MT26 Abstracts, Timetable and Presentations

22 Sept 2019, 14:00 → 27 Sept 2019, 13:00 Canada/Pacific

Hyatt Regency Hotel Vancouver

Conference Chair: Rüdiger Picker (TRIUMF), Program Chair: Michael Parizh (GE Global Research)

The detailed Technical Program can be accessed via the Timetable Views on the left.

Late submissions are no longer accepted except for the extreme circumstance of presenting last minute, ground-breaking research. In such cases, please email your abstract to mt@centennialconferences.com and be sure to include the appropriate submission category. Abstracts will be sent to the Program Committee for possible consideration at the committee’s discretion.

Anyone presenting at and/or attending the conference must be a registered participant. Registration information will be made available at the MT26 website.

If you have a presentation, you must first login via the upper right corner; then click on “My Contributions” below “Presentation(s)”.

ALL PRESENTERS must upload an electronic copy of their talk in PDF or PPT(X) format prior to their presentation at the scheduled MT26 session. By participating at MT26 and submitting your presentation, you implicitly agree to publish the content of your presentation on the public Indico site.

Presenters of oral talks must also submit their presentation file to the Speaker Preparation Room (Dover/Tennyson Room) one (1) day prior to their scheduled presentation.

Detailed presentation guidelines are available via the left side navigation of this site.

Click on the image below to download the Schedule at a Glance in PDF format.

All other conference information can be found at mt26.triumf.ca.

14_MT26_ScheduleOverview_8.27.19.pdf

15_FloorPlan.pdf

KeyFacts.pdf

Moderators_9.20.19.xlsx

MT26_CallForAbstracts.pdf

MT26_ProgramBook.pdf

Sunday 22 September

14:00 Registration Open

18:30 Welcome Reception

Monday 23 September

07:50 Registration Open (7:00 AM - 6:30 PM)

07:55 Exhibits Open (9:00 AM - 4:30 PM)

For a list of Exhibitors, please visit: https://mt26.triumf.ca/#exhibitors.

08:00 MT26 Opening

Plenary: Herman ten Kate (CERN)

Convener: Prof. Lance Cooley (ASC/NHMFL/FSU)

1 Mo-Mo-PL1-01: SUPER-Conductors for Successful Magnets

Defining what a successful SUPER-conductor for a magnet is, isn’t easy. It is often underestimated to what extend the type of magnet and its application are strongly determining the conductor requirements. Whether it is a one-off magnet where cost is not an issue, a quasi-commercial small series, or a long-term commercial production of magnets, is crucially influencing the conductor choice. The technical and economic considerations for a single high-end magnet in a satellite or for an insert in a high-field facility are very different from those for a few hundred or thousands of magnets for particle accelerators or ultimately the long-term series production of MRI magnets.
In textbooks, we find long tables with superconducting materials ever discovered, but when it comes to those for practical use in magnets, only a few remain. Yet another hurdle we encounter when attempting to use these NbTi, Nb3Sn, MgB2, BSCCO and ReBCO wires in high-current multi-strand cables and often mechanically reinforced conductors. They have to survive the enormous Lorentz force and thermal-electro-magnetic infestation present in large-scale magnets and guarantee degradation free and reliable operation for some 20 to 30 years.
The requirements for successful SUPER-conductors will be reviewed and a few striking examples, where naive initial designs had to be corrected, will be presented. Long-term research and development to learn, understand and improve not only bare transport properties of conductors but also their thermal-mechanical behavior are required for magnets to be successful.

Speaker: Herman Ten Kate (CERN)

20190923-TenKate - Plenary Oral MT26-SUPER-Conductors Magnets.pdf

08:50 IEEE Awards Presentations

09:15 Coffee Break (during Poster Sessions)

Mon-Mo-Po1.01 - Quench Protection and Detection Systems I

Conveners: Konstantinos Bouloukakis (Victoria University of Wellington), Maxim Marchevsky (LBNL)

2 Mon-Mo-Po1.01-01 [1]: Presentation withdrawn

3 Mon-Mo-Po1.01-02 [2]: Design and Evaluation of a Controllable Contact Resistance for Meter-Class REBCO No-Insulation Pancake Coils

We focusing on investigating the protection of meter-class REBCO no-insulation (NI) coils applied in next generation high-field magnetic resonance imaging scanners. In order to address the issue of controllable contact resistance, we proposed a method is based on an external variable resistance, which is paralleled with an NI coil to realize the controllable contact resistance. It can maintain the temperature increase of the coil in the safety range during a charging and discharging by the efficient leading-out the electromagnetic energy. To certify the feasibility of this method, in this study, a numerical analysis was conducted of a partial element equivalent circuit along with a thermal analysis of a simple equivalent circuit model to investigate the effective range of variable resistor to realize the protection method for the meter-class NI coil. Based on the results, we discussed the feasibility of the inhibitory effect of variable resistor on the temperature increase of meter-class NI coil and the energy dissipation rate during a sudden discharging.

Speaker: Prof. Tao Wang (Nanjing University of Science and Technology)

4 Mon-Mo-Po1.01-04 [3]: Performance of the Large Hadron Collider’s Cryogenic Bypass Diodes over the First Two Physics Runs, Future Projects and Perspectives

Cryogenic bypass diodes have been installed in all superconducting dipole magnets (1232) and all main superconducting quadrupole magnets (392) of the Large Hadron Collider (LHC) at CERN, and operated during the physics runs since 2009. The by-pass diodes are a fundamental ingredient of the quench protection system for those main dipoles and quadrupoles magnets. Diodes are located inside the magnet cryostats, operating in superfluid helium and exposed to ionizing radiation. The connection between the superconducting magnet and the bypass diode is made through a mechanically clamping system and copper bus bars. Since their first installation, all LHC diodes have undergone at least one full thermal cycle (from 1.9 K to room temperature and back to superfluid helium temperature).
The evolution of electrical parameters as well as improvements and modifications made over a period of 10 years are reviewed under a critical eye.
The maximum estimated dose accumulated for one single diode is today of the order of 500 Gy. A test setup has been developed to qualify diodes for higher neutron fluences and integrated doses than they were initially. The setup was installed at CERN in a radiation test facility and diodes irradiated at cryogenic temperatures over 2018. The qualification process has allowed to identify three candidates that could be used for the new High-Luminosity LHC circuits. This paper will also report on the behaviour and performance of the diodes that have been measured.
With CERN preparing for LHC’s High Luminosity era, the long-term strategy for cold diodes will be presented, based on the overall results and experience gathered so far.

Speaker: Giorgio D'Angelo (CERN)

Poster_MT26_LHC_Diodes.pdf

Poster_MT26_LHC_Diodes.pptx

5 Mon-Mo-Po1.01-05 [4]: Quench protection method using current of magnetically coupled secondary coil for fast current reduction of superconducting magnet

In general, superconducting magnets operate at high currents, and excessive joule heating due to high currents can damage the magnet when quench occurs. Therefore, a quench protection system that can reduce the magnet current quickly is required when the normal zone occurs in the magnet. For this reason, several quench protection methods are being developed to rapidly reduce the current. In this paper, we present a new quench protection method that rapidly reduces current in a superconducting magnet by injecting current into a magnetically coupled secondary coil. The proposed system is magnetically coupled without direct connection to the magnet and is used in conjunction with a protection method using a conventional dump resistor to help reduce the current quickly. The performance of this system was verified using a small scale high temperature superconducting test coil.

Speaker: Yojong Choi (Yonsei University, Seoul, Korea)

6 Mon-Mo-Po1.01-06 [5]: Voltage Signal rate change of Quench Detection by Real-Time Least squares for HTS Tape and Coil

The quenching of superconducting magnets is one of the key issues affecting the safe and stable operation of superconducting devices. The effect of Magnetic flux jump and electro-magnetic stress leads to local critical current drop, continuous accumulation of heat of joint resistance, failure of refrigeration equipment or other auxiliary equipment, etc. These effects may cause quenching of the superconducting magnet. When the superconducting magnet is quenching, it will cause the point of overheating. When the quenching is continued, the locali-zation will continue to heat up. Therefore, the establishment of the automatic quench protec-tion system and the correction of the quenching judgment are important for the long-term sta-ble operation of the superconducting device. In poor electromagnetic environment, quench detection based on electrometric method is easily interfered by noise and severely disrupted quench signal may cause wrong quench determination and malfunction of quench pro-tection, thereby resulting in unnecessary loss. Because of the noise cannot be completely eliminated, in order to effectively judge the quench and reduce the malfunction of the annihilation detec-tion, a real-time least squares method is proposed.
The overcurrent experiment shows that the real-time least squares method can effectively judge the point of quench.

Speaker: Jie Chen

7 Mon-Mo-Po1.01-07 [6]: Optimal Design and Performance Evaluation of Quench Protection System using Dual-capacitor Switching with Various Design Parameters for scale-up Test coil

Recently, a new quench protection system using capacitor and switches has been announced to rapidly extract energy from high temperature superconducting (HTS) magnets. When a quench occurs, the quench protection system activates four MOSFET switches in sequence, and the energy stored in the magnet is extracted through an external resistor through a capacitor. In previous studies, the system was implemented for the protection of small-scale magnets, and the feasibility of the system was experimentally verified. The experimental results show that the energy extraction of the magnet is faster than the quench protection system using a conventional dump resistor. However, since proposed system is sensitive to capacitance, inductance, and four resistors, it is necessary to optimize design variables for various magnet systems. However, since the system is sensitive to capacitance, inductance, and four resistances, it is necessary to analyze and optimize the design parameters for various magnet systems. In this paper, the effect of each design variable on the protection performance is analyzed and a method for optimal design is presented. We also evaluated the performance by applying a design optimized for the scale-up test coil.

Speaker: Yojong Choi (Yonsei University, Seoul, Korea)

8 Mon-Mo-Po1.01-08 [7]: Quench Protection of Multi-coil Low Temperature Superconducting Systems

Quench protection is critical for superconducting systems, especially those containing enough energy to damage the system during quench. We propose a new quench protection approach for multi-coil low temperature superconducting (LTS) systems that minimizes the number of protection components that must be activated during quench. In this approach, the electrically (and probably also inductively) coupled coils are electrically connected in these possible ways: all in parallel; several parallel-connected groups, with each group consisting of several series connected coils; several series-connected groups, with each group consisting of several coils in parallel. If one of the parallel-connected coils or groups quenches, current in this coil or group decreases while current in the other parallel-connected coils or groups tries to increase to keep total current flow in the circuit the same, and this tendency will be affected by the nature of the inductive coupling among the coils. If during this event the non-quenching parallel coils or groups remain superconducting (i.e., their current is below critical current and there are no mechanical or thermal events that may cause these coils to quench), then the quench is limited to only the quenched coil or group. In some cases, the equipment may continue operation after quench, although at a somewhat reduced capacity. The proposed approach is potentially more advantageous for superconducting systems that consist of many similar coils with relatively weak inductive coupling.

Speaker: Michael Parizh (GE Global Research)

Mon-Mo-Po1.01-08 - Quench protection of multi-coil LTS magnets.pdf

9 Mon-Mo-Po1.01-09 [8]: Experimental Study on the Electrical Properties of Optical Fiber Encapsulated High Temperature Superconducting Tapes

Previously, we verified the feasibility of using a Raman-based distributed temperature sensor (RmDTS) system to measure a no insulated (NI) high temperature superconducting (HTS) coil temperature variation during an overcurrent induced quench event. In addition, to reduce the temperature response time of the RmDTS, we further optimized the whole measurement system. However, the combination method between optical fibers and HTS coil in these works is immobilizing spiral optical fibers on the turn-by-turn surface of HTS coil by using epoxy which could be harmful for the structures of HTS coils. Therefore, an ideal combination structure that encapsulating optical fibers in HTS tapes along the length direction was proposed. Before winding HTS coils, the electrical properties of these optical fiber encapsulated HTS tapes (OFE-HTS tapes) should be studied in advanced. In this study, we have compare the vibration of the critical current values, resistive values at room temperature, anti-impulse current characteristics of normal HTS tapes and OFE-HTS ones. The foundational study can really promote the RmDTS application for quench detection. More detailed experimentation and comparison results will be presented and discussed in this paper.

Speaker: Z.Y. Li

Post_MT_0916(1).pdf

Post_MT_0916(1).ppt

10 Mon-Mo-Po1.01-10 [9]: A Conceptual Design of “Magnetic Dam” as a Quench Protection System Using Electromagnetically Coupled Coils for NI HTS Magnet

When a quench occurs in a high field no-insulation (NI) high temperature superconductor (HTS) magnet that consists of a stack of double-pancake (DP) coils, a large amount of current is often induced in an NI DP coil that is electromagnetically coupled with neighbor DP coils. Depending on the strength of external magnetic field, the large induced current leads to an excessive magnetic stress and occasionally damages the magnet. In this paper, we propose a new quench protection concept to reduce the amount of induced current in an NI HTS magnet. The key idea is to use resistive copper within the magnet windings in order to absorb a portion of electromagnetic energy that is initially stored in the magnet before the quench. We tentatively name these resistive coils or plates as a “magnetic dam”, as they may slow down the electromagnetic quench propagation speed among the NI DP coils, which may be beneficial to avoid the mechanical damage by the large over-current.

Acknowledgement
This work was supported by Samsung Research Funding & Incubation Center of Samsung Electronics under Project Number SRFC-IT1801-09.

Speaker: Mr Soobin An (SeoulNationalUniversity)

Mon-Mo-Po1.01-10_Magnetic_Dam_SA_20190920.pdf

11 Mon-Mo-Po1.01-11 [10]: Experimental study on quench protection of HTS magnet composed of multiple pancake-coils by use of auxiliary resistive shunt loop method

HTS coils wound with insulated wires are actually quenched, even though HTS wires have a high quench margin and can be easily damaged, if the quench protection system does not work properly, especially in the case that current density of the magnet wires is high, It should be noted that the training effects as in LTS magnets have not been observed in HTS magnets and that damaged HTS magnets cannot be reused. Therefore, protection of HTS magnets from quench damage is important for their repeated use. The most probable cause of quench damage of HTS magnet is over-heating at the highest temperature spot (hot-spot) in the magnet wire during the quench protection sequence. Therefore, to avoid damage, it is necessary to reduce heat generation in the hot-spot. In a previous work, the authors proposed a quench protection method to reduce hot-spot temperature and increase quench detection voltage to protect an HTS magnet composed of multiple pancake sub-coils from quench damages. In the method, a current of a quenching sub-pancake coil is transferred to the other sub-coils of the magnet forming auxiliary resistive shunt loop (ARSL) by resistively shorting the other sub-coils. In this work quench behaviors of the pancake sub-coils of a model magnet was investigated by simulation experiment using small scale test pancake coils wound of YBCO wire. Current patterns of the sub-pancake coils of a model magnet at a quench event were calculated for the case that ARSL method was applied. In the experiment, the same patterns of currents calculated for the model magnet were applied to the quenching test coils by a controllable current supply. Experimental results show effectiveness of the proposed method.

Acknowledgements
This work is based on results obtained from a project commissioned by the New Energy and Industrial Technology Development Organization (NEDO).

Speaker: Takuma Ichikawa (university)

Mon-Mon-Po1.01-11[10].pdf

Mon-Mon-Po1.01-11[10].pptx

12 Mon-Mo-Po1.01-12 [11]: Cenceptual Design and Performance of Quench Detection System for Super High Field Magnet Using Multi Receivers via Wireless Power Transfer Technology

The superconducting wires have been developed for high field magnet, transformers, motors and so on. The quench detection and protection system are essential for safety operations of the HTS facilities. The high voltage signal conditioner (HVSC) method is generally used for the quench detection and protection, however, especially for high voltage operation magnet such as international thermonuclear experimental reactor (ITER) magnet (56 kV, DC), it is difficult to apply to HVSC method due to the risks in terms of high voltage sparks. As well as, the power supply for HVSC should be isolated since the super high field magnet such as ITER magnets, which is supplied by 15 MA, generate about 10 T (tesla) strong magnet. To solve these problems, insulation resistance of power supply should be larger than 500 MΩ; a lower resistance can affect the common-mode voltage of the differential amplifier in the HVSC system. From these reasons, our research team, the wireless power transmitter (WPT) system has been considered as one of reasonable options to solve insulation resistance obstacles since WPT system can transfer power through any non-metallic media between antenna (Tx) and receiver (Rx) coils. Now, the one wireless power system generally supplies operating power for one differential amplifier in the HVSC. Practically, numerous differential amplifiers would be installed in the high field magnet to detect and protect magnet system. From this reason, in this study, authors described the conceptual design and fundamental performances of quench detection system for super high field magnet using wireless power technology. Especially, the thermal distribuitons of antenna and receiver will be evaluated. As well as, the number of wireless power supply including insulation resistance can be reduced by multi resonance receiver under the 100 kHz with 3kW RF generator.

Speakers: Yoon Do Chung (Suwon Science College), Yojong Choi (Yonsei University, Seoul, Korea)

13 Mon-Mo-Po1.01-13 [12]: Dynamic quench protection framework for nuclear fusion energy devices based on superconducting magnet testing

The Large-scale Superconductor Test Facility (LSTF) serves as an important part of superconducting magnet load testing for fusion research which concerns about the nuclear energy producing. During the testing process, quench protection (QP) is indispensable for protecting the load from being overheated damaged. In this paper, a compatible and flexible QP framework is put forward to meet the different QP requirements including transferring time, protection voltage, the temperature raise, current decay speed and so on. The QP framework can provide the solution of changing the power units parameter on account of specific testing superconducting magnet. Firstly, the LSTF is introduced and the QP process in the system is comprehensively analyzed by discussing the power units’ actions and circuits currents’ flowing. Then the power units of QP system are studied by elaborating the power parameters adjustments in corresponding to different loads, especially the counter-pulse capacitor unit and the fast discharge resistor system. Finally, the testing process of central solenoid coil used for the China Fusion Engineering Test Reactor is described to illustrate the operation of the QP framework.

Speaker: Kun Wang (Institute of Plasma Physics Chinese Academy of Sciences (ASIPP))

Mon-Mo-Po1.02 - Multiphysics Design and Analysis I

Conveners: Victor Bykov (Max Planck Institute for Plasma Physics, Greifswald, Germany), Walter Fietz (KIT)

14 Mon-Mo-Po1.02-01 [13]: Parametric Sensitivity Characteristics of Numerical Simulations on EMF Free Bulging of Circular Sheet Metal

Electromagnetic forming (EMF) processes of sheet metal are used to manufacture several components in modern industry. The EMF process is a highly nonlinear phenomenon and its understanding is a complex task due to the coupling of the electrical, magnetic, thermal and mechanical problems. The generated electromagnetic forces in this process are directly correlated to the resulting deformed workpiece geometry and strongly dependent on EMF system parameters as capacitance, initial capacitor energy, tool geometry, and its electrical conductivity, inductance, and mechanical properties. This study focuses on performing a parametric sensitivity analysis by numerical simulations of free bulging of circular sheet metal aiming a high and adequate force distribution from the EMF system. The numerical method solves the electromagnetic problem using an in-house script implemented in Matlab and then the mechanical problem is solved using the ABAQUS/Explicit Finite Element software. In the presented method, the EMF process is treated as fully coupled electric-magnetic and uncoupled with the mechanical problem, solving electrical circuits, identifying their parameters, and presenting calculations method for the magnetic flux density, the self and mutual inductances, and the electromagnetic force distribution regarding coil geometry to the initial time instant. The electromagnetic force calculated with Matlab is employed in a user subroutine of ABAQUS/Explicit to predict the movement of the workpiece. The research methodology involves a parametric sensitivity analysis considering the following design variables parameters of EMF devices: system capacitance, energy pulse, and tool coil geometry. Finally, conclusions and design principles for the free bulging of sheet metal by EMF are outlined.

Speaker: Prof. Evandro Paese (Departamento de Engenharia Mecânica, Universidade de Caxias Sul, Campus Universitário da Região dos Vinhedos)

poster28.pdf

15 Mon-Mo-Po1.02-02 [14]: Progress in Simulation Method of No-Insulation High Temperature Superconductor Magnets

Rare earth barium copper oxide (REBCO) coated conductor has been promising conductor for the design of high field magnets due to its high strength, high critical current and high critical field. However, high temperature superconducting (HTS) magnets are challenging to protect due to slow normal zone propagation velocity (NZPV). No-insulation (NI) winding technology has been demonstrated to produce compact, reliable, stiff and strong magnets. This technology is not devoid of its own challenges either. The charging delay due to radial bypass path in NI coil is an actively researched area. To verify that such magnets are truly self-protecting and to understand other unique behaviors of NI magnets, they are modeled using “lumped circuit model” where each “sub-coil” is modeled as a single inductor with resistances in series (quench resistance, Rq) and parallel (characteristic resistance, Rc). The results obtained using this method and lessons learned are presented in this article: (1) During fast electromagnet quench propagation of NI magnets, overcurrents (currents greater than designed operating current) are produced which can overstress the magnets. (2) Variation of Rc with temperature and magnetic field can influence the magnet voltage. (3) In asymmetric quench of nested NI magnets, the axial centering force can be large and need to be considered. (4) Screening current and its effect in field homogeneity and magnet stress is also an important challenge unique to NI magnets. Despite the challenges, the work presented here shows that it is possible to construct high field magnets using NI REBCO technology after careful consideration of these challenges and lessons learned which will be beneficial for advancing the area of HTS magnet development.

Speaker: Kabindra Bhattarai (National High Magnetic Field Laboratory)

16 Mon-Mo-Po1.02-03 [15]: Update of Joule Losses Calculation in the ITER Cold Structures during Fast Plasma Transients

As part of the design justification of the ITER magnet system and in preparation of the commissioning activities, the heat deposition on the ITER cold structures has been computed in order to generate input loads for subsequent thermo-hydraulic analyses, which are essential for the assessment of the temperature margins of the superconducting cables. The Finite Element model of a 40 degree sector of the ITER magnet system presented in [1] has been updated, including Poloidal Field (PF) coils clamps and Correction Coils (CC) supports. A new inductive plasma scenario (DINA-2017) as well as the Toroidal Field (TF) coils fast discharge have been simulated with the electromagnetic code CARIDDI. The results are in line with the old computations. In addition to these events, the effects of the voltage ripple generated on the TF coils by the power supply have been analyzed and the induced eddy currents assessed.

[1] F. Cau et al., “Joule Losses in the ITER Cold Structures During Plasma Transients”, IEEE Transactions on Applied Superconductivity, vol. 26, no. 4, Apr. 2016.

Speaker: Francesca Cau (Fusion for Energy)

MT26-poster-FCAU.pdf

MT26-poster-FCAU.pptx

17 Mon-Mo-Po1.02-04 [16]: Presentation withdrawn

18 Mon-Mo-Po1.02-05 [17]: Stress Distribution of Magnetically Controlled Reactor Core in Gaps Area under Simulated Service Conditions

In order to control and reduce the vibration of magnetically controlled reactors(MCRs) with gaps core structure, accurate stress computation should be carried out. Previously, researchers proposed a finite element model for reactors core stress calculation considering Maxwell stress theory and magnetostriction effect. Giant magnetostrictive materials are used to be filed into the gaps to reduce the electromagnetic force in iron cores between gaps. However, they did not compute MCRs core stress considering the hardness of the gap filler under service condition.
Under the MCRs service condition of AC and DC excitations, the main factors which have influence on stress distribution in gaps area include magnetostriction effect of silicon steel, electromagnetic force effect of iron cores between gaps and the hardness of the gap filler. The magnetostrictive stress and electromagnetic stress have been studied, but the influence of gaps filler hardness on the total vibration of MCRs has not been analyzed. This paper presents an electromagneto-mechanical coupled model for MCRs to analyze their stress distribution under service condition. Firstly, magnetostriction and magnetization properties for oriented electrical steel sheet along the rolling direction (RD) and the transverse direction (TD) under AC and DC excitations are tested. Then, based on the measured constitutive relations, an electromagneto-mechanical coupled model for MCRs considering electromagnetic force effect, magnetostriction effect and the hardness of inserted materials is presented and the stresses in different directions in gaps area are calculated. Finally, an MCR prototype is made and the core vibrations in gaps area under different AC and DC excitations are tested to prove the validity of the proposed model. From the calculated and experimental results, it can be seen that the vibration in the outer edge of cores is more serious than that in the center of cores.

Speaker: Long Chen (China Three Gorges University)

19 Mon-Mo-Po1.02-06 [18]: Magneto-Mechanical Analysis of A Racetrack Superconducting Magnet Using Multiscale Approach

ABSTRACT: The large range of length scales presents within superconducting magnet and its heterogeneity, a straightforward numerical simulation of a magnet, considering all details of the microstructures would cost enormous time, so incorporation of the multiscale approaches into computational models can facilitate the numerical analysis. Additionally, the superconducting magnet with high transport current and intense magnetic field are often exposed to large Lorentz forces, which lead to the unavoidable deformation in superconducting coils, the deformation will further disturb the quality of the magnetic field. In this work, the stress/strain and magnetic field of a 4T NbTi/Cu racetrack superconducting magnet were numerical analyzed, a multiscale model from the NbTi filament scale to the coil scale was developed to obtain the homogenized and the orthotropic material properties of the superconducting coil based on the representative volume element (RVE) and rule of mixture of composite methods, these material properties are employed to solve for stress/strain and magnetic field development by using three-dimensional finite element method (FEM), and taking into account the effect from magneto-mechanical coupling of superconducting coils. The study shows that the numerical predictions based on multiscale approach for the superconducting coils on the strain are in better agreement with the previous experimental data than those based on a single-scale approach, and shows the magneto-mechanical coupling behavior of the superconducting coils is remarkable especially in intense magnetic field and large transport current. The FEM based on multiscale model was demonstrated as an acceptable method to estimate the required material properties of the superconducting coils for the magneto-mechanical analysis of a superconducting magnet.
Key words: multiscale model, magneto-mechanical coupling, FEM, superconducting magnet.

Speaker: Qiang Hu (Key Laboratory of Mechanics on Western Disaster and Environment, Ministry of Education, College of Civil Engineering and Mechanic, Lanzhou University, Lanzhou, China; Institute of Modern Physics of Chinese Academy of Science, Lanzhou, China;)

MT26-poster-胡强.pdf

20 Mon-Mo-Po1.02-07 [19]: User Defined ANSYS Elements for 3D Multiphysics Modeling of Superconducting Magnets

Computational modeling of superconducting magnets allows for predicting and understanding magnet behavior. The commercial software ANSYS is a widely used finite element software for mechanical, thermal, and electromagnetic modeling of superconducting magnets. ANSYS also allows its user to create custom elements by programming the elements’ properties and its finite element matrices. These user elements can capture additional material properties and physics that current ANSYS elements do not. Once compiled, they are then compatible with all other aspects of the software, including geometry generation, meshing, solving, and post-processing. Additionally, these elements can also be used with the multiphysics solver. We have developed two 3D user elements, one thermal and one electromagnetic with circuit coupling. In addition to the basic capabilities of ANSYS, they capture quench propagation, interfilament coupling currents, current sharing, and temperature and field dependent material properties. Two-dimensional user elements have previously been developed; however, modeling superconducting magnets in 3D allows for better representation of end effects, and other non-symmetric physics. Using the ANSYS multi-field solver, these two elements are shown to simulate coupled transient electromagnetic, thermal, and circuit effects for Nb3Sn undulators and other magnets built and tested at Lawrence Berkeley National Laboratory, particularly within the MDP. The effects of quench, interfilament coupling currents, and structural eddy currents are studied and compared to magnet test data while steps towards parallelization are also explored.

Speaker: Ms Kathleen Edwards (Lawrence Berkeley National Laboratory)

Edwards_MT26_Poster_Mon-Mo-Po1.02-07 [19].pdf

21 Mon-Mo-Po1.02-08 [20]: Accurate calculation of field expansion coefficients in FEM magnetostatic simulations

FEM simulations are a standard step in the design of accelerator magnets. It is custom for accelerator applications to characterize the field quality in terms of field expansion coefficients. Expansion coefficients are usually calculated by means of a Fourier transform of the local FEM solution evaluated at points on a circle (2D) or cylinder (3D case). The accuracy of the coefficients calculated this way depends strongly on the FEM mesh configuration and simple refinement of the mesh does not always improve accuracy. The accuracy of the expansion coefficients calculation can be improved by using the data on the magnetization of elements in the magnet yoke, obtained in the solution, instead of using directly the local solution. Since currents and the yoke magnetization are the only sources of the field, with these data the field expansion coefficients can be calculated at any remote point. We derive closed forms for calculating expansion coefficients and implemented these results in the ANSYS® add-on. Results for a case study are presented, which demonstrate that expansion coefficients can be calculated with good accuracy even for a rather coarse mesh.

Speaker: Dr Vasily Marusov (GSI Helmholtzzentrum für Schwerionenforschung GmbH)

V.Marusov-Field_expansion_coefficients_in_FEM.pdf

22 Mon-Mo-Po1.02-09 [21]: HTS magnetization current simulation using ANSYS iterative algorithm method and user defined element

Kai Zhang, Sebastian Hellmann, Marco Calvi
Paul Scherrer Institut, Villigen, CH

Lucas Brouwer
Lawrence Berkeley National Laboratory, Berkeley, CA

Abstract – In this work, we will introduce the feasibility of using A-V formula in ANSYS to simulate the magnetization process of HTS bulk materials. The iterative algorithm method (IAM) based on ANSYS APDL is firstly developed to simulate the magnetization current issues in a ReBCO bulk disk based on Bean model. Specifically, we confirm it is feasible to simulate the development of trapped current density in the ReBCO bulk during the process of ramping and damping the external magnetic field. Using IAM, we can update the magnetic field-dependent critical current density for each element in the ReBCO bulk after each load step of electromagnetic analysis. It is also feasible to take the mechanical strain effects into consideration if we update the strain-related critical current density after each load step of electromagnetic-mechanical coupled analysis. Finally, a systematic study of HTS magnetization current issues is performed to test the newly developed ANSYS user defined element (UDE) in which E-J power law is defined. The flux creep effects of the ReBCO bulk during Field Cooling Magnetization (FCM) are investigated when using different n-values. The simulation results of using ANSYS IAM and UDE are compared with the simulation results of using COMSOL.

Speaker: Dr Kai Zhang (Paul Scherrer Institut)

MT-Poster-Kai-A-V-A formula.pdf

MT-Poster-Kai-A-V-A formula.pptx

23 Mon-Mo-Po1.02-10 [22]: Design and Optimization of a High-frequency Rotational Magnetizer for Nanocrystalline Alloys Based on Improved SVM and PSO Algorithms

Characterizing the magnetic properties of industrial magnetic materials has great significance on the development of transformers, motors and other electrical equipment. Recently, high-frequency and high-power density electrical equipment has attracted more attention. As the frequency is getting higher and higher, the losses of the magnetic core are much higher than that in the power frequency situation. Nanocrystalline and amorphous alloys lead to a significant reduction in the core loss which gives the opportunity to develop high-efficiency devices in high-frequency applications under frequencies from 20 Hz to 20 kHz. For better using of these materials, it is very necessary to have a deep understanding of these materials’ loss behavior under rotational magnetization condition. In this paper, a new magnetizing structure for nanocrystalline alloys rotational core loss measurement is designed and optimized by the 3D-FEM method. The optimization goal is to achieve both the best homogeneity and the highest testing frequency. As the affecting factors are very complex and the 3D-FEM calculation is very time consuming, improved SVM and PSO algorithms are combined in the optimization process. The improvement of PSO is one of the significant parts of this paper. PSO is a kind of swarm intelligence algorithm. It is simple and easy to implement. But it also has the problem of low search accuracy and is easy to fall into local extrema. In this paper, an improved PSO called the velocity-controlled PSO (VCPSO), based on the analysis of the particles’ distribution has been developed and used in the optimization process. As the 3D FEM calculation is very complex, support vector machine (SVM) is used to establish a regression model between the designed parameters of the RSST during the optimizing process. The results well detailed discussed in the full paper.

Speaker: Dr Long Chen (China Three Gorges University)

Mon-Mo-Po1.03 - High Field Magnets for Accelerators

Conveners: Karie Badgley (Fermilab), Peter McIntyre (Texas A&M University)

24 Mon-Mo-Po1.03-02 [23]: Fracture Failure Analysis for MQXFA Magnet Aluminum Shell

The High-Luminosity LHC Accelerator Upgrade Project (HL-LHC AUP) is approaching the production phase of the US-contributed Q1 and Q3 Interaction Region Quadrupoles (MQXFA). The structures for the MQXFA prototypes were design and inspected by the US-LARP (LHC Accelerator Research Program), AUP developed criteria, which will be used for the pre-series structures. As the first two full-length prototypes with 4.2 m magnetic length, MQXFAP1 and MQXFAP2, were designed and assembled at Lawrence Berkeley National Laboratory (LBNL), and tested at Brookhaven National Laboratory (BNL). The end aluminum short shell of MQXFAP2 was fractured along the shell length during the test, and tests were stopped. Analytical and Finite Element analysis were performed in light of the graded procedure defined in the Structure Design Criteria to investigate the fracture failure for MQXFAP2.
In this paper, we report the fracture analysis of the current shell design, including the elasto-plastic simulations with sub-model technique, crack propagation simulations, and calculations with Linear Elastic Fracture Mechanics (LEFM). Test material properties are also presented. The results of this analysis explain why the end shell of MQXFAP2 failed, and suggest fillets on the end shell notches to meet the margin specified in the Structural Design Criteria.

Speaker: Heng Pan (LBNL)

Poster_V3.pdf

25 Mon-Mo-Po1.03-03 [24]: Performance update of 2-m-long 11 T Nb3Sn dipole magnet models for HL-LHC

In the frame of the HL-LHC upgrade, assemblies of two 5.5 m long 11 T Nb3Sn dipoles (MBH) are expected to replace 8.3 T NbTi LHC main dipoles (MB). Double and single aperture models, each 2 m long, were built and cold tested in operational conditions. The models have design features that are verified during these tests to provide feedback for the technology development of 5.5 m full-size magnets. With the last model magnets tested, using the final conductor, conductor insulation and assembly processes, the performance is evaluated and the readiness for series production is confirmed. In this paper, the test results of the latest model magnets in terms of training behaviour and memory, conductor limits, endurance, quench protection and other cold powering tests are presented. Additionally the results of cold endurance tests, thermal cycles and powering cycles, are discussed in view of the operational requirements in the LHC.

Speaker: Gerard Willering (CERN)

2019-09-23-Mon-Mo-Po1 03-03 - Performance update of 2-m-long 11 T Nb3Sn dipole magnet models for HL-LHC.pdf

26 Mon-Mo-Po1.03-04 [25]: Analysis of quench in the HL-LHC 11 T dipole model magnets with 1-D and 2-D models

The HL-LHC Project at CERN requires the installation of 11 T Nb3Sn dipole magnets to upgrade the collimation system. Given the high operating field and current density, the quench protection of these magnets is particularly challenging. The baseline protection scheme of the 11 T dipoles is based on the quench heaters technique.
Dedicated quench tests were carried out at CERN on short samples of the 11 T dipole magnets, in which the quench heaters were fired either individually or simultaneously. The aim of these tests was to measure the quench energy and quench location in the coils, in response to heat depositions of different amplitude. The tests were carried out at transport currents in the range from 11.85 and 12.85 kA; the applied heat flux densities were increased stepwise between 5.9 and 12 W/m until a quench was detected.
Two different modeling approaches were developed to analyze the test results. The first model is based on a simplified 1-D representation of the magnet components along a line crossing radially the middle plane of one quadrant of the magnet cross section. To improve the description of heat exchange with superfluid helium, this model was also applied to analyze dedicated tests carried out in the cryogenic facility of CERN.
The second model represents in detail all magnet components in the 2-D cross section of one dipole quadrant. The model allows one to identify the parts of the magnet which are more thermally solicited in the quench tests, and therefore the most probable quench initiation locations.
The paper presents a detailed description of the models, their validation by comparison with the experimental results, and their application to analyze the details of the quench propagation in the magnet cross section.

Speaker: Marco Breschi (University of Bologna)

27 Mon-Mo-Po1.03-05 [26]: Geometrical Inspection and Analysis of the Impregnated Nb3Sn 11 T Coils

In the CERN Large Magnet Facility (LMF), the series production of the Nb3Sn-based 11 T dipole magnets is currently ongoing. Results from magnet tests and observations regarding the conductor irreversible stress limitations have shown that a uniform and well-defined pre-load is crucial. The collaring force in the assembly is adjusted by the thickness of a longitudinal shim derived from the measured coil’s azimuthal excess. One of the key features to define the collaring force is given by the control of the coil dimensions. The results from two measurement setups are presented using Coordinate Measurement Machines (CMM) featuring ±34 μm and ±5 μm accuracy. The analysis accuracy is modelled taking into account the 11 T coil branch geometry and measurement setup characteristics.

Speaker: Friedrich Lackner (CERN)

28 Mon-Mo-Po1.03-07 [27]: Analysis of the heater-to-coil insulation in MQXF coils.

In the framework of the HiLumi project, the present LHC low-β superconducting quadrupoles will be substituted with more performing ones, named MQXF. MQXF will have high peak-field on the conductor (~12 T), therefore the Nb3Sn technology is needed in order to reach the target performance.
One of the main technological challenges for the Nb3Sn magnets is the coil fabrication: due to the brittleness of Nb3Sn, coils needs to be impregnated with epoxy resin in order to improve mechanical properties, and avoid conductor damaging. Quench heaters are necessary for quench protection, and they need to be impregnated with the coil as well, in order to be close enough to the coil itself and to reach the required efficiency. Quench heaters are insulated from the coil by a 145 μm layer S 2 Glass® and Epoxy resin, and a 50 μm layer of Kapton®.
The test of the first MQXF prototype (4 m long) has been interrupted due to a heater-to-coil short circuit. Therefore, the electrical testing procedures have been improved, and a deep analysis of the heater-to-coil insulation has been performed.
In this paper, we report the results of the heater-to-coil insulation analysis, showing the simulations of the peak voltages expected in the magnet, modelling of the insulation during quench and electrical test conditions, including failure analysis, and the experiments performed on coil sections, short coils and models, long coils and prototypes made in order to prove the robustness of the insulation. Alternatives to the present fabrication solution are also presented, showing advantages and disadvantages. The results of this analysis are of general interest for all the Nb3Sn coils impregnated together with quench heaters.

Speaker: Vittorio Marinozzi (FNAL)

MT26_posterVM.pdf

29 Mon-Mo-Po1.03-08 [28]: Vacuum impregnation of long Nb3Sn coils for the HL-LHC project

The CERN Large Magnet Facility (LMF) is currently producing 5.5 m long 11 T dipole and 7.2 m long MQXFB quadrupole coils for the HL-LHC project. Both coil types are fabricated with Nb3Sn conductor and therefore produced based on the so-called wind and react process. These coils require a vacuum impregnation process to form the final electrical insulation.
The paper will present the impregnation process applied at CERN, together with the one used in the US for the MQXFA coils, within the Accelerator Upgrade Program (AUP) framework. The impregnation process and its reproducibility are shown, ongoing developments to further improve quality control are proposed. Furthermore, the LMF impregnation infrastructure and recent applied upgrades are described, aiming for a reliable process workflow based on a modular hardware with an improved interchangeability.

Speaker: Mr Jerome Axensalva (CERN)

Poster_Mon_Mo_Po1.03-08_J_Axensalva.pdf

30 Mon-Mo-Po1.03-09 [29]: Characterization of NbTi busbar for HL LHC Interaction Region Quadrupoles

The United States High Luminosity Large Hadron Collider Accelerator Upgrade Project (US-HL-LHC AUP) is designing and fabricating 11 Q1/Q3 cold masses for the interaction regions of the LHC. Each cold mass contains two 4.2 m quadrupole magnets. The Nb3Sn quadrupole magnets operate in superfluid He at 1.9 K with a nominal field gradient of 132.6 T/m. The design and fabrication of the through and local buses for the cold masses is carried out at Applied Physics and Superconducting Technology Division at Fermilab (FNAL). The bus-bars consist of two superconductive NbTi cables soldered together and wrapped in Kapton.
This paper reports the characterization of the bus-bar thermo-electric properties to validate the bus design and assure quench protection. Calculations have been performed to estimate the quench integral, the quench propagation velocity and the maximum voltage developed in the bus. The bus design was validated testing the cable together with a short Nb3Sn magnet in the vertical test facility of Applied Physics and Superconducting Technology Division at FNAL.
The test demonstrated that the bus design is sound; no spontaneous quench took place up to 17870 A current value. Temperature margins were measured to be higher than the required 5 K for the High-Luminosity Q1/Q3 triplet bus at nominal operating current. Protection studies revealed that the bus can be adequately protected using 100 mV voltage threshold value for the entire current range the magnet will operate in the LHC tunnel. Results of quench propagation velocity and quench integral measurements as a function of temperature and current are also presented in this paper.

Speaker: Maria Baldini (Fermi national accellerator laboratory)

PosterMT26.pptx

31 Mon-Mo-Po1.03-10 [30]: Design of a Compact Support Structure for a High Gradient Niobium Tin Superconducting Magnet for a Proposed Electron Ion Collider (EIC).

Abstract— A future Electron Ion Collider (EIC) may require high gradient superconducting quadrupole magnets for final focusing of the hadron beam in the interaction region. Due to the closeness to the beam collision point and the narrow 25mr crossing angle these high gradient magnets will reside in close proximity to electron beam magnets, thereby requiring a very compact support structure in comparison with typical accelerator magnet support structures, for the high Lorentz forces that are generated with excitation. This paper reports on the design of a proof of principle support structure for a 132 T/m, 120mm aperture superconducting magnet, utilizing the (HQ) coil design developed for the LHC Accelerator Research Program (LARP). In addition to the design work a 15cm long mechanical model based on the design is being built and loaded to the required level of coil precompression at room temperature, and then cooled to 77K to also confirm the level of coil precompression at cryogenic conditions. Future work will include construction and testing of a proof of principle magnet based on the design in an accelerated time frame, utilizing previously tested LARP HQ coils.

Index Terms—EIC, LARP, Hi-Lumi, LHC, Nb3Sn, superconducting magnets

Speaker: Ms Kathleen Amm (BNL)

32 Mon-Mo-Po1.03-11 [31]: Test of a single Nb3Sn sextupole coil for ECR ion source using a mirror structure

IMP is developing a Nb3Sn superconducting magnet system for a 45 GHz electron cyclotron resonance (ECR) ion source. To achieve this complicated and difficult Nb3Sn magnet, a prototype with identical cross section but half length of the magnet is proposed. Recently a single sextupole coil about 0.5 m long has been fabricated and tested. The coil has a bore size of 200 mm and was wound by using a Nb3Sn wire with 1.3 mm diameter. In order to test the coil efficiently, a mirror structure is utilized. And the Bladder & key technology is employed to exert the required preload on the coil. This paper describes the magnetic field design of the sextupole mirror structure, presents the fabrication of the sextupole coil and reports the test results.

Speaker: Dr Wei Wu

33 Mon-Mo-Po1.03-12 [32]: Final focus superconducting magnets for CEPC

Circular Electron Positron Collider (CEPC) with a circumference about 100 km, a beam energy up to 120 GeV is proposed to be constructed in China. Most magnets for CEPC accelerator are conventional magnets, except some superconducting magnets are required in the interaction region of CEPC collider ring. High gradient final focus doublet quadrupoles QD0 and QF1 are required on both sides of the collision points in the interaction region of CEPC collider ring to achieve high luminosity. QD0 and QF1 are both double aperture superconducting quadrupoles with a central field gradient of 136 T/m and 110 T/m, respectively. The field crosstalk between the two apertures in the quadrupoles should be solved. Since the final focus superconducting quadrupoles are operated inside the field of the Detector solenoid magnet with a central field of 3.0 T, strong superconducting anti-solenoid is need to cancel the Detector solenoid field and minimize the effect of the solenoid field on the beam. In this paper, the layout and magnetic design of CEPC final focus superconducting magnets are described, and the R&D status of prototypes superconducting magnets is presented.

Speaker: Dr Yingshun Zhu (Institute of High Energy Physics, Chinese Academy of Sciences)

2019-9-21 MT26 Final focus superconducting magnets for CEPC.pdf

34 Mon-Mo-Po1.03-14 [33]: A High Precision Magnetic Field Shimming algorithm for Inclined 45° Continuous Cutting on Spiral Pole of SC Cyclotron

Due to the small size and low power consumption, compact superconducting cyclotron are suitable to be installed in hospital for cancer therapy, which becomes a research hotspot in recent years. China Institute of Atomic Energy has been developing a 230MeV compact superconducting cyclotron CYCIAE-230 to meet the demands of proton therapy in China. Accelerator physics design requires a strict control of the average field error and first harmonic in the main field. A processing method of inclined 45o continous cutting on the two pole edges is proposed to shim the field in CYCIAE-230. For a spiral sector magnet, the 45o continous cutting generates an asymmetrical magnetic field on both sides, and the field change is not proportional to the milling depth, which makes the establishment of the shimming algorithm much more complicated. In this paper, a Mathematica model of the linear equation for field shimming calculation is established. The field change caused by the local cutting is calculated numerically by the integral equation method to describe the nonlinear relation of the complex shape cutted parts. And then the shimming process is built with multi-iterative simulation based on the least squares method. The finite element model is built to confirm the field change brought by the inclined 45o cutting value, which is added to the iterative calculation for cutting value correction and expecting the shimming effect. The new shimming algorithm is applied for the field measurement, amending and processing of CYCIAE-230, which achieve significant results to reduce the shimming times and further the fabrication period. The process of the shimming algorithm and the corresponding shimming effect of CYCIAE-230 will be presented as well.

Speaker: Dr Ming Li (China Institute of Atomic Energy)

A High Precision Magnetic Field Shimming algorithm for Inclined 45° Continuous Cutting on Spiral Pole of SC Cyclotron.pdf

35 Mon-Mo-Po1.03-15 [34]: Magnetic Field Measurement, Amending and Processing for 230MeV Superconducting Cyclotron Main Magnet

A 230 MeV superconducting cyclotron CYCIAE-230 is being constructed by the China Institute of Atomic Energy. The technology of magnetic field measurement and amending processing is the primary task to realize the isochronous acceleration of cyclotron. The CYCIAE-230 has higher magnetic field, higher field gradient and dense rotation orbits. Therefore, the isochronous field and resonance crossing amended simultaneously. The first harmonics is also shimmed at the same process to achieve about 80% of the extraction efficiency by using resonance and precession extraction. The precision of field measurement, amending and processing is much higher and the algorithm is much more difficult. In addition, the compact structure of the magnet has very narrow installation space, which makes mapper design more difficult. In this paper, we will introduce:
1.The asymmetric field amending method for spiral sectors of SC cyclotron based on 45 degree chamfering on the pole edge is proposed and implemented for the first time. This method can effectively shim the isochronous field and first harmonics, reduce the magnetic saturation surround the pole edge, and facilitate the installation of main components such as central region and RF cavity.
2.During the processing, the asymmetric amending on both sides of the spiral sectors is creatively introduced to adjust the local tune value, so as to avoid the beam staying near harmful resonance and realize the effective control of the beam quality in the cyclotron.
3.A automated magnetic field measurement device, with both searching coil and hall probe has been developed. A series of optimum design and implementation of mechanical parts and EMC have effectively improved the positioning accuracy, greatly reduced the interference signal, and achieved the relative field measurement accuracy of 5×10-5.
After four times of field measurements, amending and processing, the results show that the phase shift, tune value and first harmonics have achieved excellent results. Detailed process will also be given in this paper. Such results will benefit greatly the overall performance of CYCIAE-230.

Speaker: Prof. Tianjue Zhang (China Institute of Atomic Energy)

Magnetic Field Measurement, Amending and Processing for 230MeV Superconducting Cyclotron Main Magnet.pdf

36 Mon-Mo-Po1.03-16 [35]: Preliminary Study of the High Temperature Superconducting Solution for 2GeV CW FFAG Magnet

Proton beam with an average power of 5MW-10MW have important applications in particle physics towards the intensity frontier, as well as in the advanced energy, and material science. The fixed field alternating gradient (FFAG) accelerator combines the advantages of existing accelerators, which has a higher limitation of beam energy than high power cyclotron and has a higher beam-to-grid efficiency than existing high power linac and synchrotron, thus is considered as a good candidate for high power proton machine.
By utilizing the strong focusing and large acceptance features of FFAG in the theoretical framework of the fixed field and fixed frequency of isochronous cyclotron, a 2GeV/6MW continue wave FFAG design has been proposed in China Institute of Atomic Energy (CIAE). Due to the beam loss of high power proton beams, the resulting high radiation will deposit a large amount of radiation dose and head load on the SC magnet. As the high temperature superconductors (HTS) have a much larger thermal margin due to high critical temperature (> 90 K) and high upper critical field (> 100 T) than the traditional low temperature superconductors, and have been also considered have the lower overall construction costs and power consumption than the conventional magnet, currently the HTS magnet is the favorable solution for the 2GeV FFAG magnet design. In this paper, the lattice design along with the requirements on the F-D-F magnet of the 2GeV FFAG design is briefly introduced first. Then, the design of the F-D-F magnet is outlined. And the details of the HTS coil design utilizing ReBCO conductor and operating at ~40 K is also included.

Speakers: Dr Ming Li (China Institute of Atomic Energy), Tianjue Zhang (China Institute of Atomic Energy)

Preliminary Study of the High Temperature Superconducting Solution for 2GeV CW FFAG Magnet.pdf

Mon-Mo-Po1.04 - High Field Magnets for Future Colliders

Conveners: Friedrich Lackner (CERN), Qingjin XU (IHEP, CAS)

37 Mon-Mo-Po1.04-02 [36]: 3D mechanical Analysis of the Block-coil Dipole option for the future Circular Collider

This paper presents a 3D mechanical analysis study of the mechanical behaviour of the complete magnet structure of the Block-coil Dipole option for the future Circular Collider. The analysis includes three steps: (i) pre-loading with bladders and keys, (ii) cooling down from room to operating temperature, (iii) ener-gization at operating temperature. The main objective of the 3D optimization is to contain the large elec-tromagnetic forces, both in the straight section and in the coil ends. The optimization must guarantee that the stress level in the coil and in each component of the structure remains lower than the allowable values at each loading step. The magnet design in the straight section has been optimized and validated previous-ly using a 2D model. A 3D model is then required to optimize the coil ends and the longitudinal sup-port.This study was performed in the framework of the EuroCircol project.

Speaker: Mr Chhon Pes (CEA)

38 Mon-Mo-Po1.04-03 [37]: Engineering Design and Digital Twin of the Nb3Sn 16T main dipole magnet of the FCC accelerator

Superconducting accelerator dipole magnets, based on Nb3Sn technology, with a nominal operation field of 16 T in a 50 mm aperture are being considered for the Future Circular Collider (FCC) with a center-of-mass energy of 100 TeV and a circumference in the range of 100 km, or an energy upgrade of the LHC (HE-LHC) to 27 TeV. To demonstrate the feasibility of such magnets, a twin-aperture 16T Nb3Sn dipole demonstrator based on a 4-layer cos-theta coil with 50 mm aperture and cold iron yoke is developed in the frame of the EuroCirCol program. The main design challenges for 16 T magnets include large Lorentz forces at this field level while maintaining accelerator requirements. To counteract the electromagnetic forces, an innovative mechanical structure based on the bladder-and-key concept, incorporating asymmetric coils and both aluminum and stainless steel skins, has been developed at INFN and further studied in collaboration with the University of Patras. This paper describes the design concept of the 16 T twin-aperture dipole magnet and the fully 2D & 3D parametric multi-physics finite & boundary element model (FEM & BEM), including the end regions. The design optimization is described and the optimized assembly parameters are presented.
*Work is supported by CERN, under contract No. FCC-GOV-CC-0141.

Speaker: Mr Charilaos Kokkinos (FEAC Engineering P.C. & University of Patras)

39 Mon-Mo-Po1.04-04 [38]: Electromagnetic and mechanical study for the Nb3Sn bending dipole short model for FCC

The Italian Institute for Nuclear Physics (INFN), in collaboration with CERN, is going to build the short model in Nb3Sn of the main bending dipole for the Future Circular Collider (FCC). The magnet will be developed on the basis of the baseline design presented in the FCC Conceptual Design Report (CDR) in the end of 2018. The magnet is based on cosine-theta design, with an internal aperture diameter of 50 mm and a “Bladder & Key” configuration for the mechanics.
The main purpose of the model construction is to demonstrate the feasibility of a magnet dipole with field quality characteristic suitable for collider and magnetic field above the LHC frontier.
The mechanical structure, which is a critical aspect of the magnet design, especially for the brittleness of the Nb3Sn cables, will have to demonstrate the effectiveness to reach the highest performance achievable in terms of bore magnetic field.
Here we present both the electromagnetic and mechanical design study of the model.

Speaker: Riccardo Umberto Valente (LASA-INFN (Milano, Italy))

Mon-Mo-Po1.04-04 [38].pdf

40 Mon-Mo-Po1.04-05 [39]: Quench protection study for F2D2, the Flared-end Block Dipole Demonstrator for the Future Circular Collider

The forecast hadronic synchrotron studied in the FCC-hh program aims to reach 100 TeV center-of-mass collision energy using 16 T bending dipole magnets along a 100 km long ring. Gaining such magnetic field occupying a reasonable volume requires new technologies to be tested and validated on demonstrators. In collaboration with CERN, CEA is developing F2D2, the FCC Flared-end Dipole Demonstrator based on the block-coil option proposed in the EuroCirCol study. This single aperture 1.4 m long magnet is designed to reach at least 15 T with 14% margin at 1.9 K using two different Nb3Sn cables. The energy density per unit length is 1.4 MJ/m, about 3 times the energy density per unit length of the LHC dipoles. The combination of the high energy density and the graded coils makes the quench protection of this magnet one of the most challenging. A study considering the state-of-the-art of active quench protection technologies such as heaters and CLIQ is here presented, completed with multi-physics models to accurately describe the quench evolution, the hotspot temperature and the voltages between and at the end of the coils.

Speaker: Dr Valerio Calvelli (CEA)

41 Mon-Mo-Po1.04-06 [40]: Presentation withdrawn

42 Mon-Mo-Po1.04-08 [41]: Investigations into the preliminary Future Circular collider 16 Tesla dipole cryostat design.

As part of an international collaboration, CERN has recently published a Conceptual Design Review of the Future Circular Collider (FCC), a proposed particle accelerator to succeed the LHC. Under the options considered, a proto-proton accelerator with collision energies up to 100 TeV, would require approximately 4’500 Nb3Sn superconducting dipole magnets operating at 16 T fields, installed in a new tunnel of about 100 km circumference. A proposed variant, as a possible first step towards the FCC, is the incorporation of these magnets in the existing LHC tunnel infrastructure. This will provide a proton-proton collider with about twice the collision energy of the LHC, the so-called High Energy LHC (HE-LHC). The 16 T dipoles, which are considerably larger and heavier than the 8.33 T LHC dipoles, require compact cryostats to keep the overall dimensions comparable with the size of the LHC tunnel.
In this paper, we report on the design and integration work on the baseline 16T cosine-theta design dipole magnets within their cryostats. We present here, possible design options departing from the well-established solution of the LHC cryostats, including mechanical and thermal design considerations on the cryostat. We also explore the electromagnetic and mechanical coupling between the magnet and the vacuum vessel, in the case of a stray field in the cryostat space, as would be required to reduce the volume of the cold mass.

Speaker: Zoe Marie Townsend (CERN)

43 Mon-Mo-Po1.04-10 [42]: Design of an 18 T arc dipole for an LHC energy doubler

We report the design for a hybrid block-coil dipole using advanced cable-in-conduit windings. The dipole is designed for use in the arcs of an energy-doubling lattice in the LHC tunnel.
The block coil design facilitates configuration of hybrid sub-windings of Bi-2212, Nb3Sn, and NbTi, each operating to the same fraction of critical current.
The cryogenics utilizes supercritical helium, operating in the window 4.5-5.5 K.
A novel method is provided for the support structure that provides robust support and stress management, and provides for the three sub-windings to be separately wound and heat-treated and then assembled and preloaded to complete the dipole.

Speaker: Peter McIntyre (Texas A&M University)

Mon-Mo-Po1.04-10 [42].pdf

44 Mon-Mo-Po1.04-11 [43]: Presentation withdrawn

45 Mon-Mo-Po1.04-12 [44]: Mechanical behavior of a dipolar support structure for sextupole-in-solenoid Magnet during assembly, cool-down and warm-up processes

Aiming to develop a combined superconducting magnet for a fourth-generation ECR source operating at 45 GHz at the Institute of Modern Physics (IMP) in Lanzhou of China, a significant gain in performance can be achieved by using Nb3Sn to allow solenoids and sextupole coils to reach a high field of 12 T. In consideration of special design of the sextupole-in-solenoid shape, the supporting structures with pre-tensioned aluminum cylinders named Bladder are used to bear the large loading and maintain the configuration during the magnet assembly and operation in cryogenic and electromagnetic environment. A dipolar structure based on an aluminum shell and home-made bladders were designed in this work. The mechanical characteristics of the dipolar support structure were explored numerically and experimentally. A 3D finite element modeling was developed to analyze the deformation and stresses in the structures during its assembly, cool-down and warm-up for simulating the practical operation conditions. The measurements on the strains profiles in the aluminum shell in the dipolar support structure also has been conducted using low-temperature resistance strain gauges combined with a half-bridge compensation method for temperature. Our results show that the pre-stresses induced in the support structures during the two stages of gas loading in the bladder and shrinkage during cool-down process reach the level for efficiently hustling the 12T superconducting ECR magnet. The numerical analysis is in good agreement with the measurements. Additionally, the mechanical behavior of the bladders during gas loading and cool-down is obviously dependent with the friction property between contact surfaces, which gives the main concerns in the design and optimization such special support structures under cryogenic environment.
Key words: Superconducting magnet, dipolar support structure, bladder, cryogenic environment, mechanical analysis

Speaker: Beimin Wu (1 Key Laboratory of Mechanics on Western Disaster and Environment, College of Civil Engineering and Mechanics, Lanzhou University, China; 2 Institute of Modern Physics of Chinese Academy of Science, China)

Mon-Mo-Po1.04-12 [44]-Beimin Wu.pdf

46 Mon-Mo-Po1.04-13 [45]: Fabrication and High-field Performance of the First Iron-Based Superconductor Racetrack Coil

The first 100-m iron-based superconductor (IBS) tape was produced by Institute of Electrical Engineering, Chinese Academy of Sciences (IEE-CAS) using the powder-in-tube technique in 2016. Since then, the development of IBS tape provides an opportunity to propel the practical IBS application. In this study, the world first IBS racetrack coil was made using a 100-m 7-filamentary Ba1-xKxFe2As2 (Ba122) tape at the Institute of High Energy Physics, Chinese Academy of Sciences (IHEP-CAS). The IBS tape was winded in parallel with stainless steel tape before heat reaction and impregnated with epoxy resin after reaction. The performance of the IBS coil was tested at 4.2 K and 0 - 7.5 T background field provided by an Nb3Sn Common-Coil dipole magnet named LPF1.2. The racetrack coil quenched at 7.5 T with operating current of 45.9 A, which is about 64% of the quench current at self-field. And the quench was caused by heat from one joint. The details of fabrication process and performance test results were presented in this paper.

Speaker: Dr Zhan Zhang (IHEP, Chinese Academy of Sciences (CAS) )

(Poster) Fabrication and High-field Performance of the First Iron-Based Superconductor Racetrack Coil.pdf

(Poster) Fabrication and High-field Performance of the First Iron-Based Superconductor Racetrack Coil.pptx

47 Mon-Mo-Po1.04-14 [46]: Mechanical Design, Assembly and Strain Measurement Results of LPF2: a 12-T Hybrid Common-coil Dipole Magnet

The Institute of High Energy Physics (IHEP, China) has been engaged in the development of shell-based dipole magnet with common-coil configuration for the pre-study of Super proton-proton Collider (SppC) project. The first subscale magnet LPF1, with two Nb3Sn coils and four NbTi coils, reached a bore field of 10.2 T at 4.2 K. Then a higher safety margin model has been proposed as LPF2, which has six Nb3Sn coils and two NbTi coils to reach a 12-T main field in both apertures with an operating current of 5300 A. The shell and yoke are reused from LPF1, as well as the two Nb3Sn coils and two inner NbTi coils of LPF1. The pre-loaded method of LPF2 is much alike that in LPF1: using Bladder & Key technology to overcome the Lorenz force in horizontal and vertical direction and pre-tightening six aluminum rod to pre-load the coil packs in the axial direction. While, the strain gauges are applied both at the surface of the aluminum shell and the inner surface of the innermost coils to monitor the pre-loading effect. The main design parameters, stress analysis, assembly procedure and strain measurement results during the assembly and test at 4.2 K will be presented.

Speaker: Yingzhe Wang (IHEP, CAS)

2019-09-23MT26-POSTER-zhe-final.pdf

48 Mon-Mo-Po1.04-15 [47]: Mechanical analysis and measurements of MQXFS6, the fifth short model of the Nb3Sn Low-β Quadrupole for the Hi-Lumi LHC

MQXF is the Nb3Sn Low-β Quadrupole magnet that the HL-LHC project is planning to install in the LHC interaction regions in 2026 to increase the LHC integrated luminosity by about a factor of ten. The magnet will be fabricated in two different lengths: 4.2 m for MQXFA, built in the US by the Accelerator Upgrade Project (AUP), and 7.15 m for MQXFB, fabricated by CERN. In order to qualify the magnet design and characterize its performance with different conductors, cable geometries and pre-load configuration, five short model magnets, called MQXFS, were fabricated, assembled and tested. The last model, MQXFS6, used a new PIT superconductor, featuring a bundle barrier surrounding the filaments. The coil and the support structure were equipped with strain gauges and optical fibers to monitor strain during assembly, cool-down and excitation. We describe in this paper the mechanical performance of MQXFS6, analysed through experimental data and numerical models, and we compare it with the one of the previous short model magnets.

Speaker: Giorgio Vallone (LBNL)

EelisTakala-MT26-Poster-revised.pdf

Mon-Mo-Po1.05 - Fusion I: CFETR & JT-60

Convener: Jinxing Zheng (Institute of Plasma Physics, Chinese Academy of Sciences)

49 Mon-Mo-Po1.05-01 [54]: Safety Research of the 100 kA HTS Current Lead for CFETR

Abstract: Based on the Agreement of Institute of Plasma Physics Chinese Academy of Sciences (ASIPP) and Ministry of Science and Technology of China during the Thirteen Five-Years Plan (so called 13∙5 plan), A dedicated test complex of superconducting magnet for China Fusion Engineering Test Reactor (CFETR) will be constructed in Hefei, China. A pair of high temperature superconducting (HTS) current leads rated at 100 kA for the CFETR magnet test complex is being designed at ASIPP. Because magnetic energy stored in the toroidal field magnet is 134 Giga Joules which are 3 times higher than the ITER case, HTS current leads must work in high voltage and nominal current without performance degradation during the magnet quench. In order to verify the safety and reliability of HTS current lead, this paper will numerically simulate the time of loss of flow accident (LOFA) from 50 K helium stoppage to the current sharing temperature starting and the burnout time from the current sharing temperature starting to the hotspot temperature of 200 K or the max. voltage of 100 mV along HTS module. The load line of static magnetic field is presented to predict the maximum current carrying capacity of HTS module. The inhomogeneous current distribution as a function of magnetic field with/without external applied field of 30 mT for the 90 HTS stacks is calculated by ANSYS iteration to estimate the current margin. The analysis results indicate the LOFA time is more than 500 s and the full current burnout time of 30 s is better than the requirement of the toroidal field magnet fast discharge time constant of 20 s, the HTS module heat load is less than 15W.
Index Terms—HTS, Current lead, Safety, CFETR
Acknowledgment: This work was supported by the Research of CFETR Integration Engineering Design Project (Grant No. 2017YFE0300500).

Speaker: Dr Kaizhong Ding (Institute of plasma physics, Chinese academy of sciences)

50 Mon-Mo-Po1.05-02 [55]: CFETR Central Solenoid Magnet System Structural Analysis

Engineering design of China Fusion Engineering Test Reactor (CFETR) Central Solenoid (CS) coil had been started in Institute of Plasma Physics, Chinese Academy of Sciences. The highest field of CS coil is 17.2T when the running current is 60KA. CS magnet system mainly consists of 8 Nb3Sn coils compressed with 8 sets of preload structure. The functions of the preload structure are to apply an enough axial compression to the CS coils and to have a mechanical rigidity against the repulsive force between 8 Nb3Sn coils. This paper describes structural design of CFETR CS magnet system. A global finite element model was created based on the design geometry data to investigate the mechanical property of CFETR CS preload structure and support structure under the different operating conditions. A local finite element model based on structure design was created to calculate the stress on the conductor jacket and turn insulation.
Key words: CFETR, Central Solenoid, structural design, FEA, Magnet

Speaker: Aihua Xu (institute of plasma physics Chinese academy of sciences)

CFETR Central Solenoid Magnet System Structural Analysis.pdf

51 Mon-Mo-Po1.05-03 [56]: Fabrication Status of CFETR Central Solenoid Model Coil

The Central Solenoid Model Coil (CSMC) project of CFETR that began in 2014 is devoted to develop and verify the manufacturing and testing technology of the large-scale superconducting magnet. The main manufacturing processes for the coil are verified by the mockup coil’s fabrication. For now, the winding for the Nb3Sn inner and outer coils are finished and preparing for its heat treatment, and the vacuum pressure impregnation for the NbTi middle coil is being done. This paper introduces the main manufacturing progress of the CFETR CSMC.

Speaker: Houxiang HAN

Mon-Mo-Po1.05-03 [56]：Manufacturing Status of CFETR Central Solenoid Model Coil.pdf

52 Mon-Mo-Po1.05-04 [57]: The application of TSTC based on ReBCO tapes in CFETR CS magnet design

In order to further study fusion, China National Integration Design Group designed and developed a new superconducting magnet tokamak device, China Fusion Engineering Test Reactor (CFETR). As one of the most important components of the CFETR, the CS coil will be constructed to create, form and maintain a stable operation of the plasma. The latest CFETR CS magnet system design requirements are as follows：
1) To produce a 12-T peak field in the core of the magnet.
2) The maximum magnetic field on the NbTi module is lower than 6 T.
3) The maximum magnetic field change rate is 1.5 T/s, and the operating current is 47.65 kA.
4) The unit length of one Nb3Sn conductor is shorter than 1 km.
These requirements will bring a series of problems and challenges such as stability margin and mechanical safety to the design work of CS magnets. In recent years, with the development of HTS wires (especially ReBCO tapes), HTS has become an important choice for designing CS magnets in the future. Among the HTS wires, only Bi2212, Bi2223 and ReBCO are considered suitable for large-scale applications. Compared to the former two, ReBCO tapes not only has higher current transfer capability, but also No complicated heat treatment process is required after the strip is wound. Therefore, ReBCO will be one of the important alternatives for the design of CS magnet for fusion device in the future.
In this paper, we first calculate the equivalent material properties of the TSTC based on ReBCO. Then, according to the latest CFETR CS magnet design requirements, a hybrid CS magnet model based on ReBCO, Nb3Sn and NbTi was designed and analyzed. The results will provide reference for the design of high field strength and large current magnets in future fusion devices.

Speaker: Mr Yong Ren (Institute of Plasma Physics, Chinese Academy of Sciences)

53 Mon-Mo-Po1.05-05 [58]: Seismic analysis of the CFETR central solenoid model coil

Abstract:The China Fusion Engineering Test Reactor (CFETR) Central Solenoid Model Coil (CSMC) is being designed and fabricated by the Institute of Plasma Physics Chinese Academy of Sciences. In order to validate structure strength and reliability of the CS Model Coil, model analysis and seismic response analysis have been carried out. Firstly, the paper established the CFETR CSMC model by using the CATIA software. Then the natural frequencies and modes of the CSMC are obtained by modal analysis. On this basis, the single-point seismic response spectrum of the CSMC is analyzed. From the results of analysis, it is concluded that the destructive effect of the horizontal seismic wave is bigger than that of the vertical seismic wave for the CSMC. Finally, El Centro, a 7.1 magnitude seismic wave, is selected to conduct the time-history analysis of the CSMC. The results reflect the maximum displacement of the CSMC coil under seismic action occurs at about 1.9 s, and the maximum displacement is 7.10 mm, 4.14 mm and 0.04 mm, respectively. During the whole earthquake, the maximum shear stress of the CSMC coil part is 2.06 MPa, which is lower than the allowable shear stress of the insulation layer of 60MPa. The maximum displacement of the whole model coil under earthquake is 10.37 mm and the maximum equivalent stress is 138.0 MPa. Our analysis results show that the design of the CSMC meets the design criteria.
Keywords: CFETR CSMC; Seismic spectrum analysis; Time history analysis

Speaker: Mr Fan Wu (a. Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031, China; b. University of Science and Technology of China, Hefei 230026, China)

54 Mon-Mo-Po1.05-06 [59]: Optimization design and mechanical analysis of the CFETR TF coil

The design of the China Fusion Engineering Test Reactor (CFETR) has been updated since the end of 2018, the major and minor radius are enlarged to 7.2 m and 2.2 m. The CFETR magnet system consists of 16 TF coils, a eight-module CS coil, 6 PF coil and 18 CC coils. It is decided recently that a TF coil will be designed and fabricated from 2019 through 2024 by the Institute of Plasma Physics Chinese Academy of Sciences, which will produce a toroidal field of 6.5 T and a peak field above 14 T. A new circle-in-square Nb3Sn CICC conductor is being designed and the CFETR TF coil will be made of the CICC conductor without radial plates. For the preliminary design, the mechanical analysis shows that the von-Mises stress on the coil case of the inner leg and the shear stress on the ground insulation are over the limit, the reason is that the self-supporting strength of the present winding pack is not strong enough. Therefore, the design of the CFETR TF coil will be optimized by modifying the conductor design, the cross-section configuration of the winding pack and the coil case dimensions. Then the electromagnetic and mechanical analyses will be performed in order to verify the feasibility of the optimization design. The pretension, cool-down and Lorentz load will be applied for the 3-D analysis, and the orthotropic smeared material properties of the winding pack calculated with the finite element method will be used. In addition, 2-D analysis of the TF cross-section will also be performed.

Speaker: Mr Xiaogang Liu (Institute of Plasma Physics, Chinese Academy of Sciences)

Xiaogang Liu_Poster_MT26.pdf

55 Mon-Mo-Po1.05-07 [60]: The CFETR CSMC Nb3Sn coil heat treatment process research

The CSMC are major components of CFETR to generate the magnetic field for Simulating the Central Solenoid coil manufacturing process.Several trials were performed to qualify and optimize the heat treatment procedure of the Central Solenoid coil. In the trials, gas replacement, temperature controlling, protective gas flow controlling, coil fixture, and assembling procedure were performed to resolve some technical issues and to demonstrate the fabrication procedure. Major requirements are: the radius increase of the conductor must be less than 4.3mm in the reaction heat-treatment when the residual stress relax; the temperature ramp rate limited to 5℃/hr; the temperature uniformity need to be satisfied ± 5℃ at the same time in whole of the furnace; The gas ,which is exhaust from the furnace and conductor ,its’ impurity content must be less than 10ppm;

Speaker: Song Jian (Institute of Plasma Physics Chinese Academy of Sciences)

Poster_The CFETR CSMC Nb3Sn coil heat treatment .pdf

Poster_The CFETR CSMC Nb3Sn coil heat treatment .pptx

56 Mon-Mo-Po1.05-08 [61]: Effects of Resonance Phenomenon caused by Power Supply on JT-60SA CS

The central solenoid (CS) of JT-60SA has four electrically independent modules, and one module is 52-layer coil combined 6 octa-pancake coils and a quad-pancake coil vertically. The CS module is supplied with current through the room temperature busbar and current feeder of the superconductor. The maximum voltage between the CS module terminals is designed to be 10 kV, the voltage between the layers under ideal conditions is then about 0.38 kV because the CS module has 52 layers. But, in operating condition, there is a possibility that the voltage between the conductors is higher than 0.38 kV due to the voltage fluctuations of the power supply and the inhomogeneous voltage distribution in the CS induced by the resonance phenomenon. Hence, it is important to investigate the voltage behavior between the conductors in the CS module.
In the previous works, the circuit simulation model was created which includes CS module (the 52-layer pancake coil), the room-temperature busbar, superconducting current feeder and the structures (ground insulation) supporting TF coil. And the influence of resonance phenomenon on voltage distribution was investigated. In this works, based on the results of the previous works, we created the circuit simulation model of the entire CS (4 modules) and estimated the voltage distribution affected by resonance phenomenon. As a result, it can be concluded that the influence of resonance phenomenon on JT-60SA CS modules is negligible small under the operating conditions. These results therefore represent important information for the safe operation of the JT-60SA.

Speaker: Mr Shogo Sonoda (Sophia university)

Mon-Mo-Po1.05-08.pdf

Mon-Mo-Po1.05-08.pptx

57 Mon-Mo-Po1.05-09 [62]: Mechanical Compress Process for Pre-compression of JT-60SA Central Solenoid

The construction of a full-superconducting tokamak referred as JT-60 Super Advanced (JT-60SA) is in progress under the JA-EU broader approach projects. The magnet system of JT-60SA consists of 18 toroidal field (TF) coils, 4 modules of central solenoid (CS) and 6 equilibrium field (EF) coils.
CS modules are manufactured one by one, then 4 modules are stacked. Finally, the pre-compression are conducted as a final process of CS manufacturing.
There are two methods for pre-compression, one is shrink fitting method, and the other is mechanical compress method. The shrink fitting method is simple method for pre-compression because it is not needed additional jig. However it is difficult to control compress load because the height and the amount of shrinkage by compress load of CS module is not completely uniform. In addition, if compress load become reduced, re-compress will be required after starting operation, but re-compress is impossible with the shrink fitting method.
Mechanical compress process was selected for pre-compression of JT-60SA CS to avoid above problems. Nine sets of hydraulic jacks and compress jigs, and stainless steel shims were used for pre-compress process to subject compress load by mechanically. Compress load of each sector can be controlled independently with this method. And re-compress after starting operation can be conducted. It means hydraulic jacks and compress jigs can be inserted from manhole of cryostat.
Pre-compression of CS module was successfully performed using mechanical compress process. The compress load of each sectors measured by strain gauges on tie plates was more than requirement of 4.2 MN/sector.
In this paper, procedure and result of pre-compression with mechanical compress process will be described.

Speaker: Haruyuki Murakami (National Institutes for Quantum and Radiological Science and Te)

20190923_MT-26_Mon-Mo-Po1.05-09_murakami_r1.pdf

20190923_MT-26_Mon-Mo-Po1.05-09_murakami_r1.pptx

Mon-Mo-Po1.06 - Motors I

Conveners: Prof. Naoyuki Amemiya (Kyoto University), Qiuliang Wang (IEE CAS)

58 Mon-Mo-Po1.06-01 [63]: Electromagnetic Performance Analysis of an Axial Flux Partitioned Stator Hybrid-excited less-rare-earth PM synchronous Machine

In recent years, axial flux hybrid-excited permanent magnet machines with high power density, high efficiency and compact structure have the potential application prospect in the electrical vehicles. Besides, due to the rare earth resource crisis, the less-rare-earth permanent magnet machines have been taken much attention. In this paper, an axial flux partitioned stator hybrid-excited less-rare-earth permanent magnet synchronous machine (APHLPSM) which combines the structure of hybrid excitation and hybrid permanent magnet is proposed. The stator of the machine is divided into two parts, which are the armature stator and the excitation stator and the rotor locates between the two stators. The armature stator includes the armature teeth and the excitation teeth, by adopting the DC field windings wound on the excitation teeth as the auxiliary excitation source, the flux-regulation capability of the machine can be achieved. The design of the stator partition alleviates the space conflict in stator-PM machines and eases the difficulty of the current control in conventional axial flux double-stator machines. The excitation stator contains three-layer PMs, where two types of PMs of ferrite and NdFeB are reasonably combined, which not only guarantees the required power but also reduces the cost.
In the first part of the paper, the power volume equation is deduced，and the initial design parameters are given. Based on the finite element method (FEM), the electromagnetic performances, including air-gap flux density, back-EMF, cogging torque, and torque, are investigated. Then, the influence of the key structure parameters of the NdFeB and ferrite PMs on the electromagnetic performances are discussed, and the flux-regulation of the AFPHSM machine is also studied in the different DC excitation conditions. Moreover, a multi-objective optimization method is applied to optimize the APHLPSM machine, where the electromagnetic performances and the flux-regulation capabilities are considered. Finally, the optimization design results will be compared with that of the initial design to validate the effectiveness of the multi-objective optimization method. It will also verify the validity of the novel AFPHSM machine.

Speaker: Mr Wenjie Fan (Jiangsu univeristy school of electrical and informantion engineering)

mt -fwj .pdf

mt -fwj .ppt

59 Mon-Mo-Po1.06-02 [64]: Study on Performance and Irreversible Demagnetization according to rotor-teeth of SPMSM

In case of Surface-mounted Permanent Magnet Synchronous Motor(SPMSM), PMs are attached to the surface of laminated core. They are connected by adhesion and magnetic force. However, in order to withstand rotation of the motor, thousands of revolutions per minute, rotor-teeth between PMs are essential to hold them strongly in position.
The rotor-teeth are also ferromagnetic material, they would be additional paths of magnetic flux in q-axis. These paths affect to flow of magnetic flux around airgap, and it could bring about leakage. Output performance get worse in this process, but also it reduces a risk of irreversible demagnetization on edge of PMs. Because load, magnetic field intensity, on PM decreases. And thicker rotor-teeth grip PMs stably more. So, it could be shown as trade-off relation. There are many variables which have influence on this phenomenon as motor composition like number of poles and slots, PM shape, airgap length, magnetic flux density, current and so on. Especially, thickness of rotor-teeth is one of them as well.
In this paper, relations between variables and effects are determined by means of analytical method. Considering variables mentioned, magnetic equivalent circuit could be offered. Both analytical method and numerical method based on a finite element analysis(FEA) are used with respect to several SPMSM models, in order to estimate that the proposed method is valid or not. Then the finding data by proposed method are compared with them of numerical method and verify that the technique is reasonable. So, we can predict the various characteristics analytically fast including performance variation and irreversible demagnetization prevention function. Also, mises stress and displacement ratio are interpreted in accordance with stability of PMs. Finally, a proper way to design optimized rotor-teeth depending of types of motor is suggested.

Speaker: Mr Seung-Gu Kang (SungKyunKwan University)

Mon-Mo-Po1.06-02 [64] _ SeungGu Kang.pdf

60 Mon-Mo-Po1.06-03 [65]: Presentation withdrawn

61 Mon-Mo-Po1.06-04 [66]: A Study on a New Structure Ferrite Magnet Motor with Improved Output Density and Mechanical Stability

Recently, much research has been conducted on non-rare-earth magnet motors due to limited reserves and high prices of rare-earth materials. Among them, a magnetic flux concentrating motor using a ferrite magnet is being commercialized in many parts. However, it is disadvantageous to high-speed operation due to the structure of the rotor. In this paper, we propose a hybrid structure of a magnetic flux concentrating and an axial motor to solve this problem and named it FC-AFPM motor. In the axial direction motor, the axes for generating torque and centrifugal force are separated from each other to ensure mechanical stability. FC-AFPM can increase the power density by using ferrite magnets, and is excellent in mechanical stability and suitable for high-speed high-torque applications. Double-sided and Single-sided FC-AFPM motor were designed and evaluated, and the validity of the proposed new structure was verified.
Acknowledgements
This work was supported by the Energy Efficiency & Resources of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant funded by the Korea government Ministry of Trade, Industry & Energy (No. 20172010105920

Speaker: Kidoek Lee (Korea Electronics Technology Institute)

62 Mon-Mo-Po1.06-05 [67]: Design and Analysis of a New Synchronous Reluctance Machine with the Aid of Grain Oriented Silicon Steel Cores

As the price of rare earth permanent magnet (PM) is very high, developing of high performance electrical machines with non rare earth PM is have received extensive attention, and synchronous reluctance machine (SynRM) has show good performance when comparing with other electrical machines. The torque ability of SynRM is proportional to its saliency ration which is determined by the rotor topology and rotor material. In this paper, a new SynRM with the aid of grain oriented steel is adopted. the main magnetic structure of new SynRM is similar to that of traditional SynRM. In this SynRM the main core are made by the traditional non oriented silicon steel and the grain oriented steel is used to fill in the part of magnetic barrier in each layer. the rolling direction of grain oriented steels filled in the new SynRM is parallel to the direction of d-axis of the rotor core, thus the main magnetic flux flows can be increased along the rolling direction of the filled material and the d-axis reluctance can be decreased greatly. On the other hand the magnetic reluctance of the new SynRM along the q-axis direction is kept the same since the magnetic permeability of the grain orient steel vertical to the rolling direction is very low and there is some air gap existed. Therefore the saliency ratio can be increased and thus the torque can be increased. In this paper, a new SynRM is designed and optimized for the electric vehicle application, its main parameters and performance have been compared with a traditional SynRM based on the finite element method (FEM). Compared with the traditional SynRM, the torque of new SynRM has been improved about 7% with only very low material cost required.

Speaker: Dr Chengcheng Liu (Hebei University of Technology)

MTMJG.pdf

MTMJG.pptx

63 Mon-Mo-Po1.06-06 [68]: A Saddle-shaped Post-assembly Magnetizing Coil for a 300 kW 2-pole High-speed Permanent Magnet Rotor

Post-assembly magnetization is usually used in manufacturing process of high-speed permanent magnet(PM) rotors. This paper reports the optimization and test of a saddle-shaped post-assembly magnetizing coil for a 300kW 2-pole high-speed permanent magnet (PM) rotor. The required magnetizing space is 85 mm in diameter and 200 mm in length. A saddle-shaped coil structure is proposed, which effectively improves the coupling performance between the coil and the rotor, and reduces the magnetic field energy by 61% in comparison with the existing triple-coil structure. During the magnetizing process, eddy currents are produced in the coil and rotor reinforced structure and permanent magnet block. The influence of eddy currents on the magnetizing magnetic field and the electromagnetic force acting on the coil structure is analyzed. By optimizing the coil structure and pulse width, the effect of eddy current on the magnetizing magnetic field is reduced to less than 1%, and the power supply energy required for the magnetizing coil is optimized to the minimum. The saddle-shaped coil was fabricated and tested and has generated transverse magnetizing field of 6 T / 25 ms in the required space. The 300 kW 2-pole high-speed PM rotor has been successfully magnetized after assembly. The measured residual magnetic flux density agreed well with the theoretical calculation.

Speakers: Prof. Houxiu Xiao (Wuhan National High Magnetic Field Center), Tao Peng (Wuhan National High Magnetic Field Center)

64 Mon-Mo-Po1.06-07 [69]: Demagnetization Analysis and Design Optimization of Permanent Magnet Synchronous Motor for Electric Power Steering Applications

Weihua Huang, Junchen Zhao, Jin Wang*, Libing Zhou
State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Schoole of Electrical and Electronic Engineering, Huazhong University of Science and Technology, Wuhan 430074, China

Abstract
With the increasing demand for electric vehicles, electric power steering (EPS) system is in the spotlight. The EPS system has high requirements for the driving motors, such as high torque density, high reliability and low torque ripple. Permanent magnet synchronous machines (PMSM) are suitable for EPS applications because they offer many advantages like high torque density and efficiency. Irreversible demagnetization of the faults permanent magnets (PM) is troublesome in permanent magnet synchronous motors since they may greatly reduce the performance. Demagnetization fault of PMSM is also one of the key factors affecting the reliability of EPS system.
This paper presents a study on demagnetization analysis method and design optimization of PMSM for EPS system. A demagnetization analysis method based on 2D and 3D finite element analysis (FEA) for PMSM of EPS system is proposed. Based on the computation of the distribution of magnetic flux density on the surface of PM, the demagnetization risk is evaluated. EPS systems are strict to cost while PM is the most expensive material, so it is necessary to restrain irreversible demagnetization under the condition of minimizing the amount of PM. Therefore, in terms of design optimization, the thickness of PM in magnetization direction is mainly optimized. The simulation results clearly show that the optimized PMSM design can meet the requirements of EPS system, which is also verified by experimental results.

This work is partly supported by the National Key Research and Development Program of China (Grant No. 2018YFB0606000)

The corresponding author is Jin Wang.
Email: hustwj@126.com

Speaker: Mr Weihua Huang (State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Schoole of Electrical and Electronic Engineering, Huazhong University of Science and Technology)

黄炜华MT26海报.pdf

65 Mon-Mo-Po1.06-08 [70]: A Study on the NVH Characteristic Analysis of a Teeth-Concentrated Winding Motor

The vibration occurring in an electric motor can be largely divided into mechanical vibration due to nonaligned bearings and shafts, and electromagnetic vibration by the electromagnetic force. For existing industrial electric motors, the mechanical vibration associated with the life of the motor was the most important concern. However, in recent years, electric motors—such as the ones used for electric cars and hybrid cars—have high-torque density by using the rare-earth permanent magnet. Thus, the relative importance of electromagnetic noise and vibration is increasing. Electromagnetic vibration and noise affect people emotionally, so it has become very important to reduce vibration when designing a motor.
There are two types of noise due to the electromagnetic field of the motor. The first is the structure-born noise, which is transmitted through the bearings of the motor to the mechanical path, and the torque riffle is the source. Second, the radial-force of the motor is the source of the air-born noise propagated to the air by the stator or housing of the motor.
In a three-phase motor, the torque ripple is produced by making the sixth harmonic of the electrical frequency as the primary wave. The magnitude of torque ripple also depends on the number of pole-slot combinations, the shape of the rotor / stator, and the magnitude of current applied. In order to analyze the radial force, which is the source of air-borne noise, an analysis of time and space harmonic of radial force density is required.
In this paper, NVH characteristics of 8p12s, 10p12s IPMSM are compared and analyzed quantitatively and qualitatively. The NVH test also measured and compared the noise and vibration levels and frequencies of each motor.

Speaker: Won-Ho Kim (Gachon University)

66 Mon-Mo-Po1.06-09 [71]: A study on IE5 class synchronous reluctance motor design using Co-analysis

In order to cope with environmental pollution caused by the recent increase in electric power consumption, 'Minimum Energy Performance Standards(MEPS)' is being implemented in developed countries. MEPS is a policy to regulate the efficiency of the motor, which is a large part of the industrial power consumption, and it is a policy to prohibit the use of low efficiency induction motors. Research has been conducted to improve the efficiency of induction motor in order to cope with this policy. However, since it is adjacent to the saturation state, researches to replace it with a synchronous reluctance motor have been actively carried out. A synchronous reluctance motor is an electric motor using reluctance torque generated by using a rotor difference of inductance and is considered to be a suitable motor to replace an induction motor due to its simple structure and manufacturing convenience. This research was conducted to achieve IE5 level of IE4 class SynRM. The output characteristics of SynRM are determined according to the rotor difference of inductance and arc type barrier is applied to maximize the difference of inductance. In addition, the shape of the arc type barrier was mathematically identified and the rotor design parameters were reduced. Whereas induction motors can be directly driven, SynRM is required to be driven by a controller composed of inverters. In order to achieve IE5 efficiency, we analyzed the efficiency distribution of existing IE4 class motors through Co-analysis and studied IE5 class SynRM design by deriving improvement model. Additional studies have also investigated the output characteristics for Pma-SynRM by inserting permanent magnets inside the rotor. Finally, to confirm the validity of this study, we conducted the fabrication and testing and confirmed that the analysis results and the test results converged.

Speakers: Jae-Kwang Lee (hanyang university), Hyunwoo Kim

Mon_Mo_Po_06_09.pdf

67 Mon-Mo-Po1.06-10 [72]: A study on the design of BLDC Slot-less PM motor using Response Surface Method

[Introduction]
Permanent magnet (PM) motors, which have various advantages such as the wide operation range and high power density, are widely developed in various industrial fields such as automobile, aerospace, home appliance, defense industry and so on. The study and development of the slot-less PM motor is actively underway as the servo and driving motor, because it does not have teeth and their corresponding slots so that it has a variety of electromagnetic and structural advantages compared to the slotted motor : No cogging torque, Smooth motor running even at low speed, Less vibrations and audible noise, and Compact design and so on. This paper presents the study of the design and analysis of BLDC slot-less PM motor with the magnetic and electric loading using Response Surface Method(RSM).
[Body & Conclusion]
In the defense industry, the slot-less PM motor is widely developed and studied for the driving motor of guided weapon. The guided weapon is necessary a high output density and efficiency motor to improve its mobility and effectively strike a fast moving target. Especially, it should have the low rotor inertia in order to have the rapid response for forward and reverse rotation. In this paper, the electromagnetic characteristics of the BLDC slot-less PM motor are analyzed by Finite Elements Analysis (FEA). And the optimal design of BLDC slot-less PM motor is conducted with RSM and 3-Dimensional FEA (3-D FEA) to meet the requirements of a driving motor of guided weapon: the high torque constant and low rotor inertia. In conclusion, BLDC slot-less PM motor is designed with the optimal design using RSM and FEA. The achievement of the objective functions of the design for the driving motor of guided weapon is verified by FEA and the experimental tests with the prototype. Therefore, this paper provides the effective design method and process of BLDC slot-less PM motor.

Speakers: Hyunwoo Kim, Hyungkwan Jang (Hanyang University)

Mon_Mo_Po_06_10.pdf

68 Mon-Mo-Po1.06-11 [73]: A Study on the Design of IPMSM for Reliability of Demagnetization Characteristics-based Rotor

The recent next-generation railway vehicles are aiming at energy saving and weight lightening and IPMSM(Interior Permanent Magnet Synchronous Motor) with a more improved efficiency and weight to output ratio than induction motor when rare-earth permanent magnet with high energy density is applied to synchronous motor have been developed a lot. Interior permanent magnet synchronous motor, used in this study is a high-capacity traction motor for railway vehicles and has a totally-enclosed structure to prevent dust, foreign materials, etc during operation as it is placed at the bottom of railway vehicles. This totally-enclosed structure is vulnerable to temperature because the cycle of heat is not good. The high-capacity traction motor for railway vehicles requires a high weight to output ratio and to increase the weight to output ratio, rare-earth neodymium permanent magnet with high energy density should be used, but are characterized by high-temperature demagnetization. Also, high current may flow due to failure in power converter and it may produce a big reverse magnetic field and be demagnetized by the reverse magnetic field. Demagnetization characteristics caused by such high- temperature demagnetization and reverse magnetization are characterized by permanent demagnetization as a new demagnetization curve called as recoil line is generated. This study proposes how to interpret demagnetization characteristics and carries out demagnetization analysis to obtain the reliability of rotor. It sets up an analysis scenario to drive electric motor based on demagnetization characteristics by considering recoil line and predicts the demagnetization of permanent magnet. And it examines the effects of output based on predicted demagnetization characteristics. It manufactures a model verified through analysis as test product and designs interior permanent magnet synchronous motor to obtain the reliability of rotor based on demagnetization characteristics proposed in this study through performance test and saturation temperature teste.

Speakers: Hyunwoo Kim, Hyungkwan Jang (Hanyang University)

Mon_Mo_Po_06_11.pdf

69 Mon-Mo-Po1.06-12 [74]: Design of Coreless PM motor using with non-magnetic tooth-slot structures using 3D printing technology

[Introduction]
It is necessary to develop a motor with high output density, high efficiency, and high control accuracy in various industries like automobiles, robots and defense industry. Among the various types of motors, Slotless permanent magnet (PM) motors having relatively structural and electromagnetic advantages over slotted motors have been continuously developed for the precise control as a driving and servo motor. However, since the slotless motor has no tooth and corresponding slots, it requires a complex winding method, applied the skew, to maintain the structure of windings so that it makes the production process complicated and requires a lot of time and money. In this paper, design method of coreless PM motor with non-magnetic tooth-slot structures using 3D printing technology, which can replace the conventional slotless motor, is proposed.
[Body & Conclusion]
This paper proposes design method of coreless PM motor with non-magnetic tooth-slot structures using 3D printing technology. The electromagnetic characteristics of coreless motor which consists of the rotor of PM and teeth-slot structure of non-magnetic material(PC: Polycarbonates) are analyzed by finite elements analysis(FEA). Coreless PM motor with 3D printing technology and the commercial slotless motor which has the skewed-winding are designed and compare the electromagnetic output characteristics each other. The coreless motor, designed with the design method proposed in this paper can improve the difficulties of the fabrication and also have advantages of the electromagnetic output characteristics that conventional slotless motor has such as no cogging torque and high precise control with compact size. In addition, it can improve the electromagnetic output characteristics by applying the overhang of the permanent magnet of the rotor unlike the conventional slotless motor. In conclusion, the effective design method of coreless PM motor using 3-D printing which provides the reliability and convenience of the design and fabrication by getting out of the winding methods of the conventional slot-less motor is proposed.

Speakers: Hyunwoo Kim, Seungheon Lee

Mon_Mo_Po_06_12.pdf

70 Mon-Mo-Po1.06-13 [75]: Design of High Torque Density Magnet Coupling Using Halbach Magnet Array Structure

This paper presents a comparison of cylindrical and plane air gap magnetic couplings in which the tile permanent magnet polarizations can be either radial or tangential or axial.The expressions of the torque transmitted between the two rotors of each coupling are determined by using the finite element method . For this system, a Halbach permanent magnet (PM) array structure is applied as a high torque density design method for a mangetic coupling. In addition, the high torque density magnetic coupling designing requires computation of the PM size by irreversible demagnetisation considering the tempera-ture environment, magnetic coupling position, and magnetic optimum design process. Finally, the validity and superiority of the optimized design are confirmed by manufacturing the prototype model and performing the experiment.

Speakers: Hyungkwan Jang (Hanyang University), Hyunwoo Kim

Mon_Af_Po_21_13.pdf

Mon-Mo-Po1.07 - Motors II

Conveners: Prof. Naoyuki Amemiya (Kyoto University), Qiuliang Wang (IEE CAS)

71 Mon-Mo-Po1.07-01 [76]: Study on Analysis Method of Asymmetric Permanent Magnet Assistance Synchronous Reluctance Motor Considering Magnetic Neutral Plane Shift

1. Introduction
   Recently, a new types of high efficiency motors are increasingly receiving attention because of the minimum energy performance standards (MEPS). A permanent magnet assistant synchronous motor (PMA SynRM) has high efficiency since it does not have copper loss of rotor in comparison with induction motor. Therefore, PMA SynRM receive attention as the new type of high efficiency motor. PMA SynRM with the asymmetric rotor can improve the torque by shifting the current phase angle of the magnetic torque and the reluctance torque. In addition, using the asymmetric rotor can reduce cogging torque and torque ripple. Therefore, research on the asymmetric PMA SynRM is actively underway. However research on the analysis method of asymmetric PMA SynRM is insufficient.

2. Body
   This paper establishes an analysis method of permanent magnet assistant synchronous motor (PMA SynRM) with asymmetric barrier. In a general motor analysis method, the inductance is calculated using the dq-axis vector diagram. In addition, the characteristics of the motor are analyzed by separating the magnetic torque and the reluctance torque. However, in an asymmetric motor, the magnetic neutral plane (MNP) is shifted because the magnetic permeance is asymmetric. Therefore, it is difficult to analysis the characteristic of the asymmetric motor because it involves errors applying the general analysis method. In this paper, the magnetic property of the asymmetric motor is analyzed and the analysis method of asymmetric motor is proposed. To verify the proposed analysis method, PMA SynRM is designed as a conventional model. Furthermore, the magnetic torque and reluctance torque are separated through the proposed analysis method. The validity of the proposed analysis method is verified through finite element analysis (FEA) and manufacture of the conventional model.

Speakers: Mr Hyunwoo Kim (Hanyang University), Mr Hyungkwan Jang (Hanyang University)

Mon_Mo_Po_07_01.pdf

72 Mon-Mo-Po1.07-02 [77]: Study on Inter-turn Fault Diagnosis of the Six-Phase Interior Permanent Magnet Synchronous Motor Using d-Axis Current

1. Introduction
   Compared to three-phase motors, multi-phase motors have higher torque density, smaller torque ripple, and higher reliability. In addition, multi-phase motors can be operated with other healthy phases, even if one phase fails. Therefore, with the increase in industrial applications that require fault-tolerance and continuous operation, such as EVs, military, and aerospace, multi-phase motors have received much attention. Similar to the three-phase IPMSM, faults of the six-phase IPMSM can be classified as: mechanical, magnetic, and electrical faults. An example of a mechanical fault is rotor eccentricity and bearing damage, an example of a magnetic fault is demagnetization, and an example of an electric fault is a turn-to-turn fault in an open-circuit phase. An inter-turn fault causes excessive current flow, which not only accelerates the breakdown of insulation but also can cause demagnetization. Therefore, if the inter-turn fault is detected in advance, the repair cost of the motor is reduced.

2. Body
   In this paper, the performance of the inter-turn fault diagnosis of a six-phase interior permanent magnet synchronous motor (IPMSM) was analyzed through d-axis current using finite element analysis (FEA). The high-frequency injection method was used to perform fault diagnosis with a current response before and after a fault. To obtain the response of the current versus the applied voltage, the voltage equation of the six-phase IPMSM was obtained for the occurrence of the inter-turn fault. In addition, the dq-axis current responses in the healthy and faulty conditions were derived from the voltage equations. Furthermore, since the response of the current is a function of the magnitude and frequency of the voltage, the performance of the fault diagnosis was determined from the magnitude and frequency of the applied voltage. To verify this, the inter-turn fault diagnosis performance was analyzed through FEA and the control simulation tool. As a result, we proposed a voltage and frequency to maximize the inter-turn fault diagnosis performance of the six-phase IPMSM.

Speakers: Mr Hyunwoo Kim (Hanyang University), Mr Seungheon Lee (Hanyang University)

Mon_Mo_Po_07_02.pdf

73 Mon-Mo-Po1.07-03 [78]: A Study on the effect of Eddy Current Loss and Demagnetization Characteristics by the Direction of Magnet division

In this paper, the influence of the change of eddy current loss of the IPMSMG (interior permanent magnet synchronous motor generator) for automotive ISG according to magnet lamination direction on the Demagnetization characteristics and vibration was studied. Reduction of the eddy current loss reduces the heat generation in the magnet and affects the demagnetization characteristics and vibration characteristics of the magnet. Therefore, in this paper, we propose a magnet structure that maximizes the reduction of eddy current loss, increases the reliability of the demagnetization, and has the low vibration characteristics that automotive motors should have.  In this paper, the operation points of ISG model are divided into three regions: motoring 3000 rpm, power generation area 4000 rpm, and 16500 rpm. Since the demagnetization characteristics and the eddy current loss depend on the lamination type of the magnets inserted into the rotor, the vertical Segmented magnet model and the horizontal Segmented magnet model are analyzed. We compare the demagnetization characteristics according to the magnet division method by applying various drive current ranges where irreversible demagnetization can be occurred. In order to analyze the effect of eddy current loss and demagnetization according to direction of magnet division on vibration, vibration characteristics are analyzed through co-simulation of electromagnetic and mechanical properties. In this study, electromagnetic analysis is performed using ANSYS Electromagnetic Suite 19.0, and the magnet division model is considered through 3D simulation. In order to compare more precise characteristics of the demagnetization, the temperature distribution of the device in the analysis program using the J-H Curve and the thermal coefficient of the permanent magnet is calculated. In addition, we analyze the effect of electromagnetic characteristics due to the magnet division on vibration by using WORKBENCH 19.0 and analyze the magnet heat distribution using CFD thermal analysis program. In order to verify the reliability of the simulation data presented in this paper, we will prove by carrying out an experiment.

Speaker: Mr Byungchan kim (keimyung university)

Mon-No-Po1.07-03[78].pdf

Mon-No-Po1.07-03[78].pptx

74 Mon-Mo-Po1.07-04 [79]: The Study on the rotor design for LSPMSM considering the Starting Torque and Magnetic Saturation

This paper presents the optimal design method of cage-bars in a single-phase line-start permanent magnet synchronous motor considering the starting torque and magnetic saturation. This method consists of two procedures. First, the basic design of cage-bars is made by analytic method of a single-phase induction motor. In this case, the equivalent magnetic circuit method is used but this method cannot consider nonlinear characteristic as magnetic saturation and leakage flux. Second, for considering the nonlinear characteristics, the optimal design of cage-bars is performed by the response surface method (RSM).
1. Procedure for Design of LSPMSM
The design process of LSPMSM is as follow. First, using the stator with winding and air-gap volume in conventional single-phase induction motor, the outside diameter of rotor can be determined. Next, the basic cage-bars design to maximize the starting torque is performed. After the basic cage-bars design is determined, the shape and the position of permanent magnet are determined. And the barrier is designed to minimize leakage of magnetic flux.
2. Optimal Rotor Design
The basic design of rotor is only considered to the starting torque. Because the LSPMSM adjust the magnetic flux path such as barriers at steady state, the LSPMSM need to consider the optimal design including the magnetic saturation and the leakage flux, which cannot be considered by analytic method. These two components are concerned with efficiency as well as starting torque.
The parameters of the cage-bars design are performed by setting up the limited flux value of possible points of the magnetic saturation and the leakage flux. Using RSM, the design of rotor calculates the optimal value.
3. Experiments
The prototype of optimized model is not manufactured. So, to verify optimized model, the FEM result and experiment result of original model are compared. Through the FEM, it was confirmed that the start time was faster than the existing model.
4. Conclusion
Through the design process, the optimized model has higher starting torque and higher efficiency.

Speaker: Won-Ho Kim (Gachon University)

75 Mon-Mo-Po1.07-05 [80]: Superconducting stage actuation

In semiconductor photolithography equipment, high productivity and nanometer precision of the motion stages are combined to enable shrink in chip dimensions at reasonable cost. High-force density linear and planar motors drive the stages which carry the reticle mask and the wafer with acceleration levels of multiple tens to hundreds of m/s2. Superconducting actuation might be a next step to increase productivity of semiconductor equipment.

Motion stages offer a new challenge to superconducting motors and their design. The dynamic motion profiles induce significant AC losses, requiring dedicated thermal design of the coils. The combination with precision pose challenges to the dynamics of the superconducting structural mechanics, as well as to the precision with which the superconducting coils are manufactured and assembled. Finally, the usage of superconducting magnets for actuation of a production machine poses specific challenges to reliability and recovery times.

The contribution will offer a glimpse on the expected loads on the superconducting coils and the specific challenges for a semiconductor motion stage application.

Speaker: Dr Gudrun De Gersem (ASML Netherlands, B.V.)

MT26_GDeGersem_SuperconductingStageActuation.pdf

76 Mon-Mo-Po1.07-06 [81]: Comparison and Optimization of Permanent Magnet Assisted Synchronous Reluctance Machine

This paper proposes a design and optimization of ferrite assisted synchronous reluctance machine. SRM(Synchronous Reluctance Motor) could be applied in electrical vehicle traction due to its salient advantage. SRM is cheaper than traditional PMSM(Permanent Magnet Synchronous Motor) because it needs no permanent magnet or some ferrite(in Permanent Magnet Assisted Synchronous Machine), which means it has lower cost. Moreover, benefiting from the simple structure of rotor, SRM can be easily manufactured and has better robustness. Also, SRM has good performance in high efficiency and wide speed range. However, SRM has some shorts in average torque, torque ripple and Power Factor, so it is necessary to optimize the topology and improve its performance.

Compared with traditional Induction Machine and Permanent Magnetic Synchronous Machine, the structure of PMASRM(Permanent Magnet Assisted Synchronous Reluctance Motor) has good performance in EVs traction. But its disadvantage is apparent in torque ripple and torque density. It should be essential to optimize its pole/slot ratio and structure of rotor. This paper is going to compare two different kinds of topologies and optimize the structure to obtain better operating performance. The two topologies differ mainly in the types of flux barrier, one of type is angular and the other is curve. The optimization is about to be imposed in the structures considering multiple factors in order to compare the performance on the different topologies.

Two different structures of the rotor are shown in the following figure. The first one is angular flux barrier, the other one is curve flux barrier.

Speaker: Mr Ding Yuanbo (State Key Laboratory of Advanced Electromagnetic Engineering and Technology,Huazhong University of Science and Technology, Wuhan, 430074, R.P.China)

MT26.pdf

77 Mon-Mo-Po1.07-07 [82]: Stator MMF Equation of Three-phase Motor Considering Sub-Harmonics for Analyzing Electromagnetic Vibration

Generally, when designing an electric device, the harmonic components in the electric angle of the MMF do not generate the average torque, so only the fundamental component in the electric angle is considered. Also, the back EMF and the torque ripple include only the harmonic components based on the electric angle. Therefore, the conventional MMF wave equation considers only the harmonic components based on the electric angle.
Conventional equations are not problematic in obtaining electromagnetic characteristics such as back EMF, torque, and torque ripple generated by electric machines. However, the distribution of radial force density, which is the cause of electromagnetic vibration of electric machines, also generates sub harmonics in addition to the fundamental component of electric angle depending on the combination of poles and slots. Therefore, in order to consider the electromagnetic vibration characteristics, the harmonic components of the MMF waveform based on the machine angle, not the electrical angle, should be considered.
For example, consider the stator MMF of the 8 pole 9 slot motor. Using the conventional equation, the spatial harmonic component of the air gap MMF waveform generated by a single-phase winding can be obtained only in the 1st, 3rd, 5th and 7th components of the electrical angle shown in black. This means that only the 4th, 12th, 20th, and 28th harmonic components of the mechanical angle can be calculated, and it is difficult to calculate the remaining sub harmonics, so that the electromagnetic vibration of the electric machine cannot be accurately predicted.
In this paper, we propose a generalized three-phase stator three-phase winding equation that can accurately calculate the spatial distribution of stator MMF for all combinations of poles and slots.
To verify the equation proposed, the magnetic flux density of the 8p9s and the 8p48s models was calculated by FEM and the proposed equation.

Speaker: Won-Ho Kim (Gachon University)

78 Mon-Mo-Po1.07-08 [83]: Study on the Design Process of the Spoke Type Permanent Magnet Synchronous Motor Considering Magnetization Performance

An important index in determining the performance of a permanent magnet synchronous motor (PMSM) is the maximization of using the permanent magnet (PM) inserted in its rotor. Thus, a process that verifies the demagnetization of PM is generally included in a design process of PMSM. However, the magnetization, which is also one of the important indexes in the design process, has not been much considered. It is due to the fact that most of the mass produced motors are categorized as surface permanent magnet synchronous motors (SPMSMs) and interior permanent magnet synchronous motors (IPMSMs) and the whole magnetization of these motors can be performed using properly designed magnetization yokes without any major trouble.
The spoke type PMSM is a shape that maximizes the surface area of PM vertically inserted in a rotor core. Also, studies on SPMSM have been actively performed because of increasing more power density than that of IPMSM. However, it plays disadvantage to the magnetization performance in a rotor structure for improving motor performances. Consequently, the whole magnetization could not possibly be performed depending on models of the spoke type PMSM and it requires a new process that has not been considered in the conventional design process of PMSM. Thus, a new design process of the spoke type PMSM that considers the magnetization performance is proposed in this study. First, types of magnetization methods and its advantages and disadvantages were analyzed. Then, a cause that decreases the magnetization performance in the magnetization method based on yokes for the mass production of PMSM was analyzed. In addition, the major factors that affect the magnetization performance in the spoke type PMSM structure were investigated, and a new design process considering the magnetization of the spoke type PMSM was proposed. Finally, a model of the spoke type PMSM was designed, fabricated, and evaluated using the proposed design process.

Speaker: Sung Gu Lee (Busan University of Foreign Studies)

MT26_Mon-Mo-Po1.07-08 [83].pdf

MT26_Mon-Mo-Po1.07-08 [83].pptx

79 Mon-Mo-Po1.07-09 [84]: Design of SMC core in Axial-Flux Motor with 3D Printing

The Axial Flux Permanent Magnet Synchronous Motor (AFPMSM), manufacturing 3 Dimensions are limited in few ways. 3D modeling is less mass-produced with high cost of unit production because stator must roll up the amorphous electrical steel plate or be molded. The study shows AFPMSM with 3D printing technique cannot be materialized in existing motor. Under the same conditions of motor design like size, amount of permanent magnet (PM), and winding used in power density of RFPMSM and new AFPMSMS. AFPMSMS includes comparative analysis of torque density between existing model produced by Soft Magnet Composite (SMC) core with molding techniques and model that contain stator shoe produced by 3D Printing technique.
The Direct Drive Type motor for front-load washer was selected in this paper. Specifications of AFPMSM were determined in size, number of poles and slots, and amount of PM usage based on the existing RFPMSM. To increase precision, the study of axial direction Dummy analysis to consider the magnetic flux leakage in the axial direction to carry out when setting up 3D finite element method. A stator core and double-sided PM rotor type which can increase the torque density efficiently by using more PM at the same size of selected among the types of AFPMSM. The shapes could bring a high torque density because of the difficulties of stacking the stator, the free shape form of 3D Printing was suitable for this study. Specifications Design of AFPMSM with parameter analysis was made stator core shape, which is applied with 3D printing technique. Firstly, existing AFPMSM was comparative analysis with AFPMSM that stack a shoe on stator teeth with 3D Printing technique. Finally, new AFPMSM were combined of high directional electric steel plate and SMC core for better performance, and the feasibility of the study was verified through prototype test.

Speakers: Mr Hyun-Jo Pyo (Gachon University), Prof. Sung Gu Lee (Busan University of Foreign Studies), Dr Suyeon Cho (KATECH), Mr Hyung-Sik Kong (Gachon University), Mr Min-Jae Jeong (Gachon University), Mr Dong-Woo Nam (Gachon University), Prof. Won-Ho Kim (Gachon University)

Mon-Mo-Po1.07-09 [84] Design of SMC core in Axial-Flux Motor with 3D Printing.pdf

80 Mon-Mo-Po1.07-10 [85]: Optimized design of segmented magnet considering demagnetization and vibration analysis of IPMSG for ISG

In this paper, the demagnetization and vibration characteristics of a 48V 5kW BLDC ISG motor generator are analyzed according to the magnet segments. Particularly, permanent magnet is divided into 3segments and 7segments as a comparison model. According to the operation characteristics of the ISG, the driving area was divided into three areas: motoring 3000rpm, power generation area 4000rpm, and 16500rpm. In general, electrical equipments of the vehicle are very sensitive to vibration characteristics and ISG is attached to the engine part of the vehicle, so specifications are given to minimize vibration. In addition, the high output ISG has a very high driving current, which causes a risk of irreversible demagnetization. And We apply various driving current ranges that can generate irreversible demagnetization. In addition, the characteristics of demagnetization and eddy current depends on the lamination type of the inserted magnet in the rotor, so this is mainly compared and analyzed. We analyze how does the stacking of magnets in the fractional slot winding method affects the eddy current loss reduction. and then Modal analysis and harmonic analysis are performed for vibration characteristics analysis and resonance frequency is found. The demagnetization phenomenon and vibration of laminated magnets are analyzed by 3D simulation. In order to analyze the effect of the irreversible demagnetization of the laminated magnets on vibration, we used mechanical Co-simulation technique. In this research, analysis was carried out using ANSYS EM and WORKBENCH. Based on the results, the optimization design was performed. In order to verify the results of this analysis, various types of magnets were made and a comparison test was conducted using various types of magnets. so we are willing to show program analysis data and experimental data.

Speaker: Byungchan Kim (keimyung university)

81 Mon-Mo-Po1.07-11 [86]: Analysis of Characteristics of Permanent Magnet Synchronous Machines with Novel Topology of Fractional-Slot Concentrated Winding

Permanent magnet synchronous machines (PMSM) with fractional-slot concentrated winding (FSCW) configuration are featured with short end windings, low mutual coupling between phase windings, high self-inductance, high slot fill-factor, reduced losses and easy and cheap manufacturing process, which makes them best choices for many applications. Based on these merits, a novel type of FSCW topology is presented. This paper investigate the method to form this topology with method of slot vector star map and slot number phase diagram, and try to find the combination of slots and poles which is available to this topology. Recent study has found that the feasible combinations of slots and poles are an even multiple of number of slots and poles of the unit machine that can use FSCW originally. And when the new topology is applied, the number of the unit machine will be halved. It means FSCW stator with even number of unit machine can apply either the original FSCW or the new topology of FSCW. In this research, a 20-pole, 24-slot PMSM is chosen to analyse the characteristics of this topology of FSCW. Conductor phasor superposition method is adopted to analysis the MMF harmonics since FSCW leads to high harmonic content, and 2D finite element analysis (FEA) is adopted to deal with the machine performances like torque ripple, harmonic losses especially permanent magnets eddy current loss and radial electromagnetic force. All the results are dealt and compared with the original FSCW under the same situation. Research has found PMSM with the new topology of FSCW configuration has lower torque ripple and lower noise under the same electric and magnetic load. Other features are currently under study.

Speaker: Mr Linwei Hu (Huazhong University of Science and Technology)

MTPoster_Linwei_Hu.pdf

82 Mon-Mo-Po1.07-12 [87]: Design and Experimental Verification of Limited Angle Rotary Torque PM Motor for Control Valve with Self-Alignment Characteristic

Torque motors for servo valves were created about 50 years ago, and they are used in several military and aerospace applications. Servo valves, which are now widely used in the general industrial and simulator fields, are still the beginning of fusion devices located at the top of hydraulic devices can do. A common torque motor uses a feedback spring for the rotor's alignment. This is a drawback that a separate mechanism is required like feedback spring. This study deals with the design and characteristics analysis of LART (limited angle rotary torque) motor, which satisfies the movement of limited angle when DC current is applied and returns to the initial position when the current is cut off through the magnetic circuit and motor shape design. LART motors using permanent magnets have a high energy density, low weight, and high efficiency. The LART motor in this study has a constant rotation range and it can be applied to a system that regulates the supply amount of fuel, oil, etc., by controlling the movement of the main control valve (MCV). Due to the characteristics of the system, when a specific DC current is applied, the desired rotation angle should be set to maintain the stationary state. When the power supply is interrupted, it should return to its initial position. In addition, ideal control is possible when there is a linear change in the torque value and the rotation range generated according to the magnitude of the current. In order to satisfy these characteristics, this paper study focuses on the design of the rotor, stator structure, the winding method based on the finite element analysis. The validity and reliability of the design method are verified using the manufactured LART motor.

Speaker: Gang-Hyeon Jang (Chungnam National University, Korea)

MT Poster_JGH.pdf

Mon-Mo-Po1.08 - Cryostats and Cryogenics

Conveners: Alexey Dudarev (CERN), Hongyu Bai (National High Magnetic Field Laboratory)

83 Mon-Mo-Po1.08-01 [88]: Presentation withdrawn

84 Mon-Mo-Po1.08-02 [89]: The Cryogenic Thermosiphon for the CEPC Solenoid

Under the construction schedule of the next generation of Circular Electron-Positron Collider building in China, the cryogenic conception design of the detector magnet is completed, and some related preliminary research works have come out good results as well. A network of LHe tubes in the thermosiphon circulating mode, which is attached to the extemal coil wall, is used to cool the coil. The thermosiphon loop has been simulated with different working media, tube lengths and diameters, heatloads. The results can help to design the thermosiphon properly for different working condition of the solenoid.

Speaker: Dr Ning Feipeng (State Key Laboratory of Particle Detection and Electronics, Institute of High Energy Physics, Chinese Academy of Science,)

85 Mon-Mo-Po1.08-04 [90]: Development of Cryostats for Superconducting Magnets at IHEP

The 3rd generation synchrotron light source will use a lot of insertion device, such as SC wiggler and SC undulator, to generate synchrotron radiation photon. The cryostat of 3W1 SC wiggler magnets have been finished assembling and cryogenic testing, the test results show that in the normal operating mode (no power failures, unexpected quenches etc.) the cryostat work with close to zero liquid helium consumption. The cryostat of SC undulator have been finished mechanical design and will start assembling at October2019. Advanced development of the cryostat of the CEPC final focus superconducting magnets have been started at September 2018 and will finish the design and construction at December 2019.

Speaker: Mr Miaofu Xu (Institute of High Energy Physics, CAS)

86 Mon-Mo-Po1.08-05 [91]: Presentation withdrawn

87 Mon-Mo-Po1.08-06 [92]: A solid nitrogen cooling system for HTS magnets

The high temperature superconducting (HTS) magnets cooled by solid nitrogen (SN2) are of great merits of lower thermal temperature gradient, better thermal uniformity and thermal stability. However, the existing cooling system cannot provide a long-term stable low-temperature circumstance for HTS magnets due to significant heat load, since they are not specially designed for the SN2. Meantime, due to the large density and thickness of the stainless steel, which is the main constituent constructing the cryostat, the whole system is too weight to realize the compact and light-weight design of the HTS magnets. To overcome these shortcomings, we utilized two radiation shields, which are cooled by liquid nitrogen and first stage of cryocooler, to reduce the heat load of SN2 cooling system as well as to improve the working time of SN2 in this study. And we have introduced a pluggable cryocooler to reduce the whole weight of the SN2 cryostat. Afterwards, we have investigated the performance of the presented cooling system in conjunction with HTS magnets, the theoretical calculation shows that the 20 liters of SN2 can work more than 6 hours from 30K to 40K without any operating and thermal problems. The results of this work could provide a diagram for the future design and construction of high efficiency SN2 cooling system for HTS magnets.

Key words: Solid nitrogen; Cooling system; HTS magnets; Heat load

Speaker: Mr Zhen Luo (Southwest jiaotong university)

88 Mon-Mo-Po1.08-07 [93]: Presentation withdrawn

89 Mon-Mo-Po1.08-08 [94]: A long-life, high-capacity and high-efficiency cryogenic system based on the Stirling-type pulse tube cryocooler developed for high-Tc superconducting applications

The cryogenic system plays a vital role in the development of superconductivity. In a sense, superconductivity would be in more widespread use now if it were not for the problems associated with the cryocoolers needed to cool the superconducting devices or facilities. For a variety of high-Tc superconducting applications such as transformers, fault current limiters, motors, generators, power cables and synchronous compensators, the technology itself is relatively mature. However, the problems associated with the used cryocoolers have hampered the advancement of their practical applications. An ideal cryocooler for the applications should have the following features: low maintenance, high reliability, long operation life, high capacity and high thermodynamic efficiency.
In the authors’ laboratory, a long-life, high-capacity and high-efficiency cryogenic system based on the Stirling-type pulse tube cryocooler (SPTC) is being developing. The pulse tube cryocooler (PTC) without any moving component at the cold end has the intrinsic merits of long life at the coldhead, and the SPTC driven by the linear compressor also achieves the high reliability at the warm end. The developing SPTC is inherited from a series of ones developed for aerospace applications and thus keeps the merits of high reliability and long life. Its mean-time-to-failure (MTTF) can reach 10 years, which is over ten times the average MTTF of most existing cryocoolers for the similar applications. Another formidable challenge for the aimed applications is often from the required huge cooling powers. The developing high-capacity SPTC can achieve 1.1 kW of cooling powers at 77 K for each unit. And multiple units can also be combined together to provide more than 20 kW at 77 K. Another advantage of the cryogenic system is that it can vary freely between 20 K and 90 K. The SPTC has also achieved the high efficiency with a relative COP of 20% of Carnot at 77 K.
The application background and design approaches will be described and the performance characteristics of the developed cryogenic system presented and discussed.

Speaker: Prof. Haizheng Dang (State Key Laboratory of Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences)

90 Mon-Mo-Po1.08-09 [95]: AC operation characteristics of conduction-cooled HTS magnet for ADR

A conduction-cooled HTS magnet is designed and tested to produce AC magnetic field of maximum 4 T for an adiabatic demagnetization refrigerator (ADR). The magnet equipped with extensive copper thermal drains is conductively cooled by a GM cryocooler to approximately 5 K and stably generates alternating magnetic field between 0 and 4 T at 0.2 T/s. The fastest ramping rate that dictates the cycle frequency of continuous ADR, is to be determined by the AC loss of the magnet assembly. The thermal loss to destabilize the AC operation of the magnet is carefully estimated and confirmed by using two different methods for cross-checking; electrical and caloric (direct temperature rise measurement) ones. The novel scheme of in situ quench detection technique is employed to eliminate an electrical inductive pick-up noise of the auxiliary metal components as well as HTS so that the non-inductive voltage signal is reliably utilized for judging the quench event of the conduction-cooled magnet. This paper addresses fast-ramping characteristic issues of HTS magnet operation for continuous ADR. The analysis of the detailed pre-quench signal prior to full quench is an essential procedure that can determine the maximum performance of ADR. The developed conduction-cooled magnet shall be indispensable for running the integrated continuous ADR operating between 5 K and 2 K.

Speaker: Prof. Sangkwon Jeong (KAIST)

MT 26 poster.pptm

91 Mon-Mo-Po1.08-10 [96]: Nab Spectrometer Magnet System

The design of a large purpose built cryogen-free magnet is reviewed. The system has been manufactured for the Fundamental Neutron Physics Beamline (FNPBL) at the Spallation Neutron Source (SNS), Oak Ridge, Tennessee.
The magnet system will house a custom spectrometer and be used to measure a, the electron-neutrino correlation parameter, and b, the Fierz interference term in neutron beta decay.
The cryostat is cylindrical, nominally 7.5m along its axis and 1.43 m in diameter. It houses a complex set of niobium-titanium superconducting windings which provide a varying magnetic field profile along a 320mm diameter gold-plated UHV bore. The bore tube extends along the full length of the cryostat and has orthogonal ports connected to the neutron beamline. A vacuum of <3.10-10 mbar is achieved.
The stray field generated by the magnet windings surrounding the UHV bore is compensated by a series of negatively wound co-axial windings which have approximately twice the diameter of the internal positive windings. The cryostat system will be housed in a passive steel shield to further compensate the stray field.
The magnet windings operate nominally at 4K and are cooled by four Gifford McMahon two-stage cryocoolers, each delivering 1.5W cooling power at their second stage. No liquid cryogens are used for normal operation of the system. The cryostat design allows the magnet system to be operated in both horizontal and vertical orientations.

Speaker: Dr Roger Mitchell (Cryogenic Ltd)

Mon-Mo-Po1.09 - Levitation and Magnetic Bearings I

Conveners: Guangtong Ma (Southwest Jiaotong University), Mochimitsu Komori (Kyushu Institute of Technology)

92 Mon-Mo-Po1.09-01 [97]: 3D modeling and analysis of superconducting tape stack conductors for uniform trapped field

Abstract
High temperature superconducting (HTS) taped stacks have broad application in magnetic levitation because of uniform induced current distribution, good heat dissipation and preferable mechanical properties. Configuration of the stack has a great influence on the uniformity and strength of the trapped magnetic field. In this paper, 3D modeling and experiments of HTS taped stacks with different stacking configurations are carried out under field cooling conditions, and the influence of three different configuration samples on the profile and uniformity of trapped field was compared. The first sample consisted of the superconducting tapes is arranged in a straight line; the second sample is the knitted tape stack (KTS); the third is inclined stacks with an angle. 3D modeling simulation is promoted by using the E-J constitutive law together with a T-A formulation to calculate the electromagnetic properties of the taped stacks. Finally, the simulation result is roughly consistent with the experimental result. Result shows that the location of the trapped field of the stacks in the straight arrangement matches the location of the tape arrangement. In the cross-shaped sample, it has been found that the maximum trapped magnetic field values appear in the regions where the superconducting tapes overlap each other, and the minimum values appear in the overlapping edges of the tapes. Compared to the other two samples, the inclined stack sample has a greater attraction for capturing a uniform magnetic field over a larger area.

Keywords: HTS tape stacks, 3D modeling and analysis, T-A formulation

Speakers: Yang Wenjiang, Liu Zhaoxin

Zhaoxin Liu---Poster.pdf

Zhaoxin Liu---Poster.pptx

93 Mon-Mo-Po1.09-02 [98]: Magnetic levitation using stacks of commercial superconducting tapes

Abstract-Stacks of commercial high temperature superconducting (HTS) tape can be magnetized to act as strong magnets for magnetic levitation. Based on our laboratory's high temperature superconducting magnetic levitation platform, in this paper, commercial superconducting tapes are used for stacking to replace the superconducting bulks. We stacked new model round bulk with a diameter of 24-mm and square bulk with a side length of 24-mm, and we have performed theoretical and experimental studies with these stacks. The samples were magnetized using a Nd-Fe-B magnet in a temperature range of 77k to 20k. The axial levitation force was measured between field cooled HTS stacks and permanent magnet in our laboratory device. We also tested the magnetic levitation force of bulk samples of the similar shapes and compared it to stacks.

Index Terms-HTS tape, bulk superconductors, stack of tapes, trapped field, magnetic bearings, magnetic levitation

Speaker: Wei Wang (Sichuan University)

Hanxin Ye ---Poster.pdf

94 Mon-Mo-Po1.09-03 [99]: Improvement of magnetic levitation force of YBCO superconductor

The top seed method and the interior seed method are com-bined for the purpose of improving the electromagnetism of the superconductor by removing defects such as processing and cracks in the YBaCuO crystal. The top seed melt growth process is widely used as a process for growing superconducting bulk.When measuring the magnetic levitation force on the upper surface of YBCO superconductor, the YBCO superconductor fabricated by Top + Interior seeding process was observed at 66.787N. In the case of the YBCO superconductor fabricated with the Interior seeding process, it was observed at an average of 37.387N. In the YBCO superconductor fabricated using the Top + Interior seeding method, the growth surface of the superconducting bulk upper seed and the part where the growth surface of the seed touches from the center are generated, so from the measurement result of the YBCO superconductor fabricated by the Interior seeding processIt is also confirmed that it is high. The Top + Interior seeding process proves to be a very effective way to complement the disadvantages of the Interior seeding process displayed on the top surface of the YBCO superconducting bulk.This research was supported by the Korean Electric Power Corporation [Grant number:R16XA01].

Speaker: Prof. Sang Heon Lee (Department of Electronic Engineering, Sunmoon University)

MT26 Mon-Mo-Po1.09-03 [99].pdf

MT26 Mon-Mo-Po1.09-03 [99].pptx

95 Mon-Mo-Po1.09-04 [100]: Analysis to the forced vibration of a high temperature superconducting system with hysteresis

Dynamic behavior with the hysteresis of the levitation force of a magnet-superconductor system is investigated with application of an alternating magnet field. The effect of a resonance swinging and break-off of the samples from the levitation level is found. Subharmonic resonance associated with the nonlinear of levitation dynamics is shown to the system. The critical amplitude vs. the field frequency to the superconductor is discussed. Levitation is stable most when the sample is exposed to a low-frequency field. In this case a large amplitude of the alternating field is needed to break-off of the sample.

Speaker: Prof. Zhao Xian-Feng (Lanzhou Jiaotong University)

Mon-Mo-Po1.09-04 [100].pdf

96 Mon-Mo-Po1.09-05 [101]: Levitation characteristics of a magnetic bearing with a superconducting stator from CC tapes

The levitation properties of permanent magnet-superconductor systems have been studied for a long time. Recently it has been demonstrated extensive possibilities of application of stacks, slabs and windings from HTSC tapes for levitation systems.
In this work a design of a superconducting passive magnetic levitation bearing on the base of HTSC flexible tapes is proposed and implemented. The bearing consists of a cylindrical stator with a superconducting winding and a concentrical rotor. The rotor consists of a set of permanent magnets located around the stator in three layers. Different configurations of superconducting windings with different numbers of pancakes and different numbers of tape layers in one pancake are implemented. The values of the horizontal and vertical components of the levitation force are measured. A comparison is made of the obtained dependences with the values of the levitation force of stacks of HTSC tapes with different numbers of tapes over the line of magnets, similar to a rotor.

Speaker: Mr Dmitry Abin (National Research Nuclear University MEPhI (Moscow Engineering Physics Institute))

97 Mon-Mo-Po1.09-06 [102]: Design and Analysis of Coaxial Magnetic Gears Considering the Electromagnetic Performance and Mechanical Stress

The magnetic gear can prevent the noise, vibration, and damage due to the noncontact drive.
Many papers have been published with regard to the design of magnetic gears. However, most design methods in the study only considered magnetic properties. The structure of the magnetic gear has two voids, and permanent magnets are located on the inner and outer rotor. And, a fixed-pole is located between the inner and outer permanent magnets to modulate the magnetic flux.
In this study, design and fabrication are performed considering only the electromagnetic performance of the magnetic gear. However, there are significant differences between the FEA results and experimental results in terms of the efficiency characteristics. In order to analyze the errors of the analysis and measurement results, the stress analysis was performed from the results of electromagnetic force characteristics analysis of the manufactured magnetic gears. As a result, it can be confirmed that the stress distribution of the fixed core is out of the yield stress. For this reason, it can be seen that the deformation of the fixed iron core occurs and the loss due to friction is greatly increased.
In this paper proposes a method for the design and analysis of coaxial magnetic gears considering the mechanical stress as well as the electromagnetic performance. Considering the magnetic and mechanical properties of magnetic gears, the design area to increase permanent magnet usage to within 10% compared to the existing model and satisfy the maximum pull-out torque of the same level was derived. Then, the optimum design model in which the yield stress does not occur is presented through the stress analysis of each model. The production of the magnetic gear, electromagnetic and mechanical analysis, and the design method will be explained in detail in the final paper.

Speaker: Jeong-In Lee (CHUNGNAM NATIONAL UNIVERSITY)

2019_MT_MG_poster.pdf

98 Mon-Mo-Po1.09-07 [103]: Design and Analysis of a Special Lateral Suspension Coil for a Spherical Superconducting Rotor

At temperatures near absolute zero, the materials used in the superconducting magnetic suspension device are chemically inactive and the electrical losses are very low, which makes the device have a high accuracy in measuring angular velocity and angular displacement. In order to determine the accuracy of the device, it is necessary to carry out the drift test for the device. One of the commonly used methods for drift test is the torque feedback method. However, this method requires that the device be able to rotate 90 degree. In this paper, in order to meet this requirements of the drift test, four special lateral suspension coils were designed, which were evenly distributed along the equator of the spherical rotor. When the device was deflected by 90 ° for the drift test, circumferential support forces can be provided by the four lateral suspension coils. Levitation characteristics of the lateral suspension coils were analyzed by using 3-D magnetic field finite element analysis method. Due to the special structure, a tooling was designed for winding the lateral suspension coils. The results will be helpful for the drift test of the superconducting magnetic suspension device next step.

Speaker: Dr Hao Wang (Institute of Electrical Engineering, Chinese Academy of Sciences)

99 Mon-Mo-Po1.09-08 [104]: Structure and Electromagnetic Characteristics according to Pole Piece Supporter Material of Magnetic Gear

Magnetic gear which is capable of non-contact transfer torque has replaced mechanical gear and has advantages of high-efficiency and improved reliability. Common electrical devices, such as motors and generators, have a single air gap. However, there are two air gaps in the magnetic gear, and a laminated structure called a pole piece is arranged between the two gaps at regular intervals in the circumferential direction. This structural feature causes difficulty in mechanical earth of the pole piece. In this paper, two methods of supporting the pole piece are presented.
Model 1 was made of non-magnetic metal as the material of the pole piece supporter and Model 2 was made of epoxy. Model 1 was easy to fabricate and mechanically robust, but it was confirmed that eddy current loss occurred in metal pole piece supporter. The higher the rotation speed, the higher the loss exponentially and the lower the output and efficiency. On the other hand, Model 2 had no eddy current loss, but was not mechanically robust, and was damaged during the experiment due to circumferential torque and vibration acting on the pole piece.
This paper presents information on the advantages and disadvantages of the pole piece supporter according to the materials. Through the result, it is possible to consider materials suitable for the pole piece supporter according to the torque and rotation speed of the magnetic gear. Each model was designed with 3D-FEM to improve analytical reliability. An opinion is also presented on the torsional stiffness of the pole piece, which was mentioned as one of the causes of the decline of analytical reliability in previous studies.
Specific design and experiment contents are disclosed through the full paper.

This research was supported by Korea Electric Power Corporation. (Grant number: R19XO01-34)

Speaker: Eui-Jong Park (Chosun University)

Mon-Mo-Po1. 09-08.pdf

100 Mon-Mo-Po1.09-09 [105]: Electromagnetic Analysis of Linear Magnetic Gears according to the Characteristics of their Flux-Modulation Poles

Because typical electrical devices cannot be driven without a power converter, the use of gears is essential. Various studies have focused on magnetic gears without mechanical losses. In certain linear motion systems, such as wave energy power generators, using linear gears is inevitable. The most important aspect of gears in linear systems is manufacturing feasibility. Recently, research on linear magnetic gears has focused on tubular structures. However, tubular magnetic gears have the disadvantages of being difficult and expensive to manufacture. Alternatively, similar performance can be achieved by simplifying the tubular structure to a linear one. There are unfortunately few researches on simplified linear magnetic gears to date, and this is therefore very important.
In this paper, we performed an electromagnetic analysis of simplified linear magnetic gears (LMGs) according to the characteristics of their flux-modulation poles (FMPs). The performance of LMGs varies greatly depending on the characteristics of their FMP. Therefore, we proposed the optimal type of LMG by comparing the characteristics of the FMPs of three types of LMGs: non-laminated core, laminated core, and soft magnetic composite (SMC) core. Generally, non-laminated cores yield low efficiency because of core losses and eddy current losses, but their stiffness is vastly superior. Laminated cores have low stiffness but high efficiency because of their low electromagnetic losses. SMCs offer several advantages, including low core losses, low eddy current losses, 3-D isotropic ferromagnetic behavior, flexible machine design, and relatively good recyclability. By comparing these characteristics, we show the superiority of simplified LMG fabrication and its performance and then propose the best type of FMP by comparing their electromagnetic characteristics. The final focus of our electromagnetic analysis is determining the feasibility of constructing a simplified linear magnetic gear, along with its manufacturing cost, electromagnetic characteristics, and safety during operation. All results are validated through FE analysis and experimental results. Therefore, the final manuscript will cover more details about analysis process.

Speaker: Sung-Won Seo (Chungnam National University)

MT_Poster_LinearGear_v01.pdf

101 Mon-Mo-Po1.09-10 [106]: Self-sensing Modeling of Rotor Displacement for Six-pole Hybrid Magnetic Bearing Based on Improved Particle Swarm Optimization Support Vector Machine

A magnetic bearing uses eddy current sensors or Hall sensors to detect rotor displacement, which results in the problems such as large volume, increased cost and reduced reliability. Therefore, the research on self-sensing methods of rotor displacement for magnetic bearings has theoretical and application value. State estimation method and parameter estimation method have problems such as complicated structure and over-dependence on precise mathematical models. The neural network method does not depend on the mathematical model and parameters of the magnetic bearings, but it is easy to fall into the local optimum and its convergence speed is slow. In this paper, a self-sensing method of rotor displacement for six-pole double-stator hybrid magnetic bearing (HMB) based on improved particle swarm optimization (PSO) least square support vector machine (LS-SVM) is proposed, which can accurately predict the rotor displacement of HMB.
The structure and working principle of the six-pole HMB are introduced, and mathematical model is deduced. Based on the regression principle of LS-SVM, the prediction model between currents in control coils and rotor displacements is established, and the performance parameters of LS-SVM are optimized by improved PSO. In the process of optimization, the mean square error between the predicted value and the measured value is taken as the evaluation criterion to compare the prediction ability of the improved PSO with the standard PSO. The comparison results show that the performance of the prediction model based on the improved PSO LS-SVM is obviously better than that of the standard PSO. The simulation system for self-sensing modeling of rotor displacement for the six-pole double-stator HMB is constructed. The simulation results show that the method is feasible. Simulation experiments on floating and anti-interference are carried out, and the simulation results verify the feasibility of the method.

Speaker: Ms Mengyao Wu (Jiangsu University)

Liu Tiantian-Poster.pdf

Liu Tiantian-Poster.ppt

102 Mon-Mo-Po1.09-11 [107]: Parameter Optimization Design of Six-pole AC Hybrid Magnetic Bearings Considering Variable Stiffness

Besides the advantages of the conventional magnetic bearings such as high speed and high precision, AC magnetic bearings also have strengths such as small size and low cost because of the use of mature technology of inverter driving. Therefore, AC magnetic bearing has potential application prospects in industrial manufacturing, aeronautics and astronautics, wind power generation and other fields. However, the installation error of displacement sensors or the influence of the rotor non-uniform material and non-uniform heating will cause the working position of the rotor to deviate from the given reference position, resulting in the change of the stiffness of the magnetic bearing at different positions, which will reduce the rotation accuracy of the rotor and limit the further increase of rotor speed. In this paper, the influence of variable stiffness on the six-pole AC hybrid magnetic bearing is analyzed, and parameter optimization design is proposed.
Firstly, the structure of six-pole AC hybrid magnetic bearing is introduced and the formula of radial suspension force is derived by using the equivalent magnetic circuit method. Secondly, the variable stiffness coefficient is deduced according to the eccentric displacement , and the influence of the variable stiffness coefficient on the parameters design of magnetic bearing is analyzed. Thirdly, the parameter optimization design of six-pole AC hybrid magnetic bearing is carried out with reference to the characteristic of variable stiffness coefficient. Finally, simulations and experiments are carried out, the displacement waveforms of the rotor including floating, stable suspension and under external disturbance are tested. The simulation and experimental results show that the static and dynamic characteristics of the magnetic bearing are excellent. In other words, the parameter optimization design of the six-pole AC hybrid magnetic bearing which considers variable stiffness is feasible.

Speaker: Ms Mengyao Wu (Jiangsu University)

Wu Mengyao-Poster.pdf

Wu Mengyao-Poster.ppt

103 Mon-Mo-Po1.09-12 [108]: Decoupling Control Based on Active Disturbance Rejection Control of Six-pole Radial-axial Active Magnetic Bearing

With the development of energy saving and advanced equipment in the modern industry, the requirement of high-speed and high-power density motor are developing. Compared with the conventional bearings, magnetic bearings have the advantages of no friction, no lubrication and sealing, high speed, high precision, long service life. Thus, Magnetic bearings have been widely used in high-speed turbines, compressors, and high-speed motorized spindle, flywheel energy storage system, and so on. At present, the three-pole magnetic bearing driven by three-phase power inverter is a common magnetic bearing. The three-phase power inverter has the advantages of mature technology and low price, which can greatly reduce the cost of the magnetic bearing. However, the three-pole magnetic bearing has the disadvantage of low bearing capacity, low space utilization and so on.
Therefore, a six-pole radial-axial active magnetic bearing (AMB) driven by an inverter is proposed, which axial biased flux and radial biased flux are both provided by the axial biased current. Firstly, the configuration, working principle and mathematical model of the six-pole radial-axial AMB are analyzed in detail. Secondly, the working principle of the six pole radial-axial AMB is verified by finite element analysis (FEA). Thirdly, the advantages and disadvantages of linear active disturbance rejection control (LADRC) and nonlinear active disturbance rejection control (NLADRC) are analyzed, and decoupling control of six-pole radial-axial active magnetic bearings by the linear/nonlinear active disturbance rejection switching control (SADRC). When the disturbance is large or the output state estimation error is large, the LADRC is used in the system, otherwise, the NLADRC is used in the system. Finally, related experiments based on the prototype are also conducted to verify the superior performance of the SADRC. The results show that the decoupling control effect of the SADRC is better than that of LADRC and NLADRC.

Speaker: Mengyao Wu (Jiangsu University)

Wang Shaoshuai-Poster.pdf

Wang Shaoshuai-Poster.pptx

Mon-Mo-Po1.10 - Levitation and Magnetic Bearings II

Conveners: Guangtong Ma (Southwest Jiaotong University), Mochimitsu Komori (Kyushu Institute of Technology)

104 Mon-Mo-Po1.10-01 [109]: Optimal Design and Performance Analysis of Six-pole Hybrid Magnetic Bearing

Comparing with traditional bearings, magnetic bearings have the advantages of no friction, no lubrication, high speed, high precision, long life, etc.. Therefore, magnetic bearings have broad application prospects in the fields of flywheel energy storage, wind-generated electricity, high-speed machine tool and so on. The six-pole hybrid magnetic bearing is driven by a three-phase inverter, thus the volume of the magnetic bearing is reduced and the overall cost of the magnetic bearing is cut. However, there are still many shortcomings in the hybrid magnetic bearing for the practical application. For example, the iron core material is utilized inexpediently, and the coil turn number is designed unreasonably, which affects the current stiffness of magnetic bearings.
In order to overcome the problems above, the optimal design of six-pole hybrid magnetic bearings is proposed in this paper. Firstly, on the basis of introducing the structure and working principle of six-pole hybrid magnetic bearings, the mathematical models of radial suspension forces of six-pole magnetic bearings are derived. Secondly, according to the requirements of the test prototype, the main parameters (such as air gap length, stator pole shoe thickness, stator magnetic pole area and coil turn number) of the six-pole magnetic bearing are designed and optimized, and the radial suspension forces are analyzed by using the finite element software. Finally, the static floating and disturbance experiments of the six-pole hybrid magnetic bearing are carried out. The theoretical research and experiments show that the magnetic circuit structure of the six-pole hybrid magnetic bearing is reasonable, and the static suspension force and the maximum suspension force can both meet the performance requirements.

Speaker: Mengyao Wu (Jiangsu University)

Liu Gai-Poster.pdf

Liu Gai-Poster.ppt

105 Mon-Mo-Po1.10-02 [110]: Dynamic behaviors of the axial levitation force for the radial-type superconducting magnetic bearings

It is crucial to calculate the levitation force in the designation of superconducting magnetic bearing (SMB). Due to the external disturbances or the time-variable load, it is necessary to study the dynamic levitation behavior in order to ensure the stable levitation of SMB. In this paper, we investigate the dynamic behaviors of the axial levitation force for the radial-type SMB. By adopting the Power-law E-J relation of the superconductor, the simplified H-formulation finite element model of the radial-type SMB is established to calculate the axial levitation force in the PDE module of software COMSOL. The experimental measurements of the levitation force are carried out in both the field cooling and zero-field cooling condition so as to validate the model. Then, the dynamic model is built with the aid of ODE module, which can describe the dynamic response of the PM rotor along the z-axis easily. The dynamic behaviors of the radial-type SMB are discussed when the PM rotor suffer from the external disturbances including the axial constant load with different initial velocity and the sinusoidal time-variable load. The study is useful to predict the influences of the external disturbances on the dynamic levitation behaviors in the practical applications of the radial-type SMB.

Speaker: Prof. Guomin Zhang (Key Laboratory of Applied Superconductivity, Institute of Electrical Engineering,Chinese Academy of Sciences)

106 Mon-Mo-Po1.10-03 [111]: Rotational test of integrated magnetic bearing using multiple HTS cubic bulk units.

We are studying magnetic bearings combining multiple cubic superconducting bulks. Calculate the placement by optimum calculation so that the fluctuation of the trapped magnetic flux distribution is minimized according to the cubic bulk arrangement and decide the optimum arrangement for the magnetic bearing.
In this experiment, eight magnetic cubic blocks were arranged in a square to construct a magnetic bearing surface. A verification experiment was carried out with a model in which the rotating floating body as a permanent magnet was sandwiched between upper and lower bearing surfaces, with the magnetic bearing surface as one side.
This research report summarizes the influence on rotational test etc. based on the index of optimal placement.

Speaker: Kazuhito YAMAGISHI (Yokohama National University)

MT26_Mon-Mo-Po1.10-03[111].pdf

107 Mon-Mo-Po1.10-04 [112]: Dynamic Characteristics in The Horizontal Direction for New Type SMB Using SC Bulk and SC Coil

.
INTRODUCTION
Recently, magnetic levitation techniques have been developed for various fields such as energy storage flywheels and magnetically levitated vehicles. Thus, there are many reports about levitation techniques using high critical temperature (Tc) superconducting magnetic bearings (SMBs) composed of superconducting (SC) bulk and permanent magnet (PM). In this paper, new SMBs composed of SC bulk, SC coil and PM are discussed.
SC BEARING AND EXPERIMENTAL METHOD
In this paper, we propose a SC bearing composed of SC bulk, SC coil and PM. The levitation is performed using pinning force between SC bulk and PM. A neodymium (NdFeB) PM with a diameter of 27 mm and a thickness of 3.4 mm is used. The SC bulk (Dy1Ba2Cu3OX, Jc=3 ×108 A/m2 at 77 K and 1.0 T) measures 44 mm in diameter and 7.5 mm in thickness. The yttrium type SC coil (Ic=150A) measures 35mm in inner diameter, 38mm in outer diameter and 5mm in thickness with four turns. The SC bulk and the SC coil are field-cooled using liquid nitrogen.
EXPERIMENTAL RESULTS AND DISCUSSIONS
In the experiments, the SC bearing with SC coil is compared with the SC bearing without SC coil. The distance between SC bulk and PM is changed at 7mm, 8mm and 9mm. At each distance, impulse responses for the SC bearing without SC coil are performed. The result shows that the displacement amplitude for each distance decreases gradually as the time increases.
Impulse responses for the SC bearing with SC coil are performed. The displacement amplitude for each distance decreases rapidly. It is found that the damping for the SC bearing with SC coil is larger than that for the SC bearing without coil.
SUMMARY
The SC coil is effective on the damping for the SC bearings. From the experimental results, both stiffness and damping coefficient for the SC bearing with SC coil are improved compared with the SC bearing without SC coil.

Speaker: Prof. Mochimitsu Komori (Kyushu Institute of Technology)

Poster(Wada).pdf

108 Mon-Mo-Po1.10-05 [113]: Characteristics Comparison of Magnetic Gears According to Permanent Magnet Material

Studies on coaxial magnetic gears (CMG) have been actively conducted. CMGs can replace mechanical gears as they can perform noncontact power transfer, thereby minimizing loss and damage from friction.
However, the permanent magnet eddy current loss among the electromagnetic field loss of the magnetic gear is pointed out as the biggest problem in the high speed drive. Among other losses, iron loss can be greatly reduced by stacking electrical steel sheets, while permanent magnets have many technical problems to be stacked like electric steel sheets. The biggest cause of permanent magnet eddy current loss is electrical conductivity of rare earth magnets. In this paper, we applied the ferrite permanent magnet and the NdFeB permanent magnet to the magnetic gears in order to compare the characteristics of the magnetic gear according to the electric conductivity of the permanent magnet. Ferrite and NdFeB were used to design magnetic gears that exhibited the same torque, and then the characteristics of each magnetic gear at the same drive speed were compared. Since the ferrite is not electrically conductive, the ferrite-applied magnetic gear does not exhibit permanent magnet eddy current loss. However, we observed mechanical and electric problems due to its size. Also, the efficiency of the two magnetic gears was reversed on a specific speed.
In this paper, we provide information on mechanical and electromagnetic losses of magnetic gears, and it is possible to examine suitable application fields of magnetic gears according to permanent magnet materials. Each model was compared with the mechanical and electromagnetic characteristics of the two models through FEM design and prototype production. Specific design and experiment contents are disclosed through the full paper.

Acknowledgement: This research was supported by Korea Electric Power Corporation. (Grant number: R19XO01-34)

Speaker: Eui-Jong Park (Chosun University)

Mon-Mo-Po1. 10-05.pdf

109 Mon-Mo-Po1.10-06 [114]: Design, fabrication and testing of a 15-m long YBCO magnet-based linear synchronous motor for EDS train

A HTS linear synchronous motor (LSM) that uses YBCO-coated conductor as the secondary excitation system and double layer concentrated windings as the primary was recently demonstrated in our laboratory. Two YBCO-coated conductor racetrack coils were wound on a fiberglass frame via the epoxy impregnation technique and injected dc currents to provide a high stationary magnetic field for LSM. Thirty-nine copper racetrack coils manufactured modularly were assemblled into double layer concentrated winding to act as the primary of a 15-m long test line. Prior to assembling the whole system, we tested the current versus voltage curve of the connected YBCO coils with a four-proble setup, and the short circuit test and steady state test were processed on home-made electromagnetic force testing system to investagte the starting characteristics and back electromotive force of HTS LSM. Using a frequency converter to regulate the three-phase currents of stator, the secondary system could take a back-and-forth movement along the stator at electromagnetic clearances of ~50 mm. Dynamic measurements were carried out to observe the transient thrust and thrust fluctuation against the input current of the YBCO coils, clearance as well as the amplitude and frequency of the primary current. Moreover, we also established a finite-element model using which the transient thrust and thrust fluctuation at various speeds (up to 613 km/h) of the prototype were computed and found to be comparable with the measured dataset. This work has advanced the study of YBCO-coated conductor linear motor from the static measurements to the dynamic operation, taking a step forward to the application of such promising linear traction system of EDS train.

Speaker: Guangtong Ma (Southwest jiaotong University)

110 Mon-Mo-Po1.10-07 [115]: Design and optimization of closed-loop NI-HTS coils for a prototype EDS-Maglev system

Recently non-insulation (NI) HTS coils using coated conductors (CCs) draw extensive attention because of their self-protecting capability. Closed-loop coils are also promising in the application of electrodynamic-suspension (EDS) Maglev train with superconducting magnets since the heat load of the on-board magnet can be significantly reduced, typically >50%. Therefore, closed-loop NI-HTS coils are proposed to be employed in our prototype EDS-Maglev system.

Several key points on the coil design/optimization are considered and supposed to be presented: (1) Topological structure. Each on-board magnet has at least one pair of N-S poles. Each pole is composed of several, typically 4-8, double-pancake coils with a race-track shape. The optimization target is to use the least number of joints between and inside these coils and poles, especially bridge-type joints which usually are with high resistances. (2) Turn-to-turn contact resistance, which is mainly determined by the material of stabilizer layer and the contact pressure. These two factors are ex-situ studied experimentally with short CC tapes and verified in a practical coil; (3) The normal-state resistance of the PCS, which is determined by its operation temperature, the tape length and also by the material of stabilizer layer. Actually this factor has a similar influence on the charging speed as the turn-to-turn contact resistance. Therefore “how large it should be” is analyzed in the same circuit model. And then we achieve it according to our experimental study on temperature and material of stabilizer layer. (4) The decay rate. Our target is less than 1%/day. This is important for the daily operation of a real maglev train and mainly determined by the joint resistance as well as the topological structure (inductance, joint number and type), if not considering the influence of external AC magnetic field. (5) The bobbin structure. With an optimized structure, the turn-to-turn contact pressure can be controlled with an acceptable precision. Also the coils are hoped to be bonded to the bobbin with practical insulation and thermal conductance simultaneously.

Speaker: Dr Wei Wu (Shanghai Jiao Tong University)

Mon-Mo-Po1.10-07.pdf

111 Mon-Mo-Po1.10-08 [116]: Magnetic Levitation Characteristics of HTS bulk above new type of Electromagnets for HTS Maglev

Recently, we investigated High Temperature Superconductor (HTS)-ElectroMagnet (EM) interaction characteristics with experiments and computer simulations. In this investigation, new type of EMs with different geometries were designed and built for comparative analysis. We also set up a three dimensional force measurement system to evaluate the levitation and guidance forces with different EM geometries and configurations. The magnetic field distribution at different EM configurations and different excitation conditions was simulated with a commercial FEA software. The simulation results were verified by the experimental ones. The goal of this study is to explore the practical applications of a HTS-EM levitation transportation system. In principle, EM rails are able to adopt a Segmented Instant Excitation (SIE) mode to realize a minimum levitation power loss as well as sufficient levitation and guidance forces for the train. In this presentation, we report the details of this study and confirm the feasibility of a HTS-EM levitation transportation system.

Speaker: Mr Chaoqun Zhao (Tianjin University)

Poster-Zhao-MT26.pdf

112 Mon-Mo-Po1.10-09 [117]: A quadratic approximation method for the limit value of magnetic stiffness in a high temperature superconducting levitation system

In this paper we present a quadratic approximation method for the limit value of magnetic stiffness in a high temperature superconducting levitation system. The levitation configuration discussed is that of a cylindrical permanent magnet (PM) placed above a coaxial high temperature superconductor (HTS). The magnetic levitation force between the PM and the HTS is obtained on the basis of Kim’s critical model and Ampère circulation theorem. The central issue of magnetic stiffness associated with the hysteresis of levitation force is discussed. To a given levitation gap between the PM and the HTS, the approximate values of magnetic stiffness are obtained corresponding to different displacement increments from 0.1mm to 3mm. In the first approximation the least squares method is used to curve fitting force-displacement table. Secondly, the limit value of magnetic stiffness is gained at the zero displacement increment in the polynomial fitting curve of these approximate values. The results show that the limit value of magnetic stiffness is dependent on the levitation gap and the movement direction of the levitated object, which is believed to be responsible for the penetration history of shielding currents distribution in HTS and magnetic field gradients. Some displacement increments, such as 0.5mm or 1mm, are usually used in superconducting levitation experiments. The difference between experimental data of magnetic stiffness and the limit ones is also investigated.

Speaker: Prof. Xian-Feng Zhao (Lanzhou Jiaotong University)

Mon-Mo-Po1.10-09 [117].pdf

113 Mon-Mo-Po1.10-10 [118]: Design of a Fan-shaped Electromagnetic Guideway for HTS Maglev and Analysis of its Performances

A new type of electromagnetic guideway for high temperature superconducting maglev was proposed in this paper. The guideway unit is a fan shaped electromagnet that can generate magnetic field for providing enough levitation and guidance forces. A simple multi-object optimization method was used in order to determine the relative optimal geometrical parameters, so that the electromagnet can have a relative higher energy transfer efficiency. The design model was built in COMSOL Multiphysics and an experimental prototype was made to verify the design feasibility. The levitation and guidance forces were measured by a high precision force-measuring platform. The levitation performances of guideway unit along with different variables were analyzed and compared with the simulation results. Afterward, a simple maglev system was built to test the driving stability in the guideway direction. This system consist an electromagnetic guideway and a train body dewar. The guideway can be assembled in two forms: single track and double track. The comparison between the both forms was discussed and analyzed.

Speaker: Ms Wei Hong

Poster-Hong-MT26-2.pdf

114 Mon-Mo-Po1.10-11 [119]: Demagnetization performance of Superconducting Permanent Magnets under Vibration in Electrodynamic-suspension Levitation System

Superconducting permanent magnet such as bulk, stack tapes and ring-shape magnet has been proved to be a potential candidate for superconducting motors. In real applications, especially the superconducting electrodynamic-suspension(EDS) levitation system, vibrations in all directions during high speed operation are unavoidable. This paper focuses on the demagnetization process of superconducting permanent magnets under different kind of vibrations. Firstly, test samples, including stack tape, ring-shape magnet, are fabricated by laser cutting and epoxy packaging technique. Modification of commercial vibration platform is done to represent the vibration condition of EDS levitation system. The central magnetic field is chosen as the key parameter to evaluate the demagnetization performance of test samples. Both experimental and numerical methods are used to explore the demagnetization mechanism during vibration. Results obtained in this paper will be crucial for the design of excitation system as well as the cooling system in the EDS levitation system.

Speaker: Dr Jie Sheng (Shanghai Jiao Tong University)

Mon-Mo-Or1 - Fusion II: Projects Around the World

Conveners: Alfredo Portone (Fusion For Energy/European Commission), Boris Stepanov (EPFL)

115 Mon-Mo-Or1-01 [Invited]: The conceptual design of the DTT superconducting magnet system

The “Divertor Tokamak Test” is an experimental machine currently under construction in Italy, at the Frascati research center of ENEA. The main goal of this project is to explore various divertor solutions for defining the best way to manage power and particles exhaust, in view of the realization of the EU-DEMO machine. The DTT magnet system is fully superconducting and it is based on NbTi and Nb3Sn Cable-in-Conduit Conductors. It consists of 18 Toroidal Field (TF) coils plus 6 Poloidal Field (PF) and 6 Central Solenoid (CS) stacked module coils, all independently fed. The magnet system design was already presented in its previous versions, but as analyses and technical choices have further progressed, in this work the up-to-date design solutions are presented and discussed. An overview of the technical needs leading to the present conceptual design is given, having particular care of discussing the aspects that mainly impact on the procurement and construction phases which are on-going.

Speaker: Aldo Di Zenobio (ENEA)

Mon-Mo-Or1-01-Conceptual Design of DTT magnet system_A Di Zenobio_MT26.pdf

Mon-Mo-Or1-01-Conceptual Design of DTT magnet system_A Di Zenobio_MT26.pptx

116 Mon-Mo-Or1-02: Design of the inter-coil structures and supports of the DTT magnet system

The “Divertor Tokamak Test” is an experimental machine currently under construction in Italy, at the Frascati research center of ENEA. The main goal of this project is to explore various divertor solutions for defining the best way to manage power and particles exhaust, in view of the realization of the EU-DEMO machine. The DTT machine is relatively compact, and the magnet system works at high fields, this combination being quite challenging from the mechanical point of view. In particular, the loads acting on the Inner and Outer Inter-coil structures, on the Poloidal Field coils supports and on the gravity supports of the whole magnet system, are quite demanding. An overview of the design solutions adopted for all the inter-coils structures and supports is presented in this work, focusing particularly on their industrial feasibility.

Speaker: Mr Alessandro Anemona

Mon-Mo-Or1-02-Design of the inter-coil structures and supports of the DTT magnet system_A Anemona_MT26_01.pptx

117 Mon-Mo-Or1-03: Challenges of Superconducting Magnet System and Development of TF Prototype Coil of CFETR

Research and engineering design work of superconducting magnet system of CFETR (China Fusion Engineering Test Reactor) is in progress and supported by China government. The major radius and minor radius of CFETR is designed as 7.2 m and 2.2 m, respectively.
For one hands, such big size will bring big challenges to the magnet system because it will be difficult to get high enough volt seconds and magnetic field in plasma center. For another hands, high voltage seconds generated by central solenoid coils and high magnetic field provided by toroidal field coils are required to get high performance plasma with current of 10-14 MA. Therefore, to generate high enough magnetic field of 6.5 T field at R= 7.2m, the peak field at TF coils will reach to 14.3 T. The big challenge will be the enough stability margin and enough temperature margin of the high-Jc NB3Sn CIC (cable-in conduit) conductor.
Besides, China government support new funding ($600 Million) to design and manufacture a TF prototype coil since from 2019. Although the engineering design work goes smoothly in now stage, it is still big challenge to get high enough stability margin of the TF coil under the condition of peak field of 14.3 T. Besides, the peak stress of the TF coil will be about 700MPa. The new design of high Jc Nb3Sn conductor and structure of TF prototype coil will be detailed introduced.
In addition, the eight CS coils with HTS insert coil which can reach to peak filed of 17 T are investigated which can provide a high voltage second of 480V•s in the plasma region. The poloidal field coils are far away from plasma, so the big overturning moment generated by PF coils is a big challenge for snowflake plasma equilibrium configuration. It hopes that the presentation can not only be good reference for other DEMO projects, but also a good bridge for the broad international cooperation for fusion research work.

Speaker: Dr Jinxing Zheng (Institute of Plasma Physics, Chinese Academy of Sciences)

Mon-Mo-Or1-03_Jinxing ZHENG.pdf

118 Mon-Mo-Or1-04: Design of CFETR TF Prototype Coil

Design of CFETR TF Prototype Coil
Wu Yu, Shi Yi, Lu kun, Liu Xiaogang, Qin jinggang, Liu Xufeng, Hao Qiangwang, Li Junjun, Hu Yanlan, Xiao Yezhen, Shen Guang, Han Houxiang, Wei Jin, Fang Chao, Yin Dapeng, Li Jiangang.
Abstract
China Fusion Engineering Test Reactor （hereinafter referred to as “CFETR”）, based on ITER technology and bridged between ITER and DEMO, has been supported by China government to start technologies R&D and engineering design. Superconducting coil is treated as important device for fusion reactor. The field of CFETR at plasma core is 6.5T, maximum field of TF coil is about 14.5T. TF coil is winded by high-performance Nb3Sn wires and CICC conductors. Coil weight is about 550T with height about 22m and width about 15m. Design and manufacturing technologies of TF coil need to be developed and validated. TF coil design consists of mechanical & electro-magnetic design and analysis, conductor design and analysis, coil AC loss analysis, thermal-hydraulic analysis and coil cooling, quench detection and coil protection, coil winding, case manufacture, and coil assembling. Engineering design has been carried out at ASIPP. Duration for design and manufacture will be 5 years.

Key words: CFETR, TF coil, CICC.

Speaker: Yu Wu (ASIPP)

119 Mon-Mo-Or1-05: Updates on the conceptual design of the European DEMO superconducting magnet system

In DEMO fusion reactor the confinement of the plasma is achieved through the magnetic field generated by superconducting coils. The DEMO magnet system includes 16 Toroidal Field (TF) coils, 6 Poloidal Field (PF) coils and 5 modules for the Central Solenoid (CS) magnet. For the TF coils, four winding pack options are presented: one solution reproduces the ITER concept with radial plates, whereas the other three designs explore different winding approaches (pancakes vs. layers) without radial plates, and manufacturing techniques (react & wind vs. wind & react Nb3Sn), with the aim of improving the effectiveness of the conductors and propose cost effective solutions for the magnet system.
For the CS modules two designs have been proposed: the first is based on a pancake wound W&R Nb3Sn conductor, like in ITER. The second concept is based on a hybrid design with layer-wound sub-coils using HTS conductors in the high field section. Compared to the first option, the hybrid configuration allows keeping the same flux with reduced size or increasing the flux keeping the same size. Two different designs are also presented for the PF coils, following the concept that one solution is similar to the ITER one, whereas the second explore alternative concepts, such as the design of PF 1 and PF6 wound with Nb3Sn Cable-in-Conduit Conductors.
In order to validate the designs, thermal-hydraulic and mechanical analyses are carried out for all WPs, as well as experimental tests on full size and sub-size prototypes. Results are encouraging, with some critical aspects that shall be solved in future designs.
Finally, preliminary studies of the auxiliary systems (fast discharge units, feeders and cryogenic system), aiming to optimize the power consumption and the space allocation, are presented.

Speaker: Kamil Sedlak (EPFL Lausanne)

Sedlak_DEMO_update_MT26.pdf

Mon-Mo-Or2 - HTS Magnets I

Conveners: Hubertus Weijers (NHMFL/FSU), Satoshi Awaji (Tohoku University)

120 Mon-Mo-Or2-01: Technology for Compact CORC Multi-Layer Solenoid and Racetrack Coils

ReBCO-CORC wires, long dreamed about practical high current density thin conductors, are now reality and feature diameters in the 2 to 4 mm range. They are multi-purpose, but at CERN specifically developed for application in high-field magnets. CERN is interested to further aid the development of such conductors for possible implementation in the next generation of accelerator magnets and high-field insert coils. Therefore, a series of demonstrator coils are planned to develop and mature the technology. Here we report on two CORC based demonstrator coils currently in development.

The first is a solenoid to be used either standalone or as an insert. It aims to demonstrate the high performance of CORC wires in magnets, as well as to find critical parameters in the design and handling of both wire and magnet. The solenoid comprises two layers of 3.3 mm diameter CORC wire of each 17 turns wound on a former of 60 mm diameter. The 53 µH coil, with critical current of 9.7 kA in self-field and 4.2 K, can generate 4.5 T central field. As insert in a background of 10 T, it yields an additional 2.5 T central field. Test results at 77 K in self-field are reported followed by a test at 4.5 K during summer of 2019.

The second demonstrator magnet is a compact multi-layer racetrack coil of 190 mm long, 54 mm wide and with 20 mm head radius. It is wound with CORC wire embedding cutting-edge ReBCO tape comprising 25 µm substrate thickness. The reduction of substrate thickness from 30 to 25 µm yields a thinner and more flexible CORC wire, which is a hard requirement for this magnet. The manufacturing technology of this unique coil is reported along with its test results. More exciting new developments can be expected in the near future.

Speaker: Dr Tim Mulder (CERN)

Mon-Mo-Or2-01-Mulder-CORC Coils-MT26.pdf

Mon-Mo-Or2-01-Mulder-CORC Coils-MT26.pptx

121 Mon-Mo-Or2-02: High-field magnets wound from CORC® cables and wires

Advanced Conductor Technologies has been developing high-temperature superconducting Conductor on Round Core (CORC^®) cables and wires wound from ReBa₂Cu₃O_7-x coated conductors for use in high-field magnets. Initial development is aimed at CORC^® cable performance goals of operating currents exceeding 5-10 kA and engineering current densities (J_e) of over 600 A/mm² at 4.2 K in a background field of 20 T. Thinner CORC^® wires result in an even more flexible magnet conductor, bendable to radii of less than 25 mm, while operating at comparable currents and current densities as CORC^® cables.

CORC^® cables and wires have matured into practical magnet conductors with their initial performance goals close to being met. The next step in their development is underway, which is their incorporation into high-field demonstration magnets. Here we outline the latest results of high-field insert magnet development using CORC^® cables and wires. Several magnet programs will be discussed, including those focused on the development of high-field solenoids and accelerator magnet inserts for canted-cosine theta (CCT) and Common Coil magnets to reach a total field of 20 T when operating the CORC^® insert within a low-temperature superconducting outsert magnet. Progress in each of these magnet programs will be outlined. We will focus on the design and performance test of a CORC^® insert solenoid that is being developed to operate in a 14 T background field, while generating a field of 2 – 3 T at an operating current of 5 kA, resulting in a total field of 16 – 17 T. The 80 mm bore CORC^® insert magnet leaves room for an additional CORC^® insert that would increase the total field to 20 T.

Speaker: Jeremy Weiss (Advanced Conductor Technologies)

122 Mon-Mo-Or2-03: Critical Current and Quench Characteristics of a ReBCO 2G Roebel Cable Pancake Coil at Different Temperatures between 4.2K and 77K in an External Field up to 10T

A pancake coil was prepared with a length of 15-strand ReBCO 2G Roebel cable and studied in detail at different operating temperatures between 4.2K and 77K, cooled with either liquid cryogens or flowing liquid helium gas. The coil was impregnated with epoxy and the transient cooling was predominantly by conduction from current contacts. Critical current measurements were carried out with a transport current up to 1kA in an external axial field up to 10T. Quench measurements were carried out foloowing point-like disturbances initiated by a localised miniature heater embedded inside the coil. The different heat dissipation at the current contacts were dynamically compensated with collocated axillary heaters to ensure the isothermal condition of the coil for the successive quench episodes. Minimum quench energy (MQE) were obtained at different temperatures, fields and current load relative to the critical current. The present work is a substantive follow up of previous studies at 77K in liquid nitrogen where it has been established that the coil retained the critical current of the superconducting strand/cable and its quench behaviour was unaffected by the lateral cooling by the cryogen.

Speaker: Yifeng Yang (University of Southampton (GB))

123 Mon-Mo-Or2-04: Bi-2212 Coil Technology Development Efforts at the National High Magnetic Field Laboratory

The National High Magnetic Field Laboratory (NHMFL) is in the fortunate situation to put substantial effort into advancing all three high field magnet relevant types of high temperature superconductor (HTS) technologies, REBCO, Bi-2223, and Bi-2212, as a part of its commitment to develop all-superconducting high field magnets. Here we are presenting our work on Bi-2212 coil technology, which experienced a strong boost after significant progress was made in the heat-treatment process of the wire [1]. Bi-2212 wire has distinctive advantages compared with the other HTS conductors, as it can be made as round or aspected wire, it can be twisted, is multifilament, it can be easily cabled, it has low magnetization, and has isotropic electromagnetic properties. Operating conditions at highest fields, however, are extremely demanding on the coil mechanics and have yet to be fully explored in in HTS coils in general. Several test coils have been built and tested to evaluate various coil reinforcement schemes. In a collaboration with Lawrence Berkeley National Laboratory (LBNL), we heat treated several of Bi-2212 racetrack and CCT coils. This presentation will provide an overview and update of our on-going Bi-2212 coil R&D effort.

Acknowledgement: This work was performed at the National High Magnetic Field Laboratory, which is supported by National Science Foundation Cooperative Agreement No. DMR-1644779 and DMR-1839796, and the State of Florida, and is amplified by the U.S. Magnet Development Program (MDP).

[1] D. C. Larbalestier et al., “Isotropic round-wire multifilament cuprate superconductor for generation of magnetic fields above 30 T,” Nature Materials volume 13, pages 375–381 (2014)

Speaker: Dr Youngjae Kim (Applied Superconductivity Center, National High Magnetic Field Laboratory, Florida State University)

19-0923_MT26_Mon-Mo-Or2-04_Youngjae Kim.pdf

124 Mon-Mo-Or2-05: 25T High Field Bi-2212 Magnet Development

Two subscale coils of Bi-2212 wire have been made and tested in a DOE STTR collaboration between Cryomagnetics and the Applied Superconductivity Center at Florida State University. The coils are used to test the feasibility of using small-diameter wire in a solenoid configuration where single strand wire performance is crucial. If successful, the implementation of small-diameter wire into high field Bi-2212 HTS solenoids will allow for high J_E operation with moderate currents, making feasible the use of more modest control equipment, power supplies, and current leads. Furthermore, lower operating currents may allow series-connected design configurations with LTS background magnets, allowing for better, simpler, and more effective quench protection methods. A 25-Tesla magnet design, consisting of an 8-Tesla Bi-2212 coil with a 17-Tesla LTS coil, is underway at Cryomagnetics, and considerations of critical current, hoop stress, and quench protection will all be fully addressed.

Speaker: Dr Stephen Minter (Cryomagnetics, Inc.)

2019-09-23_25-T-Design.pdf

2019-09-23_25-T-Design.pptx

125 Mon-Mo-Or2-06: Presentation withdrawn

Mon-Mo-Or3 - Quench and Normal Zone Behavior I

Conveners: Fedor Gömöry (Institute of Electrical Engineering, Slovak Academy), Haigun Lee (Korea University)

126 Mon-Mo-Or3-01: Methods for performance diagnostics for Nb3Sn accelerator magnets in the CERN superconducting magnet test facility

Superconducting Nb3Sn accelerator magnet technology start to reach maturity and the 11 T dipole magnets based on that technology are prepared to be installed in the LHC. Performing detailed diagnostics on Nb3Sn model magnets has been vital for giving feedback on the design and fabrication of the magnets and for the conductor performance in that particular configuration. In the last few years, tens of Nb3Sn magnets have been tested in the SM18 test facility at CERN, including flat racetrack models, cosƟ dipoles, cosƟ quadrupoles, and block-coil dipoles. The large and different type of instrumentation of the model magnets allowed precise measurements of superconducting-normal transition, voltage measurements on quenching segments, mechanical transients, vibration spectra measurement with different methods. Diagnostics are completed by using quench patterns following ramp rate studies, temperature dependencies, and current cycles.
The methods to interpret and conclude on the performance of relatively large size magnets, with a relatively small amount of instrumentation are discussed using the instrumentation and diagnostic tools.

Speaker: Gerard Willering (CERN)

Mon-Mo-Or3-01-Willering.pdf

Mon-Mo-Or3-01-Willering.pptx

127 Mon-Mo-Or3-02: Overall critical current in tapes and devices made from superconductors with critical current fluctuating along the wire length

Fluctuation of critical current along the length of conductor is commonly observed in the 2nd generation of high-temperature superconductor tapes. In difference to low-temperature wires it seems that an elimination of this adverse feature is not a simple task. Then it would be sensible to incorporate its description in the standard tape characterization. We report on our effort to develop the procedure allowing to predict for such a tape the “overall critical current” at which the transition to resistive state takes place.
We started by analyzing the case of statistical Ic fluctuations defined by Gaussian and Weibull distributions. It was found that from the parameters describing these distributions (the mean and standard deviation in case of Gaussian distribution, the scale and the shape in case of Weibull distribution) one can nicely compute the current-voltage curve expected for the whole length of tape used in a superconducting device. This allows to establish the overall critical current even when the contribution to the total voltage comes only from a small portions of conductor. Main problem in application of this approach is that the data of industrially produced tapes usually do not fit perfectly any of these two distributions and then the predictions could fail. Significant difference is caused by weak points with Ic dropping outside the low end of statistical distribution. At currents well below the typical Ic value found in short sample testing, such locations are converted to hot spots with dissipation causing a catastrophic increase of temperature leading to a local damage.
Distinguishing between “statistical” and “unstatistical” Ic fluctuations is necessary because these two cases lead to very different behavior. For the tapes with fluctuations reliably described by a statistical model it makes sense to predict the overall critical current. In case of the tape with weak points the overall voltage is not representative and the dissipation at the weakest point defines the limitation for the current that could pass the whole device.

Speaker: Fedor Gömöry (Institute of Electrical Engineering, Slovak Academy of Sciences)

Gomory_Mon-Mo-Or3-02.pdf

128 Mon-Mo-Or3-03: Use of Silicon Carbide Varistors For Quench Protection of Superconducting Magnets in Cryogenic Environments

The use of silicon carbide varistors for quench protection of superconducting magnets has previously been reported [1], where the varistor unit is external to the magnet in a room temperature environment. Here it has been demonstrated that, in comparison to similar linear resistors, the varistor has beneficial effects in both limiting the magnitude of clamping voltages as well as limiting the temperature of hotspots in superconducting elements, through an accelerated discharge time.

This piece of work now considers how silicon carbide varistors may be applied to superconducting magnets, whereby the dump resistor is located inside the cryogenic system. Typical electrical characterises of the varistors at room and cryogenic conditions are presented and the benefits of using silicon carbide varistors as a replacement to traditional metallic resistors, commonly used in these applications, is then discussed. These benefits include a device with a higher failure energy (for a comparable footprint size) as well as having a preferred short circuit failure mode.

Speaker: Andrew Twin (Oxford Instruments)

129 Mon-Mo-Or3-04: Cable Quench Simulations and Current Sharing in REBCO Conductors Wound on Round Cores (CORC) for High Field Accelerator Magnet

Winding REBCO conductors on round cores (CORC) has innovatively transformed REBCO thin tapes to round cables which allow high temperature superconductor to meet low-inductance requirement and offer symmetrical electromagnetic and mechanical properties for large-scale high field accelerator magnets. HTS conductors, however, are known for slow quench propagation and large minimum quench energy, and very few quench studies have been conducted on the CORC cables. Its dynamic current sharing is largely unknown due to complex layer structure and layer-to-layer contacts. We plan to perform quench simulations of the CORC cables to achieve better understanding about transient current sharing during quenching. H formulation and T-phi formulation will be employed to model critical state magnetization in layers and A-V formulations will be used to characterize layer-to-layer current sharing behaviors and resulted Joule losses. Heaters will be imbedded into various locations inside the cable volume or on the cable outside surface. Current redistribution and normal zone propagation mechanism will be studied in addition to voltage and temperature signals. These studies will help find effective quench detection and protection for the HTS-cable based accelerator magnets.

Acknowledgment
The authors would like to thank K. Amm, R. Gupta, D. Hazelton, D. van der Laan, J. Weiss for helpful discussions and general support.

Speaker: Honghai Song (Brookhaven National Laboratory)

130 Mon-Mo-Or3-05: Quench Behaviour of Multi-Layer High Temperature Superconducting CORC Cables used in Hybrid Electric Aircraft

Hybrid electric aircraft requires high power density for power transmission, which makes the ReBCO conductor-on-round-core (CORC) cable a powerful candidate for the transmission line used in the hybrid-electric aircraft. However, quenching remains one of the biggest challenges in the development of CORC cable, for it can significantly influence the thermal stability and safety of the CORC cable. The quench behaviour of CORC cable is quite different with single tapes due to the influence of terminal joint resistance and inductance, which has to be elucidated in detail.
This work presents the results of a numerical and experimental investigation on the quench behaviours of two typical CORC cable models with multi-layer structure. Each layer of the first cable (Cable A) was consisted of only one ReBCO tape and was wound into 3 layers, while the second cable (Cable B) was a two-layer CORC cable with three ReBCO tapes in each layer. A heater was induced on the central area of the cables to generate pulses. Hotspot induced quenches were studied by calculating the current redistribution among tapes, voltage of each tape, minimum quench energy (MQE) and normal zone propagation. Influences of the inductances and terminal joint resistances on the thermal stabilities were analysed and discussed. Quench detection and protection measures were proposed.

Speaker: Zixuan Zhu

131 Mon-Mo-Or3-06: Calibration, validation and application of a novel 1D thermal-hydraulic/electric model for the quench analysis of the Al-slotted core HTS conductor for fusion applications

Numerous high current conductor designs based on High Temperature Superconducting (HTS) materials for fusion magnets have been recently proposed worldwide.
One of the most promising is the Twisted-Slotted-Core Cable-in-Conduit-Conductor comprised of an aluminum core with twisted slots in which REBCO tapes are stacked and with an external metal jacket. The coolant flows in a central hole and in lateral gaps between the stacks and the slots.
A thermal-hydraulic/electric 1D multi-region conductor model is under development to properly address the quench propagation in HTS conductors accounting for their design peculiarities.
Indeed, quench propagation in HTS materials is a well-known issue due to the low normal zone propagation velocity compared to low temperature superconductors (LTS). Since no quench tests have been carried out on HTS conductors, reliable thermal, hydraulic and electric modeling of quench propagation in such conductors is of paramount importance to assess their performance.
The direct applicability of well-known modeling tools for quench analysis in LTS conductors is questionable, due to very different materials, e.g. low and anisotropic thermal conductivity of the HTS tapes with respect to isotropic high thermal conductivity of LTS strands, as well as the different geometry, e.g. a bulky core with few twisted HTS stack compared to the ~ 1000 (<~1 mm outer diameter) LTS strands, employed in the HTS conductor design.
In order to properly calibrate the electric model free parameters, e.g., the electrical resistances between the HTS stacks and the slotted core are measured at 77 K.
After the calibration, the model is validated against electrical tests carried out on the HTS conductor equipped with superconductive stacks.
Finally, the 1D multi-region model is applied to the analysis of the quench propagation in the HTS conductor, accounting for the coolant flow in the lateral gaps and in the central hole as well as for the heat conduction in the solids and the current distribution in the current-carrying elements.

Speaker: Andrea Zappatore (Politecnico di Torino)

Mon-Mo-Or3-06_A_Zappatore_MT26_23sep2019_final_web.pdf

12:45 Lunch (on your own)

14:30 Coffee Break (during Poster Sessions)

Mon-Af-Po1.11 - HTS Magnets II

Conveners: Ernesto Bosque (National High Magnetic Field Laboratory), Yoshinori Yanagisawa (RIKEN)

132 Mon-Af-Po1.11-01 [1]: Experiment and simulation of the magnetic field produced by the HTS magnet magnetized by the flux pump

Stacks of high temperature superconducting (HTS) tapes magnetized by pulsed fields have been demonstrated a way for the development of the HTS magnet capable of trapping high field. A novel structure of the flux pump was proposed to magnetize the HTS magnet stacks of RE (RE= rare earth) Ba-Cu-O annular plates in this paper. Prototypes of the flux pump constructed of two types of the solenoidal coil with or without the iron core and pulsed triangular waveform current source were tested in the HTS magnet excitation system at 77 K (LN2 bath). The experiment and simulation analysis of the HTS magnet magnetized by two different structures of the flux pump was reported. There is good qualitative agreement between simulation and experiment. It can be noted that the induced magnetic field of the HTS magnet excited by flux pump with iron core in comparison to flux pump without iron core has considerable efficiency of generating high magnetic field.

Speaker: Xi Yuan (North China Electric Power University)

MT26-poster-Yuan Xi.pptx

133 Mon-Af-Po1.11-02 [2]: A Concentrically Arranged Joint-less HTS Coil System for Persistent Current Mode Operation

We have shown that a persistent current can be induced in HTS coils with the form of double pancakes or single solenoids by the technique of joint-less winding with 2G REBCO tapes. However, the inevitable gap located at the center of the joint-less coil caused very poor magnetic field homogeneity, which was shown by the magnetic field mapping from the previous experimental work. In this paper, to improve the performance of the coil, we proposed another HTS coil wound by the same joint-less technology but arranged differently. A conventional joint-less coil usually has two coil parts arranged coaxially, but the proposed one will have two coil parts arranged concentrically. By this arrangement, we could improve the magnetic field homogeneity by removing the unfavorable gap near the magnet center. We tried to induce the persistent current in the fabricated coil system in the operating temperature of 20 K reached by the conducting cooling system with a GM cryocooler. After maintaining the persistent current mode for 15 hours, we carried out the magnetic field mapping to analyze the harmonics of the central field under the 10-mm DSV. The analyses data will be used for the future design work of the passive shimming.

Speaker: Ms Miyeon Yoon (Korea Polytechnic University)

MT26_Jointless_Poster_v1.0.pdf

134 Mon-Af-Po1.11-03 [3]: A new way to solve the critical current degradation of YBCO coils by ice

The critical current degradation of YBCO coils have been observed in a large number of experiments, which have been explained that the thermal expansion mismatch between the YBCO tapes and resins lead to damage of the conductor. The no-insulation coil can avoid the performance degradation, but it has a poorer mechanical strength without any reinforcement. A new impregnation method by ice was introduced to the YBCO coils. This method can perfectly solve the critical current degradation of YBCO coils, and the coils also have higher mechanical strength and higher thermal stability. The impregnation process is easy and the YBCO tapes can be recycled.

Speaker: Prof. Yunfei Tan (Huazhong University of Science and Technology)

135 Mon-Af-Po1.11-04 [4]: Progress in the Development of a 25 T All Superconducting Magnet with Small-Scale YBCO Insert Coil

The 25 T all superconducting magnet designed as a combination of 14 T low temperature superconductor (LTS) background field magnet and 11 T YBCO insert coil has been developed at Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP). The electromechanical properties of YBCO coated conductors and magnetic field intensity and orientation dependence of the critical current were investigated to support the design of the insert coil. The insert coil with No-Insulation (NI) winding technique has the inner and outer diameters of 16 mm and 56 mm, respectively, and consists of ten single pancakes wound with about 240 m of YBCO conductors produced by Shanghai Superconducting Technologies Co., Ltd (SSTC). The preliminary tests were carried out at 77 K and 4.2 K in self-field. The results show that the performance of insert coil did not degrade during the manufacturing process, and it can generate a maximum central field of 15.6 T at 4.2 K, self-field. The YBCO insert coil will be tested in the 14 T LTS background field magnet in the next step to evaluate the performance in the ultrahigh magnetic fields. The latest design, construction, and preliminary test results of the YBCO insert coil will be fully introduced in this paper.

Speaker: Mr Xintao Zhang (the Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031, China, University of Science and Technology of China, Hefei 230026, China )

136 Mon-Af-Po1.11-05 [5]: Stress analysis of the 32 T superconducting magnet at the MagLab including screening current effects

The advent of REBCO tape has led to the development of tape-wound coils by a number of organizations. The 32 T magnet at the NHMFL uses two coils made of double-pancakes of REBCO installed within five LTS coils. It reached full field in December 2017. This is the highest field produced by an all-superconducting magnet to date. Since the 1970s it has been known that screening currents exist in tape-wound magnets which impact field distribution, helium consumption and stress. In recent years several groups have been computing screening currents and ac losses in REBCO tape in a variety of applications. However, there has been little published about coils of this size, particularly the stress state. This problem is very challenging due to the need to analyze 20,000 REBCO turns which are not bonded together. The T-A formulation of Maxwell’s equations employing a homogenization technique enables efficient estimation of the current distribution while structural calculations employing contact element allows estimation of stresses. Computational results are compared with test results.

Speaker: Dylan Kolb-Bond (NHMFL-FSU)

137 Mon-Af-Po1.11-06 [6]: Presentation withdrawn

138 Mon-Af-Po1.11-07 [7]: Design and experimental results of a Bi2223 superconducting magnet cooling by a free-piston Stirling cryocooler

In this article, we presented a design and experimental results of a Bi2223 superconducting magnet cooling by a free-piston stirling cryocooler. Depending on mechanics, thermal and electromagnetic multi-field couple analyzes results, we winding the coils with the type pancake type. We optimized the magnetic field by iron flange at the end of coils to avoid the vertical field effect of the Bi2223. And the coils are suspended from the room temperature vacuum vessel by six G10 suspension links. It is cooling by a stirling cryocooler with the cooling power 14W@77k,Now we finished the magnet and test it with the highest magnetic field 1T with the temperature 62K with PCS in it, the test results will be reported.

Speaker: Dr Chao Li (WST)

139 Mon-Af-Po1.11-08 [8]: Development of a Bi-2212 Solenoid Insert Coil in a 14T Superconducting Magnet

Compared to low temperature superconducting materials (LTS), Bi-2212 is more promising due to excellent current-carrying capability in ultrahigh magnetic field. In order to verify the long-line performance and small-scale superconducting magnet technology, a 2 T Wind & React Bi-2212 solenoid insert coil has been designed and fabricated at Institute of Plasma Physics, Chinese Academy of Science (ASIPP). The inner and outer diameters of the insert coil are 20mm and 32mm with 50mm height respectively. The No-Insulation (NI) winding technology is used to coil manufacture. The coil were reacted under 30 bar pressure followed the heat treatment process ordered by Northwest Institute for Non-ferrous Metal Research in China (NIN). It will generate a maximum central field of 16 T in a cold bore of 70 mm background field magnet at 4.2K. This study confirmed that present performance of the Bi-2212 round wire had satisfied the required high-field condition. This effort can also provide experience for superconducting magnet further design and experiment. This paper mainly presents the design, fabrication and pre-experiment of the insert coil, including wire specifications and heat treatment R&D, coil structure, no-insulation winding test and assessment.

Speaker: Huang Chen (Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031, China, University of Science and Technology of China, Hefei 230026, China )

140 Mon-Af-Po1.11-09 [9]: Development of Bi-2212 high temperature superconducting magnet

High temperature superconductor Bi2Sr2CaCu2O8+δ (Bi-2212) exhibits high irreversibility field Hc2 of nearly 100 T, and high critical current density under high field with the Jc of over 6800 Amm-2 under 4.2 K, 15 T. Therefore, it shows great potential in the fabrication of low temperature, high field magnet. In our institute, Bi-2212 multifilamentary round wires with length over 200 m have been successfully prepared. With our optimized high pressure sintering technique, the current capacity of obtained wires has been obviously improved. The maximum engineering critical current density of 1300 A/mm2 has been obtained under 4.2 K, 5 T and over 800A/mm2 at 12T. With these wires, we have developed a Bi-2212 high temperature superconducting magnet through the winding and reacting method. The magnet inner diameter and outer diameter are 18mm and 45 mm, respectively, and its height is 80mm. It was made from 1.0mm diameter Bi-2212 wire with the length of 110 m. The wire was insulated with TiO2 paste. After the heat treatment at 5 MPa, the critical current of the magnet reach 340 A at 4.2 K and self field. The central field is calculated to be 5 T.

Speaker: Mr Lifeng Bai (Northwest Institute for Nonferrous Metal Research)

MT26 Mon-Af-Po1.11-09 Bai Lifeng.pdf

141 Mon-Af-Po1.11-10 [10]: Screen-Current Overstressing of REBCO Coil: An Experimental and Analytical Study with Small REBCO Coils

Screening currents (SC) induced by varying magnetic fields may not only affect the field quality but also cause overstressing of REBCO coated conductor coils, making it a critical issue for NMR and other high-field magnets. We present in this paper results of an experimental and analytical study, performed with small REBCO pancake coils, on SC-overstressing of REBCO coil. Because SC is presumed to increase with REBCO tape width, we have studied test coils of two widths. The terminals of each coil, φ240 mm, were joined with a resistance sufficiently low to maintain the induced current constant enough during data taking. We use a 5-T/300-mm room-temperature bore magnet to not only supply an external field, but also induce up to 1000-A current to each coil at 4.2 K. Our experiment and analysis have demonstrated, and quantified, that the greater the REBCO tape width, the severer the SC-overstressing in REBCO coil will be.

Acknowledgement: Research reported in this publication was supported by the National Institute of General Medical Sciences of the National Institutes of Health under award number 5R01GM114834-13

Speaker: Dongkeun Park (Massachusetts Institute of Technology)

LiYi_MT-26_Mon-Af-Po1.11-10 [10].pdf

Mon-Af-Po1.12 - Losses in Conductors and Coils I

Conveners: Juan Bascuñàn (MIT), Pasquale Fabbricatore (INFN Genova)

142 Mon-Af-Po1.12-04 [11]: Presentation withdrawn

143 Mon-Af-Po1.12-05 [12]: AC loss evaluation of a novel 2G HTS narrow-stacked wires with 1 mm width

As a novel structure of second-generation high-temperature superconducting (2G HTS) tapes, narrow-stacked HTS wire with 1 mm width was proposed to reduce AC loss. Its fabricated processes are to cut the HTS tapes into 1 mm wide ones mechanically and stack them into one wire through the soldering furnace. In our previous work, compared with the traditional 5 mm wide HTS conductor, the remarkable AC loss reduction effect by narrowing the HTS tapes has been confirmed to be about 80%. Thus, the narrow-stacked wire is suitable to help the 2G HTS electrical device overcome the energy dissipation caused by AC loss. However, the effect of different HTS tapes stacking number on AC loss is not clarified in the narrow-stacked wires yet. To meet the requirement of the practical HTS applications, we evaluate AC loss of the narrow-stacked wires with different tapes stacking structure. Moreover, an HTS coil is wound with the narrow-stacked wire composed of two HTS narrow tapes and one same wide copper tape. The related AC loss analysis is carried out for further understanding the influence of tapes stacking.

Speaker: Dr Zhuyong Li (Shanghai Jiao Tong University)

144 Mon-Af-Po1.12-06 [13]: An Improved AC loss Calculation Method Based on H-formulation for HTS Magnets with Iron Core

The HTS windings in magnets can provide large current excitation in a limited space. However, under high level excitation condition, especially in the case of fast adjusting process, AC loss will occur and lead to reduction of thermal stability. The H-formulation method is widely used and basically meets the requirements of AC loss calculation for thousand-turns coil group. However, for magnets with iron core, the nonlinear saturation characteristic in ferromagnetic domains makes it difficult to calculate AC loss accurately and efficiently with traditional methods. Based on H-formulation method, we provide an improved modeling process of AC loss calculation in COMSOL Multiphysics. A sample magnet is simulated with the method and the AC loss calculation results are compared with experimental measurement results. The results show that AC loss of HTS magnets with iron core can be calculated accurately and efficiently with the improved method.

Speaker: Yu Zhang (Huazhong University of Science and Technology)

145 Mon-Af-Po1.12-07 [14]: Magnetization Loss estimation of HTS Solenoid Coils wound with striated CORC

CORC is one of the candidates for high magnetic field and large currents. We are interested in applying CORC to HTS power transformers that require not only large currents but also very low AC losses. We measured and calculated the magnetization losses of short straight CORC samples made of striated YBCO CC. The effect of the striation is certain for reducing the magnetization loss, but the effect is not directly dependent on the number of the striations and the applied field amplitude. For considering the effect in an HTS coil design, we defined striation effect factors from the measured data, and the factor used to revise the coil loss. To compare the patterns of the loss distributions in RACC and CORC coil, we also calculated the magnetization losses of an RACC coil. The RACC consists of 4 YBCO CC with the width of 4mm and the RACC coil had 22 turns in two layers.

Speaker: Mr Jisung Goo (Korea Polytechnic University)

MT26_CORC Poster_v1.0.pdf

146 Mon-Af-Po1.12-08 [15]: Numerical Modelling of Dynamic Resistance in Parallel Connected Stacks of ReBCO Tapes

Dynamic resistance refers to the emergence of a DC electrical resistance in a superconductor carrying a DC transport current that is exposed to an oscillating AC magnetic field1,2. This phenomenon arises due to the interaction between the transport current and moving fluxons in the superconductor. Quantitatively predicting the magnitude of this effect is important when designing and utilising superconducting components for power system applications, in order to appropriately manage the associated AC losses. Examples of such superconducting components include: rotor coils for high power-density motors/generators and HTS flux pumps.

Here we present 2D numerical calculations of the dynamic resistance which occurs in parallel-connected stacks of ReBCO tapes. These calculations are performed using an H-formulation finite-element model¬3. The Jc(B,θ) dependence of the tape is described by interpolating experimental data obtained across the full range of field orientation for a wide range of field amplitudes. The modelling allows investigation of parallel connected tapes in a way that is problematic experimentally due to contact resistance variability in short length stacks.

Our results indicate that the outer tapes act to shield the inner regions of the stack, with this effect becoming less pronounced as the transport current approaches the stack critical current. Current is redistributed between the tapes such that dynamic resistance is zero at applied field amplitudes less than a threshold field. Above this threshold field dynamic resistance appears simultaneously in all tapes.

References:
1. Mikitik G P and Brandt E H 2001 Phys. Rev. B 64, 092502
2. Oomen M P, Rieger J, Leghissa M, ten Haken B and ten Kate H H J 1999 Supercond. Sci. Technol. 12, 382
3. Mark D Ainslie et al 2018 Supercond. Sci. Technol. 31, 074003

Speaker: Mr Justin Brooks (Robinson Research Institute, Victoria University of Wellington)

MT26 Poster - Gus Dynamic Resistance_RAB.pdf

147 Mon-Af-Po1.12-09 [16]: Analysis of AC Loss of Annular Magnet Based on 3D Model and Reduced-Dimensional Inversion

AC loss is an unavoidable problem for a conduction-cooled HTS SMES magnet during dynamic operation, which may cause a temperature raise and affect the reliable operation of the magnet. In this paper, the 3D-model calculation method of 10MJ- annular magnet is analyzed. And then, the “Dimensionality Reduction-Inversion” method based on H-equation and homogenization modeling method is proposed, which realizes the fast calculation of AC loss of annular magnet. The accuracy and error source of the method are analyzed, which provides ideas for the calculation of AC loss of 3D superconducting magnets. In order to verify the accuracy of the "Dimension Reduction-Inversion" method, we built a small-scale annular magnet experiment platform, and measured the AC loss at 77K temperature, comparing the experimental results with the simulation results.

Speaker: Mr Shuqiang Guo

MT26海报-郭树强.pptx

148 Mon-Af-Po1.12-10 [17]: Additional AC loss properties of three-strand parallel conductors composed of Y-based superconducting tapes

Our research group have proposed the introduction of transposed parallel conductors which are generally used in conventional electric power machines and devices in order to realize a large current capacity, uniform current sharing and low AC loss. In previous studies, the additional AC loss due to the formation of the parallel conductors composed of two REBa2Cu3Oy (REBCO) superconducting tapes was investigated by pickup-coil method. In this study, three-strand parallel conductors were measured and compared with theoretical predictions. The objective of this study is to clarify the additional AC loss properties of three-strand parallel conductors composed of REBCO tapes and to prove the validity of the theoretical expressions via experiment.
The theoretical expressions of the AC loss assumed that the voltage-current characteristics are expressed by the n-value model. The samples of REBCO superconducting tapes were provided by Sumitomo Electric Industries, Ltd. The total thickness, width, critical current and n-value are 178 μm, 2.1 mm, 100 A and 25-30 at 77.3 K, respectively. The three insulated REBCO strands were co-wound into one-layer solenoidal coil. They were soldered at both ends. Three kinds of sample coils were prepared: non-transposed sample, once transposed sample and twice transposed sample.
The non-transposed sample was already measured and compared with the theoretical predictions. The observed AC loss roughly corresponded with the theoretical predictions. Furthermore, the current distribution of three-strand will be investigated using Rogowski coils.

Acknowledgement
This research was partially supported by the Japan Science and Technology: Advanced Low Carbon Technology Research and Development Program and the Japan Society for the Promotion of Scienve: Grant-in-Aid-for Scientific Research (JP18H03783 and JP17H06931).

Speaker: Takuma Furukawa (Kyushu University)

2019MT_3.pdf

149 Mon-Af-Po1.12-11[18]: Presentation withdrawn

150 Mon-Af-Po1.12-12 [19]: Numerical Study on AC Loss of the HTS Coil with distorted AC Transport Current around Laminated Silicon Steel Sheets

AC loss is an intractable and inevitable issue on high temperature superconducting (HTS) coils and magnets. The HTS coils used in HTS applications will suffer from distorted currents when operate in malfunction. Based on this, AC loss of the double-layer racetrack coil (DRC) carrying harmonic contents in phase or out of phase has been measured with laminated silicon steel sheets (SSS) or not. To a first approximation, the experimental data agree with the simulated results and give corresponding explanations. The influence of different harmonic currents on AC loss has been analyzed and has found that the 3rd harmonic in phase increases the loss at most and reaches up to 9.3% compared to that of the fundamental waveform. Two methods are proposed to reduce AC loss of the DRC around SSS. It is significant and straightforward that the reduction ratio of AC loss can attain 20.7% and 18.0% respectively by enlarging L and d 5 mm.
Index Terms—Double racetrack coil, silicon steel sheets, distorted currents, AC loss.

Speaker: Xiaoyong Xu (Shanghai Jiao Tong University)

post-Mon-Af-Po1.12-12.pdf

post-Mon-Af-Po1.12-12.ppt

Mon-Af-Po1.13 - Magnets for NMR

Conveners: Hubertus Weijers (NHMFL/FSU), Yoshinori Yanagisawa (RIKEN)

151 Mon-Af-Po1.13-01 [20 & 21] [Invited]: Towards a 1.3 GHz (30.5 T) NMR: Persistent-mode NMR magnet with superconducting joints between high-temperature superconductors

We will describe the first persistent-mode medium magnetic field (400 MHz, 9.39 T) NMR magnet which uses superconducting joints between high-temperature superconductors (HTSs). As an ultimate goal, we aim to develop a high-resolution 1.3 GHz (30.5 T) NMR magnet operated in the persistent-mode [1]. The 1.3 GHz NMR magnet requires superconducting joints between HTSs and those between an HTS and a low-temperature superconductor (LTS). Towards this goal, we have been developing persistent-mode HTS inner coils to be operated in a 400 MHz (9.39 T) NMR magnet, and here we present the first prototype of an inner coil wound with a single piece REBCO conductor [2]. The coil and a newly developed REBCO persistent current switch (PCS) are connected with intermediate grown superconducting (iGS) joints which can transport very high currents in external magnetic fields. To evaluate the performance of the joints with an ultimately stable and homogeneous magnetic field in a real magnet system, the coil is operated in the persistent-mode, generating 0.1 T, in a 9.3 T background magnetic field of a persistent-mode LTS outer coil. A magnetic field drift rate of this 400 MHz LTS/REBCO NMR magnet is <1 ppb/h, sufficient to obtain high-resolution NMR spectra. The 1H NMR spectrum line shape gives a half height width of 1 ppb, demonstrating that the superconducting joints perfectly functions in a high-resolution NMR system. As the next development steps, we will develop a REBCO inner coil with many joints and a Bi-2223 inner coil, which coils will also be tested in the 400 MHz LTS/HTS NMR magnet in the persistent-mode.

[1] Maeda et al, submitted to IEEE TAS
[2] Yanagisawa et al, Presented at ASC2018, 4LPo1E-05

Acknowledgements:
This work is supported by the JST-Mirai Program Grant Number JPMJMI17A2.

Speaker: Yoshinori Yanagisawa (RIKEN)

MT26_Mon-Af-Po1.13-01 [20-21]_yanagisawa.pdf

152 Mon-Af-Po1.13-02 [22]: Reaching Field Uniformity of One Part Per Billion and Below

High magnetic field uniformity is important for various applications, including NMR, MRI and quantum computing. A novel scheme has been developed to significantly improve magnetic field uniformity in a good field region, defined by (Bmax-Bmin)/Bmin, to levels well below 1X10-6 limit achievable in modern NMR and MRI magnets with shimming. This novel scheme can achieve theoretical field uniformity of 1x10-11 in a good-field-region as proven by semi-analytic calculations. The proposed scheme has a main coil that generates a high- uniformity main field, correction coils and permanent magnet arrays a two-step correction procedure to successively reduce field errors. The main coil is a discretized wire-wound spherical coil with optimized winding pitch between adjacent conductors. Assuming conservative manufacturing tolerances a field uniformity of parts per million (1X10-6) is feasible without shimming ofthe main coil. The two-step correction procedure uses a novel field decomposition technique, based on 3D cylindrical multipole description of measured magnetic field along two orthogonal axes, which allows identification and systematic correction of field errors. The first correction step uses correction coils of appropriate multipole order and with high field uniformity to correct the main field error by one or two orders of magnitude. Persistent mode superconducting magnets are needed for the main coil and correction coils to achieve sufficient temporal stability. In the second step further improvements in field uniformity are achieved using permanent magnet arrays that constitute crude Halbach arrays of given multipole order. State-of-the-art NMR field mappers with accuracy of 1X10-9 can be used for shimming of magnets with flux densities in the Tesla range. Additionally, another variation of this novel scheme is presented that enables shimming of parts per billion with peak field levels of mTesla and below.

Speaker: Dr Rainer Meinke (AML)

153 Mon-Af-Po1.13-03 [23]: Ultra-high field NMR superconducting magnet design with conduction-cooled cryostat system

A portable nuclear magnetic resonance (NMR) superconducting magnet with conduction-cooled cryostat system was under development with central field strength 7 T. The designed diameter of spherical volume (DSV) of the magnet is 0.05 m and the peak-peak homogeneity is 8 ppm. After shimming, the field homogeneity will be improved to 0.1 ppm over a DSV 0.01 m. The magnet is actively-shielded with a 5 Gauss line 0.65 m at the longitudinal direction and 0.40 m at the radial direction. The magnet coils have a diameter 0.27 m and length 0.36 m. The fabricated magnet will have a standard warm bore diameter 0.054 m.
The magnet design was based on NbTi superconducting wire, which consumes wire length 16.6 km and wire volume 0.005 m3. There are 12 magnet coils in total including 5 primary coils, 4 compensating coils and 3 shielding coils and superconducting wires with several gauges were applied to reduce the integral wire usage. The operating current for the target field strength is 110.59 A, accompanying a maximum hoop stress 122 MPa. The current margin and temperature margin for the magnet are 78.1% and 1.49 K at 4.2 K, respectively. The coil inductance is 14.8 H and the magnetic energy is 90.6 MJ.
Four bobbins were designed for the magnet coils support and another one between the compensating coils and shielding coils was used for shim coils attachment. The cold heads of cryocooler were mounted on the metal bobbins, which cooled the magnet coils temperature much lower than critical temperature.
The conduction-cooled NMR magnet largely reduced the dependence of superconducting magnet on liquid helium, which not only well copes with the scarcity of liquid helium market in the future, but also reduce the overall cost of the magnet system in a long run.

Speaker: Dr Yaohui Wang (Institute of Electrical Engineering, Chinese Academy of Sciences)

MT_yaohui wang-2.pdf

154 Mon-Af-Po1.13-04 [24]: Design and Analysis of a Multi-Bore NMR Magnet Array

In this paper, we propose a new concept of “multi-bore” NMR (nuclear magnetic resonance) magnet, where multiple high temperature superconductor (HTS) NNR magnets are closely positioned to form a magnet array. A key benefit of the multi-bore NMR system over its single-bore counterpart may be that it shares some common parts, especially cryogenic system and current lead, thus the overall multi-bore NMR system could be substantially more compact than the same number of single-bore NMR systems. However, due to the close positioning of multiple HTS NMR magnets, the electromagnetic interference among neighbor magnets may be significant, which leads to challenges in: (1) obtaining NMR quality field uniformity; (2) keeping sustainable electromagnetic force and stress; and (3) safe quench protection. This paper presents our initial design of a 4-by-4 multi-bore NMR magnet array. Then, a set of ferro-shims is designed to obtain a target field uniformity for all magnet components. The unbalanced Lorentz force on each magnet is also calculated with a first-cut design of the support structure. Finally, a post-quench analysis is performed with mutual inductances among magnets taken into consideration.

Keywords: Array of magnets, field uniformity, HTS magnet, multi-bore NMR
Category: D01 - Magnets for NMR

Acknowledgement
This work was supported by the Korea Basic Science Institute (KBSI) grant D39611. It was also partly supported by the National Research Foundation of Korea as a part of Mid-Career Research Program (No. 2018R1A2B3009249).

Speaker: Mr Jaemin Kim (Seoul National University)

155 Mon-Af-Po1.13-05 [25]: Design Methodology for Ferromagnetic Shimming of HTS NMR Magnets Using a Stacked Multilayer Shim

In this paper, a new design method using a stacked multilayer ferromagnetic shim is proposed and experimentally verified. Because of large harmonic errors caused by the screening-current induced magnetic field (SCF) and absence of superconducting active shim coils, ferromagnetic shimming is one of the most important technologies to develop the homogeneous high temperature superconducting (HTS) NMR magnets. In conventional designs of ferromagnetic shim, it has been important to optimize the thickness of hundreds of shim elements. Since the optimal thickness combination can be very complex, 0.025 mm (1 mil) to 0.5 mm (20 mils) thick, a method to reduce manufacturing errors should be considered from the design stage. Even if the shim of the complex combination is well fabricated, the performance may not be perfect, so that the shimming is iterative process. In order to reduce the manufacturing errors of the shim layer and flatten the contact section when stacking, each shim set is designed with shim elements of the same thickness. In this paper, the design method to reach 1 ppm with ferromagnetic shim alone and the process of installing multilayer shim are explained. The newly designed shim has been fabricated and verified by the shimming test of a 400 MHz all-ReBCO NMR magnet, which is supposed to have the final homogeneity level of sub-ppm, including room-temperature (RT) shims.

Speaker: Mr Hongmin Yang (Kunsan National University)

156 Mon-Af-Po1.13-06 [26]:A Novel and Fast Method for Inductance and Force Calculation of Multi-Coaxial Coils for NMR Magnet Design

In the ultra-high field NMR (nuclear magnetic resonance) and MRI (magnetic resonance imaging) application with using high-temperature superconducting (HTS) materials, the elaborate analysis of multiple coaxial solenoid coils is essential for the magnet design. The inductance and force were calculated by some authors using analytical and semi-analytical expressions based on double integrations or elliptical integrals of the first and second kinds, Heuman’s Lambda function. In this study, we present new and fast procedures for calculating inductance and force exerted between coaxial coils. The combination of Biot-Savart law and Numerical method are used to calculate magnetic field at the interesting area, the inductance is the flux linkage surface integral over the cross section and the force is the Lorentz force volume integral over the solenoid in the cylindrical coordinate system. The derived inductance and force formula based on double integral can be implemented respectively by MATLAB programming with no concern of singularity. Compared with the traditional method, in the MIT 1-GHz NMR magnet design, the inductance and force calculation results respectively differ by less than 8 ‰ and 1 ‰ when the coil distance is 0.26mm. With the increase of the distance, the minimum differences are 7.0×10-3 ‰ and 4.8×10-3 ‰. The suggested method calculation time is 2 times faster in the meantime. The presented approach is more general for calculating the inductance and force of coaxial coils and more applicable to get highly accurate results caused by a relatively simple procedure and shows low computational time.

This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (No. 2017R1A2B3012208) and Research reported in this publication was supported by the National Institute of General Medical Sciences of the National Institutes of Health under award number R21GM129688.

Speaker: Mr Quanyue Liu (Uiduk University, Gyeongju, Republic of Korea)

MT26-Mon-Af-Po1.13-06 [26].pdf

Mon-Af-Po1.14 - Electrical Insulation for Magnets

Level 2 Posters 1

Conveners: Andries den Ouden (Radboud University), chao li (University of Cambridge)

157 Mon-Af-Po1.14-01 [27]: A Study on the Dielectric Characteristics of Epoxy Resin according to Surface Roughness

A joint method for enlarging the length of a superconducting coil should be developed in order to cope with the power demand of industrial society. There are many kinds of joint methods are proposed to enlarge the length of a superconducting coil with high electrical reliability. Among them, a stop joint box method is known as the most promising method to enlarge the length of a superconducting coil because the pressure of a superconducting coil system keep constant with a stop joint box method. However, electrical breakdown could occur because of the vulnerable dielectric characteristics at surface between epoxy resin and polypropylene laminated paper (PPLP) in the stop joint box method. It is well known that the dielectric characteristics of surface between two solid insulation materials are inferior to those of a liquid or a solid insulation material. Therefore, creepage discharge characteristics of surface between epoxy resin and PPLP should be performed according to surface roughness. In this study, experiments on dielectric characteristics of a stop joint box method are performed according to pressure and roughness. It is found that the dielectric characteristics of a stop joint box method are dependent on the roughness of solid materials.

Speaker: Minkyung Jeong (Korea National University of Transportation)

Mon-Af-Po1.14-01.pdf

158 Mon-Af-Po1.14-02 [28]: Transient Voltage Analysis of Air-Core Coils with Large Section

With the rise of power level of high power device like magnetic power supply systems of fusion device, the section size of smoothing and current-limiting reactor becomes larger and larger. To keep the linearity of inductance, the structure of air-core with vacuum pressure impregnation (VPI) casting is widely used. In this paper, a numerical method based on equivalent model is adopted to study the transient voltage process of air-core coil under the overvoltage excitation, focusing on the effect of dielectric constant, thickness of insulating medium, number of coil layers on the resonance frequency and voltage distribution of various layers. To verify the numerical analysis results from MATBLE and ATP-EMTP, multi-group and various coils prototype like single layer with resin, single layer without resin and so on are fabricated and tested, which demonstrated the accuracy of proposed analysis method. In addition, the research results can provide a reference of the insulation design and fabrication of large current coils with large section.

Speakers: Dr Chuan Li (Huazhong University of Science and Technology, Wuhan, 430074, China), Mr Chengjin Qian ( Huazhong University of Science and Technology, Wuhan, 430074, China), Dr Jiawei Li (Huazhong University of Science and Technology, Wuhan, 430074, China), Dr Pengyu Wang (Huazhong University of Science and Technology, Wuhan, 430074, China)

159 Mon-Af-Po1.14-03 [29]: New types of organic resins for insulation of warm magnets

Two types of new organic resins are under development at KEK for the magnet insulation materials. One is Cynate ester resins which will be used in warm magnet insulation instead of usual epoxy resins. One of its typical (possible) characteristics is its radiation hardness. We have already developed a new type of the insulation resin based on Bismaleimide-Triazine （BT) resin.　　BT resin was widely used for high intensity accelerators because of its one order of magnitude higher radiation hardness than normal epoxy resins. Especially, most magnets of J-PARC, Japanese high intensity proton accelerator complex, were assembled with the BT resin. However some thermal characteristics of the BT resin is somewhat too keen with its curing temperature to be handled by easy manner. Then we found some possibility to realize the easy-manner handling characteristics in Cynate ester resins. Some parts of the R&D works are now under progress at KEK and at several chemical collaborating companies in Japan. We will be able to report the latest status of this R&D works at MT26.
Another trial is under progress with resins which are hardened by Ultra Violet light. Then the resin is called as "UV-resin". This UV resin can be very smooth liquid in normal room temperature. However the resin will be hardened quickly under the irradiation of UV-light, which can be found in natural light from the sun and from light source assembled with UV-light LED, etc. Thus their very important characteristics is its rapidness to be hardened. Some UV-resin will be hardened within several second from smooth liquid by the irradiation of UV-LED light. This phenomenon will help us to assemble warm magnet coils with very much complicated shape. Possible problems are its mechanical strength and radiation hardness. At present R&D of the UV-resin has just started and we will be able to report some progress at MT26.

Speaker: Prof. Kazuhiro Tanaka (KEK, High Energy Accelerator Research Organization)

CyanateResinSmall.pdf

160 Mon-Af-Po1.14-04 [30]: Mechanical characterisation of Nb3Sn cable insulation systems at ambient and cryogenic temperature used for HL-LHC accelerator magnets.

The insulation system is a key component of Nb3Sn superconducting accelerator magnets under construction for the LHC High Luminosity upgrade (HL-LHC). It needs to ensure the magnet operation at 1.9 K and to guarantee the functionality during the complete service life of the magnet in the accelerator under high mechanical stress and irradiation dose up to 35 MGy. A first set of experimental tests have been performed at room and cryogenic temperature to confirm the stress-strain behaviour, the mechanical strength and the failure mechanisms of the cable insulation system used for the HL-LHC Nb3Sn accelerator magnets. CERN is performing tensile and inter laminar shear strength (ILSS) tests and a non-standardized combined compressive shear test, which is more representative for magnets operational conditions. The tested samples consists of the same raw insulation material and follow similar specific manufacturing procedures as the ones of the 11 T Nb3Sn dipole and the MQXF Nb3Sn quadrupole magnets. In order to represent the different design criteria of these magnets, the sensitivity to the mechanical behaviour of the CTD-101K resin impregnated samples to a varying S2-glass yarn density, sizing and fibre volume fraction was investigated with different types of samples as well as the effect of mica used in the insulation system.

Speaker: Arnaud Pascal Foussat (CERN)

MT2019_poster_Wolf_Mon_Af-Po1.14-04.pdf

161 Mon-Af-Po1.14-05 [31]: A Study on Improving the Electrical Stability of a High Voltage Superconducting Magnet

A study on the cryogenic dielectric characteristics for developing a high voltage superconducting magnet system such as a superconducting fault current limiter, a superconducting transformer, and a superconducting cable has been performed. A high voltage superconducting magnet system uses liquid nitrogen as an insulating medium as well as a cooling medium by immersing a superconducting magnet into liquid nitrogen and uses gaseous nitrogen as an insulating medium by pressurizing. In many cases, electrical breakdown occurs frequently where a current lead and an enclosure meet due to the vulnerable dielectric characteristics of gaseous nitrogen compared with those of liquid nitrogen. In this study, the dielectric characteristics of gaseous nitrogen according to the work function of materials is performed and a new method for enhancing the dielectric characteristics of a high voltage superconducting magnet system is proposed. As a result, it is found that the probability of electrical breakdown at the dielectric weak point of a high voltage superconducting magnet system could be enhanced by adopting the proposed method.

Speaker: Ms Onyou Lee (Korea National University of Transportation)

162 Mon-Af-Po1.14-06 [32]: A clean production line for conductors insulation preparation

The construction of high-performing magnets has to take into account the mechanical properties of the employed materials, and insulation adhesion to the conductor is one of the key factors. ICAS, the Italian Consortium for Applied Superconductivity, after an R&D phase, set up a new production line to process copper conductors in order to prepare, apply and cure a cyanate ester based primer, CTD-450, developed by Composite Technology Development, to improve the adhesion of fiberglass epoxy resin insulation to copper. With this new semi-automatic line, a total of about 1.5 km of conductors were treated successfully in a complete temperature and moisture controlled clean environment. In order to mitigate the risk of contamination prior to curing, the whole workshop was constantly kept in overpressure and the whole line was designed to employ only non-contaminating materials. This paper offers an overview of ICAS' technical capabilities and what was learned in terms of key parameters and quality controls.

Speaker: Luigi Muzzi (ENEA)

MT-26_PRIMING_FQT_Rev3.pdf

163 Mon-Af-Po1.14-07 [33]: Partial Discharge Characteristics and Endurance Under Repetitive Square Wave Voltage for PI firm Used in Inverter-fed HTS Motors in Liquid Nitrogen

Abstract-High-temperature superconductors motors driven by power electronics or its startup requires an insulation system which prevents pulse voltage in Liquid Nitrogen.Materials like polyimide(PI) or fiber reinforced plastic materials are usually used in insulation system because of its high performance.Due to driven by power electrics,repetitive square wave voltage(RSWV) will be more appropriate than sinusoidal wave.So this paper presents characteristic of partial discharge(PD) of coil used Kapton under RSWV in liquid nitrogen(LN2).RSWV which has different parameters such as rise/fall time,frequency and duty cycle will significantly influence PD characteristics.Therefore,each condition will be measured by five same samples and same parameters of RSWV except rise time.The results,experimental site and more details will be introduced.
Index Term-insulation partial discharge repetitive square wave voltage liquid nitrogen

Speaker: Wei Wang (Sichuan University)

Poster A0 Zyt.pdf

Mon-Af-Po1.15 - Multiphysics Design and Analysis II

Conveners: Prof. Kozo Osamura (Research Institute for Applied Sciences), William Marshall (National High Magnetic Field Laboratory)

164 Mon-Af-Po1.15-01 [34]: PITHIA: An innovative BEM/FEM simulation software for field calculations of accelerator magnets

PITHIA is an advanced simulation tool, in-house developed by FEAC Engineering P.C., with currently three available modules for electromagnetic, cathodic protection and fluid-structure interaction problems (either 2D or 3D), which can effectively treat large-scale problems as well. This paper describes PITHIA’s electromagnetic module, focusing on applications such as superconducting accelerator magnets. Its capability in solving large-scale linear and non-linear magnetostatic problems to create digital twins of superconducting magnets is being further developed and validated, in the frame of the “KR3870/KT/IT/018L know how & consultancy agreement" with CERN amongst others. The software’s capabilities are characterized by accurate field calculations and modelling of arbitrarily complex coil geometry. The electromagnetic module of PITHIA is based on a coupled FEM/BEM scalar potential formulation that exploits both the advantage of BEM to treat infinite domains and the advantage of FEM to treat nonlinear problems. The numerical results of different types of accelerator magnets simulated with PITHIA are presented in this paper and compared with corresponding results obtained by other commercial simulation software in terms of accuracy and efficiency.

Speaker: Dr Dimitrios Rodopoulos (FEAC Engineering P.C. & University of Patras)

165 Mon-Af-Po1.15-02 [35]: An electric-circuit model on the inter-tape contact resistance and current sharing for REBCO cable and magnet applications

Several investigations have shown that ReBCO coils wound without turn-to-turn insulation are self-quench protecting due to the current bypass through layers. However, some of the obstacles that this type of magnets face are charging and discharging delays, directly related to the generation of eddy currents increased by the low contact resistance between turns. The inter-tape contact resistance plays a key role to address the disadvantages that no insulation brings to magnet performance and benefit from the current sharing feature. In this work we propose an electric-circuit model to describe the inter-tape contact resistance and its impact on the current sharing between tapes for REBCO cables and magnets. With the developed model, we present the ideal contact resistance that can suppress the inter-tape eddy currents and enhance the current sharing between tapes. We also report quench experiments on short REBCO tapes to validate the model. Our model is expected to provide insight into the current sharing and target values for inter-tape contact resistance in REBCO cables and magnets for various applications.

Speaker: Aurora Cecilia Araujo Martinez (Universidad de Guanajuato)

ACAM_poster.pdf

166 Mon-Af-Po1.15-03 [36]: Magnetic Properties Measurement and Analysis of High Frequency Core Material Considering Temperature Effect

Electrical equipment is tending to miniaturization and high frequency in modern industry development. High frequency transformer (HFT) has a broad application prospects whose volume obeys the law of inverse-squares of the operating frequency. Magnetic properties of its core materials under actual conditions need to be studied.
The soft magnetic ferrites, amorphous and nanocrystalline alloys are usually used to the core of HFT. High running frequency can also lead to the increase of power loss in the magnetic cores and windings, which will cause the temperature rise. Magnetic properties of the core materials measured in laboratory at room temperature cannot meet the requirement of performance analysis and loss evaluation of HFT. Therefore, it is necessary to do further research on the magnetic properties and loss properties of high frequency core materials at different temperatures.
In this paper, a testing system for ring sample is designed considering the influence of temperature. Magnetic properties of the ferrite (N87), nanocrystalline (1k107B) and amorphous alloys (1k101) are measured in the range of 25 °C to 120 °C from 1 kHz to 20 kHz. The saturation flux density, coercive force, remanence, permeability and loss properties of the above materials at different temperatures are analyzed and the change regularities are summarized. The temperature dependencies of three materials under different conditions are compared by using the coefficient of loss variation. At the specific flux density, the loss variation with temperature of 1k101 is the least, 1k107B is the slightly worse than 1k101, and the loss variation with temperature dependence of ferrite is the largest. With the increase of frequency, the loss variation of 1k107B with temperature decreases and their temperature stability is better than the other two materials. Meanwhile, the conductivity of material at different temperatures is measured and analyzed by using van der Pauw method. The overall performances of core materials are summarized in combination with the experimental phenomena and three materials are evaluated objectively.

Speaker: Yongjian Li (Hebei University of Technology)

Mon-Af-Po1.15-03 [36] Magnetic Properties Measurement and Analysis of High Frequency Core Material Considering Temperature Effect.pdf

167 Mon-Af-Po1.15-04 [37]: Numerical Analysis of a fully HTS Magnetic Bearing Under High-speed Operation

The superconducting magnetic bearing (SMB) has great application potential in flywheel energy storage system (FESS), because of the merits of wear-free, low-drag torque, self-stable, unlubricated and vacuum-compatible operation. A fully high-Tc superconducting (HTS) FESS with a 300 kW power has been established in Japan, 2015. The next generation MW-class FESS needs a larger weight and higher-speed rotor, therefore, the fully high-Tc SMB composed of the HTS coils and HTS bulks is the best choice. This fully SMB should have a flywheel rotor of over a ton-class weight with thousands-of-round-class per minute. Accordingly, both the mechanical and thermal stabilities of stator of HTS coils and rotor of HTS bulks are critical issues in engineering application. In the present work, a two-dimensional (2-D) finite-element model of the fully SMB based on H-formulation and a nonlinear constitutive relationship was built and calculated by finite-element method. The dynamic, electromagnetic and thermal characteristics in the rotor of HTS bulk and stator of HTS coated conductor coils were calculated and discussed systematically, when the rotor of HTS bulks operates under different speeds from hundreds to thousands of rpm. An overall picture were build to show the mechanical, electromagnetic and thermal stabilities of this SMB, especially the heat loss and speed degradation in superconductors. Based on this prognostic work, several operable rules are provided for the design and operation of SMB.

Acknowledgement
This work was supported in part by the National Natural Science Foundation of China under Grants 51475389, 51722706 and 51707164, in part by China Postdoctoral Science Foundation under Grant 2017M623055, and in part by the Sichuan Youth Science & Technology Foundation under Grant 2016JQ0003.

Speakers: Dr Changqing Ye (Hohai University), Guangtong Ma (Southwest Jiaotong University)

168 Mon-Af-Po1.15-06 [38]: Expansion of the magnetic field in toroidal harmonics and correlations with the current distribution

Toroidal magnets are widely exploited in industry and scientific research, involving a vast spectrum of applications, such as thermonuclear fusion, particle detectors, SMES systems and medical devices. Toroidal configurations may involve different number of coils of different planar and three-dimensional geometries; to properly analyse these systems, it is crucial to determine the magnetic field generated by various configurations.
The multipole expansion theory in the complex plane is widely adopted to describe the magnetic field of particle accelerator magnets with straight axis. The main advantage of this analytical description is the possibility of identifying multipolar field components of the magnetic system and use them to predict the interaction of a charged particle beam with the field itself. In this case, the correlation between current distribution and field harmonics is well known.
The multipole expansion theory can also be applied to the analysis of toroidal configurations, by solving the Laplace equation for the magnetic scalar potential in toroidal coordinates. In this case however, the correlation between the current distribution and the field harmonics cannot easily be identified.
This paper proposes a methodology for the determination of the field harmonics in toroidal coordinates. The starting point of the model is the calculation of the magnetic scalar potential, based on a hybrid analytical-numerical approach, which was validated versus well-established software for electromagnetic calculations.
The developed algorithm was applied to explore the correlation between the shape and number of coils disposed along the torus and the multipolar components generated by the magnetic system. A specific focus on non-planar configurations and corrector coils is presented, reporting the effect on the field harmonics of various geometric solutions.

Speaker: Prof. Marco Breschi (University of Bologna)

MT_26_field_harmonics.pdf

169 Mon-Af-Po1.15-07 [39]: Numerical investigation on the thermo-electro-mechanical behavior of HTS tapes

High temperature superconducting (HTS) materials are nowadays considered as possible candidates for high field magnets, e.g. for fusion and high-energy physics, and for AC or DC power applications. The development of HTS conductors requires extensive information about the impact of the main characteristics of the cable architecture on the electrical performances of the superconducting tapes or wires. In particular, for a proper conductor design, it is important to characterize the bending behavior of the tape.
In this work, a detailed finite element (FE) model is used to investigate the thermo-electro-mechanical behavior of a commercial (Re)BCO tape from Superpower. A measurement procedure to determine the critical current of the tape when wound helically around cylindrical mandrels of different diameters is simulated. This tape configuration can be found in conductor on round core (CORC®) cables as well as in many types of conductors for power applications.
As a first step, the cooldown to cryogenic operating conditions is fully analyzed, thus computing the strain field corresponding to the first critical current measurements performed on the straight sample. After that, the heating up to room temperature, the helical winding and the following new cooldown is modeled to obtain the final strain map in the tape. This complete analysis is repeated for different mandrel diameters and helix pitches. The numerical results are finally compared to the outcomes of experimental tests performed at 77 K.
The combination of thermal contraction effects and bending/twisting loads due to helical winding is simulated with a fully coupled approach and temperature dependent mechanical properties for HTS tapes. The experimental and numerical results presented in the paper give a better insight to the distribution of 3D thermo-mechanical strain components inside the tapes and their impact on the conductor electrical performance.

Speaker: Prof. Daniela Boso (University of Padova)

MT_26_double_bending.pdf

170 Mon-Af-Po1.15-08 [40]: Critical Temperature Prediction for a Superconductor: A Bayesian Neural Network Approach

Recently, there have been a number of studies using empirical machine learning approaches to extract useful insights on the structure-property relationships of superconductor material. Especially, these approaches are bringing extreme benefits when superconductivity data often come from costly and arduously experimental work. However, this assessment cannot be based solely on an open “black box” machine learning model, which is not fully interpretable, because it can be counter-intuitive to understand why the model gives a particular response to a set of data inputs for superconductivity characteristic analyses e.g. critical temperature, critical current density, and critical fields. This paper aims to present an alternative approach for predicting the superconducting transition temperature Tc from SuperCon database obtained by Japan’s National Institute for Materials Science. We address an explainable and reliable machine-learning framework called Bayesian neural network using superconductor’s chemical elements and formula to predict Tc. In such a context, the importance of the paper in focus is twofold. First, to improve the interpretability, we use a generative statistical model to capture the mutual correlation of superconductor compounds. Finally, Bayesian optimization is utilized to search for the optimal parameters of Bayesian neural network for an improved performance of the prediction model.

Speakers: Thanh Dung Le (École de technologie supérieure), Huu Luong Quach (Jeju National University)

MT26_Mon-Af-Po1.15-08 [40].pdf

171 Mon-Af-Po1.15-10 [41]: Presentation withdrawn

172 Mon-Af-Po1.15-11 [42]: The design of transcranial magnetic stimulation thin core coil based on multi-objective optimization

Transcranial magnetic stimulation(TMS), as a new medical technology with great development prospect, has been shown to be effective in treating a variety of mental illnesses. The stimulation intensity and focality of the transcranial magnetic coil are often used to measure its biological effects. In order to improve its performance, a magnetic core can be added to the existing coil to enhance the local magnetic permeability. However, the eddy current loss in the core generated by the high-frequency alternating magnetic field cannot be ignored. Thus, this paper proposes a design scheme of transcranial magnetic stimulation thin core coil based on multi-objective optimization. Firstly, the core material suitable for high frequency alternating magnetic field is selected to improve the overall performance. Secondly, several groups of core placements and geometric sizes, which are used as decision variables, are designed using the exhaustive method. Then the corresponding induced electric field intensity, focality as well as the core coil heat can be calculated using the finite element method. Taking reducing the heat of the core and improving the intensity of the induced electric field as well as the focality of the coil as multiple optimization objectives, the final optimization model can be established after normalizing the above-mentioned objectives. At last, the optimal core placement and the geometric size can be obtained accordingly. In the case study, the stimulation effects are analyzed and compared. Under the same power output condition, results show that the proposed core coil can increase the intensity by 80% and the focality by 20% compared with the figure of eight coil. Compared with the existing core coil, it can reduce the heat by 50% with better intensity and focality.

Speaker: Dr Chang Liu (Huazhong University of Science and Technology)

Mon-Af-Po1.15-11 [42] 刘畅.pdf

Mon-Af-Po1.15-11 [42] 刘畅.pptx

173 Mon-Af-Po1.15-12 [43]: Design and Quench Analysis Study on a 9 T NbTi Superconducting Magnet for Large Bore EMPS

A 9 T NbTi superconducting magnet with large bore is designed and will be fabricated for EMPS (Electro-Magnetic Property measurement System) whose sample space is 50 mm in diameter. To satisfy the large sample space of the system, winding bore of the magnet should be larger than 100 mm in diameter. Since the winding diameter is larger than that of conventional 9 T class NbTi superconducting magnets, wire selection and magnet design are very important and difficult in this research. Optimal design with genetic algorithm considering critical current, magnetic stress, thermal stability and field uniformity is carried out to develop 9 T large bore NbTi EMPS magnet. The design algorithm calculates the structure and dimensions of the magnet to minimize the total volume with satisfying the constraints related to the stability of the magnet. The magnet is composed of series connected three coaxial NbTi coils, of which the wire diameters are different. To evaluate thermal stability of the magnet, quench analysis is also implemented considering the two boundaries among adjacent three coaxial NbTi coils. The maximum hot spot temperature of the magnet is calculated based on the quench analysis model and the fabrication of the 9 T large bore NbTi magnet will be performed after design optimization.

Speaker: Jae young Jang (Korea Basic Science Institute)

Mon-Af-Po1.16 - Quench Protection and Detection Systems II

Conveners: Mr Etienne Rochepault (CEA Paris-Saclay), Dr Minfeng Xu (GE Global Research)

174 Mon-Af-Po1.16-01 [44]: Design of a quench detection system by implementing an optimization procedure

ENEA is currently working on the design of an experimental fusion reactor named DTT (Divertor Test Tokamak).
DTT magnetic system will be realized using superconductor materials thus implying the need for specific protection strategies. In particular, in case of magnet quench, detection and protection devices are needed and they represent a significant cost. The design of quench protection circuits should take into account reliability requirements and also possible protection circuit failures.
To the aim of design purposes, it is fundamental to evaluate all possible failure scenarios in order to identify the most critical conditions. Failure scenarios analysis is a typical problem involving the detection of an extreme condition which is suitable to be solved using parametric optimization algorithms.
From the point of view of magnetic couplings, the quench protection system may be thought as composed of two subsystems: 1) the Central Solenoid (CS), Poloidal Field coils (PF) and Plasma; 2) Toroidal Field coils (TF).
Both the magnetic subsystems include the possibility of timely Fast Discharge Units (FDU) in order to discharge the energy stored into the superconducting coil in case of quench detection. Each unit includes proper breaker circuit with discharge resistor banks in parallel. When the quench is detected, the current carried out by the circuit breaker is commutated into the discharge resistor, and the superconducting coil energy is dissipated with the circuit time constant. Therefore, these resistor banks are designed to fulfill the requirements in terms of discharge time constants. After the mentioned discharge time constants, failure occur in superconductors.

Voltages and currents in each single coil and each single FDU component, both in design and quench conditions, are estimated developing a suitable electrical model and implementing it in the ANSYS software.

Speaker: Giordano Tomassetti (ENEA)

MT_26_PosterPZ_template3.pdf

175 Mon-Af-Po1.16-02 [45]: Quasi-3D Thermal Simulation of Quench Propagation of Superconducting Magnets

In order to protect superconducting magnets, quenches must be detected on time. Unfortunately, conventional simulation predictions are not accurate enough, because they often overestimate the quench detection thresholds. These false triggers lead to frequent and unneccessary shutdowns, which considerably reduce the availability of the entire system and become even more critical for the newly developed magnets based on the Nb$_3$Sn technology. While multiphysical three-dimensional (3D) simulations are computationally expensive, two-dimensional (2D) simulations of the magnet's cross-section lack accuracy. To increase quench prediction quality while keeping the computational effort low, quasi-3D simulation methods can be employed. Here, the cross-section of the magnet is discretized with linear finite elements, while the transversal direction is resolved with polynomial spectral elements. This hybrid approach achieves significantly smaller system of equations than in the standard 3D approach and provides a higher accuracy than in the 2D case. This work deals with the transient simulation of the heat propagation in a dipole magnet. Different spectral basis functions are investigated and the method is validated against a benchmark model.

Speaker: Ms Laura D'Angelo (Technische Universität Darmstadt)

KWT2019-Poster-DAngelo_Laura.pdf

176 Mon-Af-Po1.16-03 [46]: Quench Detection of High-Temperature Superconducting Magnet using Unsupervised Learning Method

Quench detection of high-temperature superconducting (HTS) magnet is carried out using various signals like voltage, current and temperate from the magnet. Normally, the detection point is set to a fixed value, and when the measured value exceeded detection point, it is detected as a quench. The problem of this method is that the detection system may malfunction in a sequence that the user has not set before or high disturbance situation. In this study, various signals from normal operating state of HTS magnet are learned to the detection system using clustering which is one of the unsupervised learning methods. The learned data are clustered into a set of patterns that are classified through a K-means algorithm. Signals that are over the clustered range are detected as a quench. Quench detection is simulated using MATLAB and is analyzed the results with respect to the learning parameters.

Speaker: Haeryong Jeon (Yonsei University)

177 Mon-Af-Po1.16-04 [47]: Protection Studies of the HL-LHC circuits with the STEAM Simulation Framework

This paper presents a summary of protection studies being performed within the scope of the High-Luminosity Large Hadron Collider (HL-LHC) upgrade with the STEAM (Simulation of Transient Effects in Accelerator Magnets) simulation framework.

The HL-LHC upgrade features new technologies that are to be introduced into the Large Hadron Collider (LHC). This includes challenging Nb3Sn-based magnets with current densities that exceed those of the NbTi-based magnets presently used in the LHC, as well as new protection strategies such as the Coupling-Loss-Induced-Quench (CLIQ) device. Therefore, it is important to study the impact of these new technologies on the transient behaviour and protection aspects of the HL-LHC upgrade. These studies feature quench simulations of the various HL-LHC circuits where both the protection of the magnets and the busbars are considered. In addition, less common simulations types are done, such as studies of the impact of spurious quench heater and CLIQ firing on the beam, and the impact of fast losses arising from asynchronous beam dumps on the voltage-to-ground in the affected magnets.

The STEAM framework provides numerical tools for the efficient and accurate modelling of accelerator magnets, busbars and circuits. Beyond accurately modelling individual system components, STEAM also emphasizes the systems-engineering point of view, under which failures in one component (magnets, busbars, circuits, controls, etc.) cause system-wide repercussions that are studied with a cooperative simulation approach. These studies are relevant for the understanding of protection aspects and the preparation for the HL-LHC upgrade. Moreover, they will serve as references for performance evaluation of the upgraded machine.

Speaker: Matthias Mentink (CERN)

Protection Studies of the HL-LHC Circuits with the STEAM simulation framework.pdf

Protection Studies of the HL-LHC Circuits with the STEAM simulation framework.pptx

178 Mon-Af-Po1.16-05 [48]: Presentation withdrawn

179 Mon-Af-Po1.16-06 [49]: Working principle analysis and Parameter optimization of snubber circuit applied in 100kA quench protection system

Quench protection system aims to protect superconducting magnets in Large Superconducting Fusion Device (LSFD) from long time and severe conducting current. A 100kA super-high pulse current with very short pulse width produced by LC commutation circuit, flows reversely into the Vacuum Circuit Breaker (VCB) to force the magnets current cross zero, which ensures the reliable turn-off of VCB to protect the superconducting magnets. However, the large current change rate of the pulse current and the stray inductance of external circuit will generate extremely high overvoltage on the both end of VCB, which may result in the turn-off failed and shortened life of VCB. As the result, a snubber circuit consisted of snubber capacitor and snubber resistor is applied to mitigate the overvoltage of VCB.
In this paper, the producing reason of overvoltage of VCB is analyzed firstly. Then, the calculation and the theoretical analysis of transient process are given to illustrate the overall work principle of snubber circuit. And a series of simulations by using Matlab is presented to verify the correctness of the above analysis. In addition, in order to consider the performance and cost of the snubber circuit at the same time, the genetic algorithm is proposed to obtain the optimal parameters of the snubber circuit. At last, both simulation and theoretical analysis indicate that this set of parameters can greatly mitigate the overvoltage of VCB at a relatively lower cost.

Speakers: Dr Wei Tong (Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, 230031, China; Science island Branch, University of Science and Technology of China, Hefei, 230026, China.), Prof. Zhiquan Song (Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, 230031, China), Dr Chuan Li (International Joint Research Laboratory of Magnetic Confinement Fusion and Plasma Physics, Huazhong University of Science and Technology, Wuhan, 430074, China)

Mon-Af-Po1.17 - Fusion III: ITER

Conveners: Geonwoo Baek (Yonsei University), Prof. Marco Breschi (University of Bologna)

180 Mon-Af-Po1.17-02 [54]: Cold Testing of ITER Toroidal Field Winding Packs

The International Thermonuclear Experimental Reactor (ITER) is an international project aimed to build a fusion reactor using a magnetic confinement (Tokamak) for the high-energy plasma. This magnetic confinement it created by a set of various very large superconducting coils, mainly round poloidal field (PF) coils (upto 24 m wide) and D-shaped toroidal field (TF) coils (as high as 16m). The ITER machine utilises 18 TF coils in total, which are composed of a 100 tons winding pack (WP) enclosed in a 200 tons coil case (CC), each. F4E commissioned the insertion of the WP into the CC and subsequent closure welding to SIMIC. Before inserting the WP in the CC, the WP is cold tested at 80K. This cold testing process including all necessary equipment has been subcontracted from SIMIC to NOELL.
This document presents the design and manufacture of the cold testing equipment as well as status of execution and first results of the TF WP cold testing.

Speaker: Eckhard Theisen (Babcock Noell)

181 Mon-Af-Po1.17-03 [55]: Comparison of FEM Predicted and Measured values of the TF coil closure welding distortion

The International Tokamak Experimental Reactor relies in magnetic confinement of hot plasma. The main driver for the confinement is played by the Toroidal Field Coils (TFC). These magnets are composed by a winding pack, made of Nb3Sn superconductors, and a surrounding stainless steel structure or coil case (TFCC) which is closed by welding once the WP is inserted in the TFCC. The closure GTAW weld of the TFCC includes about 70m of weld ranging from 40 to 120mm.
Due to the tight tolerances that have to be respected on the final TFC, a mechanical quasi-static Finite Element Model (FEM) has been developed using ANSYS® software by Enginsoft and SIMIC, under the workframe of an F4E contract, to predict the welding distortion by simulating different welding scenarios and to confirm the definition of the required extra-material in the TFCC.
The FEM model was firstly benchmarked with validation coupons, then verified and fine-tuned with four 1:1 scaled TF coil case cross section mock ups. Finally, a full TF coil FEM model was developed in order to predict the deformation of the TFCC during the welding process.
The first TF coil was welded during the first half of 2019.
In this paper, a comparison between the deformation predicted by FEM and direct dimensional measurements of the distortions taken during the welding process of the TFC is presented. From the observation of the real deformed TFC shape, a new tuning of the model is proposed in order to improve the FEM model and reproduce with higher fidelity the welding distortions.

Speakers: Mr Marc Jimenez (Fusion for Energy), Alfredo Portone (Fusion For Energy/European Commission)

MT26-Pompa-poster-1.0.pdf

MT26-Pompa-poster-1.0.pptx

182 Mon-Af-Po1.17-05 [56]: F4E Procurement of the Pre-Compression Rings made of pultruded composite material

The ITER magnetic system includes the Toroidal Field (TF) Coils. To cope with the fatigue exercised on the TF Coils, and with the deformation resulting from the powerful magnetic fields, 3 Pre-Compression Rings (PCRs) will be placed on top of them and 3 below them. An extra set of 3 will be manufactured as spare and installed below the ITER machine in case there is a need in the future to replace the lower set.
In December 2016, F4E signed the contract with the French company CNIM for the procurement of 3 PCRs (with the option to produce 6 additional PCRs). 3 optional PCRs had been released in November 2018 so that CNIM is due to produce 6 PCRs and deliver them from May to November 2019.
This highly innovative process, proposed by CNIM and chosen by F4E, is based on a pultrusion technique that involves the manufacture of profiles of epoxy S2-glass. Each PCR is a manufacture by winding the flat pultruted profile (2mm thick and about 2800 m long) and utilizing an adhesive tape (0,12 mm thick) between layer to freeze the geometry. Finally, the PCR is machined to reach the required geometry tolerances. Each PCR will have a diameter of approximately 5 m, a cross-section of nearly 300 mm x 300 mm and will weigh approximately 3 T. The PCRs will finally be proof tested at 600MPa in hoop stress which corresponds to 1.5 time the operational hoop stress.
An extensive qualification phase has been released to prove that both materials and manufacturing technology can procure PCRs according to requirements.
This paper will describe the manufacturing processes, the results of the qualification phase and the status of the production.

Speaker: Eva Boter (Fusion for Energy)

poster horizontal_v3.pdf

183 Mon-Af-Po1.17-06 [57]: ITER Pre Compression Ring Test Facility FEM analysis

The Pre Compression Ring (PCR) system is a key component of ITER magnetic system that radially constraints the Toroidal Field (TF) coils against the out of plane magnetic forces. Due to its peculiar characteristics (one of a kind component, unidirectional S2 fiberglass in epoxy matrix) an experimental campaign has been planned on both reduced and full scale specimens. The tests purpose is the validation of the manufacturing technique verifying the compliance with the structural requirements. The Pre Compression Ring Test Facility (PCRTF) aims at reproducing the loading condition whom the PCR is subjected to in the tokamak assembly with a safety margin. For this purpose a detailed non linear 3D FEM model was developed permitting the simulation of the tests to be performed of the full scale PCR and on two different reduced PCR sub-assemblies. The analyses permitted to assess not only the stress field inside the specimens themeselves but also the stress, displacements and global forces for the modules of the testing rig. This led to a fine optimization of the PCRTF components also investigation several off-design scenarios that may occur during the assembly and the operation of the facility.
The views and opinions expressed herein do not necessarily reflect those of the ITER Organization

Speaker: Luigi Reccia (Fusion for Energy)

Mon-Af-Po1_17-06 [57] ITER Pre Compression Ring Test Facility FEM analysis.pdf

Mon-Af-Po1.18 - Fusion IV: Thermohydraulics, Mechanical, and AC Losses

Conveners: Daniela Boso (University of Padova), Lucas Brouwer (Lawrence Berkeley National Laboratory)

184 Mon-Af-Po1.18-01 [58]: Advanced mechanical modeling of cyclically loaded cable-in-conduit conductors for fusion magnets

The electrical performance degradation of Nb3Sn cables in the Cable-in-Conduit Conductors design has been well documented in literature. The Nb3Sn composite strands exhibit a critical current density that strongly depends on the strain state of the superconducting filaments. During the machine operation, the conductors are submitted to several electromagnetic and thermal cycles affecting the Nb3Sn mechanical state and consequently the capacity of the conductors to transport current. Different studies based on both a macroscopic and a microscopic approach have been performed so far to identify the mechanisms determining the conductors’ behavior. Nevertheless, no theory permitting to predict the electrical performance of cyclically loaded conductors has been developed yet. Therefore, a solid electromechanical model able to tackle the analysis of CICC and other fusion cables when they undergo thousands of cyclic loadings would be very useful.
In this paper an advanced mechanical model to study the mechanical behavior of ITER TF CICC based on the new version of the MULTIFIL finite element code is presented. The thermal loadings simulations in MULTIFIL code have been upgraded to solve the non-homogenous strain distribution problem presented in a previous work. The model was adapted to take into account the Lorentz force cumulative effect of the other petals on the one under analysis. Moreover, new material constitutive laws have been implemented in the code.
An assessment of the electromagnetic behavior based on the mechanical analysis was also performed to make a preliminary comparison between the trend of the simulated results and the trend of the experimental ones obtained in the tests of the TFIO1 sample in the SULTAN facility.

Speaker: Rebecca Riccioli (CEA, Cadarache, France)

185 Mon-Af-Po1.18-02 [59]: CICCs coupling losses: Analytical COLISEUM model enhancement and experimental cross-checks

Modelling by analytical approach the coupling losses of CICCs used in tokamaks remains a challenge to be reliable at all frequencies. This is usually done using either CPU consuming numerical approaches or heuristic models such as MPAS now used for ITER.

A recently developed analytical model COLISEUM (COupling Losses analytIcal Staged cablEs Unified Model) applies at various scales going from strands to two-stage cables and is able to predict AC losses upon geometrical and electrical parameters of a cable. A previous analysis identified the impact of these parameters on the behavior of a multiplet of strands, in order to give our model a solid base starting from the most academic step of the simulation. COLISEUM and MPAS are based on different assumptions and confronted to cross validate and strengthen themselves.

In the present work we confront COLISEUM with results from purely numerical model (JACKPOT, U. Twente). Previous crosscheck performed showed a moderate mismatch that we tried to understand by starting over from basic CICC stages (low level multiplets). We will in particular put the emphasis on conductances definitions in every models (i.e. MPAS, COLISEUM, JACKPOT) and the way to ensure their crossed consistency.

The analysis using COLISEUM and MPAS is confronted to experimental measurements of AC losses performed at CEA Cadarache in the JOSEFA facility using magnetization method. Two main objectives: compare the construction (assumptions, limitations, etc.) and reduce the number of free parameters in both models. New settings were implemented in JOSEFA enabling to generate sinusoidal field variations, giving access to more refined signal interpretations.

Contribution of the above results to COLISEUM and MPAS enhancement and complementarity of analytical, experimental and numerical part of the work will be discussed to consolidate our models. Recommandation will be given regarding extension of the model to three stage description.

Speaker: Mr Maxime Chiletti (CEA Cadarache)

186 Mon-Af-Po1.18-03 [60]: Effect of flow unbalance on the operational performance of the KSTAR PF1UL magnet with the parallel cooling channel

The cryogenic circuit used to cool a large superconducting magnet such as a tokamak system must be designed while considering the cooling conductance due to the many branches.The KSTAR PF1~2 upper and low magnet have ten and eight cooling channels parallel respectively. The pressure drop of the magnets is adjusted by cryogenic valve and is maintained by a supercritical helium circulator. The flow rate should be uniform among the cooling channels or magnets but the flow unbalance is observed in the real system. To investigate of the unbalance effects, the simple model of PF1~2 upper and low magnets is developed using Supermagnet code. The maximum temperaure is studied in details depending on the unbalance ratio.

Speaker: HyunJung Lee (National Fusion Research Institute)

Poster_MT26-Mon-Af-Po1 18-03(60)_hjlee.pdf

187 Mon-Af-Po1.18-04 [61]: AC Loss Analysis on the KSTAR PF1L Coil Based on Long-Term Operation Data

Typical tokamak fusion device uses CS (Central Solenoid) coil to initiate plasma heating by ramping up the coil with steadily increasing current which induces the plasma inside the vacuum vessel. For the case of the KSTAR (Korea Superconducting Tokamak Advanced Research) which uses superconductor for all of its magnets, this operation brings various AC losses to the magnets including hysteresis loss, coupling current loss, and eddy current loss. Thus it is important to analyze AC losses of the superconducting magnet for its reliable operation in two main perspectives: short term quench prevention and long term steady-operation. With 10 years of operation, KSTAR has provided many invaluable data in superconducting magnet operation regarding AC loss issues. This paper focuses on the AC loss of the KSATR PF (Poloidal Field) coil based on the long term operation data. Among the components of the PF coils, PF1L coil contributes to CS coil operation from which it experiences the highest field, and consequently the largest loss. First, numerical approach will be taken to analyze quantitatively each AC loss. Then the losses will be compared with the total loss measured by the calorimetric method. Finally, the results will be interpreted in qualitative manner to investigate the possible relation between the AC loss and the magnet’s performance in persistent operation.

Acknowledgement
This study was supported by Korean Ministry of Science and ICT under the Korea Superconducting Tokamak Advanced Research (KSTAR) Project. A part of the study was also supported by the National Research Foundation of Korea as a part of Mid-Career Research Program (No. 2018R1A2B3009249).

Speaker: Jung Tae Lee (Seoul National University)

MT26_Mon-Af-Po1.18-04 [61]_KSTAR.ACloss_JL_20190920[F].pdf

188 Mon-Af-Po1.18-05 [62]: Design of Quench Protection System for K-DEMO TF Magnet

Conceptual design of the K-DEMO magnet system has been under way. From the up-to-date design activities, the TF magnets use two different types of cable-in-conduit conductors (CICCs) where high field region uses quite an amount of superconducting wires, but in relatively low field region, substantial amount of superconducting wires should be replaced by copper wires. The stored magnetic energy is estimated to be over 49 GJ. Eighteen TF magnets are series-connected and charged by a power supply, where the design current is 65.52 kA. Protection circuits for the K-DEMO TF magnets should be designed with a fail-free concept after interlock signals are received. The design activities to minimize the system failures are carried out to guarantee the reliable and stable operation

Speaker: Dr Yong Chu (National fusion research institute)

189 Mon-Af-Po1.18-06 [63]: Quench analysis of the CFETR TF Coil Using the Gandalf Code

China Fusion Engineering Test Reactor (CFETR) is the next device in the roadmap for the realization of fusion energy in China, which aims to bridge the gaps between the fusion experimental reactor ITER and the demonstration reactor (DEMO). CFETR will be operated in two phases: Steady-state operation and self-sufficiency will be the two key issues for Phase I with a modest fusion power of up to 200 MW. Phase II aims for DEMO validation with a fusion power over 1 GW. For saving the cost of construction and meeting both Phase I and Phase II target with achievable technical solutions, a new design has been made by choosing a larger machine with R =6.6m,/a=1.8m, BT= 6-7T. Over 1GW fusion power can be achieved technically and it is easy to transfer from Phase I to Phase II with the same machine.
The Toroidal Field (TF) coil is a crucial system in the tokamak, which provides the main magnetic field to confine the plasma. One TF coil will be constructed next 5 years in the support of Chinese government. The quench of TF coils can be induced by many factors, for example, thermal disturbance, mechanical disturbance, vacuum destruction and so on. For the safety operation of superconducting magnet, the quench detection and quench protection system is very important for the TF coil system of CFETR. In order to give the design reference of quench detection and protection system, the assumed quench phenomenon of TF coil is analyzed. The evolution of the voltage of the normal zone, hot spot temperature and mass flow rate of cooling channel of the TF coil are simulated.

Speaker: Mr Xinghao Wen (University of Science and Technology of China)

wenxinghao-MT26.pdf

190 Mon-Af-Po1.18-07 [64]: Presentation withdrawn

191 Mon-Af-Po1.18-08 [65]: Operational Analysis of KSTAR CS Magnet

The KSTAR magnet system has stably operated since the first plasma in 2008. Scientifically important results have been achieved such as long-pulse plasma operation up to approximately 80 seconds, ion temperature more than 100 million degrees, the world-longest ELM suppression, and so on. During more than 20,000 shots, the CS magnet has experienced temperature rise especially due to AC losses as well as electro-magnetic loads. In this paper, the operational characteristics are analyzed with accumulated data such as coil voltages, temperatures, pressures, flow rates, and so on. Based on these results, conductor performance and stability issues are discussed.

Speaker: Yong Chu

192 Mon-Af-Po1.18-09 [66]: A pressure drop model for helium flow in Cable-in-Conduit conductors based on porous media analogy

The pressure drop in Cable-in-Conduit Conductors cooled by a flow of liquid or supercritical helium is one of the key parameters for the design of the large superconducting magnet systems, which determines the heat removal capability and the thermal stability. In this paper, a new model for predicting pressure drop in Cable-in-Conduit conductors is derived based on an analogy between the bundle of strands in the cable and a porous medium. The new prediction model indicate that the pressure drop in Cable-in-Conduit conductors is affected by the structure of cable and the physical properties of the liquid, such as void fraction, tortuosity, hydraulic diameter, density and viscosity of liquid helium. In order to verify the validity of the pressure drop model developed in this paper, the predictions are compared with the experimental data, the results show that the predictions are in good agreement with the experimental data, this verifies the validity of the present pressure drop model for Cable-in-Conduit conductors. In addition, the effects of the cable structure parameters on pressure drop are simulated, which explains why the Katheder correlation can be used to predict the pressure drop of Cable-in-Conduit conductors at large Reynolds numbers.

Speaker: Zhicai Ma (Lanzhou University)

Presentation.pdf

Mon-Af-Po1.19 - Power Supplies and Flux Pumps I

Conveners: Daniel Davis (FSU/NHMFL), Mr Patrick Noyes (Lockheed Martin)

193 Mon-Af-Po1.19-01 [67]: Design and test of the power supply for a fast kicker magnet

To perform fast beam switching during spot scanning procedure, the kicker system is adopted in HUST-PTF (Huazhong University of Science and Technology Proton Therapy Facility). The rise and fall time is about 100us, and the maximum repetition rate is 250Hz. A high dynamic performance power supply is required to implement the kicker function. Utmost care should be taken to avoid Electro-magnetic disturbances to surrounding equipments caused by high voltage slopes and voltage overshoot. This paper introduces the optimal design and presents the test results of the power supply. A trade-off between voltage slope reduction, overshoots and dynamic performance has been made. The results show that the power supply meets the design specification.

Speaker: Mr Wenjie Han (Huazhong University of Science and Technology)

Mon-Af-Po1.19-01 [67].pdf

Mon-Af-Po1.19-01 [67].pptx

194 Mon-Af-Po1.19-02 [68]: The design and analysis of power supply topology for high-field MRI superconducting magnet

A superconducting multi-coil magnet system has been designed, analyzed and optimized, serving as demonstrator for a high filed Magnetic Resonance Imaging (MRI). The designed superconducting magnet inductance is 3500H. The operating current is 230A. The stored energy is as high as 93MJ. The superconducting material is NiTi/Cu. The normal excitation and demagnetization are completed by the power supply, after the excitation, the power supply is disconnected. This paper presents the design and research of the two different kinds of magnet power supplies which are all adjusted for the project, the one is three-phase bridge phase-controlled rectifier which is simpler and the other is based on high-frequency which is of high power density, reduced weight, and low noise without compromising efficiency and reliability. Besides, the design of the quench detection systems for solenoid model coil was also described in this paper.

Speaker: Prof. Chao Zhou (Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, Anhui, China )

The design and analysis of power supply topology for high-field MRI superconducting magnet.pdf

195 Mon-Af-Po1.19-03 [69]: Design and Implementation of SoC Embedded Waveform Acquisition System for Surveillance and Diagnostics of Pulsed Magnets Power Supplies

The pulsed magnets power supplies systems to affect injection and extraction of the electron beam have been realized for the Taiwan Photon Source (TPS) and Taiwan Light Source (TLS). The control systems of these pulsed magnets power supplies have been achieved as the well operation interfaces. To accomplish higher reliability operation, the advanced real-time diagnostic toolkit of pulsed magnets power supplies has to be developed. The SoC (System-on-Chip) embedded waveform acquisition system has been designed, implemented and applied for inspecting the pulsed magnets power supplies during routine operation. This waveform acquisition system not only owns 125 MS/s sample rate, 50 MHz bandwidth and 14 bits resolution, but also supports the EPICS software framework for complete system integration. The acquired current transformer waveform has been extracted immediately specific characteristics for examining the status easily, and these values have been archived for long time observation. This paper reports the design, implementation and real-time data analysis of SoC embedded waveform acquisition system for pulsed magnets power supplies systems.

Speaker: Mr Chun-Yi Wu (NSRRC)

Mon-Af-Po1.19-03 [69].pdf

196 Mon-Af-Po1.19-04 [70]: Modelling and measurements of stator vs magnet width effects in high-Tc superconducting dynamos.

High-Tc superconducting (HTS) dynamos are simple devices that provide an effective alternative to current leads for driving DC currents in superconducting coils. The simple geometry of these devices consists of some arrangement of superconducting stators and exciter magnets. With recent advances in our ability to model such systems, we investigate the relationship between width of the superconducting stator and the exciting magnet. This is of interest as previous studies have shown that a non-trivial optimum exists, as the extreme cases yield poor performance. With validation against experiment, we show that this optimum is caused by the trade-off between spatial field gradient and the total flux magnitude from the exciter magnet. Simulations also allow us to inspect the local flow of critical and over-critical currents in the stator that give rise to the relationships presented.

Speaker: Ratu Mataira (Robinson Research Institute, Victoria University of Wellington)

PosterLandscapeRMStatorWidths.pdf

197 Mon-Af-Po1.19-05 [71]: Study of stator design for rotating type HTS Flux pump

HTS flux pump is a contactless charging method for a superconducting magnet, which can reduce the cryogenic losses associated with current leads. Rotating type flux pump is a simple and practical flux pump, which has great application in charging HTS magnets. For the rotating flux pump, the design of rotor has great impact on the performance of flux pump. In this study, we will change the rotor design of the rotating type flux pump. Different design will be compared and analysed. Based on the study, we will investigate the effective methods to improve the performance of HTS flux pump.

Speaker: Mr Jun Ma (University of Cambridge )

198 Mon-Af-Po1.19-06 [72]: Efficiency analysis and improvement of Transformer-rectifier flux pump for high current magnets

Flux pumps are capable of injecting flux into an HTS circuit without electrical contact. They are ideal alternatives to traditional current sources and current leads to power HTS magnets. These devices make it possible for HTS magnets to be smaller, lighter, and more accessible.
    In recent years, our group in Cambridge has developed a transformer-rectifier HTS flux pump switched by dynamic resistance, which demonstrates superior performance. Despite the achievements, many works could be done to improve performance. This paper aims to analyze the power loss and efficiency of the flux pump and further reduce the loss. The analytical solution will be proposed and verified by comprehensive experiments.

Speaker: Qihuan Dong (University of Cambridge )

199 Mon-Af-Po1.19-09 [73]: Contactless Magnetizing Technology Based on YBCO High Temperature Superconducting Tape

Recent progress in material science has proved that high temperature superconductors have a great potential to trap significant magnetic flux due to the characteristics of flux pinning, which makes them particularly attractive for a variety of engineering applications. However, using traditional methods to magnetise a superconductor, the applied field needs to be at least as high as the expected magnetic field, which needs high current power supply equipment and leads to a huge expenditure. This research focuses on a Thermally Actuated Flux Pumping Method (TAFPM) which is a novel technique to magnetise the superconductor which only requires a magnetic field with strength as low as that of permanent magnets and theoretically a flux density of more than 20 T can be obtained. Finally，with this thermally actuated magnetisation flux pumping technique, we can make lighter, more efficient and cheaper superconducting power devices, which will make a big contribution to the technical innovation of a variety of engineering applications, ranging from public transportation, through medical equipment, to high energy physics.
Based on the YBCO high temperature superconducting bulk, This research uses the Thermally Actuated Flux Pumping Method to generate a travelling magnetic wave in order to magnetise the superconductor, by measuring the trapped field and AC loss in the high temperature superconducting, optimising the Thermomagnetic Material (TM) and the travelling magnetic wave, finally making the Thermally Actuated Flux Pumping system more efficient and stable. Based on the critical state model, this research also analyses the critical current density JC and flux pinning force FP, investigating the micromechanism of the flux creep effect for 2G high temperature superconductors, revealing the physics underlying the flux pumping effect based on the travelling magnetic wave, finally providing the theoretical support and technical assurance to realise the steady strong magnetic field for high temperature superconductors.

Speaker: Dr Yujia Zhai (Hunan University)

mt2019_postertemplate_pptx_90x140 (改）.pptx

Mon-Af-Po1.20 - Stability of Conductors and Coils I

Conveners: Mr Etienne Rochepault (Université Paris-Saclay (FR)), Dr Minfeng Xu (GE)

200 Mon-Af-Po1.20-01 [74]: Thermal, Electrical and Mechanical Behaviors of Metal-as-Insulation HTS Coils Wound with Commercial REBCO Tapes under High Background Magnetic Fields at 4.2 K

Recently, several high temperature superconductor (HTS) companies, such as SuperPower, SuperOx, Shanghai Superconductor Technology (SST), and THEVA, succeeded in improving current-carrying performance of their REBCO products under high magnetic field at low temperature. However, except HTS coils made of SuperPower REBCO tape, there are insufficient reports regarding thermal, electrical and mechanical behaviors of HTS coils wound with other REBCO tapes such extreme conditions. Therefore, in this study, two sets of two metal-as-insulation (MI) REBCO double-pancake (DP) coils which have inner joint between top and bottom pancake were fabricated: 1) a set A with two DP coils wound with 140 µm thickness THEVA tape for one pancake and with a 75 µm thickness SuperPower tape for the other pancake, the aim being to use the THEVA tape to use its different a-b plane orientation with regards to the tape surface to accommodate the bending magnetic flux line at the extremity of the assembly ; and 2) a set B of two DP coils wound with a 75 µm thickness SST tape. When winding the DP coils, a sapphire plate was inserted between the single pancakes as a cooling channel inside the DP coils. After each MI DP coil was tested in a bath of LN2 at 77 K, the DP coils were mounted on a support structure for assembly as MI HTS magnet set A and B. The thermal, electrical and mechanical characteristics of the HTS magnet sets were examined with various ramping conditions under various background magnetic fields at 4.2 K. From these results, current-carrying performance, critical current uniformity, thermal and mechanical stabilities of the MI magnet under back ground fields in range of 0-20 T will be discussed with regards to technical specifications of each company’s REBCO tape.

ACKNOWLEDGMENTS: The authors acknowledge the support of the LNCMI-CNRS, member of the European Magnetic Field Laboratory (EMFL), and of the French National Research Agency (ANR) through the contracts ANR-10-LABX-51-01 (Labex LANEF) and ANR-14-CE05-0005 (NOUGAT project)

Speaker: Jungbin Song (LNCMI-CNRS)

MT26 -MON-Af-Po1.20 (Jungbin SONG).pdf

201 Mon-Af-Po1.20-02 [75]: Performance Study on the No-Insulation HTS Coil wound with Narrow-Stacked wire

As a novel high-temperature superconducting (HTS) conductor structure composed of the stacked 1-mm wide REBCO tapes, Narrow-Staked (NS) wire has been demonstrated to have a significant reduction effect of AC loss and screening current induced field (SCIF) in the insulated HTS coils. Thus, NS wire is a promising HTS conductor design for the practical magnet applications. Meanwhile, due to the enhanced engineering current density, thermal stability, and self-protecting features compared with the traditional insulted HTS coil, no-insulation (NI) coil has been a widely used technology for HTS magnets. Although NS wire was proved as an improvement for insulated HTS magnet, the NS wire effects on NI coil is not confirmed due to the special characteristics of the NI coil. In this paper, a NI pancake coil sample was wound with the fabricated NS wire. To evaluate the performance of NI coil wound with NS wire, the charge-discharge and sudden discharge tests were undergone at the liquid nitrogen temperature. Besides, the characteristic resistance was also analyzed for the NI coil sample. This paper result will provide a useful reference for NS wire application on NI HTS magnets.

Speaker: Mingyang Wang (Shanghai Jiao Tong University)

post-Mon-Af-Po1.20-02 [75] .pdf

post-Mon-Af-Po1.20-02 [75] .ppt

202 Mon-Af-Po1.20-03 [76]: Improvement on Temporal Stability of HTS No-insulation Coil by Enhancing Transverse Resistivity

Abstract:
Comparing with conventional insulated high temperature superconducting (HTS) coil, the no-insulation (NI) one has advantages of high stability, self-protection and fast quench recovery. However, the unstable and non-uniform magnetic field appear in NI coil during exciting owing to too low transverse resistivity among turns. This paper proposed a method for increasing stability and decreasing screen current by enhancing transverse resistivity among turns of no-insulated HTS coil which was fabricated by co-winding REBCO and stainless steel (SS) tapes. The latter tape functioned as increasing mechanical strength and protection of NI HTS coil. In order to enhance the transverse resistivity, the SS tape was thermally and chemically treated. Two NI HTS coils co-wound with treated and non-treated SS tapes were designed and fabricated. Both of them are analyzed and tested, the results show that the NI HTS coil with co-wound by treated SS tape has lower screening current and coupling losses as well as higher temporal stability than that one co-wound by non-treated SS tape.

Key words: non-insulation coil; temporal stability; transverse resistivity, treatment

Speaker: Mr Yanqing Lu

poster-Yanqing Lu.pdf

203 Mon-Af-Po1.20-04 [77]: Experimental Study of Quench Performance for YBCO Coated Conductors

When high temperature superconducting (HTS) devices run in the power system, the superconducting tapes may quench due to power system fault. Therefore, quench characteristic is one of the most important characteristics of superconducting tapes. In this paper, in order to obtain the quench characteristics of YBCO coated conductor, we have established an over-current experiment system based on waveform controllable power supply. The voltage and current of YBCO coated conductor sample are measured under over-current with various amplitudes. The variation of quench and recovery performance for YBCO coated conductor samples is discussed. In order to verify the validity of the experiment data, we used the thermal-electrical analogy method to build a computational model. During the over-current process, the transient resistance of YBCO coated conductor sample is greatly influenced by over-current current amplitude and its rate of change. When the over-current current is relatively large, the YBCO coated conductor sample has a recovery process after impact process. The work in this paper may contribute references to design and protection of superconducting fault current limiter (SFCL).

Speaker: Panpan Chen

204 Mon-Af-Po1.20-05 [78]: Thermal and electric characteristics of no insulation REBCO coil with conduction plates and epoxy impregnation

NI (no-insulation) winding method have been widely used to develop high field superconducting magnets using REBCO wires due to excellent mechanical and electromagnetic stability. When REBCO magnets are operated in a bath of cryogens such as liquid helium and liquid nitrogen, sufficient cooling is achieved by pool boiling of the cryogen. However, conduction-cooled REBCO magnets must ensure sufficient thermal paths from cryocoolers to the magnets. When the NI REBCO magnets are not impregnated by epoxy, radial heat transfer, which is perpendicular to the wire surface, is limited due to the dry contacts between the REBCO wires. To solve this problem, thin metal conduction plates, attached by epoxy to the wound surface of the coil, are usually used to enhance radial thermal conductance as additional thermal path. In the case of REBCO magnets with large mechanical stress, vacuum impregnation is applied using epoxy with thermal contraction similar to the magnet to avoid well-known delamination problem of REBCO wires.
In this study, two kinds of REBCO DPCs (Double Pancake Coil) were fabricated: 1) DPC with conduction plates which are attached to the wound surface of the coil by epoxy; 2) Vacuum impregnated DPC with conduction plates. The coils were installed in a conduction cooling test apparatus to compare the thermal characteristics during charging and discharging operations. In addition, AC loss, eddy current loss and leak-current loss were quantified by analyzing the measured temperature variations. The results will be used to develop mechanically robust and thermally stable REBCO magnets of maglev trains and large wind power generators.

This research was supported by "Core technology development of subsonic capsule train" of the Korea Railroad Research Institute (Grant number: PK1901A1) and by Korea Electric Power Corporation (Grant number: R18XA03).

Speaker: Mr Jeongmin Mun (changwon national university)

205 Mon-Af-Po1.20-06 [79]: Study on the effect of metallic protection ring in no-insulation HTS coils

We have been studied the no-insulation (NI) technique and co-winding method with various metallic tapes. The improved thermal stability of NI test coils by bypassing the transport current into the transverse direction was experimentally confirmed and reported. However, there are the problems of the transient stability and the reduction of critical current of NI HTS coils due to the thermal and mechanical stress according to electromagnetic force and cooling process. In addition, in NI HTS coils, we could not expect an effect of NI winding technique when a normal transition occurs at the outermost part of the coils. Therefore, in this study, we propose to install the metallic protection rings composed of two or more rings with different electrical and mechanical properties on the outermost turn of NI coils to improve the thermal, mechanical and electrical stabilities. This protection rings are mechanically and electrically connected to NI coils in parallel. The current bypassing characteristics in the transverse direction and normal zone propagation property in NI test coil with/without copper protection ring was investigated experimentally. The current bypassing from the outermost part of NI test coil to the copper protection ring was observed and the local temperature rising at outer part of test coil due to thermal disturbance was suppressed. The detail experimental results by copper protection ring will be presented.

Speaker: Seokbeom Kim (Okayama University)

MT26-KIM2.pdf

206 Mon-Af-Po1.20-07 [80]: Influence of coil size and operating temperature on transient stability in multi-stacked no-insulation REBCO pancake coil system

The no-insulation coil is expected as a technology that can realize both high current density and high thermal stability which are originally trade-off relationship in REBCO coil application. And this technique has been mainly studied for application to small diameter inner coil of NMR magnet exceeding 30T. In this case, the coil is cooled by 4.2 K liquid helium. On the other hand, we have been developing a REBCO coil system aimed at application to high-magnetic-field whole-body MRI and medical cyclotron for cancer therapy. For this application as well, a no-insulation coil is considered as a technology satisfying both high current density and high thermal stability. The REBCO coil which we aim for development has a diameter of about 1 m, the generated magnetic field is about 10 T, and conduction cooling around 30 K is assumed. Therefore, since the size, operating temperature and magnetic field are different compared with those of the NMR coil, there is a possibility that the electromagnetic, thermal and mechanical behavior when adopting the no-insulation coil winding may be quite different.　In this presentation, we report on the behavior when local normal transition occurred in multi-stacked no-insulation REBCO pancake coils by numerical analysis considering coil size, operating temperature and magnetic field as parameters. For numerical analysis, we conducted a coupled analysis of current distribution analysis based on PEEC (Partial Element Equivalent Circuit) model and thermal analysis by two-dimensional finite element method.
The part of this work was supported by Grant-in-Aid for Scientific Research (S) Grant Number 18H05244, the Ministry of Education, Science, Sports and Culture.

Speaker: Atsushi Ishiyama (Waseda University)

MT_onoshita ver.final.pdf

207 Mon-Af-Po1.20-08 [81]: Presentation withdrawn

208 Mon-Af-Po1.20-09 [82]: Millisecond Dynamic Effects During Sudden Discharge and Cycling Characteristics of an HTS Stainless-Steel-Insulated Double Pancake Coil

We have tested an intermediate-size HTS stainless steel double pancake coil (132 turns per coil) and discovered dynamic effects during sudden discharge on millisecond scale. Two main approaches have been compared: soft and hard breaks. The soft break is when the power supply is turned off suddenly but the shunt resistors (168 milliohm) is still connected. The hard break uses a high voltage contactor to suddenly open the circuit so that the DPC leads are completely open. The hard break is dangerous to traditionally insulated low temperature magnets, but the SS-insulated HTS DPC retained integrity over >80 power cycles. Voltage decay curves for the soft and hard breaks are studied on short and long timescales. On long timescales, we observe the expected exponential decay and measure the time constant to calculate contact resistance. On short timescales, we observe highly dynamic effects: a hyper-exponential decay suggesting that the inductance or contact resistance is changing with time, likely an indication of the RL circuit forming.

Acknowledgement
The authors would like to thank Y. Wang, E. Burkhardt, K. Holland, K. Schrock, and S. Chandrasekaran for their assistance and support at Michigan State University and thank K. Amm and P. Wanderer for general support at BNL. This work was supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661. Magdelena Allen was funded by the U.S. Department of Energy, Office of Science, Office of Workforce Development for Teachers and Scientists (WDTS) under the Science Undergraduate Laboratory Internships Program (SULI), and thanks Honghai Song for his mentorship at BNL.

Speaker: Honghai Song (Brookhaven National Laboratory)

Mon-Af-Po1.21 - Motors III

Conveners: Kyeongdal Choi (Korea Polytechnic University), Vicente Climente-Alarcon (University of Cambridge)

209 Mon-Af-Po1.21-01 [88]: Optimization design of Stator Notch Shape of Brushless DC Motor by Response of Surface Method

Brushless dc motor (BLDC) has high output and high efficiency characteristics. It is possible to reduce the size and weight of the device and is used throughout the society. Among them, vibration and noise reduction are becoming important issues as they are used in household appliances and automobiles adjacent to people.Vibration and noise are caused by electrical causes such as spatial harmonics and magnetic saturation. Mechanical causes are caused by cogging torque and mechanical assembly.In a BLDC motor using a permanent magnet, the ferromagnetic material near the magnetized teeth is subjected to force when the teeth are magnetized by permanent magnets. In other words, the rotor located at the upper part moves by the tangential force and stops at the position where the rotor and the tooth that are shifted coincide with each other. The generated force at this time is called the cogging torque.Cogging torque induces torque ripple during operation of the motor, adversely affecting noise and vibration.In this paper, the design optimization of the stator shape of the surface permanent magnet type (SPM type) outer ring type BLDC motor was carried out for cogging torque and magnetic saturation reduction.Typically, there are skew, tapered, notch, etc. in a manner for cogging torque reduction and magnetic saturation relaxation. Among them, the application of the notch shape is easy and cost-effective.Therefore, the notch shape is applied considering cost reduction and fabrication, and the notch shape of the stator increases the magnetoresistance and magnetic flux density by increasing the length of the gap and the volume of the gap.Therefore, as the magnetic flux density is reduced, the cogging torque and the magnetic saturation decrease. To verify this, electromagnetic analysis is performed using FEM software ANSYS Electromagnetic.In order to analyze the effect of cogging torque reduction and magnetic saturation on vibration, electromagnetic characteristics analysis and vibration characteristics analysis are performed in conjunction with ANSYS Workbench.

Speaker: Yongdae So

Mon-Af-Po1.21-01 [88] Optimization design of Stator Notch Shape of Brushless DC Motor by Response of Surface Method.pdf

210 Mon-Af-Po1.21-02 [89]: Analysis of Design and Mechanical Properties of AISG with Brush and Slip-Ring Structure

Currently, the ISG is commercialized and under active research in the 48V hybrid system. However, in a typical vehicle using a 12V system, the starter motor and generator are operated separately. In this paper, we report the development of a general advanced integrated starter-generator(AISG) for vehicles using 12V power supplies. The specifications of the power source are lower than that of conventional integrated starter-generator(ISG). It is not easy to implement in a 12-V battery system of a typical car without using a separate power conversion device, such as a converter. combining a starter motor and an alternator into one integrated system has many advantages. The first one is improving the fuel economy by stopping the engine during deceleration, unlike existing starter motors. The reason is that the conventional starter motor uses a DC motor, which is much lower in efficiency than a permanent magnet (PM) motor. Second, the torque of the motor can be reduced, and the price can be reduced. Rare earths account for approximately 40% to 50% of the price of PM motors. The AISG system in this study reduces the torque burden by using a torque increase mechanism instead of reducing rare-earth use. The motor used in the AISG is a permanent magnet-assisted-wound field synchronous motor(PMA-WFSM) that includes a brush and slip ring. A permanent magnet inside the rotor core of a PMA-WFSM increases the air gap flux density and relaxes the magnetic flux saturation of the core. As a result, the torque of the electric motor can be increased and a coordinated operation with the planetary gears leads to higher performance. The effect of increasing the torque by including permanent magnets in the design was validated using finite element method (FEM) analysis. In addition, analysis of the mechanisms was performed vis-à-vis the various mechanical structures.

Speaker: Hyunwoo Kim (Hanyang university)

211 Mon-Af-Po1.21-03 [90]: Presentation withdrawn

212 Mon-Af-Po1.21-04 [91]: A study on Improvement of Power Density and Efficiency of Permanent Magnet BLDC motor

1) Introduction
Brushless DC motor (BLDC) have wide operating range and can high power density and high torque. Therefore, BLDC is used in various fields such as vehicle, aviation, home appliances. However, there is a problem that a torque ripple occurs in a phase commutation section in which a current flows. In order to overcome such problems, various studies have been conducted to improve the power characteristics of the BLDC motor.
2) body
In this paper, a study on power density and efficiency improvement of permanent magnet brushless DC motor (BLDC). In general, there is a way to improve the power characteristic of the motor by increasing the main flux of the permanent magnet. Applying the halbach magnet array structure not only increase the magnetic flux, but also reduces the coreloss of the motor. Also, the inner rotor type motor has a simple radiating structure for the reducing thermal loss generated in the teeth of the motor. Therefore, it is superior in terms of reduction of thermal loss compared to the outer rotor type motor. On the other hand, outer rotor type motor has motor magnet usage than inner rotor type motor. Therefore, outer rotor type motor can improve torque and efficiency compared to inner rotor type motor for the same size. In order to verify this, the inner rotor type motor and the outer rotor type motor with the same size and power were designed. Also, the electronic and thermal characteristic of the two motors were analyzed through the finite element analysis (FEA).

Speakers: Seungheon Lee (Hanyang University), Hyunwoo Kim (Hanyang University)

213 Mon-Af-Po1.21-05 [92]: Design and Analysis of a Multi-Flux-Modulated Permanent Magnet Motor

Flux-modulated permanent magnet (FMPM) motors have attracted widespread attention in many applications due to the superiority of low-speed large-torque, such as the electric vehicles. In the type of motors, the flux modulation effect is the key to obtain the excellent torque performances, which realize the electric gear operation by forming the matching between the magnetic fields with high PM pole-pairs and low winding one. So in previous studies, the flux modulation effect of the FMPM motor has been the main research subject, where the performance improvements are often realized by the single design of PMs, or modulator, or winding. It reveals that the highly efficient utilization of modulation effect is an effective path to deeply explore and develop the performance potential of the FMPM motors. It is worth noting that, in motor energy conversion, the motor flux is often modulated by one time, which is inferred that the increase design of modulation times may be another effective way to improve the modulation effect utilization. In this paper, a concept of multi-flux-modulation (MFM) is proposed, and a multi-flux-modulation flux-modulated permanent magnet (MFM-FMPM) motor is designed and investigated. It contains a stator, middle PM rotor, and inner PM rotor. And the halbach-array is applied in the inner rotor to increase the PMs utilization. The key of the MFM-FMPM motor is that the MFM can be divided into three modulation combinations. One of the magnetic fields generated by the PMs in the inner rotor is modulated by the modulator in the middle rotor. Simultaneously, the other two magnetic fields generated by the PMs in the middle rotor are modulated by the stator and the modulators on the inner rotor respectively. The main harmonics in the three magnetic fields are utilized by the armature windings on the stator. With the unique MFM effect, the performances of the motor are significantly improved. Finally, the prototype is manufactured to verify the effectiveness of the MFM design and the MFM-FMPM motor.

Speaker: Mrs Weiling Pu (jiangsu univeristy school of electrical and information engineering)

MT poster - pwl 1.pdf

MT poster - pwl 1.pptx

214 Mon-Af-Po1.21-06 [93]: Research on the positive airgap harmonics for a flux-modulated permanent magnet motor

Flux-modulated permanent magnet (FMPM) motors have attracted considerable attention due to the predominant torque performance in low speed condition. Recently, the flux modulation principle is always to be developed in diverse PM motors. Intensive study results demonstrate that the harmonics in motor airgap are abundant, and they are essentially the deliverer during the process of the motor energy conversion, which is more important for the FMPM motors. Yet, it is noted that all the harmonics are not exactly playing a driving role for energy conversion. Actually, some of the working harmonics show the negative effects in motor operation. Hence, it can be inferred that analyzing the influence of harmonics on performance objectives and distinguishing its functional effects are necessary and meaningful for achieving high performance FMPM motors. In this paper, the concept of positive and negative harmonics is proposed. The harmonics having the same speed and direction with the Pw-th harmonic (Pw is the number of pole pairs of armature windings) are considered as the positive harmonics, while the opposite case is regarded as the negative harmonics. It is noted that the positive harmonic is beneficial to the improvement of motor performances, and the negative one has the opposite effect. In other words, the more positive harmonics in the FMPM motor, the better performance can be obtained. For extensive investigation, a dual-stator flux-modulated PM (DS-FMPM) motor is selected to analyze the influence of the positive harmonics on the motor performances, the harmonic characteristics of which can be changed by adjusting the relative position between the inner and outer stators. In this paper, three representative cases of the relative positions is studied, where the main magnetic field distribution are in parallel, in series and in hybrid. The electromagnetic performance and the positive airgap harmonics of the three cases are analyzed and compared in detail. Finally, the prototype machine is built to confirm the effectiveness of the design of positive airgap harmonics and the studied DS-FMPM motor.

Speaker: Mrs Min Jiang (Jiangsu univeristy school of electrical and information engineering)

215 Mon-Af-Po1.21-07 [94]: Experimental Verification and Semi-3D Analysis Techniques of BLDC Motor with Permanent Magnet Overhang and Housing-Integrated Rotor Core

Brushless direct current (BLDC) motors have the advantage of power density and low maintenance cost compared to DC motors. DC motors are increasingly being replaced with BLDC motors due to low cost of driving devices and the development of control technology. In particular, outer rotor type BLDC motors have higher power density than inner rotor type BLDC motors since permanent magnets (PMs) can be used more in the former. In this type of BLDC motors, housing-integrated rotor core structure can reduce the radial size by decreasing the thickness of the rotor core due to its three-dimensional (3D) flux path. And BLDC motors with this 3D structure requires 3D analysis for an accurate prediction of their electromagnetic characteristic. Meanwhile, overhang structure is commonly used in ferrite magnets to enhance the effective air-gap magnetic flux; this 3D structure also requires 3D analysis. However, 3D analysis is time consuming, and hence, inefficient for motor design. Therefore, in this paper, we proposes semi-3D analysis techniques using two-dimensional (2D) finite element analysis (FEA), considering the 3D structures of PM overhang and housing-integrated rotor core. First, the PM overhang structure was corrected to a 2D analysis model by equating the amount of magnetic energy to the volume of the PM. In addition, to take 3D flux path of a housing-integrated rotor core structure into account, this structure was corrected to a 2D analysis model by the cross-sectional area in a tangential direction from the definition of the magnetic flux density. Finally, semi-3D analysis techniques taking into account the 3D structures of BLDC motors were performed using 2D FEA and validated by experiments. Detailed discussions and results will be presented in the final paper.

Speaker: Hyo-Seob Shin (Chungnam National University)

MT26th_Poster_HyoseobShin.pdf

216 Mon-Af-Po1.21-08 [95]: Analysis and detection of demagnetization fault of Bearingless Permanent Magnet Slice Motor

A bearingless permanent magnet slice motor(BPMSM) has compact structure and high efficiency, which can realize the rotor magnetic suspension at five degrees of freedom. Bearingless pumps have been established in applications that demand high temperature and corrosion. The extreme environment, especially the high temperature environment, will cause the PM demagnetization fault and so on. As one of the most common faults of permanent magnet motor, permanent magnet losses will cause the motor to be unable to operate normally. Therefore, a permanent magnet flux observer is proposed to ensure the stable operation of the motor.
Firstly, the mathematical model of torque and suspension forces of the BPMSM are deduced. Secondly, the temperature field distribution of the BPMSM is simulated by finite element method, and the temperature rise of the motor is calculated, and the variation law of residual magnetic field of permanent magnet rotor at different temperatures is analyzed. Thirdly, the permanent magnet flux observer is constructed, and the appropriate feedback gain is designed to improve the robustness of the observer. The correctness of the mathematical model and control algorithm are verified by Matlab/Simulink. Finally, the proposed strategy is applied to a 4kW prototype. The experimental results show that the robustness of the system is effectively improved, as well as the dynamic and static performance.

Speakers: Ying Xu (Jiangsu University), Mengyao Wu (Jiangsu University)

Zhang Wei-Poster .pdf

Zhang Wei-Poster .pptx

217 Mon-Af-Po1.21-09 [96]: Design and Optimization of A Novel Axial-Radial Flux Permanent Magnet Machine for Higher Power Density and Lower Cogging Torque

A novel axial-radial flux permanent magnet machine (ARFPMM) is proposed to improve the performance of PM machine. The ARFPMM is capable to reach higher torque density and lower cogging torque than traditional axial and radial PM machine when designed properly. To reach higher performance, T-type SMC core, reluctance rotor, and PM rotor are applied. The T-type stator core is made of soft magnetic composite (SMC) which allows 3-D flux path and plays an important role in both axial and radial flux path simultaneously. As a part of radial flux path, reluctance rotor makes full use of the radial space and produces synchronous reluctance torque. The PM rotor exists as a part of axial flux path and produces PM synchronous torque. 3-D FEM simulation costs significant time for computation. An effective method of decoupling axial and radial flux path is adopted. A 2-D FEM model is built to investigate the influence of two reluctance rotors with different structure. Comparison study is carried out between the two reluctance rotors on average torque and torque ripple. The optimum current phase angle is confirmed for the optimum reluctance rotor. Bidirectional PM skewing technique is applied to reduce the cogging torque. The influence of PM skewing mode, magnet pole-arc ratio, skew angle, and position angle is analyzed and the regularity is confirmed. Based on the analysis above, a response surface methodology (RSM) model is established, and genetic algorithm (GA) is adopt to optimize the cogging torque. A 3-D FEM model is built to verify the validity of RSM and GA. The result shows that the cogging torque is reduced by 90% compared with the initial design. The optimization results show that the ARFPMM can increase output torque by making full use of the axial and radial space. In terms of cogging torque, an optimum combination of magnet pole-arc ratio, skew angle, and position angle can be found using RSM and GA, while the other performance remain nearly invariable.

Speaker: Mr Songjun Sun (State Key Laboratory of Advanced Electromagnetic Engineering and Technology，School of Electrical and Electronic Engineering，Huazhong University of Science and Technology)

2Poster_ARFPMM.pdf

218 Mon-Af-Po1.21-10 [97]: Design of 8p12s IPMSM for Minimization of Electromagnetic Noise and Vibration

The vibration occurring in an electric motor can be largely divided into mechanical vibration due to nonaligned bearings and shafts, and electromagnetic vibration by the electromagnetic force. For existing industrial electric motors, the mechanical vibration associated with the life of the motor was the most important concern. However, in recent years, electric motors—such as the ones used for electric cars and hybrid cars—have high-torque density by using the rare-earth permanent magnet. Thus, the relative importance of electromagnetic noise and vibration is increasing. Electromagnetic vibration and noise affect people emotionally, so it has become very important to reduce vibration when designing a motor.
The electromagnetic vibration can be predicted by analyzing radial force as a vibration source when designing the electromagnetic field of an electric motor. Thus, analyzing the spatial and time harmonics of the radial force enables us to find the harmonic that most influences the vibration. In this study, the optimum design of a 8pole 12-slot IPMSM for vibration reduction was performed. The optimum design was created by analyzing the radial force and finding the design variables that affect vibration. Additionally, to verify the validity of the design results, the results were compared using an electromagnetic-vibro coupled analysis.
In this study, an analysis was made to identify the shape parameters that affect the magnetic flux density of rotor and slot relative permeance in a permanent magnet motor. Using these parameters, optimal design was performed to minimize the vibration velocity in a 8pole 12slot IPMSM initial model. As a result, vibration velocity was reduced by 5.5%. In addition, electromagnetic field-vibration interaction analysis was performed, and thus the results of the optimum design were verified.

Speaker: Won-Ho Kim (Gachon University)

Mon-Af-Po1.21-10 [97] Design of 8p12s IPMSM for Minimization of Electromagnetic Noise and Vibration_장익상.pdf

219 Mon-Af-Po1.21-11 [98]: A Study on the Improvement of the Correction Coefficient Considering the 3D Effect of Spoke Type Permanent Magnet Synchronous Motor

Spoke type Permanent magnet synchronous motors (PMSM), which are superior to other PMSM in terms of output density by maximizing the surface area of permanent magnet (PM), have recently been actively studied. However, spoke type PMSM are magnetically separated by connecting each pole of the rotor core to a magnetically saturated rib or bridge. Therefore, there is a rotor structure in which magnetic potential difference may occur between neighboring poles. The magnetic potential difference between the rotor poles of such a spoke type PMSM induces leakage flux in the direction of the rotor axis. Since the leakage flux in the rotor axial direction has a component in the z-axis direction, this can be taken into consideration only through 3D analysis. This makes it difficult to analyze the performance of spoke type PMSM. Several studies have been conducted on the 3d leakage magnetic flux of the spoke type PMSM. However, in the previous studies only the axial leakage magnetic flux between the poles of the rotor was taken into consideration, and the linkage magnetic path between the rotor pole and the stator shoe via the axial direction was neglected. In this paper, we have further investigated the correction coefficient of spoke type PMSM which further improve the accuracy of 3d leakage paths as well as 3d linkage ones.

Speaker: Sung Gu Lee (Busan University of Foreign Studies)

MT26_Mon-Af-Po1.21-11 [98].pdf

MT26_Mon-Af-Po1.21-11 [98].pptx

220 Mon-Af-Po1.21-12 [99]: Design and Analysis of A Partitioned-Rotor and Staggered-Stator Hybrid Excited Flux Switching Permanent Magnet Machine for Hybrid Electric Vehicles

Nowadays, hybrid electric vehicles (HEVs) have been employed and developed extensively for promoting the rapid development of resource-conserving and environment-friendly society. Due to the multi-mode operations of the HEVs, the high integrated electric drive system with the motors which features the high torque density, high efficiency, and wide speed range are becoming the main trend in the HEVs. In this paper, a partitioned-rotor and staggered-stator hybrid excited flux switching permanent magnet（PS-HEFSPM）motor is proposed for hybrid vehicles, in which the air-gap field can be easily controlled.
The PS-HEFSPM motor consists of 12-stator and 10-rotor poles, in which the NdFeB permanent magnets and the DC field windings both serve as magnetic excitation sources. The partitioned rotor consists of two parts of inner and outer portion, which are connected together by an end disc to realize the same operating speed. The adoption of this unique partitioned rotor configuration effectively obtains the high torque density and avoids the stator flux leakage. Furthermore, the staggered stator of the proposed motor includes two salient pole parts staggered at a certain angle on the circumference, as well as the 12-rectangular magnetic bridges which connect the two salient pole parts in radial direction. The merits of this new stator structure are forming series magnetic circuit which runs through two rotors smoothly and creating space for the field windings which are wound around each rectangular magnetic bridge to fulfill the flux-adjusting function by controlling and changing the polarity and amplitude of the field current.
Firstly, the operation principle of the PS-HEFSPM motor is introduced and the initial design parameters are given. Then, in order to improve the flux regulation capability of the motor, the leading parameters are optimized by multi-objective optimization method. Moreover, the basic electromagnetic performances including back-EMF, torque, as well as torque–speed and power–speed characteristics are analyzed by 2D-FEA. Thereafter, it shows that after the targeted optimization design, the flux regulation capability reaches a high level, which meet the application requirements.

Speaker: Mrs Xue Zhou (jiangsu university school of electrical and information engineering)

221 Mon-Af-Po1.21-13 [100]: Design of New Novel Shape Rotor by Inductance Changes for Power Improvement and Extended Operating Range

This study shows the novel rotor shape of the spoke-type PMSM for a washing machine to improve power and widen operating range by changes of inductance in the rotor and air gap. Applying a new shape to the rotor results in an inductance change in some areas of the rotor in which low magnetic flux density existing, which in turn changes the magnetoresistance in the air gap. As the inductance changes, the inductance of the rotor d-axis decreases and the q-axis inductance increases to improve the reluctance torque. We investigated to maximize the reluctance torque and air-gap magnetic flux density with a novel rotor shape. In other words, low magnetic flux density area which help rarely torque increase was subtracted. In addition, it also can extend operating range as the saliency is maximized. The Finite Elements Method analysis results show that the back-electromotive force decreases as the saliency increases. As a result, the maximum speed range of the designed motor can be widen and it is applicable to the motor requiring high speed range. For instance, washing machine needs high speed motor in dehydrating mode to remove moisture from clothes.
It is contrast to the common technologies that increasing coil turn for power improvement results in increasing back-electromotive force. Accordingly, it was confirmed that average torque improves as some area of rotor where magnetic flux density is low, was removed. A prototype has been manufactured and is now being under experiment. The results of power improvement and operating range widened will be compared and verified.

Speakers: Hyungkwan Jang (Hanyang University), Mr Seung Heon Lee (Hanyang University)

MT26_포스터_장형관.pdf

Mon-Af-Po1.22 - Motors IV

Conveners: Kyeongdal Choi (Korea Polytechnic University), Vicente Climente-Alarcon (University of Cambridge)

222 Mon-Af-Po1.22-01 [101]: Comparison of Different Stator Winding Structures on Rotating Performance of Fully High-Temperature Superconducting Induction/Synchronous Motor

Our group has been conducting various studies of high-temperature superconducting induction/synchronous motor (HTS-ISM) for next generation transportation equipment. The HTS-ISM has various advantages, such as co-existence of synchronous and slip rotation modes, high efficiency for variable speed control, high torque density. For the HTS-ISM with copper stator winding, the torque density and efficiency are limited, because of limited current density and large copper losses. In order to achieve higher torque and efficiency, the fully HTS-ISM with superconducting stator winding should be developed.
In this paper, different stator winding structures of a 50kW fully HTS-ISM are studied and compared. Since the distributed winding is difficult to be realized, due to the limitation of bending diameter and mechanical strength of HTS tapes, the conventional concentrated winding and proposed toroidal winding are compared. Firstly, the current transport property of the HTS tape based on the different flux density is measured. Finite Element Analysis (FEA) simulations with different winding structures are performed. The results show the toroidal winding can achieve higher torque and lower torque ripples. Moreover, because of the magnetic mirror image effect, the perpendicular component of flux density HTS tape for toroidal winding is much lower than that of conventional concentrated winding. It demonstrates that the toroidal winding can improve the current transport property of HTS tapes. The detailed results will be shown and discussed.

Acknowledgements:
This work has been supported by Japan Science and Technology Agency under the program of Advanced Low Carbon Technology Research and Development Program (JST-ALCA) in Japan.

Speaker: Dr Liangliang Wei (Kyoto University)

Poster-Comparison-0920.pdf

223 Mon-Af-Po1.22-02 [102]: Design and Evaluation of Prototype High-Tc Superconducting Linear Synchronous Motor for High-speed Transportation

Due to the high thrust density and operational speed, superconducting linear synchronous motor is considered a favorable propulsion system for high-speed ground transportation. Korea Railroad Research Institute (KRRI) has researched on high-Tc superconducting linear synchronous motor (HTS LSM) to develop new high-speed transportation of which speed is over 500 km/h. As a feasibility study for HTS LSM, we developed a small-scale prototype HTS LSM and evaluated its operational performances. The design scheme of prototype was focused mainly on testing the thrust performance of HTS LSM. The HTS electromagnet consists of 2-pole HTS coil, which was developed with GdBCO tape in single cryostat vessel. To enhance self-quench protection, the HTS coils were fabricated with non-insulated windings. The rating magneto-motive force of each HTS coil was designed to be 320 kAt at the operating temperature of 20 K. And the prototype was designed to generate about 3 kN in the maximum thrust at the given operating condition. We confirmed these performances by carrying out static operational tests. This paper describes design process, fabrication and evaluation results of the prototype HTS LSM.

Speaker: Dr Chang-Young Lee (Korea Railroad Research Institute)

MT26-Mon-Af-Po1.22-02[102].pdf

224 Mon-Af-Po1.22-03 [103]: Development of a New Axial Flux Machine with the Ability of Mechanical Flux Weakening

Axial flux permanent magnet machines (AFPM) are being increasingly used in a great of industrial applications e.g. the electrical vehicle and wind generators, due to its very compact structure and high torque density. The single stator and single rotor configuration is the basic structure of axial flux machine. For AFPM the fractional slot concentrated winding and surface mounted PM structure is normal adopted. To increase the speed adjust range of AFPM, a new mechanical flux weakening adjuster is proposed in this paper. In additional to the traditional stator core and rotor core, the proposed new mechanical flux weakening adjuster is located on the outside of the stator core. The mechanical flux weakening adjuster can be rotated with a determined degrees, and the main magnetic flux can be adjusted. The operation principle of proposed AFPM is similar to the traditional AFPM and the only difference is the adopted mechanical flux weakening ability. Compared with the traditional flux weakening method, the inductance can be regulated as well during the main magnetic flux adjusts process in this new AFPM. As a example, when the d-axis current equals zero method is used in this machine, then the more torque can be achieved when it operates in the high speed range. In this paper, the operational principle has been explained and the power equation has been deduced for the initial dimension design. The main dimension of the machine will be optimized to achieve higher output torque and wider constant power adjust range. The main parameters and performance will be calculated by using the finite element method (FEM).

Speaker: Dr Chengcheng Liu (Hebei University of Technology)

225 Mon-Af-Po1.22-06 [104]: Influence of architecture of composite superconducting tape-based stacks on AC demagnetization for electric machines application

Superconducting tape-based stacks used as trapped magnetic flux magnets in electrical machines are subject to an AC-demagnetizing field. This study provides analysis of trapped flux and demagnetization of several stacks’ architectures for electrical machines applications. This work is an application-driven enhancement of a previous study on stacks architecture in regards of trapped flux profile and uniformity for applications requiring uniform magnetic field over a large area [1,2].
The trapped field and demagnetization of several stacks’ architectures made of SuperOx tapes were investigated. Using the same magnetizing field and the same number of tapes, rearranging the architecture of stacks was found to have an effect on the current density distribution, the trapped flux and the demagnetization. The electromagnetic time-dependent finite element model has been used; the latter implements the power law that takes into account field dependency of the superconductor critical current density and the power law exponent, n, at liquid nitrogen temperature interpolated from experimental characterization data.
Experimental measurements on some of the modeled architectures have been carried out to check the viability of the numerical models.

[1] T. B. Mitchell-Williams, A. Patel, A. Baskys, S. C. Hopkins, A. Kario, W. Goldacker, B. A. Glowacki, Towards Uniform Trapped Field Magnets Using a Stack of Roebel Cable Offcuts IEEE Transactions on Applied Superconductivity, 26 (3) 6800404 (April 2016)

[2] T B Mitchell-Williams, A Baskys, S C Hopkins, V Kalitka, A Molodyk, B A Glowacki and A Patel, Uniform trapped fields produced by stacks of HTS coated conductor tape, Superconductor Science and Technology, 29 (8) 085008 (16 June 2016)

Acknowledgements to:

This research is financially supported partially by the European Union’s Horizon 2020 research innovation programme under grant agreement No. 7231119 (ASuMED “Advanced Superconducting Motor Experimental Demonstrator”) and also by EPSRC grant No. EP/P000738/1 entitled “Development of superconducting composite permanent magnets for synchronous motors: an enabling technology for future electric aircraft”.

Speaker: Dr Anis Smara (ASCG, Department of Materials Science & Metallurgy , University of Cambridge)

SMARA ANIS MT26.pdf

226 Mon-Af-Po1.22-07 [105]: A Novel Flux Reversal Claw Pole Machine with Soft Magnetic Composite Cores

Flux reversal permanent magnet machine (FRPMM) is a special kind of permanent magnet machine with the permanent magnet (PM) installed on the stator side and there is no winding or PMs on the rotor side. Claw pole machine (CPM) is a special kind of transverse flux machine (TFM), with the adopted claw pole teeth, the torque ability and power factor of CPM can be even higher than those of TFM. Combing above two machines, this paper proposes a novel flux reversal claw pole machine (FRCPM) with soft magnetic composite (SMC) cores, the proposed FRCPM has both the advantages of flux reversal permanent magnet machine (FRPMM) and claw pole machine (CPM). Specifically, with the permanent magnets (PMs) are surface mounted on the surface of stator claw pole teeth with a determined pattern, the FRCPM can operate based on flux reversal principle. As the adopted winding is global ring winding and 3D magnetic flux stator core structure is similar to the CPM’s, the FRCPM is operated based on magnetic flux characteristic of the CPM as well. Therefore, the FRCPM can be operated under relatively high rotate speed since there is no winding or PMs on rotor, and the weak PMs, ring winding and SMC stator cores are encapsulated together as a whole part. Moreover the adopted 3D magnetic flux path can bring FRCPM with relatively high torque ability, and the adopted SMC cores can bring FRCPM with low core loss at the high speed operation. The operation principle of FRCPM is explained, the power equation is deduced for obtaining the initial design, and the main dimensions are optimized to ensure the developed FRCPM can have good performance. The main electromagnetic parameters and performance of FRCPM are obtained based on using the 3D finite element method (FEM).

Speaker: Dr Chengcheng Liu (Hebei University of Technology)

MT26 Poster FRCPM(1)(1).pdf

MT26 Poster FRCPM(1)(1).pptx

227 Mon-Af-Po1.22-09 [106]: Active Magnetic Equivalent Circuit Analysis Method Considering Magnetic Saturation for Delta Typed Interior Permanent Magnet Traction Motor

The objective of this paper is an analysis method for traction motor which targeting to electric bus and trailer. The type of the studied motor is IPMSM(Interior Permanent Magnet synchronous motor) which has delta type magnet topology of the rotor. It is possible to maximize reluctance torque and output characteristics by arranging the permanent magnet arrangement of the rotor in delta shaped.
Conventionally the two main methods for analyzing electrical machines include magnetic equivalent circuit(MEC) and finite element method(FEM). Whereas FEM is a very accurate yet computationally expensive method, the MEC method has the advantage of faster calculation speed and more feature variables can be considered. Therefore, it can be combined with optimal design algorithms. However, its main disadvantage is the poor accuracy of characteristics analysis as there are many considerations when using MEC method.
Because IPMSM operates in magnetic saturation region, the magnetic saturation characteristics of the iron core are nonlinear and the change in operating current is significant. In addition, because it is a method of expressing a motor with a few lumped constant circuit, there are many errors and more circuit constant or correction factors should be used to solve them. For the above reasons, it is difficult to analysis the motor using the conventional MEC method. To compensate for the inaccuracy of the conventional MEC method without taking into account the magnetic saturation, this paper will show an active MEC analysis method which actively changes according to saturation conditions. It will be implemented as an active function to segment the magnetic equivalent circuit in the rotor’s saturated area into variable resistance, so that it is actively set up according to the load. This will allow to increase accuracy and reduce costs and time. Method will be verified by comparison with FEM and conventional MEC method.

Speakers: Dongkyu Lee (Chung Ang University), Prof. JongSuk Ro (Chung Ang University)

Analysis and Design of Universally Applicable Traction Motor for Heavy-Duty Vehicles.pdf

228 Mon-Af-Po1.22-10 [107]: Presentation withdrawn

229 Mon-Af-Po1.22-11 [108]: Design and Analysis of a Novel Low-Speed and High-Torque Synchronous Motors with PM and Reluctance Hybrid Rotor

Low-speed and high-torque permanent magnet motors (LSHT-PMM) are widely used in many industrial fields. Due to the inherent characteristics, the outer diameter of the LSHT-PMM is large. Therefore, in order to make full use of the internal space of the motor, a double stator structure is proposed in this paper. In order to reduce the amount of permanent magnets (PMs) and reduce the cost, a PM and reluctance hybrid rotor is proposed. The proposed hybrid rotor structure is a combination of a magnetic barrier reluctance rotor and a permanent magnet rotor which are embedded on the inner and outer sides of the magnetic isolation ring respectively. The proposed rotor not only has the advantages of a PM assisted reluctance rotor, but also makes the design method more flexible due to the structures of PM and magnetic barrier reluctance relatively independent. In this paper, the electromagnetic design method of the proposed LSHT-PMM is studied in detail. Firstly, in order to determine the stator design, the different winding connection modes, slot-pole combination and winding distribution of the inner and outer stators are compared and analyzed. Secondly, in order to design the novel rotor, the influence of the relative position between the magnetic barrier and the PM, the shape of PM, the width and the number of the magnetic barrier rotor on the electromagnetic performance of the proposed LSHT-PMM are studied based on the field-circuit coupling method. Finally, the correctness and rationality of the designed motor are verified by the simulation and experiment. This work is supported by the National Natural Science Foundation of China under Grant 51877139.

Speaker: Fengge Zhang (Shenyang University of Technology)

Mon-Af-Po1. 22-11.pdf

230 Mon-Af-Po1.22-12 [109]: Analytical and Experimental Study of Multiphysics on Starting of a 50 kW Class Fully HTS Induction/Synchronous Motor and Its Variable Speed Controllability

Our group has been developing a High Temperature Superconducting Induction/Synchronous Motor (HTS-ISM) for highly efficient transportation equipment. So far, the 20 kW class prototype, which consists of BSCCO rotor and copper stator, has already been developed and shown its excellent characteristics based on experiment and analysis. Furthermore, the 50 kW class model, in which both the rotor and the stator are made of BSCCO superconducting tapes, has been fabricated, and various characteristics have been evaluated.
In order to realize a practical HTS-ISM drive system, not only the HTS-ISM but also peripheral devices such as an inverter and a refrigerator must be investigated. Furthermore, the cooling characteristics during drive condition is really important.
In this paper, we have developed a multidisciplinary analysis method which couples the nonlinear voltage equation, the motion equation and the thermal equivalent circuit. We performed a multidisciplinary analysis for starting and variable speed controllability of a 50 kW class fully HTS-ISM. We consider the standby mode temperature (stationary mode) at 110 K and drive temperature (operation mode) at 80 K. We showed that the nonlinear resistance of HTS stator winding should be considered in the voltage equation to express exact performance of the HTS-ISM. We also clarified there exists optimal waiting time before motor operation when the cryocooler is in higher temperature stand-by mode. These results would be very important for the achievement of highly efficient HTS-ISM system for transportation equipment.

Acknowledgements:
This work has been supported by Japan Science and Technology Agency under the program of Advanced Low Carbon Technology Research and Development Program (JST-ALCA) in Japan.

Speaker: Masaya Okuno (Kyoto University)

Mon_Af_Po1_22_12_109_Okuno.pdf

Mon-Af-Po1.23 - Transformers

Conveners: Dr Sergey Fetisov (Russian Scientific R&D Cable Institute), Roberto Zanino (Politecnico di Torino)

231 Mon-Af-Po1.23-01 [110]: Temperature Change Effects on No-Load Loss Characteristics of Amorphous Alloy Cores

Transformer is important in power system. No-load loss and apparent power of amorphous alloy transformer core change obviously with temperature. Moreover, the inner temperature varies in large scale. At present, little research has been done on no-load loss of amorphous alloy cores with temperature change. Therefore, it is very important to study the no-load loss at different temperatures.

Temperature Change Test

In this paper, three amorphous alloy cores of different strips are designed and manufactured based on measuring platform and scaled-down transformer core model. Measurements were carried out in the same temperature control box within range of 10-110℃. Measurements were made every 10℃from 10 ℃. When the inner box temperature reached set temperature and it was maintained stable for 10 minutes, measurements were then made after internal temperatures of amorphous alloy cores were in consistence with externals. The no-load loss and apparent power were measured respectively within 0.05T-1.4T magnetic density, meanwhile, the induced voltage and excitation current waveform were recorded.

Conclusion

Temperature changes may have certain effects on loss characteristics of the three types of amorphous alloy core models. When magnetic density is not saturated, as core temperature increased, the active power loss decreases by 6%-10%, and the apparent power will be reduced by about 5%. Within standard-operating magnetic density, as core temperature increases, the active power loss of core decreases by 4%-5%, while the apparent power increases by 4%-7%. When the magnetic density is supersaturated and the temperature rises, the active power loss is basically unchanged, at this point, an irregular state emerged. However, the apparent power will increase by more than 50%. Hence, the temperature change has evident effects on apparent power of amorphous alloy cores under supersaturated magnetic density.

Speaker: Prof. Huiqi Li (Department of Electric Power Engineering, North China Electric Power University)

232 Mon-Af-Po1.23-02 [111]: Design and Analysis of 6.9/1.0 kV-10 MVA Lightweight Superconducting Transformers with REBCO Coated Conductors

Fully turboelectric propulsion systems with lightweight and high power density are one of the solutions to realize future electric aircrafts. Our research group started to develop 10 MW fully superconducting synchronous generators and 2 MW motors. In this system, we designed so that the generators supply electric power at the voltage of 6.9 kV, however, the motors operate at the low voltage of a few kV. Therefore, a 6.9 kV-10 MVA step-down transformers with lightweight are required for this system. In our previous studies, a 66/6.9 kV-20 MVA superconducting transformer with REBCO superconducting tapes was developed. The low AC loss was realized by using multifilamentary REBCO tapes which were made by laser-scribing technique and parallel conductors in which REBCO tapes were stacked and transposed. The target of this study is to realize superconducting transformers with a power density over 20 kW/kg. Firstly, the structure of the superconducting transformer was assumed as an inner iron double concentric windings type. When one-turn voltage is 23 V/turn, the three-phase superconducting transformer becomes the most lightweight design of around 200 kg. Next, the optimum transposition patterns for parallel conductors which were applied to the windings were investigated to realize uniform current distribution among the tapes and low AC loss. The AC loss was calculated by using JMAG (electric instrument analysis software of JSOL). The detailed properties and design specifications of superconducting transformers will be reported in this conference.
Acknowledgement
This research was partially supported by the New Energy and Industrial
Technology Development Organization (NEDO), the Japan Science and
Technology Agency (JST): Advanced Low Carbon Technology Research and
Development Program (JPMJAL1405) and the Japan Society for the Promotion
of Science (JSPS): Grant-in-Aid-for Scientific Research (JP18H03783 and
JP17H06931).

Speaker: Goki Kawasaki (Kyushu University)

233 Mon-Af-Po1.23-03 [112]: Assessment of Dielectric Breakdown Characteristics of Nomex Paper under High Frequency Overvoltages for Superconducting Power Transformer Application

Insulation materials have different electrical characteristics according to temperature and voltage frequency. These characteristics are very significant factors for the insulation design of high voltage power apparatus. Since there are not always consistent overvoltages, it is necessary to ensure the dielectric strength against various overvoltages. In particular, high voltage power transformers can be exposed to overvoltages of very high frequency components caused by external switching operations and lightning strokes, which can lead to dielectric breakdown. In addition, in order to develop a superconducting power transformer, the insulation characteristics of material for these overvoltages should be reliable in a cryogenic environment. However, researches on non-standard impulse overvoltages are limited. In this paper, lightning and switching impulse dielectric breakdown experiments were performed to analyze the effect of overvoltage frequency on dielectric strength. In order to make different oscillation frequencies of the impulse overvoltages, the front time was set differently by adjusting resistors of impulse generator. Nomex paper used as conductor insulation for power transformer were tested in liquid nitrogen using two electrode types. Uniform electric field electrodes are composed of two same cylinder shaped materials. Turn to turn electrodes were composed of varying the number of Nomex paper layers. The difference of dielectric breakdown characteristics between lightning and switching impulse was analyzed by varying the front time and oscillation frequency. From the experiments, we have confirmed that the insulation properties of dielectric material are different depending on the type of front time, oscillation frequency and overvoltage source.

Speaker: Mr Sun-Jin Kim (Hanyang University)

MT26_Mon-Af-Po1.23-03 [112].pdf

234 Mon-Af-Po1.23-04 [113]: A New Residual Flux Measurement Method in the Power Transformer

Residual flux of the power transformer will accelerate the magnetization saturation of transformer core and generate high transient inrush current. Generally, the peak value of inrush current generated by residual flux in the core can reach 6-8 times of the rated current, which endangers the mechanical stability and insulation strength of the power transformer windings and destroys the normal operation of the power system. Therefore, the study of residual flux in the power transformer has considerable significance, especially when the residual flux cannot be directly measured. The point-on-wave control methodology is proposed to control switching for the re-energization of a transformer. However, this method does not accurately measure the residual flux, and the switch-on instant is difficult to control. Another method uses the fluxgate sensors to measure the residual flux in real time, but this method is costly and has errors brought by the additional fluxgate sensors.

To overcome the shortcomings of the existing methods, this paper proposes a method for analyzing and detecting the residual flux, based on the nonlinear magnetizing characteristics of the core. A model of single power transformer core is built to simulate transients in MAGNET software. By analyzing the transient current of the measured coil under applying positive and negative DC voltage to the measuring coil of the toroidal transformer, the direction of residual flux can be determined and the relationship between residual flux density and the magnetizing transient current can be obtained. Finally, the experimental results show that the proposed method can effectively determine the direction and accurately measure magnitude of the residual flux. According to the measured magnitude and direction of the residual flux, the demagnetization data of the toroidal transformer is set to effectively weaken the residual flux and reduce the inrush incurrent.

Speaker: Dr Chengcheng Liu (Hebei University of Technology)

MT huocailing 20190918.pdf

MT huocailing 20190918.pptx

MT huocailing 20190918.pptx

235 Mon-Af-Po1.23-05 [114]: Performance Evaluation of Conductor on Round Core Cables Used in Superconducting Fault Current Limiting Transformer

Conductor on Round Core (CORC®) cables with scalability, flexibility, strong mechanical strength and high current density are of large potential for different power applications. In this paper, CORC® Cables are proposed to be the secondary winding for superconducting fault current limiting transformer (SFCLT). In order to evaluate the working performance of CORC® cable in SFCLT, firstly, a 60cm-long CORC® short sample is fabricated, fundamental parameters including self-field critical current and room temperature resistance are measured by experiments. Then, so as to represent the real working condition, both rated current tests and overcurrent tests are carried out to the CORC cable, respectively. In rated current test, AC loss and current uniformity are used as key parameters to evaluate the performance, discussions are investigated by both experimental and numerical method. Meanwhile, in overcurrent tests, the recovery-under-load (RUL) capability is used an important evaluation parameter. Because the RUL capability shows the uninterruptible power ability of the power system with SFCLT. Conclusions obtained in this paper can verify the feasibility of this technique and also provide useful information for future SFCLT applications.

Speaker: Ms Wenrong Li (Shanghai Jiao Tong University)

Mon-Af-Po1.23-05-liwenrong.pdf

236 Mon-Af-Po1.23-06 [115]: Winding Design and simulation of a 120kVA/6kV single-phase HTS transformer

Abstract: Based on the finite element method (FEM), a simulation model of a single-phase HTS transformer was established according to a developed HTS transformer, and the simulation results are in good agreement with the experimental data. On this basis, a 120kVA/6kV single-phase HTS transformer was designed, the primary windings were solenoid coils consisted of 8 helically wound layers, and the secondary windings were consisted of 13 double pancakes connected in parallel with 9 layers. The current distribution in windings, magnetic field and stress analysis under rated working condition and in fault were simulated. The results are important to the design of HTS transformer.
Keywords: HTS transformer, wingding, current distribution, magnetic field, stress

Speaker: Tengyan Wang

poster 王腾岩.pdf

237 Mon-Af-Po1.23-07 [116]: AC loss calculation on a 6.5 MVA HTS traction transformer with hybrid winding structure

Traction transformers are key components for the Chinese high speed train system, and it is hoped that a superconducting version will replace oil-based conventional transformers in this application. Since 2018 Beijing Jiaotong University has been leading a six partner project, funded by the Chinese Ministry of Science and Technology (MOST), to develop a 6.5 MVA HTS traction transformer. The transformer consists of four single-phase 25 kV/1.9 kV HTS windings, operating at 65 K, each of which drive a motor. The rated currents for each of the HV (high voltage) and LV (low voltage) windings are 63 A and 846 A, respectively. The HTS transformer should demonstrate improved performance, achieving 99% efficiency and 3 tonne total system weight. Minimization of AC loss in the HTS windings is critical to achieve both efficiency and weight targets; the weight of the cooling system scales directly with AC loss.
Despite this improved performance, the cost of the HTS windings is critical for commercialization of the HTS traction transformer technology. Wire costs can be minimized without significantly increasing AC loss by using hybrid windings: the end-part of the windings is wound with high-cost and high-performance wire/Roebel cable; the central part of the windings is wound with low-cost and low-performance wire/Roebel cable.
We report H-formulation 2D axisymmetric FEM AC loss simulation results on hybrid structure HTS windings with both HV and LV windings wound with REBCO coated conductors. The simulation uses measured Jc(B) curves at 65 K for each conductor. The HV windings utilize 4 mm coated conductors and LV windings utilize 8/5 Roebel cables assembled using Roebel strands from 12 mm conductors. Both windings have a hybrid structure in order to reduce the wire cost. Flux diverters are placed at the end of the windings to reduce AC loss. AC loss values in the HTS transformers with the hybrid structure are compared with HTS transformers with non-hybrid structures and the feasibility of the hybrid winding structure is discussed.

Speaker: Zhenan Jiang (Victoria University of Wellington)

Mon-Af-Po1.23-07 -final.pdf

238 Mon-Af-Po1.23-08 [117]: Residual Flux Measurement and Reduction in the Single-phase Power Transformer

When a large power transformer is switched on, the residual flux in the iron core may cause inrush current, which may cause the transformer to no longer be put into operation, thus affecting the continuity of power supply in the power grid. However, the traditional methods can only estimate the residual flux. It is impossible to effectively weaken the residual flux. Therefore, the study of residual flux in the closed magnetic core of a power transformer has considerable significance.
This paper describes a novel method for analyzing and detecting the residual flux, based on externally applying multiple positive and reverse excitation. This method can accurately measure the residual flux of iron core without damaging the transformer itself and can be extended to the residual flux analysis of three-phase transformer.
A model of single phase transformer core is built to simulate transients in COMSOL software .Under the same residual flux, different current responses will be generated when the external positive and reverse excitation is applied. Under different residual flux, different current responses will also be generated when the same external excitation is applied, the experimental results show that the proposed method can effectively determine the direction and accurately measure magnitude of the residual flux. Moreover, according to the measured magnitude and direction of the residual flux, the demagnetization data of the transformer is set to effectively weaken the residual flux.
Measurements of residual flux for a simple laboratory setup verified that the simulation gave reasonable values.

Speaker: Ms Ziwei Zhao (Hebei University of Technology)

239 Mon-Af-Po1.23-09 [118]: Fault Current Limiting Characteristics of Three Phase Transformer Type Superconducting Fault Current Limiter using Two Insulated Secondary Circuits

This paper is a the fault current limiting characteristics of superconducting fault current limiter due to three phase ground fault in power system.
In this system, two superconducting elements are connected to a-phase and c-phase respectively, and a transformer type superconducting fault current limiter is proposed to limit the fault current in case of a ground faults.
In order to measure the fault current limiting characteristics of the proposed superconducting fault current limiter, b and c phases were connected and short - circuit simulations were carried out using the quench characteristics of the superconducting elements.
we compared and analyzed the peak current and the instantaneous power load characteristics with the integrated three phase superconducting fault current limiter.

Speaker: Prof. Tae-Hee Han (Jungwon University)

190922_MT26_Mon-Af-Po1.23-09_ThreePhaseTr_SFCL.pdf

240 Mon-Af-Po1.23-10 [119]: Current Limiting Characteristics of Three-Phase Transformer Type Superconducting Fault Current Limiter According to Secondary Winding Methods

The distributed power generation has increased due to the development of the electric power industry and the active generation of renewable energy. This causes a large increase in the fault current when fault occurs, which exceeds the capacity of the existing protective device. Thus it creates a risk of shutdown failure. The superconducting fault current limiter (SFCL) has been demonstrated by previous studies that one of the effective methods to limit the fault current. Installation of the SFCL is expensive, but it is more reasonable than replacement of existing protective equipment.
In addition, the superconducting fault current limiters studied in many cases are often designed as single phase, and when applied to three phases, three single phase superconducting fault current limiters are installed. In this case, at least three superconducting modules are required.
In this paper, the double quenching SFCL using E-I three-phase transformer core is proposed. The proposed superconducting fault current limiter is designed as three phases and has a similar fault current limiting effect to that of existing superconducting fault current limiters by using a small number of superconducting modules compared to existing ones. The primary side of the three-phase transformer is connected in series with the power system, and the secondary side is connected to the superconducting module. In the fault case, the single-quenching or double-quenching operation is performed depending on the magnitude of the fault current. In this paper, the operation characteristics of the proposed double quenching SFCL using E-I three-phase transformer core are analyzed through the experiments.

Speaker: Prof. Sung-Hun Lim (Soongsil University)

241 Mon-Af-Po1.23-11 [120]: HTS Coil Structure Suitable for High-Power Transmission in a Short-Time in Wireless Power Transmission System for Railway Vehicle

A Wireless Power Transmission (WPT) system for a railway vehicle has been investigated to reduce the greenhouse gas emissions in a diesel vehicle. However, the WPT system is required to transmit the electric power of several hundred kW in a short time while the railway vehicle is stopping at a station. Since there are power converters and control devices under the floor of the railway vehicle, the coil space for the WPT system is limited. Therefore, when high power is transmitted to the coils installed in a limited space, eddy current loss generates in the coils and rails, and a long time coil operation becomes difficult due to the coil heat generation. Therefore, it is required to reduce the losses in the coil and the rails and lower the operating frequency. Since a copper coil using Litz wire has low current density, it is difficult to increase the number of turns of the coil in the limited space. Since the quality factor of the copper coil decreases with decreasing the operating frequency, it is difficult to suppress the coil heat generation by decreasing the operating frequency. Therefore, we investigated an HTS coil structure suitable for high-power transmission in a short-time in a WPT system. A high-quality factor was obtained in the WPT system using the HTS coils even at the frequency region around 1 kHz. It was found that the reduction of the current load factor was particularly important for the high-power transmission in a short time because the AC loss in the HTS coil strongly depended on the current load factor. Considering this point, we were able to realize the high-power transmission in a short-time at the low-frequency region around 1 kHz in the WPT system with the HTS coils composed of parallel conductor with wide tapes.

Speaker: Ryota Inoue (Tohoku University)

Mon-Af-Or4 - Resistive and Pulsed High Field Magnet I

Conveners: Mark Bird (FSU), Anbo Wu (GE Global Research)

242 Mon-Af-Or4-01: Conceptual Design Optimization of a 60 T Hybrid Magnet

45 T is the highest continuous magnetic field available to the scientific user community, and this now since practically 20 years. We address the question of how to access the next level, defined as 60 T, with a hybrid magnet. The outsert, wound from low-temperature superconductors (LTS) will generate the highest field possible: 18 - 20 T in a 1 m bore. For the inner part, two approaches are investigated: a high-power resistive magnet or a combination of a resistive insert magnet and a “midsert” magnet employing high temperature superconductors (HTS). First rough estimates suggest equal field contributions of 20 T from the LTS outsert, HTS midsert and the resistive insert. We have then investigated of how to optimize dimensions and field contributions from the three subsystems under the primary constraint of actual feasibility and investment cost. Additional constraints are: a) current density and stress levels of the outsert conductor including its reinforcement, b) conductor and coil winding options and their maturity confidence for the midsert and c) stress level, power density, and available power for the insert. For insert and outsert a large basis of experience exists, from which reasonable extrapolations can be made with sufficient certainty. This is not the case for the HTS coil, where important decisions have to be justified, such as conductor type and its reinforcement, nature of insulation and winding techniques. Conductor cost reduces in our optimization routine the HTS contribution to a minimum; however, progress in HTS magnet technology and projected cost reductions are impressive and included in our estimations. The results of our detailed magnet design and optimization calculations indicate that it is feasible to build a 60 T hybrid magnet of rather compact dimensions with a maximum total magnet height of 1.3 m and an outer diameter of only 1.8 m. Distinct, feasible developments of the HTS and LTS conductors and resistive magnet technology have been defined. We propose a novel method, the fast ramp-down of the resistive insert, to safely protect the HTS midsert by quenching it globally and instantaneously.

Index Terms— Very high field magnets, Hybrid magnet, Large bore LTS and HTS magnets, Resistive magnets.

Speaker: Dr Hans J. Schneider-Muntau (CS&T)

16 Conceptual Design Optimization of a 60 T Hybrid.pdf

243 Mon-Af-Or4-02: Preliminary Analysis on the Failure of a 100 T pulsed magnet at the WHMFC

A 100 T pulsed magnet of triple coils was developed in WHMFC in 2018, the outer coil was powered by a 100MJ/100MW pulsed generator, and the middle and inner coils are energized by capacitor banks. The inner and middle coils are made of CuNb wire, and copper wire for the outer coil, the outline size of the magnet is 800 mm in O.D. and 1200mm high. The magnet failed at about 83 T during test, however, the magnet does not blow up and still remain intact after failure. All the current of the positive and negative ends for the three coils were measured, the experimental results show that the current of the positive end does not equal that the negative end for both middle coil and outer coil, and the difference between positive and negative ends of middle coil equals that the difference of both ends of the outer coil. This means electrical breakdown happens between the middle coil and outer one in lateral direction. It was found that indeed there was a breakdown path between the outmost layer of middle coil and the inner-most layer of outer coil after the magnet being disassembled and cut open. Moreover, many places of the windings of middle coils were burned and some part of windings fractured, and windings even penetrated into the reinforcement in some place. The magnet broke in a relative low field, and the stress may not be the primary reason. The reasons for the magnet failure are complicated, it may be the overvoltage, or defective conductor and structural instability like buckling, and all this will be discussed in this paper.

Speaker: Houxiu Xiao

presetation-xiao2.pdf

presetation-xiao2.pptx

244 Mon-Af-Or4-03: Pulsed-Magnet Developments at the Dresden High Magnetic Field Laboratory

The Dresden High Magnetic Field Laboratory (HLD) is a pulsed-field user facility which provides external and in-house researchers with the possibility to perform a broad range of experiments in pulsed magnetic fields [1]. Being a member of the European Magnetic Field Laboratory (EMFL), HLD receives more than 100 scientific proposals annually.
The Dresden High Magnetic Field Laboratory operates ten experimental chambers equipped with a variety of pulsed magnets energized by two independent, modular capacitor banks with maximum stored energies of 50 and 14 MJ at 24 kV maximum operational voltage. The pulsed magnets at the HLD are subject of permanent improvements in terms of peak field, reliability, noise level, cooling time, and longevity. Detailed analysis of the magnet performance and failure scenarios are provided in this work for various pulsed magnets operating between 65 and 95 T. Furthermore, we present a triple-coil pulsed magnet design for magnetic-field experiments beyond 95 T.
We acknowledge the support of the HLD at HZDR, a member of the European Magnetic Field Laboratory (EMFL), the DFG via SFB 1143, and the BMBF via DAAD (project-id 57457940).

[1] http://www.hzdr.de/hld

Speaker: Dr Sergei Zherlitsyn (Helmholtz-Zentrum Dresden-Rossendorf)

245 Mon-Af-Or4-04: Finite Element Method (FEM) Simulations for Pulsed Magnet Design Using COMSOL Multiphysics

Ultra-high field pulsed magnets must simultaneously satisfy a number of often competing electrical, electromagnetic, structural, thermal, and economic constraints. To produce the highest field possible, nondestructive pulsed magnets are designed to operate at the limits of mechanical strength and electrical capacity of conductors. In this presentation, we will introduce a coupled multi-engineering finite element method (FEM) implemented in COMSOL TM Multiphysics package for detailed and accurate calculations of the mechanical, thermal and electromagnetic performances in entire longitudinal cross-section of the pulsed magnet. These transient FEM simulations are performed for entire pulse length and take into account the temperature and magnetic field dependencies of electrical conductivity and mechanical properties of all the materials to provide better accuracy. Application Programming Interface (API) feature of COMSOL was used to automate repetitive modeling steps to significantly reduce the necessary time to create FEM models for a pulsed magnet which may consists up to thousands of turns and insulation/reinforcement layers. Computational results for our signature 100T non-destructive pulsed magnet will be presented.

Speaker: Dr Doan Nguyen (Los Alamos National Laboratory)

246 Mon-Af-Or4-05: Cold Spray materials for high field magnets at the LNCMI

Material is a key issue for the high field magnet development. For DC resistive magnets, copper alloys with high strength and high electrical conductivity from room temperature up to 200 °C are required.
Steady high field resistive magnets developed worldwide used mainly two technologies: the Bitter and the polyhelix one. Each technology encounters material limits.
In the case of Bitter, magnets are made of thin plates (from 0.2 to 1 mm) up to 1000 mm in diameter. High performance Copper alloys with a high content of Silver (classically 18 wt.%, with a yield strength ranging between 800 to 1000 MPa and a minimum of conductivity at room temperature of 50 MS.m-1) have been industrialized by one company up to 250 mm in diameter. For the need of larger diameters, copper plates with a possible addition of a low content of Silver are proposed by different companies. They give a lower yield strength (between 400 to 450 MPa) and a higher conductivity around 58 MS.m-1. This could be a limitation when optimizing Hybrid magnets where the external superconducting windings increase the forces on the outer most Bitter as compared to stand alone resistive magnets.
For the polyhelix technology a similar limitation is existing: the forged and heat treated tubes needed for the helix magnets exhibit decreasing physical properties with increasing diameters. To overcome this problem, the LNCMI has started a R&D program in 2012 to consolidate an alternative way of production. The Cold Spray technology, classically used for repairing purposes or layer deposition, was adapted for the production of thick tubes of copper alloys. We present the results obtained on a material point of view as well as the field production that was obtained using these new products.

Speaker: Dr Olivier Jay (LNCMI‐EMFL‐CNRS, UGA, INSA, UPS )

190923_OJ_MT26.pdf

247 Mon-Af-Or4-06: High strength - high conductivity silver nanowire-copper composite wires by spark plasma sintering and wire-drawing for non-destructive pulsed fields

Copper-based conductive wires with both a high strength and a high electrical conductivity could find applications in aerospace and power engineering as well as in niche scientific applications such as materials for the production of high-field pulsed magnets. Indeed, in order to produce non-destructive fields, the coils must be wound of wires with a very high mechanical strength to resist Lorentz forces. LNCMI-Toulouse produces some of the most intense non-destructive pulsed magnetic fields in the world with a European record of 98.8 Tesla and aims at reaching more than 100 Tesla.

For several years, LNCMI and CIRIMAT have been exploring the design and preparation of novel copper-based nanocomposite wires, including the present silver nanowire-copper wires.

Silver nanowires were synthetized and mixed with a commercial micrometric copper powder. Samples containing 1, 5 and 10 vol.% silver were prepared. Copper and silver-copper cylinders (diameter 8 mm, length 33 mm) prepared by spark plasma sintering the corresponding powders serve as precursors to wire-drawing. The diameter of the cylinders is reduced by wire-drawing at room temperature, in several passes, thus producing progressively finer wires (diameter in the range 1-0.2 mm).

The copper grains show a lamellar microstructure with ultrafine grains (200-700 nm for a 0.5 mm diameter wire) elongated over several micrometers. The silver nanowires are dispersed along the grain boundaries of copper.

The electrical resistivity and tensile strength were measured at 293 K and 77 K. The tensile strength for the composite wires is more than twice the value measured for the corresponding pure copper wires. Interestingly, the wires containing only 1 vol.% silver offer the best combination of high strength (1100 ± 100 MPa at 77 K) and low electrical resistivity (0.50 µΩ.cm).

Thus, the present 1 vol.% silver-copper composite wires compare favorably with silver-copper alloy wires containing about 20 times more silver.

Speaker: Mr Simon Tardieu (Laboratoire National des Champs Magnétiques Intenses, EMFL, CNRS-INSA-UGA-UPS)

Mon-Af-Or4-06-Tardieu.pdf

Mon-Af-Or5 - Detector Magnets I

Conveners: Prof. Lance Cooley (ASC/NHMFL/FSU), Marco Marchetto (TRIUMF)

248 Mon-Af-Or5-01: Magnet Designs for the Future Circular Collider ee, eh and hh Detectors

A design study started in 2014 at CERN for a Future Circular Collider. A new 100 km ring-tunnel for the collider magnets is foreseen as well as new particle detectors to probe electron-positron (ee), electron-hadron (eh) and hadron-hadron collisions (hh). A conceptual design report is due in 2019 for all FCC collider and detector options. Baseline designs for the various Detector magnets were developed.
For FCC-ee detectors two variants were defined: (1) a 7.6 m bore and 7.9 m long classical 2 T / 600 MJ superconducting solenoid surrounding the calorimeter; and (2) a very challenging 4 m bore, 6 m long, ultra-thin and radiation transparent 2 T / 170 MJ superconducting solenoid surrounding the tracker only.
In the case of the FCC-eh, the detector solenoid is combined with a dipole magnet for guiding the electron beam in and out the collision point. This detector comprises a 3.5 T / 230 MJ, 2.6 m free bore and 9.2 m long superconducting solenoid.
Demanding is the FCC-hh detector featuring a 14 GJ magnet system of three series connected solenoids, comprising a 4 T superconducting main solenoid with 10 m free bore, 20 m long, in line with two 3.2 T superconducting forward solenoids with 5.1 m free bore, 4 m long.
A quite challenging family of detector magnets has been proposed that need further engineering in the years to come. However, the conductor technology is essentially the same in all solenoids, using Ni doped and structurally reinforced pure Al stabilized NbTi/Cu strands based Rutherford cables, conduction cooled solenoid windings, almost entirely comprising high yield strength Al alloy. A survey of the various magnets is presented and the engineering challenges highlighted, in particular focusing on superconductor requirements and structural aspects.

Speaker: Herman Ten Kate (CERN)

249 Mon-Af-Or5-02: Status of Performance Testing of the Mu2e Transport Solenoid Coils

The magnet system of the Muon to electron (Mu2e) experiment at Fermilab consists of three solenoid magnets: the Production Solenoid (PS), the Transport Solenoid (TS), and the Detector Solenoid (DS). The S-shaped TS contains 52 coils grouped into modules, which are typically 2 coils shrink fitted into Al shells. These modules are further grouped into units made of 1-3 modules. As part of the acceptance process for these units, the magnetic center of all coils and critical dimensions of the Al shells are measured. The magnetic model is updated with these as-built values to ensure the magnetic requirements for the experiment are met. In addition, units are tested to 120% of nominal current at liquid helium temperatures to study quench performance and splice resistance. Results from the first units will be presented.

Speaker: Karie Badgley (Fermilab)

Mon_Af_Or5_02.pdf

Mon_Af_Or5_02.pptx

250 Mon-Af-Or5-03: The ALPHA-g apparatus - A precision magnet system for antimatter gravity measurement

The ALPHA-g experiment at CERN aims to be the first-ever to precisely weigh antimatter under Earth’s gravity, by “dropping” antihydrogen atoms with a magnet system. The anti-atoms are initially confined inside a vertical octupole and between two end cap coils. The currents in the coils are then gradually decreased to release the anti-atoms. The up -down balance of the escapes depends on gravity and the relative strength of the coils. By observing the escapes at different coil balances, the weight of antihydrogen is determined.
Achieving our first target of 1% precision in weight requires controlling the measurement field to an unprecedented 10 ppm precision. A sophisticated dual-cryostat magnet system is constructed for this purpose. An inner wet cryostat contains five octupoles, 22 coils and two solenoids (2 m overall height, 48 mm I.D.), and an outer dry cryostat contains a human-sized, shielded solenoid (2 m height, 600 mm I.D.). The centre of the system is used for gravity measurement, while other parts are used to confine, manipulate, transfer and cool the anti-atoms and their constituents. The octupoles and mirror coils are made to high precision at BNL by CNC wire-laying with active correction. The location, geometry and wire stock of each winding and its associated leads and splices are carefully designed using simulation to minimise field error. Wire placement inaccuracy and mechanical deformation of the windings are taken into account. Persistence effect is studied and mitigated by minimising the amount of superconductor, constructing an up-down symmetric magnet system, and using a special high-filament count NbTi cable. Higher-order corrector windings are constructed around the measurement region to provide additional field-shaping flexibility. A DCCT-based, bi-polar PID current control system is used to power the windings with < 10 ppm current precision. An environmental field-cancelling system is planned.

Speaker: Chukman So (TRIUMF (CA))

Mon-Af-Or5-03-So.pdf

Mon-Af-Or5-03-So.pptx

251 Mon-Af-Or5-04: Madmax: design of a very large-scale 9 T dipole for dark matter experiment

The MADMAX (MAgnetized Disc and Mirror AXion) project is a dark matter experiment that aims at finding axion particles with masses in the range of 100 µeV. In order to achieve this goal, the chosen approach is to use a detector comprised of many magnetized dielectric discs put in parallel in front of a mirror. The relevant level of magnetic induction needed to increase the probability of detecting axions is expressed by physics laws as the square field integral over the disc surface, and fixed at a Figure Of Merit of 100 T²m² over an axial length of 2 meters. In the framework of an innovation partnership with the Max Plank Institute, CEA proposed a conceptual design for a large NbTi dipole creating a field of 9 T in a warm bore of 1.3 m in diameter. This paper will give an overview of the magnet main features. First, the technical specifications, constraints and strategic choices are introduced. Then, the overall design approach is described including magnetic, mechanics, cryogenic, conductor and quench studies. Finally, technological aspects, development plan and cost optimization will be discussed.

Speaker: Walid Abdel Maksoud (CEA)

MT26_Madmax_WAM.pptx

252 Mon-Af-Or5-05: Design of the BabyIAXO superconducting detector magnet system

Searching for axion like particles is one of the top priorities in particle physics. Using helioscopes is a promising technology to detect solar axions. The conceptual design of the state-of-the-art facility, the International Axion Observatory (IAXO), has resulted in a 22 m-long / 660 MJ stored energy, toroidal magnet system comprising 8 racetrack coils. In order to ensure readiness of the technology required for IAXO, a smaller scale but fully functional 10 m-long twin bore demonstrator called BabyIAXO is prepared for construction in the early 2020s. Similar to IAXO, the two magnet bores have to point to the Sun and thus to rotate $360^\circ$ horizontally and $\pm25^\circ$ vertically. The 50 MJ detector magnet of BabyIAXO is based on a common-coil layout, comprising two flat racetrack coils of 10 m length spaced by 0.8 m. Using Al-stabilized Rutherford cable with 8 NbTi strands of 1.4 mm diameter, the system can operate at 9.8 kA nominal current with 2 K temperature margin, while producing 2.0 T in the center of detection bores and 3.2 T peak field. The magnet operates in persistent mode by using a thermally activated switch made of NbTi/CuNi matrix wire. The current leads are ‘over-current’ designed in order to reduce associated heat loads during short charging and long idle periods at full current. Uniquely, a group of two 1-stage GM and three 2-stage PT cryocoolers is used for precooling and maintaining 4.5 K in the coils. In addition, two cryocirculators are used to transfer efficiently the available cooling capacity to cold mass, thermal shield and current leads. While using completely ‘dry’ cooling conditions, this cryogenic setup ensures cooling down the 15 t cold mass in 18 days. The relevance of design, construction and operational experience gained with BabyIAXO for a fully fletched IAXO system is further discussed.

Speaker: Dr Nikolay Bykovskiy (CERN)

BabyIAXO_magnet_Bykovskiy.pdf

BabyIAXO_magnet_Bykovskiy.pptx

253 Mon-Af-Or5-06: Design and first tests of a unique, superconducting multipole magnet for the ultracold-neutron trap PENeLOPE

The Precision Experiment on Neutron Lifetime Operating with Proton Extraction (PENeLOPE) will use a large superconducting multipole magnet to trap ultracold neutrons. To achieve this, a large volume of 750$~$L needs to be enclosed within a steep magnetic-field gradient of at least 2$~$T, requiring a unique multipole arrangement with a high current density of 316$~$A/mm$^2$ and thin support structures. Additionally, it needs to be able to ramp within 100$~$s, so ultracold neutrons can be filled into the trap, stored, and then detected.
The goal is to measure the beta-decay lifetime of free neutrons with unprecedented precision and accuracy. The novel combination of counting neutrons surviving the trapping period and detecting protons from neutron decay in situ should be able to resolve the discrepancies between previous neutron-lifetime experiments.
This presentation will cover the design of the magnet and show results of first tests at Technical University of Munich.
This work is supported by Deutsche Forschungsgemeinschaft (DFG), the Excellence Cluster "Origin and Structure of the Universe" and the Maier-Leibnitz-Laboratorium, Garching.

Speaker: Wolfgang Schreyer (TRIUMF)

MT26_PENeLOPE.pdf

MT26_PENeLOPE.pptx

Mon-Af-Or6 - Cable-in-Conduit Conductors

Conveners: Mr Antonio della Corte (ENEA), Simonetta Turtu' (ENEA)

254 Mon-Af-Or6-01 [Invited]: SuperCIC: enhancing winding current density for high-field windings of tokamaks

The design for a new approach to cable-in-conduit (SuperCIC) for use in the high-field windings of tokamaks. Two layers of high-field superconductor wires are cabled onto a thin-wall perforated center tube. An overwrap is applied and the cable is inserted as a loose fit into a sheath tube. The sheath tube is drawn down onto the cable to compress the wires onto the center tube and immobilize them. The SuperCIC is then co-wound with a high-strength armor extrusion, which is kerf-cut so that the co-winding onto a coil mandrel can be made without deformation within the armor or the CIC. Windings can be layer-wound so that the wires used in the SuperCIC for each successive layer are appropriate to the magnetic field seen by that layer (NbTi, Nb3Sn, Bi-2212). Demountable splices interconnect layers and can be configured as a split-shell toroid that accommodates assembly onto an intact plasma chamber. Optimized simulations show that a tokamak with field at plasma of 12 T could be made with winding current density ~150 A/mm2, sufficient for optimizing the fusion power density in a compact spherical tokamak.

Speaker: Peter McIntyre (Texas A&M University)

Mon-Af-Or6-01.pdf

Mon-Af-Or6-01.pdf

Mon-Af-Or6-01.pdf

Mon-Af-Or6-01.pptx

Mon-Af-Or6-01.pptx

Mon-Af-Or6-01.pptx

255 Mon-Af-Or6-02: Manufacturing and Test of Next Generation 100 kA @ 10 T and 4.5 K ReBCO-CORC Cable-In-Conduit Conductors for Large-Scale Magnets

ReBCO-CORC Cable-In-Conduit Conductors are high-current multi-strand conductors aimed for application in large scale magnets, for example in magnets for particle detectors and fusion experiments; but also for use in bus lines feeding high currents to magnets or other devices. ReBCO based conductors open up the operating temperature range of 20 to 50 K, not accessible by any other practical superconductor, allowing super stability and significant reduction in cooling cost and simplification of the refrigeration plant. ReBCO-CORC also enables a magnetic field in large magnets far beyond 20 T at 4.5 K and a dramatic increase in thermal stability compared to NbTi or Nb3Sn superconductors.

In recent years, three unique CORC CICC samples with six-around-one cable layout were developed as technology demonstrators at CERN in collaboration with Advanced Conductor Technologies. The tests of these conductors at low temperature in external magnetic field yielded very promising results, but also showed several issues for improvement. A new 2.8 m long CORC CICC has been prepared to further increase the conductor’s critical current to 100 kA at 10 T and 4.5 K and to further enhance its thermal, electrical and mechanical stability. The conductor is designed specifically for high-current bus-bars and large detector-type magnets. It therefore features a copper jacket and practical conduction cooling via a cooling line embedded in the jacket. In contrast to previous CICC samples, the voids between CORC strands are now filled with a solder alloy providing mechanical stability to the strands. The new CICC is scheduled for testing at the SULTAN test facility at PSI, Switzerland in Q2 of 2019. Manufacturing details and test results will be reported.

Research on CORC CIC-Conductors is going strong and many new and exciting results are forecast for the years to come.

Speaker: Dr Tim Mulder (CERN)

Mon-Af-Or6-02-Mulder-CORC CICCs-MT26.pdf

Mon-Af-Or6-02-Mulder-CORC CICCs-MT26.pptx

256 Mon-Af-Or6-03: Presentation withdrawn

257 Mon-Af-Or6-04: AC Loss Measurements of the DEMO TF React&Wind Conductor Prototype no. 2

The EUROfusion DEMO is being designed as the fusion machine to be built after ITER. During the preconceptual phase, several design options are investigated by theoretical analyses as well as tests on newly developed conductor prototypes.

One design option for the toroidal field magnet (TF) and central solenoid (CS) is based on flat Nb3Sn forced-flow conductors made with react&wind technique. The usage of these conductors simplifies some steps in the conductor and coil manufacturing, and together with graded layer-winding allows approx. 50% reduction of the required amount of Nb3Sn compared to ITER-like design based on wind-react-insulate pancake-winding.

Two full-size prototype cables for DEMO TF coil were manufactured, jacketed and tested in several test campaigns in SULTAN test facility. The DC results for the second prototype, RW2, rated for 63 kA at 12.3 T, were presented and published in 2018. The extensive AC loss measurements are subject of this paper. The AC loss data were collected over several test campaigns performed on various assemblies of RW2 at parallel and perpendicular cable orientation with respect to the AC field. The measurements done at 4.5 K and 20 K allow us to decompose the AC loss contributions originating from the bundle of superconducting strands and copper-matrix stabilizer located around the cable. The AC loss for sinusoidal and trapezoidal field variations will be presented and discussed. The low AC loss of the flat cable makes the cable an attractive choice for the central solenoid operating in a pulse mode.

Speaker: Kamil Sedlak (EPFL Lausanne)

Sedlak_AC_loss_MT26.pdf

258 Mon-Af-Or6-05: The design and R&D work of high performanceCICCs for CFETR TF

The engineer design for CFETR, “China Fusion Engineering Test Reactor”, has start since 2017. Its magnet system includes the Toroidal Field (TF), Central Solenoid (CS) and Poloidal Field (PF) coils. The maximum field of TF will get around 14.5 T, which is much higher than that of other reactors. One full-scale TF coil will be built. Tremendous investigations need to be made in the development of high performance CICCs for CFETR TF before coil manufacutring. The TF conductor will operate with 87kA at 4.2K and 14.5 T. It will be subjected to much higher Lorentz force than ITER. The performance degradation during cycling will be one big issue. In order to reduce/avoid the degradation, the STP and CWS design were considered, and some R&D work was performed in 2018.
In this paper, the recent progress in development of CFETR TF CICC was described in details, in terms of superconducting material, design, strand damage analysis, press testing at low tempereature on conductor. The results show that the two designed conductor have similar mechanical property to ITER conductor with STP layout, which could avoid the degradation during operation.

Speaker: Dr Qin Jinggang (Institute of Plsama Physics, CAS)

18:00 Exhibitor Reception

Tuesday 24 September

07:50 Registration Open (7:00 AM - 5:00 PM)

07:55 Exhibits Open (8:30 AM - 4:00 PM)

For a list of Exhibitors, please visit: https://mt26.triumf.ca/#exhibitors.

Plenary: Helen Felice (CEA Paris-Saclay)

Convener: Soren Prestemon (LBNL)

259 Tu-Mo-PL2-01: Advances in Nb3Sn Superconducting Accelerator Magnets

With the faraway goal of a 100 TeV new hadron-hadron collider, the ambition for very high field accelerator magnets has never been so broad. The technology choice between Low Temperature Superconductor (LTS) Nb3Sn and High Temperature Superconductors (HTS) for such a machine remains to be made and might lead to a hybrid solution. In all cases, the challenges are ahead of us: from superconducting material’s cost to its implementation.
Nb3Sn will be used in HL-LHC in the 11-12 T range. Models and prototypes are leading the path toward a small series which demonstration remains to be done. Nb3Sn is indeed the most advanced technology but is a delicate material. Its sensitivity to strain makes it a challenging candidate for high field and therefore high stress main dipoles. For large scale production toward the next collider, important progress on industrialization must be made.
We propose here to revisit the implementation of this material in accelerator magnets from the early days of the technology to the state of the art. Nb3Sn magnet technology progress on design, coil fabrication, magnet assembly, and test will be covered. We will try to assess the key challenges to be faced to provide reliable and cost effective Nb3Sn magnets for the High Energy physics community.

Speaker: Helene Felice (CEA Paris-Saclay)

Plenary_HFelice_final2.pdf

08:45 Coffee Break (during Poster Sessions)

Tue-Mo-Po2.01 - Magnets for X-Rays and Neutrons

Conveners: Dr Hitoshi KITAGUCHI (National Institute for Materials Science), Iain Dixon (NHMFL-FSU)

260 Tue-Mo-Po2.01-01 [1]: A large scale cryogen-free magnet for neutron decay research

The design of a large purpose built cryogen-free magnet is reviewed. The system has been manufactured for the Fundamental Neutron Physics Beamline at the Spallation Neutron Source in Oak Ridge, Tennessee.
The magnet system will house a custom spectrometer and be used to measure a, the electron-neutrino correlation parameter, and b, the Fierz interference term in neutron beta decay.
The cryostat is cylindrical, 7.5m along its axis and 1.43 m in diameter. It houses a complex set of niobium-titanium superconducting windings which provide a varying magnetic field profile along a 320mm diameter gold-plated UHV bore. The bore tube extends along the full length of the cryostat and has orthogonal ports connected to the neutron beamline. A vacuum of <3.10-10 mbar is achieved.
The stray field generated by the magnet windings is compensated by a series of negatively wound co-axial windings which have approximately twice the diameter of the internal positive windings. The cryostat system will be housed in a passive steel shield to further compensate the stray field.
The magnet windings operate nominally at 4K and are cooled by four Gifford McMahon two-stage cryocoolers, each delivering 1.5W cooling power at their second stage. No liquid cryogens are used for normal operation of the system. The cryostat design allows the magnet system to be operated in both horizontal and vertical orientations.

Speakers: Dr Roger Mitchell (Cryogenic Ltd), Dr Jeremy Good (Cryogenic Ltd)

Nab Poster2.pdf

261 Tue-Mo-Po2.01-02 [2]: Development of An 10 T Superconducting Split Magnet for X-ray Diffractometer

Abstract—An 10T superconducting split magnet with a room-temperature bore of 40 mm was designed, manufactured and tested for X-ray diffractometer at The High Magnetic Field Laboratory in Hefei, China. The superconducting split magnet provides room-temperature splitting gap of 10 mm and scanning angle of 160 degrees for X-ray beam. As a result of magnetic field intensity considerations, the magnet is composed of a split-pair of Nb3Sn inner coils and NbTi outer coils. Nb3Sn coils and NbTi coils are connected in series separately and charged with two independent power supplies respectively. The magnetic field homogeneity is better than ±1% from -10 mm to 10 mm in axial direction. In addition, two pairs of HTS current leads and a two-stage GM cryocooler with cooling capacity of 1.5 W at 4.2 K were adopted to realize a zero liquid helium boil-off. In this paper, the magnetic design, manufacture, mechanical behavior analysis, and the test results of the magnet are presented.

Speaker: Dr PengCheng Huang

Tue-Mo-Po2.02 - Pulsed Magnets Technology

Conveners: Doan Nguyen (LANL), Dr Jun Lu (National High Magnetic Field Laboratory)

262 Tue-Mo-Po2.02-01 [3]: Design of a 70T Quasi-Continuous High Magnetic Field System with a Dual-Coil Magnet

As a significant research method, quasi-continuous high magnetic field (QCMHF) can meet scientific experimental requirements for higher magnetic intensity, longer flat-top pulsed width and lower ripple in the field of physics, biology and other scientific fields. In this paper, a QCMHF system designed by multi-objective optimization method is present to obtain the magnetic intensity of 70T with high-stability at Wuhan National High Magnetic Field Center. The magnet system consists of two coils, the inner coil is energized by the 100MVA/100MJ generator-rectifier power supply and the outer coil is powered by a 22MJ capacitor power supply. A protective circuit is set for short-circuit fault between the two power supplies. To improve the stability of the QCMHF, two decoupling methods are proposed and analyzed. In the hardware circuit decoupling scheme, a compensatory transformer whose mutual inductance counteracts the magnet’s mutual inductance is connected series in the circuit. In the software control decoupling scheme, the repetitive control strategy is applied to make the rectifiers output an extra voltage to offset the influence from the mutual inductance. Moreover, a self-adaptive closed-loop PI feedback controller is used to reduce the ripple of the QCMHF. The MATLAB/Simulink platform is adopted to establish the equivalent model of QCMHF system and the preconceived 70T/100ms flat-top pulse with ripple less than 200 ppm is generated.

Speaker: Dake Li (Huazhong University of Sci. & Tech.)

Tue-Mo-Po2.02-01_李大可.pdf

263 Tue-Mo-Po2.02-02 [4]: Research on Repeated Pulsed High Magnetic Field Control System Based on Pulsed Generator Power Supply

The repeated pulsed high magnetic field system is widely used for neutron diffraction, terahertz radiation, guiding magnetic field and so on. In these applications, more and more attentions are paid on magnetic field waveform consistency. The pulsed generator power supply, with large energy storage and controllable output voltage, is suitable for generating repeated controllable pulsed magnetic field. However, it’s very difficult to control the magnetic field waveform because of the rapid change of the magnetic field, the time-varying nonlinear magnet resistance and low frequencies working characteristic of phase-controlled rectifier. Base on the analyses of the operation conditions, a transient average-value model of pulsed generator power supply was established which figured out the function relationship between the magnet resistance and the magnetic field waveform. Therefore, by computing the real-time resistance of the magnet, controlling the output voltage of the power supply, the response speed of the phase-controlled rectifier would be improved. There are some errors in the theoretical calculation model of magnet resistance, so a novel on-line modified method of the magnet resistance employing the gradient descent technique is proposed. Based on this real-time calculation of the resistance, a feedforward-feedback controller is designed. As for feedforward control, the predicable disturbances of the system such as the change of magnet resistance are compensated, as for feedback control, the error caused by random disturbance is reduced. So that the control performance is enhanced and the consistence of magnetic field waveform is improved. The simulations and the experiments verified the feasibility of this control strategy, and generated a series of 30 T consistent pulse magnetic fields.

Speaker: Yun Xu ( Huazhong University of Sci. & Tech.)

Tue-Mo-Po2.02-02 许赟.pdf

264 Tue-Mo-Po2.02-03 [5]: A Design Method for Repetitive Pulse High Magnetic Field System Based on Multi-objective Optimization Algorithm

Repetitive pulsed high magnetic field (RPHMF) provides a novel solution for the frontier researches in the areas of condensed matter physics, materials science, biomedicine, and so on. Significant amount of attentions have been paid to the study of RPHMF by researchers. As the higher demand for magnetic field intensity and pulse frequency of RPHMF, the repeated supplement of energy storage and the thermal design of the magnet are enormous challenging at the same time. In the traditional design methods, the magnet and the power supply are designed step by step. However, the design of the power supply and the magnet is constrained by various factors including stress，power, current, voltage and temperature rise. Besides, these factors may interact and restrict each other. Therefore, it is hard to meet the design requirements of nonlinear complex systems with high power and strong coupling by traditional design methods. Based on the nonlinear dynamic analysis of the power supply and magnet, a mathematical model is built for the collaborative optimization in this paper. Accordingly a multi-objective design method of iterative algorithm for the overall optimization of the power supply and the magnet is proposed, which is combined by pareto-based differential evolution algorithm，real-time digital simulation, structure design of magnet and finite element analysis.In this paper, a 5T 20Hz RPHMF is designed by this multi-objective optimization algorithm for relativistic backward wave oscillator(RBWO)，which is used to generate high power microwave. Simulation and experiments results show that overall optimization of the magnet temperature rise, magnetic field intensity and continuous working times is realized. Therefore this multi-objective collaborative optimization design is feasible and this design method is of great application for RPHMF.

Speaker: Yun Xu (Huazhong University of Sci. & Tech.)

Tue-Mo-Po2.02-03 xuyun.pdf

265 Tue-Mo-Po2.02-04 [6]: Research on a Combined Power Supply of Battery and Pulsed Generator System for High Pulsed Background Magnetic Field

As an important extreme experimental condition, high magnetic field plays an irreplaceable role in the frontier scientific research, such as condensed matter physics, new materials processing. The main pulsed high magnetic field laboratories in the world are constantly working to generate higher pulsed magnetic field. A nondestructive magnet aimed at generating very high pulsed magnetic field such as 100 T is made up of several coils nested coaxially. The outer coil is in charge of getting a long pulse width background high magnetic field, accordingly the outer coil often has large radius and requires enormous energy. At the Wuhan National High Magnetic Field Center (WHMFC), a novel combined power supply of a 1kV battery bank and a 100 MVA / 185 MJ pulsed generator system is designed. In this paper, firstly consideration of magnet coupling function, the energy, stress and heating of the outer coil, a cascade structure of 24-pulse rectifier and battery with crowbar circuit is proposed. Secondly, based on a logically organizing the discharging sequence of power supply, an operation strategy consisting of rectifier, inverter, de-excitation, freewheeling and the coordination of the power supplies is adopted. Thirdly, safe operation areas of the trigger angle of the 24-pulse rectifier are derived. At last, a series of simulations and experiments (up to 20kA) are carried out, and the design of the combined power supply for high pulsed background magnetic field is valid and feasible.

Speaker: Yun Xu (Huazhong University of Sci. & Tech.)

266 Tue-Mo-Po2.02-05 [7]: Design and Implementation of DC Pulsed Power Supply Employing Self-excited Induction Generators and Flywheels for Toroidal Field Coils of a tokamak device, Plato

We developed a 600kW pulsed DC power supply employing two pairs of a self-excited induction motor/generator (IMG) and a flywheel for toroidal field coils (TFCs) of Plato. Plato is a new tokamak device to measure plasma turbulence precisely, which is under construction at Kyushu University in Japan. In the presentation, we will describe the details on the structure and experimental results of the power supply.

The power supply is categorized into a type of flywheel energy storage system (FESS) since it converts the kinetic energy of flywheels into electricity with IMGs in a discharge phase. The FESS is necessary to supply TFC current of Plato since the pulsed power consumption of the TFCs reaches 600 kW. Before Plato’s experiments, the power supply accelerates the flywheels and stores 2.88MJ of kinetic energy over 3 minutes. After the acceleration phase, it feeds 600 kW of electricity to the TFCs of Plato for 0.5 seconds. In order to achieve the above operation, we adopted two pairs of an off-the-shelf squirrel-cage IMG and an iron plate flywheel. The rated power of the single IMG is 250kW and the diameter and thickness of the flywheel are 0.9 m and 0.04 m, respectively.

As a new feature of the power supply, we utilized combination of two self-excited induction generators (SEIGs), a thyristor rectifier and a DC/DC converter. The power supply employs self-exciting capacitors in order to excite the IMG voltage by self-excitation phenomena. Furthermore, the thyristor rectifier and the DC/DC converter are installed between the IMGs and the TFCs. Although the SEIG voltage is stepwise due to on/off control of the self-exciting capacitors, the DC/DC converter maintains accurate TFC current. Using this method, we realized the compact pulsed power supply compared to capacitor banks, synchronous generators or inverter-driven IMGs.

Speaker: Masamichi Murayama (Tokyo Institute of Technology)

MT26_MasamichiMURAYAMA2.pdf

267 Tue-Mo-Po2.02-06 [8]: Presentation withdrawn

Tue-Mo-Po2.03 - Detector Magnets II

Conveners: Boris Bellesia (Fusion for Energy), Christophe Berriaud (CEA / Irfu)

268 Tue-Mo-Po2.03-01 [9]: Conceptual Design of DUNE Near Detector Superconducting Magnet System

The Deep Underground Neutrino Experiment (DUNE) has formed a near detector design group (NDDG) tasked with delivering a CDR by the end of the year. The DUNE Near Detectors will be housed in an underground hall on the Fermilab site. The two main detector systems are a liquid argon detector and a high-pressure gas time projection chamber (HPgTPC). The HPgTPC requires a magnet that generates a 0.5 T solenoidal magnetic field in a large volume of 6 m diameter, and 5 m length. In this paper, we present a superconducting magnet system design. We investigated: an open air core magnet with three coils, and a five coils system having two active fringe field shielding coils. Coils positions were optimized to obtain the specified field homogeneity in the magnet good field region, while minimizing the Lorentz forces and the superconductor volume. We discuss the choice of NbTi superconducting cable, the operating current and the temperature margins. We will also present a preliminary magnet system mechanical concept and present a FEM stress analysis.

Speaker: Vladimir Kashikhin (Fermilab)

MT26_DUNE_ND_092319_VK_ADB.docx

MT26_DUNE_ND_092319_VK_ADB.pdf

Poster_ND_Magnet_091919a.pdf

269 Tue-Mo-Po2.03-02 [10]: 2D and 3D Conceptual Magnetic Design of the MADMAX Dipole

The ultimate frontier of the particle physics beyond the Standard Model is the research of axion-like particles, to explain the absence of CP violations in the strong interaction and provide dark matter candidates. In the MADMAX (MAgnetized Disc and Mirror AXion) experiment, the principle of axions detection relies on their predicted emission of an electric field proportional to the square of a static magnetic field using magnetized dielectric disks. In this experiment, the magnetic field would be provided by a 9 T NbTi dipole magnet, 6.0 m long and with an aperture diameter of 1.3 m, producing a Figure of Merit over the disk surfaces of 100 T²m² along 2 meters, enough to detect axions with masses in the range of 100 μeV. This paper reports the 2D and 3D conceptual magnetic design of the MADMAX dipole. Starting from a general overview of the best magnet configuration, it introduces the parameters and design methodology to adapt the dipole to the experiment constraints. Then, the 2D and 3D designs are described, focusing in particular on the cross-section, the harmonics optimization in 2D and the heads optimization in 3D with and without iron, made by coupling a dedicated analytical approach to genetic algorithms. In the end, a section shows the optimization of the conductor cost as a function of the overall current density.

Speaker: Dr Valerio Calvelli (CEA)

270 Tue-Mo-Po2.03-04 [11]: Conductor development and Cold mass design for an ultra-thin 2T, 4m bore, 6m long detector solenoid for the FCC-ee IDEA detector

The proposed IDEA Experiment (International Detector for Electron-positron Accelerator) for probing ee+ collisions at the Future Circular Collider FCC is conceptualised around an ultra-thin, radiation transparent 150 MJ superconducting solenoid of 6 m length and 4 m free bore providing a magnetic field of 2 T for the inner tracking detector. Positioning the solenoid around the inner detector, thus inside the calorimeters requires the cold mass and cryostat to be ultra-radiation transparent (< 1 radiation length) to not hinder too much through particle scattering the signal in the calorimeters.
The magnetic pressure of 16 bar and the thin wall cold mass impose high mechanical requirements on the conductor like some 230 MPa yield strength. A new high-yield strength aluminium stabilized NbTi/Cu Rutherford cable has been developed comprising 0.1% w.t. Nickel doped, precipitation hardened high purity Aluminium for thermal stability, and 7068-T6511 Aluminium alloy as mechanical reinforcement. To achieve intermetallic bonding between stabilizer and reinforcement constituents, electron beam welding, friction stir welding, and cold welding based on the so called FORTE process have been investigated. They are compared for bonding strength, lifetime, scalability and cost.
Besides the conductor, the mechanical and thermal designs of the cold mass comprising the conductor windings are presented. A conduction based cold mass cooling system using high-purity Aluminium heat drain strips thermally connecting the windings to the cold mass liquid helium cooling tubes is proposed. The thermal considerations include the cool down process, energizing the solenoid and stationary operation, as well as multiple quench scenarios. Given the stored energy the light solenoid mass may require maximum energy extraction and use of quench heaters to warrant safe operation.
The conductor, cold mass and quench protection developments highlighted above are presented and detailed in the paper.

Speaker: Tobias Kulenkampff (CERN)

271 Tue-Mo-Po2.03-05 [12]: Performance of the new ALPHA-G conduction cooled solenoid

The ALPHA experiment at the CERN Antiproton Decelerator facility underwent a major upgrade in 2018. Amongst other improvements, key is the rotation of the atom magnetic trap axis, which is now vertical. Bilfinger Noell designed and fabricated the 2 m long superconducting vertical solenoid, which provides the 1 T background field for the experiment. This is an active shielded, conduction cooled, NbTi magnet with a warm bore of 0.5 m diameter. The system is designed to achieve a field precision of less than 10 ppm in the control volume and a charging time of less than 20 minutes. This contribution describes the main design features of the system and the results of the cold tests.

Speaker: Cristian Boffo (Bilfinger Noell GmbH)

272 Tue-Mo-Po2.03-07 [13]: loffe Trap Magnet for Project 8 Experiment

This work was performed as part of the international Project 8 collaboration. The goal of the Project 8 experiment is to measure the absolute neutrino mass using tritium beta decays, which involves precisely measuring the energies of the beta-decay electrons in the high-energy tail of the spectrum.
The experimental installation of the Project 8 Atomic Tritium Demonstrator requires a magnet with rather unusual field properties. The magnet has to contain within the cold mass a large closed volume surrounded by a continuous, uninterrupted boundary with high field, exceeding 2 T, whereas the field in a substantial volume inside this boundary has to be of the order of $10^{-4}$ T or less. A 1 T solenoid field provides the background field necessary for the detection of beta-decay electrons.
A proposed toroidal magnet system (Ioffe-Pritchard trap) comprised of specially shaped multiple racetrack windings satisfies these unusual requirements. The magnet is made of NbTi wire and expected to be conduction cooled. Manufacturability issues are addressed as well as the effect of the tolerances on the field quality. Additional topological features providing a low-field duct for interfacing with the peripheral coils of the energy selector are included in the design.

Speaker: Alexey Radovinsky (MIT)

MT26_poster_radovinsky_final.pdf

273 Tue-Mo-Po2.03-08 [14]: An investigation of the electromagnetic Interactions between the CLAS12 Torus and Solenoid Superconducting Magnets at Jefferson Lab

The Jefferson Lab 12 GeV Upgrade of Experimental End Station Hall B required a new detector system that would be more sensitive to forward going particles and handle higher luminosity. This new detector is CLAS12 and includes two superconducting iron-free magnets – a torus and a solenoid. The Torus magnet consists of 6-trapezoidal racetrack-type coils while the solenoid is an actively shielded 5 T magnet. The torus and the solenoid are located in close proximity to one another and are surrounded by sensitive particle detectors. The Torus and solenoid, operating at 3770 A and 2416 A respectively, were commissioned successfully and are operating normally. This paper will present an investigation of the electromagnetic interactions, which include induced static mechanical loads and inductive coupling. Modelled results and actual measured data during normal and off normal operation of the magnets is presented.

Speaker: David Kashy (Jefferson Lab)

Interaction Poster_Final.pdf

274 Tue-Mo-Po2.03-10 [15]: Design and Manufacturing Assessment of a Multi-purpose Detector for NICA Collider

Nuclotron-based Ion Collider state-of-art design involves innovative solutions in superconductive applied technology. Thanks to its consolidated experience, ASG has been directly involved into the program by providing to Joint Institute for Nuclear Research (JINR) a large 0.5 T Nb-Ti superconductive magnet (5.8m diameter, 8.1m length) equipped with active (resistive) modulation system. Typical solutions have been specifically optimized in order to guarantee maximum flexibility in all operative conditions.
ASG has been involved in the whole design: magnetic, structural, thermal, protection and control systems, including all auxiliary systems needed for the full magnet operation modes.
Magnetic configurations meeting optimized field requirements have been also selected accounting in detail the technological deviations. Two resistive coils perform the active modulation system that principally tune the optimized magnetic configurations.
The design takes in consideration Lorentz forces and coil interactions produced by the system to optimize mechanical structure and stresses on the coils. The electromagnetic interactions between components, during dynamic events, have been evaluated in order to verify the cryogenic and structural stability of the system.
The hydraulic/cryogenic system has been designed and manufactured in order to keep the magnet in superconductive condition: a thermal shield has been designed to reduce the radiation load while a liquid helium circuit has been optimized to keep the cold mass below 4.8 K.
A complete control system has been produced and configurated to operate the magnet and all the related auxiliary systems (vacuum, cooling, protection, power supply…) and also to protect the magnet in case of quench, in order to minimize thermal stresses on cold mass components.
For the manufacturing, ASG developed innovative system to operate with large magnet that allows winding of superconductive cable on thin former with ≈5m of diameter. Another tool was designed and manufactured on purpose to complete the assembly with horizontal axis.
Manufacturing phase is finished: winding is completed and assembly is ongoing,
Main results will be presented to illustrate the adopted process and technological solutions.

Speakers: Simone Grillo (ASG Superconductors SpA), Martina Neri (ASG Superconductors SpA)

MT26_ID#1755_ASG.pdf

Tue-Mo-Po2.04 - Resistive Magnets for Accelerator and Fusion I

Conveners: Reed Teyber (Lawrence Berkeley National Laboratory), Tenming Shen (LBNL)

275 Tue-Mo-Po2.04-01 [16]: Presentation withdrawn

276 Tue-Mo-Po2.04-02 [17]: Optimising a Magnetic Septum with Heating Jacket

The extraction line of the future synchrotron SIS100 will have a series of three normal-conducting magnetic septa which deflect the beam upwards. Underneath the third septum there will be a beam stop for emergency extraction. Therefore, the entire region will be very likely activated with anticipated doses that forbid manual installation of a heating jacket. A mechanism which would automatically open this third septum and install a heating box proved too big during mechanical design studies.
Therefore it has been decided to include the heating jacket into the septum. This significantly reduced the space for the magnetic screen to protect the orbit region from stray field. We will present the successful methods, and some less efficient ones, which we used to get an acceptable protection of the orbit against stray fields.

Speaker: Peter Rottländer (GSI Darmstadt)

Tue-Mo-Po2.04-02.pdf

277 Tue-Mo-Po2.04-04 [18]: Three-Dimensional Design of Massless Septum Magnets for High Intensity Synchrotrons with Slow Beam Extraction

In high intensity circular accelerators such as Rapid Cycling Synchrotrons (RCS) and Fixed Field Alternating-gradient (FFA) synchrotron, maximum beam intensity is limited by beam loss. Suppression of beam scatterings occurred in beam extraction system, especially in septum magnets, is one of the key issues to achieve low beam loss rate. Application of massless septum may be a promising way to overcome the beam loss problem. In this study, three dimensional design of the massless septum magnets for RCS and FFA is investigated. Utilizing 3D simulations, effects of nonlinear field distribution on extracted beam are analyzed and requirement of the massless septum magnets will be discussed.

Speaker: Yasuhiro Fuwa (Kyoto University)

278 Tue-Mo-Po2.04-05 [19]: Optimization of a Solenoid for an Electron Lens in SIS18

An electron lens – a novel instrument in accelerator physics to manipulate hadron beams with a magnetically confined electron beam - is under development at GSI, Darmstadt. It will be used to compensate the ion beam’s space charge by an overlapping electron beam and therefore may help to increase the intensity of primary beams in the low energy booster synchrotron SIS18 for FAIR. The main element of the lens is a solenoid with the longitudinal magnetic field of Bz = 600 mT, the diameter and the length of the good field domain of d= 80 mm and l = 300 mm. The overall length of the magnet including the iron housing is limited to L = 3360mm, corresponding to the available free space in a straight section of SIS18. To provide required parameters of the passing electron and ion beams the maximum field deviation from the average level in the magnet aperture is defined as ±5·10-4 relative units. The magnetic field in the solenoid aperture is expected to be ramped with the rate of up to 20 T/s. Consequently the eddy currents induced in the conducting elements of the magnet affects strongly the field characteristics. For achieving the required field quality inside the good field area it was necessary to solve several intrinsically linked problems: the choice of the proper winding stricture, especially in the end parts of the magnet; definition of the iron shield configuration; reducing the eddy currents in the solenoid construction elements as much as possible. To solve these problems we optimized the parameters of the magnet geometry. For this purpose we have combined the 2D finite element technology for the magnetic field modeling and the Nelder-Mead optimization strategy. The derived geometrical parameters ensured completely the required characteristics of the developed solenoid. Thorough investigation of its 3D model confirmed a quality and feasibility of the developed magnetic system.

Speaker: Dr Carsten Muehle (GSI Helmholtzzentrum fuer Schwerionenforschung)

Solenoid_Poster.pdf

279 Tue-Mo-Po2.04-06 [20]: Magnet design of the electron cooling System for HIAF

The new accelerate facility HIAF is under constructing in IMP (Institute of Modern Physics), Chinese Academy of Sciences. It consists of a linac, a booster of BRing and a spectrometer ring of SRing and some terminals for experiments. The electron cooling technology is applied in the SRing, which is composed of solenoids and racetrack coils. In this paper, the magnetic field of the electron cooler is simulated and article trajectories are displayed. Because of the long evacuated tube for cooling section, different type of drift solenoids are optimized to connect the two 3.5m solenoids to ensure the field fluctuation within 20Gauss.

Speaker: Ms Lixia Zhao

280 Tue-Mo-Po2.04-07 [21]: Design and Optimization of Eddy-Current Type Thin Septum Magnet for Beam Injection of Diffraction Limited Storage Ring

Fast kickers such as strip-lines along with lambertson magnet or thin septum magnet could support on-axis injection for Diffraction Limited Storage Ring (DLSR), in which traditional off-axis injection becomes inadequate. This paper focuses on the designing, manufacturing and process optimization of thin septum magnet. The scheme of eddy-current type thin septum magnet (the thinnest portion is with the thickness of 0.6mm) was adopted with laminated silicon steel sheets as magnet core. Firstly, theoretical analysis and calculating about magnet parameters was conducted. Then the simulation of main field and leakage field along the beam trajectory, the stray field decayed over 1millisecond time had been carried out within Opera 2D/3D. Besides, special attention was paid to compare and analyze of various shielding and insulating materials, leakage field suppression methods and optimize structure of septum to satisfy the physical requirement that the integral leakage field is less than 0.1% with respect to the main one. The work laid a foundation for injection technology of advanced light source.

Speaker: Mr Jin Tong ( (SARI-CAS( Shanghai Advanced Research Institute Chinese Academy of Sciences ), SINAP(Shanghai Institute of Applied Physics Chinese Academy of Sciences),UCAS (University of Chinese Academy of Sciences))

MT26-Tue-Mo-Po2.04-07.pdf

281 Tue-Mo-Po2.04-08 [22]: Design of focusing solenoids for charged particle beam applications

The design of focusing solenoids used in accelerator magnets or other charged particle beam applications usually has some general design requirements such as focusing strength, stray field, and eddy current losses. In superconducting solenoids specific requirements often include mechanical stress, cryogenic performance, and quench protection. In resistive solenoids specific requirements usually include minimum inductance and impedance.
Solenoids have advantages and disadvantages compared to quadrupole pairs,which also used for focusing charged particle beams. In contrast to a single quadrupole magnet, solenoid magnets can provide simultaneous focusing in both X and Y directions. The focusing strength of solenoids is relatively low compared to quadrupoles due to the second order field effects. The stray field of a single solenoid is relatively high compared to a quadrupole magnet.
This paper proposes several design options to improve the performance of traditional resistive focusing solenoids. These design options include adding bucking coils to limit the stray fields, splitting the main coil to change radial field components to enhance focusing strength, and implementing passive shielding layers to minimize the stray field and coil impedance simultaneously. Simulation results and experimental test data will also be presented.

Speaker: Dr Ye Bai (GE Global Research Center)

MT26_Design of Shielded Solenoids for Charged Particle Beam Applications_ Tue-Mo-Po2.04-08 [22] 715.pptx

282 Tue-Mo-Po2.04-09 [23]: Optimization of the compression coil configuration in magnetic trap type magnetic compression device

The design of the compression magnet in the magnetic trap type magnetic compression device has an important influence on the compression effect. Due to the large diameter (0.3m) of the vacuum chamber, and the severe eddy current in the metal cylinder induced by the rapidly changing current (700-1100kA/100μs) of the coil, the radial distribution of the magnetic field in the magnetic mirror region is very uneven. In order to produce a more uniform magnetic field configuration in the vacuum chamber, the quantity, size and position of the coils are optimized. Based on the experimental model and results from a compression magnet with multiple coil sets, it was shown that the configuration with more coil sets, closer distance between coil and vacuum chamber, and smaller size, will have more homogeneous magnetic field generated by the compression magnet. In this paper, a technical design scheme of compression magnet coils is proposed. The compression magnet adopts 9 coil groups, and each group has two coils connected in parallel, which can significantly improve the uniformity of the magnetic field and meet the engineering application requirements.

Key word: compression coil, magnetic trap type, magnetic compression, coil optimization

Speakers: Prof. Houxiu Xiao (Wuhan National High Magnetic Field Center), Tao Peng (Wuhan National High Magnetic Field Center)

Tue-Mo-Po2.05 - Mechanical Behavior I

Conveners: Hyung-Seop Shin (Andong National University), Dr Shintetsu Kanazawa (Muroran Institute of Technology)

283 Tue-Mo-Po2.05-01 [24]: Analytical formulation of mechanical stresses in no-impregnated, multi-layer solenoids

This paper develops and summarizes analytical formulations of radial and tangential stresses of superconducting, no-impregnated solenoids, based on a multilayer model. The analysis takes into account the fabrication steps (pre-winding and reinforcement), cooling-down and energization of the coil (magnetic loading). Both isotropic and orthotropic cases are considered.
Representative calculations for metal-as-insulation coils are presented and benchmarked against FEM computations with the CAST3M code.

Speaker: Philippe Fazilleau (cea)

Poster_MT26.pdf

284 Tue-Mo-Po2.05-02 [25]: Strain characteristic exploration for a 5 T superconducting split magnet system of a multi-field test facility

This paper deals with the mechanical characteristic and strain profile in a 5 T NbTi superconducting split magnet system, which provides a strong background field for the multi-field test facility established in Lanzhou University of China. The design of the split magnets, composed of 14 coils wound with NbTi wires, was adopted to satisfy a large test space (Φ100mm*800mm) for mounting the sample, fixture and sensors. Since the special structure, the mechanical behavior and stress/strain distributions in the coils, supporting structures became more important.
We present results, experimental and analytical, of hoop strains in the split superconducting magnet system, and equipped with strain gauges at their outermost turns. To explore the strain behavior in the magnets, several cryogenic resistance strain gauges (CRSG) with the half bridge compensation are used for the measurements for eliminating noise effects of both temperature and magnetic field. The several hoop strain responses during cooling down and excitation tests of outermost turns of the SC magnets are recorded to show that the split magnet system can be limited well to strain guidelines at the different operation stage, and the hoop strain at magnet’s circumference are almost the same during the operation. By strain characteristic exploration in the NbTi superconducting split magnet system, it can indicate that a structure stability for the magnet system during its operation. And based on FE analysis, we also calculate strain field of the split magnet system for the different operation stage, and the predicted results show good agreement with the experiment data.

Speaker: Beimin Wu (1 Key Laboratory of Mechanics on Western Disaster and Environment, College of Civil Engineering and Mechanics, Lanzhou University, Lanzhou, China; 2 Institute of Modern Physics of Chinese Academy of Science, China)

Beimin Wu-poster-Tue-Mo-Po2.05-02 [25].pdf

285 Tue-Mo-Po2.05-03 [26]: Performance Analysis and Testing of High Temperature Superconducting Magnet Impregnated with Composite Resin

An electromagnetic force has an important effect on the performance of high temperature superconducting magnet. The superconducting magnet can be impregnated with composite resin in order to improve its mechanical stability. A three dimensional model was established by COMOSL finite element analysis software to analyze the electromagnetic stress and strain. The results show that the maximum stress is 1.54104 N/m2 and the maximum strain is 3.3310-7 at the edge of superconducting tapes inside the superconducting coil. The critical current of the superconducting coil was measured by experiment before and after impregnation with composite resin, respectively. The attenuation rate was calculated to be only 3%. Thus, there is no or minor damage to the superconductor coil during the impregnation. That is to say, the impregnation process of the superconducting coil with composite resin was acceptable.

Speaker: Mr Zhenming Li

286 Tue-Mo-Po2.05-04 [27]: An Analytic Study on Electromechanical Conditions for Compressive Electromagnetic Stress in an HTS Magnet

Compressive magnetic radial stress is favored, over tensile one, for a high field magnet, mainly because it lowers the overall peak magnetic stress within the windings of the magnet. It is of particular importance for a no-insulation (NI) high temperature superconductor (HTS) magnet, because the compressive radial stress leads to “good” turn-to-turn contact that is essential for current sharing in the NI HTS coils and consequent self-protecting behaviors. This paper presents an analytic study to determine electromechanical conditions of an HTS magnet in order to make the magnetic radial stress to be compressive. Depending on key magnet design parameters such as target center field, magnet current density, inner winding diameter, and radial build, we have shown that electromechanical conditions for a high field HTS magnet to have compressive radial stress may be analytically pinpointed. The results may provide an insight for magnet engineers to better overview the electromechanical behaviors of their high field HTS magnets at the early design stage.

Acknowledgement
This work was supported by the National Research Foundation of Korea as a part of Mid-Career Research Program (No. 2018R1A2B3009249).

Speaker: Jeonghwan Park (Seoul National University)

Thu-Mo-Po2.04-04 [27]_EM_JP_20190920.pdf

287 Tue-Mo-Po2.05-05 [28]: Tensile properties of DyBaCuO low porosity bulk material melt-processed in oxygen atmosphere

It is well-known that REBaCuO, where RE denotes rare-earth elements, superconducting bulk materials can trap large magnetic field in the compact space. Since REBaCuO bulk materials are subjected to electro-magnetic force, improvements of the mechanical properties of REBaCuO bulk materials are indispensable for the development of high-performance devices. However, conventional REBaCuO bulk materials melt-processed in air contain pores. Pores cause degradation of the mechanical properties due to the reduction of net cross-sectional area and stress concentration around pores. In this study, the mechanical properties of a DyBaCuO low porosity bulk material melt-processed in oxygen atmosphere were evaluated. DyBaCuO bulk materials melt-processed in 50 and 75% oxygen atmosphere were also evaluated for comparison. The porosity was decreased by the increase of oxygen pressure, and few pores were observed for the bulk material melt-processed in oxygen atmosphere. The mechanical properties were evaluated through tensile tests for specimens cut from the DyBaCuO bulk materials. The mechanical properties of REBaCuO bulk materials are commonly evaluated through bending tests for specimens cut from bulk materials. However, the strength values evaluated through the bending tests are overestimated due to the limited maximum stress region in the bending test specimen. The tensile test specimens were glued to metal rods, and the tensile load was applied through the universal joints. The tensile strength was improved by the decrease of the porosity. The tensile strength values obtained in this study were lower than bending strength values reported elsewhere. Flow like patterns formed by the crack propagations were observed on the fracture surfaces of the specimens. Through the observations on the fracture surfaces, the fracture mechanisms are discussed both for the porous and the low porosity bulk materials.

Speaker: Prof. Akira Yamamoto (High Energy Accelerator Research Organization (JP))

Tue-Mo-Po2.05-05 [28].pdf

288 Tue-Mo-Po2.05-06 [29]: Frictional Force Effects Between Superconducting Tapes on Stress–Strain Characteristics of GdBCO Magnets

In designing high field magnets, the enormous mechanical stress on the magnets due to the Lorentz force must be considered. However, the common stress–strain calculations with BJR and/or force balance equation barely considered the frictional force between the superconducting tapes. In this study, the effects of frictional force between these tapes on the stress–strain characteristics were investigated using the intentionally scratched HTS tapes. Mechanical stresses of a magnet wound using the intentionally scratched GdBCO tape were empirically and analytically examined on the basis of the external pressure. The necessity of considering the frictional force between the superconducting tapes for the stress–strain analysis will be discussed in detail based on the test results.

[Acknowledgement]
This work was supported by the Materials and Components Technology Development Program of KEIT [10053590, Development of MgB2 wire and coil with a high critical current and long length for superconducting medical·electric power equipment].

Speaker: Mr Jimin Kim (Korea University)

289 Tue-Mo-Po2.05-07 [30]: Micromechanical properties evaluation of BaHfO$_3$-doped EuBCO coated conductors using a microcantilever beam method

REBCO coated conductor (CC) has been applied to high field magnets due to its high critical current density ($Jc$) and high tensile strength. In order to further improve in-field $Jc$, we have developed EuBCO CCs doped BaHfO$_3$ (BHO) as artificial pinning centers (APCs)$^{[1]}$. Since the EuBCO nanocomposite films with the BHO secondary phase is similar to the structure for improving the strength and fracture toughness in bulk ceramics$^{[2]}$, there is a possibility that the strength of the BHO-doped EuBCO CCs is also improved. However, it was difficult to directly measure the strength and fracture toughness of the superconducting layer in the CCs. As a new approach, we introduced the microcantilever beam method$^{[3]}$ to evaluate the micromechanical properties of the superconducting layer. Microcantilever beam specimens (~ $\mu$m) were formed in the superconducting layer by focused ion beam (FIB) processing. Their strengths were measured by bending tests using a nanoindenter. We will report on details of the test method and a comparison of the strength of the CCs.

Acknowledgments
A part of this work is based on results obtained from a project commissioned by the New Energy and Industrial Technology Development Organization (NEDO).

[1] S. Fujita et al., IEEE TAS., 28, 4 6600604 (2018).
[2] K. Niihara et al., J. Ceram. Soc. Jpn., 99, 974 (1991).
[3] J. Tatami et al., J. Am. Ceram. Soc., 98 3 965–971 (2015).

Speaker: Shogo Muto (Fujikura Ltd.)

290 Tue-Mo-Po2.05-08 [31]: Numerical evaluation on electromagnetic force and stress due to screening current in REBCO coil

The research and development on the applications of REBCO superconducting coil to the high field magnets for NMR, MRI, accelerator and so on are in progress. In coils wound with REBCO tapes, large screening currents are induced by the radial component of the magnetic field. The magnetic field due to the screening current (hereinafter referred to as screening current-induced field) is generated in the direction opposite to the field by the transport current, thus reducing the magnetic field, deteriorating the field homogeneity and affecting the time stability of the magnetic field. These problems of screening current have been discussed. However, the electromagnetic force due to screening current have not been discussed in detail yet. The screening current leads to non-uniform current distributions in the REBCO tape. Therefore, the distribution of electromagnetic force in REBCO coils is different from that at designing the coil assuming that the current uniformly flows on the cross section of coils. Thus, there is the possibility that the screening current is a serious problem in mechanical design of REBCO coils. In previous study, three-dimensional numerical simulation code has been developed to calculate the spatial and temporal behavior of screening current distribution in REBCO coil. The validity of the developed numerical simulation was confirmed by comparison with the experiments. In this study, we expand the developed numerical simulation code to calculate the electromagnetic force and stress due to screening current and discuss the mechanical strength structure of REBCO coil.

Acknowledgements
The part of this work was supported by TEPCO Memorial Foundation Research Grant (Basic Research) and JSPS Grant-in-Aid for Scientific Research (C) Grant Number 16K06222

Speaker: Prof. Hiroshi Ueda (Okayama University)

Tue-Mo-Po2.06 - MRI Magnets II

Conveners: Lionel Quettier (CEA Paris-Saclay), Shoichi Yokoyama (Mitsubishi Electric Corporation)

291 Tue-Mo-Po2.06-01 [32]: Several Key Issues in 14 Tesla Whole body MRI Magnet development

Understanding the human brain in neuro scale is one of the main scientific challenges in the future. The sub-micron Magnetic Resonance Imaging (MRI) is significant to the structural and functional research of the human brain. The important way to improve the resolution of MRI scanner is increasing the magnetic field B_0, as it is well known that the signal to noise ratio (SNR) is proportional to B_0: SNR~γ^(5/2) 〖B_0〗^(3/2). In the early 2000s, the French Alternative Energies and Atomic Energy Commission (CEA) launched a great program to conceive and build a ‘human brain explorer’, the first human MRI scanner operating at 11.7 T, the prospective resolution of this MRI scanner is 100 μm. now the magnet system of this MRI scanner is under test. After 11.7 T, the next challenge will be 14 T. Which can be anticipated that the ultra-high field (UHF) magnet system of 14 T MRI will be a great challenge of superconducting techniques, due to its such high field and large size of aperthe ture. In 2017s, Chinese government launched a program to develop the key technologies in 14 MRI magnet system. In the past year, several key issues have been set up and the corresponding R&D programs have been made, which will be discussed in this article.

Speaker: Chao Dai (Institute of Plasma Physics, CAS)

292 Tue-Mo-Po2.06-02 [33]: Magnetic and Finning Force behavior on Nb3Sn Strands Subjected to Transverse Deformation for 14 T MRI Superconducting Magnet

The Nb3Sn Rutherford cable and composite conductor is developed for 14T Magnetic Resonance Imaging (MRI) magnet project in China. Part of the project is devoted to the Electromagnetic (EM) behaviors studies of the deformed Nb3Sn strands from the cabling process. The magnetization characteristic of deformed Nb3Sn strands by artificial rolling method which simulates the transverse deformation is studied. The magnetization results are explained not only by the aspect ratio, but also the sintering or merging of sub-elements combined the microscopy analysis. The pinning force characteristic is also studied at 20 and 40 % deformation. The upper critical field (Bc2) and critical temperature (Tc) are derived. The results shows the Bc2 and Tc of the deformed strands are all degraded compared to the un-deformed strand and the possible explanations are discussed. The study permits to better understand and the pinning force behavior and transport current degradation of Nb3Sn strand from cabling process, which can provide the important reference for cable design and Nb3Sn strand choice.

Speaker: Prof. Shi Yi (Institute of Plasma Physics, China)

293 Tue-Mo-Po2.06-03 [34]: An optimal design approach for 14T actively shielded magnetic resonance magnets

The objective of the magnet design for MRI is first to ensure the field intensity and homogeneity in the central imaging area, and meanwhile to minimize the magnetic leakage of the stray field. Based on this, an optimal design method of 14T actively shielded MRI magnets is proposed in this paper. Firstly the current carrying region of the magnets is subdivided into two-dimensional array grids, in which each grid represents one actual conductor. Then the initial rectangular current distribution is obtained using linear programming in the grid region by a detailed consideration of the superconductor’s consumption, field intensity, imaging region homogeneity and stray field leakage range. The method of particle swarm optimization (pso) is adopted to optimize the final rectangular section of magnet with the limitation of the coil position and section size. In addition, target point sampling and spherical harmonic series elimination are proposed as two optimization strategies and are also compared to find the best design scheme. Finally the total length of this magnet design by four sets of coils is around 3.5m, and the inner diameter is nearly 1m. The detailed optimization design is presented in this paper.

Speaker: Mr Kaihong Wu (Institute of Plasma Physics,Chinese Academy of Science)

Tue-Mo-Po2.06-03[34] An optimal design approach for 14T actively shielded magnetic resonance magnets.pdf

294 Tue-Mo-Po2.06-04 [35]: Magnet design of a 7 T animal MRI scanner

A 7 T superconducting magnet was designed and under fabrication for animal magnetic resonance imaging (MRI). The magnet includes two primary coils, four compensating coils and three shielding coils. All the coils together produced a homogeneous magnetic field over an imaging sphere with diameter 0.130 m and the stray field was actively-shielded within an area at longitudinal length 3 m and radial length 2 m.
The magnet coils adopted NbTi superconducting wire with length 80.86 km and volume 0.11 m3. The operating current is 180 A for the target magnetic field strength. Under the electromagnetic circumstances, the maximum hoop stress reaches 106 MPa. The maximum magnetic field strength is 7.18 T with a current margin 83.8% and temperature margin 1.10 K at 4.2 K. The inductance of the magnet is 213.7 H and magnetic energy is 3.5 MJ.
The magnet coils were wound on four bobbins, where the first-layer primary coil and the second-layer primary coil occupied two individual bobbins, the four compensating coils were laid on one common bobbin and the three shielding coils also shared one bobbin. The fifth bobbin between the compensating coils layer and the shielding coils layer was scheduled to arrange the superconducting shim coils. The mechanical components were assembled with two end plates with 16 pull rods. The whole structure was immersed in liquid helium and surrounded in a cryostat to keep the superconducting wire at an extremely-low temperature environment.
The developed superconducting magnet has a 300 mm warm bore where a dedicated gradient assembly and radio-frequency assembly will be installed to establish a final imaging platform.

Speaker: Dr Yaohui Wang (Institute of Electrical Engineering, Chinese Academy of Sciences)

MT_yaohui wang-1.pdf

295 Tue-Mo-Po2.06-05 [36]: FEM modelling of superconducting whole body, actively shielded 7 T MRI segmented coil magnets wound using Nb3Sn strands

We present FEM results of a magnetic design study for 7 T, whole body, actively shielded MRI using Nb3Sn conductor. Nb3Sn strand was used to enable the development of short (1.4 m) segmented coil designs, as opposed to the nearly 2 m long compensated solenoid designs needed for NbTi machines. The use of Nb3Sn strand will allow a conduction cooled design, if quench is properly managed. We present two designs with magnetic field homogeneity better than 10 ppm (part-per-million) within DSV (Diameter of Spherical Volume) of 45 cm. Several classes of Nb3Sn strand especially designed for MRI applications were considered as a possible candidate for winding such magnets. The magnets were assumed to achieve maximum on-axis magnetic field of 7 T. For this on-axis field a peak field inside the magnet windings was determined and parameters of the required Nb3Sn strands (such as critical current, engineering current density etc.) calculated. The coil load lines were compared to the critical currents of the Nb3Sn conductors and we find that such a segment coil design can be achieved with several classes of existing Nb3Sn conductor. Coil geometry, length of conductor, and overall magnetic performance, and current and thermal margins are discussed. This demonstrates that a viable compact 7 T whole body MRI is achievable using Nb3Sn conductor.

Speaker: Milan Majoros (The Ohio State University)

296 Tue-Mo-Po2.06-06 [37]: Analysis of Gradient-Induced Eddy Current in a superconducting MRI Magnet

In superconducting magnetic resonance imaging (MRI) systems, time-varying eddy currents in the conducting cryostat structures are induced by switched gradient coils. These eddy currents increase thermal loads of the cryostat, create acoustic noise, lead to image distortion and limit the application of fast MR sequences. In this paper, a fast coupled circuit network method is employed to calculate the eddy current in the cylindrical cryostat structures induced by an active-shielded longitude gradient coil, with the consideration of temporal characteristic, exponential decay along the radial direction and skin depth. Also, the detrimental effects including powder deposition in the magnet cryostat and secondary magnetic field generated by the eddy currents are analyzed. To verify the accuracy, the eddy current measurements were carried out and compared with the calculated results. In addition, the eddy current distribution variation and related effects on magnet and gradient field caused by different axial mounting errors of the gradient coil were analyzed and discussed in detail. These results could provide meaningful engineering implication for improving the reliability and stability of superconducting MRI systems.

Speaker: Dr Qiuliang Wang (Institute of Electrical Engineering, Chinese Academy of Sciences)

Tue-Mo-Pp2.06-06 Analysis of Gradient-Induced Eddy Current in a Superconducting MRI Magnet.pdf

Tue-Mo-Pp2.06-06 Analysis of Gradient-Induced Eddy Current in a Superconducting MRI Magnet.pptx

297 Tue-Mo-Po2.06-07 [38]: An Optimal Target Field Approach for Passive Shimming In Superconducting MRI

In magnetic resonance imaging (MRI) system, the magnetic field homogeneity of the imaging area plays a decisive role in the quality of images. Due to assembly errors or the effects of the surrounding ferromagnetic material, the homogeneity fails to meet the design value, which makes the images deformation, and it is necessary to take measures to shim. Passive shimming uses the magnetization of iron pieces to compensate the magnetic field. In the existing algorithm, the target magnetic field value is fixed, usually the average or DC component of the magnetic field. However, the value is not the best, causing shimming inefficiency or even failure. The optimal target field approach firstly studies the influence law of the placed iron pieces on the magnetic field of a superconducting MRI. Then, the law is used to judge the change trend of the magnetic field and set an optimal target magnetic field value before shimming calculation. The optimal target field approach will reduce the rounds of shimming, improve the efficiency, and quickly improve the homogeneity during optimization.

Speaker: Dr Qiuliang Wang (Institute of Electrical Engineering, Chinese Academy of Sciences)

298 Tue-Mo-Po2.06-08 [39]: Design of the Superconducting Main Coils Based on Variable Density Method in MRI

The Magnetic Resonance Imaging system（MRI）is an important diagnosis and treatment method of modern medicine. Benefiting from the advancement of superconducting magnet technology, the performance of MRI is continuously improved. In superconducting MRI, the main coils, as the most critical components, greatly determines the quality of images, further affecting the diagnosis. Therefore, the performance of main coils is the criterion for evaluating the quality of MRI. The Variable Density Method (VDM), one of the Topology Optimization methods originated from mechanics, has rich model description approaches, fast solving speed and wide applicability. Since the distribution design of the main coils is highly similar to the mechanical structure design by VDM, it is reasonable to combines the traditional design methods of the main coils with VDM to build a new optimization model. Eventually, the superconducting main coils, which can produce high homogeneity magnetic field, are obtained and its complex shape is further optimized to be easily processed and formed.

Speaker: Dr Qiuliang Wang (Institute of Electrical Engineering, Chinese Academy of Sciences)

299 Tue-Mo-Po2.06-09 [40]: On the Accurate Calculating of Coil-tissue Interactions for Ultra-high Field MRI RF Coils Using a Hybrid MoM/FDTD Algorithm

In ultra-high field magnetic resonance imaging (MRI) systems, the wavelength of the radiofrequency (RF) field is comparable to the size of imaging object, thus causing complicated coil-tissue interactions, which can lead to detrimental changes of the magnetic field (B1 field) and thermal intensity in human tissue. However, the homogeneity of B1 field and safety is critical for the RF coil, which generate the need of accurate calculating for B1 field as well as specific absorption rate (SAR). In this paper, a huygence equivalent surface based hybrid method of moments (MoM) and finite-difference time-domain (FDTD) algorithm is used to calculate the B1 field and SAR for high frequency RF coils loaded with the human tissue. The frequency of 298MHz (7T),400MHz (9.4T) and 500MHz (11.75T) are simulated individually. Different kinds of RF coils are also modeled to achieve the best performance in separate frequencies. In addition, a well established finite element method (FEM) is also used to calculate the same problem as the hybrid method, which demonstrate the feasibility and superiority of MoM/FDTD technique. The results shown in this article may contribute to the fabrication of better RF coils.

Speaker: Qiuliang Wang (Institute of Electrical Engineering, Chinese Academy of Sciences)

Tue-Mo-Po2.07 - MRI Magnets III

Conveners: Lionel Quettier (CEA Paris-Saclay), Shoichi Yokoyama (Mitsubishi Electric Corporation)

300 Tue-Mo-Po2.07-01 [41]: Design of a Tabletop Liquid-Helium-Free, Persistent-Mode 1.5-T/90-mm MgB2 “Finger” MRI Magnet for Osteoporosis Screening

We have finalized the design of a full-scale tabletop 1.5-T/90-mm MgB₂ “finger” MRI magnet system for osteoporosis screening based on our preliminary test results of small coils and superconducting joints. The magnet will operate in persistent mode at 10 K with an additional 5 K temperature margin. The magnet design satisfies the required specification of a field homogeneity of <5 ppm over a 20-mm diameter of spherical volume (DSV) after cool-down and energization, and a fringe field of <5 gauss at 0.5 m in radius from the magnet center. A cryocooled solid nitrogen (SN₂) cryogenic system minimizes the heat input especially when the cryocooler is switched off to provide a vibration-free measurement environment during the MRI scanning. This paper covers designs of: 1) the main coils and an iron shield; 2) coil former structures; 3) cryogenic system 4) protection circuit; and analyses of 1) quench; 2) heat input into the cold mass; and 3) manufacturing tolerance sensitivity on field errors. The magnet system, to be constructed and tested in 2019, will in 2020 be equipped with a set of active-shielded gradient coils, an RF coil, and a 1.5-T MRI imaging system.

Acknowledgement: Research reported in this publication was supported by the National Institute of Biomedical Imaging and Bioengineering of the National Institutes of Health under award number R01EB022062.

Speaker: Dongkeun Park (Francis Bitter Magnet Laboratory / Plasma Science and Fusion Center, Massachusetts Institute of Technology)

(Poster) Tue-Mo-Po2.07-01 [41] Finger_MRI_Design(DkP-MIT_FBML)-online_submission.pdf

301 Tue-Mo-Po2.07-02 [42]: Design, manufacturing and testing of a high-field 2 + 3 T MgB2 dry magnet demonstrator

This paper presents the design, manufacturing and testing of a 2 + 3 T high field MgB2 ø178 bore solenoid magnet demonstrator (around 55 kgs). The magnet was designed to produce 2 T standalone at 10K and to be operated in a homogenous background field of 3 T. The magnet is helium free and is cooled down by a cryocooler. Three lengths of Columbus MgB2 conductors (1.6 kms) were used to wind the magnet linked together by two resistive junctions. The thermalization of the magnet and theses junctions is also addressed. A full set of instrumentation involving four punctual heaters and one azimuthal heater were implemented in the magnet for quench propagation studies along with voltage taps for current density control and operation. As it is a cryocooled magnet, in order to measure the temperature of the magnet, different parts of the magnet were equipped with cernox. The results of the first tests will be described and the magnet performances presented.

Speaker: Julien Avronsart (CEA)

Poster_MT26_Julien_AVRONSART.pdf

302 Tue-Mo-Po2.07-03 [43]: Charging, Discharging, and Over-current Characteristics of Partially Insulated MgB2 Magnet Using Cr-coated MgB2 Wires

Recently, we developed a 0.5-T/300 mm MgB2 magnet using the partial insulation (PI) winding technique that only employs layer-to-layer insulations without the turn-to-turn insulations; the magnet was self-protective but has a significant charge–discharge delay. In this study, the use of Cr-coated MgB2 wires was proposed as an alternative solution to enhance the characteristic resistance of the MgB2 magnet, in combination with the PI winding technique. The charging–discharging tests confirmed that the charging–discharging rates of the PI magnet that uses Cr-coated wires was ten times faster than the magnet that utilizes uncoated wires. In addition, the self-protective behavior of the PI magnet that uses the Cr-coated wires were verified via the over-current tests. Herein, the feasibility of employing the proposed winding technique for the development of self-protective MgB2 magnetic resonance imaging magnets with fast charging–discharging rates was discussed in detail.

[Acknowledgement]
This work was supported by the Materials and Components Technology Development Program of KEIT [10053590, Development of MgB2 wire and coil with a high critical current and long length for superconducting medical·electric power equipment].

Speaker: Mr Kihyun Kim (Korea University)

303 Tue-Mo-Po2.07-04 [44]: Suitable Excitation Method of REBCO MRI Magnet for Suppressing Screening Field Attenuation

The temporal stability of the magnetic field generated by an MRI magnet is of critical importance for higher resolution medical imaging. However, large screening currents are induced in High Temperature Superconducting (HTS) tapes such as REBCO tapes during the excitation, and attenuated after the excitation due to the flux creep of the HTS tapes. The temporal variation of the magnetic field due to the screening current attenuation in the HTS tapes is a critical problem to apply HTS magnets for MRI. We have verified the effectiveness of the pre-excitation, overshooting, and high temperature magnetization method for MRI magnets to suppress the screening current attenuation in the HTS tapes and the variation rate of the coil magnetic field down to 100 ppm/hour by using a small REBCO double pancake coil.
This study developed a 2 T class REBCO magnet for MRI and accurate magnetic field measurement system with an NMR probe to measure the magnetic field variation of less than 1 ppm/hour. We investigated the effectiveness of the overshooting and high temperature magnetization method to realize less than 1 ppm/hour as the temporal stability of the center field of the magnet, and clarified the suitable excitation method for HTS MRI magnets. Experimental results showed that the overshooting with less than +1% current and high temperature magnetization with the temperature change over 5 K greatly increased the temporal stability of the center field of the magnet at the operational temperature 4 - 20 K. We also clarified that the combined excitation method of the overshooting and high temperature magnetization method can realize the temporal stability of the center field less than 1 ppm/hour with a shorter time as well as smaller load factor of the REBCO magnet.

Acknowledgments: This work was supported by the New Energy and Industrial Technology Development Organization (NEDO).

Speaker: Yoh Nagasaki (Tohoku University)

304 Tue-Mo-Po2.07-05 [45]: A No-insulation YBCO Magnet using Multiple Flux Pumps as Sources to Improve Central Magnetic Field

A magnet consisting of five no-insulation (NI) double pancakes (DPs) has been constructed and tested. In this paper, operating currents in each excitation mode were optimized to achieve the highest magnetic field and three excitation modes of the magnet have been conducted in 77 K to compare. Test results showed the central magnetic field increased by multiple sources. Charging performance and electrical-magnetic transience of NI DPs have also been measured and analyzed. Finally, experiments in this paper verified the feasibility of using multi-flux pumps as DC power supply for MRI magnet consisting of NI coils, which greatly reduces the cost of charging and improves the central magnetic field.

Speaker: Wei Wang (Sichuan University)

920 wxq.pdf

920 wxq.pptx

305 Tue-Mo-Po2.07-06 [46]: A Study on the Effects of Iron Diffusion Barrier on the Magnetic Field Characteristics of MgB2 Coil

Generally, MgB2 wires possess a niobium diffusion barrier to prevent an unacceptable reaction between magnesium powder and copper stabilizer. However, given that niobium is costly, extensive studies were conducted to replace the niobium diffusion barrier with iron. Nevertheless, the MgB2 wire with iron diffusion barrier is not yet practically applied to magnetic resonance imaging magnets because the magnetization of ferromagnetic iron may lead to poor uniformity of the magnetic field distribution of the magnet. In this study, the magnetic field characteristics of solenoid magnet wound with MgB2 wire possessing an iron diffusion barrier were examined to investigate the iron barrier effects on the field homogeneity of magnets. In addition, the magnetic field drift of the magnet in a persistent current mode operation was presented. For a comparative analysis, an MgB2 magnet that utilizes conventional wires with a niobium diffusion barrier was also assessed.

[Acknowledgement]
This work was supported by the Materials and Components Technology Development Program of KEIT [10053590, Development of MgB2 wire and coil with a high critical current and long length for superconducting medical·electric power equipment].

Speaker: Jiman Kim (Kiswire Advanced Technology)

306 Tue-Mo-Po2.07-07 [47]: Presentation withdrawn

307 Tue-Mo-Po2.07-08 [48]: Development and construction of an actively shielded zero boil-off 7T/700 bore magnet.

Since UHF MRI offer the possibility to study in a deeper way the brain functionality, these kind of magnets are becoming essential in neuroscience research. ASG is involved in this sector with an active shielded, zero boil-off 7T/700 bore magnet. The magnet with stringent dimensional parameters has been designed and developed by ASG superconductors team for Magnex MS Inc., in order to fulfil all the main characteristics but with a special address to respect the overall system height, length and weight. A magnetic configuration, observing all the required parameters, has been developed through the use of a dedicated software. Since one of the most important requirement is the zero boil-off, a deepened thermal study has been implemented. The magnet design phase is terminated and we expect to finish the manufacturing and testing phases within October 2019.

Speaker: Dr Martina Neri (ASG Superconductors)

MT26_7T_ASG.pdf

Tue-Mo-Po2.08 - Resistive Magnets for Accelerator and Fusion II

Conveners: Helene Felice (CEA Paris-Saclay), Michele Modena (CERN)

308 Tue-Mo-Po2.08-01 [54]: Presentation withdrawn

309 Tue-Mo-Po2.08-02 [55]: Radiation resistant magnets for the Super-FRS of the FAIR project

The radioactive dose rate in the area behind the target of the Super-Fragment Separator (Super-FRS) will be so high that most organic materials will be destroyed in a short period of time. After 20 years of operation an accumulated dose of more than 280 MGy is expected at the most critical parts. Special magnets consisting of radiation resistant materials must be used. Three dipoles, three quadrupoles, and two sextupoles are required inside the target area.
One radiation resistant dipole with its adjustable support frame already exists. The yoke of the dipole mainly consists of 100-120 mm thick iron blocks. The coil is wound of mineral insulated cables (MIC) without cooling channels. The water cooling is realized with layers of radiators between double pancakes of cables.
After the operation of the Super-FRS is started, direct access to the magnets is impossible because of the high radiation. Misalignment due to settlement must be corrected with remote alignment. A one meter thick plate of steel above the magnets will separate the high radiation area from a temporary accessible service tunnel above the steel shield. The remote alignment will be done with bars and angle gears from the service tunnel.
The water and current supply will be also carried out through the 1000 mm shield with tubes and copper bars. The connections at their radiation resistant interfaces will be joined remotely too.
Several magnetic and thermal tests have been successfully done with the existing dipole. But unexpected problems appeared during the tests and development of the adjustable support frame below the massive 90 tons magnet.
The knowledge gained from these tests has been incorporated in the specifications of the other radiation resistant magnets. The test results, the problems, the solutions, and the characteristics of these magnets will be presented.

Speaker: Hanno Leibrock (GSI Helmholtzzentrum für Schwerionenforschung GmbH)

mt26_poster_TUE_MO_PO2_08_02_55.pdf

mt26_poster_TUE_MO_PO2_08_02_55.pptx

310 Tue-Mo-Po2.08-03 [56]: The New Magnet System for the East Area at CERN

The East Area (EA) is a facility for experiments, beam tests and irradiation operated at the CERN Proton Synchrotron since over 55 years. The experimental area requires high availability, which has been increasingly jeopardized due to the age and reduced reliability of the installed components, in particular magnets and power supplies.
The CERN management has then decided to completely renovate this experimental area. The new system will feature a reduction of the power consumption by one order of magnitude obtained by operating the magnets in cycled mode instead of DC, and a better transmission and purity of the secondary beams thanks to a redesign of the beamlines.
The new EA magnet system consists of 12 different magnet designs with a total 58 magnets: 15 bending magnets, 31 quadrupoles and 12 correctors. This paper describes the design of all magnet types, as well as the status of manufacture and tests.

Speaker: Jaime Renedo Anglada (CERN)

Poster_template_MT26_v2.pdf

311 Tue-Mo-Po2.08-04 [57]: The upgrade of the CERN Proton Synchrotron Booster transfer line magnets

The CERN PSB (Proton Synchrotron Booster) is currently under-going a major upgrade with an increase in both injection and extraction energy. With the connection of the new LINAC 4, which replaces the now decommissioned LINAC 2, the energy of the beam to be transported to the PSB is increased from 50 MeV to 160 MeV. Simultaneously, the PSB will be upgraded to provide protons to the CERN PS (Proton Synchrotron) with an increase of energy from 1.4 GeV to 2 GeV. This corresponds to an increase of two times at injection and by 30% at extraction the beam rigidity and thus field requirements of the transfer line magnets into and from the PSB respectively. To cope with these increases, more than 40 magnets in the transfer lines to and from the PSB will be replaced with new magnets. This paper gives an overview of the challenges and chosen solutions concerned by this upgrade.

Speaker: Antony Newborough (CERN)

MT26_Newborough.pdf

312 Tue-Mo-Po2.08-05 [58]: The Design and Manufacture of the 90 Degree bending Magnets for Proton Beam Therapy

Proton beam is an effective means of radiotherapy for tumors. During the transmission of the proton beam from the accelerator to the treatment head, the direction of the beam is usually changed by the magnetic field generated by dipole magnet. A variety of magnets are arranged in a radiotherapy system using a rotating gantry for proton beam transmission. The 90 degree magnet is placed above the treatment head that move with the rotation of the gantry and concentric with the rotating gantry. The iron core of the magnet is often stacked with silicon steel sheets with high magnetic permeability and low loss. The outer coil is wound with oxygen-free copper conductor with water cooling in the middle. This article will describe the details of design and manufacturing process of a 90-degree bending magnet on the proton therapy rotating gantry.

Speaker: Mr Zhihong Liu

313 Tue-Mo-Po2.08-06 [59]: Design and Test of an Octupole Scanning Magnet for Proton Therapy

Proton beams have several features that make them very effective in radiation therapy applications. These include high dose localization as well as high biological effect around the Bragg peak. Moreover, magnetic scanning methods allow one to spread an ion beam to an exact image of a complex tumor shape. The ion scanning system usually consists of two magnets, each scanning horizontal and vertical directions independently. This paper discusses the design for a novel octupole magnet design that provides beam deflection over a dipole field which can be set up at any azimuthal angle in the volume of the magnet bore. A test of the static and dynamic performance of the octupole scanning magnet has been performed using Hall probes and coils to measure the field inside the magnet and the results are presented in this paper.

Speaker: Mr Lianhua Ouyang (Shanghai Institute of Applied Physics, CAS)

Design and test of an Octupole Scanning Magnet for Proton Therapy.pdf

314 Tue-Mo-Po2.08-07 [60]: Consideration of misalignment and fringe field of beamline elements in a proton therapy facility

Proton therapy is regarded as one of the most advanced radiotherapy methods for its unique Bragg Peak. As a medical apparatus, the proton therapy facility must deliver stable and accurate dose or proton beams to patients. Huazhong University of Science and Technology (HUST) was funded in 2016 to build such a machine, known as HUST-PTF. The HUST-PTF uses a superconducting cyclotron to produce 250 MeV proton beams with highest current of 500 nA. The facility will be equipped with two 360-degree gantries and one fixed treating room. The transport beamline needs to accurately adjust the beam energy and deliver proton beams from the cyclotron to each treating room according to the treating plan. For consideration of compactness and economy, the beam pipe is designed to twice of the beam RMS size, which sets rigorous requirements on the beam orbit and optical design. So, fringe field and misalignment are the two main factors needed to be considered during the design phase. We studied the effects of fringe field of the bends and interference between the quadrupoles and steering magnets on beam optics, based on which optimized working points were proposed. We also analyzed the influence of misalignment of the bends and quadrupoles on beam orbit, based on which a global correction scheme was designed.

Speaker: Dr Qushan Chen (Huazhong University of Science and Technology)

315 Tue-Mo-Po2.08-08 [61]: Correction magnet with Permanent magnets

Correction magnets with permanent magnets are investigated. They need to generate both polarities of magnetic fields, which can be realized by rotating permanent magnet rods. Such a magnet system will reduce not only electricity but also maintenance cost. The structure and the field adjustment scheme of a trial conceptual design will be discussed.

Speaker: Dr Yoshihisa Iwashita (Kyoto University)

MT26steer7.pdf

316 Tue-Mo-Po2.08-09 [62]: Magnetic Property of Praseodymium Permanent Magnet at Cryogenic Temperature

Strong magnetic fields are demanded for advanced accelerators. As a cost-effective option other than HTS (High Temperature Superconductors), permanent magnets may be applied in the hybrid magnets to generate the strong magnetic field. One of the most promising permanent magnetic materials for the hybrid magnets is praseodymium permanent magnets (PrFeB). Although the remanent field of conventional NdFeB magnets decreases at 100 K due to spin reorientation. PrFeB magnets consisting of praseodymium (Pr) instead of neodymium (Nd) do not show such degradation and the coercivity of PrFeB at 100 K region is 7 T. In this study, magnetization curve, as a primary magnetic property of a PrFeB magnet sample was measured in the temperature range down to 4 K. Based on the experimental result, possibility of applications for accelerator magnets will be discussed.

Speakers: Yasuhiro Fuwa (Kyoto University), Yoshihisa Iwashita

Tue-Mo-Po2.09 - REBCO Wires & Cables I

Conveners: Prof. Tetsuo Oka (Shibaura Institute of Technology), Vitaly Vysotsky (Russian Scientific R&D Cable Institute)

317 Tue-Mo-Po2.09-01 [63]: Influence of GdBCO stoichiometry on the superconducting properties of industrial 2G HTS wire in magnetic field

We prepared a series of 2G HTS wires with systematically varying gadolinium content in the GdBCO layer grown by pulsed laser deposition (PLD) and characterized by them by transport Ic measurements over wide ranges of temperature (T) and magnetic field (H). The samples were fabricated using commercial production equipment at SuperOx and contained different concentration of Gd, starting from the standard production composition and with additions of 15, 30 and 45% of excess Gd. The critical current was density determined from hysteresis loops using PPMS in the 0-8 T field range from and at temperature from 4.2 to 77 K. The resistivity curves of the samples were also measured using PPMS in the field range from 0 to 9 T in the orientation from H||c (θ = 0°) to H||ab (θ = 90°) at 30° increments. In this case, the curves were obtained by the 4-probe technique with a 100 mA measuring current. From these curves the irreversibility temperature, Tirr, was derived as the beginning of the resistive transition. We replotted the Tirr(H) curves as irreversibility field lines Hirr(T) and scaled those data using the relation for the effective field for rotated sample: H_eff=H*√(γ^2 〖sin〗^2 θ+〖cos〗^2 θ). The activation energy, Ua, derived from the log(ρ/ρ0) against 1/T plots was almost constant in the whole angular range, with a small peak at H||ab. The Ua(θ) curves looked similar for all samples; the activation energy as well as the critical temperature decreased with the increase of gadolinium content. The real (χ’) and imaginary (χ”) part of magnetic susceptibility were measured in the 0-3 T field range. At high magnetic field the transition of χ’ moves to low temperature and becomes wider for all samples. The maximum of χ” also appreciably moves to low temperature. The obtained experimental results are evidence of different pinning structure mechanism in the samples.

Speaker: Pavel Degtyarenko (JIHT RAS)

Tue-Mo-Po2.09-01 [63] Degtyarenko.pdf

318 Tue-Mo-Po2.09-02 [64]: Mechanical properties of BaHfO3-doped EuBCO coated conductors fabricated by hot-wall PLD on IBAD template

REBCO coated conductors (CCs) are promising for high field magnets because of their high in-field critical current density (Jc) performance and high tensile tolerance. To further enhance the in-field Jc, doping artificial pinning centers (APCs) such as BaMO3(M : Zr or Hf etc.) into REBCO film is well known technique. We have developed BaHfO3 (BHO) doped EuBCO CCs using a hot-wall type pulsed-laser-deposition (PLD) with productive high growth condition on ion-beam-assisted-deposition (IBAD) template. We have investigated and discussed the in-field Jc of BHO-doped EuBCO CCs and confirmed that the in-field Jc is certainly improved by introducing the APCs. However, mechanical strength is also one of the most important properties for high field magnet applications because superconducting wires are subjected to various intense stresses in a high-field magnet. Furthermore, strain dependence of Jc in reversible region is also an interesting phenomenon, which is important for magnet design.
In this study, we investigated the degradation characteristics of BHO-doped EuBCO CC tapes with 50 m-thick and 4 mm-wide Hastelloy substrate and 20 m-thick copper plating under various stresses such as tension and compression. In the tensile test in the tape longitudinal direction, irreversible degradation of critical current (Ic) was not confirmed up to about 600 MPa, and even with a repetitive tensile test of 1,000,000 times at 500 MPa. Also Ic degradation was not confirmed under the compressive stress up to 100 MPa in the tape width direction, and up to 400 MPa in the tape surface vertical direction. In addition, the strain dependence of Ic in the reversible region and the mechanical properties under low temperatures and magnetic fields are also reported in detail.

Acknowledgements
A part of this work is based on results obtained from a project subsidized by the New Energy and Industrial Technology Development Organization (NEDO).
A part of this work was performed at the High Field Laboratory for Superconducting Materials, IMR, Tohoku University.

Speaker: Mr Shinji Fujita (Fujikura Ltd.)

MT2019_Tue-Mo-Po2.09-02_S_FUJITA.pdf

319 Tue-Mo-Po2.09-03 [65]: Design and electromagnetic characteristics study of YBCO cable for fast cycled accelerator magnet applications

The development of second generation high temperature superconductors (HTS) cable with larger current capacity and lower AC loss are very promising for building fast cycled accelerator magnets. In order to enhance the properties of HTS cable under the different physical fields, several HTS cable structure suitable for magnet application have been proposed by twisting, transposition, stacking, narrowing techniques. Compared to the existing HTS cable composed of the original wire with 4mm-12mm width, we utilize several narrow wires with width under 2mm to manufacture HTS cable. A novelty HTS cable comprised of stacked tapes wound on a helically slotted core has been proposed. Firstly, the critical current and n-value of HTS cable under the various mechanical force will be presented and discussed. Also,a numerical method introduced in this paper are based on H-formulation, and is used to calculate the current distribution and electromagnetic fields in HTS cable.

Index Terms: YBCO, Cables, critical current, H-formulation, Ac loss

Speaker: Zhuoyue Du (Institute of Modern Physics ,Chinese Academy of Science)

320 Tue-Mo-Po2.09-04 [66]: Determination of the thermal resistance between pressed copper-copper and copper-stainless steel interfaces for high current HTS Cable-in-Conduit Conductors

High Temperature Superconductors (HTS) are currently considered as promising candidates for high current Cable-In-Conduit Conductors (CICC) for large high-field magnets. In many cases, these CICC are formed from several HTS strands which themselves are formed from individual HTS tapes. These stranding concepts often use stacks of tapes or wrapped-tape arrangements.
Large effort is presently made to investigate the performance of these conductors during quench by modelling the entire structure. One important parameter which determines the quench performance is the current and heat transfer between the individual elements of the CICC, e.g. HTS REBCO tapes, normal-conducting metal parts (e.g. copper or stainless steel) and combinations thereof. As HTS REBCO tapes for high-field magnet application are usually encapsulated by a copper sheath, the problem reduces to the thermal resistance between pressed copper-copper and copper-stainless steel interfaces, which has been investigated experimentally by measuring the thermal conductivity of stacks made of copper strips and of copper-stainless steel strips as a function of temperature. With the knowledge of the thermal conductivity of copper and stainless steel basic material, the thermal conductivity of the interfaces was evaluated and compared to the values used until now. The resultant thermal resistances will be used in coming modelling, for example in a CICC for future fusion magnets being formed of six HTS CrossConductor (HTS CroCo) strands twisted around a central copper core forming a round cable which is embedded in a stainless steel jacket.

Speaker: Dr Walter H Fietz (KIT)

321 Tue-Mo-Po2.09-05 [67]: Numerical Study on AC Loss of Quasi-isotropic Superconducting Strand in AC Magnetic Fields at Low Temperature

Abstract —This paper mainly presents an AC loss numerical calculation of the superconducting strand in AC magnetic fields at 4.2K. Quasi-isotropic strands fabricated by second generation wires are stacked to a center symmetric structure. A 2D simulation model of strands was established based on the finite element simulation software Comsol Multiphysics，from which the distribution of magnetic field is obtained. AC loss contribution, including eddy loss and hysteresis loss, were estimated in detail in AC magnitude field. The effects of the magnetic field frequency and amplitude are also particularly considered. This paper is helpful for understanding the AC losses of quasi-isotropic strands and useful for the application of high magnetic field at low temperature.
Key words——superconducting strand，cryogenic temperature，eddy loss，hysteresis loss

Speaker: Yiran Meng (North China Electric Power University)

poster.pdf

poster.pptx

322 Tue-Mo-Po2.09-06 [68]: Mechanical and electro-mechanical investigations of assembled HTS CroCo triplets

High Temperature Superconductor CrossConductor (HTS CroCo) is manufactured by soldering REBCO tapes of two different widths in a cross-shape form. In a new long length fabrication process, the HTS CroCos are already embedded in solder to obtain a round outer shape. This allows to add an outer copper tube around such an HTS CroCo for increased mechanical and electrical stability. The mechanical and electro-mechanical properties of HTS CroCos fabricated from REBCO tapes of different widths, with and without additional copper encapsulation is investigated and compared.
In a high-current cable-in-conduit conductor (CICC), several HTS CroCos can be cabled to achieve the required current. The smallest multi-strand conductor is a triplet of such HTS CroCos. Based on the performance of the individual HTS CroCos under bending and transversal loading conditions, an HTS CroCo triplet CICC will be designed for operation at high-currents (>10 kA) and high magnetic fields (>10 T). Operating the triplet under such conditions will inevitably lead to high Lorentz forces acting on the strands of the triplet-CICC.
In order to investigate the electromechanical performance of cabled HTS CroCo triplet samples prior to their use in a large high-field demonstrator, short triplet samples will be loaded with transversal mechanical pressure in a universal testing machine at 77 Kelvin, self-field, to simulate the Lorentz forces of the intended high-current, high-field application. The maximum allowable transversal load will be investigated for different triplet sample arrangements in order to determine design limits for the triplet winding demonstrator.

Speaker: Walter H. Fietz (KIT)

_Nickel - Tue-Mo-Po2.09-06_E.M.Investigation_of_CroCo_triplets.pdf

323 Tue-Mo-Po2.09-07 [69]: Study on Mechanical properties of Superconducting conductor on Round Core at 77K

Superconducting Conductor on Round Core (CORC®) cables with scalability, flexibility, strong mechanical strength and high current density have become practical conductors in high-field magnets for fusion machines and particle accelerators. However, when it works in a high background magnetic field, the high mechanical stresses that generated in the CORC® conductor can result in irreversible degradation of the conductor. This paper presents the study on mechanical properties of CORC cables. Firstly, a 60cm-long CORC® short sample is fabricated, and its fundamental parameters are measured by experiments, including self-field critical current. Then, the effect of two typical mechanical stresses including longitudinal tensile stress, transverse compressive stress on the critical current of CORC cables has been investigated, respectively. And discussions are carried out by numerical modeling based on multi-physics finite element method. Conclusion obtained in this paper can not only verify the feasibility of CORC cables application in high magnetic field, but also provide valuable guidance in application limit of CORC cables.

Speaker: Ms Wenrong Li (Shanghai Jiao Tong University)

324 Tue-Mo-Po2.09-08 [70]: Performance Degradation of YBCO Tape with Different Stabilizing Layers under Cyclic Mechanical Stress

High temperature superconducting tapes are subject to periodic stresses and strains during AC applications, which may cause performance degradation of HTS tapes. In response to this problem, we built a periodic stress fatigue test platform for HTS tapes, and tested the critical current degradation characteristics of YBCO tapes with two different stabilizing layers under periodic stress. The causes of the critical current degradation of YBCO tape are analyzed. The effect of stabilizing layer materials on the fatigue properties of YBCO tapes are also discussed.

Speaker: Dr Ying Xu (Huazhong University of Science and Technology)

Tue-Mo-Po2.09-08 [70].pdf

325 Tue-Mo-Po2.09-09 [71]: Performance Degradation of YBCO Tape Under Overcurrent Considering Different Heat Exchange Conditions

The performance degradation of High Temperature Superconducting (HTS) tape, which may be influenced by various heat exchange conditions due to device structure, is of significant for life assessment of HTS devices under repetitive overcurrent. In this paper, considering stabilizing layer materials and heat exchange conditions, a series of repetitive overcurrent experiments were carried on YBCO tapes under 50Hz sinusoidal alternating current. The degradation of critical current of YBCO tapes after repetitive overcurrent was recorded. After comparing the performance degradation of tapes, the internal mechanism that each factor influences the degradation was analyzed and the key factor was obtained. The research could provide a reference for the design and life assessment of HTS devices.

Speaker: Guilun Chen (Huazhong University of Science and Technology)

Tue-Mo-Po2.09-09 [71].pdf

326 Tue-Mo-Po2.09-10 [72]: Investigation for Thermal Stability of Quasi-isotropic Superconducting Strand Stacked by 2mm Wide REBCO Tapes With Different Sheaths

Abstract-- In order to improve the engineering current density of high-temperature superconducting strand, we developed a kind of quasi-isotropic superconducting strand stacked by 2mm wide REBCO tapes. Minumum quench energy (MQE) and quench propagation velocity (QPV) of quasi-isotropic superconducting strands with copper, aluminum and stainless steel sheaths in liquid nitrogen (LN) were investigated numerically and experimentally in this paper. The numerical results are strong textin accord with the experiment, indicating that the developed numerical method can effectively simulate the thermal stability of this kind of strand immersed in liquid nitrogen and it can be applicated in high-current electric power transmission with high stability.
Index Terms--Thermal stability, quasi-isotropic superconducting strand, minumum quench energy, quench propagation velocity

Speaker: Ziqiu Liu (North China Electric Power University)

Ziqiu Liu.pdf

Tue-Mo-Po2.10 - REBCO Wires & Cables II

Conveners: Prof. Tetsuo Oka (Shibaura Institute of Technology), Vitaly Vysotsky (Russian Scientific R&D Cable Institute)

327 Tue-Mo-Po2.10-01 [73]: Structural Modelling of HTS Cable-in-Conduit Conductor with Helically Slotted Aluminum Core for High-Field Magnet Applications

A structural model has been developed for the Cable-in-Conduit Conductor (CICC) made with 2G HTS superconductors inserted in a helically slotted aluminum core (concept proposed by the ENEA Superconductivity laboratory [1]). The cable is particularly suited for high-field applications and consists of a twisted aluminum core and five helical slots. Each slot accommodates a stack of twenty REBCO tapes. The cable is equipped with a central cooling channel and an aluminum jacket.
In this work, finite element analysis is used to predict the electrical performance of the cable as function of the bending diameter. Modelling results are compared with experimental results obtained at 77 K. The experiments were carried out to investigate the smallest bending diameter achievable without critical current degradation. This aspect is particularly important for a magnet design, as the cable needs to be bent to form the desired coil’s shape.
The model consists of three parts: compaction of the aluminum jacket on the slotted core (each slot filled with the HTS stack of tapes), cable’s bending and thermal cooldown (from room temperature to 77 K). The electrical performance is then calculated from the obtained strain distribution of the stack taking into account the axial strain dependence of the critical current measured on single tape. Once the model is validated using the experimental results available, an alternative CICC cable, made with a copper core will also be evaluated numerically to highlight the effect of the core material properties (thermal and mechanical) on the strain distribution of the tapes after bending.
The numerical modeling will provide important information on the strain state of the tape-stacks and can be used to investigate the behavior of the more recently developed 6-slots cable and optimize future configurations.

[1] G. Celentano et al “Bending Behavior of HTS Stacked Tapes in A Cable-In-Conduit Conductor With Twisted Al slotted Core,” IEEE Trans. Appl. Supercond., accepted for publication

Speaker: Federica Pierro (Tufts University)

MT26_Poster_v2.pdf

328 Tue-Mo-Po2.10-02 [74]: Electromechanical analysis of simplified CORC® cable configurations: experiments and FE modeling

High current superconducting CORC® cable or wire is composed of spiraled HTS REBCO tapes in multiple layers. The cable combines isotropic flexibility and high resilience to electromagnetic and thermal loads. The flexibility of the cable is limited by the critical strain value damaging the REBCO layer in the tape. In order to optimize the manufacture conditions and operating performance, the mechanical behavior of CORC® cable must be understood for the different relevant loading conditions. A set of bending experiments is performed on simplified CORC® cable and wire configurations. The impact of non-bending factors such as current conduction through the copper core, thermal cool-down cycles, and position of voltage taps are studied experimentally. These influences are accounted for proper comparison with the FEM analysis. Bending on insulated core samples is also performed to avoid the current conduction through the copper core. The flexibility of the CORC® cable and wires are highly influenced by the friction between tapes and cable core. Experimental analysis is performed to determine the effect of lubrication on electrical contact resistance between tapes. A simplified electrical network model is used to analyze the effect of current sharing with the core. High current CICCs made from CORC® cables and wires experience transverse compressive stresses during operation. A FEM analysis on multilayered CORC® cable and wires is carried out to check the influence of various design factors in the overall operational performance.

Speaker: Anvar V A (University Of Twente)

MT26 Electromechanical analysis of simplified CORC® cable configurations.pdf

329 Tue-Mo-Po2.10-03 [75]: Relevance of current density in copper stabilizer for quench protection of coated conductors

Material scientists have been leading the R&D of coated conductors, and they have been focusing on increasing critical currents and lengths of coated conductors. Thanks to their efforts, long coated conductors with large critical currents are commercially available now. However, when we look back over the history of R&D of low Tc superconductors, stabilization using copper was a breakthrough to their practical applications. The amount of copper, i.e. the current density in copper stabilizer, is one of the critical factors for their stabilization and quench protection. It must be same in coated conductors, and the effect of copper stabilizer in coated conductors has been studied by various authors, but their approaches were mostly theoretical. The objective of this study is reminding of the relevance of current density in copper stabilizer for quench protection of coated conductors by using a well-organized set of experimental data.
We carried out experiments using short pieces of coated conductors in order to simulate the initiation phase of quench of a magnet. Slow normal zone propagations in coated conductors allow us such simulating experiments. We conduction-cooled 180 mm-long coated conductor samples, and initiated quenches using small resistive heaters. An FPGA module enabled us monitoring the sample voltage and controlling the output current of a power supply. Once the monitored sample voltage reached a threshold value (simulating a quench detection in a magnet), the output current of the power supply was decreased exponentially (simulating the decay of the magnet current by a dump resistor). Series of experiments were done using coated conductors with 20 micron-thick plated copper and those with 40 micron-thick plated copper, and the conditions for successful quench protection were compared.

This work was supported in part by the JST under the S-Innovation Program and in part by the MEXT under the Innovative Nuclear Research and Development Program.

Speaker: Xijie Luo

Tue-Mo-Po2.10-03.pdf

330 Tue-Mo-Po2.10-04 [76]: Direct Measurement of Modified Interconductor Contact Resistance Values in Coated Conductor Stacks and Roebel Cables

Interconductor contact resistance (ICR) is a key property in determining the stability and current sharing of coated conductor cables. Most coated conductor cables have relatively high contact resistance and low current sharing as fabricated because of surface asperities and the oxide layer that forms on the Cu-stabilizer. Here we work to quantify the induced differences in using three methods to modify ICR: sample “curing”, electrodeposition surface modification, and thin conformable inserts. At first a stack of two coated conductors was used to simulate a cable. This stack was put under transverse pressure and exposed to moderate temperatures to promote diffusion bonding via the removal of the unstable Cu-oxide layer (< 200 °C). Such a method would normally be applied after (e.g. magnet) winding. In a second approach, the samples stack surfaces were modified with a Cr, Ag, Nickel, and Nickel/Teflon nanocomposite layer. In a third approach, a conformable “smart material” was inserted into the stack. ICR measurements were performed on stacks before curing, after curing, for stacks with electrodeposited layers, and for stacks with a smart material insert. In addition, Roebel cables were prepared with electrodeposited coatings on the individual strands, and ICR was compared between the as-received and electrodeposited Roebel cables.

Speaker: Chris Kovacs (The Ohio State University)

MT26 ICR poster Kovacs II.pdf

MT26 ICR poster Kovacs II.pptx

331 Tue-Mo-Po2.10-05 [77]: In-Field Current Transport Properties in Long Length IBAD-PLD REBCO Tapes under the Influence of Local Ic Variation

Spatial homogeneity is one of the most important issues for practical applications of REBCO based magnets. Reel-to-reel Ic measurement is now widely used for the investigation of local Ic variation, however, these measurements are limited at low magnetif field around self-field and at 77 K in most cases, whereas practical operation condistions of superconducting magnets are higher magnetic field, B, and lower temperature, T. Furthermore, the relationship among the positional Ic variation, transport Ic and n-value in the long REBCO tapes is not yet fully understood.
In this study, we carried out spatially resolved Ic measurement in IBAD-PLD processed REBCO tapes under external magnetic field up to 5 T and down to 35 K by combining reel-to-reel contimuous measurement and in-field scanning Hall probe microscopy. We have also succeeded in measuring local n-value in the tape continuously with a spatial resolution of 1 mm. These measurements allow us to obtain deep insight into the controlling factors of B, T and position dependences of the current transport properties of REBCO tape. We confirmed good correlation between the measurements at low-field, 77 K and at in-field lower temperatures. Also, the positional dependence is almost independent from measurement conditions such as B and T. This strongly suggests that the B and T dependences are dominated by uniform flux pinning in a mesoscopic scale while the local Ic variation is mainly originated from current blocking obstacles in a macroscopic scale. Based on this understanding, we also propsed a multi-scale model to describe global current-voltage characteristics, i.e., transport Ic and n-value of long length REBCO tapes analytically. This is useful for describing properties in a long length magnet winding under practical operation condisions.
This work was supported by JSPS KAKENHI Grant Number 16H02334 and the New Energy and Industrial Technology Development Organization (NEDO).

Speaker: Takanobu Kiss (Kyushu University)

332 Tue-Mo-Po2.10-06 [78]: Extra fine filamentation with width below 100 μm by ESPC method in RE123 split wire

The filamentation of tape shaped RE123-coated conductors is important to reduce the shielding current from RE123 superconducting layer [1] in development of a high-field magnet such as NMR and MRI. In last year, we reported the development of split wire with 16-main-core by electrical separating by bending stress (ESBS) method [2]. In this study, to obtain more main-core, an electrical separating by pressure concentration method (ESPC) without a large bending of tape was adopted. We also improved the equipment that can produce above 12 cores simultaneously. In experiments, a 30-main-core sample was prepared and the average widths of main-core and sub-core are ~70 and ~10 μm, respectively. The results in microstructure and performances, such as critical current, with manufacturing method by the ESPC method, will be discussed in upcoming MT26 at Vancouver.

[1] Xinzhe Jin, Hidetoshi Oguro, Yugo Oshima, Tetsuro Matsuda and Hideaki Maeda, "Development of a REBa2Cu3O7-δ multi-core superconductor with “inner split” technology," Superconductor Science and Technology 29 (2016) 045006 (8pp)
[2] Xinzhe Jin, Yasuteru Mawatari, Toshihiro Kuzuya, Yusuke Amakai, Yoshinori Tayu, Naoki Momono, Shinji Hirai, Yoshinori Yanagisawa, Hideaki Maeda, "Fabrication of 16-main-core RE123 split wire using inner split method," IEEE Transactions on Applied Superconductivity (in press)

Acknowledgements:
This work was supported by the MEXT project of Leading Initiative for Excellent Young Researchers (LEADER) in Japan (Project ID: 16810210).

Speaker: Dr Shintetsu Kanazawa (Muroran Institute of Technology)

Tue-Mo-Po2.10-06 [78].pdf

333 Tue-Mo-Po2.10-07 [79]: High-field electrical transport properties of THEVA GdBa2Cu3O7 coated conductors

High-temperature superconducting (HTS) tapes are promising materials for developing high-field magnets for fields exceeding 30 T. Therefore, it is important to characterize their properties at high fields, in particular, the critical current, $I_{\rm c}$. One of the promising types of HTS tape is produced by THEVA where the architecture of the tape is unique and simple. Nowadays, these tapes show self-field $I_{\rm c}$ at 77 K of about 600 A/cm-width, among the highest reported. Moreover, since the microstructure of GdBCO in these tapes has a tilted orientation, maximum $I_{\rm c}$ can be achieved around 60$^\circ$ from the normal direction. However, the transport properties at low temperatures are not easily available due to the large current requirements. In this work, the field and angle dependence of the transport $I_{\rm c}$ at 4.2 K and magnetic fields up to 29 T is measured for the first time.
A 4 mm-wide THEVA Pro-Line HTS tape and pinning-improved tapes are characterized. The standard tape has a self-field $I_{\rm c}$ of 240 A at 77 K, and a similar value is obtained at 4.2 K and 15 T for $B\parallel c$. For $B\perp$tape, $I_{\rm c}$ is 180 A at 29 T and about 460 A at 5 T. These are already competitive results when compared to the present high values at 4.2 K of 4-mm wide tapes. The parameter $\alpha$ based on the field dependence of $I_{\rm c}$ given by $I_{\rm c}(B)\propto B^{-\alpha}$, is around 0.5 within the angular range of -45$^\circ$ to 50$^\circ$ and decreases to 0.3 for $B\parallel ab$. The pinning force per unit length, $F_{\rm p}$ continuously increases up to 29 T, and no maximum was observed for all angles. With the good in-field properties obtained in the standard THEVA tape, further investigations on tapes with additional pinning centers are conducted to explore how $I_{\rm c}$ would further improve at very high fields.

We acknowledge the support of LNCMI-CNRS, member of the European Magnetic Field Laboratory (EMFL).

Speaker: Mayraluna Lao (Karlsruhe Institute of Technology)

334 Tue-Mo-Po2.10-08 [80]: Improved performance at low temperatures of CSD-grown YxGd1-xBa2Cu3O7-BaHfO3 nanocomposite films

High-temperature superconductors are becoming engineering materials, e.g. as commercially available long-length tapes (coated conductors, CCs). Among them, REBa2Cu3O7-x (REBCO, RE rare earth) compounds have emerged as excellent candidates due to their high-field current carrying capacity. Their properties enhance even further when REBCO nanocomposites are formed, i.e., nanoscale non-superconducting secondary phases are introduced into the superconducting matrix, which pin the vortices. Through this, the performances improve in a wide range of applied magnetic fields and temperatures.
Chemical solution deposition (CSD) has been demonstrated to be a scalable, versatile and cost-effective technique for the preparation of REBCO films with embedded secondary phases, starting from a complex metalorganic precursor solution. In such films, the nanoparticles form spontaneously during the film growth and tend to orient randomly in the REBCO matrix. This creates a high density of defects generating nanostrain within the REBCO matrix, which ultimately leads to a strong enhancement of the isotropic pinning contribution.
In this work, we present the superconducting properties of 220 nm single-RE-Ba2Cu3O7-x (RE = Yb, Er, Ho, Y, Dy, Gd, Sm, and Nd) films on different substrates to develop a deeper understanding of their processing windows and properties at different temperatures. Also, we include a complete study about (Y/Gd)BCO + 12 mol% BaHfO3 nanocomposite films. These films were obtained in a high-quality after a complex growth-parameter optimization for different Y/Gd ratios. Transport measurements of the optimized films were carried out at different temperatures. The results show that the best properties are obtained for different Y/Gd ratios depending on the temperature: at 77 K, where the proximity to the superconducting transition is crucial, GdBCO+12mol% BaHfO3 has the largest critical current density Jc while at 30 K the Y0.5Gd0.5BCO+12 mol% BaHfO3 films exhibit the highest values at self-field. This behavior was understood by studying the microstructure of these samples by advanced TEM measurements. The distribution of Y and Gd in the mixed phases enrichens the pinning landscape making these films more effective at lower temperatures.

Speaker: Pablo Cayado (Karlsruhe Institute of Technology (KIT))

Poster MT26_Pablo Cayado.pdf

335 Tue-Mo-Po2.10-09 [81]: The study of quench behavior of REBCO cables under different twist pitch and perpendicular magnetic field

Due to high flexibilities and high critical current densities, the conductor on round core cable wound with REBCO coated conductors are currently being developed for the next generation of high field magnets. One of the primary challenges in the development of REBCO cable is quench protection, as the cable is prone to be burned out once the quench initiates. However, quench study of REBCO cables under different twist pitch and perpendicular magnetic field has been rarely reported. In this work, a heater is placed in the central zone on the surface of the cable, which allows pulses of various powers and durations to be generated. Combined with temperature and voltage detection, the influence of twist pitch and the number of tape layers on critical current and quench propagation will be measured at 77K in a liquid nitrogen bath. The results will provide important reference for the design of REBCO cable.

Speaker: Dr Zhang Haiyang

336 Tue-Mo-Po2.10-10 [82]: Electromechanical Performance of Practical REBCO CC tapes for Superconducting Wind Power Applications

A project to develop a Korean-type large scale floating off shore wind power system with a superconducting wind power generator has started. It is an innovative wind power project on the development of high-temperature superconducting (HTS) magnet, test facility, offshore floating system, and network connection technologies for the design of 10 MW class floating offshore wind power system with superconducting generator fully supported by KEPCO (Korea Electric Power Corporation). To make large-scale application of REBCO coated conductor CC tapes possible especially in superconducting wind turbine generator, it is required to pursuit a high generation efficiency, low weight design utilizing a higher performance of REBCO CC tapes at cryogenic temperatures and under magnetic fields. For the performance evaluation of the CC tapes, it is important to investigate the stress and strain dependency of Ic in both reversible and irreversible degradation region under external magnetic field. Generally, under magnetic field, the Ic degradation behavior may be different from the results obtained at self-field and dependent on the fabrication processes and materials of adopted practical CC tapes. In this study, the electromechanical properties including Ic degradation behavior and the irreversible limits of commercially available REBCO CC tapes were examined by the uniaxial tension tests at the expected operating condition of 77 K, 0.5 T and 30 K, 2 T. The obtained irreversible limits were compared to the ones at 77 K and self-field. Three kinds of CC samples were adopted, namely; the RCE-DR Sn-Cu stabilized, IBAD-PLD (ISD) Cu stabilized, and IBAD-PLD Cu stabilized CC tapes.

This research was supported by the Korea Electric Power Corporation. (Grant number: R18XA03). This work was partially supported by a grant from National Research Foundation of Korea (NRF-2017-001901) funded by the Ministry of Science, ICT and Future Planning (MSIP), Republic of Korea.

Speaker: Hyung-Seop Shin (Andong National University)

Tue-Mo-Po2.10-10 EMP of practical CC for Wind power.pdf

Tue-Mo-Po2.11 - Motors V

Conveners: Dr Alessandro Anemona (ENEA), Vitaly Vysotsky (Russian Scientific R&D Cable Institute)

337 Tue-Mo-Po2.11-01 [88]: Design and Analysis of an HTS Synchronous Motor with a Hybrid Magnets Rotor

High-temperature superconducting (HTS) materials, including bulks and tape stacks, have shown high current-carrying and field-trapping capacity in previous studies, which makes them employed in the synchronous motors (SMs) as a substitute of permanent magnets (PMs). When used as rotor magnets, hybrid magnets (HMs) made of HTS tape stacks and PMs show remarkable advantages compared with bulks and pure tape stacks, such as magnetization convenience, low cost, and operation safety. In this work, an HTS synchronous motor with a hybrid magnets rotor is proposed. A full-scale sample of hybrid magnets rotor is fabricated first and tested at 77 K. According to the experimental results, a prototype of the hybrid magnet synchronous motor (HMSM) is designed and the performances of the motor is obtained using finite element method (FEM) and analytical calculation. The results show that the introduction of hybrid magnets could significantly enhance the power and torque density with a minimal consumption of HTS tapes at 30 K. Due to the aforementioned advantages of hybrid magnets, HMSM is superior in practicability, economy and safety compared with the existing HTS motors, especially used as propulsion systems on ships and aircrafts.

Speaker: Dr Zhen Huang (Shanghai Jiao Tong University)

338 Tue-Mo-Po2.11-02 [89]: Evaluation of Mechanical Properties of an On-board 2G HTS Magnet System for Maglev Applications

Superconducting magnetic levitation (maglev) is developing rapidly in recent decades for its incomparable features like ultrahigh cruising speed. To develop the second generation high tempera-ture superconducting (2G HTS) maglev, a serious of work has been done by us including design of propulsive system, optimiza-tion of 2G HTS magnet system, energizing tests and over-current duration tests. In this work, as a continuation of the development progress, mechanical properties of the on-board 2G HTS magnet system that used in the maglev are evaluated, including modal analysis, harmonic response, random vibration, and shock response. Meanwhile, bench tests under much severer mechanical conditions are conducted, resulting no damages of the magnet. This work is intended to not only evaluate the mechanical properties of the magnet system, but also provide possible references and methods for similar mechanical assessment of other superconducting apparatuses.

Speaker: Fangliang Dong (Shanghai Jiao Tong University)

poster Tue-Mo-Po2.11-02.pdf

poster Tue-Mo-Po2.11-02.ppt

339 Tue-Mo-Po2.11-03 [90]: Dynamic Characteristics Analysis Considering Instantaneous Inductance According to Mover Position of Flat-type Permanent Magnet Linear Oscillating Machines

Linear oscillating machines (LOMs) can control linear reciprocating motions through stroke cycles at specific frequencies. A single-phase, short stroke LOM has been developed for use in refrigeration compressors and other similar devices, because of their high transmission efficiency and simple structure. Generally, conventional LOMs are designed as cylindrical structures. However, such structures are difficult to manufacture because the stator core must be stacked in a radial direction. To overcome these disadvantages, a flat-type LOM has been proposed; they are easy to fabricate and their output power increases with the stacking length.

In this paper, an electromagnetic design and a dynamic characteristics analysis of the flat-type LOM are presented. First, the operation principle of the flat-type LOM is explained, and then, the optimum shape of a permanent magnet and stator is designed. The electro-magnetic characteristics, such as flux density, magnetic force, and back EMF, were verified through a no-load analysis. Meanwhile, the inductance and magnetic force change instantaneously depending on the position of the movable permanent magnet. For an accurate dynamic characteristics analysis of the LOM, instantaneous changes in force and inductance should be considered along with the mechanical components, such as spring, damping, and load force to analyze the characteristics of a linear operations. The characteristics of stroke and magnetic force according to the applied voltage and frequency are verified, and the efficiency of the flat LOM is confirmed in the operating range. Finally, the reliability of the analysis is verified through the manufacturing process and experiments.

More detailed discussions, analysis results, and experimental results will be presented in the final paper.

Speaker: Chang-Woo Kim (Chungnam National University)

MT_Poster_KCW-2.pdf

MT_Poster_KCW-2.pptx

340 Tue-Mo-Po2.11-04 [91]: Experimental Verification and Analytical Study of Influence of Rotor Eccentricity on Electromagnetic Characteristics of Permanent Magnet Motor

Permanent magnet synchronous machines (PMSM) are becoming an essential technology for applications such as home appliances, industrial tools, and electrical vehicles. Todays, consumer demands for noise and vibration of products are increasing, and studies on the noise and vibration characteristics of motors that generate power are actively being conducted. One of the factors contributing to noise and vibration is rotor eccentricity that could be shown in the manufacturing process of the motor. Rotor eccentricity indicates that the center of the rotor axis deviates from the center of the stator, meaning the air-gap is not uniform. The rotor eccentricity interrupts the uniform distribution of magnetic flux to the stator, resulting in an increased cogging torque and unbalanced magnetic force. Since the cogging torque and the unbalanced magnetic force are generated by the use of permanent magnets, the impact on the magnetic field distribution due to permanent magnets should be analyzed with a model in which eccentricity is applied.
In this study, we present an analytical model for the permanent magnet machines in which rotor eccentricity is applied. We simplified the analytical model through several assumptions and modeled the magnet according to the selected magnetization direction. Based on electromagnetic field theory and the perturbation theory, the governing equations were derived in the air-gap region. Further, the relationship between the magnetic scalar potential in each region and the appropriate boundary conditions is used to obtain the undetermined coefficients to derive the magnetic flux density characteristics in each region. The validity of the analytical results was verified by comparing them to the results of the two- dimensional finite element analysis and experiments. More detailed results, discussions, and desired effects will presented in the full paper.

Speaker: Hoon Ki Lee (ChungNam National Unversity)

MT_Poster_LHK_ver2.pdf

341 Tue-Mo-Po2.11-06 [92]: Research on a High Torque Density Outer Rotor Flux-Modulated Machine with Sandwiched-Permanent-Magnet Topology

In recent years, flux-modulated principle is investigated extensively in diverse permanent magnet (PM) motors due to the prominent advantages of low-speed and large torque capability. And then, a new electrical machine family, nominated as flux-modulated PM (FMPM) motor, is formed gradually. Interestingly, the FMPM motors break through the traditional motor design rule that the pole-pairs of the stator winding and rotor are required to be the same, thus they provide new opportunities and challenges for realizing the high-performance drive motors. In current studies, the PM source designs have been regarded as the main research subject for the FMPM motors, which determine the motor performances greatly. It is worth noting that, according to the flux-modulated principle, the variation of the PM sources will result in changes on the airgap harmonics and further influence on motor performances. It means that the airgap field harmonics are actually essential bridges or deliverers in motor energy conversion, which is vital during the design analysis of the FMPM motors. Hence, it can be inferred that the establishment of relationship among the airgap harmonics, PM sources and motor performance objectives are indispensable to achieve high performances of the FMPM motors. In this paper, a sandwiched-permanent-magnet flux-modulated (SPMFM) motor with two magnet topologies are proposed, where the unique PM designs is beneficial to bring about an enhanced flux-modulated effect. So it can be indicated that the SPMFM motor possesses the potential performance features of high torque density and high PMs utilization. For achieving the optimal motor performances, the parameter design is conducted purposely by considering the leading airgap harmonics. And the key motor performances are evaluated, consisting of harmonic characteristics, back-EMF, output torque, and so on. For further verification, a prototype is manufactured and tested. Finally, the simulation analysis and experimental results validates the proposed SPMFM motor.

Speaker: Dr Zixuan Xiang (School of Electrical and Information Engineering, Jiangsu University, Zhenjiang, China)

342 Tue-Mo-Po2.11-07 [93]: Comparative research for a novel dual stator synchronous machine with permanent magnet-reluctance composite rotor

This paper presents the research work for a novel dual-stator composite-rotor synchronous machine (DSCRSM). Ferrite permanent magnets (PMs) are used for the composite rotor with flux barriers, while the axis of each PM pole is located as 45 degree (electrical) with respect of the axis of the corresponding flux barrier. Compared with the conventional permanent magnet-assisted synchronous reluctance machine (PMASynRM), the proposed DSCRSM is capable to provide a higher output torque when the same amount of ferrite magnets consumed. The electromagnetic torque of the DSCRSM is consisted of two components, namely, magnetic and reluctance torques. The superiority of the DSCRSM is obtained by the utilization of a composite rotor that is capable of full use of torque components, as both magnetic and reluctance torques can reach their maximum values near or at the same current phase angle. To evaluate the contribution, Finite element method (FEM) is utilized in this study to investigate the torque and torque components for both PMASynRM and DSCRSM, while the two machines consume the same amount of ferrite magnets. Compared with the referenced PMASynRM, the maximum output torque of the proposed DSCRSM is increased by 19.6%. Moreover, torque ripple of the developed DSCRSM is also obviously reduced. Therefore, the proposed DSCRSM exhibits higher average output torque with lower torque ripple when compared with the conventional PMASynRM consuming the same amount of ferrite magnets. Machine performances, including electromotive forces (EMFs), power losses and efficiencies of both machines are also further researched and compared in this study. Eight composite rotor topologies with different flux barrier configurations are analyzed and compared, and the desirable rotor design is obtained with the least torque ripple for DSCRSM.

Speaker: Fengge Zhang (Shenyang University of Technology)

Tue-Mo-Po2.11-07.pdf

343 Tue-Mo-Po2.11-08 [94]: Experiments and Comparative Study of Rotor Vibration of Permanent Magnet Machines with Two Different Fractional pole/slot combinations

Recently, permanent magnet synchronous motors (PMSMs) have been widely used in the industry owing to their various advantages, such as high-speed operation, high efficiency, and compact design. However, PMSMs have the drawback of noise and vibration, which is caused by local force generated by the interaction between the stator and rotor magnets having high magnetic energy, significantly affecting the machine performance. Moreover, these vibrations and noises cause problems, such as eccentricity, bearing failures, and misalignment of the PMSM. Therefore, it is important to identify which electromagnetic sources actually affect vibration and noise.
Electromagnetic vibration sources can be divided into two types: electromagnetic force and torque pulsations. Previous studies have shown that vibration characteristics are improved by a decrease in each of the electromagnetic vibration sources, and it is related to the noise on PMSM through a interaction. However, it does not clarify the influence of each source.
Thus, to analyze the influence of each source, in this study, we derived the dominant model of the pole/slot combination for each electromagnetic vibration source. The analysis and prototype model used FEM tools for the electromagnetic excitation analysis. The derived pole-slot combination is the 8-pole/9-slot and 8-pole/12-slot. The characteristic analysis results of the electromagnetic excitation are as follows. The torque pulsation, as torque ripple and cogging torque, is lower in the 9-slot model than in the 12-slot model. However, the unbalanced magnetic force in the 9-slot model is higher than that in the 12-slot model. In the 9-slot model, not only is the distribution of force density uneven, but also the magnitude of the unbalanced magnetic force is large. Thus, we analyzed the influence of each vibtation source through experiments and electromagentic-mechanical analysis by comparing the analysis results of two different fractional pole/slot combinations.
The electroamgnetic and mechanical analysis results, and experimenal set, measurements of the PMSM will be presented in more detail in the full paper.

Speaker: Tae-Kyoung Bang (Republic of Korea /Chungnam National University)

MT_Poster_TK_Ver1.pdf

344 Tue-Mo-Po2.11-09 [95]: Unbalanced magnetic force and vibration analysis of dual mechanical port flux switching PM machine considering rotor eccentricity

Dual mechanical port flux-switching permanent magnet (DMP-FSPM) machine with high power density, high torque density, and wide operation range has potential application prospect in electric vehicles (EVs). The DMP-FSPM machine is consist of inner rotor, outer rotor and middle stator which can be regarded as the combination of two conventional flux-switching permanent magnet (FSPM) machines. The stator is sandwiched by the two rotors, in which the PMs and two sets of armature windings are mounted. The flux barrier is located on the middle stator yoke. Due to the topology of the dual mechanical port, the rotor eccentricity, which causes asymmetrical air-gap filed and unbalanced magnetic force, often occurs in the complex multimode operation conditions. In this paper, the electromagnetic and vibration characteristics of the DMP-FSPM machine is investigated in the multimode operation conditions. The main works are listed as follows.
Firstly, the topology of the DMP-FSPM machine is introduced, and the initial design of the DMP-FSPM machine is given. Secondly, in the rotor eccentricity conditions, the influences of the parameters, such as stator teeth width, arc of the PMs, etc., on the radial and tangential magnetic force are studied by the finite element method (FEA). The unbalanced magnetic force of the two air gaps are also analyzed in the different operating modes, and the harmonic components of the radial and tangential unbalanced magnetic force are compared. Then, based on magnetic-solid coupling analysis method (MCAM), the electromagnetic vibration is discussed. The relations between the vibration which causes by the rotor eccentricity and torque performances of the DMP-FSPM will be given. Finally, in order to reduce the effects of vibration, the optimization design will be done by the sensitivities analysis method. The results will be compared with that of the initial design, and it will also verify the correctness of theoretical analysis.

Speaker: Mr Yifeng Hua (Jiangsu univeristy school of electrical and information engineering)

345 Tue-Mo-Po2.11-10 [96]: Cogging Force Reduction of Tubular Flux Switching Permanent Magnet Motor by Using Unsymmetrical Design Method

Tubular flux-switching permanent magnet motor (TFSPMM) is a special kind of permanent magnet machine with the permanent magnet (PM) installed on the stator side and there is no winding or PMs on the mover side. Among various kind of linear machines, TFSPMM draws a great interest from researchers for its robust structure, high drive force density and low material cost required. Compared with the other linear machines, TFSPMM’ tubular structure avoids the motor thrust fluctuation caused by transverse side effect. However, the TFSPMM is opened at two ends, which will destroy the integrity of the magnetic circuit. The end effect can bring the TFSPMM with higher cogging force, higher force ripple and un-symmetry of the PM flux linkage especially when phase A and phase B has the end winding, and the problems will bring difficulties to the stable output and control of the motor. Based on these situations, this paper proposes a new unequal stator teeth method for the reduction of end effect. On the premise of not changing the volume of the motor, the end effect of the motor can be weakened by coordinating the axial length of the stator yoke and the axial length of the adjacent permanent magnets, so as to improve the symmetry of the three-phase permanent magnet flux linkage and reduce the cogging force. The calculation results are mainly based on the analysis of the average value and peak-to-peak value of the A-phase permanent magnetic flux linkage, because the A-phase and B-phase windings are symmetric in position and contain the end windings. To reduce the calculation load, the main electromagnetic parameters and performance of TFPMM are obtained based on using the 2D finite element method (FEM), and the model is built around the Z-axis, and the software defaults to rotate 360 degrees around the Z-axis.

Speaker: Dr Chengcheng Liu (Hebei University of Technology)

mt poster.pdf

mt poster.ppt

346 Tue-Mo-Po2.11-11 [97]: Investigation of High Temperature Superconducting Flux-Switching Motors with Different Secondary Structures

Compared with Linear Induction Motor (LIM) which is widely applied in urban railway transit system, Linear Flux-Switching Motor (LFSM) has the merits of high power density, high efficiency, while the secondary of LFSM is robust and simple. Hence, LFSM is claimed to be promising for urban railway transit system.
Generally, LFSPM can be classified as Linear Wound Field Flux-Switching (LWFFS) motor and Linear Flux-Switching Permanent Magnet (LFSPM) motor. Researches show that LFSPM motor has high efficiency and power factor while the speed range and reliability is limited due to the Permanent Magnets (PM). For LWFFS motor, the speed range is wide while the power density and efficiency are influenced by the field windings.
To cooperate the merits of high power density and wide speed range, it is feasible to adopt High Temperature Superconductor (HTS) windings as field windings. But so far, the researches of HTS LFSM are limited to the design, optimization and analysis of one certain kind of HTS LFSM. It remains unknown whether the conclusions about typical LWFFS motor also apply to the HTS LFSM whose current density is extremely high. And it also lacks investigation about the strength and weakness of different topologies of HTS LFSMs. Therefore, the aim of this paper is to investigate the performance of HTS LFSPMs of different secondary structure and pole pitch ratio between primary and secondary.
In this paper, the topologies and working principles of HTS LFSMs with slotted secondary and segmented secondary will be introduced first. Second, slotted HTS LFSMs of different primary and secondary pole pitch ratios will be optimized and compared with other to obtain a finest slotted HTS LFSM. Third, segmented HTS LFSMs of different primary and secondary ratios also be optimized and compared with other so that a finest segmented HTS LFSM can be obtained. In the end, the HTS LFSMs of different secondary structures will be compared under different working conditions to investigate their performance for railway transit system.

Speakers: Ruiwu Cao, Mr Lu Minghang (Nanjing University of Aeronautics and Astronautics)

Investigation of High Temperature Superconducting Flux-Switching Motors with Different Secondary Structures.pdf

Investigation of High Temperature Superconducting Flux-Switching Motors with Different Secondary Structures.pptx

347 Tue-Mo-Po2.11-12 [98]: A Study on the Shape Design of a Magnetic-Geared Synchronous Motor for Improvement of Performance and Securing Rigidity

This paper describes a study on the shape design of Magnetic-geared synchronous Motor for improvement of performance and securing rigidity. The Magnetic-Geared synchronous Motor(MGM) is an all-in-one structure of a magnetic gear and a permanent magnet synchronous motor, and is an electric machinery capable of operating both functions. In this study, the existing surface-mounted type is set as the model of the basic design and the performance is improved through the design of changes in the permanent magnet shape of the rotor. Mechanical reduction devices have high mechanical noise and vibration and require replacement due to wear of the gear teeth, resulting in increased maintenance costs. In addition, when the induction motor is applied, the power transmission efficiency drops to 90% or less, so the efficiency tends to be low. In this paper, the basic design of the 1kW magnetic-geared synchronous motor (MGM) was performed in SPM type. However, SPM type with many domestic and foreign research examples has limited performance due to large magnetic gap and disadvantage of structural rigidity at high speed. Thus, in this study, the existing SPM type was set as the model of the basic design and the performance improvement and rigidity were secured through the design of changes shape of the rotor. This method of study was conducted based on the FEM of electromagnetic field. This paper describes a study on the shape design of the MGM for improvement of performance and securing rigidity. In order to improve the performance, the shape of the rotor was changed to reduce the amount of permanent magnet and the torque ripple rate. In addition, we propose and design a favorable shape for high speed and secured rigidity through FEM analysis. MGM has studied SPM type, but MGM proposes IPM type because IPM type is excellent in performance and rigidity.

Speakers: Hyungkwan Jang (Hanyang University), Hyunwoo Kim

Tue_Mo_Po_12_03.pdf

Tue-Mo-Po2.12 - Motors VI

Conveners: Dr Alessandro Anemona (ENEA), Vitaly Vysotsky (Russian Scientific R&D Cable Institute)

348 Tue-Mo-Po2.12-01 [99]: Efficiency Improvement of Permanent Magnet BLDC with Halbach Magnet Array for Drone

1) Introduction
Currently, drones are used in various fields such as logistics, transportation and filming in the military field. However, there is a disadvantage that it is difficult to operate for a long time due to the battery limit of the drone. In order to overcome these disadvantages, studies have been conducted to improve the efficiency of the motor and to increase the power per weight.
2) Body
In this paper, a study was carried out to improve the efficiency of permanent magnet brushless DC motor (BLDC) of drone. In order to improve the efficiency of the motor, there are methods such as changing the load ratio of the motor or changing the grade of the permanent magnet material. Among them, when the halbach magnet array is applied, the leakage flux toward the outside of the rotor is decreased, and the use of core on the outside the rotor can be reduced. In addition, since the field magnetic flux increases, the influence on the armature reaction can be reduced, and the coreloss of the motor can be decreased to improve the efficiency. Also, when the pole / slot combination of the motor is changed, the magnetomotive force (MMF) distribution varies depending on the winding factor. Therefore, efficiency can be improved by selecting pole / slot combinations with maximum MMF distribution. Therefore, in this paper, the distribution of the MMF according to the winding factor in BLDC motor has been analyzed. Also, the model with a halbach magnet array in existing BLDC motors was confirmed to have an effect of improving efficiency by using finite element analysis (FEA) and the electromagnetic characteristics of the motor were analyzed by adjusting the ratio of halbach magnet.

Speakers: Seungheon Lee (Hanyang University), Hyunwoo Kim (Hanyang University)

Tue_Af_Po_21_01.pdf

349 Tue-Mo-Po2.12-02 [100]: Optimization Design of Permanent Magnet Assisted Single Winding Bearingless Synchronous Reluctance Motor

In the past two decades, a bearingless synchronous reluctance motor (BSynRM) was proposed and developed. Besides the advantages of the traditional bearingless motor, the BSynRM has the advantages of simple structure, low cost, low losses and can realize high speed operation using weak magnetic speed regulation. A permanent magnet assisted bearingless synchronous reluctance motor (PMa-BSynRM), which adopts a multi-layer flux barriers rotor with permanent magnets installed in, has advantages in torque density and power factor. Therefore, the PMa-BSynRM has broad application prospects in vacuum, high speed, high precision and many other industrial fields. However, as a result of the traditional PMa-BSynRM having torque windings and suspension force windings, the volume of the motor and the power loss and processing cost of the stator are increased, and the vibration of the traditional PMa-BSynRM is severe, which limit its scope of application in some degree.
To balance the contradictions mentioned above, a novel permanent magnet assisted single winding bearingless synchronous reluctance motor (PMa-SWBSynRM) with the skewed stator and rotor is proposed in this paper. Firstly, the basic structure and operation principle of the proposed motor is described detailedly. Secondly, the mathematic model of the radial suspension forces is derived with Maxwell stress tensor method. Then, the electromagnetic characteristics the motor is analyzed in detail through finite-element analysis (FEA). Following the electromagnetic analysis, the vibration of the PMa-SWBSynRM is discussed based on the model analysis and harmonics of the radial force. Finally, the experimental prototype platform was built and the FEA results were verified by the experimental measurement.

Speakers: Ying Xu (Jiangsu University), Mengyao Wu (Jiangsu University)

Ji Zongyou-Poster.pdf

Ji Zongyou-Poster.pptx

350 Tue-Mo-Po2.12-03 [101]: Design and Analysis of a BLDC Motor with Halbach array magnets

1. Introduction
   The BLDC motors(Brushless DC Motors) have been used for different kinds of industries due to the high power density, low maintenance and simple design. BLDC motors are used in variety of applications such as home appliances, electric vehicles and aerospace applications. Recently, aerospace applications like drones raise a demand for a permanent magnet BLDC motor with high efficiency and more flight time. In order to make longer flight under the same battery, outer rotor BLDC motor which is being used in commercially available drones should have structure for improvement of power density.

2. Body
   This paper presented design of outer rotor BLDC motor with halbach array magnets. Since halbach array magnets maximize the flux density in one direction, the proposed topology has structure that concentrates permanent magnet flux. Structural studies on halbach array magnets were carried out in consideration of permanent magnet shape, pole ratio and stator shape. In addition, according to the direction of magnetization and magnet arrangement, output characteristics were analyzed. Target motor which is for commercial use was selected to verify the superiority of the BLDC motor presented in this paper. The test was done to measure power density, efficiency and current density of the target motor. The design result was simulated with Finite Element Analysis(FEA) design-based software. Also, through comparison of output characteristics between the target motor and the design result, the superiority of the BLDC motor presented in this paper was verified.

Speaker: Seungheon Lee

351 Tue-Mo-Po2.12-04 [102]: Analysis and Design of a New Type of Less-rare-earth Hybrid-magnet Motor with Different Rotor Topologies

Permanent magnet (PM) machines have been a research hotspot for EV propulsion due to their merits of high power density and high reliability [1]. Recently, considering the high price and unstable supply of rare-earth PM material, the non-rare-earth PM (NRE-PM) motor has drawn increasing attention. However, the relatively low magnetic energy product of non-rare-earth PM makes it difficult to ensure the high torque output. And the large volume of PM material is generally required in the NRE-PM motor, which reduces the mechanical strength of the rotor. To realize high torque density, in this paper, a new type of less-rare-earth hybrid-magnet (LRE-HM) motor is proposed, where two types of excitation sources of non-rare-earth ferrite-PM and rare-earth NdFeB-PM are integrated into the rotor.
In the proposed LRE-HM motor, the placement of two types of PM materials is very flexible, so it can be formed in series or parallel magnetic circuit, or even mixed one. According to the further desired objectives of improved flux-weakening ability and enhanced capability of anti-demagnetization, the LRE-HM motor with different rotor topologies are designed artfully. In this LRE-HM motor, through the interaction of two kinds of PM materials, the higher operating points of hybrid PMs can be also obtained.
Compared with the NRE-PM motor, the motor performance of the proposed machine such as torque density, speed range and demagnetization withstand capability have been significantly improved. In addition, the LRE-HM motor with parallel magnetic circuit has the smaller magnetic leakage and the higher utilization rate of PM torque than those with series magnetic circuit. With the properly designed barrier, a larger d-axis inductance can be obtained and the total torque output can be further improved combining with the reluctance torque.
In order to verify the feasibility of the LRE-HM motor topology and the desirable electromagnetic performance, the experimental prototype are fabricated, and more theoretical analysis and experimental verification will be provided in the full text.

Speaker: Mrs Yunyun Chen (School of Hydraulic, Energy and Power Engineer, Yangzhou University)

MT poster-cyy .ppt

352 Tue-Mo-Po2.12-05 [103]: Design and Electromagnetic analysis of 2 MW Fully-Superconducting Synchronous Motors Composed of REBa2Cu3Oy coated conductors for Turboelectric Propulsion System

High power motors and generators with compactness and lightweight are required for turboelectric propulsion system for future electric aircrafts. Fully superconducting rotating machines have the potential to realize high power density. In this study, we aim to design high-power-density synchronous motors composed of superconducting field windings and superconducting armature windings, especially power density over 20 kW/kg. Note that, the voltage of the armature windings should be a few kV or less due to a low withstand voltage at a height of over 8000 m in the sky. The introduction of transposed parallel conductors can realize a large current capacity in the armature windings, which also lead to low voltage. Firstly MW-class fully superconducting motors were designed as follows. The superconducting wires were BaHfO3-doped EuBa2Cu3Oy coated conductors fabricated by IBAD-PLD technique. The operating temperatures were assumed as 20 or 65 K. The magnetic flux density at the air gap was assumed 1, 1.5 and 2 T. The motor properties were investigated by making a numerical simulation with JMAG. AC losses were actually observed by a pickup coil method and partially estimated by using theoretical expressions such as a temperature scaling law. For a total model of 6 patterns, the influences of the operating temperature and the magnetic flux density at the gap on the power density and the AC losses of the field and armature windings were investigated and compared. As a result, it was shown that the power density attained to 21.2 kW/kg in the case of the operating temperature of 20 K and gap flux density of 1.5 T for the 5 MW-class superconducting motor.

Acknowledgement

This research was partially supported by the New Energy and Industrial Technology Development Organization (NEDO), the Japan Science and Technology Agency (JST): Advanced Low Carbon Technology Research and Development Program (ALCA) and the Japan Society for the Promotion of Science (JSPS): Grant-in-Aid-for Scientific Research (JP18H03783 and JP17H06931).

Speaker: Mr Ryota Sugouchi (Kyushu University)

353 Tue-Mo-Po2.12-06 [104]: Conceptual design and electromagnetic analysis of superconducting induction motors using REBa2Cu3Oy tapes

High power density motors are required for electric propulsion systems of future electric aircrafts, flying cars and electric vehicles. The highest power density of the conventional motor for aircrafts is reported as 5.5 kW / kg. Superconducting rotating machines have a potential to realize higher power density due to its high current density and low loss property. In this study induction motors which has air-cored superconducting armature windings are developed. The first target in the power density of the superconducting motor is 20 kW / kg. The superconducting tapes for the armature windings were BaHfO3-doped EuBa2Cu3Oy ones fabricated by IBAD-PLD technique. The AC losses of the tapes were actually observed by a pickup-coil method and partially estimated by using theoretical expressions such as a temperature scaling law. For the reduction of the AC loss in armature windings, a laser-scribing technique and transposed parallel conductors which were developed in our previous studies were applied. The electromagnetic design and analysis were carried out by using JMAG Designer. The output power, number of magnetic pole and operating temperatures were set as 100 kW, four poles and liquid nitrogen temperature of 65-77 K, respectively. The dependences of the power density and efficiency on the size (diameter and effective length), frequency and number of turns of armature windings were investigated. The detailed analysis results will be reported in this conference.
This research was partially supported by the New Energy and Industrial Technology Development Organization (NEDO), the Japan Science and Technology Agency (JST): Advanced Low Carbon Technology Research and Development Program (JPMJAL1405) and the Japan Society for the Promotion of Science (JSPS): Grant-in-Aid-for Scientific Research (JP18H03783 and JP17H06931).

Speaker: Mr Koichiro Ozaki (Kyushu University)

354 Tue-Mo-Po2.12-07 [105]: Optimized Design of Permanent Magnet Considering Thermal Demagnetization Analysis of Synchronous Motor

EV & HEV are being studied to increase fuel economy and driving efficiency in a variety of ways. Especially, mechanical compressor is critical reason of reducing fuel efficiency. The brushless direct current motor (BLDC) is considered as the most suitable model to satisfy the characteristics of electric compressors. Segmented permanent magnet was used to improve the efficiency of the electric-driven compressor of electric vehicles motor. It is one of the methods for reducing the eddy current loss. In this paper analysis precision analysis design according to winding pattern. Therefore, this paper proposes optimal structure that minimizes eddy current loss and irreversible demagnetization characteristics of permanent magnet. Recently, permanent magnet type motors have been mainly studied for output increase motor for electric compressors. The irreversible demagnetization characteristics of magnets, which is one of the factors that determine the performance of a motor, should be carefully analyzed and designed. The occurrence of irreversible demagnetization in a permanent magnet can be largely divided into two types: an external demagnetization field and demagnetization phenomenon by temperature change. Therefore, an optimal design is analyzed the demagnetization reliability of permanent magnet based on these factors. The maximum efficiency was analyzed by consider the shapes of various magnets.And Rare earth magnets are used in motors that generate high efficiency and output characteristics. However, it is vulnerable to irreversible demagnetization at high temperatures. Therefore, we studied optimal design after analyzing the characteristics of demagnetization at external magnetic field and high temperature. The irreversible demagnetization characteristics of the permanent magnets were analyzed using a split magnet. The characteristics of output power according to concentration winding and distribution winding and irreversible demagnetization characteristics of permanent magnet was analyzed. Back_EMF was compared to analyze the permanent magnet demagnetization ratio. The ANSYS Electromagnetic Suite 19.0 was used to analyze irreversible demagnetization under driving conditions.

Speaker: Mr Jonghun Lee (KEIMYUNG UNIVERSITY)

MT26_1194.pdf

355 Tue-Mo-Po2.12-08 [106]: Design, Fabrication, and Testing of a YBCO Racetrack Coil for an HTS Synchronous Motor with Brushless Exciter

An experimental platform of high temperature superconducting (HTS) synchronous motor with brushless HTS flux pump exciter has been designed and built. The support structure of HTS field windings was designed with a cantilever beam and was manufactured. In this paper, an HTS racetrack coil wound with YBCO tapes was designed and fabricated to verify the reliability of the motor employing a brushless exciter. The brushless HTS exciter was designed to be used as DC power supply to inject large currents into the HTS field coils, which eliminates the slip ring in the motor and avoids thermal load from current leads. The coil was mounted to support structure enclosed in the thermal shield and tested to check performance at an operating temperature of about 30 K. The test results show that the racetrack coil has excepted thermal and electrical stabilities. Finally, the test at this stage verifies the feasibility and reliability of HTS synchronous motor with brushless HTS flux pump.

Speaker: Dr Wei Wang (Sichuan University)

356 Tue-Mo-Po2.12-09 [107]: Proposed Commutation Method for Performance Improvement of Brushless DC Motor

Generally, brushless DC (BLDC) motors use three low-cost Hall sensors to obtain information regarding the position of the rotor and operate using a 120° commutation method. Furthermore, BLDC motors require an ideal trapezoidal back-EMF waveform owing to an input current. However, it negatively affects the motor performance owing to the notch phenomenon of current. In addition, torque ripple, core loss, and permanent magnet loss may result from current harmonics. Therefore, to minimize this effect, it is important that the back-EMF waveform of BLDC motor must be designed ideally sinusoidal. In addition, it is essential to control commutation via the BLDC drive to obtain a phase voltage that is ideally sinusoidal. Thus, the back-EMF and current waveforms must be sinusoidal, similar to those of a brushless AC (BLAC) motor, thereby increasing the efficiency.
This study focused on efficiency improvement of BLDC motors via reduction of torque ripple, core loss, and permanent magnet loss. To achieve this objective, we proposed an improved 150° commutation method for three-phase permanent magnet BLDC motors to improve the current waveform. Although the 120° commutation method is generally employed for a BLDC motor, the improved 150° commutation method is introduced in order to operate the BLDC with the same efficiency as a BLAC motor. Moreover, the improved 150° commutation is proposed to reduce the phase current harmonics. The study investigates the attributes of different commutation methods analytically and experimentally in order to determine the optimal commutation method. The result of this study indicates that the improved 150° commutation method is optimum in terms of harmonic attributes, and reduced torque ripple, thereby improving the motor’s efficiency.

Speakers: Prof. Chang-Sung Jin (Wonkwang University), Hyungkwan Jang (Hanyang University)

Tue-Mo-Po2.12 Presentation.pdf

357 Tue-Mo-Po2.12-10 [108]: A new linear permanent magnet switched reluctance motor with segmented primary for urban rail transit

Linear switched reluctant motors(LSRMs) have received more attention in variable speed drive applications such as urban railway transportation due to their simple structure and minimum use of power switching devices. However, the thrust/power capabilities is not high enough in certain circumstances. To incorporate the merits of simple and robust structure of LSRM and high thrust force density and efficiency of permanent magnet motor, a new linear permanent magnet switched reluctance motor (LPMSRM) with segmented primary is proposed in this paper. The primary of the segmented LPMSRM consists of six individual U-shaped segments; each one has two teeth associated with a PM installed between them. The secondary is simply composed of iron in the core. When none of the coils is excited, the flux generated by the PM is only closed through the U-shaped segment and does not cross the secondary and the gap. So, the no-load cogging force of LPMSRMs is near to zero. The thrust ripple is lower than the conventional LSRMs to some extent. This paper comprehensively evaluates and compares a high-thrust segmented-stator LPMSRM drive with a conventional LSRM drive in terms of static magnetic and dynamic performances. The static magnetic characteristics of a segmented LPMSRM and a conventional LSRM, including flux distribution, phase flux linkage, electromagnetic thrust, are analyzed and compared. The comparative results show that the LPMSRM has better characteristics than the conventional LSRM, such as less iron consumption, higher static and dynamic average thrust production, lower thrust ripple, higher power and thrust densities, higher efficiency, and stronger starting capability.

Speakers: Ruiwu Cao, Mrs Shen Danni (Nanjing University of Aeronautics and Astronautics)

358 Tue-Mo-Po2.12-11 [109]: Analysis and Optimization of Less-rare-earth Hybrid Excitation Flux-switching Machine

Flux-switching permanent magnet (FSPM) machine is extensively investigated own to its advantages of robust motor structure, low torque ripple and high efficiency. Recently, considering the high price and unstable supply of rare-earth PM, less-rare-earth or none-rare-earth PM motors have drawn increasing attention. Due to the relatively low magnetic energy product of non-rare-earth PM, the larger volume of PM material is generally required to ensure the high torque output. However, the stator space is limited in the conventional FSPM machine, which restricts the amount of PMs and armature windings, and consequently limits the improvements of the electromagnetic performance and heat dissipation capacity.
In this paper, by integrating the special partitioned double-stator structure in the multi-excitation flux switching motor, a less-rare-earth hybrid excitation flux-switching machine (LREHE-FSM) is proposed for EV propulsion. The proposed DSHE-FSM inherits the advantage of high space utilization. The hybrid-PMs of rare-earth NdFeB and none-rare-earth ferrite are applied to reduce the consumption of rare-earth PM material while keep high torque density. The field windings around ferrite-PMs can be as supplementary electric excitation windings. Moreover, with AC and DC field windings equipped in the outer and inner stator separately, more flexible flux adjustment can be achieved and more wide effective speed range can be obtained. The demagnetizing withstand capability of ferrite-PMs can also be improved. According to the requirements at different EV driving cycles, the proposed LREHE-FSM needs to offer multiple driving modes. The electromagnetic performances including output torque, torque ripple, efficiency and flux regulation ratio are then selected as optimization targets for different driving modes. Then the proposed LREHE-FSM is optimized and compared with a conventional dual stator flux switching machine.
In order to verify the feasibility of the LREHE-FSM topology and the effectiveness of the proposed optimization, the experimental prototype is fabricated, and more theoretical analysis and experimental verification will be provided in the full text.

Speaker: Yunyun Chen (School of Hydraulic, Energy and Power Engineer, Yangzhou University)

359 Tue-Mo-Po2.12-12 [110]: Design and Investigation of a Dual-Stator Flux-Modulated Permanent Magnet Motor with High Demagnetization Withstand Capability

Recently, flux-modulated permanent magnet (FMPM) motors which based on flux-modulation principle have been extensively investigated, due to inherent high torque density at low speed. With the increasingly critical operating environments for traction machines, high-reliability operation of machines has gained much attention. Especially when traction machines operate under extreme conditions, like overload and deep flux-weakening, PMs often suffer from high irreversible demagnetization risk. Under such conditions, motor output torque capability would be reduced to some extent, which impacts the continuous high-reliability operation of motors. Yet, the current studies on FMPM motors are mainly biased on proposing novel motor topologies, and investigating the relationship among airgap harmonics and flux linkage, back-EMF, and output torque, the relationship between motor demagnetization capability is seldom involved. Hence, in order to fill the knowledge gap, the relationship between airgap harmonics and motor anti-demagnetization capability are investigated. Based on this, a dual-stator flux-modulated permanent magnet (DS-FMPM) motor with high demagnetization withstand capability is proposed and investigated.

In the investigated DS-FMPM motor, the spoke-type PMs are inserted in the middle rotor, while the middle rotor is sandwiched between the inner and outer stators. Firstly, the relationship between motor airgap harmonics and PM operation points is investigated in detail. Then, based on this, in order to improve motor anti-demagnetization capability, some key design parameters, like PM topology, are purposely designed and optimized. It is noted that, compared with the initial motor, the average PM operating points is improved from 0.18T to 0.25T, and the PM demagnetized area is about 1/3 of that of the initial motor, while the torque output capability of the investigated motor is almost the same. Hence, it not only proves the high-demagnetization capability of the investigated DS-FMPM motor, but also verifies the relationship between air-gap harmonics and motor demagnetization characteristics, which lays solid foundation for the design of high-reliability flux-modulated permanent magnet motors.

Speaker: Deyang Fan (Jiangsu University)

Tue-Mo-Po2.13 - Low Tc Wires and Cables

Conveners: Emanuela Barzi (Fermilab), Peter Lee (Florida State University)

360 Tue-Mo-Po2.13-04 [111]: FEM modeling of stability and current sharing in Nb3Sn Rutherford cables

Finite Element Method (FEM) modeling of stability and current sharing in Nb3Sn Rutherford cables was performed. The modeled cables had 32 strands and they were three twist pitches long. Different values of contact resistances Ra and Rc were selected based on previous values extracted from ac loss measurements, as well as a set of design values. Current sharing was then projected for these cases. FEM models which mimic the QXF1055z-D cable (here named Q6 cable) and the HQ1020ZB (here named H1 cable) were set up. A defect in the central strand, 1 mm long, was created. It was assumed that this defect can carry 50 % of the strand’s critical current. At the cable current of 0.85 Ic the current sharing effect was modeled for real values of Ra and Rc of the cables. Superconducting properties of the strands were modeled via a power law E-J curve. Power generated in the cable defect was calculated and its influence on cable quench was analyzed. MQE was estimated as a function of Ic for the cable for various values of Ra and Rc, and the temporal evolution of the quench is displayed for a characteristic case.

Speaker: Milan Majoros (The Ohio State University)

361 Tue-Mo-Po2.13-05 [112]: The Superconducting NbTi Wirе for the Superconducting Dipole Magnet for CBM Experiment at FAIR

The superconducting dipole magnet for the Compressed Baryonic Matter (CBM) experiment at FAIR houses the Silicon Tracking System (STS), and provides a magnetic field integral of 1 Tm which is needed to obtain a momentum resolution of Δp/p = 1% for track reconstruction at FAIR beam energies. The magnet gap has a height of 140 cm and a width of 250 cm in order to accommodate the STS with a polar angle acceptance of ± 25° and a horizontal acceptance of ± 30°. The magnet is of the H-type with a warm iron yoke/pole and cylindrical superconducting coils in two separate cryostats.
About 1 tone of the NbTi conductor (wire) size 2.02 mm × 3.25 mm with filament diameter ~ 40 μm, single piece length 5 km and a Cu/SC ratio of about 7.4 is necessary for the making of superconducting coils.
NbTi conductors (wires) with a high Cu/nonCu ratio and a large cross-sectional area are usually made using the «wire-in-channel» technology. Current-carrying capacity in wires of this type is determined (limited) by the current-carrying capacity of the soldered SC insert. The "wire-in-channel" technology involves using of solders with harmful additives and uneven filament distribution in the copper matrix aggravating heat dissipation.
In this paper, we demonstrate the possibility of successfully producing the NbTi wire of size 2.02 mm × 3.25 mm with a single piece length of 5 km and relative residual resistance (RRR) >200 in the monolithic technology for CBM experiment at FAIR. Critical current exceeds 2270 A (E = 0.1 µV/cm; 5 T; 4,2 K) at the copper/non copper ratio 7.4:1.

Speaker: Mr Yury Karasev (JSC VNIINM (Bochvar Institute))

362 Tue-Mo-Po2.13-06 [113]: Study on High Jc and Low AC Losses NbTi/Cu5Ni Superconducting Wire for HIAF Magnets during recently years in WST

The High Intensity Heavy Ion Accelerator Facility (HIAF) is a new engineering project proposed by Institute of Modern Physics of China. Superconducting magnets will be used as part of the accelerator magnets. When operating at fast-pulsed cycled mode, the superconducting cable will dissipate power (AC loss), which affects the stability of magnet. The main contribution of the AC losses in superconducting wire are hysteresis loss and eddy current losses. Fine filaments design can reduce the hysteresis loss and a resistive inter-filamentary matrix can reduce the inter-filamentary eddy current losses. During recently years, WST has developed several types of superconducting wires with the matrix of CuNi alloy for HIAF project successfully. NbTi/Cu5Ni superconducting wires with filaments number of 10080, 12960, 23760, 36720 and 44064 were designed and fabricated by double stacking method. The microstructure and influence of aging heat treatment on the critical current density, hysteresis loss and break times of NbTi/Cu5Ni superconducting wire were presented in this paper. By reducing the Cu/Sc of sub-elements and improving the Cu shell thickness of final billet, the deformation of outer filament is relatively good, which is helpful to the improvement of critical current density and the decrease of hysteresis loss. Critical current density of six designed wire is between 2600 and 2700 A/mm2 and n value is between 35 and 45 at 5T&4.2K, which demonstrates that no filament breakage occurs in the wire. The Cu5Ni alloy is considered as the inter-filament matrix to reduce inter-filament coupling currents loss. When the filament number increases from 10800 to 44064 and diameter of NbTi filament reduces from 4.5 to 2.5μm, the hysteresis losses reduces from 42.8 to 17.3 J/cm3 at ±3T. The average wire length of six designed wires are more than 2000m, which indicates that WST have the ability of mass production. After 5 years investigation on this type of wire, WST have well obtained the design and fabricated technique and can completely satisfy the requirement of HIAF magnets.

Speaker: Qiang Guo (WST)

Qiang Guo-MT26-poster.pdf

363 Tue-Mo-Po2.13-07 [114]: Effects of Processing Conditions on Critical Current Density and Flux Pinning for Nb3Al Wires Fabricated by Jelly Roll Method

With extremely high critical current density (Jc) and excellent strain tolerance, Nb3Al superconductor is considered as an alternative to Nb3Sn for application of high-filed magnets. However, complexity in the phase formation of Nb3Al hinders the Nb3Al superconducting wires to satisfy the requirement of engineering applications at present. Here, we have reported the improved performance of simple-structured 18-filamnet jelly-roll Nb3Al precursor long wires fabricated with rapid heating and quenching (RHQ) process. The effects of processing conditions such as tensile stress, heating current, and post-heat treatment on the performance of simple-structured 18-filamnet jelly-roll Nb-Al precursor long wires are studied in this work. It is observed that the optimized conditions have significantly improved the performance of the Nb3Al wires. Especially, a balance between the tensile stress and strand structure is important to maintain a continuous processing and a high quality of the wires. Flux pinning mechanism related with the phase formation of Nb3Al is discussed.

Speaker: Yong Zhao (Fujian Normal University)

26th MT-poster-Yongzhao.pptx

364 Tue-Mo-Po2.13-08 [115]: Investigation of the Tape Shaped RHQT-Processed Nb3Al Conductors

National Institute for Fusion Science (NIFS) in Japan is considering about FFHR-d1 (Force Free Helical Reactor) for their future R&D project. Its magnet system will be needed a pair of helical typed coils with the major radius of 15.6 m. Since the maximum magnetic field on the helical coil of FFHR-d1 reaches 11.9 T, the NbTi cable is not applicable. The practical Nb3Sn cable was selected for the ITER (International Thermonuclear Experimental Reactor) project and it might be still one of candidate conductor for FFHR-d1 as well. However, the large helical coil shows 3 dimensional complex forming, it is strongly preferable to apply a React and Wind method for the coil winding. Recently, the STARS (Stacked Tapes Assembled in Rigid Structure) conductor fabricated using 2G-REBCO tapes is being investigated by a research group of NIFS and Tohoku University. The 2G-REBCO tape shows a large critical current density at 4.2 K, and also mechanically strong due to the hastelloy substrate. In addition, its thin tape shape may be good advantage to keep a small bending strain with flat-wise direction. In this paper, the RHQT(Rapid Heating/Quenching and Transformation)-processed Nb3Al tapes with 0.2 mm in thickness were fabricated, and their superconducting properties and microstructures were investigated. We propose the Nb3Al conductor as another candidate for FFHR-d1. It is well known that Nb3Al conductor shows an excellent strain tolerance and is promising very much for a React and Wind method for the coil winding. In addition, Cu stabilized long wire with over one kilometer length has already been made by NIMS (National Institute for Materials Science). We will report the transport critical current at 4.2 K of the 0.2 mm thick Nb3Al tape soldered on brass fixtures, which have different radius down to 15 mm. Maximum bending strain corresponds to 0.66% in this study.

Speakers: Akihiro Kikuchi (National Institute for Materials Science), Mr Kyohei Yamada (Sophia University)

MT26_Poster_Tue-Mo-Po2.13-08.pdf

MT26_Poster_Tue-Mo-Po2.13-08.pptx

365 Tue-Mo-Po2.13-09 [116]: Phase structure and superconducting properties of RHQT Nb3Al wires fabricated by static and dynamic rapid heating

This work compared the phase structure and superconducting properties of RHQT Nb3Al wires fabricated by static and reel to reel (R2R) rapidly heating and quenching conditions. The time for static and dynamic heating of the wire is 0.8s and 0.4s. Rapid heating current (IRHQ) of 67A~69A for static RHQ and 120~122A for R2R dynamic RHQ can fabricated ductile precursor wires and obtain single phase Nb3Al wires after low temperature transformation process. The Tc-onset of RHQT Nb3Al wires are about 16.8 K under various heating conditions and Tc-mid changed between 16.6K and 12K depending on the heating current. Compared to wide superconducting transition of 3K for the static RHQT samples, R2R RHQT Nb3Al wires show much smaller ΔTc of about 1K, indicating significant improvement of composition homogenous in the formed A15 phase. The critical current density (Jc) of RHQT Nb3Al fabricated by R2R RHQ is stable of 4.0~4.5×105A/cm2@4.2K, 7T which is almost independent of the heating current, meanwhile, static RHQ wires show Jc in the range 5×104A/cm2~1.1×105A/cm2@4.2K, 7T. For the samples fabricated under smaller current of static RHQ (64A~65A) and higher current of dynamic RHQ (123A~124A), Nb2Al impurity phase was generated in the RHQT Nb3Al wires. These wires exhibit much lower Jc performance of 2×103A/cm2 for static RHQ and 5×104A/cm for R2R dynamic RHQ samples @4.2K, 7T. The main pinning mechanism of Nb3Al superconducting wires was grain boundary pinning, as deduced from the fitting of flux pinning force versus applied field curves.

Speaker: Dr Zhou Yu (Superconductivity and New Energy R&D Center (SNERDC), Key Laboratory of Magnetic Levitation Technologies and Maglev Trains (Ministry of Education), Southwest Jiaotong University, Chengdu, Sichuan 610031,China)

MT26-Poster-Yu.pdf

MT26-Poster-Yu.pptx

366 Tue-Mo-Po2.13-11 [117]: Dimensional Changes of Nb3Sn Conductors During Heat Treatment Using Digital Image Correlation

In order to develop future particle colliders such as the HiLumi - Large Hadron Collider (HL-LHC) and the Future Circular Collider (FCC), high field superconducting Nb3Sn magnets are necessary. Following the winding, the conductor requires a heat treatment at 650 °C during which significant dimensional changes occur. If dimensional changes are not allowed by the tooling, mechanical stresses build up in the coils and the performances of the magnet degrade. Therefore, coil fabrication tooling must authorize these dimensional changes in order to prevent conductor degradation and improve magnet performances. However, quantitative dynamics of the thermomechanical behavior of Nb3Sn conductors during heat treatment remains unknown. This study describes how a DIC (Digital Image Correlation) approach has been used for the first time to observe the displacements fields of Nb3Sn samples during heat treatment at 650 °C. To do so, a furnace equipped of portholes allows observing the sample at high temperature. Two digital cameras record the displacements at the surface of the sample (for example a Rutherford cable), from different viewing angles. Finally a DIC algorithm reconstructs the evolution of the displacements fields. The advantages of the method, compared to classical methods, are to have access to in-situ dimensional changes at high temperature, in the three directions of space, with the dynamics during the heat treatment cycle. An analysis of measurements on representative samples is given and data are compared to the literature.

Speaker: Mr Etienne Rochepault (CEA Paris-Saclay)

Poster_MT26_DIC v3.pdf

367 Tue-Mo-Po2.13-12 [118]: Study on the defects degree and flat-rolling reduction of round wires of Nb3Sn Rutherford Cable for High-Energy Accelerators

The advantages of superconducting Rutherford cables are that it can reduce the inductance and increase the stability of superconducting magnets. Due to its high critical field strength and high current carrying capacity Nb3Sn Rutherford cable is one of the best choices for making high field accelerator superconducting magnets. But Nb3Sn superconducting wire has poor mechanical properties and the current carrying capacity is reduced with the increase of strain. Therefore during the preparation of the Nb3Sn Rutherford cable the difficulty is to control the strain of the Nb3Sn wire and to reduce the attenuation of the current carrying capacity. In order to simulate the deformation of the Rutherford cable at the corner the flat-rolling method is used. With the different flat-rolling heights the different deformation degrees is caused to measure the influence the properties of different wire structures and different wire design parameters. The properties reduces as the flal-rolling height increases. The results of the properties, the flat-rolling parameters and the microstructure of strands of Rutherford Cable are discussed together.

Speaker: Mrs Yanmin Zhu (Western Superconducting Technologies Co., Ltd)

Tue-Mo-Or7 - LHC Upgrade and High Field Magnets for Future Colliders

Conveners: Charlie Sanabria (Commonwealth Fusion Systems), Giorgio Ambrosio (Fermilab)

368 Tue-Mo-Or7-01: Assembly and First Test of a 15 T Nb3Sn Dipole Demonstrator

U.S. Magnet Development Program (MDP) has developed a 15 T Nb3Sn dipole demonstrator for a post-LHC pp Collider. The magnet design is based on 60-mm aperture 4-layer shell-type coils, graded between the inner and outer layers to maximize the magnet performance. The cable in the two innermost layers has 28 strands 1.0 mm in diameter and the cable in the two outermost layers has 40 strands 0.7 mm in diameter. Both cables have been developed and fabricated at Fermilab in long lengths using RRP Nb3Sn wires produced by Bruker-OST. An innovative mechanical structure based on aluminum I-clamps and a thick stainless steel skin is used to preload brittle Nb3Sn coils and support large Lorentz forces at high fields. The maximum field for this design is limited by 15 T due to mechanical considerations. The first magnet assembly was done with lower coil pre-load to minimize the risk of coil damage during assembly. This paper describes the design of the 15 T dipole demonstrator and the details of the magnet assembly procedure. First results of magnet cold tests including quench performance and strain gauge measurements in the temperature range of 1.9-4.5 K are presented and discussed.

Speaker: Dr Alexander Zlobin (Fermilab)

Tue-Mo-Or7-01-Novitiski.pdf

369 Tue-Mo-Or7-02: First field quality measurements of a 15 T Nb3Sn Dipole Demonstrator

Within the US Magnet Development Program (MDP) a 15 T Nb3Sn dipole was developed, to demonstrate a magnet design for a post-LHC pp Collider. The magnet design is based on 60 mm aperture 4-layer shell-type coils, graded between the inner and outer layers to maximize the magnet performance. The cable in the two innermost layers has 28 strands 1.0 mm in diameter and the cable in the two outermost layers has 40 strands 0.7 mm in diameter. Both cables use RRP Nb3Sn wires produced by Bruker-OST. Magnet coils are surrounded by vertically-split thick iron laminations, connected by aluminum I-clamps, and a thick stainless-steel skin. The magnet was tested at the Vertical Magnet Test Facility (VMTF) at Fermilab. This paper reports the first results of magnetic measurements of the 15 T Nb3Sn dipole demonstrator including geometrical harmonics, coil magnetization and iron saturation effects. The experimental data are compared with the magnetic calculations.

• This work is supported by Fermi Research Alliance, LLC, under contract No. DE-AC02-07CH11359 with the U.S. Department of Energy.

Speaker: Thomas Strauss (Fermi National Accelerator Laboratory)

MT26 presentation.pdf

370 Tue-Mo-Or7-03: 3D Design of F2D2, the FCC Block-coil Short Model Dipole

F2D2, the FCC Flared-ends Dipole Demonstrator, is a 15 T single-aperture short model being developed within a collaboration between CEA Paris-Saclay and CERN. The design phase is ongoing at CEA; the magnet will be fabricated at CEA and then tested at CERN. The 2D magnetic and mechanical designs have been optimized previously and allowed defining the operating points and the required structural components. This paper reports on the preliminary design phase, focused on 3D mechanical optimizations of coils and structure. F2D2 will be the first Nb3Sn block-coil magnet using two cable grades. The cables will be spliced outside of the magnet, which represent one of the most complex design feature, and requires a special focus on the magnet ends. To do so, the design of the magnet has been performed using a CAD (Computer Aided Design) and both magnetic and mechanical 3D FEM (Finite-Elements Models). The CAD defines precisely the complex coil-ends shape that allows positioning the layer jumps and routing the cable exits. The FEM are used to optimize the longitudinal pre-load system in order to contain the large Lorentz forces during operation. The magnet is pre-loaded transversally with bladders and keys and with an external Al shell; and longitudinally with Al tie-rods and end-plates. The pre-load levels are computed to operate the magnet under sufficient compression, while minimizing the stress in the coil and avoid degradation.

Speaker: Mr Etienne Rochepault (Université Paris-Saclay (FR))

Rochepault - MT26 - F2D2 v3.pdf

Rochepault - MT26 - F2D2 v3.pptx

371 Tue-Mo-Or7-04: High Field Magnet Program for Accelerators in China: Status and Plan for Future

High field superconducting magnet technology is the key to the success of the high energy particle accelerators. China is pursuing high field magnet R&D for future particle colliders like the Super Proton Proton Collider (SPPC). SPPC will need thousands of high field (12-20 T) superconducting magnets in around 20 years. A long term R&D roadmap of the advanced superconducting materials and high field magnets has been made, aiming to push the technology frontier to the desired level, and a strong domestic collaboration is established, which brings together expertise of Chinese superconductivity community from fields of physics, materials, technology and application. In the past years model magnets with hybrid coils (NbTi, Nb3Sn and iron-based superconductors) have been developed and tested: a model dipole reached >10T main field in the two apertures at 4.2K, the 1st iron based superconducting coil in the world was successfully tested at 24T background field, and dipole magnets with CCT configuration for HL-LHC is under development. An overview of the high field magnet program: R&D status and the future plans will be presented.

Speaker: Qingjin Xu (IHEP)

20190925-High_Field_Magnet_RD_for_Accelerators_in_China-MT26.pdf

372 Tue-Mo-Or7-05: Electromagnetic design, fabrication and test of LPF2: a 12-T hybrid common-coil dipole magnet with inserted IBS coil

High field dipole magnets with common-coil configuration are under development at IHEP (the Institute of High Energy Physics, Chinese Academy of Sciences) for key technology pre-study of high energy colliders like SPPC (Super Proton-Proton Collider). A model magnet named LPF1 has been fabricated and tested in 2018, which was made up of 4 flat racetrack NbTi coils and 2 flat racetrack Nb3Sn coils, and a main dipole field of 10.2 T has been reached in the two apertures at 4.2 K. A new model magnet LPF2 is being designed and fabricated in 2019, with 4 new Nb3Sn coils included comparing with LPF1, and the magnet is expected to reach a much higher field. To reduce the field enhancement at the coil ends, the new fabricated Nb3Sn coils are designed with different straight lengths and bending radiuses. This hybrid dipole magnet is designed to provide a 12-T main field in the up and bottom apertures with an operating current of 5300 A, corresponding to a load line ratio of 78 % at 4.2 K. A single-pancake racetrack IBS (Iron-based superconducting) coil wound with a 100-m IBS tape is inserted into the middle of the magnet. This magnet is also used to test the IBS coil performance under high field and high stress. The main design parameters, fabrication process and the test results of the magnet will be presented.

Speaker: Dr Chengtao Wang (IHEP, CAS)

Tue-Mo-Or7-05-Wang.pdf

Tue-Mo-Or8 - High Tc Wires and Cables I

Conveners: Drew Hazelton (SuperPower Inc.), Venkat Selvamanickam (University of Houston)

373 Tue-Mo-Or8-01: Low cost transposed cables for coil windings made with REBCO 2G HTS tapes

ABSTRACT BODY:
HTS tapes, because of their widths and large shape aspect ratios, have not been readily manufacturable into Rutherford or Roebel cables, even though these kinds of cables are required for many large coil applications. A type of transposed Roebel cable is under development with 2G tape, but its design flexibility is very limited, and its processing very complex, as well as requiring that much of the expensive 2G tape feedstock be discarded. However, our recent advances in cabling provide an opportunity to develop and produce long lengths of low-cost HTS transposed tape cables for fabricating many types of coils. Using our cable design model, combined with the properties of 2G, we have identified architectures for producing prototype transposed HTS tape cables by this new cabling approach. Test runs with a 6-strand cabling machine were completed to establish the feasibility of producing and attaining target performance levels. Degradation of Ic in the cabled tapes, as compared to their pre-cabled Ic’s was found to be minimal. Bend tolerance tests on cables comprised of 8 and 16 tapes demonstrated that Ic does not start to decrease until bend diameters go well under 20 cm. Longer length cables were produce and test coils wound – with tests confirming that these cables are well suited for the fabrication of HTS-based coils with the required large operating currents. These developments pave the way to now develop and produce long lengths with many more tapes and achieve 2, 5 and 10 kA class cables for high field usage in a large variety of magnet types.

Speaker: Dr Alexander Otto (Solid Material Solutions, LLC)

374 Tue-Mo-Or8-02: Recent progress on CORC® cable and wire development for magnet applications

Advanced Conductor Technologies is developing high-temperature superconducting Conductor on Round Core (CORC®) cables and wires wound from REBCO coated conductors for use in high-field magnets. Magnet applications on which the conductor development is focused on include compact fusion magnets that operate at currents between 50 and 100 kA at fields of 12 – 20 T and accelerator magnets that operate at currents exceeding 10 kA and engineering current densities (Je) of over 600 A/mm2 at 4.2 K in a background field of 20 T. Here, we outline the latest results of CORC® cable and wire development tailored for each magnet application. We’ll discuss the improvements of CORC® wires with respect to in-field performance and flexibility required for high-field accelerator magnets through improved pinning performance and reduction of the substrate thickness from 30 down to 25 μm in tapes from SuperPower. The design of several CORC® Cable-in-Conduit-Conductors (CICC) for fusion magnets will be discussed. The CORC®-CICC are designed with improved mechanical support of the bundle of 6 CORC® cables, or 10 – 14 CORC® wires, to ensure sufficient mechanical resilience against transverse compressive stresses when operated at 50 – 80 kA at 10.8 T later this year in the SULTAN test facility at the Paul Scherrer Institute in Switzerland.

Speaker: Danko van der Laan (Advanced Conductor Technologies)

375 Tue-Mo-Or8-03: Measurements of the Effect of Compressive Load on the Narrow Side of the HTS Tape

Brookhaven National Laboratory (BNL) is building a 25 T, 100 mm cold bore HTS solenoid for the Center for Axion and Precision Physics (CAPP) at the Institute for Basic Science (IBS) in Korea to be used in their search for Dark Matter Axions. The magnet is wound using - Second Generation (2G) High Temperature Superconductor (HTS) tape from SuperPower. The combination of high magnetic field (>20 Tesla) and large aperture will result in high stresses within the magnet, with hoop stresses approaching 500 MPa (applied on the wide side of the HTS tape) and axial stresses approaching 200 MPa (applied on the narrow side of the HTS tape). While studies show that the 2G HTS tape from SuperPower with 50µm Hastelloy substrate and 20µm copper stabilizer performs within limits under hoop stresses of 500 MPa, there is no experimental data available showing the effects of high axial stress on the performance of the 2G HTS tape. To validate the conductor choice for the magnet, BNL fabricated an experimental cryogenic (77K) compression setup that would replicate the mechanical stresses the conductor and coils in the IBS magnet would experience during operation. A series of compressive tests were performed at 77K on 2G HTS tape from SuperPower with a Hastelloy substrate thickness of 50µm and copper stabilizer layer thicknesses of 65µm, 40µm, and 20µm. The initial design and several iterations in the test setup, along with the test results, will be discussed.

*This work was carried out under a research agreement between Institute of Basic Science, Korea and Brookhaven Science Associates, LLC under contract No. IBS-NF-16-32. This work was also supported by Brookhaven Science Associates, LLC under contract No. DE-SC0012704, with the U.S. Department of Energy.

Speaker: Shresht Joshi (Brookhaven National Laboratory)

MT26_SJoshi_CompressionTest_Tue-Mo-Or8-03.pdf

MT26_SJoshi_CompressionTest_Tue-Mo-Or8-03.pptx

376 Tue-Mo-Or8-04: Hoop stress concentration in an HTS tape coil under external magnetic fields

The use of REBCO inner coils is a promising option for developing high-field magnets since the coil can be designed at high-hoop stress typically at >400 MPa. Such a coil, however, sometimes suffers from the appearance of a normal voltage even at medium hoop stress such as 200 MPa, i.e., unexpected degradation [1]. We believe that those degradations are caused by strong electromagnetic forces in high magnetic fields. REBCO conductors are very weak against stress concentration modes caused by electromagnetic forces, such as cleavage/peeling (Mode #1), buckling (Mode #2), and axial tensile stress under edgewise bending (Mode #3). In a previous paper [1], we predicted a degradation due to hoop stress concentration in Mode #3 caused by screening currents. In fact, recently, effects of screening current-induced stress [2] have been reported both experimentally [2] and numerically [3].
In the present work, we investigated the effect of conductor thickness on hoop stress concentration using structural analysis for a current transport one-turn tape coil under an external field, in which coil Lorentz force originated from the screening current is considered. It gave a hoop stress distribution in the superconducting layer, which results in Mode #3 stress concentration. We obtained the maximum circumferential stress, σ_max, and compared it to the ideal hoop stress, BJR. We found that the stress concentration factor, defined by σ_max/BJR, drastically depends on the geometry of the tape conductor. This result is of great importance for conductor selection for the design of a high-field HTS inner coil.
[1] Kajita et al. SuST 30 (2017) 074002
[2] Hahn et al. Presented at ASC2018 (2018) 4LOr3B-01
[3] Ueda et al. Presented at 97th Ann. Conf. Cryo. Soc. Japan (2018) 3C-a09
This work was supported by the JST Mirai-Program Grant Number JPMJMI17A2.

Speaker: Shunji Takahashi (Sophia University)

Tue-Mo-Or8-04.pdf

377 Tue-Mo-Or8-05: Effect of thermal mismatch stress and electromagnetic loads on delamination in REBCO coated conductors

Rare Earth-Barium-Copper-Oxide (REBCO) coated conductor (CC) tapes are promising conductors for high energy and high field applications. In the case of epoxy-impregnated REBCO superconducting coils, however, excessive transverse stresses generated from cooling, and Lorentz forces on the CC tapes can cause delamination, resulting in reductions in the load-carrying capacity as well as significant degradation in the coil’s critical current. In this study, a simplified representative element of REBCO CC coils is used to qualitatively study the influence of thermal mismatch stress and electromagnetic force on delamination in REBCO coated conductor by finite element model. First, a 2D REBCO CC delamination model based on the cohesive zone model (CZM) is constructed. All the adjacent layers are coupled via spring equations under the CZM framework to character the interfacial failure due to delamination. The basic delamination properties such as deformation of each constituent layer, interfacial stiffness and interfacial traction varying with transverse mechanical load are presented. Furthermore, the thermal and electromagnetic loads influence on delamination behaviors are intensively discussed. The results show that the CZM defined on the interfaces have strong influence on stresses/strains distributions in each constituent layer even through no delamination occurs. As the electromagnetic force are generated in REBCO layer, both the stresses/strains distributions and delamination behaviors are significantly influenced by the magnitude and direction of the electromagnetic force. Thermal mismatch stress generated during cooling process in a large temperature range also has the possibility to lead to delamination in REBCO CC. The insulation’s characters, such as thickness, elasticity modulus, coefficient of thermal expansion, prestress of the insulation, are all strong effect the delamination behaviors of REBCO CC. Additionally, the occurrence of delamination on the interface between insulation and CC tape can effectively prevent of delamination of REBCO CC tapes. The FEM analysis provides an effective method to investigate thermal stress and electromagnetic force influence on delamination behaviors of REBCO CC, which is helpful for REBCO CC application in cryogenic temperature and electromagnetic field.

Speakers: Dr Peifeng Gao (Lanzhou University), Prof. Xingzhe Wang (Lanzhou University)

Tue-Mo-Or8-05-Peifeng Gao_MT26.pdf

378 Tue-Mo-Or8-06: Bi2223 persistent current coil with superconducting joint fabricated by JIM method

Recently, we developed a superconducting joint between two multi-filamentary Bi2223 tapes with the joint by incongruent melting (JIM) method [1]. During the incongruent melting process, Bi2223 phase is separated to Bi2212, Bi2201, and liquid phases. Since the Bi2212 is also high-temperature superconductor, the superconducting joint can be obtained without recrystallization of Bi2223 from the Bi2212 and liquid, during a short heating treatment as 1 min at 890 °C. To obtain a high critical current, it is better to keep the crystal orientation of Bi2223/Bi2212 filaments with crystal growth at interface of joint along vertical direction of tape (c-axis). In this study, we suggested a lap-type multi-junction method to increase the effective interface area of superconducting current path, toward improvement of the critical current. In experiment, three junctions for a joint sample was prepared and obtained critical current above 16 A at 77 K. We have been obtained the critical current of 177 K at 4.2 K for joint fabricated by JIM method, which is about 15 times that measured at 77 K (12 A). Considering this increasing rate, the multi-junction sample may have a large critical current above 200 A at 4.2 K. The resistances at 77 and 4.2 K in a persistent current coil show the same ultra-low value about 1 pΩ, after half a day or less from the start of persistent current operation [1]. The measurement results for Bi2223 persistent current coil with the joint will be presented in MT26 at Vancouver.

Acknowledgements:
This work was supported by JST-Mirai Program Grant Number JPMJMI17A2, MEXT project of Leading Initiative for Excellent Young Researchers (LEADER) Project ID 16810210, and JSPS KAKENHI Grant Number JP18K04719, Japan.

[1] X. Jin, Y. Suetomi, R. Piao, Y. Matsutake, T. Yagai, H. Mochida, Y. Yanagisawa, H. Maeda, “Superconducting joint between multi-filamentary Bi2Sr2Ca2Cu3O10+δ tapes based on incongruent melting,” Supercond. Sci. Technol., vol. 32, 2019, Art. no. 035011.

Speaker: Dr Shintetsu Kanazawa (Muroran Institute of Technology)

Tue-Mo-Or8-06_MT26_Bi2223joint_2019.pdf

379 Tue-Mo-Or8-07: Superconducting joints between Bi2223/Ag tapes towards persistent current HTS magnets

For realizing HTS magnets equipped with a persistent current circuit, the development of superconducting joints between HTS tapes with enough large current capacity in external magnetic fields is indispensable. On the other hand, the Ag-sheathed Bi2223 (Bi2223/Ag) commercial tapes, DI-BSCCO, show high critical current (I_c) characteristics of ~ 200 A at 77 K in self-field and above 400 A at 4.2 K under high magnetic fields such as 20 T. DI-BSCCO tapes have been widely used for power cables and superconducting magnets for various applications including a high-resolution NMR system, while the practical superconducting joint technology for Bi2223/Ag tapes has not been developed thus far.
In our recent study, a superconducting joint with high I_c above 400 A at 4.2 K in self-field connecting DI-BSCCO tapes was successfully demonstrated [1]. In addition to the improvement in I_c properties for joints including under fields, the design of optimal joint configurations is needed, which enables joint parts to be introduced in the actual superconducting magnet systems. These developments should lead to the realization of persistent current Bi2223/Ag magnets. Based on these backgrounds, the achievement of high joint I_c characteristics under wide temperature and field conditions and in various joint configurations has been aimed in this study. Furthermore, the result of experiments to evaluate joint resistance using circuits with a persistent current loop consisting of DI-BSCCO tapes will also be reported.

[1] Y. Takeda et al., Appl. Phys. Express 12 (2019) 023003.

Acknowledgments:
This work was supported by JST-Mirai Program Grant Number JPMJMI17A2, Japan.

Speaker: Yasuaki Takeda (The University of Tokyo)

Tue-Mo-Or8-07_Takeda.pdf

380 Tue-Mo-Or8-08: Critical Current – Strain Dependence, Ic(ε), of Solenoids Wound with Bi-2212 Round Wire

New high temperature superconductor (HTS) technology is actively being pursued to achieve fields beyond those available with the present Nb3Sn technology (~23 T). In an effort to further drive Bi2Sr2CaCu2O8-δ (Bi 2212) round wire technology, better understanding of the performance of coils wound with this conductor is paramount. Work presented in this body demonstrates that the limiting strain dependence on the critical current of short samples, Ic(ε)-limit, found in the literature can very accurately and precisely translate into coil performance limits. Extensive multiphysics finite element modeling (FEM) was utilized to design the prototype coils that were manufactured and operated up to their strain-limited peak performance. The quantitative agreement between the predictive modeling and experimental coil results validates the modeling accuracy and further serves to illustrate that coil performance limitations are well understood. In order to venture into the >23.5 T (>1 GHz NMR) range, a multitude of reinforcement techniques are being further evaluated to mitigate the strains borne from the Lorentz stresses so that these prototype coils can be scaled up to larger magnet systems.

This work is supported by the US DOE Office of High Energy Physics under grant number DE-SC0010421, the National Science Foundation under DMR-1157490 and DMR-1644779, by the state of Florida, and is amplified by the U.S. Magnet Development Program (MDP).

Speaker: Ernesto Bosque (National High Magnetic Field Laboratory)

190925 Bosque Ic(strain).pdf

Tue-Mo-Or9 - MRI Magnets I

Conveners: Dr Hitoshi Kitaguchi (National Institute for Materials Science), Michael Parizh (GE Global Research)

381 Tue-Mo-Or9-01 [Invited]: Commissioning completion of the Iseult Whole Body 11.7 T magnet

Neurospin is a neuroscience research center located in France at CEA Saclay. The facility is already hosting several MRI magnets and Iseult, an innovative Whole Body 11.7 T MRI system, will be available very soon. The core part of Iseult is an actively shielded NbTi magnet cooled with a superfluid helium bath at 1.8K, that will provide a homogeneous field of 11.7 T within a 90 cm warm bore. The project was launched in 2002, and after 15 years of work and efforts, the magnet successfully reached its nominal field in July 2019. The paper will summarize the project history, from the early design phase to the commissioning tests performed a few weeks ago. The prototyping activities, the magnet manufacturing, as well as the cryogenic and electrical facilities required to operate Iseult will be also described. The last section will cover the magnet commissioning, from the cooling phase to the step-by-step energization up to the nominal current.

Speakers: Dr Lionel Quettier (CEA), Dr Pierre Vedrine (CEA), Thierry Schild (ITER)

382 Tue-Mo-Or9-02 [Invited]: Development of High Stable Field REBCO Superconducting Magnet for MRI

Research and development for the practical application of a medical-use magnetic resonance imaging system (MRI) superconducting magnet that requires without liquid helium started as the New Energy and Industrial Technology Development Organization's (NEDO) supported project in fiscal 2016. Development of a liquid helium-free medical MRI superconducting magnet is desired. Another purpose is to reduce the size and weight of high magnetic field magnets. By using the high temperature superconducting coil, it is possible to make the 3T magnet as shape, weight, leakage magnetic field as 1.5T magnet. In this project, we are developing a half size active shield-type 3T REBCO coil for MRI. This magnet has active shield coils with a maximum diameter of 1200 mm, and the room bore diameter is 480 mm. This magnet is one of the largest in the world as a magnet using a REBCO wire with an accumulated energy of 1.6 MJ at the rated magnetic field. It is a magnet system with magnetic field uniformity and magnetic field stability necessary for imaging. In this paper, we report the half-size active shield-type 3T coil and the cooling system that can reduce the initial cooling time.
Acknowledgement
This research received grants and support from NEDO "development of an HTS magnet system with highly stable magnetic field" as part of the "promotion technology development for HTS practical application."

Speaker: Shoichi Yokoyama (Mitsubishi Electric Croporation)

383 Tue-Mo-Or9-03: Development of quench tolerant epoxy impregnated REBCO coils for an HTS MRI magnet

Coils for rare-earth barium copper oxide (REBCO) high temperature superconductor (HTS) magnets are often wound with insulation between turns (i.e. effectively infinite resistance). In this case, magnetic field generated by the coil is linearly related to the transport current in the coil, allowing voltage-limited magnet ramping. However, quench protection has been shown to be hard to implement using either standard passive or active quench protection schemes.

Introducing a finite resistance between turns adds a new radial current path in addition to the desired azimuthal current path. Now current may automatically bypass quenched areas, avoiding irreversible damage. However, finite resistivity between turns means that there may no longer be a linear relationship between transport current and magnetic field. The lag between the transport current reaching its operating value and the coil field reaching its operating value we term the settling time. Setting the resistivity between turns allows control of the settling time, which in turn determines how readily current may bypass quenched areas in the event of quench.

We wish to manufacture a quench tolerant ReBCO MRI magnet, making use of epoxy encapsulated coils for strength, with finite resistivity between turns. However, it is well-known that any magnet for magnetic resonance applications requires excellent field stability and uniformity. Magnets with low turn-to-turn resistivity have been shown to have excessively long settling times which will yield a slowly changing magnetic field magnitude and uniformity unsuitable for MRI. We have therefore developed software to model and calculate the turn-to-turn resistivity

Speaker: Mr Konstantinos Bouloukakis (Robinson Research Insitute)

Tue-Mo-Or9-03_Bouloukakis_MT26.pdf

384 Tue-Mo-Or9-04: Magnetic, mechanical and thermal modeling of superconducting, whole-body, actively shielded, 3 T MRI magnets wound using MgB2 strands for liquid cryogen free operation

In this study we performed magnetic, mechanical and thermal modeling of a 3T actively shielded whole body MRI (Magnetic Resonance Imaging) magnet. The final design had an overall magnet length and conductor length which can lead to conduction cooled designs which are comparable to NbTi helium bath cooled 3 T designs. The design had a magnetic field homogeneity better than 10 ppm (part-per-million) within a DSV (Diameter of Spherical Volume) of 49 cm. A new class of MgB2 strand especially designed for MRI applications was considered as a possible candidate for winding such magnets. The magnet design was a segmented coil type optimized to minimize conductor length while hitting the standard field quality and DSV specifications as well as a standard, compact size 3 T system. Unlike the frequently used Helmholtz-like coil pair design (even number of coils, typically 8 or 10 coils in total) we used a Maxwell-like configuration (an odd number of coils, containing 9 coils in total). This Maxwell-like coil design is advantageous for a number of reasons, in particular because it can allow a higher inner winding diameter in the central part of the MRI magnet. The final design achieved 3 T in the bore, with 10 ppm homogeneity in a 49 cm DSV. The total magnet length is 1.37 m, and the total conductor length is 121 km. The operational current is 287 A, and based on a 4.2 K Ic = 383 A, this gives I/Ic = 0.75. This work represents the first magnetic design for a whole-body 3 T MgB2-based MRI magnet for a short (1.37 m length) magnet which uses the performance parameters of existing MgB2 wire. This result represents a strong step towards a viable 3 T, whole body, conduction cooled MRI based on MgB2 conductor.

Speaker: Prof. Mike Sumption (The Ohio State University)

385 Tue-Mo-Or9-05: A Tabletop, Liquid Helium-Free, Persistent-Mode 1.5-T MgB2 “Finger” MRI Magnet: Test of a Half-Scale MRI-Quality Magnet

In this paper, we present construction and persistent-mode operation results of a half-scale 1.5-T/54-mm room-temperature bore MgB₂ MRI-quality magnet for the development of a tabletop “finger” MRI system. A half-scale magnet, composed of 5 coil sections and a persistent-current switch, was wound with a single ~590-m long unreacted/monofilament MgB₂ wire having a superconducting joint, and then heat-treated. We operated the magnet, immersed in liquid nitrogen and cryocooled, successfully, achieving a persistent-mode 1.5-T field at the target operating current of 112 A in the temperature range 10-15 K. We also evaluated a temporal stability and a before-shimmed bare field homogeneity of the magnet by using both a hall probe and an NMR probe. Our discussion includes the spatial field homogeneity difference between as-designed and as-built magnets in consideration of manufacturing tolerance.

Acknowledgement: Research reported in this publication was supported by the National Institute of Biomedical Imaging and Bioengineering of the National Institutes of Health under award number R01EB022062.

Speaker: Dr Dongkeun Park (Francis Bitter Magnet Laboratory / Plasma Science and Fusion Center, Massachusetts Institute of Technology)

MT26_YChoi_DPark_submitted (Tue-Mo-Or9-05).pdf

386 Tue-Mo-Or9-06: Ultra-compact MRI System with High Temperature Superconducting Magnet

This paper presents the design of a high field and portable MRI magnet system for the rapid and early diagnosis of brain trauma. Early diagnosis and therapy stratification can reduce the risk for critically brain ill patients with the use of near patient imaging, and can aid with precision medicine. High temperature superconductors have the ability to carry large currents at higher temperatures than low temperature superconductors. We wish to fully leverage this ability by employing a flux pump to charge the MRI magnet which we have designed. The higher the current which can be employed the lower the inductance of the magnet for a given field. This has several effects. First it reduces cost by reducing the amount of superconductor (this mitigates against the high cost of HTS). Second it makes the magnet smaller and lighter. Third it reduces the amount of stored energy in the magnet and thereby mitigates against quench.

In summary the key component for compact MRI is a compact and high field superconducting magnet. Using an HTS flux pump provides the means to eliminate the reliance on expensive high current power supplies and thermally wasteful current leads. An HTS based main magnet with 1 ppm uniformity in a 10 × 10 × 5 cm elliptical volume has been designed, for incorporation into an MRI system and will be used in pre-clinical tests.

Speaker: Dr Timothy Coombs (University of Cambridge)

MT2019 (Boyang Shen).pdf

MT2019 (Boyang Shen).pptx

12:45 Lunch (on your own)

14:00 Coffee Break (during Poster Sessions)

Tue-Af-Po2.14 - No-Insulation Coil Technology

Conveners: Dr Arnaud Badel (Tohoku University), Xavier Chaud (LNCMI-EMFL-CNRS, Univ. Grenoble Alpes, INSA, UPS)

387 Tue-Af-Po2.14-01 [1]: Presentation withdrawn

388 Tue-Af-Po2.14-02 [2]: Design and Performance Estimation of a 20 T No-Insulation all-REBCO User Magnet

This paper reports a design and performance estimation of a 20 T no-insulation (NI) high temperature superconductor (HTS) standalone user magnet currently being developed at the National High Magnetic Field Laboratory. It consists of a stack of 17 double pancake coils wound with tapes from two different vendors, SuNAM and SuperPower, in consideration of their complementary in-field critical current and mechanical properties. The inner and outer winding diameters and overall winding height of the magnet are 58 mm, 127.5 mm, and 149.2 mm, respectively. The magnet is designed to generate a center field of 20 T at its nominal operating current of 280 A in a bath of liquid helium at 4.2 K. The inductance and stored energy are 3.75 H and 147 kJ, respectively. First, we report key design parameters followed by numerical simulations on: (1) NI charging behavior and estimation of liquid helium consumption; (2) stress analysis, before and after quench, taking account of induced overcurrent during quench and the screening current distribution; (3) post-quench behavior including the local temperature rise.

ACKNOWLEDGMENTS
This work was performed at the National High Magnetic Field Laboratory, which is supported by National Science Foundation Cooperative Agreement No. DMR-1644779 and DMR-1839796, and the State of Florida. A part of analysis work by U. Bong and S. Hahn was supported by the National Research Foundation of Korea as a part of Mid-Career Research Program (No. 2018R1A2B3009249).

Speaker: Kwanglok Kim (National High Magnetic Field Laboratory)

MT26_poster_Tue-AF-Po2.14-2_KMK.pdf

MT26_poster_Tue-AF-Po2.14-2_KMK.pptx

389 Tue-Af-Po2.14-03 [3]: Presentation withdrawn

390 Tue-Af-Po2.14-04 [4]: The Effect of Turn-to-Turn Contact Resistance on the Electrical Characteristic and Thermal Stability of 2G HTS Pancake Coils

This paper presents our analysis of the electromagnetic characteristic and thermal stability of 2G high-temperature superconductor (HTS) pancake coils depending on the turn-to-turn contact resistance. Numerical simulations for investigating electromagnetic characteristic, mechanical stress and thermal stability of HTS pancake coils were performed by taking into account different contact resistance between turns based on equivalent circuit model and finite element analysis in COMSOL. Since the electromagnetic characteristics of HTS coil highly depend on the temperature, the current density and the magnetic field vector, it is extremely complex to analyze the stability of HTS coils when the current wave, the magnetic field distribution, heat losses and the cooling condition are taken into consideration. The numerical model of YBCO coils based on H-formulation has the problem of highly non-linear behavior, which means that as the temperature of the HTS coils reach normal state, the E-J power law becomes strongly singularity. To avoid the problem, we propose a new definition of current density in YBCO tape, which is a sum of two components in different stage. To validate the simulation results, four HTS pancake coils co-wound respectively with stainless steel, epoxy, Kapton and non-insulation(NI) coil were fabricated and tested. And then contact resistances of HTS coils were measured under different magnet field and frequency.Chargedischarge, sudden-discharge and over-current tests were performed to evaluate performance of coils. Quench test induced by hot spot disturbance during constant current were performed in different conditions immersed in liquid nitrogen. Beside, a parallel resistance method is proposed to decrease contact resistance. Both numerical and experimental results show that turn-to-turn contact resistance can affect characteristics of time constant, ac loss distribution, thermal stability and mechanical stress in HTS coils. From the study, it is believed that as the contact resistance decreases, the electrical stability increases. The obtained results could be useful in designing HTS coil.

Speaker: Mr Guangda Wang

WGD_2019MT26_Poster.pdf

391 Tue-Af-Po2.14-05 [5]: Electromagnetic and thermal analysis of No-Insulation ReBCO Double Pancake Coils During Charging

This article analyzes the charging behavior of no-insulation high temperature superconducting (HTS) ReBCO double-cake coils under conduction cooling and liquid nitrogen cooling in detail. A partial equivalent circuit model of a determined parameter ReBCO coil is applied to evaluate charging behavior under different cooling conditions. At the same time, the finite element method is used to couple the circuit model with the magnetic field model and the heat transfer model to analyze the changes of the current distribution, magnetic field and temperature of the coil during the charging process. The simulation results obtained by numerical calculation using the coupled model are in good agreement with the results of coil charging experiments under conduction cooling conditions, which also verifies the correctness of the proposed coupled model. In addition, numerical simulation and experiment of different charging rates were carried out under conduction cooling conditions to analyze the excitation characteristics of no-insulation high temperature superconducting magnets in detail.

Speaker: Dr Qiuliang Wang (Institute of Electrical Engineering, Chinese Academy of Sciences)

392 Tue-Af-Po2.14-06 [6]: A critical quench simulation model of No-insulation high temperature superconducting coils with defects

This paper is to study the practical critical current of No-insulation (NI) high temperature superconducting (HTS) coils under local heat disturbances. Based on a multi-physics model that built from an electric network model, a thermal coil model and a magnetic field model, behaviors of a HTS coil under different currents and heat disturbances are compared in this paper. A balance model of HTS coils with tiny persistent Joule heating is proposed, which is compared with the practical measurement results of a REBCO coil and shows a good agreement. In condition of persistent Joule heating, the practical critical current of the coil model is significantly less than the theoretical value. The work can provide an important reference to the analysis of HTS magnets quench behavior.

Speaker: Dr Qiuliang Wang (Institute of Electrical Engineering, Chinese Academy of Sciences)

393 Tue-Af-Po2.14-07 [7]: Over-current test on an intra-layer no-insulation (LNI) REBCO coil under a high background field

The no-insulation (NI) method has provided dramatic progress on the high-field magnet technology in the last decade. An NI REBCO pancake coil can operate at a very high current density supported by a self-protecting behavior. However, it was recently demonstrated that asymmetric distributions of axial forces due to electromagnetic forces during the quench propagation results in serious mechanical damage on the NI REBCO pancake coil [1]. In the case of an NI REBCO layer-wound coil, whose effectiveness was recently demonstrated by using an “intra-layer no-insulation (LNI)” method, it is possible that the coil does not face such degradations because the axially unbalanced electromagnetic forces are hard to occur in an LNI REBCO coil [2]. However, such a potential advantage has not been experimentally demonstrated and in the present work we will conduct over-current experiments on an LNI REBCO coil in liquid helium in an LTS coil background field.
We wound an LNI REBCO coil with a single piece REBCO conductor of 250 m. For applying the LNI method, one-side insulated copper sheets were inserted between all the layers. The coil winding was 18 mm in inner diameter, 70 mm in outer diameter, 40 mm in height. The number of layers was 160 and the total turns were 1604. The LNI REBCO coil and a Bi-2223 coil were series connected and charged in the cold bore of a 17.2 T LTS magnet until the LNI REBCO coil reached a thermal runaway. The LNI REBCO coil eventually showed a thermal runaway at 289.6 A in the center magnetic field of 31.4 T and the coil was protected.

[1] P. C. Michael et al., Presented at ASC2018, 2LOr1D-01 (2018)
[2] Y. Suetomi et al., Supercond. Sci. Technol. 32 (2019) 045003

This work is supported by the JST Mirai-Program Grant Number JPMJMI17A2.

Speaker: Mr Yu Suetomi (RIKEN/Chiba University)

Tue-Af-Po2.14-07_suetomi_poster.pdf

394 Tue-Af-Po2.14-08 [8]: Study of Screening Currents in No-Insulation REBCO Magnets

Recently, we have reported that screening currents in REBCO high field magnets may be a source of large electromagnetic stresses and consequently cause mechanical damage to the superconducting tape. To better estimate the electromechanical behavior of a REBCO magnet even in the initial design stage, we have modeled the distribution of screening currents in an NI REBCO magnet and compared the simulations with experiments to visualize the spatial distribution and temporal change of the screening currents within a REBCO sample tape. A 14 T, 161-mm low temperature superconductor background-field magnet, currently available at the Applied Superconductivity Center of the National High Magnetic Field Laboratory, is used to apply the magnetic field to induce screening currents in REBCO tapes. An array of calibrated Hall sensors is used to measure the time-varying magnetic fields on the REBCO tape’s surface. All tests are performed in a bath of liquid helium at 4.2 K.

Acknowledgement
This work was performed at the National High Magnetic Field Laboratory, which is supported by National Science Foundation Cooperative Agreement No. DMR-1644779 and DMR-1839796, and the State of Florida. A part of the analysis work by J. Bang and S. Hahn was supported by the National Research Foundation of Korea as a part of Mid-Career Research Program (No. 2018R1A2B3009249).

Speaker: Kwanglok Kim (National High Magnetic Field Laboratory)

MT26_Tue-Af-Po2.14-08_KKim.pdf

395 Tue-Af-Po2.14-09 [9]: Elimination of Screening Current-Induced Magnetic Field in a non-insulation REBCO Superconducting Coil Through A Small Size Radio Frequency Antenna

Due to the special rectangular cross section of the REBCO tapes, the screening current-Induced magnetic field (SCIF) in a REBCO high temperature superconducting (HTS) coil will deteriorate the spatial homogeneity and temporal stability of the superconducting magnet, which is a key issue for the application of HTS magnets in the Nuclear Magnetic Resonance (NMR) and Magnetic Resonance Imaging (MRI) devices. In this paper, a method, through a small size radio frequency antenna (RFA) located inside/outside of the REBCO HTS non-insulation coils, was proposed to eliminate the SCIF generated in the REBCO coils. By controlling the eddy current loss generated in the HTS coil, the temperature distributions will be affected, which has an effect on the critical current distributions in the REBCO HTS coil. This will lead to a re-distribution of screening current in the REBCO HTS tape. In the paper, the effects of shape, working conditions, and relative position of RAF on the elimination of SCIF was studied and investigated. An improved numerical method was used to simulate the SCIF in the HTS magnet and the efficiency of the RAF. And also, the related experiments were performed at 77 K and compared with the simulation results, which shows a good agreement. These results will help us design and fabricate a 15 T non-insulated HTS insert for the 30 T all-superconducting magnet in the near future.

Speaker: Dr Lei Wang (Institute of Electrical Engineering, Chinese Academy of Sciences)

396 Tue-Af-Po2.14-10 [10]: Fatigue behavior of No-Insulation Coils with and without Reinforcing Co-Wind

The NHMFL has commenced with the development of an all-superconducting 40 T magnet that will be installed in its DC-Field User Facility. At present various high temperature superconductor technologies are being investigated as candidates for the magnet construction. It is the objective of this early development stage to address questions regarding the application of a type of superconductor to magnet technology through model coil testing and properties measurements. No-insulation (NI) REBCO is a viable conductor and coil configuration for the 40 T magnet but needs further studies to reduce risk and to better understand its ability to perform reliably through long term user operations. The research presented here is focused on the fatigue effects of 500 A, 4 kJ NI test coils with and without reinforcing stainless steel co-wind. The coils contain six double pancakes with an inner diameter of 100 mm and will be operated to strain levels up to 0.4 % in a background field of 6.9 T. The impact of electromagnetic cycling on the REBCO will be studied using Yatestar which is a device that provides a full-length image of the REBCO’s superconducting state via magnetization and transport measurements. The REBCO surface of a non-reinforced coil is oxidized to prescribe a contact resistance and its robustness to the cyclic behavior will be assessed. In addition, the relevance of cracks in the REBCO crystal on the slit-side of the REBCO tape will be examined.

Speaker: Iain Dixon (Florida State University)

Tue-Af-Po2.14-10 [10].pdf

397 Tue-Af-Po2.14-12 [11]: Testing of Quality Assessment (QA) HTS Magnets at Tokamak Energy

Tokamak Energy are developing large scale REBCO HTS magnets for application in spherical tokamaks for fusion energy. As part of our HTS technology development plan, a series of quality assessment (QA) coils have been manufactured and tested. These are non-insulated coils containing ~100 m of HTS tape. The manufacture and testing of these magnets has allowed us to assess the performance of HTS conductors from various worldwide suppliers, as well as to develop magnet construction techniques. Six different QA magnets have been made and tested in total. The magnets were tested using Tokamak Energy’s purpose-built cryogenic test rig, which provides conduction cooling at temperatures in the range 12 - 50 K and currents up to several kiloamps.

This talk discusses the tests conducted and presents a comparison of conductor performance (without identifying the products). The talk concludes with a summary of work on high field demonstrator magnets under way at Tokamak Energy. We aim to reveal the test results for a high field conduction cooled non-insulated HTS solenoid utilizing the novel coil construction methods demonstrated in QA coils.

Speaker: Greg Brittles (Tokamak Energy)

Tue-Af-Po2.15 - Resistive and Hybrid Magnets

Conveners: Satoshi Awaji (Tohoku University), Yunfei Tan (Huazhong University of Science and Technology)

398 Tue-Af-Po2.15-01 [12]: Conceptual Design for a next generation Resistive Large Bore Magnet at the NHMFL

The National High Magnetic Field Laboratory (NHMFL) has successfully operated its 20 Tesla 195mm large bore magnet for over 20 years. Eventually, as there was a certain slowdown in demand for that magnet at the time, it had been decommissioned in 2016 and its two outer coils have been re-used for parts in a higher energy density configuration to facilitate the fast construction of the word record 41.5 Tesla 32mm bore NHMFL resistive magnet. With no resistive large bore magnet providing fields in the 20 Telsa range available for the last two years, the demand or desire for such a facility has been steadily rising. Again, cost and schedule for the construction of such a magnet are critical aspects being under consideration. One elegant solution to keep these factors most manageable is to not design a new stand-alone magnet but to design one or a set of insert coils that is interchangeable with a smaller bore existing magnet at the NHMFL. Different alternative configurations for such a large bore resistive insert including two different existing NHMFL magnets to serve as the outsert as well as different usable bore sizes have been considered on a preliminary level of detail for comparison only. Eventually, a more detailed conceptual design has been developed for a chosen magnet system. In this paper, the authors present a summary of the different alternative considerations as well as an introduction to the conceptual design of a next generation 195mm Large Bore Magnet capable to produce well above 20 Tesla.

Speakers: Dr Jack Toth (National High Magnetic Field Laboratory, Tallahassee, USA), Mr Scott Bole (National High Magnetic Field Laboratory, Tallahassee, USA)

MT26_Toth_poster_Tue-Af-Po215-01-12_001.pdf

399 Tue-Af-Po2.15-02 [13]: Design of the resistive insert for the Nijmegen 45 T hybrid magnet

The High Field Magnet Laboratory of the Radboud University is constructing a 45 T hybrid magnet system. The hybrid magnet is being assembled in one of the six cells of the Nijmegen laboratory. The resistive insert magnet will be energized with the 40 kA, 550 V power converter installed at the HFML.
This paper provides details of the electromagnetic and thermal coil design of the resistive insert magnet, which will be capable of generating at least 32.7 T in the background field of 12.3 T of the 625 mm bore superconducting outsert magnet. Details of the design of the housing will be discussed, in particular the clamping of the coils, necessary to hold the end turns of the coils and the way the housing deals with the fault forces that occur when one or more coils of the insert magnet would fail.

Speaker: Dr Frans Wijnen (Radboud University Nijmegen)

Tue-Af-Po2.15.02.pdf

400 Tue-Af-Po2.15-03 [14]: Failure modes of the insert magnet of a hybrid magnet system: consequences for the mechanical design

The High Field Magnet Laboratory of the Radboud University is constructing a 45 T hybrid magnet system. The measures taken to accept the largest fault forces that can result in the not so unlikely event of failure of parts of the resistive insert magnet, dominate the design of the support structures, in particular those coupling the room temperature resistive insert magnet with the superconducting coil in the cryogenic environment. The largest fault forces arise when half of the insert coil becomes electrically short-circuited in a burn-out accident, and in the case due to the inductive coupling of the resistive and superconducting magnets the mutual axial forces may be as high as 2.5 MN. The mechanical design should guarantee that the structures can sustain these forces with no catastrophic failure.
We will argue, based on evidence of actually observed failure of resistive magnets and models of the observed failure modes, that the fault forces that may realistically occur will be much smaller. In this paper we will elaborate the measures taken in the construction of the resistive insert and superconducting outsert magnets to safely handle the fault forces.

Speaker: Frans Wijnen (Radboud University Nijmegen)

Tue-Af-Po2.15.03.pdf

401 Tue-Af-Po2.15-04 [15]: Redesign and Strength Check of 40T Hybrid Magnet Thermal Shield

The 40T hybrid magnet in Hefei consisting of a 10 T superconducting outsert and a 30 T resistive insert magnet has passed the national evaluation in 2017 and has been running steadily up to now. The thermal shield cooled by liquid nitrogen sandwiched by the superconducting magnet and the water-cooled resistive magnet is the important component of the hybrid magnet. During the debugging phase of the hybrid magnet in 2016, a trip of the water-cooled resistive magnet triggered the quench protection of the superconducting magnet, resulting in expansion and rupture of the oxygen-free copper thermal shield. In this paper, we will reveal the reason of damage of the oxygen-free copper thermal shield via the finite element simulation analysis. We also introduce a new design scheme of the thermal shield adopted by the 40 T hybrid magnet which is currently operating steadily.

Speaker: Dr Zhen Fang (Chinese High Magnetic Field Laboratory ,Chinese Academy of Science)

FZ-Poster.pdf

Tue-Af-Po2.16 - Power Supplies and Flux Pumps II: Transformers

Conveners: Jun Ma (Cambridge University), Yujia Zhai (Hunan University)

402 Tue-Af-Po2.16-01 [16]: Contactless Power Transfer for HTS Magnets with A Novel YBCO-coated Conductor Bridge as Rectifier

Abstract—As a marvelous promotion of applications with HTS magnet in a variety of fields appears, it is of particular importance to compensate persistent current decay in HTS magnets. Therefore, a large quantity of means of contactless power supply (CPT) have emerged in endlessly. In general, CPT mainly consists of 5 parts, which include power, inverter circuit, electromagnetic inductive coupler, rectifier circuit and load. A pretty large proportion of attention has been paid to optimize circuit topology and coupler structure rather than rectifier circuit. According to the majority of proposed methods which utilized diodes as rectifier, the inevitable heat loss resulted from operating diodes is always puzzled. For that reason, this paper presented a novel means, taking the place of diodes with a YBCO-coated conductor bridge which coordinated with a specific programed AC power signal aiming at AC-DC conversion, to decrease unavoidable heat loss from normal diodes rectifier circuit. Once an alternative current where positive peak value is higher than negative peak value is induced in the superconducting secondary winding, it drives the bridge into flux flow region and induces direct voltage between the bridge at around its positive peak value. In consequence, power supply for HTS magnets was accomplished. Apart from that, due to the particularity of this experiment, in which rectifier circuit connected with both secondary coils wound with YBCO-coated conductor and magnet is in the cooling system(77K). So that diodes rectifier has to operate in 77K environment and endures unignorable effect. However, regardless of that defect, the cooling system is coincidently and perfectly suitable for a YBCO-coated conductor bridge. In a word, considering of the whole power supply system, utilizing the bridge is able to reduce heat loss in view of zero resistance. Futhermore, this means also converts the shortcoming towards diodes rectifier circuit in the cryogenic environment into superiority of the bridge.

Index Terms—HTS magnet, contactless power supply(CPT), YBCO-coated conductor bridge

Speaker: Ms Yuke Deng (1.Applied Superconductivity Laboratory, State Key Laboratory of Traction Power, Southwest Jiaotong University, Chengdu, Sichuan 610031, China.2School of Electrical Engineering, Southwest Jiaotong University, Chengdu 610031, China. 2.School of Electrical Engineering, Southwest Jiaotong University, Chengdu 610031, China.2School of Electrical Engineering, Southwest Jiaotong University, Chengdu 610031, China.)

Poster_MT26-DYK-simple.pdf

Poster_MT26-DYK-simple.pptx

403 Tue-Af-Po2.16-02 [17]: Practical Estimation of Superconducting Dynamo Losses

In High Temperature Superconductor (HTS) direct current (dc) magnet applications much of the cryocooler load required for continuous operation is imposed by the external current leads. Operation of HTS dc magnets at high currents requires large cross-section leads, but these leads provide a large thermal bridge between the ambient current supply and the cryogenic superconducting components. Removing these leads would allow smaller cheaper cryocoolers to be used on these magnet systems, and reduce ongoing operation costs.
Superconducting dynamos are a non-contact method of energising HTS coils, and are capable of producing currents in the connected superconducting circuits far in excess of the current supplied at the ambient components. As a non-contact system, the current leads are eliminated. Additionally, this technology eliminates the need for a large high current source to drive high current magnets, further reducing capital and operating costs.
Previous work on superconducting dynamos has focussed on driving larger currents, and understanding the constraints which govern the efficacy of the energisation behaviour. It is known that the varying magnetic field strength at the superconducting surface of the superconducting dynamo will result in some AC losses, however in the quest for higher currents the extent of these losses and other system losses have not been considered.
In this work the losses of a multi-stator “squirrel-cage” superconducting dynamo are investigated experimentally, and compared to the losses expected in the conventional copper current lead based energisation method.
At present, the thermal load associated with conduction cooled copper leads prevents practical application of kilo-amp class dc HTS magnets. However, the superconducting dynamo investigated here offers an energisation method to enable feasible portable high current HTS magnet systems.

Speaker: Ratu Mataira (Robinson Research Institute, Victoria University of Wellington)

PosterLandscape2.pdf

404 Tue-Af-Po2.16-03 [18]: Design and performance analysis of a dynamo-type HTS flux pump for a 10 kW superconducting generator

In general, superconducting rotating machines have been widely deployed because they have advantages such as smaller volume, lighter weight, and higher efficiency than conventional rotating machines. However, superconducting rotating machines need a cryogenic system to keep field coils in a superconducting state. High temperature superconducting (HTS) flux pumps inject DC current into superconducting field coils without current leads and external power supplies. Therefore, the HTS flux pump removes the need for a current lead, thereby reducing the associated heat load and improving cryogenic efficiency. This paper deals with the design and performance analysis of a dynamo-type HTS flux pump for a 10 kW superconducting generator. The HTS field coil of the 10 kW superconducting generator was designed and fabricated. The induced DC current, output voltage, and dynamic resistance of the flux pump connected to the HTS field coil were estimated using electric circuit equations. They were tested at various rotational speeds and air gaps at 77 K, and the test results were compared with the estimated results. As a result, when the rotational speed of the flux pump increased from 500 rpm to 2500 rpm, the output voltage of the flux pump connected to the HTS field coil increased proportionally. As the air gap of the flux pump increased from 6 mm to 13 mm, the output voltage decreased. The HTS field coil of the designed 10 kW superconducting generator was well excited by the DC current of the flux pump when the rotational speed and air gap were 2500 rpm and 6 mm, respectively. These results will help to apply a flux pump to excite the field coil of a superconducting rotating machine.

Speaker: Mr Gi-Dong Nam (Changwon National University)

MT-26_poster_Tue-Af-Po2.16-03[18]_Nam Gi-Dong.pdf

405 Tue-Af-Po2.16-04 [19]: Experimental and Numerical Characterization of the Contactless Self Current Drived HTS Flux Pump

High temperature superconductor (HTS) magnet working in persistent current mode (PCM) shows great potential in improving the efficiency of electrical applications, since it can offer amazing merits in lowering the energy cost and realizing the compact and light weight design of electrical devices. Unfortunately, the lossless PCM HTS magnet is unavailable due to the non-ignorable joint resistance. The compensation of the losses in the HTS magnet is therefore a must. Tranditional current leads powering method causes severe issues to the cryogenic stability and overall efficiency, in virtue of the heat leakage generated by the current leads spaning from cryogenic temperature to room temperature, it would, to some extent, counteract the advantages brought by the HTS magnet technology. To overcome this issue, in this study, in conjunction with the wireless power transfer approach, we have specially designed a contactless self current drived HTS flux pump, by which, a good sealing of the cryostat could be achieved. To validate this idea, a basic prototype has been demonstrated and experimentally investigated. Moreover, a finite element model is implemented based on COMSOL and solved by 2D T-A formulation. The numerical results could be helpful in understanding the mechanism and also be useful in design optimization of the self current drived HTS flux pump. The insights obtained by this work are intended to offer valuable implications for the future exploratations of low loss HTS flux pump.
Key words: HTS magnet, wireless power transfer, HTS flux pump

Speaker: Pengbo Zhou (Southwest Jiaotong University)

poster_mt26_zpb.pdf

poster_mt26_zpb.pptx

406 Tue-Af-Po2.16-06 [20]: Charging Characteristics of HTS Coils with Various Insulation Materials by Charging of Rotary HTS Flux Pump

High-temperature superconducting (HTS) coils wound without turn-to-turn insulation (NI coils) show excellent electrical and thermal performance compared to HTS coils wound with insulation material (INS coils). However, charging the NI coils using a direct current (DC) power supply have a slower charging time than the INS coils. To overcome this slow charging time, research is underway to charge the NI coils using a flux pump, a DC voltage source, instead of a DC power supply. In this paper, we conducted experiments to compare the charging and discharging characteristics of an NI and INS coils charging by a rotary HTS flux pump. A superconducting circuit consisting of the two coils with the same magnitude of inductance is connected in series. As a result of the experiments, we compare the charging and discharging characteristics when a DC voltage source of the same value is applied to the two coils with a rotary HTS flux pump which is a contactless excitation rotary device.

Speaker: Mr Seunghak Han (Yonsei University)

MT 26 Tue-Af-Po2.16-06 [20].pdf

MT 26 Tue-Af-Po2.16-06 [20].pptx

407 Tue-Af-Po2.16-07 [21]: Presentation withdrawn

408 Tue-Af-Po2.16-08 [22]: Characteristics of a Stationary Flux Pump using Linear Moving Magnetic Fields for an HTS Jointless Coil in Persistent Current Mode

Though an HTS jointless coil can conduct a persistent current without decay, it needs an external power source for the excitation. We have magnetized the HTS jointless coils by field cooling and also have excited by flux pumps with rotating permanent magnets. A stationary flux pump has several comparative advantages over the field cooling or the rotary flux pump.
In this paper, we designed and fabricated the stationary flux pump without mechanical moving parts. The flux pump was made of copper coils and iron cores. The copper coils were excited by an AC power source. The iron core had an air gap and an extended turn from the jointless coil was inserted into the air gap. We excited the HTS jointless coil with the flux pump by changing the width of the air gap and the frequency of AC power source for the copper coils. The results from the charging and discharging tests were compared with the ones of the rotary flux pump.

Speaker: Mr Seyeon Lee (Korea Polytechnic University)

409 Tue-Af-Po2.16-09 [23]: Superconducting transformer for superconducting cable research and development

Abstract

A facility capable of testing superconducting cables with current of tens of kA is essential for the development of large superconducting magnets. A superconducting transformer (SCT) is a suitable choice as a high DC current source for testing superconducting cables. In this work, we will present our experimental results of a SCT that was originally developed by Lawrence Berkeley National Laboratory to reach a maximum output current of 50 kA. The SCT is characterized first at 4.2 K in zero magnetic field. Its behaviors during a sample quench at different current levels is studied. We will also present its performances in high magnetic field measured on a SC cable in a 12 T split magnet at the National High Magnetic Field Laboratory.

Acknowledgement

We thank Mr. Eric Stiers for helps on electronic control. This work is supported by the user collaboration grant program (UCGP of the NHMFL which is supported by NSF through NSF-DMR-1157490 and 1644779, and the State of Florida.

Speaker: Hui Yu (National High Magnetic Field Laboratory)

Superconducting Transformer for Superconducting Cable Testing up to 45 kA_Hui Yu.pdf

Superconducting Transformer for Superconducting Cable Testing up to 45 kA_Hui Yu.pptx

410 Tue-Af-Po2.16-10 [24]: Transient Analysis of AC Power System for JT-60SA Superconducting Magnets

JT-60SA is the second largest tokamak device constructed in the world, which is being implemented aiming to start the first experiment in 2020. One of the most important features of JT-60SA is to have superconducting magnets for long-pulsed plasma discharge (100 s flattop). JT-60SA has ten of poloidal field (PF) coils for inductive current drive and shape control of a plasma. Their stored magnetic energy is up to 1 GJ in total. The current for each coil is individually supplied by thyristor-based AC/DC converters, which require a large amount of AC power more than 250 MVA. In JT-60SA, all the PF coils are powered by a dedicated motor-generator called H-MG (400 MVA/2.6 GJ). In addition, from the second research phase, some additional plasma heating devices, such as neutral beam injection (NBI), are planned to be connected to the motor-generator in parallel to the AC/DC converters for PF coils.
In the AC power system, one of the key issues is unacceptable voltage distortion. In the case of emergency event such as magnet quench, all the AC/DC converters stop and the magnetic energy is discharged immediately using Quench Protection Circuits (QPCs) to protect the superconducting coils. This protective action leads to large and rapid load change and thus an overvoltage in AC side. In addition, plasma disruption also causes rapid load reduction since NBI must be shutdown to avoid the damage of plasma facing components inside the vacuum vessel. In such a case, however, AC/DC converters should be operated properly for normal demagnetization to suppress AC loses of superconducting magnets.
This presentation focuses on transient analysis using an integrated circuit simulation model and optimization of the AC power system at the emergency events.

Speaker: Mr Shoichi Hatakeyama (National Institutes for Quantum and Radiological Science and Technology)

MT-26_poster_r1.pdf

MT-26_poster_r1.pptx

411 Tue-Af-Po2.16-11 [25]: Design of a Resistive Magnet Power Supply Based on Three-Level Buck Converters

Water-cooled resistive high-field research magnets require a high power supply with an extremely high current stability, and a low current ripple and noise. The conventional resistive magnet power supply uses thyristor rectifiers, followed by a passive filter and an active filter in series to reduce the voltage ripple. This Paper describes a new circuit topology design of the resistive magnet power supply, which consists of an uncontrolled rectifier bridge and a three-level buck converter in series instead of the conventional thyristor rectifier. The three-level buck converter works at a higher switching frequency, which can greatly reduce the cost, volume and weight of the filter. According to simulation and analysis results, it is seen that the three-level buck converter structure provides a lower voltage and current ripple than the conventional thyristor rectifiers, reduces the voltage stress of the power electronic devices. Beside, without power factor correction devices, this new design can achieve a higher power factor.

Speaker: Mr Can Wang (Hefei Institutes of Physical Science, Chinese Academy of Scienc)

Tue-Af-Po2.16-11 [25]_Can Wang.pdf

412 Tue-Af-Po2.16-12 [26]: Improvement of the performance of Flat-top Pulsed High Magnetic Field Facility based on battery-bank power supply

The high stability flat-top pulsed magnetic field (FTPMF) is strongly needed for some scientific researches such as nuclear magnetic resonance (NMR) and specific heat measurement. The high stability FTPMF Facility based on the battery power supply with a linear bypass circuit had been built at Wuhan National High Magnetic Field Center the in 2018. The linear bypass circuit mainly consists of insulated-gate bipolar transistors (IGBT) operating in the active region and power resistor. The current of bypass circuit can be adjusted by the gate voltage of IGBTs to achieve the continuously regulation of the voltage division ratio between divider resistor and magnet. As a result, the joule effect of the magnet can be offset and the magnet current can maintain stability with feedback control. With two IGBT FZ3600R17KE3-B2 ($1700 each), the FTPMF at 23.370 T for 100 ms with the stability of 64.2 ppm had been achieved. However, the terminal voltage of the IGBT in this facility is high due to operate in the active region, which limits its through-current capability. With the magnetic strength increase the through-current capability of IGBT will decrease, which means the more IGBTs are needed. In this paper, a current injection equipment is proposed to reduce the terminal voltage of the IGBTs by injecting current to the power resistor. In this way, the through-current capability of IGBT will be enhanced greatly and the regulation scope of the FTPMF system will be expanded with the same number of IGBT.

Speakers: Dr Shaozhe Zhang (Wuhan National High Magnetic Field Center,Huazhong University of Science and Technology), Zhenglei Wang (Wuhan National High Magnetic Field Center,Huazhong University of Science and Technology)

Tue-Af-Po2.16-12.pdf

413 Tue-Af-Po2.16-13 [27]: A new control strategy to improve the performance of the voltage source converter of new high power magnet power supply

In the past years, the thyristor converter technology has been adopted in the Tokamak coil power supply, mainly because of current carrying capacity and overload capability of thyristor with high power level. However, thyristor converter technology also has inherent defects, including poor dynamic control, low power factor, and producing a large number of reactive power and harmonics that damage to the power grid. With the development of semiconductor power device technology, the power level of full-controllable devices has been improved. Therefore, a new magnet power supply based on full-controllable devices is proposed. The new magnet power supply is composed of voltage source converter (VSC) and H-bridge. In this paper, a new control strategy is proposed to improve the performance of the voltage source converter. The new control strategy is to introduce the neutral point balance factor into the double closed-loop control system to achieve the DC side voltage stability and neutral point potential balance of the whole magnet power supply. Based on the theoretical analysis, the voltage source converter achieves the goal of high power factor and low harmonic operation while realizing the output target voltage and current, reduces the impact on the power grid, and improves the compatibility with the power grid. Finally, the theoretical analysis and the effectiveness of the control strategy are well-verified by Hardware-in-the-loop simulations on the RTLAB.

Speaker: Dr Zhenshang Wang (1.Institute of Plasma Physics, Chinese Academy of Sciences,Hefei 230031,P.R.China; 2.University of Science and Technology of China,Hefei 230026,P.R.China)

Tue-Af-Po2.17 - NbTi Accelerator Magnets I

Conveners: Mr Etienne Rochepault (CEA Paris-Saclay ), Gerard Willering (CERN)

414 Tue-Af-Po2.17-04 [28]: Presentation withdrawn

Speaker: MT26 Conference Organizer (Centennial Conferences)

415 Tue-Af-Po2.17-05 [29]: Preliminary Test Results of the First of Series Multiplet for the Super-FRS at FAIR

The Superconducting FRagment Separator (Super-FRS) at FAIR being built in Darmstadt, Germany, foresees a significant increase of momentum acceptance and angular acceptance of the secondary particle beams compared to the current facility of Fragment Separator (FRS). This requires dipoles and multipole magnets with a large aperture. Consequently, superferric magnets will be installed except for high radiation area. The multipole magnets are arranged in a common cryostat and this cryogenic module is called a multiplet, which is the focus of this paper. In total, 32 multiplets need to be constructed. However, they will be configured differently in order to be adapted to the requirement of beam optics. This paper presents design and preliminary test results of the first of series (FoS) multiplet containing one quadrupole magnet and one sextupole magnet. The two magnets are assembled together as a cold mass column and will be cooled in a He bath by up-to 800 liters of liquid helium, while the beam pipe remains at room temperature. The features of the magnets are a warm bore radius of 192 mm, vacuum impregnated racetrack coils made of Nb-Ti conductor and a maximum gradient of 10 T/m for the quadrupole magnet and 40 T/m2 for the sextupole magnet, respectively. The required magnetic field quality of the quadrupole magnet was reached by introducing saturation control holes despite of its strong iron saturation. The design pressure of the He vessel is 20 bars absolute. Its design, material selection, and welding process were thoroughly verified and a final pressure test was performed at 22 bars. The construction of the FoS multiplet was completed and the site acceptance test is now underway at a CERN cryogenic magnet test facility in the frame of a GSI/CERN collaboration work.

Speaker: Hans Guenter Mueller (GSI)

Tue-Af-Po.2.17-05.pdf

416 Tue-Af-Po2.17-06 [30]: Industrial production of superconducting magnets for the FAIR SIS100 accelerator

For the FAIR project`s SIS100 Synchrotron a series of 110 fast ramped dipoles is currently built and in addition a total of 83 superconducting quadrupole doublet modules (QDM) are needed for this accelerator.
An intense measurement program of the first of series (FoS) dipole revealed excellent behavior with respect to, e.g., quench performance and AC losses. With an optimized fabrication technique, the geometrical accuracy was improved to provide a highly homogeneous field and the series production started in 2016.
This document reports about the series manufacturing process of the 110 dipoles. NOELL describes the crucial steps of the series manufacturing and assembly processes. In addition a brief outlook on the integration of the SIS100 QDMs is given.

Speaker: Wolfgang Walter (Babcock Noell GmbH)

417 Tue-Af-Po2.17-07 [31]: Mock-up developments for the superferric dipoles of the Super-FRS of FAIR

The Facility for Antiproton and Ion Research (FAIR), currently being built in Darmstadt (Germany), needs 21 standard superferric dipoles for its Superconducting FRagment Separator (Super-FRS). The dipoles manufacturing contract has been awarded to Elytt (Spain) in Spring 2017 and CEA Paris-Saclay (Commissariat à l’Energie Atomique) is overseeing the design and manufacturing activities in the context of the in-kind contribution of France to the FAIR project. The design activities are completed and the manufacturing of the First-of-Series (FoS) will be launched by Elytt after it has completed all the mock-up activities which will validate each key manufacturing process. These superferric dipoles have cold NbTi trapezoidal coils (4.5 K) and warm iron (300 K), and several small scale to full-scale mock-ups were developed and tested by Elytt. We develop in this paper, the mechanical tests performed on samples of conductor and impregnated stack of conductors, the results of the winding tests, the tests of the splices required to put the two coils in series and the tests carried out on the full-scale Helium vessel mock-up made of stainless steel.

Speaker: Arnaud Madur (CEA Saclay)

SFRS-MT26-D3-poster-01-main-v2.pdf

418 Tue-Af-Po2.17-09 [32]: Preparation of the superconducting magnet string test for the SIS100 synchrotron

The new international accelerator facility FAIR (Facility for Antiproton and Ion Research) is currently under construction in Darmstadt, Germany. The core component of the complex is the heavy ion synchrotron SIS100 which utilises 417 superconducting magnets assembled in 191 cryo-magnetic modules. The SIS100 machine is supplied with two phase helium via 52 local cryogenic components. All cryo-modules are tested at ambient (300 K) and at operating (4.5 K) conditions during comprehensive acceptance tests either at contractor’s or at GSI side. Besides the testing of standalone modules, the SIS100 magnet string will be assembled and tested at GSI. The string will be built-up of a number of the main cryo-magnetic components such as dipole- and quadrupole modules and the most crucial local cryogenic parts, such as a by-pass line piece. A wide spectrum of tests will be performed in order to evaluate the interaction of the main components during cool down, warming up and during powering at operational conditions. The testing program includes i.a. mechanical and electrical integrity tests. Special attention will be brought to the functionality of the ultra-high vacuum system and its performance. Moreover, the quench detection system and the power converter control will be verified on the string. Besides the tests relevant to the SIS100 operation, the string will provide an ideal scenario to develop the processes for the future machine assembly, i.e. sc-circuits interconnection, process pipes welding. In this work the preparation plan of the string test is presented.

Speaker: Patricia Aguar Bartolome (GSI GSI Helmholtzzentrum für Schwerionenforschung GmbH)

Tue-Af-Po2.17-09.pdf

Tue-Af-Po2.18 - NbTi Accelerator Magnets II

Conveners: Dr Tatsushi Nakamoto (High Energy Accelerator Research Organization, KEK), Thomas Strauss (FNAL)

419 Tue-Af-Po2.18-01 [33]: Magnetic field design of a full-scale prototype of the HL-LHC beam separation dipole with a correction of mechanical deformation

The beam separation dipole, MBXF, is being prepared by the High Energy Accelerator Research Organization, KEK, for the high luminosity LHC (HL-LHC) upgrade. The new magnet is designed to generate a central field of 5.6 T at the nominal operating conditions of 12.05 kA and 1.9 K. From the past design study, the magnet is designed as a single layer coil wound with a 15 mm wide NbTi/Cu Rutherford cable. According to requirements from CERN, the coil aperture is fixed to 150 mm so that the size matches those of inner triples, and this requires the magnet to withstand a large electromagnetic force.
So far we have tested the two models and a re-assembled magnet. The test of the first model shows the pre-stress of the coil was not at satisfactory level. So, we decided to re-assemble this magnet to increase the pre-stress up to 100 MPa which is 35 MPa higher than the first one. The re-assembled magnet then showed had a good training performance. From the experiences of the first model and its re-assembled magnet, we fabricated the second model where the pre-stress in the straight section was further increased up to 115 MPa. Although it had a good training performance as expected, we observed the measured b3 is 16-18 units higher than the calculation, the reason of which is presumably due to the coil deformation triggered by the large pre-stress. Therefore, we decided to modify the electromagnetic design of MBXF so that we can cancel out the increase of b3 even the coil is deformed by the large pre-stress. In this paper, we report results from our design study and a new cross section of MBXF.

Speaker: Kento Suzuki (High Energy Accelerator Research Organization )

mt26_xsec_v2.pdf

420 Tue-Af-Po2.18-02 [34]: Magnetic Field Measurement of first series twin aperture orbit correctors for the HL-LHC Upgrade

The Large Hadron Collider (LHC) upgrade, called High Luminosity LHC (HL-LHC) is planned for the next decade. A set of twin aperture beam orbit correctors positioned on the approaches to the ATLAS & CMS experiments will be development. The orbit corrector based on Canted Cosine Theta (CCT) design to achieve 5 Tm field integral and multipoles lower than 10 units in the twin aperture. Tow institutes (IHEP, IMP) and one company (WST) in China will work on the magnet R&D and series production. IMP in charge of the performance test at 4.2 K including field strength and field quality. This paper presents the results of the magnetic field measurements of the first series magnet by a rotating coil probe.

Speaker: Mr Wenjie Yang (University of Chinese Academy of Sciences)

421 Tue-Af-Po2.18-03 [35]: HL-LHC D2 Short model recombination dipole cold test results and analysis

The new D2 recombination superconducting dipole is a key two-in-one NbTi magnet with a 105 mm bore aperture for the LHC high luminosity upgrade project (HL-LHC) expected in operation from 2024. A short model magnet of 1.6 m magnetic length has been designed by INFN (Genova), built by Ansaldo Superconductors Group, and cold tested at CERN within a INFN-CERN collaboration framework. This model magnet features novel magnetic and mechanical design elements, which include the cancellation of unwanted cross-talk field multipoles through asymmetric coils, aluminium alloy collar pack preloading rings and a peculiar axial structure design. The future series of four 8.5 m long full-length dipole magnets shall be installed on both sides of ATLAS and CMS interaction points with an integral field of 35 T.m and 4.5 T bore magnetic field
This paper shall present the first power test mechanical results including training, protection, and field quality. Short model results will give a relevant feedback on the prototype construction and the series production.

Speaker: Arnaud Pascal Foussat (CERN)

MT26_2019_poster_D2.pdf

422 Tue-Af-Po2.18-04 [36]: Design and performance of the quench protection heater for the HL-LHC beam separation dipole

The LHC beam separation dipoles plans to be replaced for the high luminosity LHC (HL-LHC) upgrade. The new separation dipole, MBXF, is based on the Nb-Ti superconductor, and is designed to generate 35 Tm at the nominal operating conditions of 12.05 kA and 1.9 K. The magnet has a stored energy of 0.34 MJ/m, and all the energy needs to be extracted only by quench protection heaters before the hot spot temperature reaches its practical limit of 300 K.
The first heater is made of 25 um thick by 15 mm wide stainless steel (SUS), and its total length is adjusted to that of the MBXF model (2 m). An inrush current of ~150A is provided by the 7.05 mF capacitive power supply. The heater test was conducted with the first MBXF model and we found that the single strip-line heater was not capable of protecting the magnet for the nominal operation. Therefore, we conducted a design study for a new protection heater using our thermal simulation code.
The new heater is a composite of same materials as used in the first heater while the length and position of the SUS strip is optimized so that the normal propagation zone is developed effectively. The heaters were equipped with the second model magnet, and the full energy discharge was tested in order to check the performance. The result showed that the magnet current was successfully dumped and the new heater fulfills the protection requirements on the MBXF. In this paper, we summarize the results from the full energy dump test for the second model, and give prospect for the full-scale production magnet.

Speaker: Kento Suzuki

mt26_qph_v2.pdf

423 Tue-Af-Po2.18-05 [37]: Design of radiation hard spare units for the orbit corrector dipoles of LHC

In the Large Hadron Collider (LHC) at CERN, it is expected that 35 out of the 122 MCBC and MCBY orbit corrector dipoles will receive up to 20 MGy of gamma radiation over the High-Luminosity (HL)-LHC lifetime. Since these magnets were not designed to withstand such high gamma doses, new MCBC and MCBY magnets have to be designed and produced using radiation hard impregnation insulation and materials.
The MCBC and MCBY magnets are located close to the interaction points, are operated at about 60% on the load line and are epoxy impregnated. The MCBC (resp. MCBY) magnet is a dipole with 3.1 T (resp. 2.5 T) central magnetic field and 56 mm (resp. 70 mm) aperture diameter. It is operated at 1.9 K (resp. 4.3 K) and uses 14 (resp. 15) rectangular Nb-Ti wires insulated with PVA (polyvinyl acetate) enamel which are glued together in a Ribbon cable. Over the HL-LHC lifetime, it is expected to receive up to 20 MGy (resp. up to 5 MGy) of gamma radiation.
In this paper, we describe the new design and technologies that will be used for the production of new radiation hard units of MCBC and MCBY magnets. These new solutions include for example the selection of polyimide enamel instead of PVA enamel as insulator or the use of the MCBY coils for both MCBC and MCBY magnets in order to reduce their manufacturing cost as well as the gamma dose seen by the MCBC magnet. Indeed, since the new MCBC magnet will use a coil with larger bore, a radiation shield can be placed between the aperture and the inner part of the coil.

Speaker: Dr Alexandre Mehdi Louzguiti (CERN)

DesignofRadiationHardSpareUnitsfortheOrbitCorrectorDipolesofLHC_v1.pdf

424 Tue-Af-Po2.18-06 [38]: Fabrication and results of the first Round Coil Superferric Magnet at LASA

The LASA Laboratory (INFN, Milan) is working in the High Luminosity LHC program for developing, in collaboration with CERN, 6 different types of High Order corrector magnets. In this framework, in parallel with a conventional design of superferric magnets with LTS conductor, the LASA Lab. is focusing on the research of novel superconducting materials which may have application in particle accelerator magnets. To this purpose LASA Lab. is developing a new type of superferric magnet suitable to arbitrary multipole order, called Round Coil Superferric Magnets (RCSM). The iron yoke shaped with arbitrary poles is able to create the desired harmonic component using only one single round coil with a large bending radius which is suitable for very strain-sensitive superconductors. The electromagnetic design of a sextupole configuration of the magnet and the production of the first superconducting MgB$_2$ round coil prototype have been already presented. In this paper, we expose the optimization of the iron yoke and polar expansions assembly of the first magnet. The results of the whole magnet powering test are described in detail and the analysis of the magnetic performances are compared with those of classical superferric correctors.

Speaker: Samuele Mariotto (University of Milan - INFN Milan)

MgB2MT262019.pdf

425 Tue-Af-Po2.18-08 [39]: Analysis of Interdependent multipole field pattern and complement dipole field quality

This paper presents an analytical method that fines the mutual influence of the magnetic field in a dipole magnet. A vacuum beam tube is in thermal contact with a cryogenic cooling pipe for a high-quality vacuum. These two different geometric components have different eddy current profiles. And the corresponding magnetic fields disturb the operation field quality. The cooling pipe in an optimal position shows the opposite polarity with the same magnitude of one multipole field component corresponding to that of the beam tube. The present geometric field analysis identifies the pattern of the multipole field and the cooling pipe position. The eddy current in the optimal conductor geometry is able to complement the dipole field quality.

Speaker: Dr Seong Yeub Shim (GSI)

MT26 poster SYSHIM.pdf

426 Tue-Af-Po2.18-09 [40]: The training test research of high stress superconducting magnet for 200 MeV superconducting cyclotron

Based on the collaboration of Institute of Plasma Physics Chinese Academy of Sciences (ASIPP) and Russia Joint Institute for Nuclear Research (JINR) for proton therapy, a 200 MeV compact superconducting proton cyclotron project (SC200 project) has been launched at ASIPP since 2016. The superconducting magnet is the most critical and challenging subsystem for the cyclotron to provide ~3 T magnetic field of central region and enough flutter field to focus on the proton beam. The inner radius of the superconducting coil is about 0.7 m and total stored magnetic field is ~ 3.4 MJ. The superconducting magnet has been manufactured and tested in ASIPP. This paper pays attention to the coil ‘training’ effect which associated with the use of epoxy resin impregnates. The magnet was performed the quench training of twelve times and the current raise to 168.7 A. The axial and hoops mechanical stress on the coil has been analysis. The test process will be outlined in detail, the ‘training’ results will be discussed in the paper.

Speakers: Chunlong Zou (Institute of Plasma Physics, Chinese Academy of Sciences), Dr Kaizhong Ding (Institute of Plasma Physics, Chinese Academy of Sciences), Shuangsong Du (ASIPP)

427 Tue-Af-Po2.18-10 [41]: Optimization Design of CiADS Superconducting Solenoid

Accelerator Driven System (ADS) is recognized as one of the most efficient ways to transmute minor-actinides. China initiative Accelerator Driven System (CiADS) project as ADS demonstration with 500 MeV has been approved in 2015. Three type superconducting focusing solenoids are used to focus and correct beam in CiADS superconducting LINAC. The focusing solenoid includes a solenoid coil and a pair of steering dipoles. It is required to produce high focus strength and low stray field near superconducting RF cavity in a limited space according to beam physics requirements. It is difficult to design the solenoid using a commercial magnetic field simulation program. Self-developed Solenoid optimization code base on OpenMDAO toolkit was used to design the solenoid. Nonlinear optimization method was used for the solenoid coils to meet the requirement of focusing strength and stray field with minimized solenoid volume. This paper presented the optimization design of the solenoid.

Speakers: Ms Tongjun Yang (Institute of Modern Physics, Chinese Academy of Sciences), Wei Wu (Institute of Modern Physics, Chinese Academy of Sciences)

Tue-Af-Po2.19 - Losses in Conductors and Coils II

Conveners: Francesco Grilli (Karlsruhe Institute of Technology), Mike Sumption (The Ohio State University)

428 Tue-Af-Po2.19-01 [42]: Instantaneous AC Loss Measurement of HTS Coil

AC loss is one of the important considerations in the design and operation of high temperature superconducting (HTS) devices. Traditional method to measure AC loss generated in HTS coil is to measure the coil voltage’s resistive component by using a lock-in amplifier. This method has several limitations during application. In order to solve these problems, integration method and energy conservation theorem are used in this paper to measure HTS coil’s AC loss. In this method, voltage and current of HTS coil are simultaneously acquired by data acquisition device and converted to digital signals. And then these data are processed in a computer to get the coil’s instantaneous AC loss. Based on this method, a measurement platform is constructed. Details of the platform and algorithm of data processing have been introduced in this paper. Also model for calculating the AC loss of superconducting coil is built with the finite element software COMSOL. By comparing the measurement and calculating results, it is proved that this method can be applied to effectively measure the HTS coil’s instantaneous AC loss.

Speaker: Kai Zhu (Huazhong University of Science and Technology)

429 Tue-Af-Po2.19-02 [43]: Experimental investigation on AC loss characteristics under HTS cable electromagnetic conditions

In a high-temperature superconducting (HTS) multi-layer AC cable, the HTS tapes of one layer are twisted cylindrically, an AC transport current is provided, and the cable is exposed to an AC magnetic field produced by the other layers. The magnetic field consists of a circumferential magnetic field and a longitudinal magnetic field. The circumferential magnetic field is produced by a transport current in the inner layer. The longitudinal magnetic field is produced by a transport current in the twisted outer layers. In a previous study, we measured the AC losses in each layer of a three-layer twisted HTS cable using a calorimetric method. This cable could change the AC transport current balance and enabled the control of the circumferential and longitudinal magnetic fields. The magnetic field of each layer behaved as an external magnetic field for other layers. The amplitude and direction of the magnetic field influence the AC loss characteristics; when the magnetic field is parallel to the axis of the HTS tapes, the AC losses are smaller than when it is exposed in other directions.
In this study, we assumed one layer of the HTS cable and measured AC losses in twisted cylindrical samples with an AC transport current and external circumferential and longitudinal magnetic fields. For the circumferential magnetic field, we placed non-twisted stacked HTS tapes cylindrically with a transport AC current. The longitudinal magnetic field was generated by a capper solenoid coil. We could control the amplitude and direction of the composition magnetic field with the balance. We measured AC losses using the calorimetric method, similar to our previous study. We investigated the influence of the twist pitch, amplitude, and direction of the magnetic field on the AC loss characteristics.

Speaker: Prof. Jun Ogawa (Niigata University)

190917MT_cable_Poster_final.pdf

430 Tue-Af-Po2.19-03 [44]: Research on Driving Coil with Coupling Cooling Method in Electromagnetic Forming

The long-life driving coil is the prerequisite for Electromagnetic forming industrial application, so far, the temperature rise is one of the major factors that restraint its working life. This paper proposes a new coupling cooling method of driving coil by placing extra cooling coil with timing control system on the other side, which can reduce the Joule heating and temperature rise of the system. In this study, a finite element simulation model of Electrical circuit-Electromagnetic field-Thermal coupling has been established, then the temperature rise of driving coil by changing the structural parameters of the cooling coil: number of turns, cross-sectional area and electrical conductivity have been analysed. The simulation results show that it is effective to reduce the Joule heating in the driving coil and the average temperature rise was reduced by 13 degrees, fell 22.8% in this new method.

Speaker: Li Qiu (China Three Gorges University)

431 Tue-Af-Po2.19-04 [45]: Presentation withdrawn

432 Tue-Af-Po2.19-05 [46]: Test Results of Quench-back Management Due to Fast Decaying Current Induced AC Losses in SHMS Superconducting Magnet at Jefferson Lab

The Super High Momentum Spectrometer (SHMS) of Hall C, part of the recent 12 GeV accelerator Upgrade at Jefferson Lab, was successfully commissioned in 2017. During pre-commissioning, fast dumps of the SHMS Q2/Q3 quadrupole and Dipole superconducting magnets experienced some level of operational difficulty. Measurements and analyses demonstrate that the fast discharge caused fast current decay, which resulted in substantial ac loss in the conductor and subsequently triggered a quench-back effect. The details of the measurements and analyses have been reported previously. This paper will focus on the test results of the magnets with recommended modifications to the respective dump resistors. The physical test and measurement setup will be the same as for the previous measurements except the sampling rates. The sampling rates of the digital scopes will be changed to 250 Hz for all magnets from 1 kHz for the Q2/3 magnet and 500 Hz for the Dipole because the recommended dump resistors have low resistance values—producing slow decaying currents. The test results will be compared with the calculations. The detailed analysis and measurement techniques used during this investigation could lead to the development of a fine-tuned ac loss computational procedure for future similar projects.

Speaker: Dr Eric Sun (Jefferson Lab)

MT26_2019_Sun_MT26-Tue-Af-Po2.19-05.pdf

MT26_2019_Sun_MT26-Tue-Af-Po2.19-05.pptx

433 Tue-Af-Po2.19-06 [47]: Calculation of Iron Losses for Soft Magnetic Materials Under Sinusoidal Pulse Width Modulation (SPWM)

Copper losses and iron losses are the two most significant losses in electrical machines. The iron loss is a large portion of the total losses, and it mainly influences efficiency. The copper losses are relatively easy to calculate and it will be negligible if current is too small; on the other hand, the calculation methods of iron losses are more complicated than the copper loss calculation. If no measurement data are provided for materials, approximation-based methods have to be used. The famous empirical equation is Steinmetz equation, but it only works for the sinusoidal and limits frequency range. According to research data, improved generalized Steinmetz equation (IGSE) give highly accurate results among the Steinmetz-based methods for non-sinusoidal. Outside the Steinmetz-based methods, loss surface approach also provides good results which can be used for materials if no data sheet is available and change the material’s characteristics due to the cutting process. Nowadays a widely used of power electronics devices and most of the electric machines are fed with voltage source inverters (VSI) with SPWM schemes, which can cause extra core losses due to the presence of harmonic components. In this research, we use the different modulation ratio and carrier ratio of SPWM as excitation waveform to excite the ring simples of soft magnetic composite (SMC) and silicon steel materials. We also take fast Fourier transform (FFT) as a tool to analyze total harmonic distortion (THD) of different SPWM. Even, the calculation results of IGSE, loss surface approach and how THD influence on the iron loss calculation are compared and analyzed under the different ratio of SPWM. Due to the results, the modulation ratio has a more significant effect on iron losses than the carrier ratio and THD also play essential roles according to the iron losses analysis.

Speaker: Mr Htutzaw Hein (State Key Laboratory of Reliability and intelligence of Electrical Equipment, Hebei University of Technology, 300130 Tianjin, China)

434 Tue-Af-Po2.19-07 [48]: A Theoretical Investigation on the AC Loss Estimation Method for Fusion Magnet

During operation, AC loss of central solenoid (CS) coils can be quite significant. From cryogenic point of view, CS coils, made of cable-in-conduit conductors (CICC’s), can be regard as porous pipes. A common way to estimate the heat generated by AC loss is from a difference in the enthalpy flow between the inlet and outlet. In actual cases, offsets in the enthalpy flow difference commonly observed, which does not seem to stay constant during operation. For a simplified cryogenic circuit, which contains key ingredients of actual system, we investigate this background enthalpy flow in detail, by using FLOWER code. The circuit contains a by-pass line and a pressure-relief valve. The work done passing through the porous media, CICC, has been carefully removed. It was shown that for the semi-closed test circuit, the enthalpy flow is accumulated in the outlet side in the form of cryogen density increase. The accumulated enthalpy only can be removed by pressure relief and due to overall mass imbalance, offsets in the enthalpy flow difference vary significantly. A way to minimized AC loss estimation error is further discussed.

Speaker: Sangjun Oh (NFRI)

435 Tue-Af-Po2.19-08 [49]: Effect of Dynamic Resistance on AC loss in a Conductor-on-round-core Cable

Abstract—Conductor-on-round-core (CORC) cable, which is helically wounded by YBCO coated conductors, has become a promising candidate conductor for high temperature superconducting (HTS) applications, such as superconducting magnets and electric machines. Understanding the mechanism and magnitude of AC loss is extremely critical for the design of CORC cable. Dynamic resistance has been observed in HTS coated conductors when they transport DC current and expose to an AC magnetic field. AC loss in this state includes the magnetization loss and the dissipative loss generated by dynamic resistance.
In this paper, a 3D finite element method based on T-A formulation is bulit to calculate the dynamic resistance and AC loss in a CORC cable, which is carrying a constant DC current under an AC magnetic field up to 100 mT. Subsequently, we investigate the relationship between dynamic resistance and the magnitude of applied current and magnetic field. Then how the frequency of AC magnetic field influences the dynamic resistance is analyzed. The effect of interaction between dynamic resistance and AC external field on AC loss is also studied. Finally, the characteristics of dynamic resistance and AC loss mentioned above are all experimented to compare with the modeling. Dynamic resistance is generated when the magnitude of external field exceeds the threshold and increases with the continue increasing of the magnitude of AC external field. The result shows that there is a slight dependence of dynamic resistance on the frequency of AC magnetic field when the applied current is much less than the critical current. AC loss reaches to the maximum at threshold field and then decreases with the increasing of background field.
Index terms——CORC cable, Dynamic resistance, AC loss

Speakers: Liu Rujing, Yang Wenjiang

Rujing Liu—MT26th(2).pdf

Rujing Liu—MT26th(2).pptx

436 Tue-Af-Po2.19-11 [50]: Self-field AC loss measurement of a four-tape HTS stack using Fiber Bragg Grating sensors

Understanding AC loss in High Temperature Superconductor (HTS) magnets is critical to application. The common methods for AC loss measurement are electrical and calorimetric measurements. It is generally accepted that calorimetric techniques are superior to electrical methods when there is a phase difference between the transport current and external magnetic field. A common challenge in calorimetric measurements is the interaction of an electric thermal sensor with the magnetic field; it has been proposed that an optical fiber sensor that is immune to EMI can overcome this challenge. Other researchers have demonstrated the feasibility of the calorimetric method measurement based on Fiber Bragg Grating (FBG) sensors on single HTS wire.

In this work, we demonstrate the calorimetric method measurement for self-field AC losses on a four-tape HTS stack using FBG sensors. Several types of cryogenic FBG temperature sensors were selected for the thermal measurement to study the available optimized loss sensitivity. These measurements were carried out at 77 K through conduction cooling in a cryostat. A heater was used to calibrate AC loss values in the measurement. The effect of bonding on the AC loss sensitivity was analyzed by comparing the fully bonded and single-end-bonded sensors. The magnetic strain effect on the measurement was also evaluated using fully bonded FBG sensors through comparison of the experimental and theoretical results. The measured loss results were verified through comparison with the FEM simulation results using H-formulation and electrical measurements of AC-loss. The results in our paper shows that the calorimetric method based on FBG sensor can be used for the AC loss measurement of the four-tape HTS stack, which provides the possibility of ac loss measurement on HTS coils.

Speaker: Mr Yanchao Liu (Beijing Jiaotong University)

Tue-Af-Po2.19-11.pdf

437 Tue-Af-Po2.19-12 [51]: Reduction of ac loss in HTS coils of superferric magnets for rapid cycling synchrotrons by changing iron yoke geometry

We have been studying the potential of energy consumption reduction in rapid cycling synchrotrons (RCSs) by using superferric magnets with high temperature superconductor (HTS) coils. In our previous research, we developed a three-dimensional electromagnetic field analysis model for superferric magnets, and analyses were conducted on superferric magnets in several kinds of RCSs designed for accelerator-driven nuclear transmutation systems. Analysis results of the designed superferric magnets indicate that ac loss is concentrated on the coil ends that are not surrounded by iron yoke.
In this paper, we aim to reduce the ac loss in HTS coils of the superferric magnets designed in previous research by changing their iron yoke geometries. We assumed that the large ac losses in coil ends are caused by leaked magnetic flux density at coil ends. Then, effects of several ac loss reduction approaches will be studied by numerical analyses based on this assumption. For example, using thicker iron yoke may reduce the ac losses at coil ends, because thicker iron yoke has more margin to saturation and therefore leaked magnetic flux will be less. Also, adding field clamps to coil ends is another possible approach to ac loss reduction, as it can guide magnetic fluxes and reduce the magnetic flux density at coil ends. When changing geometry of iron yoke, we will make sure that the changed magnets satisfy the requirements of the RCS (magnetic flux density, field uniformity, magnet size, etc.).

This work was supported in part by the Ministry of Education, Culture, Sports, Science and Technology under the Innovative Nuclear Research and Development Program.

Speaker: Yang Li (Kyoto University)

The-Af-Po2.19-12[51].pdf

Tue-Af-Po2.20 - Motors VII

Conveners: Dr Anna Kario (GSI Helmholtzzentrum für Schwerionenforschung GmbH), Takanobu Kiss (Kyushu University)

438 Tue-Af-Po2.20-01 [54]: An Optimal Design to Prevent Demagnetization of Dy-free Magnet for a Traction Motor

Neodymium (Nd) magnets have been applied for a traction motor owing to its considerable maximum energy product. In addition, heavy rare earth elements such as Dysprosium (Dy) are added to the Nd magnets for withstanding severe conditions of a traction motor that includes high temperature and strong demagnetizing field. However, the employment of Dy causes critical issues regarding environmental problems and price fluctuations due to unstable supply.
To resolve the issues, application of Dy-free magnets, which eliminate the Dy content of magnets, have been dealt with recently. Especially, an optimal design of motor shapes has been studied to prevent irreversible demagnetization due to a low coercivity of the Dy-free magnet. Nevertheless, these studies should be supplemented since partial demagnetization on diverse operating points has not been considered thoroughly.
Meanwhile, an optimal design for preventing demagnetization should be based on finite element analysis (FEA) to improve the reliability of the analysis. However, excessive computation cost is required for FEA-based demagnetization analysis on diverse operating points. To overcome the deficiency, optimization algorithms is requisite to derive an optimal solution within the limited computation cost.
This paper demonstrates an optimal design to prevent demagnetization of Dy-free magnets applied for a traction motor. The demagnetization of Dy-free magnets including partial demagnetization were considered on diverse operating points. Furthermore, in order to derive the optimal solution among numerous candidates of variables, an optimal design was performed applying a novel optimization algorithm, which is intelligent multi-start mesh adaptive direct search based on kernel support vector machine.

Speakers: Ho-Chang Jung (Korea Automotive Technology Institute), Dr Dongsu Lee (University of Illinois at Urbana-Champaign)

Tue-Af-Po2.20-01 [54] An Optimal Design to Prevent Demagnetization of Dy-free Magnet for a Traction Motor.pdf

439 Tue-Af-Po2.20-03 [55]: Low-Iron-Loss Design of a Flux-Modulated Motor Considering Air-Gap Harmonics

As a promising member of permanent-magnet brushless motors, flux-modulated permanent-magnet (FMPM) motors have aroused considerable attentions due to the outstanding low-speed large-torque characteristics. With the increasing demands of high quality PM motor, the high efficiency transmission in motor operation is one of the important performance evaluation indexes of motor. And then, the analysis, calculation and reduction of the motor losses have been one of the research subjects for the FMPM motors, such as the iron loss. In previous studies, the reduction of iron loss is often realized by optimizing the topologies of stator and rotor or improving the winding configuration. Yet, it is worth noting that, to the FMPM motors, the abundant harmonics often exist in the air-gap due to the flux modulation effect. So it can be inferred that the low-loss design of the FMPM motor is closely related to the air-gap harmonics. In this paper, an outer-rotor FMPM (OR-FMPM) motor is selected and researched, in which a low-iron-loss design is carried out considering the air-gap harmonics. In the motor, two rectangular PM pieces are artfully placed with V shape in one stator pole, which can enhance the flux-focusing effects and further increase the flux density in the air-gap. In order to reduce the iron loss of OR-FMPM motor, flux barriers are adopted purposely to adjust the harmonics which have a great influence on the iron loss, considering the relationship between iron loss and air-gap harmonics. Then, the electromagnetic performances of both the existing motor and proposed motor are compared to verify the reasonability of the low-iron-loss design. The results indicate that the iron loss of the motor can be reduced significantly, when maintain an almost consistent the output torque. Finally, a prototype is manufactured to verify the rationality of the proposed motor and the effectiveness of the proposed low-iron-loss design, which offers a new perspective on the low-iron-loss design of PM motors.

Speaker: Mr Fu Zhang (Jiangsu University School of Electrical and information engineering)

poster.pdf

poster.ppt

440 Tue-Af-Po2.20-04 [56]: Low-Weight Design Method of Electric Outboard PM Motor for Small Leisure Boat

This paper presents the design of Electric outboard Permanent Magnet(PM) motor driven at a rated output and speed of 2.5 kW and 3,000 r/min, respectively, for use in small leisure boat. The PM motor for electric outboard motors is located below the water surface and it is necessary to set the proper PM operating point in consideration of the fact that the water cooling can be applied. In addition, the actual driving mechanism must be capable of at least three speed adjustments and rapid acceleration/ deceleration at the same time. In this paper, the final design model that satisfied the above specifications of electric outboard PM motor is performed with finite element analysis(FEM). The optimal design is to improve the output density to achieve low-weight and to compare the outer rotor type with the inner rotor type. Finally, the validity of the low-weight design method is verified through manufacturing prototype and experiments.

Speaker: Hyungkwan Jang (Hanyang University)

441 Tue-Af-Po2.20-05 [57]: A New Hybrid Excitation Synchronous Machine with Radial Combination of PM and ALA

A permanent magnet synchronous machine (PMSM) has the advantages of simple structure, high power density and high efficiency, without the excitation winding and its loss. However, the magnetic field in PMSM is difficult to be regulated, due to its excitation by permanent magnet (PM), which leads to limited constant power speed range (CPSR) as a motor and/or confined voltage regulation capacity (VRC) as a generator. In the recent decades, the hybrid excitation synchronous machine (HESM), which combines PM with axially-laminated anisotropic (ALA) in the axial direction in the rotor, has attracted a lot of interests. It tries to take advantages of both PMSM and ALA reluctance synchronous machine (RSM), which can easily achieve wide CPSR and/or excellent VRC based on the electric excitation (EE). However, since the magnetic fields of the PM part and the ALA part are almost self-governed in the rotor with the essential magnetic barriers between the two parts for this kind of HESM, the existing axial combination of PM and ALA cannot sufficiently develop the performances of the HESM.
In this paper, a new combination structure of PM and ALA is proposed, in which PM and ALA are composed in the radial direction in the rotor. In this way, the magnetic fields of the PM part and the ALA part work both in serial and in parallel. The inductances of the direct axis and the quadrature axis of PM part are deeply influenced by the ALA part. The direct axis inductance could be much bigger than the quadrature axis inductance, which is different from the traditional PMSM. And EE can increase or decrease the magnetic field of PM according to different load conditions of applications. Moreover, some more details of the new HESM introduced in this paper, such as the design principle of the radial combination of PM and ALA and its effects on the parameters and performances of HESM, will be discussed in the full paper.

Speaker: Hongqin Xie (Sichuan University)

442 Tue-Af-Po2.20-06 [58]: Research on the cost-effectiveness for a flux-biased flux-modulated permanent magnet motor

Flux-modulated permanent magnet (FMPM) motors have been considered as a promising candidate in the direct drive application due to the superior torque performance in the low speed condition. Yet, the output torque capability of the FMPM motor generally relies on the expensive rare earth permanent magnet (REPM), which is same to the conventional permanent magnet motor. It greatly limits the sustainable development of the FMPM motors, especially the unstable supply of the REPM material. Thus, the motor cost-effectiveness has become a hot topic in the researches of FMPM motors. In this paper, a flux-biased dual-airgap flux-modulated permanent magnet (FBAD-FMPM) motor is proposed, where the relative position of the double rotors is fixed with the 90deg of electrical angle in the operation. The key of the motor is to introduce the flux-biased concept to effectively improve the torque performance with a relatively less REPM. Meanwhile, the leakage flux generated by the REPM in the stator is reduced by the special design of dual-airgap, which has great influence on the improvement of permanent magnet utilization. Thus, a high cost-effectiveness is achieved in the proposed FBAD-FMPM motor. In order to clearly demonstrate the potential performance features of the FBDA-FMPM motor, a regular double airgap flux-modulated permanent magnet motor is selected and compared, which possesses the same motor sizes and similar topology for fair comparison. The results show that the PM cost of FBDA-FMPM motor is reduced by 30% while the output torque capabilities of two motors are same. It denotes that the proposed FBDA-FMPM motor possesses higher cost-effectiveness. Finally, a prototype is manufactured to verify to the rationality and performances advantages of the proposed motor.

Speaker: Zixuan Xiang

443 Tue-Af-Po2.20-07 [59]: Comparative Study on A Novel Modular Multistage Axial Flux Permanent Magnet Machine with Different Core Materials

Comparative study of a 5kW novel modular multistage axial flux permanent magnet machine (MMAFPMM) is carried out. The mentioned MMAFPMM has three rotors and two stators. The rotors and stators are arranged in axial direction alternately and the two sets of windings are independent. So there are different forms to adopt the different operating conditions. They can work in respective, series-wound, or shunt-wound form. As a key part of the machine, stator core have significant contribution to behaviors of machine such as magnetic field distribution, back electromotive force (EMF), electromagnetic torque, and core loss. In order to analyze the influence of different materials used in stator core, comparative study is carried between silicon steel, amorphous alloy, and soft magnetic composite. A 3-D finite element method (FEM) model is built and different materials are applied to analyze the mentioned MMAFPMM. No-load, full-load, magnetic field distribution, core loss, etc. are calculated. FEM result indicates that SMC and amorphous alloy have almost equal influence with silicon steel on magnetic field distribution, back EMF, and electromagnetic torque. But in aspect of core loss, difference appears between SMC, amorphous alloy, and silicon steel. Due to the high resistivity, the eddy loss of SMC is rather lower than amorphous alloy and silicon steel, but the hysteresis loss is higher due to the higher coercivity. Amorphous alloy has better electromagnetic performance than SMC, but the mechanical property limits the application to the MMAFPMM. Finally, SMC material is selected to fabricate a prototype. No-load and full-Load experiment are carried out to test the performance. An improved method using lever principle is applied to measure the cogging torque. The experimental results is consistent with the FEM results and confirms the validity of machine design.

Speaker: Mr Songjun Sun (State Key Laboratory of Advanced Electromagnetic Engineering and Technology，School of Electrical and Electronic Engineering，Huazhong University of Science and Technology)

2Poster_Material.pdf

444 Tue-Af-Po2.20-08 [60]: A novel tubular switched reluctance linear machine shielding from end magnetic effect

Traditional linear machines are under great influence of end effect because of their finite stacking lengths in transverse and longitudinal directions. Transverse end effect will produce a lot of flux leakage enclosed with air. Longitudinal end effect will cause imbalance of phase performance so that linear machine’s force fluctuation is aggravated. In this paper, a novel tubular switched reluctance linear machine (TSRLM) is proposed, which can shield from unexpected impact of end effect. In structure, there is no transverse cut in tubular linear machines, so tubular linear machines are not influenced by transverse end effect. The stator sleeve of proposed TSRLM includes six ferromagnetic rings and five spacer rings. There are twelve salient poles on every stator ferromagnetic ring. The winding coils are all through windings. The mover is composed of an aluminum tube and several fan-shaped poles. The adjacent fan-shaped poles are placed at 120 degree intervals. The stator poles of energized phase only drag the the mover ferromagnetic rings with the same-direction fan-shaped poles. Three phases are energized alternatively, then, the mover reciprocates. It also operates according to the minimum reluctance principle. This structure makes cyclic arrangement of three-phase windings possible so that there is no deviation in phase at end or phase in the middle, and their coupling effects are balanced. Thus, this machine is also not influenced by longitudinal end effect. Then it is modeled by 3-D finite element method. The mutual inductance is also considered in this model. And a prototype is manufactured, and its corresponding hardware platform is established. A series of simulations and experiments verify that there is no deviation performance among phases. Traditional longitudinal end effect in linear machines caused by longitudinal cuts can be thoroughly evaded.

Speaker: Hao Chen (China University of Mining & Technology)

MT26(3) .pdf

445 Tue-Af-Po2.20-09 [61]: Cogging Torque Reduction in Double-Rotor Hybrid Excited Axial Switched-Flux Permanent Magnet Machine

The double-rotor hybrid excited axial switched-flux permanent magnet (PM) (DR-HASFPM) machine is a novel hybrid excited machine with single stator and double disk-type rotors. The double rotors have same structure without PMs and windings. The stator contains 6 doubly-H-shaped cores and 6 interlaced magnetized PMs. The PMs are sandwiched between the two doubly-H-shaped cores, where the armature windings are coiled on the sandwich units. The excitation windings are wound around the middle teeth of the doubly-H-shaped cores.
The machine exhibits a lot of merits such as short axial length, simple and compact structure, high power/torque density, large torque capability, and wide speed-regulation range, which has good prospect for in-wheel traction motor. However, it has relatively high cogging torque due to the doubly salient structure and high air-gap flux density. Therefore, the cogging torque reduction methods, including notching and chamfering in the stator and rotor teeth, are investigated in this paper.
The expression of the cogging torque is deduced by energy method, and the composition as well as the influence factors are analyzed. Based on 3-D finite-element method, the cogging torque reduction techniques including notching or chamfering in the stator/rotor, both notching and chamfering in the stator and rotor are investigated. Meanwhile, the influence of the dummy slot width, depth, location, shape and number, and chamfering width on the cogging torque, electromagnetic torque, especially the average output torque and torque ripple are compared and evaluated in detail.
The results indicate that the cogging torque reduction effect by notching in the rotor teeth is well, and the technique of adding two dummy slots is better than that of adding one dummy slot. Besides, the chamfering technique in both stator and rotor reduces the cogging torque and hardly affects the average torque. The combination of notching and chamfering in the rotor teeth can significantly reduce the cogging torque with negligible reduction of the average torque in the novel DR-HASFPM machine.

Speaker: Deyang Fan (Jiangsu University)

Tue-Af-Po2.20-09 [61].pdf

446 Tue-Af-Po2.20-10 [62]: Optimization Design and Performance Analysis of Bearingless Flux Switching Permanent Magnet Motor with Multi-tooth Structure

The bearingless flux switching permanent magnet (BFSPM) motor integrates the advantages of magnetic bearings with no mechanical wear, no lubrication, high speed and high precision, long service life, etc., as well as inherits some merits of flux switching permanent magnet motors with fast heat dissipation, low demagnetization risk, high critical speed and so on. In recent years, it has important scientific research and application value in centrifuge, sealed pump, flywheel energy storage, semiconductor industry and other special electric drive fields. However, the structure of doubly-salient pole and the excessive use of permanent magnets in the BFSPM lead to high torque ripple and high cost, which limit its application range to some extent.
In order to solve these problems above, a BFSPM motor with stator multi-tooth structure is proposed in this paper. Firstly, the basic structure and operation principle of the motor are analyzed in detail. Then, the key dimension parameters of stator and rotor are deduced according to the empirical formulas. Then, based on the finite element analysis (FEA) software, the performance of the motor, such as back EMF, flux linkage, inductance parameter, harmonic characteristic and cogging torque, is simulated respectively, and the simulation results are compared with that of the traditional BFSPM motor. Finally, the simulation results show that compared with the traditional BFSPM motor, the cogging torque and torque ripple of the multi-tooth bearingless flux switching permanent magnet (MT-BFSPM) motor proposed in this paper, are significantly reduced by around 56.4% and 13.6%, whereas the suspension force is increased by around 5% after parameter optimization.

Speaker: Mrs Ying Xu (Jiangsu University)

Xu Ying-Poster.pdf

Xu Ying-Poster.ppt

447 Tue-Af-Po2.20-11 [63]: A Novel Flux Switching Claw Pole Machine with Soft Magnetic Composite Cores

Flux switching permanent magnet machine (FSPMM) is a new permanent magnet machine, with installing permanent magnet (PM) in between of adjacent stator tooth to form good flux concentrating structure and there is no windings or PMs on rotor core. Claw pole machine (CPM) is a special kind of transverse flux machine (TFM), compared with TFM the CPM can have higher torque ability and power factor, as the adopted claw pole teeth can help CPM use more PM fluxes and reduce the flux leakage ]. With the advent of soft magnetic composite (SMC) material, the manufacturing process of CPM with SMC cores can be much easier. Combing the above two machines and new material, this paper proposes a novel flux switching claw pole machine (FSCPM) with soft magnetic composite (SMC) cores. The proposed FSCPM has both advantages of flux switching permanent magnet machine (FSPMM) and claw pole machine (CPM) with SMC cores. Specifically, with permanent magnet (PM) installed between the stator claw pole teeth, FSCPM can have merit of good flux concentrating characteristic thus the air gap flux density can be improved greatly. As the applied claw pole teeth and global winding, the torque coefficient of FSCPM is relatively high. The mechanical robust ability of FSCPM is quite good due to there is no windings or PMs on rotor core. The core loss of FSCPM at high operation frequency is relatively low for the SMC material has lower core loss properties at high frequency compared with silicon steels. The topology and operation principle of FSCPM are explained at first. To seek better performance, the main dimensions of FSCPM are optimized. Finally, the main parameters and performance of FSCPM are calculated based on 3D finite element method (FEM).

Speaker: Dr Chengcheng Liu (Hebei University of Technology)

MT Liu chengcheng.pdf

MT Liu chengcheng.pptx

448 Tue-Af-Po2.20-12 [64]: Presentation withdrawn

Tue-Af-Po2.21 - Motors VIII

Conveners: Dr Anna Kario (GSI Helmholtzzentrum für Schwerionenforschung GmbH), Takanobu Kiss (Kyushu University)

449 Tue-Af-Po2.21-01 [65]: Inductance tracking Method for Interior Permanent Magnet Synchronous Motor by Electric Torque Estimator

Interior permanent magnet synchronous motors (IPMSM) are widely applied to various industry applications such as electric vehicle, wind power generator, industrial servo motor, and home appliance due to advantage of wide speed range, high power density, high efficiency and excellent control performance. To realize a high performance and reliable IPMSM drive system, the exact knowledge of the IPMSM parameters is indispensable. Since IPMSM has a cross saturation, motor parameters change nonlinearly with electric current magnitude and phase angle. Inaccurate parameters can cause problems with output degradation, low efficiency operation, and even out-of-synchronization. Especially, as the change of inductances varies irregularly depending on the power, shape, and operating characteristics of motor, the incorrect estimation of inductances reduces motor operation performance. Thus, accurate real-time estimation of inductances is a necessary factor in designing the controller and ensuring excellent control performance.
The advantage of the offline parameter estimation techniques is that it is easy to implement with a simple algorithm. Nevertheless, there is a disadvantage that additional equipment is required and measurement errors are caused by measurements performed at a single point.
The online parameter estimation techniques are introduced as the model reference adaptive control techniques, observer-based techniques, extended kalman filter based Techniques, and neural network techniques. These techniques are suitable for applications that have various operation ranges, because it is estimated during operation.
Previous technologies have the disadvantage that it does not take into account the irregular operating conditions of the motor or requires complex calculations. Additionally, the magnetic flux is required for the conventional parameter estimation techniques, which can vary due to the motor temperature or magnetic saturation. Thus, it is difficult to exactly estimate a parameter.
This Letter proposes a new method with online parameters identification using electric torque estimator without considering the magnetic flux. This estimator is made up of dq axis voltage and current parameter so that the torque of the IPMSM can be calculated without additional equipment.

Speakers: Hyungkwan Jang (Hanyang University), Hyunwoo Kim (Hanyang University)

Tue_Af_Po_21_01.pdf

450 Tue-Af-Po2.21-02 [66]: Thermal-Electromagnetic Design of ISG WFSM Motor for Vehicle Considering Cooling System

In recent years, researches on high output and high efficiency of electric devices in all industries have been actively carried out due to strengthened regulations on energy consumption and environmental pollution worldwide.
In order to achieve high power efficiency and high efficiency in the motor industry, it was mainly used for rare earth motors using rare-earth magnets with high energy density. However, demand for derealization studies is underway due to the large amount of environmental pollution wastewater and pollution occurring in rare earth-containing mineral extraction and rare earth separation processes during the production of rare earth materials.
The motor design should be done with multi-physics design such as heat, electromagnetic field and rigidity.
The use of WFSM(Wound Field Synchronous Motor) in automotive electric motors is increasingUnlike other motors, the WFSM has coils in the field. The coil is the most heat-generating element in the motor.
The ISG motors have operating characteristics of Starting, Assisting and Generating, and Starting has high instantaneous power. If a high current flows, a high temperature is generated, which may cause deterioration of the performance of the motor.
This paper shows Thermal-electromagnetic design of ISG WFSM design. ISG Motor has each cooling system. According to cooling system, maximum calorific value is decided. The amount of heat generated by the current can be calculated through an thermal equivalent circuit, and the electromagnetic field can be designed based on this calculation.

Speakers: Hyungkwan Jang (Hanyang University), Hyunwoo Kim

451 Tue-Af-Po2.21-03 [67]: Equivalent magnetic circuit analysis of doubly salient permanent magnet motor with Π-shaped stator iron core segments

Due to the advantages of simple rotor structure and ease of PMs temperature regulation, stator permanent magnet (PM) motors have been attracted more and more attention. A doubly salient PM motor with Π-shaped stator iron core segments (Π-core DSPM motor) has been proposed, of which the special operating principle was explained by the principle of magnetic field modulation and the magnetic field density was deduced based on the equivalent magnetic circuit (EMC) method. The results of the EMC method are agreed well with those of the 2-dimensional finite element method. However, in the existing paper, the quantitative calculation of key electromagnetic performances, such as flux density, no-load EMF and torque, have not been presented in detail.
In this paper, an EMC analytical method for the Π-core DSPM motor will be presented. An EMC of the Π-core DSPM motor will be established firstly according to the distribution characteristics of main magnetic flux. On this basis, the expressions of stator and rotor permeance can be determined according to its unique double salient pole structure. Then the detailed deduction and calculation process of magnetic field density will be obtained subsequently. The deduced expressions of no-load EMF and torque will also be presented one after another. A comparative analysis of the calculation results of proposed EMC method and the 2-dimensional finite element method (2D FEM) reveals that those results are in good agreement, so that the reasonability and feasibility of proposed EMC method can be verified. Compared with the finite element method, the analytical method has the advantage of easy and fast calculation, so as to save a lot of time when analyzing many motor designs with different dimensions. So the EMC method can therefore be used as a powerful tool during the motor design processes. Thus, the preliminary design of the motor will be carried out with the proposed EMC method and the experimental results will be tested to verify the proposed analytical method.

Speaker: Yi Du (Jiangsu University)

MT26-Yi Du.pdf

MT26-Yi Du.ppt

452 Tue-Af-Po2.21-04 [68]: Three-dimensional Magnetic Equivalent Circuit Analysis of Double-sided Switched Reluctance Linear Machine

This paper proposed a 3D magnetic equivalent circuit (3D MEC) method to analyze the flux linkage characteristics of double-sided switched reluctance linear motor (DSRLM). Firstly, the 3D finite element model (3D FEM) of DSRLM is established to analyze the magnetic field line distribution of the motor. Then, the magnetic field distribution of two representative positions (unaligned and aligned position) is mainly analyzed, and the magnetic resistance of each part was obtained by the magnetic flux tube method. According to the similarity principle, the magnetic flux tube with irregular shape is equivalent to a simple magnetic circuit that is easy to calculate. The permeability and flux in each section are assumed to be constant, and the reluctance of each part is calculated. According to the similarity of magnetic circuit and electric circuit, the 3D MEC model of DSRLM was established. Secondly, according to the established 3D MEC model, the Gauss–Seidel iteration method is used in MATLAB to solve the flux linkage-current magnetization curve and the thrust-mover position curve at two representative positions, and then, compare them with the curves of the two positions derived from the 3DFEM model. Finally, experimental verification is carried out，and it shows that the solution is feasible because the error of 3D MEC is within acceptable limits.

Speaker: Hao Chen (China University of Mining & Technology)

MT26.pdf

453 Tue-Af-Po2.21-05 [69]: Presentation withdrawn

454 Tue-Af-Po2.21-06 [70]: Coupled Magnetic Field analysis and optimization of Double Stator Linear Rotary PM Machine

As the complexity of modern industrial drive systems, the two degree of freedom (2-DOF) movement is needed in many industry drive applications. In this paper, a double stator linear rotary permanent magnet machine (DSLRPMM) which features linear and/or rotary movements is investigated. The motor is constituted of two stators and a hollow mover with permanent magnets (PMs) affixed on its surfaces.
In the DSLRPMM, the linear and rotary magnetic fields are coupled in the mover core. In general, the mover core are designed as thickness as possible to avoid the magnetic field coupling. Yet, the increase of the mover mass may cause the decrease of torque/inertia ratio, thrust/inertia ratio, bearing support strength, etc.. Thus, this paper forces on the coupled magnetic field of the DSLRPMM, and the two optimized topologies of the DSLRPMM is proposed. Based on the finite element method (FEM), the electromagnetic characteristics and optimization of the DSLRPMM are investigated. The main works are listed as follows.
Firstly, the characteristics of the coupled magnetic field in the different operation conditions is studied based on the 3D FEM, and the relation between the magnetic field coupling degree and the electromagnetic characteristics including the torque, force, core loss, and etc. are also discussed. Then, two topologies of the DSLRPMM are proposed, and the electromagnetic characteristics are investigated. The magnetic field coupling of the two topologies are also studied. In order to reduce the influences of the coupled magnetic field, the electromagnetic parameters are optimized based on the multi-objective optimization method under the same constraints and goals. Lastly, the results are compared and discussed, and those will validate the effective of the DSLRPMM topologies. Moreover, the experiments will be also done to affirm the validity of the results that obtained from the simulation analysis.

Speaker: Dr Lei Xu (School of Electrical and Information Engineering, Jiangsu University)

455 Tue-Af-Po2.21-08 [71]: Considering axial phenomenon, axial permanent magnet segment motor Analysis.

As increasing of rare earth permanent magnet motor usage, IPMSM(Interior Permanent Magnet Synchronous Motor) is used in many industrial region. As used in many industrial region. researches on increasing power, efficiency and stiffness are under way. Most of these researches are interpreted as 2D model. If interpreted in 2D model, phenomenons which occur on axial direction are not considered. One of axial direction phenomenons is fringing effect. Fringing effect is related to magnetic flux interlinkage. Magnetic flux interlinkage is related to torque of IPMSM.
This paper use axial permanent magnet segment structure IPMSM. Axial permanent magnet segment cause fringing effect in the middle of stacking length. Fringing effect in the middle of stacking length exchange leakage flux to magnetic flux interlinkage. Magnetic flux linkage is proportional to torque and power of IPMSM. Flux linkage is proportional to loss. As exchange leakage flux to magnetic flux, torque and power of IPMSM increase and loss of IPMSM reduce.
To calculate magnetic flux linkage and leakage flux value. magnetic equivalent circuit is used in this paper. To confirm accuracy of calculate value, preparing no-load EMF. After calculating and confirm the volume which is caused by fringing effect, it is possible to increase accuracy of axial permanent magnet segment analysis on 2D model.

Speakers: Hyungkwan Jang (Hanyang University), Seungheon Lee

Tue_Af_Po_21_08.pdf

456 Tue-Af-Po2.21-09 [72]: Study of A Post-Assembly Magnetization Method of a V-Type Rotor of Interior Permanent Magnet Synchronous Motor for Electric Vehicle

The interior permanent magnet synchronous motor (IPMSM) has a promising prospect in electric vehicle because of its advantages of high power density, high torque density, high efficiency and good flux weakening ability. With the improvement of motor power and performance, shaped permanent magnet (PM) pole rotors like V-type, U-type and other structures appear. The device complexity and assembly cost of traditional manufacture process which magnetizing the PMs before assembly significantly increase, together with the risk of PM damage during the process. Post-assembly magnetization method can properly overcome these difficulties with its advantages of simple installation, low cost, high safety and in-situ magnetization or demagnetization, etc. In this paper, a 50kW 8 poles 48 slots V-type IPMSM rotor for electric vehicle is selected as the prototype. An auxiliary stator type magnetizing fixture is designed to magnetize the IPMSM rotor after assembly. The needed magnetizing field configuration and minimum field intensity for saturated magnetization are calculated. The influence of saturation of silicon steel sheet and eddy current in PM during magnetization process are analyzed, according to which the parameters of the magnetizing system are optimized. The prototype experimental results are in good agreement with finite element simulation results, which indicate that the needed magnetizing field configuration and field intensity can be obtained by the designed magnetizing system, i.e., the post-assembly magnetization of the IPMSM rotor can be realized.

Speaker: Qingjian Wang (Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology)

Tue-Af-Po2.21-09_MT26_Wang Qingjian.pdf

457 Tue-Af-Po2.21-10 [73]: Optimization Method to Maximize Efficiency of a Drive Motor with Electrical Winding Changeover Technic for Hybrid EV

Drive motors for hybrid electric vehicles (EVs) have often been studied to increase their efficiency and improve the total driving distance on a single charge. The motors are required to operate over a wide operating speed range according to operating characteristics of HEVs, which should improve the efficiency in the frequent operating range. To achieve this improvement, this paper presents optimal design of interior permanent magnet synchronous motor (IPMSM) with electrical winding changeover technic (EWCT) to maximize the efficiency of hybrid EV based on finite-element analysis. Since IPMSM has outstanding performance in terms of wide operating speed range, high efficiency and power density, IPMSM has often been used in EV applications. However, because a back-electromagnetic force (EMF) of the IPMSM increases linearly with speed, the motor can be damaged by an excess voltage at an overspeed. The EWCT is a method to switch the number of turns to decrease the back-EMF at high speed, which can extend the operating speed range under a limited maximum voltage. For this motor, two switching steps of EWCT were adopted, where the turn number of the first switching step is twice that of the other switching step. According to two switching steps, the performance of the IPMSG changes greatly in terms of field weakening control, winding resistance, magnitude and phase shift of current, etc. These characteristics also affect the efficiency including copper loss and iron loss. As a result, the two efficiency maps are presented, which can be operated for better efficiency.
In optimal design, maximizing the efficiency is applied at frequent operating points of HEV, and a differing extent mesh adaptive direct search is used as the optimization algorithm. Finally, the performance and the optimization method of IPMSM are validated from experimental test results. This work is funded by the Korea Automotive Technology Institute.

Speaker: Dr Ho-Chang Jung (Korea Automotive Technology Institute)

poster.pdf

poster.pptx

458 Tue-Af-Po2.21-11 [74]: Optimization Design of Segmented Permanent-Magnet Shape by Analysis of Thermal Characteristics

The brushless direct current motor (BLDC) is considered as the most suitable model to satisfy the characteristics of electric compressors. Segmented permanent magnet was used to improve the efficiency of the electric-driven compressor of electric vehicles motor. It is one of the methods for reducing the eddy current loss. The thermal characteristics of the motor are analyzed according to the change of the eddy current loss. Thermal analysis for partial thermal distribution will be analyzed using CFD program. Irreversible demagnetization characteristics are different according to permanent magnet shape. In this paper analysis of eddy current loss and demagnetization characteristics of permanent magnet according to segment type. The maximum efficiency was analyzed by consider the shapes of various magnets. The simulation is performed using a permanent magnet divided horizontally and vertically. The irreversible demagnetization characteristics of magnets, which is one of the factors that determine the performance of a motor, should be carefully analyzed and designed. The occurrence of irreversible demagnetization in a permanent magnet can be largely divided into two types: an external demagnetization field and demagnetization phenomenon by temperature change. In this paper, an optimum model which is considered minimizes the vibration, eddy current loss and irreversible demagnetization according to the segmented of permanent magnet is proposed. So we studied optimal design after analyzing the characteristics of demagnetization at external magnetic field and high temperature and we analyze the eddy current loss reduction according to the shape of the segmented magnet. Back_EMF was compared to analyze the permanent magnet demagnetization ratio. Also, resonance frequency is analyzed through simulation of modal analysis and harmonic response. The ANSYS Electromagnetic Suite 19.0 was used to analyze irreversible demagnetization under driving conditions.

Speaker: Jonghun Lee (Keimyung University)

MT26_1199.pdf

Tue-Af-Po2.22 - Stability of Conductors and Coils II

Conveners: Haigun Lee (Korea University), Honghai Song (Brookhaven National Laboratory)

459 Tue-Af-Po2.22-01 [75]: Investigation on Electrical and thermal behaviors of 2G HTS Racetrack Coil with Metal-Insulator Transition Insulation Material under External Time-Varying Magnetic Field

This paper presents the basic investigation results on electrical and thermal characteristics of second generation high temperature superconducting race-track coil (2G HTS RTC) under external time-varying magnetic field. This RTC is electrically and thermally insulated by a vanadium III oxide (V2O3), which is one of the metal-insulator transition (MIT) materials and has a variability in the contact resistance with temperature changes. A synchronous rotating machine can be frequently operated under time-varying magnetic field of unsynchronized armature. Therefore, the electrical and thermal behaviors of MIT RTC should be examined and proved to confirm the applicability of MIT insulator on the turn-to-turn insulation of field coil for rotating machine. In this study, under external rotating magnetic field with various magnet grade, the basic behaviors of MIT RTC such as voltage, temperature, and center magnetic field are experimentally investigated in operating current charging in steady-state as well as overcurrent charging in transient-state.

Acknowledgement: This work was supported in part by the “Human Resources Program in Energy Technology” of the Korea Institute of Energy Technology Evaluation and Planning (KETEP), granted financial resource from the Ministry of Trade, Industry & Energy (MOTIE), and by Korea Electric Power Corporation. (Nos. 20184030202200 and R18XA03)

Speaker: Jung Hyup Ko (Jeju National University)

460 Tue-Af-Po2.22-02 [76]: Smart Insulation that Enables Calculation of Operating Current of ReBCO Coil

This paper proposes a heretofore unestablished process to calculate the operating current of a ReBCO coil based on the electrical stability of smart insulation (SI) ReBCO coil. The nonhomogeneity of the critical current (IC) of the ReBCO coated conductor (RCC) makes the calculation of the coil IC from the IC-B-T data of a short sample difficult. In addition, at the determining the operating current, even if the coil IC is measured, due to factors such as load conditions, magnetic field, and cooling, a margin of error is given without any clear criteria. The SI ReBCO coil uses a V2O3 material with metal–insulator transition (MIT) characteristics instead of the polyimide film, which is used as a conventional insulating material. A material with MIT characteristics transitions to an insulator below a certain temperature and to a conductor above a certain temperature. The V2O3 material has a transition temperature of approximately 150 K. For the SI ReBCO coil in liquid nitrogen, in a steady state, controllability is ensured by the operation of the insulation coil. Conversely, in the transient state, electrical stability is ensured by the operation of the no-insulation coil for which turn-to-turn current bypass occurs. Accordingly, we propose a process for calculating the operating current based on the characteristics of the SI ReBCO coil. It can address the problem of permanent burnout due to the RCC nonhomogeneity and transient state instability of the conventional ReBCO coil. The proposed process to calculate operating current was verified based on experimental and simulation data of SI ReBCO coils of various specifications.

This research was supported by Korea Electrotechnology Research Institute (KERI) Primary research program through the National Re-search Council of Science & Technology (NST) funded by the Ministry of Science, ICT and Future Planning (MSIP) (No. 19-12-N0101-50).

Speaker: Dr Hyung-Wook Kim (Korea Electrotechnology Research Institute)

MT26_Poster (HW).pdf

MT26_Poster (HW).pptx

461 Tue-Af-Po2.22-03 [77]: Investigation on the Thermal and Electrical Characteristics of GdBCO Magnet Using Intentional Bypass Current Path

Recently, the NI winding technique has been actively investigated to be used in HTS magnets because this technique enables the coils to become lighter and smaller than that of conventionally insulated counterparts. However, the charge–discharge rate of the NI coil is considerably higher than that of completely insulated coils due to the absence of insulation resistance. In this study, we proposed a novel winding method that employs the intentional bypass current path (IBCP) using normal metal wires directly soldered during the first and final turn of an insulated magnet; this method may allow the over-current in a quench event to be bypassed through normal metal wires. Therefore, the magnet exhibits rapid charging/discharging rates with high thermal/electrical stabilities. The charge–discharge and over-current characteristics of the magnet fabricated using the IBCP winding technique were examined and compared with that of conventional insulation and NI magnets.

[Acknowledgement]
This work was supported by the Materials and Components Technology Development Program of KEIT [10053590, Development of MgB2 wire and coil with a high critical current and long length for superconducting medical·electric power equipment].

Speaker: Mr Kim Kihyun (Korea University)

462 Tue-Af-Po2.22-04 [78]: Study on Cooling and Over-current Characteristics of a Superconducting Magnet Using a Grooved Bobbin

Despite the extensive research on a conduction cooling system, liquid helium (LHe) was still used as a cryogen to cool down the superconducting magnets due to the high-temperature deviation and mechanical vibration of this cooling system. However, in a quench event, the superconducting magnet that utilizes LHe may also exhibit temperature deviation within the magnet because the innermost turns were not exposed to LHe, resulting in slow heat dissipation. In this study, we proposed the use of a bobbin with grooves on its surface, thereby allowing the LHe to fill the grooves of the bobbin and to be the cooling channel. Cooling and over-current tests were facilitated to investigate the effects of the cooling channel on the thermal and electrical stabilities of the GdBCO magnet with regard to the width and depth of the groove. The experimental results were compared with the simulations that employ a finite element analysis method.

[Acknowledgement]
This work was supported by the Materials and Components Technology Development Program of KEIT [10053590, Development of MgB2 wire and coil with a high critical current and long length for superconducting medical·electric power equipment] and in part by the Korea Basic Science Institute under Grant D39614.

Speaker: Mr Hyun Sung Noh (Korea University)

463 Tue-Af-Po2.22-06 [79]: Investigation on the correlation between electric and thermal contact resistance of REBCO HTS wires

No insulation (NI) winding technique using a REBCO wire is considered as a feasible option to develop a high field magnet due to its excellent electric and mechanical stability. A NI magnet shows strong thermal and electromagnetic stability in case of quench, however, it also has charging delay due to leak currents and additional resistive loss through turn-to-turn winding contacts. The stability and the charging delay are strongly related to the electric and the thermal contact resistance between winding turns. To predict the electric and the thermal behavior of the NI magnet, it is necessary to estimate the electric and thermal contact resistance between winding turns. The electric contact resistance can be obtained through charging and discharging test of the magnet or from the measured ones. Yet, the thermal contact resistance is hard to measure because it requires a complicated measurement apparatus. Since the electric and thermal conductivity of metals are correlated to so-called Weidemann-Franz law, the electric and thermal contact resistance between stacked REBCO wires are supposed to have similar relation.
In this study, stacked REBCO wires were installed in a conduction cooled test apparatus to measure the electric and thermal contact resistances in a temperature range of 4 to 90 K. During the experiment, Belleville washers were used to apply designated contact pressures. The measured data shows a meaningful correlation between the electric and the thermal contact resistance, which is similar to Weidemann-Franz law. This correlation will be used to estimate an effective thermal conductance of NI magnet from the measured electric contact resistance. In addition, it can be applied to determine an appropriate operating sequence of initial charging and to simulate a post-quench behavior.

This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. NRF-2017M1A3A3A02016566)
This research was supported by Korea Electric Power Corporation. (Grant number:R18XA03)

Speaker: Geonhang Seo (Changwon National University)

Poster_Tue-Af-Po2.22-06_Investigation on the correlation between electric and thermal contact resistance of REBCO HTS wires_Geonhang SEO.pdf

464 Tue-Af-Po2.22-07 [80]: Quench test of a stacked REBCO coil composed of six single pancakes with electrically conductive epoxy resin

A coil without turn-to-turn insulation, called a no-insulation (NI) coil has been developed. The NI winding technique has been reported to be a promising method of quench protection. In order to apply the NI winding technique to a conduction-cooled REBCO coil, we developed a coil using an electrically conductive epoxy resin. The electrically conductive epoxy resin in which a metal power was mixed was applied to the edge of the winding. If thermal runaway of the coil is observed, the excessive current could be automatically bypassed through the electrically conductive epoxy resin [1]. In order to confirm the effect of a larger coil with higher stored energy with the electrically conductive epoxy resin, we fabricated and tested a stacked coil composed of six single pancakes whose inner diameter and outer diameter were 500 mm and 554.5 mm, respectively. The detailed features of a stacked coil with electrically conductive epoxy resin and the test results of over-current tests under conduction-cooled conditions will be presented at the conference.

[1] H. Miyazaki, et al: “Over-current Test of REBCO Pancake Coils Impregnated with Conductive Epoxy Resin Under Conduction-cooled Conditions,” 5LOr1C-02, 2018 Applied Superconductivity Conference, Seattle, USA, Oct. 28- Nov. 2, 2018

Speaker: Dr Hiroshi Miyazaki (Toshiba Energy Systems & Solutions Corporation)

465 Tue-Af-Po2.22-08 [81]: Presentation withdrawn

466 Tue-Af-Po2.22-09 [82]: Characteristics research on BSCCO HTS tapes with short-circuit impulse current impact at LNG cooling ambient temperature

The DC superconducting energy pipeline has the advantage of integration of power and fuel, in which the superconducting cables are cooled by liquefied natural gas (LNG) coolant. As one of the newly developing technology of superconductivity in power system, the integrated delivery has the superiority that its total efficiency of energy transportation could reach 96%, for the power loss is only 1/3 of that of separate delivery of power and fuel.
In order to guarantee the safe operation of the DC superconducting energy pipeline, it is important to study the ability of superconducting tapes to withstand the short-circuit impulse current at LNG temperature. A test platform has been established which consists of a closed and pressurized dewar, an impulse current source, an oscilloscope and a cryogenic auxiliary system. Heating LN by an electric heating resistor in the pressurized dewar, we achieve the ambient temperature of 85-90K, which is near to LNG temperature in the DC superconducting energy pipeline. Three kinds of BSCCO HTS tapes, which are Type H, HT-CA and HT-SS, have been tested under the impact of short-circuit impulse current by increasing the current amplitude gradually. The test results show that the HT-CA tape has the best ability to withstand short-circuit impulse current with amplitude of 1700A and lasting period of 7ms. There is no degradation for this kind of tape and it maintains perfect without any hurt by over heat. Moreover, the critical current does not decrease after withstanding the impulse current. This study contributes to the optimization and stable operation of the DC superconducting energy pipeline.

Speaker: Mr Guangrui Zhao (Department of Electrical Engineering, Tsinghua University )

Tue-Af-Po2.23 - Novel and Other Applications I

Conveners: Honghai Song (Brookhaven National Laboratory), Philippe Masson (AML Superconductivity and Magnetics)

467 Tue-Af-Po2.23-01 [88]: Recent State of The Art Magnets for Beamline Applications

High-field split solenoids requirements for beamline applications have become increasingly demanding and an area of significant development in magnet engineering. A number of new magnet designs have been developed utilizing the high current density achievable in modern Nb3Sn superconductors. The magnets described are custom designed for individual experimental applications and have unique design features in order to maximize both the central field and beam access. These high field compact magnets provide significant engineering challenges due to high coil forces and current densities required for each new geometry. These include a 12T/11T actively shielded symmetric and asymmetric operation with a 35 mm split and ±4° to a 20 mm high x 20 mm diameter sample volume The development of a higher field 14T/12T symmetric and asymmetric operation with a parallel split of 40 mm and with ±10° angular access to a sample volume of 20 mm diameter x 20 mm height is detailed. The development steps leading to the use of Nb3Sn to achieve a lower field 7T actively shielded magnet with ±10 to an extended 40 mm high x 20 mm diameter sample volume are also described.

Modelling of the high stresses on both the coils and the magnet formers holding the coils are described as well as the quench management approach required to manage the stored energy. Other recent advances in active shielding of the beamline magnets to restrict stray field effects in both symmetric and non-symmetric modes of operation are also described

Speaker: Daniel Strange (Oxford Instruments)

468 Tue-Af-Po2.23-02 [89]: A Hybrid Trapped Field Magnet Lens (HTFML): concept and realisation

In this presentation, the concept of a Hybrid Trapped Field Magnet Lens (HTFML) is described, which exploits two different characteristics of type II superconductors: the “vortex pinning effect” of an outer superconducting bulk cylinder, which acts as a trapped field magnet (TFM) using field-cooled magnetization (FCM), combined with the “diamagnetic shielding effect” of an inner bulk magnetic lens. The HTFML can reliably generate a concentrated magnetic field in the centre of the lens that is higher than the trapped field from the cylindrical bulk TFM and the external magnetizing field, even after the externally applied field decreases to zero. This requires that, during the FCM process, the outer cylinder is in the normal state (T > superconducting transition temperature, Tc) and the inner lens is in the superconducting state (T < Tc) when the external magnetizing field is applied, followed by cooling to an appropriate operating temperature, then removing the external field. The concentrated magnetic field in the HTFML changes depending on the superconducting characteristics of the materials used, their shape and size, as well as the magnetizing conditions. This is explored for two potential cases: 1) exploiting the difference in Tc of two different bulk materials (“case-1”), e.g., MgB2 (Tc = 39 K) and Gd-Ba-Cu-O (Tc = 92 K) or 2) using the same material for the whole HTFML, e.g., Gd-Ba-Cu-O or (RE)-Ba-Cu-O (where RE is rare-earth element), but utilizing individually-controlled cryostats, the same cryostat with different cooling loops or coolants, or heaters that keep the outer bulk cylinder at a temperature above Tc to achieve the same desired effect. We will also report sample fabrication and experimental results towards realising an all-(RE)-Ba-Cu-O HTFML practically.

Speaker: Dr Mark Ainslie (University of Cambridge)

MT26 2019 Poster HTFML.pdf

469 Tue-Af-Po2.23-03 [90]: Presentation withdrawn

470 Tue-Af-Po2.23-04 [91]: Research on the Squeeze Current Effect of the Foil-type Excitation Windings under the Condition of High Frequency

Combined with the design of magnetic properties measurement structure and high frequency transformer, the traditional copper stranded wire windings increase the design demand of the core window area to limit the improvement of measuring device. The kind of winding has many turns leading to an increase in inductance. In this paper, an improved windings design method is proposed to optimize the magnetic properties measuring device and high frequency transformer that decreases the inductance and volume of windings. The excitation windings will be in foil-type structure under the condition of large current. But the current density distribution of foil windings is more complex in high frequency. The squeeze current effect of the foil windings comes from the magnetic induction strength B perpendicular to the copper foil, and the varying magnetic flux produces the eddy effect inside the copper foil windings. The induced current will affect the distribution of the conduction current in the windings. As the frequency increases, this phenomenon will become more pronounced. Some methods are to add magnetic shielding plate at both ends of the windings. But these methods have yet to consider various factors under the comprehensive high frequency impact. In this paper, the method that diminishing the squeeze current effect by optimizing the foil windings parameters and adding the shielding plate is described in detail. The influence factors of current density distribution in foil windings are analyzed from the width, thickness, segment number of windings and frequency. Meanwhile, the squeeze current effect of foil windings can be reduced by applying the magnetic shielding plate on both sides of the windings, and the influence of the magnetic shielding plate parameters on the squeeze current effect is analyzed in detail. A good current sharing effect can be obtained.

Speaker: Prof. Yongjian Li (State Key Laboratory of Reliability and Intelligence of Electrical Equipment,School of Electrical Engineering, Hebei University of Technology)

Tue-Af-Po2.23-04 [91] Research on the Squeeze Current Effect of the Foil-type Excitation Windings under the Condition of High Frequency.pdf

471 Tue-Af-Po2.23-05 [92]: Development of a Prototype MgB2 Superconducting Solenoid Magnet for High-Efficiency Klystron Applications

An MgB2 superconducting magnet for X-band (12 GHz) Klystrons has been designed, manufactured and tested. According to a CLIC-380GeV staging scenario at CERN, about 5000 sets of klystrons will be used. The Klystrons need electron beam focusing solenoid magnets, and the power consumption of 5000 magnets using Cu conductor is estimated to be 100 MW in case. This MgB2 superconducting solenoid magnet is planned to reduce the energy consumption to one tenth, 10 MW. And also the magnet is designed to absorb the stored energy by coils in case the quench occurs.
This paper describes the magnet design fulfilling above requirements, the test results of a preliminary experimental coil, and the test results of the prototype magnet. Two coils included in the magnet are conduction-cooled by using Sumitomo’s cryocooler CH-204. This magnet is designed to produce 0.8 T at I = 57.1 A, with a maximum field of 1.1 T in the coil winding. The coils were made by wind & react method and were resin-molded. In the performance test about 10 times quench tests including 10 % overcurrent one have been conducted and the coil temperature rise after quenches has been measured to be less than 200 K. The magnet has no deterioration. The field distribution has been measured and confirmed to agree with the simulated value.

Speaker: Mr Hiroyuki Watanabe (Hitachi, Ltd.)

Tue-Af-Po2.23-05[92] Watanabe.pdf

472 Tue-Af-Po2.23-06 [93]: Experimental Analysis of the Interference-Fit Joining of Aluminium Tubes by Electromagnetic Forming

This article investigates the main parameters influencing the joint strength of tubular components by electromagnetic compression, more specifically interference-fit (force-fit) by crimping tubes into mandrels. The mechanical parameters considered in this analysis are the remaining residual stress on the mandrel, the joining area and its shape, and the interfacial friction coefficient between tube and mandrel. These parameters are related in a very complex way with electromagnetic compression process parameters, starting with the charging energy and the distribution of the magnetic pressure pulse that triggers the forming process, the initial gap between the joining parts, the material components and geometry, the shape and surface roughness of the mandrel. This work investigates the Interference-fit joining of aluminum alloy tubes AA6082-O with mandrels of different materials and metallurgical conditions (AISI 1045, AA6082-O and AA6082-T6) and, therefore, the process is analyzed by the gradual influence of other process parameters such as the initial gap between joining partners, the energy pulse, the field shaper geometry, the mandrel material and surface roughness in order to manufacture joints of maximum strength. The achieved results indicate that the joint strength and its associated failure mechanism are directly related to process parameters and are an important contribution to the development and industrial implementation of this technology.

Speaker: Prof. Evandro Paese (Departamento de Engenharia Mecânica, Universidade de Caxias Sul, Campus Universitário da Região dos Vinhedos)

Geier et al 2019 Experimental Analysis of the Interference-Fit Joining of Aluminium Tubes by Electromagnetic Forming.pdf

473 Tue-Af-Po2.23-07 [94]: Design and experimental implementation of a novel electromagnetic stirring system for casting particle-reinforced aluminum matrix composites

Stirring casting is one of the most commonly used fabrication processes for particle-reinforced aluminum matrix composites (PRAMCs). It includes mechanical stirring and electromagnetic stirring. Compared with the former, electromagnetic stirring has advantages of non-contact, flexible force loading and so on. However, the structure of traditional electromagnetic stirrer (EMS) is similar to the stator winding of three-phase asynchronous motor, which is cumbersome and complex. In order to overcome the disadvantages of traditional stirring casting, a novel electromagnetic stirring system consisting of an solenoidal electromagnetic stirrer (SEMS) and a temperature control device is proposed in this paper. SEMS draws lessons from the idea of tube compression in electromagnetic forming. Compared with EMS, the structure of SEMS is quite simple and compact.Only a single coil is required to produce an alternating magnetic field. According to the law of electromagnetic induction, the conductive molten aluminum is subjected to Lorentz force generated by the magnetic field and induced eddy current. The nonuniform distribution of the force causes strong stirring effect, which enables the reinforced particles to distribute evenly in the aluminum matrix. The temperature control device, composed of a resistance furnace, a thermocouple and a control box, is used to keep the aluminum matrix molten.To verify the feasibility of the proposed electromagnetic stirring system, a coupling model of electromagnetic field and flow field is established to study the relationship between the magnetic field strength, frequency and electromagnetic stirring force by numerical analysis. On this basis, the electromagnetic stirring system is fabricated and tested, of which the working coil has 96 turns and an inductance of 5.8mH. The system can provide different magnetic field strength (0~50mT) and frequency (0~200Hz) in the region of interest. More importantly, it has been demonstrated that the composite suspension consisting of aluminum and particles can be well stirred under these parameters.

Speaker: Junyu Fu (Huazhong University of Science and Technology,Wuhan National High Magnetic Field Center)

474 Tue-Af-Po2.23-08 [95]: Design and Fabrication of a Laboratory Electromagnet applying HTS Coils

This paper deals with the design and fabrication of a laboratory electromagnet utilizing high temperature superconducting (HTS) coils which is applied to excitate high magnetic fields compared with the conventional laboratory electromagnet with copper coils. The proposed electromagnet was composed of iron-core, HTS coils, and cryostat for the HTS coils. The components are designed using numerical calculation and finite element analysis. The electromagnet is based around a compact iron-core with HTS double pancake coils, and the electromagnetic design was carried out to take into account magnetic properties of the iron-core material and the Ic-B performance of the HTS conductor. The compact cryostat having HTS current leads is designed to reduce the thermal load of the coils. Based on the design results, the laboratory HTS electromagnet was fabricated and the performance is evaluated. The HTS coils are immersed into the liquid nitrogen of 77 K and energized up to the designed current level with the background field generated by electromgnet. In addition, the performance test result is discussed with respect to the shape of magnetic flux from iron-core.

This work was supported by KBSI grant (D39614).

Speaker: Young Jin Hwang (Korea Basic Science Institute)

475 Tue-Af-Po2.23-09 [96]: A 10+ m$^3$ Ioffe Trap for Project 8

This work was performed as part of the international Project 8 collaboration. The goal of the Project 8 experiment is to measure the absolute neutrino mass using tritium beta decays, which involves precisely measuring the energies of the beta-decay electrons in the high-energy tail of the spectrum.

To achieve its design sensitivity of $m_\beta\sim$ 40 meV, Project 8 has chosen an $\textit{atomic}$ tritium source to eliminate the energy smearing inherent to past and current molecular tritium experiments. The design sensitivity assumes a fiducial population of at least $10^{18}$ tritium atoms. The second key element which enables this sensitivity is a frequency-based energy measurement invented by Project 8 called Cyclotron Radiation Emission Spectroscopy. The CRES technique, however, has optimal sensitivity at an atom density of $10^{12}$ cm$^{-3}$. At this density, $10^{18}$ atoms occupy 10 m$^3$.

To prevent recombination of the tritium atoms on the container walls, it is necessary to trap them in a magnetic minimum. The baseline trap depth is $\Delta B = 2$ T, but even this substantial depth can only trap a population of atoms below $\sim30$ mK. The atom trapping field minimum simultaneously traps the beta decay electrons. I will discuss a candidate magnetic velocity and state selector to supply a sufficient trappable flux of atoms.

CRES further relies on a highly uniform magnetic field and precise knowledge of that field to convert the measured frequency into the electron energy. Our baseline is a background solenoid field of 1 T and a field uniformity in the fiducial volume of well below $10^{-5}$. With a fiducial volume fraction of perhaps 50%, the magnet itself takes on quite sizable proportions. I will discuss a preliminary design for a NbTi superconducting multipole (Ioffe-Pritchard) trap in the context of this large scale as required for a next-generation neutrino mass measurement.

Speaker: Alec Lindman (PRISMA+ Cluster of Excellence, Johannes Gutenberg Universität Mainz)

MT26_poster_lindman_v7.pdf

476 Tue-Af-Po2.23-10 [97]: Study on a Novel Electromagnetic Tripping System with Two Staeg Short Circuit Tripping Characteristic

Usually, the electromagnetic trip unit in AC circuit breaker has only one trip current value. When a current in circuit is greater than the trip current, the electromagnetic trip unit will be released, so it is suitable for instantaneous tripping in the case of short circuit. In this paper, a novel electromagnetic trip system with two trip current values is studied, which is suitable for two-stage tripping characteristic of circuit breaker, that is, short delay tripping and instantaneous tripping, when a short circuit is occurred. According to the characteristics of AC electromagnetic system with constant magnetic potential, a secondary winding is added to the iron core to change the value of main magnetic flux in the trip system by shorting and opening the secondary winding.Theoretical research shows that the two tripping current values can be achieved by this method.
In this paper, the overall plan with double winding controllable electromagnetic tripping unit is put forward in first. Then, a new type electromagnet tripping system is composed. Through the Maxwell equation theory, the main influencing factors （such as the air gap,the pole area, the length of the magnetic circui, and number of turns of secondary winding, etc.) for the minimum tripping current with double winding controllable electromagnetic tripping unit are analyzed under the two different working conditions. The mathematical models of double winding controllable electromagnetic tripping unit are established based on the Simulink module in MATLAB software. The simulation research and theoretical analysis shows that the two trip current values by shorting and opening the secondary winding is feasible. Finally, the 3D magnetic field model with double winding electromagnetic tripping unit is established by ANSOFT. Then the structure of the double winding controllable electromagnetic tripping unit, especially the placement position of the secondary winding is optimized. The selective protection for distribution system may be provided.

Speaker: Prof. Ming Zong (Shenyang University of technology,China)

477 Tue-Af-Po2.23-11 [98]: Experimental research on conduction cooling of superconducting induction heating magnet

Induction heating is essentially the use of electromagnetic induction in the conductor of eddy current heating to achieve the purpose of heating the workpiece, with fast, clean, convenient for surface and local heating, and in most cases energy-saving advantages. Compared with the traditional AC induction heating process, the superconducting DC induction heating device uses superconducting magnet instead of traditional copper cable magnet to produce background magnetic field in the iron core. It has obvious advantages in heating depth and heating efficiency.
In this paper, we carried out a series of cooling experiments for induction heating magnet with conductive cooling mode. The optimal cooling structure is determined by experiments on various cooling structures. Finally, relevant experiments are carried out on a formal induction heating magnet. Experiments show that the optimized conductive cooling structure can effectively refrigerate the magnet and maintain thermal stability under the condition of long-term operation of the magnet

Speaker: Mr Lei Hu

478 Tue-Af-Po2.23-12 [99]: Frequency measurement of Terahertz wave by using high magnetic field technology

This paper introduces a novel method of frequency measurement of terahertz (THz) wave with the high magnetic field technology. According to the Zeeman Effect, the magnetic field and frequency are linear, so we can convert the measurement of frequency into the measurement of magnetic field strength by this method. Two magnet systems were used in the experiment, one of them is a pulse magnet that can generate a 30T pulsed magnetic field, and the other is a superconducting magnet that produces a steady-state magnetic field of 16T. The magnitude of the magnetic field determines the range of the frequency measurement of the method. In theory, the highest frequency can be measured at 3THz of this method. Simultaneous measurement of three frequencies of 60GHz, 170GHz, 360GHz are presented for two different configurations, using different magnet components, and measured under cryogenic conditions, respectively. It is shown that the method developed is also applicable to investigation of the mono-chromaticity of the signal. Another alternative method is also provided to achieve the purpose of eliminating the measurement error of the magnetic field, and two or three frequencies are arranged to be measured simultaneously from one or two signals, which have a known frequency. Each experimental results have a good agreement with the prediction of the theory. A discussion of both methods from the aspects of the resolution and simultaneous measurement of multi-signals are described, and finally this paper concludes with a summary that the resolution of this method is about 100MHz, and multi-frequency measurement bandwidth of 300GHz is realized.

Speaker: Xin Qi

Tue-Af-Po2.24 - Novel and Other Applications II

Conveners: Rainer Meinke (AML Superconductivity and Magnetics), Sasha Ishmael (Lupine Materials and Technology)

479 Tue-Af-Po2.24-01 [100]: The development of three stage electromagnetic forming facility and its timing control system

Abstract—a Space-Time-Controlled Multi-Stage Pulsed Magnetic Field (Stic-Must-PMF) forming and manufacturing technology is introduced in Wuhan National High Magnetic Field Center, the technology is based on spatially strategically placed multiple coil systems and each coil can be addressed individually by its associated power supply with precise timing control. Such well-designed space-time distribution of electromagnetic force could lead to the forming and manufacturing of sheet and tube parts and components with controlled materials properties.
Based on Stic-Must-PMF a Three Stage Electromagnetic Forming Facility is developed. The designed facility is composed of three capacitor power modules. The total energy of each power module is 1MJ, 200KJ, and 14.4KJ respectively. The power modules can be freely selected or utilized for driving multi-stage coils under its timing control system. The precise timing control system is designed for power modules configuration and discharge control. By generating precise and synchronous triggering signals according to the requirement of forming, the multiple power modules could be discharged to multi-stage coils synchronously or in a preset time sequence.
With the application of the designed and fabricated triple-stage electromagnetic forming system, an approach of radial Lorentz force augmented electromagnetic forming is proposed to realize the deep drawing with large drawing ratio. The forming depth of aluminum alloy sheet (1060-H24) has been dramatically increased from 8.44 mm to 20.28 mm .

Speaker: Jianfeng Xie

480 Tue-Af-Po2.24-02 [101]: 30 T pulsed magnet designed for an 800 GHz gyrotron

Gyrotron is a promising source of high-frequency, high-power RF radiation for plasma heating, ESR spectroscopy, new medical technology and so on. The magnetic field system, which controls the trajectory of the electron beam and the cyclotron frequency of electrons at the resonator cavity, is one of the key parts of the gyrotron. According to the theory of electron cyclotron masers, an 800 GHz gyrotron requires magnetic fields of up to 30 T to operate at fundamental harmonic. The prohibitively expensive commercial superconducting magnet can just allow magnetic field of up to 12-15 T. But fortunately, Pulsed magnets with a maximum magnetic field up to 100 T have a relatively lower cost and simpler geometry.
In this paper, the design of a compact 30 T pulsed magnet for an 800GHz gyrotron will be proposed. The magnet has a large bore with a diameter of 80 mm for the installation of resonator tube. The magnetic field profile is given by the design of electron optics. So the magnet geometry was optimized by genetic algorithm. Then a simple one coil magnet system has been obtained. The inner radius, outer radius, and the height of the coil are R1=44.26 mm, R2=172.61 mm, and H= 352 mm respectively. A small filling factor of 28% was adopted to reduce the resistance of the magnet. Six coil layers were winded separately, and then connected by special designed copper joints. Each layer of conductor was also been reinforced by glass fiber. The magnet is powered by 5 modules of 25kV/1MJ capacitor backs. The 800GHz gyrotron can work at fundamental harmonic with the magnetic field of 29.6 T, and also at second harmonic with the magnetic field of 14.8 T.

Speaker: Dr Pengbo Wang (Huazhong University of Science and Technology)

481 Tue-Af-Po2.24-03 [102]: Poloidal Vector Potential Transformer

We constructed a long and flexible solenoid coil by winding a thin, enameled wire around a slightly thicker enameled wire. The structure of this flexible solenoid resembles that of a string of a guitar or a piano. The flexible solenoid is wound on a torus in toroidal direction.
A usual toroidal coil winds the winding in the poloidal direction, but our coils are wound in the toroidal direction. Furthermore, the winding is not a simple copper wire but the flexible solenoid. The structure of this coil is the coiled-coiled of the coil and it is nested in multiple. The structure of such a coil is used as the primary coil of the poloidal vector potential transformer. This primary coil provided with the current return path does not generate a net magnetic field outside the coil.
The secondary coil of the poloidal vector potential transformer was realized by placing a toroidal coil in its internal cavity. Since there is practically no magnetic field outside the sufficiently long solenoid coil, there is no magnetic flux inside this secondary coil, but a finite induced voltage has been observed. The induced voltage is proportional to frequency at low frequencies, but sharply increased at high frequencies with higher order of frequency response such as the squared to cubed. In this coil, the vector potential generated by the primary coil while it orbits the poloidal surface can interact with the secondary coil many times. We report the transfer characteristics, the effect of the electromagnetic shield, the result compared with the toroidal vector potential coil.

Speaker: Dr Masahiro Daibo (Iwate University)

Daibo_Tue-Af-Po2.24-03 [102]R4.pdf

482 Tue-Af-Po2.24-04 [103]: Dynamic analysis of sheet metal forming process by uniform pressure electromagnetic actuator using the finite element method

Due to its high efficiency and uniform deformation force, the uniform pressure actuator (UPA) is a potential electromagnetic forming (EMF) technology for shaping of mesoscale dimensional metals, such as metal bipolar plates. However, because of its complex structure, the current simplified two-dimensional model or three-dimensional model cannot fully reveal the law and characteristics of UPA, such as the role of conductive outer channel, the impact of contact resistance. In this paper, A three-dimensional (3D) finite element model with the equations of the electrical equivalent circuit, electromagnetic field, and mechanical field has been developed for calculating the discharge currents through the forming coil, the magnetic forces acting on the workpiece, and the plastic deformation of the workpiece by COMSOL software. The coil impedance changes during the forming process are coupled to the circuit equation through the coil voltage. The effect of air deformation caused by workpiece deformation in the structure field is coupled to the electromagnetic field through the Moving Mesh. What’s more, the contact resistance between the conductive outer channel and the workpiece in the electrical contact area is also considered. The simulation results are in good agreement with the experimental results of the induced current, magnetic field and forming depth. Finally, the general design criteria of the UPA are given, which provides a basis for the industrial application of the UPA.

Speaker: Mr Zelin Wu (Huazhong University of Science and Technology)

Tue-Af-Po2.24-04 吴泽霖.pdf

Tue-Af-Po2.24-04 吴泽霖.pptx

483 Tue-Af-Po2.24-05 [104]: Design and simulation of three-phase electromagnetic wiping device

In order to solve the problem that the traditional gas wiping method cannot meet the needs of high-speed production, the oxidation and atomization of zinc liquid which not only wastes zinc, but also disperses zinc into the air to pollute environment, a three-phase electromagnetic wiping based on traveling wave magnetic field is proposed. By using a three-phase coil, a traveling wave magnetic field is generated which can induce electromagnetic force on the surface of the galvanized layer and wipe off excess zinc liquid. There is no direct contact between the device and the workpiece. The frequency and amplitude of the coil current are controlled to achieve the control of the thickness of the zinc layer. The zinc liquid on the workpiece is uniformly applied and the direction is clearly controllable, which does not cause sputtering of the zinc liquid.
Through the theoretical analysis, the electromagnetic and mechanical simulation models of the workpiece, zinc liquid, magnet and power source are established. The main parameters of the power supply and coil, the traveling wave magnetic field and the force of the zinc liquid are simulated. The simulation results show that under the action of the coil current of several tens of Hertz and several hundred amperes, the electromagnetic force generated by the device can achieve the wiping effect of the gas wiping on the zinc liquid. The three-phase electromagnetic wiping can generate greater axial stress, and the force is more uniform, and has a better wiping effect.
A three-phase electromagnetic wiping device prototype was developed. The coil adopts a circulating water cooling system to ensure that the coil can operate in a safe temperature range. The preliminary experimental results show that it can meet the requirements of high-speed hot dip galvanizing production and has broad application prospects.

Speaker: Prof. Tonghai Ding (Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology)

MT26_Poster_Tue-Af-Po2.24-05.pdf

484 Tue-Af-Po2.24-06 [105]: Verification of an Efficient Closed Loop Degaussing Technique for a Ferromagnetic ship

Under the earth magnetic field, ferromagnetic equipments on a naval ship are magnetized, and accordingly they are apt to cause a local field disturbance underwater. To mitigate such magnetic field for ship’s safety, modern vessels are usually equipped with a degaussing system. In order to minimize the underwater field anomaly, individual coil currents are elaborately tuned, and so there are two kinds of degaussing techniques named as open loop degaussing (OLDG) and closed loop degaussing (CLDG), respectively.
Degaussing coil currents in OLDG are optimally regulated in specific magnetic treatment facilities (MTF) off shore. Since it belongs to a passive current control system, OLDG cannot make up for magnetic property change of the hull. Therefore, OLDG inevitably requires periodic maintenance of degaussing coil currents. On the other hand, an active current control system is equipped for CLDG which itself can compensate magnetic property change of the ferromagnetic hull as well as the variation of the earth magnetic field on a ship. To achieve this, CLDG additionally needs tens of onboard magnetic sensors and their processing systems. In the conventional CLDG technique, underwater magnetic field is first predicted based on the sensor signals, and then degaussing coil currents are optimally regulated. Thus, the procedure for CLDG is somewhat complicated, and requires a relatively heavy computational workload when compared to OLDG.
To alleviate such the CLDG drawback, an efficient CLDG technique is proposed in this paper, and it is experimentally verified with a miniaturized MTF. The principle and procedure of the proposed CLDG is first explained with reference to the conventional ones. Then an elaborated model ship and experimental equipments for the down scale MTF are described. Finally, the closed loop degaussing performance is tested with a ferromagnetic model ship, which is equipped with fourteen degaussing coils and twelve onboard magnetic sensors.

Speaker: Mr Byungsu Kang (Kyungpook National University)

485 Tue-Af-Po2.24-07 [106]: Magnetic lens effect analysis of high temperature superconductors by finite element software

REBCO coated conductor has been regarded as one of the most viable high-temperature superconductor (HTS) options for next-generation high field magnets, mainly owing to its large in-field current carrying capacity and higher mechanical strength. To explore REBCO coil technology, a small-scale REBCO coil was designed, fabricated and tested. The REBCO coil has a winding inner diameter of 15 mm, outer diameter of 29 mm and length of 38 mm using layer-wound and no-insulation technology. The REBCO coil was tested in a 31.5 T background field, leading to a high field of 32.5 T. The no-insulation behaviors of the REBCO coil, including the charging delay and magnet constant, were investigated at 77 K and 4.2 K respectively. With the magnetic load from the high fields, we found the REBCO coil was mechanically damaged after the experiments, being two major patterns: peeling and bucking.

Speaker: Donghui Jiang (The High Magnetic Field Laboratory, Chinese Academy of Sciences)

Poster.pdf

Poster.pptx

486 Tue-Af-Po2.24-08 [107]: The Modeling and Numerical Simulation for Spherical Vector-Potential Coil

We propose a model of the spherical vector-potential coil, and we investigate the properties of the coil especially the uniform distribution of vector potential. The model is designed base on a spherical winding which made by the long flexible thin solenoid. When we apply a current to a very long solenoid coil, it creates a magnetic field within the coil only; there is no magnetic field outside the spherical vector-potential coil. On the other hand, outside of the loop, a vector potential is generated in the same direction parallel to a current-carrying conductor. The direction of vector potential is parallel to the spherical axis. In this manner, it points out the equation of similarity of the magnetic flux density and the vector potential. We have the motivation to create a uniform distribution of vector potential along the z-axis. The potential benefits of the uniform vector potential distribution can be applied to high-precision electronic measurements. Especially, the excellent properties of the vector potential, it generates an electric field without an electrode and no magnetic field. For detection, it can penetrate the conductive material to produce the desired secondary voltage and an electric field, and it can work well with a media such as corrosive blood. We numerically simulated the distribution of the vector potential in the sphere coil using MATLAB. The simulation method is based on Ampere's circuital law and analogy equations of the magnetic flux density and the vector potential. We also show the properties of the coil, such as secondary voltage, and transimpedance. The simulation result confirms that the vector potential is a uniform distribution.

Index Terms- Vector potential, Magnetic coil, Uniform distribution, Analogy method.

Speaker: Mrs Sarai Lekchaum (Iwate University)

Poster presentation.pdf

487 Tue-Af-Po2.24-09 [108]: Numerical Investigations on Enhanced-Performance Superconducting Linear Acceleration System for Pellet Injection

As the pellet injection for the fuel of the Large Helical Device (LHD), a pneumatic pellet injection is generally used. Although this method injects some pellets made of frozen hydrogen gas into a plasma of the LHD at the velocity of 1.2 km/s, the pellet does not reach the plasma core. For this reason, this method is not efficient in the fuel supply.

Recently, a novel pellet injection system by using a Superconducting Linear Acceleration (SLA) has been proposed to inject the ice pellets into the plasma core to supply the fuel in the LHD. In the system, a pellet container attaching the HTS films for acceleration and levitation is accelerated like the magnetic levitation train electromagnetically. Consequently, the estimation speed of the pellet injection system by the SLA becomes 5 km/s or more. However, it is not clear how much pellet speed can be obtained because the SLA has not yet applied to the pellet injection system.

In the previous study, we develop the FEM code for analyzing a shielding current density in an HTS film to investigate the feasibility of the SLA system. By using the code, the results of the computations show that the pellet container can be accelerated to 5 km/s or more by about 6.9 seconds by using the multiple coils for the acceleration. As a result, the required distance of the electromagnetic rails becomes about 21 km.

The purpose of the present study is to enhance the acceleration performance of the SLA system by locating another acceleration coil outside a conventional one. In addition, we investigate the influence of the experimental conditions of the SLA system on acceleration performance.

Speaker: Teruou Takayama (Yamagata University)

Tue-Af-Po2.24-09 [108].pdf

488 Tue-Af-Po2.24-10 [109]: A hybrid compensation method for ICT high voltage power supply

Insulated core transformer (ICT) electron accelerator offers many advantages including high efficiency of energy conversion, high-power output, low cost, and high reliability. It is a superior type of E-beam systems for the radiation processing applications in the low energy region (<1MeV). The ICT power supply is the core component of the electron accelerator. The structure of the ICT cores is segmented, and it results in large magnetic flux leakage at the gaps of the cores. Therefore, the output voltages of different disks are non-uniform, which highly affected the performance of the ICT power supply. In order to reduce the non-uniformity caused by the magnetic flux leakage, a hybrid compensation method with optimizing the turns of the secondary coils and using dummy primary coils mounted on the top of the ICT is presented in this paper. For an 800keV/50mA ICT power supply, the compensation scheme is designed, and the parameters are also optimized. The result shows the consistent output high voltage of each disk is achieved and the non-uniformity is better than 5% from no-load to full-load when the output high voltage is 800kV. This design effectively improves the uniformity of the electrical field distribution, increases the utilization of the rectifier components and reduces the size of the power supply.

Speaker: Can Jiang (Huazhong University of Science and Technology)

MT26_Tue-Af-Po2.24-10[109].pdf

489 Tue-Af-Po2.24-11 [110]: Operation parameter and economic effect study of the 1 MW HTS DC induction heater

In previous studies, the advantages of high temperature superconductor (HTS) DC induction heater (HIH) in energy saving and better heating quality had been provided. Compared with the conventional AC induction heater, the initial capital investment for HIH is high. The energy cost saved in the future is applied to pay the cost of HIH project. The key issue of the industrial application is to determine whether there is economic feasibility. In this paper, an economic analysis method on operation parameter of 1 MW HIH is proposed. The economic indexes to evaluate the economic performance include net present value (NPV), internal rate of return (IRR) and payback period (PBP). And the economic effect of different operation parameters of the HIH is also discussed, including four different system capacities, three solutions to solve peak torque issue and different aluminum billet parameters. The results show the PBP of 1 MW HIH investment is 2-3 years. The analysis results provide a reference to make the final decision for the industrial application and energy-saving renovation project of the HIH.

Speaker: Ping Yang (Shanghai Maritime University)

490 Tue-Af-Po2.24-12 [111]: High Coupling Characteristics of Resonance Coil for Superconducting Wireless Power Transfer

In this study, a wireless power transfer (WPT) technology with a superconductor was proposed. The proposed technology maximizes efficiency by applying superconducting characteristics to the resonance coil. To maximize the efficiency of the resonance coil during WPT, it is essential to consider the inductance and coupling coefficient (k). They are determined by the shape of the resonance coil.
As such, a rounded rectangular resonance coil was proposed and its characteristics were analyzed using the HFSS software. The shape of the proposed coil considered the electric current concentration due to curvature. The simulation analysis results showed that the cross-sectional area of the rounded rectangular resonance coil was approximately 21% larger than that of the circular resonance coil. In addition, the inductance and coupling coefficient (k) increased. Therefore, it was confirmed that the efficiency of the proposed coil was approximately 14% higher than that of the circular resonance coil.

This research was supported by Korea Electric Power corporation [grant number: R16XA01]
This work was supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIT) (No.2018R1A2B2004242)

Speaker: Hui-Seok Gu (Chosun University)

Presentation_Hui-Seok.pdf

Presentation_Hui-Seok.pptx

Tue-Af-Po2.25 - Novel and Other Applications III

Conveners: Rainer Meinke (AML Superconductivity and Magnetics), Dr Sasha Ishmael (Lupine Materials and Technology)

491 Tue-Af-Po2.25-01 [112]: Structure Design and Performance Analysis of Superconducting DC Energy Transfer Line

Transmission integration of power and the gas could be realized If a superconducting DC cable uses liquefied natural gas (liquefaction temperature: 110K) or liquid hydrogen (liquefaction temperature: 27K) as the cooling medium. Therefore, the efficiency and reliability of the liquefied natural gas (LNG) integrated energy transfer system can be improved using superconducting DC energy transfer line. This paper presents principles in designing the superconducting DC energy transfer line. The design scheme of superconducting DC energy transmission line is given. The structure of superconducting DC cable part is conductor on round core cable (CORC) wound by the second generation (2G) high-temperature Superconducting (HTS) tapes. The twist angle and relative position of different tape layers affect the distribution of transmission current, which further impacts the distribution of magnetic field. This paper uses finite element method to simulate such effect and the effect of external shielding layer on magnetic field distribution. Based on the simulation results, the superconducting cable is optimized with the aim of maximizing critical current. Considering the transmission principle of LNG, the theoretical efficiency, reliability and cost of the whole energy transfer system are calculated. And the optimal design of superconducting DC energy transfer line with the best comprehensive performance is given based on the calculations.

Speaker: Mr Peng Xue (Tsinghua University)

Poster2.pdf

492 Tue-Af-Po2.25-02 [113]: Feasibility study for the application of 154 kV smart HTS cables to a power system

In South Korea, Korea Electrotechnology Research Institute (KERI) has developed 154 kV smart HTS cables since 2017. The smart HTS cable has a fault current limiting function. There are two types under development, resistive and inductive.
When the HTS conducting layer of a resistive smart HTS cable is quenched by a large fault current flowing to the HTS layer, the resistance of the cable increases and limits the fault current. The resistive type has disadvantages that it has not enough short circuit capacity required by a protective coordination of power systems.
In other hand, the inductive smart HTS cable is more useful to operate in power system. The inductive smart HTS cable maintains the general shape of a conventional HTS cable and places a high permeability material such as an iron core on the outside. When a large fault current flows into the inductive smart HTS cable, the current of the shield layer disappears because of the quenching of the shield layer. At this time, the fault current is limited by an inductive reactance generated by interlinkages between the magnetic field emitted to the outside of the cable and the high permeability material.
We focus on the application of the inductive smart HTS cable. This paper presents the feasibility to apply 154 kV smart HTS cables to a real power transmission system. We propose a concept of smart superconductivity power systems applying 154 kV smart HTS cables. 154 kV smart HTS cables can replace 345 kV conventional cables. In general 154 kV power systems under 345 kV substations are split each other due to a fault current problem. If the smart HTS cable is applied to incoming 154 kV transmission lines of a 345 kV substation, the HTS cable can limit fault currents and the split 154 kV systems can be interconnected and operated as a power system. The proposed smart superconducting power system can dramatically improve the reliability and stability of a power system.

Speaker: Seung Ryul Lee (KERI)

493 Tue-Af-Po2.25-03 [114]: Sensitivity Analysis of Parameters in Transverse Flux Induction Heating Model

Compared with traditional open fire heating, induction heating has the advantages of high efficiency, energy saving and environmental protection. There are two basic forms of induction heating: longitudinal flux induction heating (LFIH) and transverse flux induction heating (TFIH). The magnetic induction line produced by TFIH is perpendicular to the heated workpiece, which is suitable for heating strips with small cross-section area. With the development of heat treatment industry, the heating treatment of metal strips has become a trend in the industry. Therefore, TFIH technology is widely used. Although the technology of TFIH has been greatly developed, but the temperature distribution uniformity of the strip surface along the width direction of the strip at the outlet of the heater (Trel) is poor. The TFIH model is used to simulate and analyze the heating process of the strip by using the 3D finite element method (FEM). The four parameters of the model, include the effective value and frequency of exciting current, the structure of heater coil and the moving speed of the strip, have great influence on the Trel. However, the influence of the four parameters changing on Trel has not been sorted so far. Sensitivity analysis is used to evaluate the influence of model parameters changing on the results of model calculation qualitatively or quantitatively. Sensitivity analysis involves two methods, local sensitivity analysis (LSA) and global sensitivity analysis (GSA). In this paper, morris method of GSA is used to analyze the influence of the four parameters changing on Trel. The sensitivity values of the four parameters are sorted, which can provide an optimal priority for the optimization of TFIH model parameters, so that the strip surface temperature distribution at the heater outlet can be more uniform.

Speaker: Dr Chengcheng Liu (Hebei University of Technology)

WujianchengposterTueAfPo22503.pdf

WujianchengposterTueAfPo22503.pptx

494 Tue-Af-Po2.25-04 [115]: A Finite Element Study on the Distribution and Variation of the Eddy Current in Electromagnetic Sheet Free Bulging

Electromagnetic forming is a technology that employed electromagnetic force to accomplish the deformation of the metal with high conductivity. It is reported that the improved formability and reduced spring back are observed during the EMF. Combined other advantages such as good control performance and contact-less, EMF technology draw more attentions as a promising solution for the room temperature processing of lightweight alloy.
EMF is a complicated process which involves the coupling effect of the multi-field. Many processing parameters will influence the forming result. Among those, the excitation frequency is one of the most important parameters. The distribution of the eddy current and the magnetic pressure in the workpiece is directly decided by the frequency of the excitation current. In consequence, the forming results of the EMF are also influenced. Most of the researchers related the effect of the frequency to the skin depth in the workpiece. However, the relation between the optimum forming frequency and the thickness of the workpiece is still in dispute.
The distribution and changes of the eddy current in the work-piece during the EMF process is not exactly the same as that in infinite plate when Sine uniform planar electromagnetic wave incidences as the thickness of the sheet is limit. The skin depth cannot describe the distribution of the eddy current in EMF accurately. In this paper, with the employment of a full coupling simulation model, the distribution of the induced current with different charging frequencies during electromagnetic sheet free bulging are analyzed in detail, and the magnetic pressure is calculated. Based on these analysis, the research on the relations between the forming frequency influence and the forming result will be developed.

Speaker: Dr Lantao Huang (Xiamen University)

495 Tue-Af-Po2.25-05 [116]: Effect of the iron core air gap structure of superconducting DC induction heater on the heating of aluminium billet

In aluminium manufacturing plants typical billets having 200 mm diameter and 1000 mm height are pre-heated to a temperature of 723.15–773.15 K in order to soften the metal before it is pressed through the extruder. Due to the similar physical properties of aluminium and copper the efficiency of these heaters is in the order of 50%. In order to improve the efficiency superconducting DC induction heating has been proposed. The idea is to force the billet to rotate in a static magnetic field produced by a DC superconducting magnet with iron core. Since a static superconducting magnet has no losses, the efficiency of the system is the efficiency of the motor used. The magnetic field profile generated by different core air gap structures with a same DC superconducting magnet is different. The heating time and temperature uniformity for the same rotating speed will be different when the aluminium billet is heated to a certain temperature. Therefore, it is necessary to study the influence of different air gap structures on the heating of the aluminium billet.
In this work, the temperature distributions arising from the magnetic field profile produced by a given superconducting magnet under different air gap structure of iron core are reported. The heating time and temperature uniformity vary with the rotational speed are investigated. The two end faces of the iron core are trapezoidal and semi-circular. The radius and length of aluminium billet are 100 mm and 1000 mm respectively. Considering the cryogenic system and the thermal insulation, the distance d between the inner surface of the coils and iron yoke is 85 mm and the distance between the surface of the aluminium billet and iron yoke is 50 mm. Finally we discuss our results in terms of the effect of core air gap structure on heating of aluminium billet and design optimization method of core air gap structure.

Speaker: Mr Xufeng Yan (Beijing Jiaotong University)

496 Tue-Af-Po2.25-08 [118]: A Novel Trenchless Detection Technology Based on Transient Electromagnetic Method for Power Poles

In the project construction and daily maintenance of overhead power distribution lines, it is necessary to know the actual situation of the auxiliary parts for power polses, such as chassis, chuck and puller, to prevent the poles from pulling up, sinking and lodging. But due to the inconvenient excavation of power poles or the large amount of excavation work, trenchless detection technology is put forward to detect the status of chassis, chuck and puller underground, and provides a research opportunity for electromagnetic detection methods. This paper proposes a trenchless detection method based on transient electromagnetic method, which realizes underground detection by transmitting, receiving and processing electromagnetic signals generated by underground conductors. In this paper, a prototype of transient electromagnetic detector is designed on the base of theoretical analysis and mathematical modeling for the chassis, chuck and puller underground. The prototype consists of a transmitting power supply, a transmitting coil, a receiving coil and a signal processor.The transmitting power supply generates a flat-top pulsed current with a high change rate of 20 A/us, thus enhancing the magnetic field signal returned from the measured object.The transmitting coil and receiving coil are the same solenoid structure with parameters of 40 turns and 300mm diameter. In order to reduce the influence of mutual inductance between transmitting coil and receiving coil, two coil are placed side by side. The prototype is tested with the chuck 1.5 meters deep, chassis 3 meters deep and puller respectively in the field of practical application. Through the analysis of the experimental results of multiple test objects, the transient electromagnetic detector can realize the detection as designed, and the precision of measurement reaches 90%.

Speaker: Jun Zhou (Huazhong University of Science and Technology)

Tue-Af-Po2.25-08.pdf

497 Tue-Af-Po2.25-09 [119]: A Novel Magnetic Gear with Unequal Halbach Array and Spoke Permanent Magnets

Due to low acoustic noise, low vibrations, reduced maintenance and inherent overload protection, magnetic gear (MG) has been extensively used in many industrial applications for transmitting torques and adjusting speeds. However, the biggest shortcoming of MGs is their poor torque densities. Although several attempts have been conducted for improving their torque density, such as optimizing the design parameters and adopting bulk high temperature superconductors (HTS) to provide stronger magnetic field, they are still far away from satisfying the demands of industrial applications. In order to improve the torque density of MG, this paper proposes a novel MG with unequal Halbach Arrays on the inner rotor and spoke permanent magnets on the outer rotor. On the inner rotor, a new arrangement of Halbach array which is “unequal” on magnetization direction and arc length of each segment is proposed. Both fundamental flux density and total harmonic distortion (THD) of “unequal” Halbach array is better than the “equal” one. On the outer rotor, the permanent magnets are spoke structure and tangential magnetization direction, and a larger per-pole flux density can be obtained in the air gap. The two-dimensional finite element method is used for simulating the proposed model. The magnetic field and electromagnetic torque of the magnetic gear are calculated. Compared with the conventional magnetic gear, the results show that the torque transmission capability of the proposed magnetic gear can be substantially improved by about twice time.

Speaker: Qian Wang (Huazhong University of Science and Technology)

MT-26(ID-622).pdf

498 Tue-Af-Po2.25-10 [120]: A Novel Slotted Magnetic Gear with Spoke and Inset Permanent Magnets

Compared with mechanical gear, Magnetic gear has the advantage of low acoustic noise, low vibrations, reduced maintenance and inherent overload protection. Although magnetic gears have many merits, the utilization of PMs and torque density of magnetic gears are extremely low due to the influence of parallel-axis topologies. In recent years, coaxial magnetic gear (CMG) has been put forward, and the utilization of PMs are obviously improved. In order to reduce material costs and increase the torque density, it is still very necessary to research the magnetic gear with simple structure and high torque density. In this paper, a novel structure of magnetic gear is proposed, which has higher torque density and mechanical properties than conventional magnetic gears. The permanent magnets (PMs) of the outer rotor are spoked and magnetized along the tangential direction. The PMs of inner rotor are the surface-mount type and magnetized in the radial direction. The PMs are fixed in the inner and outer rotors’ iron yoke so as to keep the PMs from falling off during the rotation. In order to reduce the usage of iron, it is considered to notch slots on the outer rotor. The two-dimensional finite element method is used for simulating the proposed model. The magnetic field and electromagnetic torque of the magnetic gear are calculated. Finally, a prototype of a CMG is built and tested, and the experimental results show that the torque transmission capability of the CMG can be substantially improved, and its transmission efficiency is above 90%. When the load torque reaches 116.5N·m, the effective length of the prototype corresponds to the torque density is 135.07kN·m/m3.

Speaker: Qian Wang (Huazhong University of Science and Technology)

MT-26(ID-623).pdf

499 Tue-Af-Po2.25-12 [121]: Detection of Underground Tower Base for Distribution Transmission Network Based on Transient Electromagnetic Method

In the construction of distribution transmission network, in order to check whether the poles and towers are built as required, it is necessary to detect the underground tower base which is made up of concrete-filled steel tubular. The transient electromagnetic method can obtain location information of underground metals when they induced secondary induced voltage on receiving coil caused by eddy current effect of these metals. It is efficient and non-destructive which can be used in the detection of underground base.
However, due to circuit transient process and electromagnetic coupling, signal collected on receiving coil not only has secondary induced voltage, but also mixes primary induced voltage caused by mutual induction between transmit coil and receiving coil. Since the magnitude of primary induced voltage is much larger than secondary induced voltage, accurate detection becomes rather difficult.
In this paper, a hardware decoupling method using decoupling coil and precise potentiometer is proposed. The decoupling coil and transmit coil are coaxially reversed winded but independent to each other. Meanwhile, decoupling coil and precise potentiometer are connected to the receiving coil. By fine-tuning the precise potentiometer, the output voltage of the decoupling circuit counteracts to the primary induced voltage so that the acquired signal on receiving coil is a pure secondary induced voltage waveform.
A detection system is designed according to the analysis of the transient electromagnetic process. Finite element analysis method is adopted to establish equivalent detection model and obtains the spatial induced field distributions. Experimental results of the prototype show that acquisition waveform on receiving coil is generated by eddy current effect of underground base and compared with the feedback waveform of standard underground base, the proposed method can verify whether the poles and towers of distribution network is buried as required.

Speaker: Xiao Fang

Tue-Af-Po2.25-12 [121]何州.pdf

Tue-Af-Po2.25-12 [121]何州.pptx

Tue-Af-Spe1 - Special Session: Magnet Technology and Conductor for Future High-field Applications

The Special session will discuss status, magnet and conductor technology needs for future very high magnetic field applications. Possible potentially-commercial or large-volume applications include imaging, rotating machinery, fusion and accelerator technology. In these applications, high fields promise the system performance improvements beyond magnetic field-generating assembly, compact devices and reduced weight. Several presentations will address status of the high-field, >10 tesla, ReBCO, BSCCO and TMC conductors. HTS and TMC conductor needs will be discussed including technical characteristics and manufacturing demands. The magnet technology challenges include but not limited to interactions with the system components, high forces and stresses, quench protection, operation at high currents, high voltage insulation, manufacturing issues.

Convener: Joseph Minervini (MIT)

500 Introduction

501 Ultra-high Field Superconducting Magnets for MRI

Speaker: Michael Parizh (GE Global Research)

Tue-Af-Spe1-02 - Ultra-high field MRI magnets - Parizh.pdf

502 Ultra-high-field Fusion - CFS

Speaker: Zach Hartwig (MIT)

MT26_UltraHighFieldFusion_Hartwig.pdf

503 Advantages and Challenges in High-field Rotating Machinery

Speaker: Mathias Noe (Karlsruhe Institute of Technology)

Tue-Af-Spe1-04-Noe-Final.pdf

504 High-field Accelerator Magnets

Speaker: Bernardo Bordini (CERN)

2019 9 24 MT 26 Special Session.pdf

505 TMC - A Low-cost High Field Conductor

Speaker: Mr Bernd Seeber (scMetrology)

SEEBER-MT26-TMC-190921.pdf

506 Status of High-field ReBCO Conductor

Speaker: Satoshi Awaji (Tohoku University)

2019MT26_REBCO.pdf

507 Conductor Technology Needs

Speaker: Mike Sumption (The Ohio State University)

508 Key Issues in HTS Magnet and Conductor Technology Toward Various Applications

Speaker: Naoyuki Amemiya (Kyoto University)

Tue-Af-Spe1-09-Amemiya.pdf

509 Magnet Technology Development for High-field Accelerator Magnets

Speaker: Ramesh Gupta (BNL)

Special session tuesday - gupta.pdf

Special session tuesday - gupta.pptx

510 Questions & Discussion

Wednesday 25 September

07:50 Registration Open (7:00 AM - 6:00 PM)

07:55 Exhibits Open (9:00 AM - 4:00 PM)

For a list of Exhibitors, please visit: https://mt26.triumf.ca/#exhibitors.

Plenary: Alessandro Bonito-Oliva (F4E) - sponsored by ASG Superconductors

Convener: Cesar Luongo (ITER Organization)

511 Wed-Mo-PL3-01: Toward Completion and Delivery of the First EU ITER Magnets

The plasma confinement of the International Tokamak Experimental Rector (ITER) is provided by the magnetic field generated by 18 toroidal field (TF) coils while 6 poloidal field (PF) coils have the function to shape and pre-heat the plasma. Fusion for Energy (F4E), the European Domestic Agency for ITER, is responsible for the supply of 10 TFC and 5 PFC to the ITER project. The ITER Organization (IO) team is instead responsible for the design of such coils as well for the coordination of the activities of the different Domestic Agencies (DA) producing the different components for the Tokamak.
The PF coils utilize NbTi Cable-in-Conduit-Conductor and have different diameter ranging between 7 and 25 meters and a weight up to 400 tons. Regarding the PF coils produced by F4E, so far one has been completed by the the Institute of Plasma Physics Chinese Academy Of Sciences (ASIPP) under a collaboration agreement with F4E. The other 4 PF coils are being produced at the ITER site (Cadarache) under F4E supervision: the first PF coil (PF5) will be completed by June 2020 while the last coil (PF3) will be ready be the end of 2023. The TF coils utilize a Nb3Sn conductor and are manufactured with the “Wind, React & Transfer” method. The first TF coil is close to its completion and it will be delivered to ITER by begin of 2020, while the others TF coils will follow with a rate of about one every 3-4 months. In this article we will report on both PF and TF coils, in particular on the different utilized manufacturing strategies, the main challenges faced so far and the results obtained.

Speaker: Alessandro Bonito-Oliva (F4E)

MT26-bonito oliva -plenary-.pdf

Young Scientist Plenary

Convener: Tiina Salmi (Tampere University of Technology, Finland)

512 Introduction

513 Wed-Mo-PL4-01: Mitigation of Shielding-current-induced Field in a Magnet Wound with Coated Conductors for Accelerator Systems

Speaker: Dr Yusuke Sogabe (Kyoto University)

Wed-Mo-PL4-01_Sogabe.pptx

514 Wed-Mo-PL4-02: Superconducting Magnet Testing: The Art of Giving Feedback on Magnet Design

Speaker: Franco Julio Mangiarotti (CERN)

Wed-Mo-PL4-02_FJMangiarotti_SuperconductingMagnetTesting.pdf

Wed-Mo-PL4-02_FJMangiarotti_SuperconductingMagnetTesting.pptx

515 Wed-Mo-PL4-03: Bi-2212 High Field Magnet Development

Speakers: Ernesto Bosque (National High Magnetic Field Laboratory), Dr Ernesto Bosque (Applied Superconductivity Center, National High Magnetic Field Laboratory, Florida State University)

190925 Bosque Plenary.pdf

516 Wed-Mo-PL4-04: Electro-mechanical Characterization of HTS Tapes and Conductors for the next Generation High-field Magnets

Speaker: Federica Pierro (Tufts University)

Pierro_YS_Plenary.pdf

Pierro_YS_Plenary.pptx

517 Wed-Mo-PL4-05: Flux Pumps

Speaker: James Gawith (University of Cambridge)

Flux Pumps.pdf

Flux Pumps.pptx

518 Wed-Mo-PL4-06:Development of Superconducting Undulators

Speaker: Dr Ibrahim Kesgin (Argonne National Laboratory)

09:30 Coffee Break (during Poster Sessions)

Wed-Mo-Po3.01 - Fusion V: DDT and DEMO

Conveners: Neil Mitchell (ITER Organization), Simonetta Turtu' (ENEA)

519 Wed-Mo-Po3.01-01 [1]: Conceptual Design and Analysis of the DDT PF Coil System

The DDT (Divertor Tokamak Test) machine is under construction at the Frascati research center of ENEA and is aimed to investigate the possible divertor solutions for the management of power and particles exhaust for the EU-DEMO tokamak. Its Poloidal Field coil system is constituted by 6 magnets, identical in pairs as the machine is foreseen to be fully symmetric to allow for plasma configuration in the single null (SN) as well as in the double null (DN) scenarios. The PF1 and PF6, will be wound by Cable-in-Conduit conductors (CICC) cabled with Nb3Sn strands, answering to the request of magnetic fields up to about 8 T, as well as to reduce their occupancy in favor of mechanical structures and to leave room for the large ports at the polar regions, while the PF2/5 and PF3/4 are designed with NbTi CICCs, being the project request in terms of field less stringent.
In this paper, the last progress in the conceptual design and analyses of the 6 Poloidal Field winding packs are illustrated, and the technical solutions to satisfy the high flexibility of the DDT tokamak with respect to the various operative scenarios foreseen in the present fusion experimental project are discussed.

Speaker: Turtu' Simonetta (ENEA)

520 Wed-Mo-Po3.01-02 [2]: Structural analyses of the Toroidal Field magnet system of the DTT

The Divertor Tokamak Test facility (DTT) is an experimental tokamak machine to be built in Frascati, Italy, at the ENEA research centre. During its development, the DTT has gone through several important design updates. Developing a rigorous finite element methodology to evaluate the performance of all its components has thus been a critical part of the verification phase of each new design iteration. This work summarises the outcome of the structural analyses that support the current design of the Toroidal Field (TF) magnet system, including the superconducting winding pack ($Nb_3Sn$), the casing structure and all of the inter-coil structures. Given the high complexity of the 3D structure to reproduce, some modelling simplifications were mandatory to solve the problem. We hereby describe the finally adopted methodology next to all the motivations we examined to make sure the results were sound and reliable from an engineering point of view.

Speaker: Mr Gherardo Romanelli (ENEA)

521 Wed-Mo-Po3.01-03 [3]: Optimization of the fast discharge time constant for the DTT Toroidal Field magnets

In the EU DEMO fusion reactor, currently in its pre-conceptual design phase, the long plasma pulse duration and the large thermal loads represent a challenge for the power exhaust, so that a new, robust design of the divertor is needed. For this reason, several DEMO-relevant divertor solutions will be tested in the Divertor Tokamak Test (DTT) facility that will be built in Italy. It will be a fully superconductive compact tokamak, very flexible in terms of plasma configurations.
The 18 Toroidal Field (TF) magnets, cooled by forced-flow supercritical helium at 4.5 K, must then be reliable components, capable to cope with several different operating scenarios. To protect them (and the entire machine), the possibility of a fast discharge of their magnetic energy by means of dump resistors is foreseen.
The 4C code, aimed at the analysis of thermal-hydraulic transients in superconducting magnets, is used here to develop a detailed model of the DTT TF coils. The model will be used to analyse parametrically the fast discharge and optimize the dump time constant. The latter will indeed be limited by two main constraints: on the one hand it must be sufficiently large not to develop a voltage that can damage the electrical insulation, with a serious impact on safety and reliability aspects which are fundamental for an expensive nuclear fusion experiment; on the other hand, the heat deposited by AC losses in both cable and supporting structures during the current and magnetic field variation can lead to a quench, so that it is desirable to reduce the transport current as fast as possible to reduce the hot spot temperature and thus the thermo-mechanical stresses possibly damaging the cable (and, again, impacting on the magnet system reliability). An optimum range for the dump time constant is then proposed as a guideline to the magnet system designers.

Speaker: Roberto Zanino (politecnico di torino)

DTT_TF_poster_MT2019_v1.pdf

522 Wed-Mo-Po3.01-04 [4]: Structural assessment of the DTT Poloidal Field Coil system

In the context of the European Fusion Roadmap, the Divertor Tokamak Test (DTT) experimental reactor is intended to investigate alternative divertor configurations in view of the EU-DEMO power exhaust handling necessities, and it is to be built at the Frascati ENEA research centre in Italy. The six poloidal field coils of the tokamak are responsible for the plasma shape and equilibrium, and numerous steps were taken to obtain a design that is magnetically consistent with the plasma requirements and structurally compliant with the chosen failure criterion. All the poloidal field magnets are superconductive and comprised of $\rm{NbTi}$, except for the uppermost and lowermost coils which feature $\rm{Nb_3Sn}$ as superconducting material. This work presents the structural assessment that has been performed on the poloidal field coil system, taking into account the cooldown process, the energisation to operating conditions and fatigue. Finite Element Analysis has been employed as the principal means of investigation, while some classical results from the theory of Elasticity corroborate the evaluations.

Speaker: Mr Lorenzo Zoboli (ENEA, Superconductivity section, C.R. Frascati, Italy; Department of Civil Engineering and Computer Science, University of Rome Tor Vergata)

523 Wed-Mo-Po3.01-05 [5]: Magnetostructural calculations and design study of the DTT central solenoid

The “Divertor Tokamak Test” facility, DTT, is a project of an experimental tokamak reactor developed in Italy, in the framework of the European Fusion Roadmap.
This work presents the magnetic and the structural assessment of the performance of the DTT central solenoid.
The CS is the core magnet of the poloidal system and generates the magnetic flux needed to induce the plasma current.
This magnet is composed of a stack of six layer-wound independently energized modules, comprised of Nb3Sn Cable-in-Conduit Conductors.
To optimize the amount of superconductive material, each module is divided into two submodules. The innermost submodule operates in a range of 10/14 T, while the outer one at 10/6 T.
The objective of the design process is to obtain a coil that is capable of providing the required magnetic performance while being structurally compliant.
To address this problem, an analytical assessment has been carried out and a thoroughly parametrical FEM model has been implemented.

Speakers: Dr Lorenzo Giannini (ICAS), Dr Luigi Muzzi (ENEA)

LorenzoGiannini_MT-26.pdf

524 Wed-Mo-Po3.01-06 [6]: CEA Broad Design Studies on EU Demo TF, CS and PF Magnets Systems

In the framework of EU design activities for dimensioning the future fusion DEMOnstration reactor (DEMO), extensive analyses were conducted in EUROfusion context, aiming at ultimately defining the design of the DEMO magnets system. In this objective CEA proposes design for all cryomagnetic systems: Toroidal Field (TF) coils, Central Solenoid (CS) and Poloidal Field (PF) coils.
In the last DEMO reactor baseline, designs for all three systems were investigated with pre-dimensioning macroscopic CEA tools, resulting in many possible design options.
Broad parametric investigations, conducted on the three systems, will be presented, highlighting the merits of the selected afore-mentioned open choices. For example, regarding TF system, several pancake-winding patterns can be envisaged while complying with machine-level constrains. Central design parameters are varied (e.g. mechanical stress, maximum conductor current, temperature margin…) for which each design option shows a specific sensitivity. Parametric studies will not only address variables but also TF pancake-wound design concepts variants: presence or absence of radial plates. Taking into account the DEMO baseline, the influence of important inputs (maximum field, operating temperature…) accuracy (macroscopic models, detailed numerical codes…) on the TF design features will also be quantified, with considerations on design strategy.
On CS system influence of e.g. dimensions (height, external radius), conductor material (LTS versus HTS), design criteria (e.g. temperature margin, stress…) or mechanical model (static, fatigue…) are investigated to identify a domain of compliance around the reference design for DEMO configurations. And finally PF system will also be parametrically explored especially regarding the aspect ratio of PF coils winding.
The outcomes of this exhaustive broad exploration will be exposed and discussion will be led on pros and cons of each option.
Finally recommendations will be issued both for choosing reference design for the three magnetic systems and for the definition of methodologies to be followed for design purposes.

Speaker: Louis Zani (CEA)

MT26_ZANI_poster_final.pdf

MT26_ZANI_poster_final.pptx

525 Wed-Mo-Po3.01-07 [7]: Design and analysis of DEMO PF coils

The design of DEMO PF coils is proposed and analysed based on the requirements defined by the EUROfusion 2019 DEMO baseline. Two types of forced flow cable-in-conduit conductors are used: NbTi with high void fraction and Nb3Sn with a dedicated cooling channel. The design addresses the dimensioning of the winding pack, the electromagnetic field calculations, stress analysis and thermal hydraulic and quench propagation analysis. The amount of structural material depends mainly on the hoop load. This is verified by fatigue stress analysis. The amount of superconductor, copper and cable void fraction (or cross-section of cooling channel) are determined by the temperature margin and quench analysis. The AC loss is modelled with conservative assumptions. The new design fulfils the design criteria set by the 2019 DEMO baseline. For some coils, the comparison of NbTi and Nb3Sn design options suggest more efficient allocation of structural and superconducting material in the latter case. It is also verified that temperature margin is always above 1.5 K.

Speaker: Dr Mithlesh Kumar (EPFL-SPC)

DEMO_PF_MT26_Po30107_ver1.pdf

DEMO_PF_MT26_Po30107_ver1.pptx

526 Wed-Mo-Po3.01-08 [8]: EUROfusion DEMO Tokamak, Inter-Layer Joint for Toroidal Field Coil

The Swiss Plasma Center (SPC) has developed a layout of Toroidal Field (TF) coil for EUROfusion DEMO tokamak, basing on a reference baseline of 2015. Each TF coil winding pack is wound with graded Nb3Sn conductors and consists of 12 single layers, connected in series by means of inter-layer joints.
The design of inter-layer joints takes into account the react-and-wind (R&W) manufacturing technique for fabrication of TF coil winding pack, i.e. the inter-layer joint is prepared with use of two already heat treated Nb3Sn conductors. The development, preparation and test of inter-layer joint at SPC is performed in frame of R&D program for TF coil of EUROfusion DEMO tokamak.
The high-grade Nb3Sn TF conductor, operating at 63 kA and 12.4 T (Tcs >6.5 K) was tested at SPC, and afterwards was used for fabrication of inter-layer joint. The developed TF inter-layer joint is an “overlap-type” joint, which can be fit within the dimensions of TF winding pack. Each end of two conductors is copper cladded by a plasma-spraying technique and bonded together over the surfaces of cladded copper by a high-frequency inductor.
This paper describes the design of inter-layer joint, its manufacture and the test results obtained at SPC in the SULTAN test facility.

Speaker: Mr Boris Stepanov (EPFL-SPC)

BS_DEMO Joint Po3.01-08_v3.pdf

BS_DEMO Joint Po3.01-08_v3.pptx

527 Wed-Mo-Po3.01-09 [9]: Presentation withdrawn

528 Wed-Mo-Po3.01-10 [10]: Progress in the Design of a Hybrid HTS-Nb3Sn-NbTi Central Solenoid for the EU DEMO

State-of-the-art high field solenoids make use of hybrid designs exploiting the superior high field performance of High Temperature Superconductors (HTS) in the innermost region. The benefits of a hybrid Central Solenoid in a pulsed tokamak like DEMO can be two-fold: either to reduce its outer radius (which would result in a reduced overall size and cost of the tokamak), or to increase the generated magnetic flux (which could extend the plasma burn time and possibly increase the power plant efficiency). In the framework of the pre-conceptual design studies for DEMO coordinated by EUROfusion, a hybrid Central Solenoid is proposed based on ten layer-wound sub-coils using HTS, Nb3Sn, and Nb-Ti conductors respectively for the high, medium, and low field sections. The design exploits the flexibility of layer winding by grading both the superconductor and the stainless steel cross sections in each sub-coil, which has the potential for significant space and cost savings. Mechanical analyses have identified fatigue as the main design driver for the EU DEMO Central Solenoid. Possible alternatives to reduce the sensitivity of the proposed design to fatigue are currently under investigation.
This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014-2018 under grant agreement No 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission.

Speaker: Xabier Sarasola (EPFL)

DEMO_CS_poster_MT26_v0.pdf

Wed-Mo-Po3.02 - Fusion VI: Conductors for Fusion & New Designs

Conveners: Andries den Ouden (Radboud University), Arnaud Pascal Foussat (CERN)

529 Wed-Mo-Po3.02-01 [11]: Conceptual Design of Compact CS Insert for HTS Spherical Tokamak FNSF

Second-generation high temperature superconductors (HTS) are available for producing >25 T at magnet bore compared to 16 T for low temperature superconductors (LTS) magnets proposed in recent studies of the Fusion Nuclear Science Facility (FNSF), thus enabling higher fusion power density and a smaller device size. High current density is required for engineering design of the next step FNSF to allow space for interior plasma components. PPPL is teaming up with US industry in developing the compact high field central solenoid (CS) insert design made with high current transposed cable comprised of mechanically enhanced Bi-2212 wires. This collaboration is aimed at demonstrating the feasibility of producing a small (a few centimeters diameter) but high field HTS solenoid insert that meets the challenging fast current ramp rate and low AC loss requirements while maintaining high current density needed for the low aspect ratio ST FNSF pilot plant design.

HTS magnets with high current density are particularly attractive in reducing the size of a device, beneficial for low-aspect-ratio compact tokamaks, due to their space constraints. Successful HTS magnet development may enable the design of smaller and cheaper fusion “pilot plants” with a mission of demonstrating net electricity. This paper focuses on exploring HTS CS insert design options and prototype coil development using mechanically enhanced Bi-2212 wires.

The prototyping and small coil testing plan developed will demonstrate maturity of the enabling Bi-2212 wire technology desired in ~20T high field prototype coil for fusion pilot plants. The goal is to demonstrate design of small CS insert solenoid coil for plasma startup while maintaining a low fabrication cost, for solenoid coil winding using directly commercially available Bismuth strontium calcium copper oxide (Bi-2212) strands to achieve 20T high field on coil and 1-2 Wb flux swing therefore, validating maturity for compact fusion magnet design, prototyping and testing. The plan includes production of small Bi-2212 of solenoid prototype coil, and prototype coil testing.

Speaker: Yuhu Zhai (Princeton Plasma Physics Laboratory)

530 Wed-Mo-Po3.02-02 [12]: The general appearance of the superconducting magnet system for the Gas-Dynamic Multimirror Trap

The goal of the Gas-Dynamic Multimirror Trap (GDMT) project is to create a multi-functional experimental facility and lay the groundwork for future development of fusion applications of open-ended magnetic plasma confinement systems with linear axisymmetric configuration. Among the most promising plasma confinement concepts to be studied on this facility are the diamagnetic plasma confinement mode and plasma flux suppression by multimirror and helical magnetic sections [1].
The conceptual design of the GDMT installation is under development and assumes a modular construction principle, which allows the installation to satisfy the requirements of the experimental program. Regarding the magnetic system of GDMT, this means that it must be built from several types of universal modules, which could be assembled in a particular order according to demands of the experiment. By utilizing this approach and controlling the current in each of superconducting coils, which make up the modules, it is possible to facilitate a transition from one magnetic configuration to another. The confinement region of the magnetic system is a several meters long solenoid with diameter of magnetic coils ~ 1.3m and axially uniform magnetic field. A certain experimental scenario requires that the magnetic field be ramped up from 0.3 to 3 T within 5 seconds, which implies than a special low AC-loss superconducting cable must be chosen for this part of the installation. In this paper we present the requirements for magnetic field distribution, preliminary calculations and a general appearance of the superconducting magnet system, along with an assessment of the parameters of superconducting materials necessary to create such a system.

[1]. P.A. Bagryansky, A.D. Beklemishev, V.V. Postupaev 2019 J Fusion Energ 38 162

Speakers: Dr Dmitry Yakovlev (Budker Institute of Nuclear Physics), Prof. Vitaly Vysotsky (Russian Scientific R&D Cable Institute)

GDMT poster 02.pdf

GDMT poster 02.pptx

531 Wed-Mo-Po3.02-03 [13]: An Alternative Conductor Design for the K-DEMO Toroidal Field Coils

The conceptual design for the superconducting coils of the K-DEMO tokamak has been proposed and continues to be updated. The toroidal field coils rely on Nb3Sn technology with new generation high Jc strand. The design is that of a cable-in-conduit conductor (CICC) consisting of multistage Nb3Sn cable inside a rectangular stainless steel jacket. There are huge Lorentz forces on the cable due to the large currents and magnetic field. A large aspect ratio for the rectangular conductor is proposed to reduce the accumulative pressure on the cable strands. Further increases in the aspect ratio would be advantageous. However, manufacturing such a conductor in a conventional way would be difficult as compaction of a cable to extreme aspect ratios damages the strands. To overcome this limitation, an alternate cable design for the conductor is proposed. The perceived advantages and expected difficulties and required complications of the design are discussed.

Speaker: Dr Soun Pil Kwon (NFRI)

alt K-DEMO HF CICC.pdf

532 Wed-Mo-Po3.02-04 [14]: Development of high-current density HTS STARS conductor for the next generation helical fusion device

Conceptual design studies of the helical fusion reactor FFHR-d1 are progressing at National Institute for Fusion Science (NIFS) for realizing steady-state fusion energy production. The continuously wound helical coils have the major radius R of 15.6 m, four times that of the presently working Large Helical Device (LHD) with R = 3.9 m. The High-Temperature Superconducting (HTS) large-current capacity conductor, named STARS (Stacked Tapes Assembled in Rigid Structure), has been developed to be applied to the helical coils of FFHR-d1. The operation condition is 100 kA current at 14 T magnetic field and 20 K temperature. The current density of the conductor is set at 25 A/mm2.
At NIFS and in the Japanese fusion community, discussion about the post-LHD project has started so that it would be implemented after completing the LHD project in about ten years. One of the candidates is to build a new middle-sized helical device (R = 3.3 m as the present reference) with a higher magnetic field associated with a magnetic configuration optimizing that of LHD. The HTS conductor is being considered to be applied to the helical coils of this device having the target condition of 18 kA at ~10 T and 20 K. The current density is presently set at 80 A/mm2 in the maximum case. A STARS conductor could be a candidate by employing a simple stacking of REBCO or Bi-2223 tapes, while there are presently two other candidates, FAIR and WISE conductors. In this paper, development of 20-kA-class HTS-STARS conductor is discussed, focusing on the quench protection with such a high current density. The bridge-type mechanical lap joint technique is also progressing to apply the “joint-winding” method for facilitating the winding process of the helical coils by connecting segmented conductors on site.

Speaker: Shinnosuke Matsunaga (SOKENDAI (The Graduate University for Advanced Studies))

MT-26 Yanagi poster.pdf

MT-26 Yanagi poster.pptx

533 Wed-Mo-Po3.02-05 [15]: HTS-WISE conductor and magnet impregnated with low-melting point metal

The FFHR Design Team has been investigating several types of High-Temperature Superconducting (HTS) large-current capacity conductors to be applied to the LHD-type helical fusion reactor FFHR-d1 (major radius R = 15.6 m). Presently, before realizing this commercial fusion reactor for electricity production, smaller reactors FFHR-c1 (R = 10.92 m) for DEMO and b1 for volumetric neutron source are being designed. For FFHR-b1, the target values of the current and current density are 10 kA and 120 A/mm$^2$, respectively, at the magnetic field of >16 T and temperature of ~20 K on the conductor. A new manufacturing method called “Wound and Impregnated Stacked Elastic tapes, WISE”, has been invented as one of the candidate conductors. In this concept, stacked HTS tapes are inserted into a flexible metal tube to form a conductor, and wound onto a coil frame, and then impregnated with low-melting metal. In the flexible metal tube, each tape naturally deforms so as to minimize the strain forces. The low-melting metal stabilizes the conductor from two points of view: good cooling efficiency and uniform current distribution among tapes and windings by utilizing the no-insulation (NI) technique.
A sample coil using the HTS-WISE conductor was fabricated to prove the feasibility of the WISE concept. Ten REBCO tapes of 4-mm width were inserted into a stainless-steel tube and wound to shape a solenoid coil. The major specifications of the coil are 21.5 turns with a minimum winding radius of 40 mm, and 30 µH of inductance. The coil achieved a central magnetic field of 0.16 T at 77 K, having an 800 A current (15 A/mm$^2$) in steady-state. Despite the appearance of an electric field of ~1 mV/m along the conductor, quench did not occur. In the presentation, the details of the NI-HTS-WISE magnet concept is discussed.

Speaker: Mr Shinnosuke Matsunaga (The Graduate University for Advanced Studies (SOKENDAI))

Wed-Mo-Po3_matsunaga_20190925_MT26.pdf

534 Wed-Mo-Po3.02-07 [16]: Electro-Magnetic Design of a 3T superconducting Dipole magnet

In this article, we presented a technical design of the superconducting Dipole magnet, H-type like the SAMURAI magnet at RIKEN, for the Lithium(Li) alloy, the material of first wall of ITER Demo, magnetofluid behaver study, depending on mechanics, thermal and electromagnetic multi-field couple analyze results. Each coil has 1998 turns, with the inner diameter was 1.5m. The wire has NbTi filaments with a total Cu/SC ratio of about 8 in the conductor. The operating current and the goal of central field are 425A and 3.0T, within 1000mm×1000mm×300mm(L×W×H) regions the inhomogeneity of the field is less than 5%, and the maximal magnetic field (Bmax) is 4.3T in the coils, respectively. The vertical magnetic force in the coils is about 200 tons, and the maximal hoop stress and radial stress of the coils are about 90MPa and 10MPa, theoretically. Meanwhile, magnetic quality and coil’s stress state affected by the assembly error and welding deformation of the magnet former are systematical analyzed, moreover dependent on the previous correlation results, we optimized the manufacture and assemble parameters to reduce the cast. And the cold mass of each coil is suspended from the room temperature vacuum vessel by six Titanium alloy suspension links. The magnet, with energy stored in the magnet is about 5 MJ, will be self-protecting. However, in order to limit the temperature, current and voltage value under a reasonable value in case of a quench, multi-segments protection method was employed. Now, the magnet is under construction, and as expected the test results will be reported.

Speaker: Chao Li

Wed-Mo-Po3.03 - Cryogenic Systems

Conveners: Hongyu Bai (NHMFL), Mr Kazuma Fukui (National Institutes for Quantum and Radiological Science and Technology)

535 Wed-Mo-Po3.03-01 [17]: Design of JT-60SA Cryodistribution components

JT-60SA is a fusion experiment tokamak device using superconducting magnets to be built in Japan. This joint international project involves Japan and Europe. In this work, we presents the design of cryodistribution and its components which are composed of a main transfer line (TL) and valve boxes (VB).
Five coolant loops are distributed between a helium refrigerator system (HRS) and cold components. Super critical pressure helium (SHe) of 4.5 K and 0.5 MPa supplied to 18 toroidal field coils, 6 equilibrium field coils and 4 central solenoid modules (LOOP1 & 2). SHe of 3.7 K and 0.5 MPa is supplied to divertor cryopumps (LOOP3). Gaseous helium (GHe) of 80 K and 1.4 MPa is supplied to radiation thermal shields (LOOP4). GHe of 50 K and 0.4 MPa is supplied to cold ends of high temperature superconducting current leads (LOOP5).
TL is a vacuum heat-insulation multiple piping, of which the length is about 45 m, and connects between HRS and the tokamak cryostat. All 5 supply lines, 4 return lines and 2 control valves are installed in TL. The outer vacuum pipe diameter is 965.5 mm and the inner coolant pipe diameter are 108.3 mm for LOOP 1/2/4 and 59.0 mm for LOOP 3/5. A vacuum partition between HRS and the tokamak cryostat is located near the middle of TL in a longitudinal direction.
VB contains cryogenic valves and measurement devices to control the cold helium flow. Eleven VBs are installed around the tokamak cryostat. Dimensions of VB body are 2 m in height and 1.4 m in diameter. Almost all cold helium lines from HRS are firstly into VBs through TL. Impulse lines, orifice plates, and resistor elements are installed at the pipes in VB for measurement of the pressure, the flow rate, and the temperature of coolant helium.

Speaker: Dr Kyohei Natsume (Quantum radiology Science and Technology)

Wed-Mo-Po3.03-01_Natsume.pdf

536 Wed-Mo-Po3.03-02 [18]: Quench recovery analysis of the JT-60SA superconducting magnets

JT-60SA is one of the experimental nuclear fusion reactors with superconducting magnets. It is a joint international research and development project involving Japan and Europe. The transitional change of temperature distribution of these magnets in recovery from the coil quench is investigated.
The quench recovery period is necessary to be confirmed. Generally, the maximum temperature drop of magnets is able to be confirmed by checking the thermometer attached to the outlet of the helium flow path. However, the maximum temperature of the JT-60SA central solenoid (CS) is not able to be measured during quench recovery. A CS module is composed of the 52 layers pancake coils. The 26 helium flowing paths are in a one module and two pancake coils are cooled in series in one flow path. The refrigerator supplies helium at 4.4 K to each flowing path in nominal operation.
The flowing paths of CS is C-shaped and both of the outlets and the inlets of helium are on the outer periphery surface of the CS modules. Due to this C-shaped flowing path, heat exchanges between the inlet flow paths and the outlet flow paths. The CS outer periphery side becomes colder than the inner periphery side. The typical issue is the CS inside temperature is not able to be measured by the thermometers on the flowing paths.
In case of a quench, the refrigerator stops helium supply in order to shut out large heat load from the quenched magnet. Helium will be supplied again when the magnet pressure become low enough. In this work, the CS temperature distribution change during quench recovery is calculated by using the thermal fluid simulation codes, and the period required for recovery is investigated.

Speaker: Kazuma Fukui (National Institutes for Quantum and Radiological Science and Te)

537 Wed-Mo-Po3.03-03 [19]: Alarm and interlock system in cryogenic system of EAST

EAST (Experimental Advanced Superconducting Tokamak) has been carried out fourteenth campaigns since its implementation at the end of 2005. The cryogenic system is one important subsystem which is to cool down the superconducting magnets and relating components. Alarm and interlock system ensure the reliability and safety of cryogenic system. This paper presents the overview of the alarm and interlock system, especially in quench protection in cryogenic system of EAST. At same time, the operational performance has been analyzed with further purpose to improve the cryogenic system reliability so as to guarantee the success of high performance plasma experiments in future.

Speaker: Dr Liangbing Hu (Institute of plasma physics Chinese academy of sciences)

Wed-Mo-Po3.03-03_HU.pdf

538 Wed-Mo-Po3.03-04 [20]: Conceptual design of the cryogenic system for large scale superconducting coil test

With the development of superconductivity technology, more and more large scale superconducting coils or magnets are used in the scientific installation like tokomaks, particle accelerators and colliders. Before installation, each coil is needed to cold test at nominal operating current to minimize the risk of malfunction. Hence, a helium refrigerator with an equivalent cooling capacity of 5 kW at 4.5 K for large scale coil test facility is proposed. It can provide 3.7 K, 4.5 K supercritical helium for coil, 50 K cold helium with a 10 g/s flow rate for High Temperature superconducting (HTS) current leads and 50 K cold helium with a cooling capacity of 1.5 kW for thermal shield. This article presents the conceptual design of cryogenic system for large scale superconducting coil test, including system process, thermal cycle, operation modes, compressors station system, cold box, distribution system and cryogenic control system.

Speakers: Dr Zhigang Zhu (Institute of Plasma Physics, Chinese Academy of Sciences), Prof. Ming Zhuang (Institute of Plasma Physics, Chinese Academy of Sciences)

Conceptual design of the cryogenic system for large scale superconducting Coil Test.pdf

Wed-Mo-Po3.04 - Medical Applications

Conveners: Atsushi Ishiyama (Waseda University), William Marshall (National High Magnetic Field Laboratory)

539 Wed-Mo-Po3.04-01 [21]: Design and development of beamline system for a proton therapy facility

A proton therapy facility with multiple treatment rooms based on superconducting cyclotron scheme is under development in HUST (Huazhong University of Science and Technology). This paper will introduce design and development of the beamline system that convers the ESS (Energy Selection System) section based on an energy degrader, the gantry beamline with image optics, and a kicker system which performs fast beam switch during spot scanning. Design, construction and magnetic field measurements of beamline magnets, including dipoles, quadrupoles and the kicker magnet will be described. A lightweight superconducting gantry beamline with alternating gradient (AG) combined function dipoles, which is planed for future upgrade, will also be discussed.

Speaker: Mr Wenjie Han (Huazhong University of Science and Technology)

540 Wed-Mo-Po3.04-02 [22]: Design and development of small model HTS coil system for Skeleton Cyclotron

We proposed the air-core cyclotron using high-temperature superconducting (HTS) technology, named Skeleton Cyclotron, as high intensity compact cyclotron. Skeleton Cyclotron consists of split main coils generating the isochronous field and sector coils generating the azimuthally varying field (AVF). Rapidness and reproducibility of magnetic field change for various particle and various energy are improved. Currently, we are carrying out a feasibility study on a variable-energy multi-particle Skeleton Cyclotron for medical radioisotope (RI) production. It is necessary to develop the following HTS magnet technologies for Skeleton Cyclotron: 1) the no-insulation (NI) winding technique for high current density and high thermal stability; 2) reduction method of screening current for highly precise magnetic field and optimal operating current pattern for temporal stability of magnetic field; 3) our proposed Y-based Oxide superconductor and Reinforce Outer Integrated (YOROI) structure with a high mechanical strength structure for circular and noncircular coils; and 4) optimal configuration design of HTS multi-coil system. Therefore, the small model HTS coil system to generate the magnetic field for accelerating proton up to 5 MeV of energy at an extraction radius of 20 cm is designed and manufactured to verify the key issues in HTS magnet technologies for Skeleton Cyclotron. In this presentation, the design and progress in development of the small model HTS coil system is reported.

Acknowledgements
The part of this work was supported by JSPS Grant-in-Aid for Scientific Research (S) Grant Number 18H05244.

Speaker: Prof. Hiroshi Ueda (Okayama University)

541 Wed-Mo-Po3.04-03 [23]: Structure Optimization of The Fast Scanning Magnets for Proton Therapy

A new proton therapy facility is under development in Huazhong University of Science and Technology.Scanning magnets play an important part in this facility, which affect the size of the radiation field by controlling the trajectory of the proton beam.Two independent dipole magnets, magnet X and magnet Y, scan the beam in horizontal and vertical, respectively.In order to reduce the temperature rise of the coil, the tapered air gap of magnet Y which is compatible with the envelope of the proton beam deflected by the magnet X is considered.In this paper, Software simulation have carried out to design two dipole magnets，mainly on the tapered air gap structure optimization of magnet Y.The local and integrated field quality have been optimized.As two dipole magnets are excited by alternating currents, excitation current and repetition frequency should be taken into account, which can cause the temperature rise of the magnets.The static and dynamic electromagnetic simulation were carried out.The thermal simulation was also carried out to analyze the effect of the eddy current.The dynamic behaviors of the two dipole magnets were analyzed and the way to reduce the effects of the eddy currents was proved to be useful.

Speaker: Zhongqi Zhang (Huazhong University of Science and Technology)

Wed-Mo-Po3.04-03 [23].pdf

542 Wed-Mo-Po3.04-04 [24]: Multiple redundant fuzzy-PID control technology for the scanning magnets of proton therapy nozzle

The scanning magnets in the proton therapy nozzle control the deflection of the proton beam by changing the magnetic field, so that the position of the proton beam can be controlled precisely, within 0.5mm error at lateral and longitudinal position. In order to meet the requirements for precise control of the beam position, a multiple redundant adaptive PID control system for scanning magnets is designed based on LabVIEW in this paper. It monitors the current of the scanning magnet coil and the actual magnetic field at the same time, then controls the output of the scanning magnet power supply separately through closed-loop positive feedback calculation, so that the entire magnetic field control system can maintain normal operation. And the fuzzy-PID control technology is added in the closed-loop program to improve the system response speed and adaptive computing ability, also increase the stability of the system.

Speaker: Yinjie Lin (HUST: Huazhong University of Science and Technology)

poster-huyuying.pdf

543 Wed-Mo-Po3.04-05 [25]: Lightweight design of superconducting magnets for a rotating gantry with active shielding

A rotating gantry enables charged particles to be delivered to a tumor with great accuracy in heavy particle therapy. Hence, cancer therapy that does not damage a patient can be realized with a rotating gantry. The world’s first rotating gantry composed of superconducting magnets was developed in the National Institutes for Quantum and Radiological Science and Technology in 2015. Using superconducting magnets instead of conventional magnets, it became possible to make a lighter, smaller rotating gantry.
The superconducting magnet for the rotating gantry consists of a cosine-theta superconducting coil surrounded with an iron yoke which is the heaviest part of the magnet’s weight. The weight of one superconducting magnet reaches several tons, and the rotating gantry is composed of ten superconducting magnets. Accurate rotation control is required under the condition that the magnets of several ten tons are mounted on the frame of the rotating gantry. In this study, a superconducting magnet composed of an active shield coil for the gantry has been proposed for the purpose of simplifying the control system and the frame structure of the rotating gantry by reducing its weight. The magnet’s weight can be reduced by using an active shield coil instead of an iron yoke to shield the leakage magnetic field. The lightweight design of a superconducting magnet with active shielding for a rotating gantry is presented.

Speaker: Tetsuhiro Obana (NIFS)

MT26.pdf

544 Wed-Mo-Po3.04-06 [26]: Fundamental Study on Cancer Therapy by Blocking Newborn Blood Vessels Using a High-Frequency Rotating Magnetic Field

In this study, a novel cancer treatment with low side effect and less invasiveness by blocking newborn blood vessels around the diseased part was proposed. In the therapy, ferromagnetic particles administered into the body are accumulated in the newborn blood vessels using a rotating magnetic field, and then are aggregated by a uniform magnetic field to block the blood vessels. The blockage prevents the cancer growth and metastasis. The particles are selectively accumulated on-axix of the rotating magnetic field by the cyclic motion on the inner wall of the blood vessel since a stable magnetic force acts on the particle.
A previous study in our group showed the possibility of local accumulation of the ferromagnetic particles on the rotation axis 25 mm away from a magnetic field source by using a high-frequency rotating magnetic field. In order to put this therapy into practical use for cancers located deep in the body, it is necessary to accumulate the particles at a target site about 300 mm away from the magnetic field source. In this research, we propose an application method of the rotating magnetic field by utilizing four superconducting magnets and a cylindrical magnetic shielding material with a slit. In this method, the four superconducting magnets are excited at the same time, and the rotating magnetic field is applied by the leakage magnetic field from the slit of the rotating shielding material. Accordingly, we designed a rotating magnetic field that can locally accumulate the particles at the target site 300 mm away from the magnetic field source and examined the possibility of particle accumulation by the simulation based on magnetic field and fluid analysis and the model experiment by using simulated organ.

Acknowledgment: A part of this research was supported by Magnetic Health Science Foundation.

Speaker: Mr Makoto Kirimura (Division of Sustainable Energy and Environmental Engineering, Graduate School of Engineering, Osaka University)

Poster_Wed-Mo-Po3.04-06.pdf

545 Wed-Mo-Po3.04-07 [27]: Optimum Design of Continuously Workable Transcranial Magnetic Stimulator

Repetitive Transcranial Magnetic Stimulation (rTMS) is a non-invasive biological stimulation technology. For ideal therapeutic effect, the stimulation current usually has a rather high amplitude. Since the resistance of stimulation coil can’t be neglected, large Joule heat will be generated during treatment. Once the coil temperature is beyond safety margin, the stimulator will be suspended, resulting in low stimulation efficiency.
To solve this problem, an integrated heat dissipation transcranial magnetic stimulator for continuous working is proposed in this paper. The stimulation coil is winded by hollow copper wire and the hollow part provides circulation channel for deionized cooling water. The cooling water source is provided by a small silent chiller. Low-temperature cooling water from the outlet takes away the Joule heat when running through the coil, then the heated cooling water returns to chiller to complete the cooling circulation. The stimulation system and the heat dissipation system are controlled by the same computer. Temperature and flow rate of the cooling water can be adjusted on-line by tracking the stimulation parameters through the control module to ensure that the temperature of stimulation coil is maintained at desired value.
Adaptive genetic algorithm is adopted to globally optimize the key parameters of the transcranial magnetic stimulator including coil turns, layers, hollow diameter as well as temperature and minimum flow velocity of cooling water. Optimal design of transcranial magnetic stimulator is obtained with minimum power loss and satisfies both medical needs and heat dissipation requirements. Finite element analysis is adopted to obtain three-dimensional spatial distribution of the intracranial induced electric field. Results show that compared to traditional magnetic stimulator without considering heat dissipation, this novel transcranial magnetic stimulator design can work continuously under the premise of guaranteeing the stimulation intensity and focalization.

Speaker: Xiao Fang

Wed-Mo-Po3.04-07 [27]方晓.pdf

Wed-Mo-Po3.04-07 [27]方晓.pptx

Wed-Mo-Po3.05 - Generators I

Conveners: Dr Timothy Coombs (University of Cambridge), Michael Green (LBNL)

546 Wed-Mo-Po3.05-01 [28]: Multiobjective optimal design of bearingless permanent magnet synchronous generator with multiobjective particle swarm optimization algorithm

Since the rotor is supported by mechanical bearings, the mechanical friction and wear exist in the conventional wind turbine inevitably, which not only increase the starting wind speed and the maintenance cost, but also reduce the efficiency of power generation and the operation stability. In order to overcome these disadvantages, a magnetic suspension wind turbine (MSWT) is proposed. Nowadays, the MSWT has been extensively investigated all over the world due to the advantages of low starting wind speed, high power generation efficiency, low maintenance cost, no friction, no lubrication, and so on. However, some defects limit its development. For example, the application of magnetic bearings increases the axial length of the system, limits the critical speed, and generates great suspension power consumption. The introduction of a bearingless generator to replace the wind turbine supported by magnetic bearings can effectively solve these problems. To realize the design objectives of high generation performance and stable suspension capability, the multiobjective optimal design of a bearingless permanent magnet synchronous generator with multiobjective particle swarm optimization (MOPSO) algorithm is carried out in this paper. Firstly, the torque and the suspension force performances of each design factor combination are analyzed by finite element analysis (FEA) method according to the central composite design scheme. Secondly, in terms of the results of FEA, the response surface method is applied to obtain the regression equations of the optimization objectives with respect to the design factors. Thirdly, with the response surface models as the objects, the Pareto front is obtained by the MOPSO algorithm. Finally, the Pareto optimal results are analyzed in the FEA software and the validity of the design scheme is verified.

Speakers: Ying Xu (Jiangsu University), Mengyao Wu (Jiangsu University)

Hua Yizhou-Poster.pdf

Hua Yizhou-Poster.pptx

547 Wed-Mo-Po3.05-02 [29]: Experiments and Design Criteria for a High-Speed Permanent Magnet Synchronous Generator with Magnetic Bearing Considering Mechanical Aspects

A high-speed permanent magnet synchronous generator (PMSG) has been applied to a variety of industries due to its many advantages, as simple structure and high output density. However, since the required speed of the rotor is increased, the structure problem of the rotating machine is continuously caused due to the physical contact in the case of the conventional ball bearing.
In this study, the design and experiment of high-speed PMSG using magnetic bearing without mechanical friction was carried out. The rotor size of the PMSG is designed by considering the DN factor of the bearing, and has a rotor diameter larger using magnetic bearings than that of the rotor diameter using ball bearings. Increasing the size of the rotor will reduce the stator copper loss and rotor eddy current loss due to the increase of magnetic field, but the increase of the core loss. Furthermore, stress analysis of permanent magnets and sleeves should be performed as a result of the increase in rotor size. Thus, in this paper, the high-speed PMSG with magnetic bearings is presented a design method considering the improvement of the conventional electric machine design technique from an electromagnetic point of view and the securing of structural reliability of rotor. The validity of the proposed design method was verified by the electromagnetic and mechanical analysis, design and comparison with experimental results of the high speed PMSG of 124 kW, 36 krpm. The design criteria, analysis results, and measurements of the high-speed PMSG will be presented in more detail in the final paper.

Speaker: Jeong-In Lee (Chungnam National University)

2019_MT_ORC_poster.pdf

548 Wed-Mo-Po3.05-03 [30]: Design and Analysis of High-Speed Permanent Magnet Synchronous Generator Considering Rotor Structure

Owing to their many advantages, such as high efficiency, high power density, simple mechanical construction, no excitation loss, and good reliability, high-speed permanent magnet synchronous generators (PMSGs) are gaining considerable attention from academia as well as industry worldwide. Because of the high-magnitude centrifugal forces that are exerted on the permanent magnets (PMs) in high-speed PMSGs, a robust rigid rotor construction is paramount. In particular, to protect the PMs in the rotor, the surface of rotor is coated with a retaining sleeve constructed from either an alloy or carbon fiber. Furthermore, a high-strength material is used for the shaft coupling component of the PMSG because of the stiffness of the shaft. Nevertheless, because this high-strength material might possess magnetic properties itself, it can influence the electromagnetic characteristics in the end effect. Moreover, the winding reactance includes significant leakage reactance because of the robust rigid rotor structure. Therefore, it is important to accurately calculate the total leakage reactance for the electromagnetic evaluation of high-speed PMSGs. In this study, an accurate analysis to determine the electromagnetic parameters of high-speed PMSGs is proposed; in addition, the influence of the rotor structure on the electromagnetic performance of these generators is analyzed. Because finite element (FE) analyses capable of solving transient models that include rotational and external circuits are now widely available, using these advanced computational methods, it is possible to determine the electromagnetic performance of the generators considering realistic features such as saturation, magnet segmentation, and end effects. In particular, in contrast to the existing 2D FE analysis approach, the electromagnetic parameters that are influenced by the rotor structure have also been identified and included in our proposed approach to accurately predict the electromagnetic performance of high-speed PMSGs. Finally, the efficacy of the proposed method is evaluated using 3D FE analysis and experimental verification.

Speakers: Kyung-Hun Shin (Chungnam National University), Tae-Kyoung Bang (Republic of Korea /Chungnam National University)

MT_Poster_Shin_Upload.pdf

549 Wed-Mo-Po3.05-04 [31]: Experimental Verification and Analytical Prediction for Generating Characteristics of Double-Sided Permanent Magnet Linear Synchronous Generator for Ocean Wave Energy Converter

For permanent magnet (PM) linear generators to be applied to ocean wave energy converters, highly efficient energy conversion is important; however, for maximum power generation, wave motion variation must be treated in real time. Therefore, we propose a characteristic map of the generating performance, including characteristic results of power, losses, efficiency, force, and the power take-off (PTO) damping coefficient. The conditions for optimum performance and the range of maximum power generation can be obtained from these results. Furthermore, when regular wave energy is generated, the heaving motion of the buoy is changed by the PTO damping coefficient from the PM linear generator, and the input velocity of the PM linear generator is thereby affected. Therefore, selecting the condition for maximum power in regular wave energy is vital for ocean wave energy converters.
In this study, a three-dimensional (3D) analysis method and a manufacturing model are used for analysis of generating performance and experimental verification on a double-sided PM linear synchronous generator (PMLSG) with a slotless stator. The initial design was devised using the 3D analytical method, which reduced analysis time and provided increased reliability. In addition, no-load performance was verified through experiments on the manufactured model. And then, under an ac-load, we determined the generating characteristics of the PM linear generator, with the heaving motion of the buoy coupled with the generator according to ocean wave variation. Finally, we addressed the generating results of the PM linear generator for the ocean wave energy converter according to the irregular input wave. In the detailed manuscript, we present a simple summary process of the 3D analysis method and various experimental results of the manufactured model; and all the analytical procedures are specially designed to contribute to related research and industrial applications.

Speaker: Sung-Won Seo (Chungnam National University)

MT_Poster_IrregularWave_v01.pdf

550 Wed-Mo-Po3.05-05 [32]: Experimental Verification and No-load Characteristics Analysis of Permanent magnet Linear Oscillating Actuator by using Semi-3D Analysis Technique with Corrected Stacking Factor

Recently, with the emergence of several global industries, linear oscillating actuators (LOAs) have been developed for various applications where short-stroke linear motion is required. In common LOAs, since electromagnetic losses are the parameters that determine the operating conditions and efficiency of most electrical machines, it is very important to accurately predict and reduce these losses. To reduce the loss of a single - phase LOA model with ring - type stator structure used in this paper, lamination of the radial direction perpendicular to the current direction of the coil is applied.
In contrast to normal electrical machines, radially laminated cores consist of 12-lamination blocks because of manufacturing limitations for the stator. The 12 stacked blocks are independent, and three-dimensional(3D) analysis is essential for a more accurate analysis of radially stacked LOA. However, 3D analysis takes a considerable amount of time. In this paper, we propose an analytical method that addresses the stacking factor through a two-dimensional (2D) analysis, with the aim of deriving an analytical result similar to the 3D result but with a shorter analysis time. In the 2D analysis, the stacking factor is considered in analyzing the magnetic flux density according to frequency. When the stacking factor is considered, the accuracy of the analysis is increased compared to that of the conventional 2D analysis because the area of the iron core relative to the induced magnetic flux density is taken into account. Subsequently, no-load characteristics were analyzed based on the more accurate magnetic flux density.
Finally, we compare the core loss through the proposed analysis method and the core loss through the 3D model analysis. In addition, the validity of the analytical method presented in this paper was verified by comparing the experiment of LOA actually made. Further discussion and analysis are also provided in the final paper.

Speaker: Jong-Hyeon Woo (chungnam national university)

MT_Poster양식.pdf

551 Wed-Mo-Po3.05-06 [33]: Research of Post-Assembly Magnetization of Large Surface-Mounted Rare-Earth Permanent Magnet Machines with Integrated Magnetizing Windings combing with Stator Windings

With the power increasement of permanent magnet (PM) machines, the manufacture process and maintenance of irreversible demagnetization become increasingly difficult, which limits the magnetic field configuration design of large PM machines. Post-assembly magnetization method is the key to solve these problems and can improve the machine performance. One way is adding additional integrated magnetizing winding. The magnetizing coils are directly wound around the un-magnetized PMs, and mounted on the surface of the rotor together. The PM machine can be magnetized after completely assembly by energizing the magnetizing winding with a pulsed magnetizing current. However, it is not easy to obtain high enough magnetizing field while ensure the insulation and reinforcement of the magnetizing winding due to the limited space between adjacent PM poles. A hybrid magnetization method using additional integrated magnetizing winding combing with machine's own stator winding for a megawatt PM wind generator is presented in this paper. The parameters of the magnetizing winding are designed. The parameters of the magnetizing circuit and the discharge sequence and field proportion of the magnetizing coil and stator winding are optimized to obtain the minimum magnetizing field required for saturated magnetization. The impact of inverse eddy current in PMs and the coupling effect between magnetizing winding and stator winding are analyzed. The problem of weakness of local magnetizing field caused by stator slotting is solved by using magnetic slot wedges. The simulation results show that the magnitude and uniformity of the composite magnetizing field meet the requirements, the ampere turns required is reduced compared with the method of using additional magnetizing winding only. Moreover, the temperature rise and stress of the magnetizing winding are acceptable. It is indicated that the large surface-mounted PM wind generator can be post-assembly magnetized with the magnetization method proposed in this paper.

Speaker: Qingjian Wang (Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology)

Wed-Mo-Po3.05-06_MT26_Wang Qingjian.pdf

552 Wed-Mo-Po3.05-07 [34]: Detent Force and Static Thrust Experimental Analysis of a 3kW Single-Phase Linear Permanent Magnet Generator for Striling Engines

The single-phase linear permanent magnet generator (SPLPMG), which is applied to the free piston Stirling engine (FPSE), has a simple structure and robust topology.
When a linear drive system such as a free piston Stirling engine is applied, a linear generator does not require a mechanical energy conversion device such as a screw or a crankshaft, and thus has a small mechanical loss and a spatial advantage. Also, it does not require lubrication and has a simple maintenance mechanism because of its simple mechanical structure.
Despite these advantages, the linear generator has the disadvantage that it is very difficult to evaluate due to its reciprocating linear motion. Also, unlike rotating machines, it is not easy to evaluate the detent force of a linear generator and to evaluate the output power of a linear generator.
Therefore, in this paper, the detent force, the repulsive force and the static thrust force of the SPLPMG are analyzed by FEM. And the evaluation system of the detent force and the repulsive force
In order to test the detent force and the repulsive force of the SPLPMG, a linear evaluation system was constructed. The evaluation system consisted of a load cell, a mover position controller, an air bearing, and a bed.
Based on the developed evaluation system, the detent force of the mover and the repulsive force by the spring magnet will be evaluated and compared with the analysis results.
Also, in the case of linear generators, it is difficult to evaluate the thrust force for the input power when evaluating the load.
Therefore, the load rated current will be applied while the mover is fixed, to evaluate the static thrust force.
Based on the results of this analysis, the final paper will give a detailed comparison of the results of the analysis and experimental evaluation of the detent force, the repulsive force of the spring magnet, and the static thrust.

Speaker: Mr Kyu-Seok Lee

MT26-Wed-Mo-Po3. 05-07.pdf

MT26-Wed-Mo-Po3. 05-07.pptx

553 Wed-Mo-Po3.05-08 [35]: Maximizing Efficiency of IPMSG in the Engine Generator System of a Plug-in Hybrid EV and Its Comparison with SPMSG

Recently, eco-friendly vehicles such as pure electric vehicles (EVs), hybrid EVs and plug-in hybrid EVs (PHEVs) have been the subject of many studies in a dramatically accelerated effort to increase the total driving distance on a single charge. Among of PHEV components, increasing the efficiency of the engine generator system (EGS) is a key challenge in this effort. In the EGS, a generator and an engine are mechanically linked, where the generator is operated from output power of the engine while the PHEV is operating. In order to increase the efficiency of EGS, the generator should be driven with high efficiency at optimal operating points, which are selected based on their efficiency using an experimental engine test. These operating points are called the optimal operating line (OOL), and the efficiency of the generator should be maximized on the OOL. Therefore, this paper proposes to maximize the efficiency of the generator in the EGS of a PHEV.
Meanwhile, permanent magnet synchronous generators are well-known as suitable candidates in PHEV because of their performance characteristics such as high power density and efficiency. According to PM arrangement, a surface-mounted PM synchronous generator (SPMSG) and an interior PM synchronous generator (IPMSG) are classified. In this paper, both of them have been designed and applied to optimal design to maximize the efficiency on the OOL based on finite-element analysis, where intelligent mesh adaptive direct search was used as the optimization algorithm. The generators were experimentally tested and compared in terms of torque density, efficiency, total harmonic distortion and torque ripple. Since the performance of IPMSG is better than that of SPMSG, it was selected and built into the vehicle. Finally, the IPMSG built-in PHEV has been tested and validated. A full paper will describe the above-mentioned studies in detail. This work is funded by the Korea Automotive Technology Institute.

Speaker: Dr Ho-Chang Jung (Korea Automotive Technology Institute)

554 Wed-Mo-Po3.05-10 [36]: A Novel Permanent Magnet Linear Generator

A novel single phase tubular permanent magnet linear generator for Stirling engines is proposed in this paper. It has a bread type winding, which has no cutting. It comprises an outer-stator, an inner-stator and a mover, and they are mounted in a cylinder. The winding coils are wound in a ring shape and placed in the slot of the outer-stator. The inner-stator is made up of a ferromagnetic ring. The mover is drivingly linked to a piston and it consists of four ring-shaped permanent magnets that are all polarized radially, and the polarized direction of the two permanent magnets on the outside are in the opposite of that of the two magnets on the inside. The stator outer diameter is 80mm and the outer-stator laminated thickness is 22mm. The whole mover laminated thickness and the inner-stator laminated thickness are both 30mm. The inner-airgap is 0.2mm while the outer-airgap is 0.3mm. The silicon steel material of the outer-stator and inner-stator is 50W470. The permanent magnetic part of the mover is made up with Nd-Fe-B, and the non-magnetic support shaft is made up with aluminum. Taking the space of outer-stator’s slot into consideration, the turns of diameter of the copper wire is selected as 71 and the diameter of the copper wire is chosen as 1.5mm when concerned about the output current value is approximately 10A. The three-dimensional finite element model of proposed TPMLG is established. The model and its boundary conditions are presented. Through the FE model, its electromagnetics analysis is carried out. The performance of this generator under reciprocating frequency 75Hz is investigated and analyzed. With the FE model, the weight of the iron core of outer-stator, inner-stator, coils of copper, mover with four permanent magnets and the support shaft are calculated thoroughly. The average power per unit mass is around 115.848W/kg. The advantages of the generator that it has high-power density are shown. It can be used as the generator in the Stirling engine.

Speaker: Prof. Hao Chen (China University of Mining and Technology)

MT26(1).pdf

555 Wed-Mo-Po3.05-11 [37]: Fully Coupled Numerical Method for Coated Conductor HTS Coils in HTS Machine

Rotational machine is a kind of promising high temperature superconducting (HTS) electrical application. Among them, the coated conductor HTS coils are most commonly used as DC magnets because the DC HTS coils in the rotor under the relatively stationary fundamental magnetic field does not cause AC loss. However, in actual operation, AC loss produced by the harmonic magnetic fields is inevitable. Other inevitable transient electromagnetic disturbances in the operating machine environment can also cause AC loss. Considering cooling penalty, these kinds of AC loss may not be ignored, and it is not easy to be calculated because of the complex electromagnetic environment in actual operating machines, the large scale of HTS coils, high aspect ratio for coated conductors, and the anisotropy property of HTS tapes. This paper introduces and verifies a fully coupled numerical method for coated conductor HTS coils in operating machine based on T-A formulation. This method can calculate the AC losses of HTS coils in the operating machine environment fast and effectively. Using this method, the effects of ferromagnetic stator teeth and shielding layer on AC loss produced by the harmonic magnetic field and load change are also quantitatively displayed.

Speaker: Dr Zhen Huang (Shanghai Jiao Tong University)

Wed-Mo-Po3.06 - Generators II

Conveners: Dr Timothy Coombs (University of Cambridge), Michael Green (LBNL)

556 Wed-Mo-Po3.06-01 [38]: Design and Performance Test of an 1-kW-class HTS Generator with HTS Contactless Rotary Excitation Device

In this paper, the motor-generator set was developed to test the various output performance of a 1-kW-class high-temperature superconducting generator (HTSG) which is charged by HTS contactless rotary excitation device (CRED). First of all, the various full components for 1-kW-class HTSG were manufactured and assembled including a salient rotor pole with HTS coils, rotating shafts, torque transferring structures, rotating and stationary parts for CRED, and liquid nitrogen cooling system. Then, this assembled machine was connected with induction motor which is driven and controlled by voltage source inverter and three phase resistive and inductive road bank. The rated operating current of HTS field winding can be excited by rotation of HTS strands attached on toroidal rotor head of CRED at rated charging speed. After field winding charging, 1-kW-class HTSG was tested in no-load and electrical load modes to measure output power characteristics.

Acknowledgement: This work was supported in part by the “Human Resources Program in Energy Technology” of the Korea Institute of Energy Technology Evaluation and Planning (KETEP), granted financial resource from the Ministry of Trade, Industry & Energy (MOTIE), and by Korea Electric Power Corporation. (Nos. 20184030202200 and R18XA03)

Speaker: Ji Hyung Kim (Jeju National University)

557 Wed-Mo-Po3.06-03 [39]: Design of a HTS Field Winding Vernier Machine with HTS bulks on Flux Modulation Pole

This paper focuses on the design of a Vernier machine with HTS bulks on Flux Modulation Pole(FMP) and HTS field winding. Vernier machine gained importance in recent years for low-speed and large- torque (LSLT) applications, such as wind power generation. Despite the Low-speed high-torque capability, Vernier machine have lower Power factor than the power factor of conventional HTS Field Winding synchronous machine. The key of improvement is introduction of HTS bulks which decrease the flux leakage on the Flux Modulation Pole. In the analysis, Finite Element Analysis(FEA) was used to obtain the magnetic flux field distribution and the performance of the Vernier machine which is resulted by the magnetic gearing effect of the FMP. The voltage harmonic components of Vernier machine with HTS bulks was also investigated. Based on the design, we investigate the advantage of the HTS field winding Vernier machine with HTS bulks comparing to the one without HTS bulks.

Speaker: Do Hyun Kang (Sungkyunkwan University)

MT26_Poster_KDH.pdf

558 Wed-Mo-Po3.06-04 [40]: The structure design of a 300-kvar class HTS synchronous condenser prototype

China Southern Power Grid, Ltd. has established a project to study the feasibility of installing large-scale HTS dynamic synchronous condensers in Ultra High Voltage Direct Current (UHVDC) transmission grid. To investigate some key technologies, a small–scale one, such as 300-kvar class HTS synchronous condenser prototype is designed. The electromagnetic and structure design of this prototype is described in this manuscript. The rotor excitation winding, composed of totally 8 double-pancake racetrack coils, are wound by ReBCO coated conductors. It is cooled by forced-flow helium gas, and the working temperature is expected below 30 K. The water-cooled stator winding is embedded in non-ferromagnetic stator teeth. Made by fibre glass epoxy, the torque tubes are optimized to balance the thermal leak and mechanical requirement. The pair of copper (OHFC) current leads are designed to transport current from room temperature to cold terminals which are conduction cooled to below 30 K. All the rotor structures are enclosed in a vacuum chamber. Before assembling, the critical current of the rotor magnets are tested in liquid nitrogen temperature, and the test results shows the satisfactory with the design values.

Speaker: Qihong Wu (Tsinghua University)

MT26-Poster-SP-Wed-Mo-Po3.06-04.pdf

MT26-Poster-SP-Wed-Mo-Po3.06-04.pptx

559 Wed-Mo-Po3.06-05 [41]: Design and Numerical Analysis of 10 MW-class Fully-Superconducting Synchronous Generators Installing the New Casing Structure for Turboelectric Propulsion System

Nowadays, feasibility study of fully turboelectric propulsion systems for electric aircrafts are being conducted. Fully superconducting rotating machine is one of the solutions to realize fully turboelectric propulsion systems with lightweight and high power density. In our previous studies, we reported the high output power density over 20 kW/kg for the 10-MW-class fully superconducting generators. In the previous model it was assumed that the rotor is installed at the space filled with helium gas and the stator is cooled by sub-cooled liquid nitrogen at 65 K or liquid hydrogen at 20 K. The helium gas is cooled by the inner wall of the stator case. Therefore, the operating temperature for the field windings in the rotor was restricted to the liquid refrigerant temperature. In this study, we studied on the new model where the field winding is installed into another vacuum chamber and independently cooled by the other gas/liquid refrigerant. It composes a rotor. In this case it is possible to make the operating temperature of the field windings different from that for the armature windings. In this paper, various kinds of properties of the fully-superconducting generators with this new structure. The operating temperature of the field winding, Tf-op, are set to 20-65 K as a parameter. The dependences of the Tf-op on the AC loss, efficiency, dry weight, output power density were investigated and compared. In addition, the numerical analysis of the thermal stability was performed.

Acknowledgment
This research was partially supported by the New Energy and Industrial
Technology Development Organization (NEDO), the Japan Science and
Technology Agency (JST): Advanced Low Carbon Technology Research and
Development Program (JPMJAL1405) and the Japan Society for the Promotion
of Science (JSPS): Grant-in-Aid-for Scientific Research (JP18H03783 and
JP17H06931).

Speaker: Mr Masataka Komiya (Kyushu University)

560 Wed-Mo-Po3.06-06 [42]: Design and Analysis of a 10-MW-Class HTS Generator considering Various Winding Insulation Techniques for HTS Rotor-Field Poles

This paper presents the results of the electromagnetic design and numerical analysis for a 10-MW-Class second generation high-temperature superconducting generator (2G HTSG). Since the offshore wind power has the technical and economic difficulties in a regular maintenance due to geographical conditions that are difficult to access, the operation reliability of 2G HTS coil for the rotor-field poles should be technically guaranteed to realize the feasible application and, by extension, commercialization of the 10-MW-Class HTSG on offshore wind power. In this study, three winding insulation techniques (WITs) for HTS field coils (FC), such as no-insulation, metal insulation, and metal-insulator transition insulation, are considered to give a definite report the operation reliability of the 10-MW-Class HTSG in offshore environment. Using the time-transient solver of the three-dimensional electromagnetic finite element analysis (3-D EM FEA), EM characteristics of HTSG with three WITs are investigated and compared in terms of the performances of HTSG’s electrical output and HTS FC’s critical current. Then, in order to analyze the charging and discharging characteristics in steady-state operation as well as the electrical and thermal characteristics in transient-state operation of HTS FCs with three WITs, electric equivalent circuit models are built with key parameters based on EM FEA result. Finally, the performances of HTS FCs are discussed and evaluated in electromagnetic response time and stability characteristics.

Acknowledgement: This work was supported in part by the 2019 scientific promotion program funded by Jeju National University, and in part by Korea Electric Power Corporation (No. R18XA03)

Speaker: Yoon Seok Chae (Department of electrical engineering, Jeju National University)

Wed-Mo-Po3.07 - Magnetization and AC Losses I

Conveners: Hiroshi Ueda (Okayama University), Pasquale Fabbricatore (INFN Genova)

561 Wed-Mo-Po3.07-01 [43]: Magnetizing Technique for Permanent Magnets in IPM Motor Rotors Using HTS Bulk Magnet

A unique activation technique for permanent Nd-Fe-B magnets which were embedded in the rotors of interior permanent magnet (IPM) motors has been developed as a magnetizing tool using high temperature superconducting (HTS) bulk magnets. The experimental and numerical simulation studies were conducted to evaluate the magnetic field-trapping performances in two manners of we call “scanning” and “stamping” modes for the rotor of air-conditioner compressor in hybrid-type automobiles. The sample rotor with demagnetized permanent magnet plates were exposed in the intense static magnetic fields above the magnetic pole which contained the bulk magnet generating over 3 T. The magnetization property of permanent magnet plates in the rotor was found to follow the magnetization curve of the material with its anisotropic magnetization property. As a result, the sample magnets were perfectly magnetized in the static magnetic fields. The precise simulation on the flux distribution in the rotor clarified that it is important to make the direction of flux in the hales of rotor core and the easy magnetization axis of PM identical. We convinced this activation technique should enable us to promote the degrees of freedom of motor designing and processing.

Speaker: Prof. Tetsuo Oka (Shibaura Institute of Technology)

Oka A0 Wed-Mo-Po3-07-01 MT26 190917 Oka.pdf

Oka A0 Wed-Mo-Po3-07-01 MT26 190917 Oka.pdf

Oka A0 Wed-Mo-Po3-07-01 MT26 190917 Oka.pdf

562 Wed-Mo-Po3.07-02 [44]: Presentation withdrawn

563 Wed-Mo-Po3.07-03 [45]: Measurement and Analysis on Local Magnetization Properties of RE-123 Coated Conductor with DC Transport Current and External Magnetic Field

Magnetization of RE-123 coated conductor influences the spatial homogeneity and time variation of the magnetic field of a magnet. This has been an important issue for the realization of MRI, NMR and accelerator comprising the coated conductor. Therefore, the measurement and modelling of the magnetization of the coated conductor is crucial for the quantitative estimation of its influence on a magnet. However, the magnetization of the coated conductor is usually measured and analyzed as a global value; then it is difficult to clarify the local electromagnetic behavior governing such a global performance. Furthermore, such behavior should be investigated under the condition where both DC transport current and external magnetic field are applied simultaneously. In this study, local electromagnetic behavior was visualized by the scanning Hall-probe microscopy (SHPM). Taking account of the behavior, it was successfully reconstructed by a numerical analysis based on finite element method (FEM) including the local magnetization and its time variation depending both on DC transport current and on external magnetic field. This will contribute to the quantitative estimation and a solution for the magnetization problem of the magnets comprising RE-123 coated conductors.

This work was supported by JSPS KAKENHI Grant Number JP16H02334 and JP18K18864.

Speaker: Dr Kohei Higashikawa (Kyushu University)

MT26_Wed-Mo-Po3.07-03_Higashikawa_ppt_ver2.pdf

564 Wed-Mo-Po3.07-04 [46]: Presentation withdrawn

565 Wed-Mo-Po3.07-05 [47]: Influence of the size of soft-iron yoke on trapped field performance of HTS bulk

We study to increase a trapped magnetic field of HTS bulk magnet activated by pulsed field magnetization (PFM). Although various methods to enhance the trapped field are considered, they can be broadly divided into two approaches; one is improvement of magnetizing method and another is modification of exciting equipment. In the latter, a pulse width was expanded by changing an inductance of the coil and a capacitance of condenser which was current source. However, it costs a lot for the modification. In an exciting system of PFM, soft-iron yokes are used in order to expose the bulk to the magnetic field for a long time. It can be predicted that that trapped field is improved because magnetic flux hold in a soft-iron is increased when the size of yoke is increased qualitatively. On the other hand, an effect of the size of soft-iron yoke on trapped field performance has not been evaluated quantitatively. In this paper, a GdBCO bulk 60 mm in diameter and 20 mm thick is magnetized by applying a single pulsed field with varying an amplitude of applied field and temperature when soft-iron yokes of 40, 64 and 80 mm in diameter are used, and these trapped field characteristics are compared. This method is useful for practical use because the trapped field can be enhanced only by changing a soft-iron yoke.

Speaker: Kazuya Yokoyama (Ashikaga University)

MT26_posterA0-yoko.pdf

566 Wed-Mo-Po3.07-06 [48]: Magnetization of HTSC tape in flux pump regime

We have studied both theoretically and experimentally the process of magnetization of HTSC square (12mm x12mm) tape as well as stack from tapes by means of small source of magnetic field. The size of magnetic field localization was less than the size of sample. Local magnetic field induced the currents which were calculated in the frame of critical state model taking into account the dependencies of critical current on magnetic induction. The magnetization of the sample was calculated as well. We investigated the various methods of applying of magnetic field in which the amplitude of magnetic field was changed adiabatically. The position of source of local magnetic field changed too. It was shown that multiple cyclic impact of external field leads to increase in total magnetic moment in the sample up to 80 per cent from the maximum theoretical limits for studied sample. The results obtained make it possible to optimize the magnetization regime of a square fragment of a tape (or a stack of tapes) when implementing a magnetic pump on their basis.

Speaker: Maxim Osipov (NRNU MEPhI)

567 Wed-Mo-Po3.07-08 [49]: Modelling of Field and Field Quality in a YBCO Coated- Conductor Wound Planar Undulator

The field and field quality was modeled for a DC planar undulator designed to be wound with YBCO coated conductor. The undulator field on axis target was 1.3 T with a period length of 17 mm. The winding former and pole material were 1006 LCS, and the gap was 9.5 mm. A tape wound design was used, with 50 tape layers in a groove. The tape was taken to be 4 mm wide and 0.08 mm thick, with 10 m insulation on all sides (total thickness tape + insulation 0.1 mm). Operational temperature was assumed to be 4.2 K, and a 900 A Ic was assumed. Based on this design, the field, both in the winding, and in the bore, was calculated using FEM modeling in COMSOL Multiphysics software. Particular attention was paid to the bore region, where the field contribution of the shielding currents in the YBCO coated conductors were included. These results were compared to simple estimates based on analytic models. The field contributions were explored for different excitation levels, and for different cycle histories. Cycle histories were developed to minimize the field error contributions of the shielding currents at fields of active interest (user field measurement points). It was seen that a small pre-cycle could reduce both field error and its change with time.

Speaker: Milan Majoros (The Ohio State University)

Wed-Mo-Po3.08 - Current Limiters I

Conveners: Dr Mark Ainslie (University of Cambridge), Martin Eibach (GSI)

568 Wed-Mo-Po3.08-02 [54]: Modelling and experimental verification of dc inductive superconducting fault current limiter

Due to its excellent current-limiting capacity, especially at the initial dc fault transient stage, the analyses of dc inductive superconducting fault current limiter (I-SFCL) are attracting more attention. In this paper, a modelling method for dc I-SFCL was proposed to describe its nonlinear characteristic of inductance. Firstly, the structure of dc I-SFCL was briefly introduced. Then the magnetic field distribution, including the leakage magnetic flied distribution, was considered by finite element method (FEM) to establish an equivalent magnetic circuit of the dc I-SFCL. By analyzing the equivalent magnetic circuit, the relationship between dc transient current and the inductance of dc I-SFCL was calculated. Accordingly, a mathematical I-SFCL model can be built in MATLAB to discuss the current-limiting performance. A dc I-SFCL prototype has been fabricated to verify the accuracy of the proposed modelling method and simulation result.

KEY WORDS: dc inductive SFCL, leakage magnetic field distribution, equivalent magnetic circuit, modelling method, dc SFCL prototype.

Speakers: Prof. Bin Li (Tianjin University,Key Laboratory of Smart Grid of Ministry of Education School of Electrical & Information Engineering), Mrs Wei Hong (Tianjin University,Key Laboratory of Smart Grid of Ministry of Education School of Electrical & Information Engineering)

Poster-Wang-MT26-qiV2.pdf

569 Wed-Mo-Po3.08-03 [55]: A Resistance Model of Fault Current Limiting Magnets under DC Impact

Abstract: The short-circuit fault current on the DC side affects the operation safety of the multi-terminal flexible HVDC transmission system (MTDC) seriously. At the same time the superconducting fault current limiter (SFCL) has received extensive attention in limiting the DC impact current due to its characteristics such as fast response speed, good current limiting effect and zero impedance at steady state. At present, simulations of the resistance of YBCO tapes under DC impact is relatively larger, which affects the design accuracy of SFCLs. In this paper, the characteristics of DC fault current are studied. The resistance and other parameters of YBCO samples under DC impact are measured by use of a DC impact platform. The heat transfer process of YBCO tapes under DC impact is studied and three different modeling methods are obtained. Finally, these methods are improved considering the characteristics of the fault current limiting magnet (FCLM), and the simulation results are compared with the experimental results of FCLMs. The advantages and disadvantages of three modeling methods are compared, and the correctness is verified. This research aids in simulation analysis and optimization design of DC SFCLs.

Key words: fault current limiting magnet, YBCO tape, DC impact and transient heat transfer.

Speaker: Haonan Wang (Applied Superconductivity Key Lab, Institute of Electrical Engineering, Chinese Academy of Science)

A Resistance Model of Fault Current Limiting Magnets under DC Impact_20190919.pdf

A Resistance Model of Fault Current Limiting Magnets under DC Impact_20190919.ppt

570 Wed-Mo-Po3.08-04 [56]: Design of a novel inductive type fault current limiting

In a power system, fault currents are on the rise and are becoming a common problem. Although several methods are used to restrict fault currents, the methods have demerits in respect of stability and reliability of power system. In this regard, high temperature superconducting (HTS) fault current limiting applications are considering as an alternative and a number of related researches are in progress.
The authors suggest a novel inductive type fault current limiting HTS power cable, which takes the form of wound cable with iron core. When fault current traveling through the cable, the HTS shield layer experiences a transition from the superconducting state into a resistive state by the quench. It causes release of magnetic flux generated by the current to the out of shield layer, then the amount of magnetic flux interlinkage for the wound cable increases and inductive impedance also increases. The cable provides two merits, which are no additional insulation for the fault current limiting function and quick recovery time after fault clearance due to very low heat generations on the HTS layers.
In this paper, a novel inductive type fault current limiting HTS power cable was suggested and its effect was described through design and simulation results. The results are discussed in detail.

ACKNOWLEDGMENTS
This work was supported by the Korea Institute of Energy Technology Evaluation and Planning(KETEP) and the Ministry of Trade, Industry & Energy(MOTIE) of the Republic of Korea (No. 20171220100400).

Speaker: Sung-Kyu Kim (Korea Electrotechnology Research Institute)

MT26_Poster_SK_Kim.pdf

571 Wed-Mo-Po3.08-05 [57]: Simulation and experimental investigation on the critical current and AC losses of a hybrid superconducting fault current limiter with bias magnetic field during normal operation

The level of fault current has been increases quickly with rapid growth of electric load in recent years. The capacity of conventional circuit breaker has been unable to meet the demand. The wide application of high temperature superconducting fault current limiters (HT SFCL) provides a new avenue for power protection. They use the electrical properties of HTS to instantaneously protect power grids which can not only reduce the capacity of the circuit breaker but also improve safety of power grids. This paper deals with a novel hybrid superconducting fault current limiter with bias magnetic field. This high temperature superconducting fault current limiter has a reactor with double-split symmetrical windings and a non-inductive high temperature superconducting (HTS) magnet which is in series to one branch of the reactor. The simulation model of the hybrid SFCL is established in Matlab/Simulink to investigate its performance in a power grid. An experimental system is set up with a unit of SFCL magnet immersed in the liquid nitrogen and a high speed Data Acquisition (DAQ) System of National Instruments (NI) based on LABVIEW. The characteristics of the critical current, AC losses for the non-inductive superconducting unit of SFCL are experimental investigated to verify the effectiveness of the hybrid SFCL and evaluate the technical feasibility.

Speaker: Mr Hanyang Qin (North China University of Technology)

poster-MT26-zhujiahui.pdf

572 Wed-Mo-Po3.08-06 [58]: Conceptual design of a saturated iron core superconducting fault current limiter for a DC power system

Recently, high voltage direct current (HVDC) power systems have been widely developed and used around the world because of their large transmission capacity and low power loss. However, conventional DC circuit breaker (DCCB) is difficult to interrupt large fault current. Therefore, to limit the fault current to a relatively low level, a superconducting fault current limiter (SFCL) is introduced to effectively and rapidly limit the fault current due to inherent physical properties of the superconductor and significantly reduce the stress on the DCCB of the HVDC system. This paper presents a conceptual design of a saturated iron core SFCL (SI-SFCL) for a 15 kV, 3 kA DC power system. First, the electrical characteristics of the SI-SFCL were analyzed and the relationship between the fault current and the SI-SFCL parameters was defined. Then, the detailed design process of the SI-SFCL and its corresponding configuration were summarized. A mathematical model was developed to investigate the fault characteristics of the 15 kV, 3 kA DC power system and to determine the parameters of SI-SFCL accordingly. We also implemented the PSCAD/EMTDC simulation to analyze the operation and fault current limiting characteristics of the SI-SFCL. The validity of the fault current limiting performance and the design parameters was verified through the simulation results. When a fault occurred, the iron core was no longer saturated and the inductance of the SI-SFCL was increased due to the increase of permeability. As a result, the inductance of the SI-SFCL became much larger than that of the normal operating state for a very short time during the fault, limiting the fault current up to 70%. Since the SI-SFCL was not quenched, the system was immediately recovered by reclosing of the DCCB. The results of this study will be effectively applied to the development of SI-SFCL for large-scale HVDC power systems.

Speaker: Mr Van Quan Dao (Changwon National University)

MT26_Poster_Van Quan Dao.pdf

573 Wed-Mo-Po3.08-09 [59]: AC Loss Analysis of a 10-kV / 500-A Flux-coupling type Superconducting Fault Current Limiter

Fault current limiter (FCL) is commonly applied as a current-limiting device to improve the stability of the power system. In this paper, a Flux-coupling type Superconducting FCL (FC-SFCL) with a pair of HTS parallel windings has been developed. The limiter is based on disconnecting coupling windings for current-limiting, which has a low steady impedance at normal state and higher limiting one after fault. The problem of ac losses is fierce, which affects the thermal stability for larger leakage flux and greater fault current impulsion on the HTS windings after disconnecting. For a 10 kV / 500 A FC-SFCL prototype with windings wound on an iron-core with air gap, an improved AC losses calculation model is used to analysis the influences of different winding structures on losses and current distribution, and the scheme to reduce losses is proposed. Through adjusting the parallel numbers and arrangements of the coupling windings, their losses characteristic has significant improvements. The losses on each winding are balancing, total losses are declining, and magnetic field distributions become uniform.

Speakers: Sinian Yan (Huazhong University of Science and Technology, China), Li Ren (Huazhong University of Science and Technology), Guilun Chen (Huazhong University of Science and Technology)

574 Wed-Mo-Po3.08-10 [60]: Balanced current distribution in high coupling coils of flux-coupling-type superconducting fault current limiter

The flux-coupling-type superconducting fault current limiter (FC-SFCL) has been proposed to solve excessive short-circuit current in power system. FC-SFCL promotes the breaking capability by connecting two circuit breakers in parallel through two high-coupling coils. Since each coil is made of multiple coil units in parallel, there may be a problem of unbalanced current distribution, resulting local loss and stress concentration, which may cause security risk in operation. Therefore, design for high-coupling coil sets with balanced current distribution is a key part for application. This paper develops a method to design a pair of coil sets in FC-SFCL. Through theoretical analysis and simulation, an inductance calculation method considering structures and parameters of coil sets is obtained. Based on the demand of FC-SFCL, the parameters of coils are optimized by algorithm to achieve its requirements of balanced current distribution. According to the optimization results, the model is built and simulation is done to verify the effectiveness of design method.

Speakers: Rongyu Su (State Key Laboratory of Advanced Electromagnetic Engineering and Technology), Li Ren (Huazhong University of Science and Technology)

575 Wed-Mo-Po3.08-11 [61]: Analysis on Operation Characteristics of Double Quench Flux Lock Type Superconducting Fault Current Limiter

System operators make an effort to solve the fault current problem due to increase of distributed generation and complexity with parallel connection of the power system. Announced methods for solving the fault current such as replacing circuit breaker, installing high-impedance power equipment or series reactors have problems with cost, voltage drop, and power loss. The SFCL (Superconducting Fault Current Limiter) is effective in resolving the fault current with suppressing disadvantages of other methods. The SFCL has no electrical resistance during the normal operation. When the fault occurs and the fault current exceeds the threshold value of the current, the SFCL is quenching and the fault current is suppressed. The SFCL with a quench phenomenon has the feature that it cuts off the fault current at high speed without the control device and the monitoring device and is automatically returned to the normal state. For the above reasons, various type SFCLs have been studied recently. Among various SFCLs, the double quench trigger type which operates according to magnitude of the fault current with two current limit reactors is advanced model than single quench trigger type SFCL. The double quench trigger type SFCL consists of a switch, two HTSCs and resistances. However, the resistive type SFCL and trigger type SFCL could not have to control the HTSC characteristics such as quench time and impedance. We can search the adjustment method of the characteristics in the flux lock type. The flux lock type SFCL consists of iron core, multiple windings and HTSC element with serial connected in one of the windings. The flux lock type SFCL could improve both the quench characteristics and the current limiting effect according to the connection methods of the two coils and the winding directions.
This paper proposes the double quench flux lock type SFCL, combined with double quench type and flux lock type, which derives current limiting and operation controlling characteristics The suggested method could be confirmed through the simulation using PSCAD/EMTDC.

Speaker: Hyeong-Jin Lee (Soongsil University)

MT_Poster_ver1.pdf

576 Wed-Mo-Po3.08-12 [62]: Study on the current limiting characteristics of YBCO coated conductor according to different stabilizer layer with iron core and coil

The yttrium-barium-copper-oxide (YBCO) coated conductor, which supplement the fault of the existing superconducting current-limit materials YBCO thin film, bismuth-strontium-calcium-copper-oxide(BSCCO) wire and bulk, has been improved its mechanical weakness and has high index; hence, after quench YBCO coated conductor could limit the fault current effectively because of fast resistance occurrence speed. Furthermore, it has wide applicable area as an current limit material because it shows different resistance occurrence tendency by the thickness and kind of stabilization material sputtered on the superconducting layer. Therefore, many researchers are carrying out the study of application of YBCO coated conductor to superconducting fault current limiter (SFCL) for making high quality current limit element, based on resistance type. On the other hand, the study for other type except resistance type has been rarely conducted for the application of YBCO coated conductor to SFCL as an current limit element. Consequently, in this study, YBCO coated conductor with different stabilization layer Cu and Stainless steel, is applied to SFCL using iron core and coil, and examine the many index points as an current limit element, such as current limit characteristic, the tendency of resistance occurrence, response time, the temperature trend for stability.

Speaker: Ho Ik Du (Chonbuk National University)

Wed-Mo-Po3.08-12_presentation materials.pdf

Wed-Mo-Po3.09 - Current Limiters II

Conveners: Dr Mark Ainslie (University of Cambridge), Martin Eibach (GSI)

577 Wed-Mo-Po3.09-01 [63]: Fabrication and performance test of fault current limiting elements made of non-stabilizer coated conductors

For the application of superconducting wires to fault current limiting devices, it is required that they have a high rated voltage when a fault occurs. Stabilizer-free coated conductors, particularly, shows a good performance for the high rated voltage, which is beyond 0.6 V/cm. In this study, using the stabilizer-free coated conductors, we made fault current limiting devices and examined their characteristics. Fault current limiting devices were fabricated with a shape of the cylinder of a mono-filar coil winding. Stabilzer-free coated conductors were wound along the mono-filar coil line and the terminal parts between the wire and metal were soldered using In solder. Two kinds of devices were fabricated by a different method in the terminal joint, one was made by a soldering and the other was made by a soldering-free joint. Critical currents and resistance at the joint parts were measured. In addition, long-time current flowing tests were also carried out for the characterization of the fault current limiting devices.

Speaker: Ho Ik Du (Chonbuk National University)

Wed-Mo-Po3.09-01_presentation materials.pdf

578 Wed-Mo-Po3.09-02 [64]: Comparison of Fault Current Limiting Characteristics between the separated Three-phase Flux-lock Type SFCL and the Integrated Three-phase Flux-lock Type SFCL

We investigate the comparison of fault current characteristics between the separates three-phase flux-lock type superconducting fault current limiter(SFCL) and integrated three-phase flux-lock type superconducting fault current limiter(SFCL). The single-phase flux-lock type SFCL consists of two coils. The primary coil is wound in parallel to the secondary coil on an iron core and superconducting elements are connected to secondary coil in series. Superconducting elements are used by the YBCO coated conductor. The separated three-phase flux-lock type SFCL consists of single-phase flux-phase type SFCL in each phase. But the integrated three-phase flux-lock type SFCL consists of three-phase flux-reactors wound on an iron core. Flux-reactor consists of the same turn's ratio between coil 1 and coil 2 for each single phase. To compare the current limiting characteristics of the separated three-phase flux-lock type SFCL and integrated three-phase flux-lock type SFCL, the short circuit experiments are carried out fault condition such as the single line-to-ground fault. The experimental result shows that fault current limiting characteristic of the separated three-phase flux-lock type SFCL was better than integrated three-phase flux-lock type SFCL. And the integrated three-phase
flux-lock type SFCL has an effect on sound phase.

Speaker: Ho Ik Du (Chonbuk National University)

Wed-Mo-Po3.09-02_presentation materials.pdf

579 Wed-Mo-Po3.09-03 [65]: Design and Test of 6 kV / 140 A Conduction Cooled Flux Coupling Type Superconducting Fault Current Limiter

The paper presents the design and test results of a conduction cooled flux coupling type superconducting fault current limiter. The 6 kV / 140 A SFCL was tested with a 2500 MVA short-circuit generator at a high power test facility. The design of the limiter consists of two parallelly connected and magnetically coupled windings cooled by single stage cryocooler. Magnetically compensated windings made of REBCO tape gives a very low voltage on the limiter at a nominal current. Windings were connected to cooper current leads and cooled down to 72 K. This paper summarizes the design and the experimental results of SFCL short circuit tests.

Speaker: Dr Michal Majka (Lublin University of Technology)

580 Wed-Mo-Po3.09-04 [66]: The application of hybrid-type DC SFCL in shipboard MVDC system

With the development of integrated power system (IPS) applications in navy, medium voltage direct current (MVDC) for shipboard electrical distribution is widely focused on. Compared with medium voltage alternating current (MVAC), MVDC is more adequate and affordable to meet electrical demand of future destroyer. However, one of the bottlenecks restricting the development of MVDC in shipboard is the occurrence of fault current. In order to ensure that fault current is limited within the on-off capability of the protection device, a hybrid-type DC superconducting fault current limiter (SFCL) is designed to protect MVDC in shipboard from two typical short circuit faults. In this paper, the working principle and mathematical model of the hybrid-type DC SFCL are analyzed. Two typical short-circuit fault conditions in shipboard MVDC system are chosen to be the backgrounds. The optimal installation position of the SFCL is selected and confirmed from different positions by simulation. Finally, the prototype experiment is conducted to verify the validity and feasibility of the SFCL applied to shipboard MVDC system. The verification results show that the SFCL has fast response speed and good current limiting effect in shipboard MVDC system.

Speaker: Ms Zheng Li (Huazhong University of Science and Technology)

MT_poster.pdf

581 Wed-Mo-Po3.09-05 [67]: Voltage Distribution Research on Flux-Coupling-Type SFCL

The level of short circuit current in power system is increasing rapidly, flux-coupling superconducting fault current limiter based on paralleled superconducting windings can effectively limit short-circuit current by the increased impedance after decoupling of the windings. The superconducting windings of high coupling factor is the core component of this SFCL, and the voltage distribution of windings may be uneven depending on the winding type and operating condition, this could affect the insulation and quenching of superconducting windings. In this paper, the voltage distribution of pancake-winding and layer-winding is theoretically analyzed, then simulations considering different operating conditions were carried out, two prototypes were processed and the experiment results are in accordance with simulation to some degree, at last the difference of two winding types is analysed based on data.

Index terms: flux-coupling SFCL, voltage distribution, pancake-winding, layer-winding

Speakers: Zhiwei Cao (Huazhong University of Science and Technology), Li Ren (Huazhong University of Science and Technology), Guilun Chen (Huazhong University of Science and Technology)

MTposter-czwei.pdf

582 Wed-Mo-Po3.09-06 [68]: Technical and Economic Analysis of Resistive Superconducting Current Fault Limiter with Parallel Shunt Resistance

The resistive superconducting fault current limiter (RSFCL) is widely used in high voltage direct current transmission based on modular multilevel converter (MMC-HVDC) to effectively limit the fault current and facilitate the interruption of the DC circuit breaker. During current limiting process, the RSFCL needs to withstand an overcurrent impact with a magnitude of several times the critical current, and the temperature rise could leave irreversible damage on its superconducting properties. In order to protect the superconducting tapes, the RSFCL is usually connected with a parallel shunt resistance which can divert part of the fault current. However, the shunt resistance will affect the current limiting performance of RSFCL, and need to consume more superconducting tapes under the same equivalent resistance. This paper will discuss the technical and economic performance of RSFCL with shunt resistance. Using finite element software, the temperature rise and the quenching resistance of the RSFCL will be calculated, and the results will be compared with the case without shunt resistance in terms of current limiting performance, fault response speed, superconducting tape consumption, and temperature rise. This work is expected to be the reference for the RSFCL design and optimization.

Speakers: Mr Xiangyu Tan (Huazhong university of science and technology), Mr Siyuan Liang (Huazhong university of science and technology), Ms Sinian Yan (Huazhong university of science and technology), Ms Zheng Li (Huazhong university of science and technology), Mr Guilun Chen (Huazhong university of science and technology)

谭翔宇 海报 MT poster.pdf

583 Wed-Mo-Po3.09-07 [69]: Electromagnetic field analysis of resistive superconducting fault current limiters for DC applications

With the development of DC power supply systems, breaking capacity of circuit breakers has been increasingly unable to meet the growing requirements for DC system short-circuit current level. To ensure the safety of the systems, a fault current limiter must be used in series with circuit breakers. The properties of superconducting fault current limiters such as fast reaction rate, simple structure, small size have caused widespread concern, the research on superconducting fault current limiters is becoming a hotspot in the field of DC system protection.
In the paper, a transient FEM computational model of resistive superconducting fault current limiters is established. Using the model, the transient magnetic field distribution and the inductance of superconducting coils, and the electromagnetic force on the coils are calculated. Based on the transient FEM computational model of the electromagnetic field, the field-circuit combination method is used to calculate the current and voltage in the coil of the resistive superconducting fault current limiter, and the influence of temperature on them when a short circuit occurs in the power system. Using the results of theoretical calculation, the short-circuit characteristics of resistive superconducting fault current limiters with different structures and geometries are studied.
In addition, an experimental model of resistive superconducting current limiters, which is used to verify field calculation results, is developed, and the relevant data are measured.
The results of the paper can be used for performance analysis and optimization design of resistive superconducting current limiters.

Speaker: Prof. Dong Xia (Chinese Academy of Sciences)

584 Wed-Mo-Po3.09-08 [70]: Magnetizing Characteristics of Bridge Type SFCL with Simultaneous Quench Using Flux-Coupling

With the development of modern power systems, the generation of fault currents and the system sensitivity to fault currents have increased. A superconducting fault current limiter (SFCL) is emerging as an alternative to reducing such fault currents in alternating current (AC) and direct current (DC) systems. SFCL can perform faster current limit operation as well as automatic fault current detection and recovery, regardless of fault type. Conventional bridge type SFCL applicable to DC systems requires a controller and an interrupter to protect the superconducting coils due to faults. This conventional method has a disadvantage that the configuration cost and control are somewhat complicated.
In this paper, a flux-coupling type SFCL using only two HTSC elements and two coils was fabricated to analyze the fault current limiting characteristics in a DC system. Before and after the accident, the current limiting operation and the voltage waveforms of each device were compared. We also analyzed flux linkages and instantaneous powers of flux-coupling type SFCL composed of HTSC elements with different critical currents. During the fault period, the magnetization power area and the flux linkage's operating range variation according to the magnetization current were compared with each other.

Speaker: Seok-Cheol Ko (Kongju National University)

MT26-dual-발표자료.pdf

585 Wed-Mo-Po3.09-09 [71]: Fault Current Limiting Characteristics of a Small-Scale Bridge Type SFCL with Single HTSC Element Using Flux-Coupling

In recent years, power devices using direct current are increasing rapidly. Especially, the development of renewable energy including photovoltaic power generation has led to the expansion of direct current (DC) power generation sources, so that interest in DC systems is increasing. However, the obstacle in the DC system is that dc circuit breaker (DCCB) is still under development. In this regard, it is necessary to appropriately apply the superconducting fault current limiter (SFCL) already developed for the alternating current (AC) system to the DC system.
Therefore, in this paper, a flux-coupling type SFCL using a single high-temperature superconducting (HTSC) element is proposed to mitigate the effect of DC short circuit. First, the operating principle and mathematical model of a flux-coupling type SFCL using a single HTSC element in a DC system are presented. After the fault occurrence, we analyze the current limiting operation and voltage characteristics of the DC fault current, the power load characteristics of each device, and the energy region characteristics of the two coils and HTSC element in the proposed SFCL. Experimental results show that applying this SFCL can help to suppress DC fault current, compensate for DC voltage drop and maintain power balance. As a result, the robustness of the low voltage direct current system for DC short circuit accidents can be greatly improved.

Speaker: Seok-Cheol Ko (Kongju National University)

MT26-single-발표자료.pdf

586 Wed-Mo-Po3.09-10 [72]: Study on Coordination of Resistive SFCLs and Hybrid-Type Circuit Breakers to Protect a HVDC System with LCC and VSC Stations

To efficiently protect a high voltage direct current (HVDC) system containing line commutated converter (LCC) and voltage source converter (VSC), this study proposes to coordinate resistive superconducting fault current limiters (SFCLs) and hybrid DC circuit breakers (HDCBs) to clear the DC line fault. The principle modeling of the resistive SFCLs is stated, and the impacts of the SFCLs on the DC fault currents of the LCC and VSC stations are analyzed. In terms of that the DC fault current interruption involves multi-stages, the coordination time sequence between the SFCL and the HDCB in the LCC/VSC station is given. Using PSCAD/EMTDC, a 320 kV class HVDC system is created. The change of the SFCL size and the HDCB operation delay is simulated, and the performance indexes including the DC fault current level, breaking time and dissipated energy are compared. It is confirmed that the proposed approach is effective in handling the fault. Especially for the VSC station, the approach is to visibly reduce the DC fault current and shorten the transient voltage duration on the HDCB, and the dissipated energy of the HDCB is dramatically reduced. For the LCC station, the approach may act as a competitive backup to ensure a timely current breaking. As a result, the DC fault can be removed more rapidly and reliably.

Speakers: Prof. Lei Chen (Wuhan University), Dr Ying Xu (Huazhong University of Science and Technology)

MT26-Wed-Mo-Po3.09-10-poster-Chenlei.pdf

587 Wed-Mo-Po3.09-11 [73]: Application Study of a Flux-Coupling-Type SFCL for Low-Voltage Ride-Through Operation of a Virtual Synchronous Generator

In order to effectively solve the low-voltage ride-through (LVRT) issue of a virtual synchronous generator (VSG) under severe grid fault, this paper proposes and studies the application of a flux-coupling-type superconducting fault current limiter (SFCL). Since the magnetic flux of the SFCL has a high controllability and its current path can be flexibly adjusted to cause the quench of high temperature superconductor (HTS), the SFCL is able to rapidly show its current-limiting impedance to better fault transient behaviors. In the study, the SFCL is installed at the point of common coupling (PCC) of the VSG, and it will combine with the virtual impedance controller of the VSG to limit fault current and compensate voltage sag. Using the MATLAB software, the voltage-current fluctuations of the VSG and the flux linkage variation of the SFCL are evaluated, and different configuration ratios of the virtual impedance and the SFCL impedance are simulated. Based on the simulation results, we obtain a proper parameter scheme of the coupling transformer (CT) and superconducting component (SC) in the SFCL, whose current-limiting and magnetizing characteristics are verified to satisfy the LVRT requirements of the VSG. Meanwhile, it is found that the proposed approach enables to provide multiple contributions, such as reducing the voltage loss, increasing the synchronizing power and accelerating the fault recovery. In summary, the application potential of the SFCL for reinforcing the robustness of the VSG is well demonstrated.

Speakers: Prof. Lei Chen (Wuhan University), Ms Guocheng Li (Wuhan University)

MT26-Wed-Mo-Po3.09-11-poster-Chenlei.pdf

588 Wed-Mo-Po3.09-12 [74]: Numerical Analysis of the 6 kV / 140 A Conduction Cooled Flux Coupling Type Superconducting Fault Current Limiter.

Fault current is one of the basic threats to the elements of power systems. Fault current in a shorted circuit is usually many times greater than the current occurring during normal operation of the network equipment. Fault current flow can cause thermal and dynamic harmful effects on the operation of power equipment. Electrodynamic forces occurring during the fault current flow can mechanically damage electrical equipment. Any such damage causes costly and time-consuming repairs. A superconducting fault current limiter is an electrical device with low impedance under normal operating conditions that changes into a state of high impedance during a short circuit, limiting the fault current. Superconducting limiters reduce the first, most dangerous peak fault current, thus protecting electrical system equipment from the dynamic effects of the fault current flow. In recent years the superconducting resistance fault current limiter for networks with rated voltage of 6 kV and rated current of 140 A with the possibility of overloading to 420 A was designed and tested. The limiter is conduction-cooled by means of a single-stage cryocooler. It is first Polish superconducting limiter for 6 kV network which uses conduction cooling. Changing the cooling method of the superconductiong limiter from liquid nitrogen bath to conduction cooling allows to increase the nominal current of the limiter by cooling the windings to lower temperatures and effectively limit several consecutive short circuits. The prototype of the limiter was tested in the Research Laboratory of Distribution Apparatus of the Electrotechnical Institute and installed for test in the GS2 110 kV / 6 kV switchgear in the Electrotechnical Institute in Warsaw. This paper presents the numerical model and the calculated electrical parameters of the new 6-kV class SFCL prototype.

Speaker: Dr Michal Majka (Lublin University of Technology)

Wed-Mo-Po3.10 - Conductors for Large Scale Applications

Conveners: Cesar Luongo (ITER Organization), Jeseok Bang (Seoul National University)

589 Wed-Mo-Po3.10-01 [75]: Study of superconducting strands damage and mechanical characteristics by different shape of CICC conductors

In order to optimize the structure design of CFETR TF conductor, the influence of rectangle and square conductor on the current transport performance is demonstrated. To analyze the mechanical structure and strands damage caused by different shape, a square and a rectangular experimental conductor were designed and manufactured by ITER TF and CFETR CSMC cable design. The indentation damage and cross-sectional distribution of these conductors are counted. The effects of square rectangle and circular conductor structure on material damage caused by internal conductors are compared and analyzed. The mechanical characteristics of different shape conductors and the damage on the strands are also discussed.

Speakers: Dr Chao Dai (Institute of Plasma Physics, Chinses Academy of Science), Jinggang Qin, Mr Zichuan Guo (Institute of Plasma Physics Chinese Academy of Sciences)

Study of superconducting strands2.pdf

590 Wed-Mo-Po3.10-02 [76]: Conductor Design of the Madmax 9 T Large Dipole Magnet

Madmax (MAgnetized Disc and Mirror AXion) project is an experiment dedicated to the discovery of the axion particle, the mass of which is expected in the range of 100 µeV. A square-field integral value of 100 T²m² with a  5 % homogeneity over 2 meters along the axis is required. The conductor has been designed to minimize the global magnet cost while fulfilling the following constraints: the hot spot temperature must kept below 100 K, the voltage below 2 000 V, and mechanical Von Mises stress below 165 Mpa. This has led us to design the largest world dipole with a warm bore of 1.3 m and a central field of 9 T. Its overall total length is of 6 m, the total weight is of 200 tons, including 40 tons for the windings. We made the choice of NbTi technology. The engineer current density is of 50 A/mm² and the nominal current 25 kA. With such large dimensions and field, a pre-stressed coil is difficult to obtain. As a consequence, the large forces over the conductor blocks during current ramping will induce some displacement and thus heat losses by friction. So to guarantee the magnet stability during that phase, we made the choice of a wetted magnet: a superfluid helium channel will take place in the conductor stabiliser. Then, the stress must be carefully managed around this hole. At last, the protection aspects will be also reviewed.

Speaker: Christophe Paul Berriaud (DAPNIA)

Madmax conductor-MT26 .pdf

591 Wed-Mo-Po3.10-03 [77]: Nb3Sn Wind & React conductors and joints for the low field grades of a layer wound DEMO TF coil

The conceptual design of the superconducting magnet system for the DEMO tokamak is being carried out in Europe since a few years. The Toroidal Field (TF) coil requirements and main geometrical features have undergone a series of changes, as a consequence of iterations leading to system-level machine optimization. In particular, solutions with 16 or 18 TF coils have been investigated, operating in the magnetic field range between 12 T and 13 T. At the same time, within the magnet design team different design concepts for the superconducting coils have been investigated, considering Wind & React (W&R) or React & Wind (R&W) manufacturing approaches, as well as layer- or pancake-wound coils. Among various possibilities, ENEA is involved in the design of a layer-wound TF coil, based on rectangular-shaped Cable-in-Conduit conductors and W&R manufacturing approach. In previous years, the feasibility and performance of a large-size Nb3Sn conductor operating at about 82 kA in a 13 T field has been demonstrated. Another key aspect for a layer-wound TF coil has been considered to be the demonstration of a joint between two different conductor grades, and to be possibly manufactured in-line during winding. Beside its feasibility, the performance of a joint between low-field conductor grades, i.e. constituted of a low number of superconducting strands and a high number of stabilization copper wires, had to be verified. Two conductor lengths of the low-field grades have thus been manufactured, characterized by a different number of superconducting wires and different outer dimensions, with an inter-layer joint between them. A sample has been assembled, for a test to be carried out at the SULTAN facility of the Swiss Plasma Center. The present paper summarizes the main features of the conductor design and the manufacturing steps of the two lengths and the connecting joint.

Speaker: Luigi Muzzi (ENEA)

muzzi_mt26_poster_demo cicc and joint_v1_red2.pdf

592 Wed-Mo-Po3.10-04 [78]: Post-mortem mechanical investigation of ITER TF conductor samples after heat treatment and SULTAN testing

The electrical performance of cable-in-conduit conductors made from Nb3Sn superconductor can degrade during operation, depending on the operating parameters selected and the cable pattern and geometry. In this study, we perform a comparative destructive examination on two identical ITER TF conductor sections, one of which is heat-treated but untested, and the second of which has been tested to the full IxB Lorentz force envisioned for ITER operation. We compare the level of macroscopic mechanical damage, microscopic filament breakage, and the distribution of strand positions within the conductor cross-sections to understand the origins of the performance degradation. Combined with future examination of reduced IxB samples, we expect this method to help elucidate some mechanisms of the performance degradation.

Speaker: Prof. Matthew C. Jewell (Materials Science Center, University of Wisconsin-Eau Claire)

ITER TF conductor poster MT26.pdf

593 Wed-Mo-Po3.10-05 [79]: Cable Compaction as a Possible Factor to Reduce Tcs Degradation of ITER Toroidal Field Conductors

The testing of samples of “cable in conduit conductors” (CICC) made of Nb3Sn and copper strands for ITER toroidal field coils in general cases demonstrated the degradation of current sharing temperature Tcs under cycling electromagnetic loads [1]. This is mostly because of a movement of superconducting strands under Lorentz forces inside a cable that causes the cracking of brittle Nb3Sn filaments. Samples of toroidal field conductors delivered from Russia demonstrated less or almost no degradation under cycling electromagnetic forces in comparison with other suppliers [2]. Some suggestions have been pronounced about reasons of such behavior, for example larger surface roughness of the strands coated by chromium [3]. In this paper we suggest that some peculiarities in compaction of CICC could lead to higher density of strands in outer layers that prevents their movement and improve behavior under cycling load. Some factors affected the stability of Tcs are discussed and the suggestion to reduce Tcs degradation by the extra compaction of cables has been considered.
[1] A. Devred, et al, Superconducting Science and Technology, No.27, 2014, Article: 044001.
[2] M. Breschi, et al, Superconducting Science and Technology, No.30, 2017, Article: 055007.
[3] C. Sanabria, et al, Superconductor Science and Technology, Volume 29, Number 7, 2016, Article 074002

Speaker: Vitaly Vysotsky (Russian Scientific R&D Cable Institute)

594 Wed-Mo-Po3.10-06 [80]: Research on non-destructive examination of NbSn3 cables based on the method of inversion of electromagnetic property

Superconducting cable is an important component of CICC conductor. The quality of the cable is the guarantee to ensure safe operation of superconducting conductor, and the key step to reduce the degeneration of superconducting conductor performance. The cables will be sustained extremely complex stress during manufacturing process, which is easily cause damage on strands and influent conductor performance. However, the spiral structure caused by irregular cabling with multiple materials, cores, and layers strengthen the complexity of CICC, which also brings more difficulties on R&D of non-destructive examination (NDE) of cable inspection. On the basis of electromagnetic NDE, this paper proposed a method based on inversion of electromagnetic property, and explores relative characteristics of cable damage single and magnetic leakage signal, as well as the synchronous NDE quantitative evaluation method through the combination of theoretical model and experimental research. Meanwhile, the wavelet transform is used to extract characteristics and reduce noise for strands signal, and then extract defect signal, which realizes the effectiveness of the new evaluation method in complex environment.

Speaker: Mrs Xiaochuan Liu ( Institute of Plasma Physics Chinese Academy of Sciences)

poster-Wed-Mo-Po.3.10-06.pdf

595 Wed-Mo-Po3.10-07 [81]: AC loss, contact resistance, and cabling degradation analysis of various Nb3Sn sub-size CICC cable designs

The superconducting cables for magnet systems in nuclear fusion reactors usually adopt the Cable-in-Conduit conductor (CICC) concept. CICC cables are known for higher thermal stability compared to other cable designs. Selection of a suitable cable design for higher operational performance still remains a challenge. The maximum magnetic field in future fusion reactors like DEMO and CFETR may reach up to 15 T, cable designs that can withstand electromagnetic loads at these higher fields, at the same time minimizing coupling losses, require thorough analysis.

Therefore, six sub-size CICC cables made of Nb3Sn strands are manufactured and tested experimentally on AC coupling loss, interstrand contact resistance, and cabling degradation. The inter-strand coupling loss and contact resistance are analyzed with the numerical code JackPot ACDC, developed at the University of Twente, to find an optimal cable pattern. Transport current degradation is measured on a few selected strands in the cables and strand indentation from cabling and compaction are analyzed as well.

Among six cables, four are design variations of a cable pattern with close-to-one twist-pitch-ratio as earlier found as an optimization for coupling loss and transverse load. For this so-called Twente cable design, variations have been chosen in twist pitch length and void fraction. Remaining cables are CWS-I, based on the Copper Wound Superconducting strands design and the CFETR Central Solenoid Model Coil (CSMC) design, proposed by ASIPP. The CWS design is aimed at reducing superconducting strand pinching causing degradation of transport properties mainly during compaction and possibly also at cyclic loading, by using soft copper strand inclusion. The CSMC cable pattern is close to the ITER CS cable design and is taken as a reference for comparison. The study of coupling loss and mechanical deformation on Nb3Sn cables is also relevant for other strain sensitive materials like MgB2 and BiSSCO round wires, potentially to be used in CICC as well.

Speaker: Anvar V A (University Of Twente)

MT26 AC loss Rc, and Ic analysis of various Nb3Sn sub-size CICC cable designs V5.pdf

Wed-Mo-Po3.11 - Quench and Normal Zone Behavior II

Conveners: Fedor Gömöry (Institute of Electrical Engineering, Slovak Academy), Honghai Song (Brookhaven National Laboratory)

596 Wed-Mo-Po3.11-01 [88]: Quench analysis of no-insulation magnet using YBCO coated conductor tapes with copper cladding

No-insulation (NI) high-temperature superconductor (HTS) coil which have self-protecting feature when quench have been presented for several years, HTS magnet using NI technique also have been applied, however, the quench behavior need to be calculated and analyzed. With the charging delay of our magnet satisfied, YBCO coated conductor tapes with copper cladding are used which have better safety and heat stability. Usually the partial element equivalent circuit (PEEC) model is proposed for the numerical simulation of an NI HTS coil, but it often require substantial computation time especially as a NI magnet having many coils, so a simply circuit model with a single inductor with a resistor in series and a resistor in parallel is used for numerical simulation of the magnet which have four pancake coils in series with a yoke. A three-dimensional quench simulation of the magnet has been carried out in OPERA-quench, the current, voltage, temperature and normal zone propagation with respect to time are analyzed, the influence of the yoke is also discussed.

Index terms: Quench analysis, No-insulation, high-temperature superconductor coil.

Speaker: Shijun Zheng (Institute of Modern Physics，Chinese Academy of Sciences)

597 Wed-Mo-Po3.11-02 [89]: Quench Analysis of an LTS Quadrupole Triplet Magnet System for the IBS RAON Inflight-Fragment Separator

In this paper we present quench analysis results of a Low-Temperature Superconducting (LTS) quadrupole triplet magnet system, a part of the In-flight Fragment (IF) separator of a heavy ion linear accelerator complex, named RAON, currently being constructed by the Institute of Basic Science (IBS). This magnet system is composed of three quadrupole magnets: a triplet, surrounded by iron yokes and embedding hexapole/octupole LTS coils for field correction. The magnet will be operated at 4.2 K in liquid helium. For reliable and safe operation of this complex superconducting system, quench and protection analysis with possible failure scenarios must be performed. In this paper, we first discuss probable quench scenarios and then present results of the quench propagation analysis on: 1) coil currents and voltages by multi-coil model circuit analysis; and 2) simulated temperature distribution inside each coil. Our quench analysis results show that the maximum voltage and temperature in each coil are below safety limits, 2000 V and 150 K, respectively, and confirm that this quadruple triplet magnet system is self-protecting.

Acknowledgement: This work was supported by the Rare Isotope Science Project of Institute for Basic Science funded by Ministry of Science and ICT and NRF of Korea (2013M7A1A1075764)

Speaker: Dr Wooseung Lee (Massachusetts Institute of Technology, Francis Bitter Magnet Laboratory / Plasma Science and Fusion Center)

Wed-Mo-Po3.11-02 [89]_Contents_W.Lee-ver.2.1.pdf

598 Wed-Mo-Po3.11-03 [90]: A fast turnaround experimental platform for testing quench initiation and detection of REBCO coated conductors for high-field magnet applications

High-field magnet technology based on REBCO coating conductor is facing several critical challenges, one of which being quench detection and protection in various working conditions with or without strong stresses. We describe a fast turnaround experimental platform for testing quench initiation and detection of REBCO coated conductors for high field magnet applications.
It is essentially a single-layer coil wound from 2 m long REBCO tapes that we can test a couple of such coils a day at a temperature ranging from 4.2 K to 77 K and in a background field of up to 15 T (at 4.2 K). It is adapted from a spiral coil technique that was successfully used to test the degradation limit of Bi-2223 and Bi-2212 wires carrying a large current in a high magnetic field and subjecting to a strong axial stress during a quench.
We describe results of our experiments on coated conductors with different thickness of copper stabilizers at different temperatures, different magnetic fields, and with or without axial stresses. The experimental results are compared with the numerical results by a quench simulation code.

Speaker: Xijie Luo (Kyoto University)

Wed-Mo-Po3.11-03.pdf

599 Wed-Mo-Po3.11-04 [91]: A Lumped Circuit Model for No-Insulation Pancake Coil to Consider Fast Electromagnetic Quench Propagation

This paper proposes a new lumped-circuit model that has been modified from the conventional one to demonstrate the fast electromagnetic quench propagation among electromagnetically-coupled no-insulation high temperature superconductor (HTS) coils. Recently, multiple groups have reported that the conventional lumped-circuit model, which has well demonstrated charging and discharging behaviors of an NI magnet, could not account for post-quench behaviors. Specifically, terminal voltages of individual pancake coils were estimated to be too high than the simulated ones. This paper proposes a new lumped circuit model that focuses on the post-quench simulation of an NI HTS magnet. The key idea is to incorporate a new circuit element that may physically represent the fast electromagnetic quench propagation in the magnet. First, we define key assumptions and justify the use of the new element theoretically. Then, we apply our new model to selected high field NI HTS magnets. The simulation results with the new model are compared with experimental results as well as those simulated using the conventional lumped-circuit model.

Acknowledgement
This work was supported by Samsung Research Funding & Incubation Center of Samsung Electronics under Project Number SRFC-IT1801-09.

Speaker: Chaemin Im (Seoul National University)

MT26_Wed-Mo-Po3.11-04_Quench_CI_20190920[2541].pdf

MT26_Wed-Mo-Po3.11-04_Quench_CI_20190920[2541].pptx

600 Wed-Mo-Po3.11-05 [92]: Numerical and Experimental Analysis of Thermal Stability of Superconducting Windings Using a YBCO Core Cable

High-temperature superconducting (HTS) device is a new application of superconducting technology in the electric power network. It shows several advantages, including small volume, light weight, high efficiency, strong capability of overload, and risk-free of fire. In this paper, we designed a core cable based on the adiabatic conditions, and then realized both numerical and experimental analysis to determine the minimum quench energy and quench propagation velocity of superconducting winding using the core cable.
Section I briefly introduces the background of YBCO cable application and stresses the quench analysis for the power system application. When HTS devices run in the power system, the superconductive tapes may quench due to power system fault and endure electromagnetism and mechanical stress caused by large or unbalanced current. In Section II, the structure of the prototype core cable is shown first and then the quench test facilities, as well as the experimental procedures, are presented.
Section III deals with the 3D transient modelling of this YBCO core cable using newly developed T-A formulation [1-2]. The numerical results are proposed to analyze the curves of temperature and voltage under quenching condition with different thermal disturbance. With the combination of the stability theory, we estimate the quench propagation velocity and analyze the factors affecting quench propagation velocity and minimum quench energy. It is obtained that the minimum quench energy of the core cable is related with the transmission current.
The paper is concluded in Section IV. The results show that the thermal stability of the core cable is related with transmission current and the longitudinal quench propagation velocity of core cables ten times as much as the velocity in superconducting tapes.

[1] Zhang Huiming, Zhang Min, Yuan Weijia. An efficient 3D finite element method model based on the T–A formulation for superconducting coated conductors[J]. Superconductor Science & Technology, 2017, 30(2):024005.

Speaker: Dr Deng Xiangli (Shanghai University of Electric Power)

601 Wed-Mo-Po3.11-07 [93]: Analysis of the influence of hot spots on the design of DC resistive SFCLs

When High-temperature Superconducting Coated Conductors (HTS-CCs) are subject to a transport current of the order of the critical current, their low thermal diffusivity and nonuniform critical current density can easily lead to the appearance of destructive hot spots. The transition to the normal state probably causes the degradation of superconducting properties in HTS-CCs. In recent years, several valid methods to detect and protect against hot spots have been proposed, but their impact on the design of HTS-CCs based DC resistive Superconducting Fault Current Limiters (SFCLs) is not yet fully understood. In this manuscript, we will present numerical models that enable the simulation of hot spots on HTS-CCs and the prediction of their influence on the performance of DC SFCLs.

Speaker: Mr Jiabin Yang (University of Cambridge)

2019 MT Poster-Jiabin Yang.pdf

602 Wed-Mo-Po3.11-08 [94]: Investigation on Quench and Normal Zone Propagation Characteristics of 2G HTS Racetrack Coil with Metal-Insulator Transition Insulation Material

In this study, the quench initiation and propagation characteristics of second generation high temperature superconducting race-track coil (2G HTS RTC) are investigated in both experiment and simulation. This RTC is insulated by the metal-insulator transition (MIT) insulation material which has a variability of the contact resistance as a function of temperature. First, thermal quench tests with constant operating current and heater activation are performed to investigate the heat transfer characteristics of MIT RTC, such as the minimum quench energy and the transverse and longitudinal normal zone propagation velocities at the curve and straight section of RTC. Then, experimental results are compared and discussed with results of numerical simulation using finite element method.

Acknowledgment: This work was supported in part by the "Human Resources Program in Energy Technology" of the Korea Institute of Energy Technology Evaluation and Planning (KETEP), granted financial resource from the Ministry of Trade, Industry & Energy (MOTIE), and by Korea Electric Power Corporation. (Nos. 20184030202200 and R18XA03).

Speaker: Mr Huu Luong Quach (Jeju National University)

603 Wed-Mo-Po3.11-09 [95]: Experimental study on the quench characteristic of YBCO tapes with different arranggements

Abstract: Because the current carrying capacity of a single superconducting tape is limited, in some practical superconducting devices, multiple tapes need to be used in parallel. Due to the inhomogeneity of the tape and their uneven current distribution, hot spots are easily formed on some of the tapes when the superconducting device passes through large current. The normal zone will not only spread in the tape containing local hot spots but also expand to other tapes parallel to them, eventually causing damage to the whole superconducting device. The research on the quench characteristics of stacking tapes and parallel tapes, which are two typical arranggements, has guiding significance for thermal stability evaluation and protection system design of superconducting devices. In this paper, Normal zone propagation velocity (NZPV) and minimum quench energy (MQE) of single-length tape, stacking double tapes and parallel double tapes were measured at the liquid nitrogen temperature. The quench propagation characteristics of parallel structure and single strip were compared. The experimental results show that NZPV of tape containing hot spots in parallel structure is slower than that of single strip due to the shunt effect.
Keywords: Quench propagation, YBCO tapes, Parallel structure, Normal zone propagation velocity, Minimum quench energy

Speaker: DongSheng Pu (State Key Laboratory of Advanced Electromagnetic Engineering an)

Wed-Mo-Po3.12 - Motors IX

Conveners: Hao Chen (China University of Mining & Technology), Qiuliang Wang (IEE CAS)

604 Wed-Mo-Po3.12-01 [96]: Design of a Novel Axial Flux Rotor Consequent-Ploe Permanet Magnet Machine

In this paper, a novel 3-phase 12/10-pole rotor-permanent magnet (PM) hybrid excited axial switched-flux (RPM-HEASF) machine is proposed and investigated, which exhibits high power/torque density, wide speed-regulation range, and good overload capability, and is interesting for electrical vehicle (EV) or hybrid EV applications.
The RPM-HEASF machine contains double-outer-stator and single-inner-rotor, and the two outer stators have same structure. The armature and excitation windings are remained in stators, while the PMs with interlaced magnetized direction are embedded in the rotor. The stator consists of 6 E-shaped modular core units, and the excitation windings are wound around the middle teeth of the stator units which provide physical and magnetic isolation between the armature windings. There are 10 sandwich units in the rotor and the sandwich unit is composed of two rotor teeth and one PM. By injecting the positive or negative DC exciting current in the excitation windings, the air-gap field can be regulated in a wide range. Hence, the hybrid excitation operation is implemented and the operation principles are investigated in detail.
Based on the flux-regulation range and output torque, the optimization design is carried out and the key dimension parameters are obtained. The main electromagnetic performance of the novel RPM-HEASF machine is investigated and analyzed by 3-D finite element method, including the magnetic field distribution, air-gap flux density, open-circuit PM flux-linkage, back-EMF, torque characteristic, as well as flux-regulation principles and capability.
The results indicate that the RPM-HEASF machine has essentially sinusoidal and symmetrical PM flux-linkage and back-EMF under PM and hybrid excitation mode, and is very suitable for brushless AC operation. Moreover, by injecting a small DC excitation current, the air-gap field can be flexibly controlled and the machine can attain a low-speed large-torque and wide-speed constant-power operation range. By placing the PMs in the rotor, the torque output capability is better while the torque ripple is smaller. Hence, the proposed RPM-HEASF machine is very attractive for EVs/HEVs application.

Speaker: Deyang Fan (Jiangsu University)

Wed-Mo-Po3.12-01 [96](1).pdf

605 Wed-Mo-Po3.12-02 [97]: Measurement of eddy current loss of permanent magnet with higher frequency and temperature effects

The use of a permanent magnet (PM) to achieve high performance and high efficiency in the modern motor and generator industry technology has increased rapidly. In the design process, one needs to consider the magnetic properties and the eddy current loss due to high conductivity in long term operating condition. Due to high eddy current loss the temperature of the permanent magnet increases which increases the chance of thermal demagnetization and completely irreversible loss of magnetic properties. For measurement of AC loss of PM under the presence of an external magnetic field as synonymous to operating permanent magnet synchronous machine (PMSM), closed loop magnetic measurement system is designed, developed and manufactured. With this symmetrical closed magnetic measurement system, the loss of the PM is measured with varying frequency and for varying temperature. Two different shaped of PMs which are used in PMSM is evaluated from this measurement setup. Most promising improvements in magnetic measurement and loss calculation can be analyzed and investigated.
Initially, the AC loss in PM is measured under sinusoidal conditions to verify the FEM PM loss model. The AC loss measurement is further validated using the thermal measurement for AC loss calculation. The accuracy of the AC loss measurement method is improved by modifying the measurement coils using the printed circuit board (PCB) to measure the induced voltage due to eddy current in the PM. Then it is used for measurement of AC loss under non-sinusoidal excitation. The non-sinusoidal excitation signal is generated either using a function generator or pulse with modulated (PWM) inverter. In this paper, the calculated and the measured AC loss in PM under sinusoidal and non-sinusoidal excitations with different harmonic contents are compared with higher frequency and temperature effects.

Speaker: Nijan Yogal (Physikalisch-Technische Bundesanstalt)

606 Wed-Mo-Po3.12-03 [98]: Experimental characterization of a no-insolation HTS racetrack coil in travelling magnetic fields

To investigate the electromagnetic characterization of HTS coil under a travelling magnetic field, a no-insolation racetrack coil was wound with YBCO tapes. For comparison, another HTS coil which has the same geometric and structural parameters was wound with insolated tape between the layers. The coils were injected with DC current and a flat stator which has traditional copper windings and a controllable three-phase inverter was introduced to provide travelling magnetic field. These HTS coils were respectively operated in the external magnetic field from the stator and the different voltage and current response of the coils was measured by experiments. In addition, finite element method was applied in this work to furtherly study the electromagnetic stability of the no-insolation coil which is potentially going to perform as the field magnet of a HTS linear synchronous motor.
Key words: HTS magnet, electromagnetic characterization, no-insolation magnet, travelling magnetic field

Speaker: Dr Kang Liu (Applied Superconductivity Laboratory, State Key Laboratory of Traction Power, Southwest Jiaotong University)

poster-mt26-Experimental Characterization of a No-insolation HTS Racetrack Coil Subjected to Travelling Magnetic Fields.pdf

607 Wed-Mo-Po3.12-04 [99]: Comparative Analysis of a Linear Electric Motor using Superconducting and Conventional Conductor Coil

Regarding a linear motion and forces the linear electric motors have a number of advantages over ordinary motors, the most obviously the lack of an intermediate gearbox to convert rotational motion into straight line motion saves energy. Essentially linear electric motors with conventional conductor (copper) coils are designed to produce high force at low speeds and the demand for these devices has increased for many industrial applications due they are directly coupled to the machine load, saving space, simplifying machine design and removing potential sources such as balls-crew systems, belts, etc. Actually, numerous industrial applications require even greater strength forces in compact size machines, so it is of interest to analyze, explore the efficiency and sustainability of using superconducting coils for these linear electric motors (LEM). This work contributes in determining the performance evaluation and comparison between conventional and superconducting coils used in LEM, also contributes in determining the increase of strength forces of these devices while using superconductor coils instead of conventional conductive material such copper. The work highlights the techno-economic aspects of using superconductive materials in the LEM coil. Moreover, the work shows the design characteristics and the electromagnetic analysis performance with finite element simulations and the experimentation results are presented. A small prototype (100W) of LEM with tubular characteristic was designed and manufactured; of the same size and characteristics was manufactured the LEM with superconducting material, this to determine and compare its output forces in both motors. Such comparison is necessary to justify the use of superconducting material both technically and economically in the LEM.

Speaker: Adrian Gonzalez-Parada (University of Guanajuato)

608 Wed-Mo-Po3.12-05 [100]: A novel permanent magnet linear motor for the application of urban transit

The surface-mounted permanent magnet linear motor (PMLM) is a good candidate for the application of urban transit due to its merits of high-power density and efficiency. However, this kind of machine needs a lot of permanent magnets (PMs) on the long stator structure, which is costly. To solve this problem, a novel PMLM has been proposed in this paper. The stator of novel PMLM has the consequent poles structure and the mover of novel PMLM has two iron cores, which sandwiches a PM. Firstly, the structure and operation principle of the PMLM have been investigated. Then, the key parameters, including the structure parameters, the back electromotive force, the efficiency, the force ripples are fully analyzed. Finally, for a fair comparison, the proposed motor is designed and built based on an existing PMLM with the similar electromagnetic and geometrical parameters. The performances of the novel PMLM are estimated and compared with the conventional surface-mounted PMLM, which indicates that the proposed PMLM can keep the same performances with the exciting PMLM. Moreover, it has the simple structure and can save about 50% of PMs, which can help reduce costs.

Speaker: Dr Cong Deng

609 Wed-Mo-Po3.12-06 [101]: A Study on Robust Design of Irreversible Demagnetization of IPMSM Rotor Core Using Dy-Free Permanent Magnet

Since only one tenth of the ore is deposited as rare earth elements, these elements are not common. However, these elements are constantly needed to be used to supplement the thermal demagnetization strength of the motor.
However, there are many cost variables and risks for continuous use of these elements, since these elements are mainly buried in only certain countries.
Recently, a lot of magnets excluding heavy rare earths have been studied by using the hot forming technique, but the coercive force of these magnets does not reach the coercive force of existing magnets. In order to apply these magnets to motors, robust design for non-reversible demagnetization must be accompanied with.
In this paper, we study the shape of the rotor with the maximized coercivity so that the motor made by using the permanent magnet without heavy rare earths can operate similarly to the motor made by using the permanent magnet at the actual motor operating temperature (150 ℃). By using the same specification of the existing 22Kw hybrid vehicle traction motor, the rotor parameters affecting the rotor demagnetization were changed to analyze the demagnetization and performance characteristics. We adopted the IPMSM structure which is small and efficient in consideration of the motor space constraint. As a result, we can propose various irreversible demagnetization design methods. The effect of the presence of demagnetization at the extreme temperature condition (200 ℃) and the performance of the demagnetization were analyzed by applying the demagnetization analysis conditions. In addition, the prototype was fabricated and tested to verify the validity of the study.

Speakers: Hyungsik Kong, Prof. Sung Gu Lee, Dr SuYeon Cho (KATECH), Mr Hyun-Jo Pyo, Mr Min-Jae Jeong, Mr Dong-Woo Nam, Prof. Won-Ho Kim

MT26_2019 Poster_Hyung_Sik.pdf

610 Wed-Mo-Po3.12-07 [102]: Design of IPMSM for Electric Oil Pump considering PM Irreversible Demagnetization at Saturation Temperature

When designing a motor, the motor should be designed to withstand harsh conditions, for it to operate at any extreme environment. For the motor that uses permanent magnet (PM), its irreversible demagnetization is undesired characteristic that has negative effect on motor performance. As interior PM synchronous motor (IPMSM) is often used for high torque density generation, its operation characteristic regarding PM irreversible demagnetization is considered as an important factor. In most cases however, PM irreversible demagnetization is analyzed considering ambient temperature of the motor. But for accurate analysis, the temperature of the PM should be taken into account, not the ambient temperature. Therefore, assumption on PM temperature is carried out based on operation and cooling condition of the motor. By employing derived PM temperature for motor analysis, more accurate operation characteristic will be derived in terms of both output performance and PM irreversible demagnetization. Then, the design parameters of the motor can be revised to reduced undesired phenomenon of the motor.

In this paper, design of Interior Permanent Magnet Synchronous Motor (IPMSM) for Electric Oil Pump (EOP) considering PM irreversible demagnetization is discussed. To begin with, base EOP motor is analyzed to satisfy operation requirement at its operating temperature. The saturation temperature of the motor is derived using MotorCAD, which is a powerful tool for electromagnetic and thermal performance analysis, based on the operating condition as well as the cooling condition for each operating points. With the derived saturation temperature, irreversible demagnetization of PM is analyzed under its load condition. Based on the analysis, design of the EOP motor is revised to enhance the demagnetization effect, and its PM irreversible demagnetization ratio is derived. Finally, the characteristic of the improved model is compared to that of the base model.

Speaker: Mr Dae-Woo Kim (Sungkyunkwan University)

Wed-Mo-Po3.12-07 [102]_MT26_Poster_Daewoo Kim.pdf

611 Wed-Mo-Po3.12-08 [103]: A study on the magnet structure for reducing demagnetization by grain boundary diffusion method

Permanent magnets are largely classified into ferrite magnets, Alico magnets, and rare earth magnets. Ferrite magnets and Alico magnets are significantly less magnetic than rare earth magnets. Therefore, when a rare-earth magnet is used, it is advantageous in size and weight because it uses less magnet than other magnets. Particularly, in the case of a magnet used in a vehicle, it is necessary to reduce the size and weight of the magnet. The motor used in the vehicle may have irreversible demagnetization depending on the temperature to be driven and the parameters to be applied. If a irreversible demagnetization occurs, the performance of the magnet is deteriorated, and the output characteristics of the motor can not be improved due to the failure of the motor. In this paper, the motors for ISG use rare earth magnets. Rare earth magnets can be caused irreversible demagnetization at high temperatures. The portion of the motor magnet where the irreversible demagnetziation occurs locally occurs more in the edge than in the central portion of the magnet. In the grain boundary diffusion, it is possible to selectively inject Dy and Tb into the rare earth magnet surface. Therefore, we distribute Dy and Tb components locally on the surface of the magnet and the edge where irreversible demagnetization can occur, thereby enhancing the coercive force and suggesting a method advantageous to irreversible demagnetization. The electromagnetic characteristics were analyzed by finite element method. Electromagnetic analysis is performed by using the ANSYS Electromagnetic Suite 19.0. We make a model applying grain boundary diffusion to the part where demagnetization occurs, and conduct a demagnetization experiment by conducting a single piece test with a normal magnet. Then, each magnet is mounted on the ISG model, and the electromagnetic characteristics test and the demagnetization test are carried out.

Speaker: Byungchan Kim (keimyung university)

612 Wed-Mo-Po3.12-09 [104]: Study on Reduction of Eddy Current Loss of Permanent Magnets in Ultra-High Speed Machines

This paper describes the analysis on the Number of Axial Segments of Permanent Magnet in SPMSM for Ultra-High-Speed Application; Electric-Turbo Compound System(E-TCS) for Construction Equipment. E-TCS is a device that combines a turbocharger, which is a regenerative device through exhaust gas, and a compressor to improve the turbo lag. As a result, E-TCS must be able to drive at least 80,000 rpm and require a large torque at low speeds. And because of scattering problem of permanent magnets, so limit to increase the rotor size and shaft length is relatively long. To increase performance of motor, difficulties of permanent magnetization and reduce permanent magnet loss, the segment must be applied in the axial direction on permanent magnet. Design criteria and power loss analysis of the ultra-high-speed motor are described by analytical method, and the results are validated by 3D-finite element method. And then, the prototype motor has been fabricated 3 cases and tested. The experimental results confirmed the validity of the proposed design and alalysis scheme of the ultra-high-speed SPMSM(Surfaced Permanent Magne

Speaker: Hyungkwan Jang (Hanyang University)

613 Wed-Mo-Po3.12-10 [105]: Design and Analysis of a Magnetless Linear Variable Reluctance Motor with Modular Mover Units for Electric Propulsion

Due to its stator robustness and the substitution of permanent magnets by DC field windings, the magnetless linear variable reluctance motor (MLVRM) possesses several advantages: high reliability, low cost and flexible flux regulation capability, which is a good candidate for rail transit applications. However, the MLVRM is essentially a doubly-salient machine, so there exists a drawback of large force ripples.

In this paper, a MLVRM with $n$-module mover units is proposed to suppress the force ripples. The proposed motor consists of a stator and a mover with $n$-module mover units. The stator is constructed with laminated iron core only, while each modular mover unit consists of armature windings, DC field windings and laminated iron core.

In order to suppress the force ripples and attain the highest back electromotive (EMF), two design conditions must be followed:

${d}=({k}+\frac{1}{n})\tau_s$, ${k}\geq{0}$ and ${n}\geq{2}$. Where ${d}$ represents the distance between two adjacent mover units; $\tau_s$ denotes the stator pole-pitch; ${n}$ indicates the number of the mover unit; ${k}$ is an integer.

$\alpha_{1}^{i}=\frac{i-1}{n}{360^\circ}$, ${i}=2,3...n$. Wherein, $\alpha_{1}^{i}$ represents the position between the ${i}$th mover unit with the first one, which is expressed in electrical angle. When ${0^\circ}\leq\alpha_{1}^{i}\leq{90^\circ}$ or ${270^\circ}<\alpha_{1}^{i}\leq{360^\circ}$ , the connection of the armature windings in the ${i}$th mover unit is the same as that in the first one. When ${90^\circ}<\alpha_{1}^{i}\leq{270^\circ}$ , the connection of the armature windings in the ${i}$th mover unit is the opposite to that in the first one.

In this paper, the utilization rate (UR) of the $n$-module mover units will be defined to measure the level at which the motor attains the highest back EMF. MLVRMs with $n$-module mover units (${n}\geq{2}$) are quantitatively evaluated by the finite element method. The anticipated results of the proposed MLVRM will possess a remarkable effect in reduced force ripples. In addition, the paper describes the process to optimize the number of modular mover units ($n$) for the proposed MLVRM capable in both suppressing force ripples and achieving a higher UR.

Speaker: T. W. Ching (University of Macau)

Poster.pptx

614 Wed-Mo-Po3.12-11 [106]: A Novel Three-phase Tubular Switched Reluctance Linear Machine with Transverse-flux path

Several tubular switched reluctance linear machines (TSRLMs) with transverse flux are proposed for improving thrust density recently. Owing to the particularity of the structure of transverse-flux TSRLMs, how to maximize the electrical utilization becomes a key to improve these machines’ performance. A novel three-phase transverse-flux TSRLM is proposed in this paper, whose stator sleeve is composed of six ferromagnetic rings and five spacer rings. And the mover is composed of an aluminum tube and several fan-shaped poles. The adjacent fan-shaped poles are placed at 120 degree intervals. The novel structure permits that the winding coils can be all through connections. This winding way helps addressing the problem of the coils placement that exists in other transverse-flux TSRLMs. In order to verify superiority of the novel TSRLM, a conventional transverse-flux TSRLM which has the same main dimensions is presented. The three-dimension finite element models of the machine electromagnetic field is established. The model and its boundary are shownFinally, the finite element calculation results show that the average thrust per unit core mass of proposed TSRLM is greater than conventional TSRLM. With the flux linkage data and co-energy data calculated by FE software, the dynamic simulation models of both TSRLMs are established in MATLAB/Simulink. The electrical simulations and generated simulations are conducted with these models. The closed-loop speed regulation simulations are conducted, which utilizes the PI regulator. In the PI regulator, the proportion coefficient is 7, and the integral coefficient is 15. In addition, the generation simulations with separately excited topologies of power converters are conducted. The power supply is 36V. The operation velocity is 2m/s. The current waveforms and output power waveform are presented. It proves that the novel structure can help increase the electromagnetic utilization of TSRLMs. It can be found that the ability in electromagnetic energy conversion is stronger. Thus, if one linear machine is used as a generator in direct-drive system, the structure of machine is a strong candidate.

Speaker: Prof. Hao Chen (China University of Mining and Technology)

MT26(2).pdf

615 Wed-Mo-Po3.12-12 [107] [Invited]: Superconducting Synchronous Motors for Electric Ship Propulsion

Synchronous electric machines with superconducting field windings have been around for a long time but have not gone beyond prototypes and very limited demonstrations. However, magnetic resonance imaging (MRI) systems use superconducting magnets that are made in significant volumes each year and run with high reliability. Leveraging significant technology advances in cryogenic systems engineering and electric machine design, it is possible to design commercially-viable superconducting electric machines with volumetric and gravimetric power densities that far exceed other types of AC machines. In addition, superconducting machines, with proper design, can offer efficiency benefits that can increase their value in ship propulsion applications beyond just saving space and weight.
This paper provides a brief review of the technology advances that move superconducting machines toward commercialization and then delves into a notional design of a superconducting synchronous motor rated for 36.5MW of shaft power at 120rpm that would be compatible with a 5kV DC bus. The interaction of the motor with its power electronic drive is also discussed, showing how the design of the motor and the design of the converter are coupled. The motor is based on low temperature superconducting field coils and an armature core with reduced steel. The 7T magnetic fields produced by the field coils result in an air gap magnetic field greater than 2T. The reduced use of magnetic materials yields a 100x reduction in the radial forces of attraction between the armature and field compared to a conventional machine, easing structural issues substantially. Some comparisons are made to homopolar superconducting machines.

Speaker: Michael Parizh (GE Global Research)

Wed-Mo-Po3.12 – SC Synchronous Motors for Electric Ship Propulsion.pdf

616 Wed-Mo-Po3.12-13 [108]: Application of AC Loss on HTS Magnet using Frequency Loss Induced Quench (FLIQ) Protection System.

A fundamental challenge with High Temperature Superconductors (HTS) is their high critical temperature (Tc) values and the stability that they impart when used in a magnet device with sufficient stored energy. Low normal propagation velocities and high stability of HTS wires cause localized damage due to an excessive peak hot spot temperature during a quench. Protection of HTS magnets for reliable operation has proven to be a challenge with the large amount of energy that is required to raise a significant fraction of the conductor above its local critical temperature which will dissipate the stored energy throughout the volume of the coil. Frequency Loss Induced Quench (FLIQ) system is a novel advancement of a relatively new technique that relies on AC losses to uniformly heat up a superconducting coil or sections of the coil to quench the coil accordingly. FLIQ drives an imbalance in the transport current between two or more sections of the magnet through a capacitor. To drive the imbalance, FLIQ uses an H-bridge design with Insulated Gate Bipolar Transistor (IGBT)s, whose gates are driven based on the current feedback control that allows the system to operate at resonance. This paper will discuss the application of FLIQ for HTS magnets and discuss recent data from experiments carried out on an insulated REBCO coil.

Speaker: Kikelomo Ijagbemi (National High Magnetic Field Laboratory)

Wed-Mo-Po3.12-13.pdf

Wed-Mo-Po3.13 - Motors X

Conveners: Hao Chen (China University of Mining & Technology), Qiuliang Wang (IEE CAS)

617 Wed-Mo-Po3.13-01 [109]: Comparative Study of Permanent Magnet Assisted Linear Switched Reluctance Motor and Linear Flux Switching Permanent Magnet Motor for Railway Transportation

Compared with conventional rotary machines, linear motors have no mechanical transmission device and, therefore, offer higher transmission efficiency, lower noise and easier to maintain. Hence, they have attracted a lot of attention in urban rail transit recently. Among them, linear induction motor (LIM) merits the advantages of simple structure, and has been applied in some countries. However, LIM suffers low efficiency and power factor, which is difficult to improve furtherly. Accordingly, more and more researches focus on the linear structures of other kinds of motors, such as linear flux switching permanent magnet (LFSPM) motor, linear switched reluctance (LSR) motor, etc. There are many similarities between the LFSPM motor and LSR motor such as similar primary iron and robust secondary. However, what is the difference between the electromagnetic characteristics and operation mechanism of the two motors in rail transit system? No quantitative comparison has been conducted between LFSPM motor and LSR motor in the identical volume until now. As we know, in contrast to LFSPM motor, no permanent magnet is a major obstacle of thrust improvement for LSR motor. On this basis, the magnetic circuits of the permanent magnets are introduced to LSR motor so that the magnetic saturation in primary poles is weaken. In this paper, a permanent magnet assisted linear switched reluctance (PMA-LSR) motor is proposed, investigated, and quantitatively compared with LFSPM for the urban railway transit system. First, the topology, operation principle, and electromagnetic performance of the LFSPM motor have been investigated and validated using finite element method (FEM). Then, the PMA-LSR motor for railway transit is designed and optimized. Finally, the electromagnetic performance of LFSPM and PMA-LSR motor have been compared and summarized through FEM in the following respects: working mechanism, thrust, thrust ripple, normal force, power factor, efficiency, magnetic field distributions, cost of materials, etc. The analysis results will provide design reference for the practical application and selection of two kinds of motors in urban rail transit traction system.

Speaker: Deyang Fan (Jiangsu University)

Comparative Study of Permanent Magnet Assisted Linear Switched Reluctance Motor and Linear Flux Switching Permanent Magnet Motor for Railway Transportation.pdf

Comparative Study of Permanent Magnet Assisted Linear Switched Reluctance Motor and Linear Flux Switching Permanent Magnet Motor for Railway Transportation.PPT

618 Wed-Mo-Po3.13-02 [110]: Modelling and Experimental Study on the Magnetization Losses of Tri-axial CORC Cable used in All-Electric Aircraft

A high temperature superconductor tri-axial CORC cable has been designed for all electrical aircraft. This paper is to study the magnetization loss of this tri-axial cable under time-varying external magnetic field. This cable is wound with ReBCO tapes from SuNAM, Korea. An experimental platform is built to measure the magnetization loss using an electrical method. The tri-axle cable is operated at 77 K in liquid nitrogen. Magnetization loss is studied under two situations: with transport current and without transport current. Under a same external field, the cable with transport current generates more magnetization loss than that without transport current. The influences of field amplitude and frequency on the magnetization loss are also studied in this paper. The magnetization loss increases dramatically with the field amplitude. A 3D finite element method (FEM) model based on T-A formulation is built to calculate the magnetization loss. The results from measurement show a good agreement with that from calculation. Then the distribution of the magnetization loss on different layers of the cable is analysed by modelling. Less magnetization loss happens on the inner layers of the tri-axle cable, due to the field shielding of the outer layers.

Speaker: Zixuan Zhu

619 Wed-Mo-Po3.13-03 [111]: Ferrite PM Optimization of SPM BLDC Motor for Oil-Pump Applications According to Magnetization Direction

This paper proposes optimizing the magnetization direction of isotropic ferrite permanent magnets (Fe-PM) to enable the maximization of back-electromotive force (B-EMF), torque density, and minimum torque ripple of surface permanent magnet brushless direct current motor. The concept design is divided into two steps. First, two general Fe-PM electric oil pump motor models with radial and parallel magnetization are selected and compared with the neodymium permanent magnet models. Secondly, a finite element method (FEM) analysis is carried out with two different magnetization directions for each of the models in open-circuit and load operation. For more accurate results, the effects of no-load B-EMF, magnetic field distribution, air-gap flux density, copper loss, and efficiency are investigated. Finally, the validity and superiority of the FEM design results are confirmed by manufacturing the prototype motor and performing an experiment.

Speakers: Hyunwoo Kim, Seungheon Lee

We_Mo_Po_13_03.pdf

620 Wed-Mo-Po3.13-04 [112]: A Study on Design of Hybrid Type Electromagnet for Maglev

Recently, as the demand for high-speed trains increases, studies on the stability of high-speed trains are actively under way. In the conventional case, most of the high-speed trains were driven by friction with the rails mounted on the rotating electric motor. In this case, unevenness and friction between the rail and the wheel caused the driving performance to drop, causing large vibration and noise in the carriage, resulting in instability. To improve this, Maglev is actively researched. Maglev is a system consisting of a levitation electromagnet and a linear motor. The levitation electromagnet is used to lift a bogie, and the linear motor is used to propel an injured bogie. This study is a study on the design of hybrid type permanent magnet type electromagnet. The levitation electromagnet is a structure that generates a guide force to prevent deviation from the outside in driving in addition to the levitation force for lifting the carriage. A typical electromagnet has two exciting electromagnet forms. In this case, the levitation force can be sufficiently generated according to the input current and the number of turns, but the guide force has a weak characteristic. In order to solve the problems of the existing model, this model proposed a three - axis type one - piece electromagnet. Since the electromagnet adopts one excitation structure, it is easy to manufacture, and it is possible to realize a robust Maglev system with the guide force improved through the three-spindle shape. In addition, detailed analysis of the iron loss in the levitation electromagnet was conducted through 3D-FEA analysis in the levitation electromagnet, and the durability of the system was verified through the demagnetization analysis of the permanent magnet. Finally, to verify the validity of this study, the fabrication and testing were carried out, and the test results and analysis results were compared and analyzed.

Speakers: Jae-Kwang Lee (hanyang university), Hyunwoo Kim

621 Wed-Mo-Po3.13-05 [113]: Study on The Novel Design Process of Working Bar of Double Cage Induction Motor

A policy that mandates the use of high-efficiency devices in order to use energy resources reasonably is being implemented. Induction motors are the most commonly used energy consuming equipment and are highly effective in high efficiency design. For the design of high efficient induction motor. satisfying the high starting torque, the double bar type bar type rotor was designed. In the case of the working Bar of the double cage bar, most of the cases use an experience constant. However, these cases are applied to high voltage and large capacity induction motors (over 100kW), In case of medium and low capacity induction motors, errors are generated, resulting in lower results than the actual efficiency. In this paper, a new design process for the rotor's working bar of a double cage induction motor for high efficiency induction motor design is proposed. First, set the target value of working bar current density(WBCD) and rotor teeth magnetic flux density(RTMFD), and then calculate the current and area of working bar through resistance. Using this, WBCD is calculated and experience constant are changed and recalculated until WBCD is converged to the target value. When the area of working bar is determined, the height is divided by 1/2, and the width of working bar for each height is parametrized. When the RTMFD converges to the target value, the efficiency is calculated by implementing the performance evaluation. If the target efficiency is not satisfied, WBCD and RTMFD is revised and recalculated until the target efficiency is satisfied. Based on a model of 15 kw-class induction motor, the finite element analysis(FEA) results of the design model using the existing experience constant and the proposed design process were compared. Finally, the validity of the process is verified by prototype performance test.

Speaker: Mr Dong-Ho Kim (Gachon University)

MT26_2019 Poster_dongho.pdf

622 Wed-Mo-Po3.13-06 [114]: Electromagnetic performance of HTS linear generator under Field-Cooled and Zero-Field-Cooled condition

The design of a cylindrical linear generator involves the calculation of the stator winding as a function of the magnetic field inside the solenoid, in such a way that the generation of the voltage obtained will be a function of the number of turns and the speed of the movement of the magnetic field inside. On the other hand, the use of HTS tapes in applications of linear electrical machines involves different aspects in their development such as: the configuration of the geometry, according to the anisotropic behavior of the material, depending on the incidence of the magnetic field on its surface; where another aspect to consider is the cooling method used to reach the superconducting state.
In the present work the comparative results of the electromagnetic evaluation of a linear generator constructed with tapes of BSCCO and YBCO are presented according to the cooling method; with absence of magnetic field (ZFC) and presence of the magnetic field (FC) incident on the winding. Where the voltage ​​generated are obtained as a function of the speed of the movement of the magnetic field and the cooling method used; as well as the force generated from the evaluation as a linear motor. The results obtained show a superior behavior in the generator built with YBCO repect to BSCCO.

Speaker: Dr Adrian Gonzalez-Parada (Universidad de Guanajuato)

623 Wed-Mo-Po3.13-07 [115]: Evaluation of Power Losses in High-temperature Superconducting Coils for Field-excited Electric Motors

High-temperature superconducting (HTS) machines received tremendous attention recently in the high power applications such as wind power generators and electric propulsion for ships, as they offer both high power density and high efficiency with the improving performance of HTS windings. In conventional HTS motors, HTS field windings are commonly constructed with HTS coils which supplied with DC current to produce the excitation field, so they are usually mounted on the rotors. Due to the complicated structure and high cost of the associated rotating seals located at the cooling Dewars, the application of rotor HTS windings are limited. Recently, a new kind of motor with static seal, whose HTS field-excitation coils and armature windings are both located at the stator, was proposed and received many attention. When the HTS field-excitation coils are located on the stator, the complicated cryogenic coupling device and high mechanical strength torque tube can both be eliminated, hence operational reliability be improved and reducing costs.
Traditional analytical methods can only be applied on models with simple superconductor (SC) geometry and unchanging field, e.g. circular SC. Other than circular SCs, there are many researches on rectangular SC. However, no analytical results can be obtained. Numerical methods such as finite element analysis (FEA) was used to simulate the partial differential equations. COMSOL Multiphysics will be used in this analysis, it works under the framework of FEA and could solve complex simulations accurately and quickly.
A cross-section model of a multi-stack rectangular SC coil will be created and investigated, while the AC losses when the coil was subjected to a transport current of 10 to 100%. Detailed design and construction of a race-track HTS winding, Dewar, analysis and evaluation of a multi-stack HTS tape will also be presented in full paper.

Speaker: Dr T. W. Ching (University of Hong Kong)

624 Wed-Mo-Po3.13-08 [116]: Analysis of Novel Wound Field Flux Linear Reversal Machine with Multiple MMF Working Harmonics

Due to the application limitation of permanent magnet and the ever-growing market requirement on linear motional equipment, the wound field linear machines are still drawing much attention. In this paper, a novel wound field flux reversal linear machine (WFFRLM) is proposed, which has both excitation windings and armature windings on a dual-side primary core, offering high thrust density and suitable for long-distance application. The pole shoes of the proposed WFFRLMs are specially designed with different pole pitches, introducing additional working magnetic motive force (MMF). As a result, the machine can operate on multi-MMF working harmonic mode, which means multiple orders of MMF are utilized, and by the flux modulation functioned by secondary iron poles, all the resultant working orders of air-gap flux density can contribute to the fundamental back electric motive force (back-EMF). Since the magnetic field strength is not enhanced but the MMF is better utilized, the proposed machine can accordingly enhance its electromagnetic performance, including the thrust force density and power factor. To clarify and verify the superiority of the proposed WFFRLM, the configuration of the proposed machine is firstly introduced and the analytical equations of the electrical excited MMF, air-gap flux density and back electromotive force (EMF) are derived and compared to that of the regular WFFRLM. Then the performance of the proposed machines with different excitation/armature pole pair combinations are analyzed to figure out the best one for the WFFRLM. Moreover, the influence of the key geometric parameters including slot opening ratio, different ratio of excitation pole pitch, size of secondary iron poles are investigated to achieve maximum thrust density and power factor. Finally, the well-optimized WFFRLM is modelled and compared with a conventional WFFRLM. The results show that the proposed WFFRLM can yield 18% higher back-EMF and 13% larger thrust force than the conventional one.

Speakers: Yi Cheng (Huazhong University of Science and Technology), Yuanzhi Zhang (Huazhong University of Science and Technology)

MT26_zhouyou_180x83.pdf

MT26_zhouyou_180x83.pptx

625 Wed-Mo-Po3.13-09 [117]: Design Optimization of 2G High-Tc Superconducting Magnet for High Speed Transportation

Motivated by growing needs for high speed transportation system, Korea Railroad Research Institute (KRRI) has developed the core technology of HTX (HyperTube eXpress) that operates vacuum tube above 1000 km/h. In order to achieve subsonic speed and dynamic stability, efficient propulsion and levitation systems are required, and consequently the subsonic capsule train has been developed by the linear synchronous motor and electrodynamic suspension based on superconducting magnet (SCM). Furthermore, detachable cryocooler system for the 2G high-Tc superconducting magnet (HTSM) enables to reduce the weight of the capsule train. However, the advantage of the 2G HTSM is accompanied by several problems including performance loss caused by increased operating temperature and relatively high wire price.

The purpose of this paper is to find effective 2G HTSM design for the subsonic capsule train. In the view of the cost and performance respectively, the wire volume and critical current can be improved by optimizing the coil shape of the 2G HTSM. While the 2G HTSM design is belong to non-linear optimization problem, non-linear critical current conditions which varies with the self-field direction are efficiently converted to simple linear constraint, and then the design problem is converted to a number of linear topology optimization problems. With many solutions for various constrains, most preferred SCM design is determined by considering its shape, cost, and performance. Also, one of the SCM design is fabricated to illustrate and evaluate the optimization result.

Speaker: Dr Jungyoul Lim (Korea Railroad Research Institute)

MT26-Wed-Mo-Po3.13-09 [117].pdf

626 Wed-Mo-Po3.13-10 [118]: Study on The Novel Rotor Core of Induction Motor with Cross Lamination

The induction motor(IM) is used in a variety of fields such as home appliances and factories, automobiles and railroad cars. Therefore, each motor has different target performance and the shape of the rotor is different. Use a cage rotor(CR) when the efficiency of the IM is important, and a double cage rotor(DCR) when starting torque is important. Starting torque and efficiency are in a trade-off relationship, which is affected by rotor resistance. Lowering the rotor resistance increases the efficiency and decreases the starting torque, which is reversed when the resistance increases. Since the rotor resistance is fixed to the rotor core shape, once the mold is made, the shape and performance of the rotor core are determined. Therefore, different types of rotor cores are required to make different types of IM, and many molds are required, which greatly increases the production cost. In this paper, a new rotor core feature of IM using cross-lamination is proposed. Make CR and DCR using dissimilar molds or counterpunch. The area of the starting bar in DCR is 1/4 of the bar in CR. Since the current flows to the starting bar during startup, the resistance of the DCR is about four times that of the CR. By 1:1 the resistance of the cross-lamination rotor core is approximately 2.5 times greater than that of the CR and approximately 0.375 times less than that of the DCR. When the resistance changes, the torque-slip curve changes depending on the proportional trend characteristic of the IM. By adjusting the stacking ratio, you can select the starting torque and efficiency by adjusting the rotor resistance with the least mold. Finally, the new rotor core features proposed based on 15kw grade IM are applied variously to verify the validity of their performance through finite element analysis(FEA).

Speaker: Mr Dong-Ho Kim (Gachon University)

627 Wed-Mo-Po3.13-11 [119]: Design of a High temperature superconducting linear synchronous motor for pulse power application

Linear synchronous motor is expected to be widely used in pulse power application, such as electromagnetic launch. A High Temperature Superconducting linear synchronous motor (HTS-LSM) for pulse power application is developed in this paper. A HTS winding is used as the moving coil, the stator coil is wound with copper winding. The superconducting winding has been excitation to flow DC current before a launch, which makes the current flows in the HTS winding in a closed-loop and remain constant DC during the launching. Thanks to both the zero resistance characteristics of superconducting and short-time emission characteristics of pulse power applications, a synchronous launch is achieved without a DC excitation applied on the moving coil. At the end of a launch process, the limited launch velocity is expected to reach the maximum point with the margin of the critical current of the HTS winding reducing to near zero. A small HTS-LSM prototype is designed in this paper. Both the synchronous launch mechanism of HTS-LSM and the electromagnetic characteristics of the superconducting winding are researched. The limit launch characteristic of the superconducting winding is also studied. Results show that the HTS-LSM has a higher utilization ratio of superconducting wires and a good emission efficiency.

Speaker: Shifeng Shen (Naval University of Engineering)

628 Wed-Mo-Po3.13-12 [120]: A Feasibility Study to Apply the Bitter Magnet to Electric Power Devices

The “Bitter” magnet has been serving high field science community over decades, since its first implementation by MIT in the 1930s and its variation of the Florida Bitter by the National High Magnetic Field Laboratory in the 1990s. With a proper water-cooling environment, average current density of such a bitter magnet reaches ~600 A/mm^2 with a field generation capacity of >40 T. This paper reports our initial efforts to apply the Bitter magnet to electric power applications with focus on: (1) air-cooled rotating machine such as axial-flux-type synchronous motor; and (2) oil-cooled stationary machine such as transformer. Due to the high-energy-density feature of the Bitter magnet, the new power machines may be substantially more compact than the conventional counterparts. Also, owing to the rigid structure of the Bitter windings, we expect lower vibration noise in operation of such machines. In spite of these benefits, mainly due to the requirement of high pressure coolant, the overall system’s efficiency must be carefully examined. As the first step of our research, this paper reports: (1) key concept of the Bitter magnet electric machine; (2) preliminary design of selected machines; and (3) performance estimation of the newly designed machines by use of finite element method.

Acknowledgement
This work was supported by the National Research Foundation of Korea as a part of Mid-Career Research Program (No. 2018R1A2B3009249).

Speaker: Mr Soobin An (SeoulNationalUniversity)

Wed-Mo-Po3.13-12_A Feasibility Study to Apply the Bitter Magnet to Electric Power Devices_SA_20190920.pdf

Wed-Mo-Or10 - Resistive Accelerator Magnets

Conveners: Kazuhiro Tanaka (KEK: High Energy Accelerator Research Organization), Ruediger Picker (TRIUMF)

629 Wed-Mo-Or10-01: Power test and magnetic measurement of the first short models of twin aperture magnets for FCC-ee

We report on the results of magnetic measurements, in particular, of the first short models of twin-aperture magnets for the CERN Future Circular Collider (FCC-ee) arcs. To date, we have built and tested three 1-m long bending magnets, using different materials for the ferromagnetic yoke and a 1-turn vs. multi-turn excitation. Besides the interest in checking the unusual I-layout, the focus is also on the behavior at low field, down to about 10 mT in the gap, and its impact on field quality (in particular, on the gradient term). In parallel, we have also worked on a 1-m long quadrupole model, with the aim of testing the peculiar twin configuration and assessing the multipole field errors as a function of the excitation current, checking especially the dipole and sextupole components. The results presented can be the basis of further developments for this kind of magnets.

Speaker: Carlo Petrone (CERN)

MT26-Wed-Mo-Or10-01__CPetrone_2019.pdf

MT26-Wed-Mo-Or10-01__CPetrone_2019.pptx

630 Wed-Mo-Or10-02: Performance of the Optimized Mechanical Design of the CLIC Main Beam Quadrupole Magnet Prototype

The Main Beam Quadrupole (MBQ) magnets of CLIC, the Compact Linear Collider under study at CERN Laboratory in Geneva, are part of a critical magnet family, considering the industrial production challenges. An R&D program on the MBQ magnets was launched for studying and investigating several assembly solutions in order to minimize the procurement cost of a large series of magnets comprising more than 4000 units. In this paper, the performance of the latest configuration is presented comparing the results of magnetic measurements with previous magnet model variants. Innovative solutions for an efficient and fast fiducialization and alignment of the MBQ quadrupoles were also studied and developed inside the PACMAN Project, a CERN project supported by the European Union via the 7th Framework Programme “Marie Curie actions”. The advantages of the mechanical design of the iron yoke and of the assembly and alignment procedures are presented and discussed.

Speaker: Michele Modena (CERN)

MT26_MMo_FINAL_slides.pdf

MT26_MMo_FINAL_slides.pptx

631 Wed-Mo-Or10-03: Comparative studies of three-dimensional analysis and measurement for establishing pulse electromagnet design

A new horizontal shift bump electromagnet for the J-PARC RCS injection bump system was designed and fabricated. The magnet is a pulse magnet that repeatedly excites a trapezoidal waveform of about 1.5 ms at 25 Hz. And it is possible to change of the rising and falling time of the pulse waveform with the maximum current of 16 kA and the voltage of 12 kV between 150 and 500 microseconds according to the optimum beam generation condition. In order to design the magnets of such specifications, three-dimensional dynamic magnetic field analysis capable of evaluating eddy currents is required. Using one electromagnet model, the difference between the static magnetic field analysis and the dynamic magnetic field analysis, and the difference between the two-dimensional and three-dimensional analysis were compared, respectively. In addition, we also verified the difference between the analysis result and the actual measurement result and so the difference of the magnetic field measurement method between the search coil and the hall probe and established a pulse electromagnet design method. The verification results by the fabricated electromagnet are presented here.

Speaker: Tomohiro Takayanagi (JAEA/J-PARC)

Wed-Mo-Or10-03_presentation.pdf

Wed-Mo-Or10-03_presentation.pptx

632 Wed-Mo-Or10-04: Combined-function magnetic measurement system

Production-quality magnetic measurements are required to characterize accelerator magnets for the Advanced Light Source Upgrade (ALS-U). Measurements of the magnetic axis, multipolar content and mechanical fiducialization are typically performed on three separate apparati. In this work, we describe the methodology and development of a combined-function, stretched-wire magnetic measurement system for high-throughput magnet characterization. For magnetic axis measurement, a vibrating wire apparatus is coupled with a hardware-in-the-loop optimization algorithm to automatically seek the magnetic axis given a starting search point. The same wire is then displaced on a circular trajectory in the magnet aperture, and the induced voltage is processed into the magnetic field harmonics. Finally, laser diodes are used to track displacements as the wire is probed around magnet pole tips for mechanical fiducialization. Measurement results are presented with a discussion on the methods and attainable level of automation in the combined-function magnetic measurement system for accelerator magnet characterization.

Speaker: Reed Teyber (Lawrence Berkeley National Laboratory)

Wed-Mo_Or10-04 Teyber.pdf

Wed-Mo_Or10-04 Teyber.pptx

633 Wed-Mo-Or10-05: TRIUMF new high resolution mass separator magnet design

TRIUMF is constructing a new facility, ARIEL, for rare isotope beam (RIB) production using the ISOL method. ARIEL will increase the production and enable the delivery of three simultaneous radioactive beams, making it the first multi-user RIB facility worldwide. The selection of such beams will be achieved by means of a new high resolution mass separator system, funded though the CANREB project. The separator is designed to achieve a resolving power of twenty thousand for a transmitted emittance of three micrometer. At the core of the system there are two identical 90 degree dipole magnets with a 1.2 meter radius of curvature, arranged in an optical configuration that minimizes aberration. The magnets are designed and manufactured with an integral field flatness in the order of one part in one hundred thousand to comply with the stringent optical requirements. Additional features are built into the magnet design to correct for high order aberration and guarantee linear behavior over a wide mass range. In this paper we will present the magnetic field study and the engineering considerations that lead to the final design of the dipole.

Speaker: Dr Marco Marchetto (TRIUMF)

Wed-Mo-Or10-05-Marchetto.pptx

634 Wed-Mo-Or10-06: Presentation withdrawn

Wed-Mo-Or11 - Magnetization and AC Losses in Conductors and Coils

Conveners: Eric Sun (Jefferson Lab), Dr Sebastian Hellman (Paul Scherrer Institut)

635 Wed-Mo-Or11-01 [Invited]: Magnetization, Flux Penetration, and Drift of YBCO Cable Segments Models and Measurements for Accelerator Magnet Applications

High temperature superconductors, such as YBCO, are being considered for high magnetic field magnets to be used in particle accelerators. A knowledge of the magnetic properties of these superconductors, and in particular the cables made from them are needed for accelerator magnet design. Here we present measurements of HTS CORC and Roebel cables using two devices. First, from a hall probe rig made to measure the magnetization of short sections of YBCO cable up to 4 cm x 1 cm. We performed measurements on stacks of YBCO tape, Roebel cable, and CORC cables at 4.2 K in this work, with field cycles up to 12 T. The second measurement was on longer segments of superconducting cables using a 3 T dipole AC susceptometer. The magnetization and penetration field of the cables was then compared to tape from which the cables were wound. Models for the magnetization of the cables, as well as direct measurements of them, were then then compared. The time decay (creep) of the magnetization was also measured for these cables. Simple models were then used to make estimates of field errors and field error drift (from creep), and the influence of field cycle was explored. Magnetization values on the order of 1000 kA/m were observed, with 20% change over 20 minute hold times. This could result for some magnets in errors in the hundreds of units.

Speaker: Prof. Mike Sumption (The Ohio State University)

636 Wed-Mo-Or11-02 [Invited]: Magnetic field measurements of stack of double-pancake coils wound with striated and copper-plated coated conductors

Striation is one of the approaches to reduce the shielding-current-induced fields (SCIFs) in magnets wound with coated conductors. We focus striated and copper-plated coated conductors, in which the current sharing between filaments through plated copper could improve their stability and could help their quench protection. It should be noted that the striation is effective to reduce SCIF only after the decay of coupling current which flows among filaments through plated copper.
We measured the magnetic field of stack of double-pancake coils wound with striated and copper-plated coated conductors in order to clarify the effect of striation to reduce SCIF. Four double-pancake coils were stacked, were installed in a cryostat, and were conduction-cooled by using a GM cryocooler. Each double-pancake coil was wound with 12.5 m-long conductor. The temperature of double-pancake coils was monitored and was controlled by using resistive heaters. We used a stable current supply, whose current stability is better than 10 ppm per hour, in order to examine the small field change caused by the decay of coupling current. At first, we ramped up the current to 50 A at 40 K, and the magnetic field was measured at the center of the stack of the double-pancake coils. The measured magnetic field was expanded with exponential terms with a couple of time constants. The determined time constants were compared with the decay time constant of coupling current, which was estimated from experiments using stacks of short samples of the striated coated conductor. One of the exponential terms, whose time constant was about 500 s, could represent the decay of coupling current flowing through the plated copper. The influence of the magnitude of current as well as the temperature, which could influence the resistivity of plated copper, will be studied at the second step of experiments. Furthermore, we plan the experiments using double-pancake coils with another conductor length.

This work was supported in part by the JSPS KAKENHI Grant Number 16H02326.

Speaker: Prof. Naoyuki Amemiya (Kyoto University)

637 Wed-Mo-Or11-03: Experimental results of field-error cancellation with HTS-based magnetic screens

Future circular accelerators for high-energy particle physics are expected to rely on increasingly higher magnetic fields for steering and focusing the particle beams. High temperature superconductors (HTS) are a promising technology for such future accelerator magnets. In particular, superconducting tapes based on rare-earth cuprate compounds (ReBCO) are potentially excellent candidates. Such tapes can withstand magnetic fields up to several tens of Tesla without losing their superconducting state, and achieve a critical temperature of about 90 K. Therefore, high thermal margins can be achieved by operating the tapes at 10 K and below.
While these outstanding magnetic and thermal properties make the use of HTS tapes a very interesting option, magnetic field control and quality are still a concern. Whenever an HTS based magnet operates in dynamic regime, for example during a current ramp, large eddy currents are induced in the superconducting tapes. These eddy currents typically show a decay time that is longer than the duty-cycle of the magnet. The magnetic field error induced by this undesired eddy currents could potentially prevent the use of HTS tapes in applications requiring a tight control over the field quality.
In order to improve the field quality in superconducting magnets, we propose to use dedicated magnetic screens based on the HTS technology. The screens are derived from the concept of persistent current shim coils [1]. To prove the potential of such screens, a dedicated experimental setup for transverse magnetic field configurations has been developed. In this contribution, we describe the setup, the proposed experiments and present the most relevant results in terms of magnetic field errors.

Acknowledgment: This work has been sponsored by the Wolfgang Gentner Programme of the German Federal Ministry of Education and Research (grant no. 05E15CHA), by the ‘Excellence Initiative’ of the German Federal and State Governments and by the Graduate School of Computational Engineering at Technische Universität Darmstadt.

[1] Van Nugteren, Jeroen. High temperature superconductor accelerator magnets. Diss. Twente U., Enschede, Enschede, 2016.

Speaker: Mr Lorenzo Bortot (CERN)

2019_09_MT26_Bortot_Wed-Mo-Or11-03.pdf

2019_09_MT26_Bortot_Wed-Mo-Or11-03.pptx

638 Wed-Mo-Or11-04: Magnetic vector potential-based formulations for modeling superconducting applications: a valid alternative to the H-formulation

In recent years, the H-formulation of Maxwell’s equation has become the de facto standard for simulating the time-dependent electromagnetic behavior of superconducting applications with commercial software. However, there are several situations where the H-formulation is not the most suitable tool. These include for example: i) situations where the superconductor is better described by the critical state than by a power-law resistivity; ii) HTS coated conductor coils with an excessively large number of turns; iii) electrical machines with materials with non-linear magnetic properties. In order to accurately and efficiently handle those situations, we discuss here two approaches based on the magnetic vector potential: the Campbell model and the T-A formulation. In this contribution, the Campbell model is for the first time implemented in the Comsol Multiphysics software package, without the need of resorting to external Matlab subroutines for the time-step algorithm. In addition, the T-A formulation is extended to 2-D conductors so that large coils with different coupling scenarios between the turns can be considered. Both models are first validated against experiments and simulation benchmarks, and then used to investigate cases of practical interest such as AC ripples in HTS coated conductors and AC losses of electrical machines with superconducting stator coils.

Speaker: Francesco Grilli (Karlsruhe Institute of Technology)

grilli_MT_2019.pdf

Wed-Mo-Or12 - Flux Pump and Cryostats

Conveners: Dr Timothy Coombs (University of Cambridge), Dr Zhenan Jiang (Victoria University of Wellington)

639 Wed-Mo-Or12-01: Investigation on the Ultra-high field Flux Pumped superconducting magnets

Flux pump field magnets have the ability to generate high fields through avoiding utilizing current expensive high-current power supplies and warm-to-cold current leads. The resultant effect is that the purchase and running costs of high-field magnets will decrease substantially. Thus it is realistic to expect HTS flux pumped magnets to be available which could be installed widely enabling a radical sea change in the use of high field magnets to support research.
Flux pump technology and the latest dynamic bridge switching method will be the key to providing the required high currents cost-effectively. Most previous studies have focused on the circuit of the flux pump system under ideal circumstance. However, in a real flux pumping system for high field magnets, the electrical components in the flux pumping system can be affected by each other. Negative impacts, such as the quenching of the dynamic bridge and inefficient control strategies, slow down the charging speed, and result in the saturation of the transformer iron core and even the failure of the whole flux pump system. This paper will investigate how to optimize the whole flux pumping system and coordinate the electrical components in the circuit to achieve the best performance. An effective and interesting solution based on second harmonic analysis is proposed to eliminate the negative impacts. Experimental results from a flux pump system will be presented to validate the methods described in the paper.

Speaker: Mr Chao Li (University of Cambridge)

Investigation on the Ultra-high field Flux Pumped superconducting magnets.pdf

Investigation on the Ultra-high field Flux Pumped superconducting magnets.ppt

640 Wed-Mo-Or12-02: HTS Switch for use in Flux Pumps

This report details the design of and results from a fast-switching, high power density HTS switch. The switch design initially used commercially available second generation HTS tapes, with later prototypes using thin films of YBCO on sapphire. The method used to switch into the off-state is through application of an AC magnetic field to the superconductor, causing any transport current to experience a dynamic resistance. The field also heats the superconductor causing the material to thermally quench but the recovery time back into the superconducting state can be very fast. Results show that second generation REBCO coated conductors can be used, but thin films of REBCO on thermally conducting, electrically insulating material such as sapphire have superior performance. Results showed that a 10mmx50mm, 300nm YBCO thin film on sapphire could provide an on-state IC of 90A and an off-state resistance of around 100mΩ. On-state to off-state transition time was less than 100µs and off-state to on-state transition time was less than 10ms. These results are promising for further development of a high power, fast-acting HTS power switching device for use in applications such as flux pumps or superconducting power converters. More broadly, switching thin films of HTS fast and controllably between superconducting and non-superconducting states is an interesting area of research which may yield further applications.

Speaker: James Gawith (University of Cambridge)

Wed-Mo-Or12-02.pdf

Wed-Mo-Or12-02.pptx

641 Wed-Mo-Or12-03: Design, construction and test of thermally activated ReBCO switches

Aiming to demonstrate the feasibility of a 10-kA class all-ReBCO based superconducting rectifier of the transformer-type, the development of high current ReBCO switches is crucial. A group of four switches in a bridge arrangement called switch-bridge has been developed. The switches are based on cyclic thermal heating of stacks of ReBCO tapes, operating in the 50 to 60 K temperature range when switched ‘on’ (no heating applied) and above 90 K when switched ‘off’. Thermal and electromagnetic models were generated for optimizing the total number of tapes and heating power required to turn ‘off’ 2 out of 4 switches of the selected bridge layout. For manufacturing this configuration of the switch, in total 36 SuperOx tapes of 12 mm width have been etched over an 8 mm-long central section using an ‘in-house’ etching method and recipe developed. Details of the etching process and key manufacturing steps are reported. The complete switch-bridge assembly, fully suitable and compliant for a rectifier circuit, has been tested in standalone mode in a liquid nitrogen bath. The test results including critical current of the switch gates, ‘off’-state resistance and switching time constants between ‘on’ and ‘off’ states are presented. The results are used to extrapolate the performance of the switch bridge towards the target operating conditions. With the results obtained, the proposed design of the switch is experimentally verified, and its application in combination with a transformer in a superconducting rectifier circuit is further discussed.

Speaker: Dr Nikolay Bykovskiy (CERN)

Switch_bridge_Bykovskiy.pdf

Switch_bridge_Bykovskiy.pptx

642 Wed-Mo-Or12-04: Self-Protecting HTS Current Lead - Demonstration of a new technology

A straight forward solution to reduce the heat load of Current Leads to superconducting magnets operating at 4 K is the use of high temperature superconductors (HTS) thereby eliminating the ohmic heating at the 50-77 K range. The heat input from the current leads is then determined by heat conduction in the HTS section only, leading to some factor 10 reduction in the heat load in comparison to fully normal conducting conventional leads. Modern HTS conductors demonstrate extremely high current density and further decrease of the current lead heat load is limited not by the material properties but by the requirement of robustness and reliable protection of the leads in the case of cryogenic failures in order to avoid lead burnout.
While accelerator magnets are designed for a fast dump at quench events within a fraction of a second, larger stored energy magnets like detector magnets may have discharge times of tens of seconds or even more. In this case the HTS part of the lead has to withstand the ohmic heating for a relatively long time and this requirement then determines the heat input at operation conditions. A new idea to reduce the heat load while keeping full reliability of the HTS leads is using an automatic thermo-mechanical switch that is thermally connected to, and electrically connected in parallel to the HTS lead section. In the case of a quench in the HTS lead section, by using the differential thermal expansion between materials, the switch turns on and the overheated section is bypassed by the high cross-section of the conductive part in the switch.
We wish to use this new technology for the first time for the BabyIAXO detector magnet.
In this paper the design and test of the first and unique Self-Protecting HTS Current Lead with a current rating of a few kA is presented.

Speaker: Alexey Dudarev (CERN)

20190918-Dudarev - MT26 Oral - Self-Protecting HTS Current Lead-ad_htk_ad.pdf

20190918-Dudarev - MT26 Oral - Self-Protecting HTS Current Lead-ad_htk_ad.pptx

643 Wed-Mo-Or12-05: Conceptual design of the cryostat for a highly radiation transparent 2 T superconducting detector solenoid for FCC-ee

The Future Circular Collider (FCC) electron-positron version may be the next step towards a next generation of particle colliders. It may include an Experiment for probing ee+ collisions using the IDEA (International Detector for Electron positron Accelerator), or similar, detector requiring a solenoid enclosing the inner tracking detector. An innovative 2 T superconducting solenoid with 4 m bore and 6 m long, has been accepted as baseline. Positioning the solenoid in between tracker and calorimeter requires an ultra-thin and highly radiation transparent cold mass. Likewise, a thin and radiation transparent cryostat is needed. The set value for the solenoid’s maximum radiation length is 1*X0.
The cryostat is designed as a sandwich of thin Aluminum alloy inner and outer shells eventually locally reinforced, for achieving vacuum tightness, and layers of innovative insulation material providing lowest thermal conductivity and sufficient mechanical resistance. Cryogel Z, a composite blanket of silica aerogel and reinforcing fibers, has a density of 160 kg/m3 and would allow a 250 mm cryostat thickness featuring a heat load of 400 W on the cold mass and 10 kW on the thermal shield. As an alternative, glass spheres (e.g. K1 type, manufactured by 3M, with a 65 μm diameter and a 125 kg/m3 density), or similar material, can be dispersed between the vacuum vessel thin-walls providing structural support.
Besides the cryostat conceptual design, we outline the setup developed at CERN to measure the thermal conductivity of the above-mentioned materials, present the test results and provide a design of the solenoid cooling system.

Speaker: Veronica Ilardi (Twente Technical University (NL))

MT26 Ilardi oral.pdf

644 Wed-Mo-Or12-06: Conceptual design of a conduction cooled superconducting undulator

In superconducting undulators (SCUs) that are currently operating at the Advanced Photon Source, the undulator magnets are indirectly cooled with liquid helium penetrating through channels in the magnet cores. The liquid helium is stored in a tank which is cooled by cryocoolers. However, a cryogen-free version of a superconducting undulator in which the undulator magnets are conduction-cooled, is also possible as it has been realized in the SCUs developed at ANKA in Karlsruhe Institute of Technology. We are currently working on a conceptual design of a conduction-cooled planar superconducting undulator. The measured load lines of cryocoolers and the measured thermal conductance of various thermal links are used in the thermal analysis. Also, various materials for the undulator magnet cores are being considered. This paper reports thermal design of conduction-cooled planar SCU.

Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357.

Speaker: Dr Shiroyanagi Yuko (Advacned Photon Source, Argonne National Laboratory)

Wed-Mo-Or12-06_talk.pdf

Wed-Mo-Or12-06_talk.pptx

12:45 Lunch (on your own)

14:00 Coffee Break (during Poster Sessions)

Wed-Af-Po3.14 - Structural Materials for Magnets

Conveners: Akira Yamamoto (KEK and CERN), Pablo Cayado (Karlsruhe Institute of Technology (KIT))

645 Wed-Af-Po3.14-01 [1]: The Study of Strengthening and the Electrical Resistivity of Deformation Processed Cu/Cu-16%Nb and Cu/Cu-7%Nb Microcomposites

The wide range of tensile strength values (1000-1700 MPa) simultaneously with the electrical conductivity of 55-75% of the international standard for annealed copper (IACS) are required for commercial Cu-Nb wires. For the industrial production, the optimal combination of physical properties must be supplemented with the reasonable cost. One of the ways to reduce the price of products can be the manufacture of wires with a reduced content of Nb. Mainly researches is devoted to the study of composites with a narrow range of Nb fracture (16-20%).
In the present study, we compare two composites with a standard niobium content Cu/Cu-16%Nb and with a lower one - Cu/Cu-7%Nb. The effects of deformation of these microcomposite wires on microstructure and physical properties are studied. The low Nb fraction allows to achieve the higher level of cold deformation up to 12 in comparison with 8,6 for Cu/Cu-16%Nb wire. The upper limit of tensile strength is 1200 MPa and 1500 MPa for Cu/Cu-7%Nb and Cu/Cu-16%Nb accordingly. The level of electrical resistance for maximum deformation is approximately the same for both wires. However, in the range of deformations far from the maximum, the combination of strength and conductivity is the same.
For both wires, a stepwise dependence of the electrical resistivity on the deformation is observed at a cryogenic temperature (10 K). This is speculated as an evidence for non-monotonic formation of the Cu/Nb interface.
These composites demonstrate a phase transition to the superconducting state and temperature of the phase transition decreases with increasing deformation. However, at extremely high deformations for the composite with reduced niobium content, an unexpected effect of increasing the critical temperature is found. The reasons for this behavior are discussed in relation to microstructure features of Cu/Cu-7%Nb wire.

Speaker: Victor Pantsyrny (Bochvqr Institute)

646 Wed-Af-Po3.14-02 [2]: Study of the fatigue behavior of unidirectional zylon/epoxy composite used in pulsed magnets

The fatigue behavior of the Zylon fiber reinforced epoxy matrix composite (Zylon/epoxy composite) has been tested under quasi-static tensile and tensile fatigue loads. The distribution of the fatigue life at different stress levels were determined. The results show that the statistical characteristic of the static strength and the fatigue life can be satisfactorily described by the normal, lognormal or Weibull distribution model. The measured S–N curve exhibits a pronounced nonlinear behavior with the stress levels in the studied life range. Strains of the unidirectional specimens were monitored by means of a mechanical extensometer during the fatigue loading. Three distinct stages of the strain evolutionary process can be identified. The evolution curves show a sharp increase in the first stage, an approximately linear slow increasing in the middle stage and an unstable acceleration in the third stage before failure. Similar to the strain evolution, the three-stage stiffness of degradation is also observed. The maximal cycle strain was chosen as the indicator for damage evaluation. The experimental data of the damage parameters were fitted with the existing analytical model and it is shown that the presented models have a good agreement with the tested results.

Speaker: Prof. Houxiu Xiao (Wuhan National High Magnetic Field Center)

2019MT26-poster2.pdf

647 Wed-Af-Po3.14-04 [3]: High strength and conductivity CuAg micro-composites by accumulative drawing and bundling process

High strength and conductivity CuAg micro-composites were fabricated via casting and accumulative bundling and drawing (ADB) process. CuAg with large cross-section exhibits competitive strength and conductivity properties for pulsed magnets use. The CuAg filaments and eutectic whiskers evolution during the compositing process was investigated. The tensile properties and thermal compression properties were analyzed. And the conductivity characteristics varied with the wire size were also investigated. And the mechanism for the mechanical properties was discussed. It is found that the whiskers refining is crucial for the increase of the strength. And the pure copper matrix added by bundling process will be beneficial to the electronic transporting.

Speaker: Ming Liang (Northwest Insititute for Non-ferrous Metal Research)

Wed-Af-Po3.pdf

648 Wed-Af-Po3.14-05 [4]: Examination and Assessment of Large Forged Structural Components for the Precompression Structure of the ITER Central Solenoid

Large structural forgings of complex shape are required for several components of the precompression structure of the ITER Central Solenoid, consisting of a stack of six electrically independent modules and featuring a total height of 18 m and a diameter of over 4 m. The precompression structure allows the vertical tensile loads to be reacted and adequate preload to be maintained, in order to insure the contact between the modules during plasma operation. Several components of the precompression structure such as tie plates, lower and upper key blocks, lower and upper components are machined from open die forgings of an unprecedented combination of complex shape and large size. The selected material is FXM-19, a high strength nitrogen bearing austenitic stainless steel particularly suited for application at temperatures as low as 4.5 K. A specific manufacturing schedule including redundant multidirectional forging is applied in order to achieve the required properties and microstructure of the final parts.

The paper summarises the lessons learned from the series production of the components. The achievement of a fine and homogeneous microstructure, which is of paramount importance for final inspectability of the parts and to obtain the mechanical properties, is particularly challenging taking into account their large size. It requires a perfect mastering of the whole manufacturing process, from the steelmaking route, based in some cases on sequential remelting of electrodes from different master heats to create large Electroslag Remelted (ESR) ingots, to the sequence of the thermomechanical steps, from the initial upsetting of the ingots to the final solution annealing of the as-forged parts.

Non-Destructive Examinations are based on stringent acceptance criteria. A fine microstructure is indispensable to allow full volumetric inspection with sufficient lateral resolution. The paper illustrates how inspectability of the full thickness of the parts by Ultrasonic Testing, compatible with the criteria imposed by the technical specification and the structural requirements of the single components, is only possible in absence of unrecrystallised areas or excessive grain growth.

Speaker: Stefano Sgobba (CERN)

Wed-Af-Po3.14-05_MT_26_SSg_et_al_.pdf

Wed-Af-Po3.15 - HTS Magnets and Conductors for Accelerators

Conveners: Dr Alexander Otto (Solid Material Solutions, LLC), Maria Baldini (FNAL)

649 Wed-Af-Po3.15-01 [5]: Ongoing Manufacturing of the EuCARD2 Roebel-based cos-theta magnet at CEA Saclay

In the framework of the FP7 EuCARD2 project, CEA Saclay developed a cos-theta insert magnet, wound with REBCO high temperature superconductor Roebel cable. Each dipole coil consists of a single arched layer of conductors, insulated with a glass fiber sleeve and impregnated with epoxy resin for mechanical reinforcement. Tooling has been developed to carefully guide the Roebel cable during the winding phase, transfer the coil to the impregnation mold and impregnate it. The magnet is made of two coils assembled around a Nitronic® 40 hollow core to mechanically limit its ovalization when operating in a 13 T background field. The structure is completed by the addition of an external stainless steel tube surrounding the coils. The paper details the validation of the whole fabrication procedure by using a stainless steel dummy Roebel cable and relates about the fabrication of the superconducting coils and the magnet assembly. The tests of the magnet in standalone configuration are foreseen for the end of this year in INFN-LASA test facility.

Speaker: Maria Durante

Wed-Af-Po3.15-01 [5].pdf

Wed-Af-Po3.15-01 [5].pptx

650 Wed-Af-Po3.15-02 [6]: Bending properties of quasi-isotropic strands made by 2G wires at 77 K

This paper numerically and experimentally studies the mechanical properties of quasi-isotropic strands under bending load at 77 K. Due to quasi-isotropic superconducting core fabricated by 2G wires existing in strand, bending on strand in different directions will lead to various critical current degradation, which will necessary meet during the winding of them into high current cable. Trough rotating the strand sample in tests, the dependence of bending radius on bending direction is obtained. A 3D mechanical model of quasi-isotropic strand built by ANASYS is used to analyze the bending behavior and estimate the measured results, with consideration of the slipping phenomenon of wires. In addition, similar quasi-isotropic strand but with annealing copper tube is also tested to explore the possible methods for improving the bending characteristics. Basing on the results from the work, high current Conduit-in Conductor cable (CICC) or Rutherford Cable made by the strand can be designed.

Speaker: Changtao Kan

651 Wed-Af-Po3.15-03 [7]: Quench Analysis of HTS quadrupole magnets for the IF Separator of IBS RISP Demonstrating Electromagnetic Quench Propagation

The Rare Isotope Science Project (RISP) of Institute for Basic Science (IBS) has been constructing a heavy ion accelerator complex, named Rare isotope Accelerator complex for ON-line experiments (RAON). To produce various high-intensity rare isotope beams, the RISP equips RAON with two rare isotope beam production systems: in-flight fragment (IF) separator; and isotope separator on-line system. The magnets placed in the forepart of the IF separator will be exposed to a high radiation dose of ~10 MGy/year. Considering the performance degradation and heating from high radiation, the RISP adopts high-temperature superconducting (HTS) magnets for the quadrupole magnets in the high radiation region. Each HTS quadrupole magnet consists of 8 series-connected metal-insulated single pancake coils. Because of the magnetic coupling, the quench of one or more HTS coils can induce the electromagnetic quench propagation to other coils. In this paper, we present probable quench scenarios and their electromagnetic and thermal transient behavior of HTS quadrupole magnets based on multi-coil circuit analysis.

Acknowledgement: This work was supported by the Rare Isotope Science Project of Institute for Basic Science funded by Ministry of Science and ICT and NRF of Korea (2013M7A1A1075764)

Speaker: Dr Jiho Lee (Institute for Basic Science)

652 Wed-Af-Po3.15-04 [8]: Design study and preliminary test results of a high field ReBCO coil with a new end structure

IHEP (The Institute of High Energy Physics, Chinese Academy of Sciences) is pursuing the pre-study of SPPC, a super Proton-Proton collider prorosed to be built in the future. To reach the 70 TeV or higher center of mass energy in proton collisions, dipole magnets with 12-T or higher bore field are required. A subscale magnet named LPF1 was fabricated and tested in 2018, which reached a main field of 10.2 T at 4.2 K with NbTi and Nb3Sn coils. In parallel with the continuous improvement of LTS (Low temperature superconductor) approach, the HTS (High temperature superconductor) coils are also under development to provide 1.5-3 T more field in LTS magnets. The conceptual design of a high field ReBCO insert coil with a new end structure has been completed. It will be fabricated and inserted into the LPF2: an improved magnet based on LPF1 and is expected to provide much higher dipole field than LPF1. To take advantage of the angular dependence of the critical current in the ReBCO tapes, an anti-angular arc is adopted at the coil ends to bend the tape with a larger radius and reduce the angle between the broad side of the tape and the magnetic field flux. The main design concept, fabrication process and test results of this ReBCO coil will be introduced.

Speaker: Ershuai Kong (IHEP&USTC)

MT26-posterkes0919.pdf

653 Wed-Af-Po3.15-05 [9]: Excitation and Magnetic Field Performances of a Prototype REBCO Sextupole Magnet at 4.2 K

A prototype REBa2Cu3Oy (REBCO) sextupole magnet was designed and fabricated for the chromaticity correction of an asymmetric–energy collider, named SuperKEKB. The REBCO sextupole magnet consists of six two-layer-rectangular coils, which are wound with a 4-mm-wide coated conductor and impregnated with epoxy resin. The inner bore radius and magnet length are 75 mm and 200 mm, respectively. The designed magnetic field strength is 200 T/m2 at a nominal current of 250 A and an operation temperature of 30 K. We conducted a series of experiments on the REBCO sextupole magnet after the fabrication. In this paper, we present the excitation and magnetic field results at 4.2 K.

Speaker: Xudong Wang (High Energy Accelerator Research Organization)

Wed-Af-Po3.15-05 poster.pdf

654 Wed-Af-Po3.15-06 [10]: Research and development of future radiation resistant accelerator magnets based on high temperature superconductors

A future accelerator facility to open up a new frontier will require a superconducting magnet with high radiation resistance. A construction plan of a second materials and life science experimental facility is proposed as one of the future plans of J-PARC. At the facility, superconducting solenoids are placed just behind the target to maximize the production of secondary particles. The absorbed dose of the superconducting magnet reaches 130 Gy in 10 years and the heating radiation is roughly estimated to be 650 W. In case of conventional NbTi based coils, it is difficult to keep the coil at superconducting temperature lower than 6.5 K due to heat load by the extremely high radiation. On the other hand, degradation of electrical insulation based on organic materials becomes conspicuous in this high radiation environment. Therefore, we have been performing research and development of mineral insulated superconducting magnets based on high temperature superconductors (HTS) to establish technology for a next generation radiation resistant superconducting magnet. In this contribution, results of applied research on ceramic coating and bonging technology to superconducting magnets, development status of the mineral insulated HTS coils, and results of irradiation test of HTS conductors and ceramic insulation samples will be presented.

Speaker: Masami Iio (High Energy Accelerator Research Organization (KEK))

MT26_Wed-Af-Po3.15-06 [10]_iio_H2.pdf

655 Wed-Af-Po3.15-07 [11]: HTS Quadrupole Magnet for the Persistent Current Mode Operation

The new high temperature superconducting (HTS) quadrupole magnet with circular coils was designed and built at Fermilab. There were investigated also several HTS coils at the liquid nitrogen temperature. The main goal of this activity is to investigate coils, and the magnet operation in a persistent current mode to reduce accelerator magnets capital and operational expenses. For that was used HTS persistent current switch and short-circuited coils. In the paper discussed magnet design, fabrication, and tests. There were measured magnetic field in the magnet aperture and the field decay when the magnet operates in the “frozen flux” mode. The test results are compared with simulations and confirmed advantages of the proposed approach.

Speaker: Vladimir Kashikhin (Fermilab)

MT26_HTS_Quadrupole_VK_092319a.docx

MT26_HTS_Quadrupole_VK_092319a.pdf

Poster_HTS_Quadrupole_091819a.pdf

656 Wed-Af-Po3.15-08 [12]: Applying Superconducting Magnet Technology for Klystron Beam Focusing and Energy Efficient RF Power Systems in Particle Accelerators

The energy efficient RF power generation system will be critically important for future energy frontier particle accelerators, such as CLIC, ILC, FCC, and CEPC. An option of the CLIC-380 (GeV) staging scenario will require ~ 5,000 X-bad (12 GHz) Klystrons with a total AC plug-power consumption of ~ 200 MW. it is so important to improve the energy efficiency. We focus on the Klystron beam focusing magnetic field presently with normal conducting solenoids consuming a half of the total power consumption. Applying superconducting magnet technology, we may expect a significant power saving, with an order of magnitude lower power for cryogenics operation. It will be more efficient to use higher temperature superconductor, such as MgB2 or higher temperature superconductor, to be operated at ~ 20 K or higher. This paper focuses on a prototype MgB2 superconducting solenoid magnet development successfully demonstrated with a central field of 0.9 T at 63 A, > 25 K, and will discuss feasibility of higher temperature superconductor application in future energy efficient RF power systems in future particle accelerators.

MT26-Wed-Af-Po3-15-08.pdf

657 Wed-Af-Po3.15-09 [13]: Effect of Screening Current Induced Field on Field Quality of an Air-Core HTS Quadruple Magnet

An air-core HTS quadruple magnet has many advantages by eliminating iron-core of an iron-core quadruple magnet. Study on air-core HTS quadruple magnet for accelerator application is currently ongoing at Applied Superconductivity Laboratory, Yonsei University. It is comprised of 8 metal-insulation double-pancake racetrack coils, each wound with 4 mm wide REBCO tapes. An REBCO tape is of high critical current, but magnetization current can flow in the tape due to its monofilament architecture. The magnetization current generates so called Screening Current Induced Field (SCIF). For an air-core HTS quadruple magnet, the SCIF could be critical for the field quality, such as gradient, uniformity, and effective length. In this paper, the current distribution in the REBCO tape of an air-core HTS quadruple magnet led to magnetization current is calculated, and the effect of the SCIF on field quality of the magnet is analyzed and discussed.

Speaker: Mr Geonwoo Baek (Yonsei University)

MT26_Poster_Wed-Af-Po3.15-09.pdf

658 Wed-Af-Po3.15-10 [14]: Experimental test of the Magnetic Field Active Shimming Method for the Air-core HTS Quadruple Magnet

A quadruple magnet, one of the superconducting magnets in accelerator system, is used to focusing accelerated beam particles. Recently developed high-temperature superconductor(HTS) has characteristics of high critical temperature and operating current densities under high-field region. Therefore, developments of HTS quadruple magnets applied to the hot cell region that has a high heat load in the accelerator system are being conducted. In addition, the study of air-core HTS quadruple magnet(AHQM) that is removed iron yoke are also under way. The magnet is suitable for the hot cell region and generate a higher magnetic field. Further, magnetic field characteristic of the magnet is linear according to the operating current. However, the magnetic field of the AHQM could be sensitively changed by the manufacturing error and assembly error because the iron yoke is removed. The magnetic field shimming method is used to compensate the magnetic field error after manufacturing the magnet. In the previous paper, we introduced the copper wire bunch active shim (CBAS) method which utilizes the free space that is generated by the removal of the iron yoke in the air-core HTS quadruple magnet. In this paper, the optimum design method and process for the CBAS method is presented. Furthermore, a test model of the CBAS method based on the design is constructed and its characteristics and applicability for the air-core quadruple magnet are analyzed.

Speaker: Mr Junseong Kim (Electrical and Electronic Engineering, Yonsei University)

659 Wed-Af-Po3.15-11 [15]: The Design of superconducting magnet for IF (In-flight Fragment) separator of RISP

The RAON of Rare Isotope Science Project (RISP) in Korea will provide not only rare isotope (RI) beams, but also stable heavy ions, ranging from protons to Uranium. Both of the In-flight Fragment (IF) separation and the isotope separation on-line (ISOL) will be used in RAON. Six HTS quadrupole magnets and One HTS sextupole magnet will be installed in the forepart of IF separator considering high radiation environment near the IF production target. HTS quadrupole magnets have an aperture radius of 120 ~ 170 mm and field gradient of 2.9 ~ 10.5 T/m. In the other part of IF separator, thirteen LTS quadrupole triplet magnets will be installed. LTS quadrupole triplet magnet has the field gradient of 11~11.7 T/m and effective lengths of 550, 900 mm. The HTS prototype quadrupole magnet and the LTS prototype quadrupole triplet was fabricated and tested. Both of protype magnets can be operated in the required field gradient stably, but they need some modifications such as yoke shape, coil specifications, etc. In this paper, the test results of prototype magnet are presented. Also, the modified designs based on test results are presented. All superconducting magnets for IF(In-flight Fragment) separator of RISP will be installed in 2021.

Acknowledgement : This work was supported by the Rare Isotope Science Project of Institute for Basic Science funded by Ministry of Science and ICT and NRF of Korea (2013M7A1A1075764)

Speaker: Sukjin Choi (IBS)

660 Wed-Af-Po3.15-12 [16]: Development of a 3-T conduction cooled MgB2 dipole magnet

A 3-T MgB$_2$ dipole magnet has been designed aiming at applications of compact accelerators and rotating gantries for heavy-ion radiotherapy facilities. The dipole magnet contains two identical racetrack coils. Each coil is wound by 156-m long commercial MgB$_2$ wire, with the length of the straight side, the winding diameter of the round portion and the height of 60 mm, 40 mm and 23 mm, respectively. The central magnetic field of the dipole magnet is designed to be 3.0 T at the operating current of 125 A at 20 K. For verifying the feasibility of manufacture techniques, three identical scaled MgB$_2$ racetrack coil was designed, manufactured and tested in advance. All coils were wound by 5.1-m long MgB$_2$ wire, the same type as in the full-scale dipole magnet, and heat treated at different temperatures from 650 $^{\circ}$C to 700 $^{\circ}$C. All coils were cooled by solid nitrogen and tested at 20 K. The temperature evolutions at current lead and coil body positions were monitored. Two coils heat treated at 650 $^{\circ}$C and 675 $^{\circ}$C remained stable when charged up to 250 A. The one heat treated at 700 $^{\circ}$C quenched at 225 A. It was proved that our manufacturing technique is reliable and can be used in the full-scale dipole magnet.

Speaker: Qihong Wu (Tsinghua University)

poster_MT_Kang.pdf

661 Wed-Af-Po3.15-13 [17]: Preliminary research on Soldered Stack ReBCO Cable

ReBCO is the second generation of high temperature superconducting (HTS) materials with potential for high-field applications and low mass quality applications. The fabrication process and performance of superconducting cables are a key issue for superconducting magnets operating at high-field or large sizes. This study describes a process of a soldered stacked conductor using a 4 mm wide ReBCO tape with copper stabilizing layer. The development of this kind of conductor is the preliminary research for more complicated cable modus, such as twisted stacked conductors and aluminum stabilized superconducting cables. The electrical and mechanical properties of the ReBCO soldered stacked conductor samples, including critical current, minimum bending radius, and axial maximum stress, were tested and analyzed. A simple multi-turned single-pancake coil using the above conductors was fabricated, tested, and compared to a similar coil using single ReBCO tape. In the future work, the development route of aluminum-stabilized superconducting cables for large-aperture magnet applications is stated.

Speakers: Mr Feipeng Ning (IHEP), Dr Xuyang Liu (IHEP)

cable poster.pdf

662 Wed-Af-Po3.15-14 [18]: New Application of Superconducting MgB2 Tubes for Passive Magnetic Field Shielding for Electron Ion Collider

Abstract— Electron Ion Collider (EIC) will be a next generation collider to address outstanding puzzles in modern nuclear physics, supported by both Brookhaven National Laboratory (BNL) and Jefferson Laboratory (JLab). The design of the interaction region (IR) requires a high field quadrupole for the heavier proton beams and an almost field free path (desired magnetic field within a few mT) for the electron beams. As the two beams passing close by each other, the magnet design in the interaction regions have great challenges due to tight space. Thus, a passive shielding is highly desired. Magnesium and Diboride (MgB2) - an intermediate temperature (39 K) superconductor which seems to be the most effective candidate for such a magnetic shielding. Thanks to its higher critical temperature, an MgB2 shield tube does not need the same level of helium cooling as NbTi and could conceivably be integrated with an intermediate temperature thermal shield and thereby save radial space. Owing to primary elements of magnesium and diboride, it’s much cheaper than high temperature superconductors Bi2Sr2Ca2Cu3O10+x(Bi-2223) or REBa2Cu3O7-x (where RE stands for rare-earth) in addition to low fabrication cost. MgB2 can be made in long tubes of various and complex shapes. We will develop superconducting magnetization model and perform shielding simulations at BNL. Critical current density of MgB2 at temperatures ranging from 4.2 K to 20 K will be considered to optimize tube diameters and thicknesses to effectively shield magnetic field of ~50 mT. Hyper-Tech will prototype and manufacture the MgB2 tubes based on the optimized parameters and magnetic shielding tests are expected to be performed at Ohio State University. We will report on the shielding design, fabrication and testing of the MgB2 tubes for the IR magnets for the future EIC collider.

Acknowledgement
This work was supported in part by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-FOA-0001940.

Speaker: Honghai Song (Brookhaven National Laboratory)

Wed-Af-Po3.16 - Magnets for Light Source

Conveners: Greg Brittles (Tokamak Energy), Piyush Joshi (Brookhaven National Laboratory)

663 Wed-Af-Po3.16-01 [19]: Control System for a Cryogenic Permanent Magnet Undulator at Taiwan Photon Source

A hybrid-type cryogenic permanent-magnet undulator (CPMU) with a 15-mm period length is being constructed for the TPS Phase-II beamline. A control system for CPMU called CU15 which is developed since 2018. The control system for CU15 is based on the Experimental Physics and Industrial Control System (EPICS) architecture and Ethernet Control Automation Technology (EtherCAT) framework. The main control components include the motor with encoder for gap adjustment, trimming power supply for corrector magnets, ion pumpers and BA gauges for vacuum system, resistance temperature detectors (RTD) for cryogenic environmental monitoring, and safety interlock for motion and cryogenic system. The design and implementation of CU15 control system will be summarized in this paper.

Speaker: Mr Chun-Yi Wu (NSRRC)

Wed-Af-Po3.16-01 [19].pdf

664 Wed-Af-Po3.16-02 [20]: Design and Development of a New Control Architecture for Elliptically Polarizing Undulator at Taiwan Photon Source

In the phase-II beamlines project of the Taiwan Photon Source (TPS), the insertion device (ID) of elliptically polarized undulator (EPU) called EPU66 and EPU168 will be installed in 2020. The new control system for EPU is based on the Experimental Physics and Industrial Control System (EPICS), and Ethernet Control Automation Technology (EtherCAT) framework. The EPU control elements include: motors with optical absolute encoders for gap and phase control, corrector magnets power supply control for trimming coil, interlock safety system for automatically stopped motion by using the encoders, limit switches, tilt sensors, and emergency buttons. All control functionality coordinate by the fan-less embedded computer with three Ethernet ports is developed. User interface for operators and beamline users are included to help them to operate the system, such as gap/phase control and on-the fly experimental. Reliable operation of the EPU is important to users of beamlines. The most unpredictable fault is due to a soft error in optical absolute encoders. There are several protection solutions to avoid faults, e.g. by increasing the distance of the encoder from the beam center, by a lead shield cover and finally by adopting an auxiliary position sensing device to cross check the position and perform the necessary procedure. Efforts to improve operational reliability of the EPU controls will be discussed. Features and benefits of EPU66 and EPU168 control system will be summarized in this report.

Speaker: Mr Chun-Yi Wu (NSRRC)

Wed-Af-Po3.16-02 [20].pdf

665 Wed-Af-Po3.16-03 [21]: Conceptual Design of a Superbend Magnet for Advance Light Source Upgrade Project

ALS-U is an ongoing upgrade of the Advance Light Source (ALS) at Lawrence Berkeley National Lab (LBL). The upgraded ring of the ALS will use a multibend-archomat (MBA) lattice, which will allow increasing the brightness of soft x-ray sources 100-1000 times with respect to current ALS capabilities. One of the goals of the project is maintaining ALS capability of producing hard x-ray beams, which are used for a macromolecular crystallography. The hard x-ray sources will be provided by replacing six gradient dipole magnets of the upgraded ring with superbend magnets generating a higher peak field at the source point. Two defocusing quadrupoles will be installed together with each superbend magnet in order to match the quadrupole field component from removed gradient dipole. Two alternative designs are being investigated. The first design is a warm-bore superconducting magnet. Its coils are made of an internally reinforced bronze-route Nb3Sn wire and a holmium pole is used as a flux concentrator. The second option is NdFeB permanent magnet system with build-in field clamps. Due to limited space in the accelerator lattice and the magnetic field requirements for the x-ray source points, both designs present challenges due to high magnetic forces acting on the manget components and due to impact of the magnet cross-talk on the beam trajectory.

Speakers: Charles Swenson (LBNL), Mariusz Juchno (LBNL)

MT26 - Conceptual Design of Superbend and Hardbend Magnets for ALS-U Project - POSTER.pdf

666 Wed-Af-Po3.16-04 [22]: The Cooling Design for the Magnetic Structure of the SHINE Superconducting Undulator

Abstract: Forty planar superconducting undulators (SCUs) with 4 m long magnetic structure will be used in Shanghai High Repetition rate XFEL and Extreme Light (SHINE). As the longest SCUs being developed in the world, they can produce the photons with energy of 10 keV – 25 keV. NbTi/Cu wire with the diameter of 0.6 mm and the ratio of Cu to NbTi 0.9 is adopted to fabricate the superconducting coils and the temperature of the coils must be below 5 K when the operating current is up to 400 A. The magnetic gap is no more than 5 mm in order to obtain the peak field of 1.58 T and it is impossible to design a beam vacuum chamber inside the gap. Instead, two copper foils parallel to each other are installed near the pole surfaces in the gap to shield the beam heat load. The special copper spacers are designed to cool the copper foils while four liquid Helium pipes are located symmetrically around the beam channel which is comprised of copper foils and spacers. The liquid Helium is provided by the cryogenic plant of the SHINE.

Speaker: Mr Qisheng Tang (University of Chinese Academy of Sciences)

Cooling Design for the Magnetic Structure of SHINE Superconducting Undulator v1.pdf

Cooling Design for the Magnetic Structure of SHINE Superconducting Undulator v1.ppt

667 Wed-Af-Po3.16-05 [23]: Development of a Nb3Sn superconducting undulator for the Advanced Photon Source

NbTi superconducting undulators (SCUs) are currently reliably operating at the Advanced Photon Source (APS) at Argonne National Laboratory (ANL). These devices significantly enhanced x-ray flux and brightness at high energy spectrum. As NbTi SCU technology is close to its full potential, further performance enhancement requires using different superconducting materials. Nb3Sn is a promising candidate to achieve that goal. Recently APS has started developing a Nb3Sn double undulator compatible with the APS storage ring. The magnetic length of each Nb3Sn undulator is about 1.4 m, totaling to 2.8 m. The completed device is planned to be installed in the APS storage ring. To develop the Nb3Sn SCU technology, a series of short SCU models has been fabricated and successfully tested. The SCU magnet design is being scaled up to an intermediate length of ~0.5 m. In the course of the short model magnet R&D, performance, quench behavior, mechanical and magnetic instabilities of the design have been experimentally evaluated and improved. The details of this work will be reported in this paper. In addition, on-going scaling-up efforts to intermediate lengths and relevant test results will also be presented and discussed.

Speaker: Dr Ibrahim Kesgin (Argonne National Laboratory)

668 Wed-Af-Po3.16-06 [24]: Numerical Design Optimisation of Short-Period HTS Staggered Array Undulators

Short period undulators are an essential component of compact free electron lasers (FEL) and medium energy storage rings for the production of hard X-rays. The use of ReBCO high temperature superconductors (HTS) in a staggered array undulator geometry is expected to yield a magnetic undulator field above 2T for a 10mm period and a 4mm magnetic gap, thus substantially increasing the performance of existing devices.
The optimisation of this design with FEM simulations and a critical analysis of its working principles are discussed. Specifically, the maximisation of the undulator field and the minimisation of the HTS material are the two main objectives of this study, which is performed with realistic material parameters - measured when applicable - of commercially available bulks and tapes. Finally, merits and drawbacks of different technical solutions and HTS materials are discussed and the intrinsic limits of this undulator geometry are highlighted.

Speaker: Dr Sebastian Hellmann (Paul Scherrer Institut)

2019_09_20_MT26_Hellmann_Poster_Q_Wed-Af-Po3.16-06_24_06_HQ.pdf

669 Wed-Af-Po3.16-07 [25]: Quench simulation of a REBCO undulator coil

Udulators are important insertion devices for synchrotron radiation light source such as storage ring and free electron laser facility. Comparing with undulators based on permanent magnet, superconducting undulators may maintain high magnetic fields with a shorter period length. Superconducting undulators based on NbTi coil were successfully developed and are now in operation. Recently, significant advances were achieved in research and development of REBCO (RE=rare earth, barium copper oxide) coated conductors (CCs). Due to its superior superconducting and mechanical properties, REBCO becomes promising candidate to further improve an undulators’ magnetic structure and simplify the cooling system. However, quench protection remains a critical issue of REBCO coil due to a very low normal zone propagation velocity (NZPV). In this paper, quench behavior of a REBCO undulator coil is investigated by numerical simulation based on finite element method. Numercial model of the undulator coil is built. Quench characteristics of minimum quench energy and NZPV are obtained. Quench protection methods such as subsection, diodes and quench heaters are simulated. Effect of different protection methods on hot-spot temperature are studied and compared.

Speaker: Dr Yi Ding

670 Wed-Af-Po3.16-08 [26]: Quench Protection of Insulated HTS Magnets by inducing a Current Surge within the Magnet

It is well understood that HTS conductors have low quench propagation velocities due to the high conductor specific heat with increased temperature. An HTS conductor with very little copper has a low value of the integral of j2dt between the magnet operating temperature and 300 K. Adding copper to an HTS conductor reduces the quench velocity within the coil and it makes the coil thicker, but it increases the integral of j2dt between the operating temperature and 300 K. The extra copper makes the quench harder to detect. A method that can work in some coil configurations such as thin solenoids, involves turning a large portion of the HTS coil conductor normal by putting a large current pulse into a thin coil via a center tap. This method has been used with success in a large high-current-density two-layer LTS magnet. This method is more effective if the coil has a well-coupled shorted secondary winding

Speaker: Dr Michael Green (Lawrence Berkeley Laboratory)

Wed-Aft-Po3.16-08 Poster copy.pdf

671 Wed-Af-Po3.16-10 [27]: Magnetic Field Optimization of an In-Vacuum Undulator at NSLS-II

A 3m long In-Vacuum Undulator (IVU) is employed at the National Synchrotron Light Source II (NSLS-II) for the Hard X-ray Nanoprobe (HXN) beamline providing structural and X-ray fluorescence imaging with world-leading spatial resolution. On July 1st 2018 a gearbox shaft in the gap drivetrain assembly sheared due to stress caused by mechanical misalignment. The device was extracted from the storage ring and measured. The magnetic field measurements detected a degradation of the magnetic performance as well as a demagnetization of the magnetic modules of the first 3 upstream periods. This paper describes the phase shimming optimization and the gap taper adjustments implemented to restore the spectral performance of the device.

Speaker: Dr Marco Musardo (Brookhaven National Laboratory)

Wed-Af-Po3.16-10[27].pdf

Wed-Af-Po3.16-10[27].ppt

672 Wed-Af-Po3.16-11 [28]: Field measurement of a cryogenic permanent magnet undulator at NSRRC

A PrFeB-based cryogenic permanent magnet undulator (CPMU) is under construction at the
Taiwan Photon Source (TPS) to provide high brilliant X-rays for phase II beamlines. The in-vacuum Hall probe measurement system is improved to measure and tune the magnetic field at cryogenic temperature. To ensure the measurement is taken in the magnetic field center, we also develop two methods: point-to-point and off-axis measurements. By tuning the differential adjuster, we can correct the magnetic field errors causing by re-assembly. This paper describes details of improvements in the measurement system, measurement result checking methods, and field tuning methods. Measurement results at cryogenic temperature are also presented.

Speaker: Dr Chinkang Yang (NSRRC)

MT26 poster-CK Yang.pdf

MT26 poster-CK Yang.pptx

673 Wed-Af-Po3.16-12 [29]: Magnetic and thermomechanical study of a variable gap superconducting undulator

A 3D thermo-magneto-mechanical study of a variable gap, 14 mm - 10 period superconducting undulator has been conducted based on a preliminary magnetic design carried out in RADIA. The choice of the conductor is made on the basis of a safe operating margin of the superconducting winding. This margin is determined via a coupled thermal, magnetic and mechanical analysis. Thus, the studies include the impact of the Lorentz forces and the heat input from the electron beam during energization and nominal operation of the undulator as well as the minimum pre-loading of the coils to achieve a tolerable peak stress on the conductor to achieve 1 T on axis at a variable gap ranging from 5 mm to 11 mm. To account for the thermo-mechanical effects on the winding, a refined study coupling thermal and mechanical models relying on contact elements has been implemented to get a more accurate response of the system under load. Those contacts elements model the contact between the coils and the carbon steel core making the two poles of the undulator.

Speaker: Dr Frederic Trillaud (Universidad Nacional Autónoma de México)

Wed-Af-Po3.17 - Mechanical Behavior II

Conveners: Hyung-Seop Shin (Andong National University), Victor Bykov (Max Planck Institute for Plasma Physics, Greifswald, Germany)

674 Wed-Af-Po3.17-02 [30]: Cyclic behavior of Wendelstein 7-X magnet system during first two phases of operation

Cyclic behavior of Wendelstein 7-X magnet system during first two phases of operation
V. Bykov, J. Zhu, A. Carls, B. Hein, K. Risse, P. van Eeten, H-S. Bosch,
L. Wegener and the W7-X Team

Max-Planck-Institut für Plasmaphysik, EURATOM Association
Teilinstitut Greifswald, Wendelsteinstr. 1, D-17491 Greifswald, Germany
The sophisticated large magnet system of Wendelstein 7-X (W7-X) stellarator has been operated during first two experimental campaigns at the Max-Planck-Institute for Plasma Physics in Greifswald, Germany, for roughly 13 months. Its 70 superconducting coils (NbTi CCIC) are extraordinary not only due to complex 3D shapes of 50 non-planar coils, but also due to a non-linear support system.
In addition, five big resistive coils with the aim to correct W7-X error fields are installed on the outer cryostat and use rubber pads in their supports to compensate thermal expansion of the coils.
The unique feature of the experimental device is the extended set of temperature and mechanical sensors to monitor the system behavior and to compare it with finite element predictions.
Several cooldown/warming up and thousands of electromagnetic cycles with different loading patents and with up to 70% design load magnitude have been performed by the system successfully.
The paper focus is on the structural cyclic behavior of the W7-X magnet system. Several related issues such as
bolts and rubber pads prestress degradation,
support slippage development,
evolution of mutual coil displacement,
loading path dependence of stress levels,
sliding weight support (cryoleg) adjustment,
and sensor failure
are addressed.
Lessons learned so far are also briefly summarized.

Speaker: Dr Victor Bykov (Max-Planck Institute for Plasmaphysics)

Poster_MT26_Bykov_final MT26-Wed-Af-Po3.17-02.pdf

675 Wed-Af-Po3.17-03 [31]: Mechanical design and analysis of the BabyIAXO magnet cold mass, cryostat and support system

According to the Primakoff effect, axions and axion-like particles can transform into photons in the presence of a strong magnetic field. To continue the search for these hypothetical particles, a new helioscope called the International Axions Observatory IAXO, and its subscale fully functional demonstrator BabyIAXO, are being designed.
To increase the sensitivity by a factor of a 100 compared to CAST, the experiment needs a stronger magnetic field and in a larger volume. The superconducting magnet of Baby-IAXO features two 10-m long flat racetrack coils, spaced by 0.8 m, operated in a quadrupole configuration and generating an average magnetic field of 2.9 T in the two 700 mm detection bores positioned between the coils.
The cold mass structure, using mainly Al5083, is designed to handle the pre-stress of the coils and the magnetic loads generated with current on. At ultimate current of 12 kA, the repelling force between the coils is 8 MN. Furthermore, the supporting structure has to keep the coils in position as they are in an unstable equilibrium in the plane parallel to the racetracks.
To support the cold mass in the cryostat, an arrangement of rods was chosen to minimize the cryogenic load. There are 4 vertical titanium rods taking the weight of the magnet; and another 4 of permaglas to keep the cold mass centered during cool down. In addition, there are 8 longitudinal permaglas rods whose main purpose is to allow the 25° tilting of the magnet while tracking the sun.
The total mass of the magnet is 22 t comprising a 15 t cold mass and 7 t cryostat. The magnet is installed on an elevated 360° rotating platform further constraining the cryostat design.
In this paper the mechanical design of cold mass, supporting system and cryostat of the BabyIAXO magnet are presented.

Speaker: Helder Filipe Pais Da Silva (CERN)

20190907-Silva - Poster MT26 - BabyIAXO-Mechanics-v6.pdf

676 Wed-Af-Po3.17-04 [32]: Mechanical design of the magnet mirror structure for testing Nb3Sn sextupole coil of 45 GHz ECRIS

The new Nb3Sn superconducting magnet system for the fourth-generation 45 GHz ECR source is under developing in the institute of Modern Physics(IMP). A mirror structure of the Nb3Sn sextupole testing coil based on a key and bladder technology is used for studying the coil's mechanical, thermal and quench performance under the realistic conditions. This paper describes the main components and the assembly procedures of the Mirror structure. Based on the three-dimensional finite-element mechanical model, the stress analysis for the process of assembly, cooling down, and charging is carried out. The assembly and strain measurement results of sextupole mirror structure are also introduced in this paper.

Speaker: Dr Wei Wu (Institute of Modern Physics,Chinese Academy of Sciences)

677 Wed-Af-Po3.17-05 [33]: Mechanical Design and Analysis of Capture Superconducting Magnet for EMuS

An Experimental Muon Sourse (EMuS) is proposed to construct at the facility of China Spallation Neutron Source (CSNS) by IHEP (Beijing, China), for the R&D of key technologies of the next-generation neutrino beam facility. The capture superconducting solenoid magnet is one of the key components of the EMuS. It consists of 4 coils which are an axially graded solenoids with a peak central field of 5-T at 3944 A of nominal current. The capture magnet has an iron yoke for flux return and field shield. This paper presents the mechanical design and analysis of the capture magnet.

Speaker: Mr Zhilong Hou (The State Key Laboratory of Particle Detection and Electronics, Institute of High Energy Physics (IHEP) Chinese Academy of Sciences（CAS）, University of Chinese Academy of Sciences)

Poster-mt26 - Houzl.pdf

678 Wed-Af-Po3.17-06 [34]: The Mechanical Analysis of the Rutherford Cable Subjected to Axial Tension

The energy upgrade of the Large Hadron Collider (HE-LHC) and the Future Circular Collider (FCC) demand new requirements that the magnetic field of accelerate magnets should be up to 16 T. The Nb3Sn Rutherford cable is used for magnet design. Due to the complex geometry and working conditions of the magnets, Rutherford cables have to suffer complex stress condition. To better understand the stress distribution and the deformation in the Rutherford cables when subject to loads, a three-dimensional model is built to analyze its mechanical behaviors. Firstly, the method to generate the geometric model of Rutherford cable is described. Then the mechanical behaviors of the Rutherford cable are analyzed when it is subjected to axial tension. The influence of friction coefficients and strand damage are considered. This analysis may help us to understand the role of friction coefficients and strand damage when the Rutherford cable is under tension condition.

Speaker: Ms Libin Jiang (Lanzhou University)

presentation.pdf

679 Wed-Af-Po3.17-07 [35]: High definition 3D finite element analysis of low temperature Rutherford cable

A multi-scale mechanical model of Rutherford type, low temperature superconducting cable is discussed in this paper.
The homogenization of the mechanical properties of the superconducting bundle is explained, at room and cryogenic temperature. The inclusion of a high definition three-dimensional sub-modelling of the strand geometry is illustrated, up to the superconducting filaments scale. The geometrical reconstruction of impregnated stacks is presented using a simplified bi-metallic description.
This finite element model is confronted with experimental results performed on stacks of conductors, with a view in estimating the cable current transport capability thanks to existing scaling laws.

Speaker: Pierre Manil (Université Paris-Saclay (FR))

Poster MT26 - CoCaSCOPE - v1.pdf

References.pdf

680 Wed-Af-Po3.17-08 [36]: Mechanical behaviour of the HL-LHC beam screen during a quench test campaign of the MQXF short model magnet

In the framework of the High-Luminosity Large Hadron Collider (HL-LHC) project, a complex assembly, known as the beam screen, will be installed by 2024 in the aperture of the new Nb3Sn HL-LHC triplet magnets (MQXF) nearby the ATLAS and CMS experiments. The beam screen is an octagonally shaped pipe that ensures that the vacuum conditions, required for the stability of the beam, are met. It also shields via tungsten-based inserts the 1.9 K magnet cryogenic system from the heat loads and damage to the magnet coils that would otherwise be induced by the highly penetrating collision debris.
The mechanical behaviour of the beam screen during a magnet quench needs to be carefully studied. The distribution of Lorentz forces induced in the assembly is closely related to the magnet protection system, which is composed by conventional quench heaters and the Coupling-Loss Induced Quench (CLIQ) system.
To this purpose an innovative coupled multiphysics model has been developed as a tool to support the design of the beam screen. The model combines the magnetic, thermal and mechanical equations in a dynamic way.
A dedicated test campaign has been conducted at the CERN’s magnet test station to assess the effects of magnet quenches on the beam screen inserted in an MQXF short model magnet. The beam screen assembly has been instrumented with strain gauges, special probes and optical fibres.
This paper presents the measurements on the beam screen and a comparison with simulations.

Speaker: Mr Marco Morrone (CERN)

Poster_Marco_Morrone_MT26.pdf

681 Wed-Af-Po3.17-09 [37]: Analysis of the mechanical behavior of the KSTAR CS magnet during long pulse plasma discharges

The KSTAR central solenoid (CS) is a vertical stack of four pairs of coils compressed axially by preloading structures. The axial compression on the CS coils is monitored by measurements of strain and displacement, which are important monitoring parameters for safe operation of KSTAR. The equivalent vertical force methodology of a simplified multi-spring system was developed to analyze the preload and displacement variations of the CS magnet. The equivalent vertical force is based on the poloidal field (PF) coils and plasma currents during plasma discharge. The estimated vertical displacements by the developed method were reasonably well in agreement with the displacement measured during long pulse discharges in 2017 (#18437) and 2018 (#21735) campaigns. The analyzed displacement can be used to quickly calculate the preload reduction of the CS magnet structure. This approach contributes to the development of advanced operation scenarios for long pulse and large plasma current discharges with safety margin. During plasma discharge, this algorithm can be applied to a real-time plasma control system.

Speaker: Hee-Jae Ahn (NFRI)

Poster_MT26-Wed-Af-Po3.17-09_hjahn.pdf

Wed-Af-Po3.18 - REBCO Wires & Cables III

Conveners: Chris Kovacs (The Ohio State University), Dr Ibrahim Kesgin (Argonne National Laboratory)

682 Wed-Af-Po3.18-01 [38]: Development of High Je 2G HTS Wires for High-Field Magnet Applications

Recently, deposition of REBCO layer on thinner C276 Hastelloy substrate for the second generation high temperature superconductors (2G HTS) wires have attracted more attentions. The main advantages are i) to effectively increase the critical engineering current (Je) without additional efforts on enhancement of current carrying capacity in the superconducting layer, ii) to improve the electricomechanical properties such as critical bending diameters. Shanghai Superconductor Technology Co., Ltd. (SST) as an emerging 2G-HTS manufacturer is aiming to contribute significantly to the wire availability on the market. In this work, we described the deposition processes and characterization of 2G HTS wires using 30 micrometer thick C276 Hastelloy substrate at SST. After optimization of the whole processes, 4 mm wide tapes (60 micrometer thick in total, with 15 micrometer thick Cu-stabilizer at each side) are obtained. Current carrying capacity of the REBCO layer (with intrinsic pinning centres optimized for magnet applications) is comparable to that made on 50 micrometer thick substrate typically used in our process. And Je values of the tape are over 700 A/mm2 at 77 K, self-field and 2.3 kA/mm2 at 4.2 K, 10 T, respectively. Electricomechanical tests on the 4 mm wide tapes at liquid nitrogen condition show that the Ic retention is over 90% when applying tensile stress of 700 MPa, while no significant Ic degradation is discerned at bending diameter of 2 mm. This work demonstrates the high potential of using such high Je 2G HTS wires for high- field magnet and high-current conductor applications.

Speaker: Yue Zhao (shanghai jiao tong university)

683 Wed-Af-Po3.18-02 [39]: Effect of Core Materials on the Electrical Properties of Superconducting Conductor on Round Core Cable

High temperature superconducting (HTS) conductor on round core (CORC) cable is considered as a potential technology for power applications, because of its high current-carrying capacity, compactness, and strong mechanical properties. As the main component of CORC cable, the center core is used to support the HTS conductors. However, for metal center core, the eddy current induced in the core under alternating electromagnetic field is unneglectable, which will lead to extra AC loss in power applications. This paper focuses on the selection of center core of CORC cable. AC loss of CORC cable using different center core is evaluated by both numerical and experimental methods, in which copper, aluminum, nickel, stainless steel and fiberglass epoxy (G10) have been chosen as the core. Results illustrate that AC loss of CORC cable has a correspondingly decrease with the resistivity of the core material, and this effect also relies on the shielding effect of the outer HTS conductors. Besides, CORC cable with core of nickel shows a quite different AC performance due to its ferromagnetic characteristics. Conclusions obtained from this paper will provide essential data for the future optimization on the design of CORC cable.

Key words: High temperature superconductor, Conductor on round core, Magnetization loss, Transportation loss, Shielding effect

Speaker: Haosheng Ye (Shanghai Jiao Tong University)

Wed-Af-Po3.18-02.pdf

684 Wed-Af-Po3.18-04 [40]: Electromagnetic properties of REBCO coated conductor with multi-superconducting layers

The enhancement of engineering current density, Je is one of important issues in conductors for high performance superconducting magnets. In order to obtain the higher Je of high temperature superconducting (HTS) REBCO conductor, we adopted the laminate structure consisting of three REBCO superconducting layers on one common IBAD processed substrate. In this study, we have fabricated various conductor samples with three HTS layers by using two types of REBCO tapes supplied from different companies, where one was HTS layer with artificial pinning centers, L_REBCO (APC) and the other was that without APC, L_REBCO. We evaluated in-field critical current density, Jc property of 3-HTS layered REBCO conductor samples in the magnetic field range of 0 to 6 T. And also investigated the influence of REBCO layer with APC on the improvement of in-field Jc property for samples with four different layer structures of L_REBCO(APC)/L_REBCO/L_REBCO(APC), L_REBCO(APC)/L_REBCO/L_REBCO, L_REBCO/L_REBCO/L_REBCO and L_REBC(APC)/L_REBC(APC)/L_REBC(APC). Detailed results will be presented in the conference.

Speaker: Dr Sang-Soo Oh (Korea Electrotechnology Research Institute)

MT26_ssoh.pdf

685 Wed-Af-Po3.18-05 [41]: Current distribution of an HTS twisted stacked-tape cable conductor investigated by self-field measurements

Various large current-carrying conductors composed of REBCO tapes have been proposed in recent years for high current applications such as magnets and power transmissions. As one of the conductors, a twisted stacked-tape cable (TSTC) is being developed at the Massachusetts Institute of Technology. The TSTC conductor is composed of stacked REBCO tapes which are twisted along the longitudinal direction of the stacked tapes. The stacked REBCO tapes are immersed with a solder, and are imbedded in a copper former. Therefore, current transfer between REBCO tapes occurs easily when applying current in the TSTC conductor. In this study, self-field distribution measurements of the TSTC sample were conducted along the conductor in order to investigate current distribution in the conductor. A 650 mm diameter single turn coil of a 48 tape TSTC conductor made with 6 mm width SuperOx REBCO tapes was developed. The self-field measurement experiments with the sample were conducted in the test facility of the National Institute for Fusion Science. The current distribution in the TSTC conductor will be discussed by using a line current model with the measured self-fields.

Speaker: Dr Tetsuhiro Obana (NIFS)

MT26@TSTC@19-9-20.pdf

686 Wed-Af-Po3.18-06 [42]: Improvement of Jc properties for Hf and La doped Gd123 films fabricated by fluorine-free MOD method

We have fabricated Hf and La doped FF-MOD GdBa2Cu3Oy (Gd123) thin films on LaAlO3 substrates and investigated their flux pinning properties. Temperature dependence of Jc in magnetic fields parallel to the c-axis orientation up to 7 T was estimated from the width of the magnetization curves using the modified critical state model. Critical temperature for Gd123 thin films indicated around 92 K, and Tc varied little by Hf and La doping. Hf 10 mol% doped film achieved high critical current densities of 2.72 MA cm-2 at 77.3 K under 0 T, and 0.27 MA cm-2 at 77.3 K under 1 T. With increasing Hf doping amount, Fp gradually increased, and the peak of Fp shifted to the high magnetic field side. The elementary pinning force and the effective pinning center density also increased. The number of effective pins increases until Hf 2 mol%, and then it decreases a little. Especially Hf 2 mol% film obtained the maximum value of 49.8 μm-2 at 4.2 K, which is 2 times larger than that for non-doped film. We believe that BaHfO3 are introduced into FF-MOD Gd123 thin films by Hf doping. Furthermore, Gd123 thin films with La addition showed the increase of Jc at self-magnetic fields and the decrease in number of density of holes on the film surface. La 1 mol% and Hf 2 mol% co-doped film achieved high critical current densities of 3.10 MA cm-2 at 77.3 K under 0 T, and 0.32 MA cm-2 at 77.3 K under 1 T. It confirmed that the effective APCs were introduced by Hf doping to improve Fp in magnetic fields and promoting crystallization of Gd123 by La doping brought about the increase of Jc in low fields.

Speaker: Joichiro Fukui (Electrical and Electronic Engineering, Tokyo Metropolitan University, Japan)

Wed-Af-Po3.18-06 [42].pdf

687 Wed-Af-Po3.18-07 [43]: The study of pinning center formation in Sm1Ba2Cu3O7-d coated conductor by reactive-co evaporation method

We investigated the pinning centers formation in Sm1Ba2Cu3O7-d(SmBCO) coated conductor by reactive co evaporation method. The SmBCO film was deposited on the IBAD-MgO template with the structure of SmBCO/LMO/MgO/Y2O3/Al2O3/Hastelloy using EDDC (Evaporation Using Drum in Dual Chambers) process. We investigated the phase formations as pinning centers with the change of composition ratio of Sm:Ba:Cu. We found out that several phases were observed in the SmBCO matrix such as Sm2O3 and Sm/Ba anti-site when compositional ratio of Sm:Ba:Cu=1+x:2:3, which was confirmed by TEM analysis, and good superconducting properties under high magnetic field could be achieved by virtue of those pinning centers. We also investigated the effect of deposition process parameters such as deposition rate and temperature on the pinning centers formations. As the deposition rate of SmBCO was increased, point shaped pinning centers were dominant, on the other hand, as it was decreased, rod shaped pinning centers were dominant. As substrate temperature was increased, rod shaped pinning centers were dominant, on the other hand, as it was decreased, particle shaped pinning centers were dominant. We could fabricate high performance of SmBCO superconducting coated conductor under high magnetic field with effective pinning centers.

Speaker: Dr Ho-Sup Kim (Korea Electrotechnology Research Institute)

MT26-Wed-Af-Po3.18-07.pdf

688 Wed-Af-Po3.18-08 [44]: Experimental research on critical current behavior of various HTS tapes

In practical applications, the critical current of high temperature superconducting (HTS) tapes is usually influenced by many factors, such as magnetic field, stress and strain, etc. In order to design HTS devices accurately, it is vital to study the critical current behavior of HTS tapes under different conditions. In this work, a series experiments have been performed to study the critical current characteristics of several typical HTS tapes at 77 K. The experimental results and analysis have been introduced in details, including the dependence of critical current of the HTS tapes on external magnetic fields, applied tensile strain and bending stresses, as well as the current recovery characteristics after the withdrawal of the mechanical stress.

Speaker: Prof. Li Ren (Huazhong University of Science and Technology)

Experimental research on critical current behavior of commercial HTS tapes.pdf

689 Wed-Af-Po3.18-09 [45]: Presentation withdrawn

690 Wed-Af-Po3.18-10 [46]: Insulation Design for 10kV Three-phase Concentric High-Temperature Superconducting Cable

This paper introduced a insulation design for a 10kV three-phase concentric high temperature superconducting cables by cold dielectric method. Insulation properties of the PPLP (Polypropylene laminated paper) and its dielectric strengths un-der AC voltage endurance test and the lighting test in liquid ni-trogen have been studied. According to test results and the standard for 10kV paper insulation cable, The main insulation and the stress cone for the 10kV three-phase concentric high temperature superconducting cables have been designed. The voltage endurance test under power frequency and the lighting impulse test have been carried out, indicating that the cable is complied with the requirements after the verification of the test.

Speaker: Dr Wei Pi (North China Electric Power University)

Wed-Af-Po3.18-10[46]-poster.ppt

Wed-Af-Po3.19 - REBCO Wires & Cables IV

Conveners: Anbo Wu (GE Global Research), Drew Hazelton (SuperPower Inc.)

691 Wed-Af-Po3.19-01 [47]: The impact of stacked angle on the uniformity of trapped field in HTS taped stacks

Uniform magnetic field was mainly produced by electromagnetic coils in most engineering applications. However, with the development of superconducting technology, the demand for bulk magnets with uniform magnetic field has increased accordingly. In this paper, the key factors affecting the magnetic field uniformity of bulk magnets have been studied experimentally by magnetizing HTS taped stacks with different stacking angles under liquid nitrogen temperature zone. A trapped field with higher uniformity in the taped stack has been obtained by optimizing the stacking angle of HTS tapes. By using E-J power law joint with T-A formulation to establish a two-dimensional axisymmetric simulation model in a commercial software, the distribution of trapped magnetic field lines in the angled tape stack has been achieved and the induced current density in the taped stacks has been analyzed as well. Results show that the strong nonlinearity of the induced current distribution in the HTS tapes is the main factor affecting the uniformity of the trapped field. The magnetization angle does not affect the uniformity of the trapped field, but it is the important factor that affects the strength of the trapped field.

Speakers: Xiaodong Li (Beihang University), Wenjiang Yang (China)

692 Wed-Af-Po3.19-02 [48]: Performance Test of a Geometrically Symmetrical Strand Fabricated by 2G Wires at 4.2 K

Because of the well mechanical property and high current capability, geometrically symmetrical strands made from second generation (2G) wires are promising for large scale high-field magnets typically operated at 4.2 K. This paper performs the first tests of a geometrically symmetrical strand in liquid helium and magnetic field of up to 6 T. The critical current and its anisotropy under background direct current (dc) magnetic field are measured and compared with the estimated value from single tape data. The impacts of transverse Lorentz forces on the current carrying capability of the strand is characterized by the repeatedly cycled magnetic background field. To lower the total resistance of whole circuit, three stacking methods of wires on strand terminations are measured and contrasted at 77 K. The testing results have great significance for using high-temperature superconducting (HTS) geometrically symmetrical strand in high-field magnet applications.

Speaker: Changtao Kan

693 Wed-Af-Po3.19-03 [49]: The Contact Mechanical Behaviors in Triad CORC Wires

The CORC wires is one of the most ideal structures and will be used in the next generation controllable nuclear fusion magnets due to the advantages of cheap cooling costs, high transport performance and especially simple manufacturing process. In recent years, the cabling process of CORC has been studied in detail by scholars. However, the superconducting magnet in the fusion reactor is made by further twisting, winding and transverse compressing the multiple CORC. Therefore, the CORC wires will be deformed by stretching, bending, torsion and transverse compressing in the above process, these deformations can affect the degradation of the magnet. D C van der Laan et al. conducted several experiments for the critical current degradation of the CORC wires under transverse force, and the conclusion that the tape gaps and the thickness of the copper layers are important factors affecting the transport capacity was given. This work aims at building a model that simulates the mutual twisting process of multiple CORC wires and the final winding process of the magnets via the commercial software ABAQUS. The superconducting tapes of different specifications and the CORC wires made by different winding methods are considered in the triad forming process. The distribution of stress and strain of the superconducting tape of each CORC wires is calculated and displayed, and then the degradation of the critical current is calculated by the scaling law. The obtained numerical results are verified by experiments. Finally, the optimal cabling scheme for the multiple CORC wires was obtained.

Speaker: Mr Keyang Wang (Lanzhou University)

mt26-wky.pdf

mt26-wky.pptx

694 Wed-Af-Po3.19-05 [50]: Numerical study on the coupling current and magnetization loss of striated CORC cables using 3D T-A formulation

Striation is proved to be effective in the magnetization loss reduction for Conductor on Round Core cable. Though it was experimentally observed that the coupling loss contributed to the total magnetization loss of striated CORC cables, simulation models and detailed analysis of the coupling current were still missing. In this study, we present numerical models of striated CORC cables considering the inter-filament coupling by using 3D $\textit{T}$-$\textit{A}$ formulation implemented with commercial software. To confirm the validity of our models, two sets of 4-filament REBCO tapes were prepared by laser cutting and coupled by electroplated copper and tin respectively to generate different inter-filament resistance. The magnetization loss in the frequency range of 10 Hz to 150 Hz were measured and compared against numerical results. Corresponding models of CORC cables with striated strands and inter-filament resistance were developed, where the magnetization loss behaviors and the coupling current patterns were analyzed in detail.

Speaker: Yufan Yan (Tsinghua University)

Numerical investigation of the coupling effect in CORC cable with striated strands_Yan_Wed-Af-Po3.19-05.pdf

695 Wed-Af-Po3.19-06 [51]: Development of Cost-effective Secondary Generation High-temperature Superconducting REBaCuO Tapes for Power Applications

With the performance/price improved, there are increasing market demands and power applications for the cost-effective secondary generation high-temperature superconducting REBaCuO Tapes. In the past decade, main challenges are realized for metallorganic solution-derived (MOD) REBaCuO Coated Conductors to achieve higher critical currents with and without applied fields, such as microcracks or misorientation with increasing thickness of REBaCuO layers, and the competitive effects on the destruction or enhancement of in field critical current density performance Jc(H) with a large amount of artificial disorders. In the present talk, we report our recent efforts on the improvement of the superconducting thickness and associated current-carrying abilities in the field for MOD-derived REBaCuO coated conductors.

It is revealed that the low fluorine, reduced atmosphere pressure, chemical doping and controllable heterostructures are effective for MOD technique to improve the in-plane texture as well as to suppress the microcracks for the film thickness up to 2-3 μm. More than 500 hundred meters of MOD coated conductor tapes with the above thickness of superconducting multilayers or heterostructures exhibit excellent biaxially textured and superconducting performances. The critical currents along the long tapes reach 500 A/cm-width at 77 K, measured by both reel-to-reel transport and inductive systems. As well, various artificial techniques, including chemical doping, ion irradiation, multilayers, or heterostructures of superconducting layers are investigated on the REBaCuO coated conductors, showing the cost-effective MOD technique very promising for the achievement of high-quality coated conductor tapes.

Speaker: Prof. Cai Chuanbing (Shanghai Key Laboratory of High Temperature Superconductors, Shanghai University；Shanghai Creative Superconductor Technologies Co. Ltd. )

696 Wed-Af-Po3.19-07 [52]: Study on Mechanical Properties of Quasi-identical Superconductor Strands Stacked by 2mm Wide REBCO Tapes

Abstract—Due to its excellent performance in critical current, REBCO high-temperature superconductor has important applications in superconducting strands, superconducting cables, superconducting magnets, and superconducting transformers. However,high-temperature tapes are subject to unpredictable mechanical stresses in various applications, and excessive stress will cause permanent damage to the tapes. The critical bending radius, the critical tensile stress, and the critical twist angle and n value of 2mm wide REBCO high-temperature tape were studied numerically and experimentally in this paper. At the same time, the bending, stretching and twisting characteristics of quasi-identical high-temperature superconducting strands stacked by 2mm wide RECBO tapes were further studied. The conclusions obtained can provide important data support for the practical application of superconducting tape.
Index Terms—High-temperature superconducting tape, high-temperature superconducting strand, bending characteristics, tensile properties, twisting characteristics, critical current

Speaker: Shuwen Ma (North China Electric Power University)

Shuwen Ma.pdf

697 Wed-Af-Po3.19-08 [53]: Effect of Combination Twisting with Bending Characteristics on Critical Current of Quasi-Isotropic HTS Strand

The commercial coated conductors (CCs) are at present available in the form of thin strips with high critical current density and excellent mechanical properties. To realize high current carrying capability, several cable conductors were proposed by assembling a large number of CCs. One of them is so called quasi-isotropic strand consisting of four sub-strands by stacking a number of CCs. In the application of conductor and cable, the bending cable is essential and the twisting is an effective technique for uniform current distribution which reduces AC losses of the cable and then improves its stability. In this paper, the strain mathematical characterization of a quasi-isotropic strand (Q-IS) is studied under conditions of bending, twisting and combination of both. The chosen set of Q-IS mechanical parameters satisfies electromechanical limitations and provides feasibility for its practical application.

Key Words: bending, critical current, twisting, quasi-isotropic strand (QI-S)

Speaker: Dr Yang Nie

poster-Yang Nie.pdf

Wed-Af-Po3.20 - CCT Magnets and Field Quality of Accelerator Magnets

Conveners: Damien Simon (Université Paris-Saclay), Federica Pierro (Tufts University)

698 Wed-Af-Po3.20-01 [54]: CCT Type Twin aperture Superconducting Quadrupole Design for CEPC Interaction Region

Iron free twin aperture superconducting quadrupole in the interaction region is a key technology to increase the luminosity for the high energy particle collider. The Circular Electron Positron Collider (CEPC) that China plan to build in the next 10 years, has the center-of-mass energy of 240 GeV and 33 mrad cross angle at the interaction regions. The beam separation distance at the front end of the final focusing quadrupoles QD0 (2.2m away from the interaction point) is only 72 mm, whereas the diameter of the beam pipe is 40 mm which left the useful space for the coils is very tight. Build QD0 qudarupole by using the Rutherford cable is not in practice, which needs large space and special collar to confine coil to prevent quench. In recent years, with the rapid development of the Machine tool CNC, machine precision for spatial curves is greatly improvement. A bundle of thin superconducting wires can be wound into the pre-machined slot in coil former. The coil has a Canted Cosine Theta（CCT) type, the winding direction is in a fix angle with respect to the former. The coils can also be designed with the combination of the several function magnets, or can be used to cancel out the unwanted harmonics. For QD0 magnet in CEPC, the coils in the two apertures are nearly contacted, high order harmonics will be produced from the magnetic field crosstalk, which can be calculated in precision previously. This paper will present the CCT type for the QD0 magnet, where the shape at the coil end is optimized by added several opposite harmonics to cancel out the unwanted harmonics. The axial solenoidal field compensation scheme is also present for beam dynamic requirement. Two single CCT quadrupole prototypes with each has the 500mm long will be built to testify the design idea, they will be test in the vertical Dewar at the similar fixed position as that of the QD0 quadrupole.

Speaker: Prof. Quanling Peng (Institute of High Energy Physics, Chinese Academy of Sciences)

Peng Quanling(MT-26).pdf

699 Wed-Af-Po3.20-02 [55]: No Insulation CCT Coils for Superconducting Accelerator Magnets

The Canted Cosine Theta (CCT) magnet design is typically fabricated by winding individual turns into grooves machined into a metallic mandrel. This allows for precise placement of the conductor for field quality and also provides mechanical support against the Lorentz forces on an individual turn level. A new concept is explored in which the electrical continuity between adjacent turns is broken by means of a gap in the winding mandrel. In this case, no isolation of the turns to the winding mandrel is necessary, eliminating the need for turn to mandrel insulation. Insulation systems for Nb3Sn CCT magnets have so far consisted of a glass sleeve or braid over the conductor which is then vacuum impregnated with epoxy resin post reaction. With the new concept, the conductor can be wound into a mandrel without insulation, reacted, and then impregnated with a conducting material (for example with a low melting point metal). This new approach will be evaluated with respect to the previous glass and resin insulation system with a focus on: (1) improved efficiency due to elimination of the glass, (2) reduction in the quench disturbance spectrum by removal of the brittle resin, (3) improved cleanliness of the reaction process by removal of the glass and sizing, and (4) increased thermal stability of the coil due to being in close contact with conductive material. The reduction of mandrel stiffness due to the gaps will be studied using finite element modeling with possible stiffening mechanisms proposed where necessary. Finally, an initial study of the fabrication steps for such a coil will also be presented with a focus on manufacturing of the winding mandrel.

Speaker: Lucas Brouwer (Lawrence Berkeley National Laboratory)

MT-Vancouver-19-poster-brouwer_vfinal.pdf

700 Wed-Af-Po3.20-03 [56]: Design and Test of a Canted-Cosine-Theta Superconducting Quadrupole Prototype For CiADS Project

The Superconducting Linac of the CiADS (China Initiative Accelerator Driven System) project contains parts of quadrupoles with conventional design. The length of the magnets takes up a lot of space on the Linac. In order to make it more compact, a 40T/m Canted-Cosine-Theta (CCT) superconducting quadrupole prototype is presented, which is put into one cryomodule with solenoids. The design comprises two layers of oppositely wound helical windings to generate high quality quadrupole. The ten wires, insulated with Nylon braid are wound once into the 2 mm wide by 5 mm deep rectangular channels. This paper describes the detailed design based on the CCT concept and reports on the fabrication and coil winding of the magnet prototype. Finally the coil is successfully energized to the design current without a quench.

Speaker: Dr Yu Liang (IMP,CAS)

701 Wed-Af-Po3.20-04 [57]: The Effects of Manufacturing Errors on Field Quality of a Canted-Cosine-Theta Twin Aperture Beam Orbit Corrector

The High Luminosity LHC (HL-LHC) project, as an upgrade of the large hadron collider (LHC), is to be started in 2020. A set of twin aperture beam orbit corrector with Canted-Cosine-Theta (CCT) dipoles will be developed in China, with a field quality requirement of 10-3 in the two apertures. Cooperating with CERN, a twin aperture corrector is being fabricated as the prototypes before the series production. The corrector consists of two apertures and for each aperture there are two layers of CCT coils winded on aluminum formers by using 10 NbTi wires. During the fabrication of the CCT coils, certain manufacturing errors including the former tolerance error, rotation error, concentricity error and winding error were appeared, which affect the field harmonic components. This study analyzed the effects on field harmonic components by these manufacturing errors. Suggestions from the analysis results are provided the further series production of the 2.2-m orbit correctors.

Speaker: Dr Shaoqing Wei (Institute of High Energy Physics,Chinese Academy of Sciences(IHEP,CAS))

MT26-Poster-wsq.pdf

MT26-Poster-wsq.pptx

702 Wed-Af-Po3.20-05 [58]: Design considerations of an alternating-gradient canted-cosine-theta superconducting magnet applied to proton therapy

As a novel superconducting magnet scheme, Canted-Cosine-Theta(CCT) magnet has demonstrated advantages of superior field quality and structure compactness. Combining with Alternating-Gradient (AG) field feature, CCT magnets can be applied to proton therapy gantries with the momentum acceptance significantly increased. This paper will introduce design considerations of a 135 degree AG-CCT magnet for proton therapy gantry, including design and optimization of magnetic field with AG combined function. Technical issues covering the choice of superconducting coils, layer scheme and mechanical structure of the CCT magnet will also be discussed.

Speaker: Mr Wenjie Han (Huazhong University of Science and Technology)

Wed-Af-Po3.20-05 [58].pdf

703 Wed-Af-Po3.20-06 [59]: A Transducer for Measuring the Field Quality in Superconducting Solenoids

At CERN the critical current of superconducting wires is measured in four test stations that use high-field superconducting solenoid magnets achieving up to 15 T. The reduction of the measurement uncertainty requires the field mapping of the solenoids in their operating condition. This paper presents the design, manufacture, and application of solenoidal-field transducers based on nested pairs of induction coils, which are moved along the axis of the magnet. The system yields an accurate measurement of the average longitudinal and transverse field components as a function of the sensor`s longitudinal position. The radial dependence of the magnetic field can be estimated directly from the nested coils of different diameters or indirectly by applying the theory of pseudo-multipoles in solenoidal magnets. In this way, the transducer can be validated and the error estimation for the field measurement can be derived. The results of the magnetic measurements are finally presented and discussed.

Speaker: Carlo Petrone (CERN)

MT26_CPetrone_MT26-Wed-Af-Po3.20-06.pdf

MT26_CPetrone_MT26-Wed-Af-Po3.20-06.pptx

704 Wed-Af-Po3.20-07 [60]: Vertical Magnetic Field Measurements of Full-Length Prototype MQXFAP Quadrupoles at Cryogenic Temperatures for Hi-Lumi LHC

The U.S. HL LHC Accelerator Upgrade Project (AUP) (previously LARP) collaboration and CERN have joined efforts to develop high field quadrupoles for the Hi-Lumi LHC upgrade at CERN. The US national laboratories in the AUP program will deliver 10 cryostatted magnets and each cryostat has two 4.2 m long Nb3Sn quadrupoles with 150 mm aperture. The vertical magnet testing facility of the Superconducting Magnet Division (SMD) at Brookhaven National Laboratory (BNL) has been significantly upgraded to perform testing in superfluid He at 1.9 K. Magnetic measurement is an essential step in the AUP magnet to monitor production process and to ensure that the magnetic fields meet the functional requirements and acceptance criteria. We have successfully performed magnetic measurements on the MQXFAP2 magnet in 2018 and the measured field data has provided information on the mechanical assembly and integration. The MQXFAP1b magnet is a magnet reassembled from three coils used in MQXFAP1 and one new coil and it will be tested at BNL beginning in April 2019. This paper will report further magnetic field analysis on the MQXFAP2 and recent measurement activities on MQXFAP1b. The paper will include warm measurement at room temperature, comparison between BNL and Lawrence Berkeley National Laboratory (LBNL) warm measurements, cold measurements at 1.9 K, detailed field analysis and the relationship between the field harmonics and the geometric asymmetries along the axial direction. In addition, recent developments of the magnetic field measurement systems at SMD/BNL will be reported.

Acknowledgement
This work was supported in part by the U.S. Department of Energy, Office of Science, Office of High Energy Physics, through the U.S. LHC Accelerator Research Program, and in part by the High Luminosity LHC project at CERN.

Speaker: Honghai Song (Brookhaven National Laboratory)

705 Wed-Af-Po3.20-09 [61]: A flexible search coil set-up for magnetic measurements of accelerator dipole magnets

Search coils are used for fast and reliable measurements of field integrals as well as integral homogeneities of dipole magnets. A long experience exists at GSI using search coils in series measurements of synchrotron dipoles as well as measurements of dipoles with large deflecting angles.
The biggest advantage of this technique is a direct and fast measurement of the field integral. Current technology, however, always required a dedicated coil for each bending radius and length. A prominent example is High Energy Beam Transfer (HEBT) of the FAIR project with 6 different radii between 4.5m and 167m. In addition to the 6 coils, radius dependent moving and guiding systems are necessary.
To overcome the above mentioned drawbacks we developed a modular search coil system with adjustable radius including the support and movement system. The features of the system and measurement results are presented.

Speaker: Dr Carsten Muehle (GSI Helmholtzzentrum fuer Schwerionenforschung)

Flex_coil_Poster.pdf

706 Wed-Af-Po3.20-10 [62]: Presentation withdrawn

707 Wed-Af-Po3.20-11 [63]: Presentation withdrawn

708 Wed-Af-Po3.20-12 [64]: Presentation withdrawn

709 Wed-Af-Po3.20-13 [65]: A rotating coil system based on CMM for high gradient small aperture quadrupoles in HEPS-TF

A new rotating coil measurement system based on the CMM is developed for measuring the High gradient small aperture quadrupole for the HEPS-TF. The system is located on the CMM's marble platform. The CMM and two Newport translate stages are combined to align the rotating coil to the magnet center within an accuracy of 10 μm. The integrated gradient strength, the field quality and the magnetic center of a prototype high gradient small aperture quadrupole magnets are measured. Also the harmonic compensation is done to meet the multipole field requirement. The overview of the measurement system, the measuring process, some validated simulations, and primary results of the two prototype quadrupoles are illustrated in this paper.

Speaker: Dr Yingshun Zhu (Institute of High Energy Physics, CAS)

710 Wed-Af-Po3.20-14 [66]: Magnet end shaping of the Future Circular Collider Main Quadrupole: optimization and validation

In the frame of a collaboration agreement between CERN and CEA, the Main Quadrupole (MQ) design of the so-called Future Circular Collider (FCC) has to be investigated. So far, a 2D electromechanical design has been proposed in the FCC Conceptual Design Report [1,2]. Here, the FCC MQ design is further investigated through a 3D electromagnetic design. The integrated field quality over the magnet length is analyzed. In parallel, a small mock-up is set up in order to validate the 3D end design of the 2 layer magnet by means of a Nb3Sn cable very close in dimension to the final one and 3D printed end spacers. Layer jump curvature tests are reported, too.

[1] “Future Circular Collider Study. Volume 3: The Hadron Collider (FCC-hh) Conceptual Design Report”, preprint edited by M. Benedikt et al. CERN accelerator reports, CERN-ACC-2018-0058, Geneva, December 2018. Submitted to Eur. Phys. J. ST
[2] C. Lorin et al. “Exploration of two layer Nb3Sn designs of the Future Circular Collider Main Quadrupoles”, IEEE Transactions on Applied Superconductivity, vol 29, Issue 5, 4001005

Speakers: Mr Etienne Rochepault (CEA Paris-Saclay), Helene Felice (CEA Paris-Saclay)

posterMT26CL_FCCquad.pdf

posterMT26CL_FCCquad.pptx

711 Wed-Af-Po3.20-15 [67]: Topology Optimization of the Pole Shape in Passive Magnetic Channel using MMA Method

Passive magnetic channel is a kind of beam focusing elements in cyclotron. It consists of several soft iron bars which are magnetized by the main field in cyclotron. One of the common method to design pole shape of the magnetic channels is based on a current sheet analytical model. Geometry parameters of the rectangular pattern pole shape are designed using this model. In this paper, we proposed a topology optimization method to design the pole shape in passive magnetic channel, this method does not require any fixed geometry pattern or initial design. The nonlinear static magnetic finite-element analysis model is used to calculate the objective magnetic field function. Persuade iron material with variable density is used to describe the iron distribution. Method of Moving Asymptotes (MMA) is used to optimize the control variable of iron density distribution on magnetic channel cross section. A penalization factor is used to get a thresholding iron distribution results. It ensures the final design without density related persuade iron material. In three numerical examples, magnetic channels for a 250 MeV superconducting cyclotron is provided, where the design goal is to provide the given magnetic field gradient and bending angle. The relationship between the design goal and the pole shape pattern is discussed. It reveals that magnetic channel pattern with only 2 iron bars is possible for some design goals.

Speaker: Dr Lige Zhang (Huazhong University of Science and Technology)

Wed-Af-Po3.20-15.pdf

Wed-Af-Po3.21 - Nb3Sn Wires

Conveners: Ildar Abdyukhanov (VNIINM (Bochvar Institute)), Matthias Mentink (CERN)

712 Wed-Af-Po3.21-02 [68]: Refining the grain size and improving critical current in tube type Nb3Sn conductor in Hyper Tech

The internal oxidation technique could generate oxide nano particles in Nb3Sn strands, which could significantly refine the Nb3Sn grain size and boost the high-field critical current density. Our recent Ta doped ternary APC Nb3Sn wires with ZrO2 pinning center demonstrated substantial grain refinement and significantly increased Jc,nonCu, while retaining the high Bc2 values of the best ternary Nb3Sn conductors. The non-Cu Jcs of these APC conductors has reached nearly 1500 A/mm2 at 16 T/4.2 K, which approaches the current CERN FCC spec. Their layer Jc reaches 4700 A/mm2 at 16 T/4.2 K - more than double the present best ternary Nb3Sn conductors. Even so, further improvements are possible using straightforward methods, and by using these we are pushing the fine grain fractions in these conductors up a further 10% to 20% which is expected to lead directly to proportionate increases their Jc. This strand has been made to 61-filament restack strands getting filament size of 45 micros at the 0.5 mm strand. In this paper, we will report the recent progress in this APC Nb3Sn wire.

This work was supported by the US Department of Energy, Office of High Energy Physics, Grants No. DE-SC0017755 and DE-SC0013849.

Speaker: Xuan Peng (Hyper Tech Research Inc.)

713 Wed-Af-Po3.21-03 [69]: Challenges and Perspectives of the Phase Formation of Internally Oxidized PIT-Type Conductors

The generation of nano-scale precipitates from an additional alloying component in the Nb-alloy precursor of Nb3Sn-based wires is considered one of the promising techniques to refine the grain size of the superconducting phase and boost the Jc beyond the specification of a Future Circular Collider (FCC). Much effort by research groups could demonstrate that this technology is viable and can lead to the desired grain refinement if sufficient oxygen can be supplied to the Nb-alloy precursor.

However, the addition of oxygen as an additional reacting agent renders the already convoluted reaction scheme of high tin conductors even more complex. In order to understand and adjust the phase formation, two key features need to be addressed: (i) The relative diffusional velocity of oxygen and tin and (ii) the impact of oxygen on the phase formation of Nb-Sn intermetallics.

Due to their flexibility, Powder in Tube (PIT) concepts have been chosen to efficiently benchmark new conductor layouts. Bruker has developed, manufactured and tested more than 30 different designs in which oxygen and tin diffuse from the same or different locations within the filament. Nb1Zr or Nb2.5Ti was used as the initial alloys and oxygen was supplied from SnO2 or CuO powders. To assess the phase formation and grain size, bouquet conductors consisting of different monofilaments were introduced as an innovative tool for rapid prototyping.
The differences in phase formation between oxidized and reference samples could be illustrated. Based on this data, the effectiveness of the type, location and composition of the oxygen source to generate nano-scale precipitates or to refine the grain size was evaluated. The critical temperature and thereby the oxygen concentration in the Nb-alloy that remains after heat treating was analyzed to quantify the oxygen release provided by the different layouts.

This work was partially supported by CERN as a part of the FCC conductor development program as well as the Institute for Technical Physics (ITEP) at the Karlsruhe Institute of Technology (KIT).

Speaker: Carl Buehler (Bruker EST)

Poster MT 26-upload.pdf

714 Wed-Af-Po3.21-04 [70]: Mechanical strength evaluation of the internal matrix reinforced Nb3Sn multifilamentary wire using Cu-Sn-In ternary alloy matrix

The degradations of superconducting properties due to the loading of mechanical stress and strain on the practical Nb3Sn wire are serious problem to apply for the future fusion magnet operated under higher electromagnetic force. Recently, we investigated the internal reinforcement method without reinforcement material using Cu-Sn ternary alloy matrix and found that mechanical strength of bronze processed Nb3Sn wires was improved by the Cu-Sn-Zn ternary alloy matrix. The Cu-Sn-Zn ternary alloy matrix was transformed to the (Cu, Zn) solid solution based on the solid solution strengthening mechanism.
Generally, it is well known that there are many solute elements for the solid solution strengthening of copper binary alloy. For the further mechanical strength improvement, we focused on the Indium (In) as the more effective solute element compared with the Zn element and fabricated bronze processed Nb3Sn multifilamentary wire using various Cu-Sn-In-(Ti) ternary alloy matrices.
In this study, the change of the Vickers hardness before and after Nb3Sn synthesis heat treatment and the transport critical current (Ic) under the uniaxial tensile deformation on the these Nb3Sn multifilamentary wires using Cu-Sn-In-(Ti) ternary alloy matrices were evaluated. We confirmed that Vickers hardness of the matrix after Nb3Sn synthesis heat treatment on the Cu-Sn-In ternary alloy matrix samples was higher compared with the conventional bronze processed sample and was increased with increasing nominal In composition. This would be mainly caused by the (Cu, In) solid solution formation from Cu-Sn-In-(Ti) ternary alloy matrix, as same as the case of the Cu-Sn-Zn ternary alloy matrix. In element would become more attractive solute element of the ternary alloy matrix for the internal matrix reinforcement.
In addition, we also carried out the tensile test under 4.2 K and magnetic field of 15 T on the Nb3Sn multifilamentary wires using various Cu-Sn-In-(Ti) ternary alloy matrices. Transport Ic behavior by the unidirectional tensile deformation on the Nb3Sn multifilamtary wire using various Cu-Sn-In ternary matrices was also reported.

Speaker: Prof. Yoshimitsu Hishinuma (National Institute for Fusion Science)

Poster(MT-26_Wed-Af-Po3.21-04)-2.pdf

715 Wed-Af-Po3.21-05 [71]: Fabrication of new internal tin Nb3Sn wire using Sn-Zn alloy as Sn core

Nb$_3$Sn superconductor is expected to play a vital role even for next generation high field applications. However, the $J_\mathrm{c}$ is approaching to be fully optimized in terms of cross sectional layout and heat treatment condition. Therefore, some drastic solutions are needed for further improvement in $J_\mathrm{c}$.
We have been studying the effect of the element addition to the matrix in internal tin (IT) Nb$_3$Sn wire. One of the attractive additive elements is Zn. We have revealed so far that Zn promotes the Nb$_3$Sn layer synthesis. On the other hand, Ti is well known to be an effective additive to promote Sn diffusion, and enhance $B_\mathrm{c2}$ and $J_\mathrm{c}$. In our conventional brass matrix IT wires, Ti is used to be doped to Sn cores because of the simplicity of the doping method. That also contributed to increase the hardness of Sn cores. However, our previous study revealed that a Sn-Ti intermetallic compound layer is formed during the pre-annealing for Sn/Cu mixing in case that Ti is doped to Sn cores, which seems to avoid smooth outward Sn diffusion. Therefore, it would not be preferable to dope Ti to Sn cores.
The workability of IT wire is actually also an important issue, because, in IT wires, quite soft Sn cores are contained in the composite together with relatively hard Nb, which causes unbalance of the hardness across the composite. This ununiformity was one of the main reasons for wire breakages in our laboratory-scale brass IT wires.
From these reasons, we attempted to fabricate new IT wires using Sn-Zn alloy as central Sn cores, and doping Ti to the matrix and Nb but not to Sn cores. In this study, the drawability of the new IT wire was evaluated. Furthermore, we study Sn, Ti and Cu diffusion behaviors during the heat treatment in detail through microstructural and microchemical observations. The microstructure is correlated with the $J_\mathrm{c}$ performance.

Speaker: Taro Morita

Wed-Af-Po3.21-05_comp.pdf

716 Wed-Af-Po3.21-06 [72]: Fundamental study on the effect of Zn addition into Cu matrix in internal tin Nb3Sn conductors

As a new approach to enhance the Jc property, we have been studying the element addition into the Cu matrix in the internal tin Nb3Sn conductors. We have shown so far that Zn addition promotes the Nb3Sn layer formation, compared to the non-doped Cu matrix Nb3Sn wires.
In this work, we concentrated to investigate the effect of Zn addition on the microstructure during the heat treatment in detail thorough fundamental study. First, various single Cu-Zn/Sn composites were prepared and then their reaction behaviors were observed with respect to the heat treatment condition. The most interesting finding was that the Cu-Zn/Sn diffusion couples resulted in a significantly different reaction behavior from the Cu/Sn diffusion couple. For example, in the Cu/Sn couple, ε phase widely forms together with η phase at the reaction layer at 400 C, while in the Cu-Zn/Sn couple, another ternary Cu-Sn-Zn phase (presumably β-CuZn) forms adjacent to ε phase. This was considerably interesting, because this ternary phase is quite solid and no void is present, while the ε phase contains many voids. The suppression of void formation should be important for the improvement of Cu/Sn interdiffusion during the pre-annealing in the multifilamentary precursor wires. In our laboratory scale Nb3Sn multifilamentary wire samples, the Jc in the Cu-Zn matrix samples is appreciably better than that in the Cu matrix sample, which would be attributed to the improvement of Sn diffusivity in the pre-annealing process. In addition, we investigated optimum Zn content in the Cu matrix, the grain size and the influence of the filament barrier thickness and so on.
The Zn addition into the Cu matrix is fairly interesting for further Jc improvement of the Nb3Sn conductors in terms of uniform Sn diffusion across the matrix and acceleration of the Nb3Sn layer formation.
We are greatly thankful to the late Prof. Tachikawa for everything he have done for us through this research.
This work was partially supported by JSPS KAKENHI Grant Number JP18K04249.

Speaker: Nobuya Banno (National Institute for Materials Science)

MT26_Wed-Af-Po3.21-06 [72]_v2.pdf

717 Wed-Af-Po3.21-07 [73]: Superconducting Properties of Internal Tin Nb3Sn Strands, doped with Ti, Zr and Ti, Ti and Ta.

State-of-art magnetic systems of high-energy physics devices require magnetic fields up to 16 T. Attaining the level of fields in the range of 14-16 T is challenging for Nb3Sn superconductors used for such magnets. In order to increase their critical current density in high fields by optimization of the pinning through the modification of the microstructure of the Nb3Sn filaments, doping with various elements, the introduction of artificial pinning centers, etc. are used.
The paper presents the results of a study of three types of internal tin Nb3Sn strands of the same design, differed by the way of doping with titanium, titanium and zirconium, titanium and tantalum. The diameter of the fabricated strands was 1.0 mm. For the formation of the superconducting phase, a series of two steps heat treatments (HT) were carried out. The temperature of the reaction second stage of HT was varied from 620 to 750 ° C.
The microstructure of the Nb3Sn layer after HT was studied by scanning electron microscopy. Transport properties of the strands samples were measured in magnetic fields up to 18T.
The interrelation of the HT regimes and superconducting properties of the strands investigated, including RRR, Tc and Ic has been analyzed. It has been shown that with an increase of the HT second stage temperature the critical temperature of samples doped with two elements simultaneously shows the tendency to increase, wherein the critical temperature of the samples doped only with titanium has a maximum after HT at a temperature of 700 °C. Studies of the critical current density of the samples in the wide magnetic field range as a function of the HT second stage temperature are presented.

Speaker: Dr Victor Pantsyrny (Bochvqr Institute)

718 Wed-Af-Po3.21-08 [74]: Evaluation of various Nb-rod-method Cu-Nb/Nb3Sn wires designed for practical React-and-Wind coils

The bronze-processed Cu-Nb/Nb3Sn wires, composed of the Nb-rod-method Cu-Nb reinforcing stabilizer around the Nb3Sn filament bundle, have superior mechanical strength at both low temperature and room temperature after Nb3Sn creation heat-treatment. Therefore, in react-and-wind (R&W) process, the Cu-Nb/Nb3Sn wires are able to be handled easily with applying strains not to exceed the irreversible strains that the characteristics deteriorate due to cracks of mechanically brittle Nb3Sn filaments. Moreover, the non-Cu-Jc values of Cu-Nb/Nb3Sn wires have been remarkably enhanced by applying the high tin bronze and the appropriate pre-bending treatment. In this study, we discuss improved acceptable values of tensile stress and bending strain for the various Cu-Nb/Nb3Sn wires in the R&W process and the R&W magnet operations.　Additionally, we propose some specific designs of Cu-Nb/Nb3Sn wires applicable to practical R&W coils, and describe their advantages against the conventional wires such as NbTi wires and wind-and-react (W&R) process Nb3Sn wires.

Speaker: Mr Masahiro Sugimoto (Furukawa Electric Co., Ltd.)

Wed-Af-Po.3.21-08_MT26_M.Sugimoto_Poster_20190925.pdf

719 Wed-Af-Po3.21-09 [75]: Performance Improvements to Nb3Sn Superconducting Wires by bronze route

High performance Nb3Sn superconducting wires, which have high critical current density and low hysteresis loss, are desired for high-field magnet systems. To meet the requirements, investigations on increasing the Sn concentration in the bronze matrix, improving arrangement of Nb filaments and examining a new design of diffusion barrier were carried out. Wires with critical current at 4.2K and 12T above 300A and hysteresis loss at 4.2K and ±3T below 300mJ/cm3 were manufactured. Finer filaments were obtained which are helpful for increasing critical current density. Small and uniform Nb3Sn grains were formed after a long reaction heat treatment. A higher Sn content in matrix led a higher Sn content in Nb3Sn phase, which resulted in a higher critical current density. Using tantalum as diffusion barrier material has a great effect on decreasing hysteresis loss.

Speaker: Dr Ke Zhang (Western Superconducting Technologies Co. Ltd.)

LiuJW-MT26-poster.pdf

LiuJW-MT26-poster.pptx

720 Wed-Af-Po3.21-10 [76]: Effect of Nb3Sn coarse grains on critical current densities of Internal Tin Nb3Sn strand

Nb3Sn strand have significant applications in constructing high-field (> 10 T) magnets and has great potential value in the next 20 years. Internal-tin (IT) Nb3Sn strand has been developed by many methods for the future fusion reactor after ITER with low hysteresis loss. However, how to improve the current densities of Nb3Sn strand has been becoming an important problem with the increasing demand for high Jc Nb3Sn strand. In our study, we found that more than double Nb content should be added within Internal Tin Nb3Sn strand and 2~3 times critical current densities can be enhanced compared with ITER Nb3Sn strand. With this Nb3Sn strand, the phase transition during heat treatment was investigated and new phase (Cu-Nb-Sn) can be produced at 400℃ as the reason of more Nb content added and Cu6Sn5 phase decomposition. The coarse Nb3Sn grains were analyzed and a composite structure (Cu and Nb3Sn) can be produced as Nb element diffusion during Cu-Nb-Sn phase formation. We also found that phase-balance (less Cu-Nb-Sn produced), which can control the formation of Nb3Sn coarse during filaments, can be obtained through element ratio optimization. With this method, coarse grains among filaments can be refined from micron size into nano-size. Effect of varisized coarse grains on the critical current densities was also studied and we found that micron sized Nb3Sn (1~2 μm) grains reduced the the critical current densities severely.

Speaker: Dr Bo Wu (1. National Engineering Laboratory for Superconducting Material, Western Superconducting Technologies (WST) Co., Ltd. 2. State Key Laboratory of Solidification Processing, Northwestern Polytechnical University)

Wed-Af-Po3.21-10 [76] Effect of Nb3Sn coarse grains on critical current densities of Internal.pdf

721 Wed-Af-Po3.21-11 [77]: Impact of transverse compression on the sub-element RRP Nb3Sn strand

For developing 14 Tesla whole body superconducting magnetic resonance imaging (MRI) magnet, a new kind of composite conductor has been preliminary deigned. In current design, a structure of Nb3Sn Rutherford cable-in-channel (RIC) conductor is adopted which is similar to Iseult 11.7T MRI conductor. The composite conductor consists of Rutherford cable and cooper stabilizer with channel. Developing Rutherford cable techniques for composite conductor with High-Jc Nb3Sn strand is important, and a key issue is control the strand deformation. During cabling, the strand would experience plastic deformation under transverse compression, which causes sub-elements damage and degrades the transport performance and residual resistivity ratio (RRR). In this paper, the impact of transverse compression on the sub-element RRP Nb3Sn strand before heat treatment was studied with finite element model (FEM) and experiments, the FEM results and experiment results are compared and analyzed.

Speaker: Dr Yongliang Zhang (Institute of Plasma Physics, Chinese Academy of Science)

Wed Af Po3.21 11 [77].pdf

722 Wed-Af-Po3.21-12 [78]: Heat Treatment Studies of Nb3Sn RRP wires for Superconducting Planar Undulators

NbTi-based superconducting undulators have been developed and proven to increase the brightness by an order of magnitude at high x-ray energies at the ANL Advanced Photon Source (APS). Nb3Sn has the potential to further enhance the performance of SCUs. These Nb3Sn undulators operate at maximum on-conductor field ranges between 4 T and 6 T; such comparatively low field values present stability issues, which was addressed by using 0.6 mm in diameter Nb3Sn wire with small sub-element size, specifically a Restacked Rod Processed (RRP) wire with 150 superconducting subelements over 169 total subelements. The effective sub-element diameter, Deff, of this wire is ~35 µm. At these small Deff values, the critical current density Jc is known to deteriorate. In addition, the Residual Resistivity Ratio, or RRR, of such small diameter wires is very sensitive to heat treatment. A delicate balance has to be found to obtain parameters within operation specifications. In this paper we show performance results from different heat treatments on 150/169 RRP wires between 0.5 mm and 0.8 mm with both high-Sn and intermediate-Sn designs.

Speaker: Emanuela Barzi (Emanuela)

Wed-Af-Po3_21-12_Barzi.pdf

Wed-Af-Po3_21-12_Barzi.pptx

Wed-Af-Po3.22 - Associated Technology I

Conveners: Maria Baldini (FNAL), Dr Sasha Ishmael (Lupine Materials and Technology)

723 Wed-Af-Po3.22-01 [79]: Study of magneto-resistance for low magnetic field measurement

High-Q operation of Superconducting Radio Frequency cavity reduces power loss at surface and is desirable for CW operation.
For high-Q operation, it is needed to reduce the surface resistance, which is a summation of the BCS resistance and residual resistance. It was found that the residual resistance comes mostly from magnetic flux trapping during cool down process.
A magnetometer called “flux gate sensor” has been used to measure the ambient magnetic field but it is a large sensor compared to a cavity size and it is very costly.A sensor utilizes the magneto-resistance effects, such as AMR (Anisotropic-Magneto-Resistive), is smaller and less expensive than a flux gate sensor.
We have examined characteristics of magneto-resistance sensors at the room temperature and cryogenic temperature.The results are reported in this paper.

Speaker: Dr Ryuichi Ueki (KEK)

MT26-Wed-Af-Po3.22-01-poster.pdf

724 Wed-Af-Po3.22-02 [80]: Effect of Specimen Shape on Eddy Current Distribution in Large Single Sheet Tester

Laminated silicon steel sheet, which is widely applied in electrical engineering, such as cores of power transformer and electrical machines, usually suffer from stress caused by a quantity of factors such as non-uniform clamping forces, wavy laminations, or temperature gradients. Therefore, the measurement of magnetic properties under stress is important. A remarkable number of works demonstrate that the large single sheet tester (SST) is suitable for applying stress and the problems related to the large SST are discussed in detail. However, the development of large SST is restricted by the defect that the systematic error was high and, in the worst case, reach up to 28%, which is attributed to the flux penetration into the specimen causes additional eddy current loops closing in the specimen’s plane. In this paper, the effect of specimen shape on eddy current distribution in large SST are mainly evaluated by numerical analysis and experimental comparison of different shapes of cross-shape specimen under various yoke constructions. The additional eddy current closed loops in the specimen’s plane will be cut off by the means of slotting in the specimen. Three kinds of SST construction are applied to test different shapes of samples and losses of each specimen are compared and analyzed. The results demonstrates that slotting is beneficial to decrease the additional eddy current loss and increase the measurement accuracy.

Speaker: Yongjian Li (Hebei University of Technology)

Wed-Af-Po3.22-02 [80] Effect of Specimen Shape on Eddy Current Distribution in Large Single Sheet Tester.pdf

725 Wed-Af-Po3.22-03 [81]: Vibration Control of Vertical Motion for a Superconducting EDS Train

With an operating speed of over 500 km/h and large levitation gap of over 100 mm, electrodynamic suspension (EDS) trains have drawn extensive attention in the railway industry due to these innate merits. The operating performance of the EDS train is strongly affected by the self-excited vibration caused by the varying magnetic field and track irregularity. Being the emphasis of this paper, vibration Control is essential therefore to improve operating performance. Various control methods such as pole configuration, hysteresis-advance adjustment and speed feedback were adopted in this paper. Moreover, the active controller based on pole configuration and hysteresis-advance adjustment as well as the semi-active controller named skyhook damper based on speed feedback was specially designed for EDS system. Limited by the unknown distribution of track magnetic field, only the track irregularity was employed as the excitation source imposed to above controllers. The obtained results show that the above active and semi-active controllers designed for EDS system can effectively suppress the self-excited vibration. Potential applications of these controllers could be expected in the future design of control system for EDS train.

Key words: electrodynamic suspension (EDS) train, self-excited vibration, active controller, skyhook damper

Speaker: Mr Gang Li (Southwest Jiaotong University)

726 Wed-Af-Po3.22-04 [82]: A pulsed current based critical current measurement system for long REBCO coated conductors

Long wire critical current (I_c) characterization is important for fabrication of superconducting magnets. Many inductive and transport I_c measurement methods have been developed for km scale rare earth cuprate (REBCO) based Coated Conductors (CC), which is the most promising high temperature superconducting (HTS) material for magnet applications. As a direct indication of the current carrying capability, transport measurement if favored by most tape users. However, the traditional transport measurement technique has its limitations for long tape characterization. The speed of transport measurements is usually not high enough for kilometers of tape, and direct current (DC) measurement also has a certain risk of tape damage due to the Joule heating at current contacts, especially for some special CCs with higher contact resistance, e.g. stainless steel encapsulated CCs. For long wire measurements, the risk of tape damage is generally higher than acceptable. A transport measurement system was developed in this work, where pulsed current is used to reduce Joule heating thus reduce the risk of tape damage. To avoid the low measurement speed of normal pulsed current measurements, a special technique is adopted. Different long CCs, especially the ones with different encapsulation layer materials were measured by the system. During the tests, no tape damage was found. The I_c results were compared with the conventional four-point method for the short samples, the measured I_c values well correspond to each other.

Speaker: Ms Yiwen Chen (Shanghai Jiao Tong University)

post 陈怡文---0918-3.0.pdf

727 Wed-Af-Po3.22-05 [83]: Trapped Field Charateristics of A HTS Magnet with Two Holes Using Four Magnetization Methods

A Bitter-like high temperature superconducting (HTS) magnet stacked by RE (RE=rare earth )Ba-Cu-O annular plates and magnetized by flux pump is attractive in application of magnet operating in persistent mode (PCM). Its self- and mutual inductances is essential for calculation of stored energy which has significant something to do with its stability such as quench and recovery as well as protection measures. The analytical calculation of self- and mutual-inductances is obtained based on Modified Neumann's formula instead of the linear integral current with the surface integral current. Meanwhile, the self-inductance and mutual inductance matrices of the HTS magnet which could adjust the numbers of stacked annular plates automatically are also simulated by Matlab programming. It is shown that the analytical results are good agreement with the simulated ones.
Key words: inductance, Matlab matrices, Neumann’s formula, REBCO annular magnet

Speaker: Yanqing Lu (NCEPU)

Poster-Yukai Qiao.pdf

728 Wed-Af-Po3.22-06 [84]: Numerical study of the performance of HTS switch under perpendicular magnetic field

HTS switch is a critical component for many HTS applications such as flux pumps, fault current limiters. The dynamic response of the HTS switch is a critical to the the performance of the flux pump and fault current limiters. In this study, we build a thermal coupled numerical model for a HTS switch. We use this model to analyse the performance of a HTS switch under different perpendicular magnetic fields when carrying different transport current. The dynamic response of the switch will be obtained and the numerical results will help better design the HTS switch.

Speaker: Jun Ma (Cambridge Universitry)

Wed-Af-Po3.22-06 [84].pdf

729 Wed-Af-Po3.22-07 [85]: Development of fine shimming technique with magnetorheological fluid

Two physics experiments using Muon are proceeded in J-PARC, named MuSEUM and g-2/EDM experiments. Objectives of these experiments are to measure hyperfine transitions in the ground state hyperfine structure interval of Muonium and to measure the anomalous magnetic moment of the positive muon, respectively. High homogeneity of magnetic field is essential to achieve the physics goals of both experiments. In general, iron pieces are used to shim a magnetic field to achieve required homogeneity, with the level of a few ppm. However, a fine-tuning shimming using iron pieces needs a lot of time effort due to a large magnetization. The further small iron pieces are required for the fine tuning, but it is difficult to assure sufficient manufacturing accuracy.
We are developing a new shimming technique using magnetorheological fluid. That has smaller magnetization than iron and the volume can be easily controlled because of a nature of liquid, so that it seems to control magnetic field precisely. Magnetizations of some commercial fluids are measured and capability of magnetic field shimming using fluids are studied.
In addition, a multi-channel NMR probe with high resolution of less than 10 ppb are being developed. The magnetic field generated by superconducting magnet would shift since temperature and pressure change etc., which cause change of magnet size. Therefore, we have to measure the magnetic field as quickly as possible. Besides, we also need to suppress an amount of the materials of the field measurement probe because the magnetizations of the probe own would degrade resolution. In order to fulfill these requirements, a multi-channel NMR probe with simultaneous reading is being developed. The probes compose of not only non-magnetized but also suppressed to less quantity.
This presentation reports the status of the development with the system of generating the homogeneous magnetic field.

Speaker: Ken-ichi Sasaki (KEK)

WedAfPo3-22-07.pdf

Wed-Af-Po3.23 - Resistive and Pulsed High Field Magnet II

Conveners: Tao Peng (Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology), Frans Wijnen (Radboud University Nijmegen)

730 Wed-Af-Po3.23-03 [88]: Design, Construction and Operation of New Duplex Magnet at Pulsed Field Facility-NHMFL

The Pulsed Field Facility (PFF)- National High Magnetic Field Laboratory (NHMFL) in Los Alamos, New Mexico has developed and operated a several types of ultra-high field pulsed magnets, including 100 T Multi-shot, 60 T Long Pulse, and an array of small 65 T magnets for users. Separately powering (nested) coils allows to both reduce the driving voltages and have a further degree of control over the pulse duration and therefore the current carrying capacity in conductor to maximize the produced magnetic fields. Duplex design with two nested coils powered separately by two capacitors has been used at several pulsed field centers to increase the generated magnetic field. In last year, PFF-NHMFL focus on developing such a magnet to generate maximum magnetic field up to 78 Tesla using existing 16 kV – 4 MJ capacitor bank. The magnet is expected to prove 75 Tesla magnetic field during regular operation. A Metal Oxide Varistor (MOV) bank is used to protect the capacitor bank and its associated electrical components from the overvoltage in the case of fault happen in the duplex magnet. This paper will outline the design, construction and operation of that magnet and the MOV bank.

Speakers: Doan Nguyen (LANL), James Michel (Los Alamos National Laboratory)

731 Wed-Af-Po3.23-04 [89]: Design and Test of the 64 T with 10ms Flat-Top Magnetic Field System Driven by Capacitor at the Wuhan National High Magnetic Field Center

The 64 T with 10ms flat-top magnetic field system driven by capacitor was manufactured and tested at the Wuhan National High Magnetic Field Center (WHMFC). The system consists of the primary circuit and the secondary circuit driven by capacitor banks as they are normally used to generate a pulsed field. The magnet coil and the outer winding of the transformer are connected in series to form the primary circuit. The secondary circuit includes the inner winding of the transformer. The current in the magnet circuit will decrease when the secondary circuit is triggered due to the electromagnetic coupling. A flat-top current in the magnet circuit can be obtained by adjusting the discharge voltage and trigger time of the secondary circuit. The primary and the secondary circuit are driven by ten and two 1MJ capacitor banks. Fields up to 64 T with 10ms flat-top have been obtained with a conventional user magnet used at the WHMFC.

Speaker: Shuang Wang (Huazhong University of Science and Technology)

Wed-Af-Po3.23-04_S. Wang.pdf

732 Wed-Af-Po3.23-05 [90]: The Axial Displacement and Its’ Effects on the Mechanical Behavior of Pulsed High-field Magnets

Traditional pulsed design software, such as PULSE and PMDS, only analyzes the stress distribution on the mid-plane of magnets. The calculations are under the assumption of the constant strain and adjacent materials are perfectly bonded together. These approximate calculations are effective in most cases but cannot take the axial elastoplastic of magnets in consideration and could make significant errors in high-field operation conditions. In this paper, the axial displacement and its’ effects on the mechanical behavior of pulsed high-field magnets are studied. 2-D finite element analyses (FEA) of magnets are taken in ANSYS, with the contact pairs inserted in all the interfaces between the conductors and the reinforcements. Simulations show that the accumulation of the axial compression along the axis leads to a large axial displacement at the end of the magnets, which enhances the risk of short circuits of the windings. Besides, the axial displacement makes the calculated contact status different from 1-D results. The stress distribution of magnets is totally changed. Furthermore, several influencing factors of the axial displacement of magnets, which couldn’t be account in 1-D simulations, are found out. First of all, the distribution and the dimension of the cross-section of the conductors. A flatter magnet has a better axial stability. Secondly, the transverse stiffness of the materials. High transverse stiffness makes a new requirement for the selection of the materials of magnets. Last, the friction coefficient of the interfaces between the conductors and the fiber reinforced plastic (FRP). These results indicates that analyses of the axial mechanical behavior are necessary for the design of magnets over 75T. The factors mentioned above must be account.

Speaker: Dr Siyuan Chen (Wuhan National High Field Center, Huazhong University of Scienc)

Wed-Af-Po3.23-05.pdf

733 Wed-Af-Po3.23-06 [91]: Integrating Modeling Toolchain into High Field Magnet Monitoring and Control system.

The Laboratoire National des Champs Magnetiques Intenses (LNCMI) is a French large scale facility, part of the European Magnetic Field Laboratory (EMFL), enabling researchers to perform experiments in the highest possible magnetic field. On its Grenoble site, the LNCMI provides up to 37 teslas combining a PolyHelices and Bitter magnet.

Following the power upgrade from 24 to 30 MW, the control and monitoring have been completely redesigned. Magnet activities are recorded into a database and can be easily tracked down on a web interface. Magnet characteristics (namely geometry and materials property) are also stored into a database. This allows to keep a record of all events during a magnet lifetime, to have access to instant data such as power consumption, cooling water temperature, ...

In parallel, a numerical toolchain, HiFiMagnet has been developed in collaboration with Institut de Recherche Mathematique Avancee (IRMA) from Strasbourg University to simulate the magnets ranging from simple OD to full 3D models. Over the last three years, HiFiMagnet has reached a level of maturity
and has been selected as a pilot for the MSO4SC H2020 project. MSO4SC is an e-infrastructure that provides services and resources for simplifying the use and development of large scale applications on HPC in the cloud.

To get better control and follow-up on our magnets, we have connected the monitoring system and MSO4SC platform in order to:

Extract and setup HiFiMagnet simulation from an existing magnet in operating condition,
Provide predictive behavior of the magnets from a control perspective,
Help researchers by providing more accurate field map to prepare, design and exploit their experiments.

This work is illustrated by examples targeting both the magnet designer and the end-user.

ACKNOWLEDGMENTS: HiFiMagnet has received funding from the European Union's Horizon 2020 research and innovation program under grant agreement No 731063. The authors also acknowledge the support of LNCMI, Centre de Modélisation et de Simulation de Strasbourg (CEMOSIS), the Labex IRMIA and the FUI MOR_DICUS.

Speaker: Dr Christophe Trophime (Christophe)

MT26.pdf

734 Wed-Af-Po3.23-07 [92]: Modular Toroidal Copper Coil for the Investigation of Inductive Pulsed Power Generators in the MJ-Range

Inductive pulsed power generators apply coils as powerful short time energy storage which is an ordinary mean to deliver pulses of high power to loads like electromagnetic accelerators¹. This article deals with the design, simulation, construction, electrical characterization and a pulsed stress test of a modular toroidal coil. The coil was made from 180 D-shaped copper discs and has an inductance and dc-resistance of 1 mH (@ 50 Hz) and 6 mΩ. Its height, diameter and weight are 0.4 m, 1 m and 1 ton, respectively. It is designed to store more than 1 MJ of energy. The coil is segmented into 20 sub-coils with corresponding interfaces whose number of windings can be varied in order to allow its use in different current amplifying topologies like the XRAM circuit or pulse transformer.

¹O. Liebfried, "Review of Inductive Pulsed Power Generators for Railguns", IEEE Trans. Plasm. Sci., vol. 45, no. 7, pp. 1108-1114, 2017

Speaker: Oliver Liebfried (French-German Research Institute of Saint-Louis)

MT26 Poster LIEBFRIED Wed-Af-Po3.23-07.pdf

735 Wed-Af-Po3.23-08 [93]: Presentation withdrawn

736 Wed-Af-Po3.23-09 [94]: Non-destructive testing of high strength conductors for high field pulsed magnets

High field pulsed magnets at the NHMFL use high strength conductors up to 90% of its ultimate tensile strength. Therefore it is critical to ensure that the conductor is free of defects for its entire piece length which could be as long as a few hundred meters. It is known that in the wire drawing process, internal crack or so-called ‘chevron crack’ can occur due to unsuitable drawing die schedule, poor lubrication and so on. These cracks occurs infrequently along the wire, so tensile tests of samples cut from ends of a long length conductor often miss the problem. In addition, small inclusions on the wire surface might have impact on its fatigue properties. So it is critically important to inspect these defects using non-destructive testing (NDT) methods.
In this paper, we present results of our NDT inspection of Glidcop AL-60 and Cu-Nb wires using Eddy current testing, ultrasonic testing and x-ray tomography (2D and 3D). The minimum detectable flaw sizes for our conductors are established for each NDT technique. Some chevron cracks are found in some Glidcop conductors by all three NDT techniques. We have developed a long length Eddy current wire inspection capability, the technical details of which will be presented.

Acknowledgement
We would like to thank Mr. Daniel Bone of Delphi Precision Imaging for x-ray tomography, Mr. Chuck Edie of Olympus NDT for eddy current and ultrasonic testing of short samples, and Mr. Justin Deterding and Donald Richardson of the NHMFL for eddy current inspection of long length wire. The NHMFL is supported by NSF through NSF-DMR-1157490 and 1644779, and the State of Florida.

Speaker: Dr Jun Lu (MS&T, NHMFL)

MT-26 NDT pulsed mag wire Jun Lu rev 2.pdf

Wed-Af-Po3.24 - Small Test Model Coil

Conveners: Eric Sun (Jefferson Lab, USA), Rainer Meinke (AML Superconductivity and Magnetics)

737 Wed-Af-Po3.24-01 [95]: A cable-scale experiment to predict training characteristics of superconducting magnets and explore new magnet materials

A previously commissioned system for exploring Ic pressure sensitivity in superconducting cables, the Transverse Pressure Insert, was instrumented and operated to examine signals resulting from strand motion and insulation/impregnation cracking in a fully-excited single strand embedded in an insulated and impregnated Rutherford cable stack at 4.2 K with transverse pressures up to 250 MPa and transverse applied fields up to 15 T. Voltage and acoustic signal traces from a CTD-101K impregnated cable stack were compared to those of a sample impregnated with Matrimid and some other materials. Pressure was applied and removed to simulate stresses seen during magnet operation. These experiments are in pursuit of developing smaller scale, cost, and time methods for exploring techniques and materials to decrease training in next-generation Nb3Sn magnets.

Speaker: Chris Kovacs (The Ohio State University)

Wed-Af-Po3_24-01.pdf

Wed-Af-Po3_24-01.pptx

738 Wed-Af-Po3.24-02 [96]: Design, Construction and Test of a Double-Pancake Coil wound with Kilometer Long REBCO tape

Motivated by our previous works, 26.4-T 35-mm and 18-T 74-mm ultra-high field no-insulation (NI) stand-alone magnets wound with 2G REBCO, we recently embarked on a new project to develop a 35-T NI REBCO standalone magnet. We published a design of a 35-T 40-mm winding bore magnet in 2017. Owing to the large average current density of the magnet (365 A/mm2), the magnet became highly compact; the winding outer diameter was 222 mm, while the overall winding height was 628 mm. It consisted of a stack of 52 double pancake (DP) coils and each 1500-turn DP coil requires ~600 m long REBCO tapes. As a part of the project, we fabricated and tested a single DP coil wound with a kilometer long REBCO tape to investigate manufacturing details. In this paper, we present design and construction details of the test coil, and test results in a bath of liquid nitrogen at 77 K and in conduction-cooling at 20 K.

Keywords: NI winding, REBCO tape, superconducting magnet, ultra-high field
Category: G09 - Small Test and Model Coils

Acknowledgement
This work was supported by the Korea Basic Science Institute (KBSI) grant D39611. It was also partly supported by the National Research Foundation of Korea as a part of Mid-Career Research Program (No. 2018R1A2B3009249).

Speaker: Mr Jaemin Kim (Seoul National University)

739 Wed-Af-Po3.24-03 [97]: Design and Development of a High-Frequency Magnet Prototype for Magnetic Hyperthermia Applications

The objective of this work is to discuss the engineering feasibility of high-frequency magnets for the magnetic hyperthermia cancer therapy. For effective induction heating properties of cancer therapy, the target specifications of the high-frequency magnet system are 0.06 T of the peak magnetic flux density with 200 kHz of the operating frequency at the center of used space. The operating time of the system requires 300 seconds. In order to investigate the most optimal design of high-frequency magnet system for magnetic hyperthermia, the authors carry out the design of a small sized high-frequency magnet prototype based on magnetic circuit theorem. In the prototype design, a ferrite core length is limited to 1 m, and copper Litz wires are used for the coil windings. In order to compensate the self-inductance of the magnet, the power supply system requires series resonance circuits using capacitor banks which are directly connected to the coil windings. SiC-MOSFETs will be the feasible solutions for the 200-kHz class high-frequency inverter. The magnet prototype is composed of 16 sets of 5-turns coils and will obtain the target magnetic with an operating current of 65-A. The Litz wires consist of 1800*3 strands is used for the coil windings The diameter of each strand is 0.05 mm. However, from the results of the impedance measurements, the prototype has 2 mH of the self-inductance which value is higher than the designed value. If the magnet is operated with 65-A and 200 kHz, the voltage between each coil winding becomes 10.2 kV. In this case, 5.1 nF of the capacitor banks are required for the series resonance circuit. Addition to this, the resistance of the coil windings is 10 ohm. Therefore, in order to reduce the impedance, further optimization of the magnet design and the Litz wire conductor design is now in progress. In this paper, the authors summarize the final design of the magnet prototype including the conductor design, the cooling method and the capacitor banks.

Speaker: Prof. Shinichi Nomura (Meiji University)

Poster_Wed-Af-Po3_24-03_[97]_ Nomura_Xu_MeijiUniv.pdf

740 Wed-Af-Po3.24-04 [98]: Design and research of a REBCO plate-stacked coil

High-temperature superconducting magnet technology are developing fast, especially using REBCO tapes. This paper present a new design of a HTS coil. The coil is made of stacked REBCO plates and operates with power supply, which works like a conventional resistive coil. The structure design and construction details was then described herein. The advantage of this design is its low inductance which make it excited fast. Finite element method was used to analyze the stress distribution and thermal stability of the coil. We fabricated a model coil by this design and test its performance and feasibility at 77 K. The critical current Ic of the REBCO tapes we used to fabricated the model was measured at 77 K, and was compared to the critical current of the model coil. We listed our future work plan to improve our design. The design has potential application in future LN2 magnets. It is also afford a new idea to make high field magnets cooled by 4.5 K supercritical helium flow or conduction cooled by cryocooler.

Speakers: Guihong Zou (high magnetic field laboratory of Chinese Academy of Sciences), Donghui Jiang

741 Wed-Af-Po3.24-05 [99]: Manufacture and performance test of High Temperature Superconducting Coils for 3.5T Magnetic Separation

With manufacturing process development of the high temperature superconducting (HTS) tape, the hundreds meters HTS tapes are applied in industry, especially beneficiation. It cannot effectively improve the work efficiency of the material purification and separation, but also solve the problem that some weak magnetic materials are difficult to separate due to the so high magnetic intensity and gradient. A 3.5T HTS magnetic separation facility was manufactured in China. This paper focuses on the manufacturing process and performance test of coils. The method of axial movement across the layer during winding first radial turn was adopted to reduce some mechanical deformation damage; the resistance value of new type coil connected joints was lower than 1μΩ and it made the magnet assembly work convenient, reliable and efficient in the non-consideration of the location of coils leads; the degradation of coils critical current did hardly happen by the way of the specific solidified treatment before and after solidification. The installation and shakedown test of coils was carried out in the operation condition. As it turned out, the center magnetic field could reach 3.57T and the center axis uniformity of the magnetic field was more than 95% in the range of ±100mm from the mid-plane. Meanwhile, it meant that the magnet manufacture technology was verified and could be applied on other similar magnet in future.

Speakers: Huajun Liu (Chinese Academy of Sciences), Liang Guo

mt 26 POSTER(GUO Liang).pdf

742 Wed-Af-Po3.24-06 [100]: Design and Test a ReBCO Conduction-Cooled Solenoid Magnet without Insulation

Abstract: A laboratory solenoid magnet was designed and tested in this paper to explore the feasibility of ReBCO tapes applied to detector magnet technology. The magnet consists of several double pancake coils, which adopted to No-insulation winding method. The outer and inner radius were 240 mm and 150 mm, respectively. We conducted a series of experiments on the prototype to investigate the properties of the magnet at 20 K. The magnet adopted a conduction-cooled method by a GM cryocooler. The critical current and the central operating magnetic field were measured in this test.
Key words: solenoid magnet, ReBCO, conduction-cooled, no-insulation

Speakers: Dr Xuyang Liu (IHEP), Mr Feipeng Ning (IHEP)

MT26 poster.pdf

743 Wed-Af-Po3.24-07 [101]: Electrical insulation testing for CFETR CS model coil

The Central Solenoid (CS) model coil, which is responsible for developing and verifying the larger-scale superconducting magnet technology of China Fusion Engineering Test Reactor (CFETR), has been designed and is currently being manufactured at ASIPP. In case of an emergency shut-down like in succession of a quench, the voltage across the coil may rise to about 2.5kV. Therefore, the coil have to be provided with a reliable electrical insulation. The electrical insulation systems of the CS model coil consist of turn, layer, and ground insulation. In order to verify the insulation performance, the insulation electrical performance tests are carried out at different stages of the manufacturing process. Test content includes inter-turn voltage withstand test, AC and DC high voltage test, and insulation resistance test. This paper gives the description of the electrical insulation testing for CS model coil. The test method and test process for each test are introduced. The test results are analyzed to determine whether the requirements are met.

Speaker: Dr Ma Yuanyuan (Institute of Plasma Physics, Chinese Academy of Sciences)

744 Wed-Af-Po3.24-08 [102]: Reliability evaluation procedure of REBCO coated conductor tapes based on mechanical and electro-mechanical properties obtained by uniaxial tension and cyclic tests at 77 K

In the HTS superconducting magnet application fields like motors, generators and SMES, 2G coated conductor (CC) tapes will be subjected to alternating stress or strain during manufacturing and operation. The repeated load affects the mechanical integrity and eventually the electrical transport property of CC tapes. In the design of coils and magnets under magnetic fields, both the yield strength obtained by a quasi-static uniaxial tensile test under the use environment (temperature and magnetic field) of 2G CC tapes and the irreversible stress limit obtained by the electromechanical property evaluation test considering the Ic degradation behavior have been mainly used. Selection of 2G CC tapes for superconducting coils is usually based on these values. On the other hand, considering the operating life of superconducting coils and magnets such as 30 years, the fatigue life will be 105~106 cycles. Based on this condition, the mechanical fatigue limit from the S-N curves obtained by the high cycle fatigue test of CC tapes will be determined. Meanwhile, it is necessary to carry out the electromechanical characteristic fatigue test to evaluate the Ic degradation behavior induced by the repetition of a specified stress amplitude expected during operation. This makes it possible to determine the electromechanical fatigue limit of the CC tapes. The establishment of mechanical and electromechanical properties through a series of uniaxial tensile and fatigue tests is necessary to evaluate the reliability of CC tapes and to ensure the durability of the application devices. In this study, we introduce the procedure for evaluating reliability of 2G CC tapes using characteristic limit values obtained through a series of mechanical and electromechanical properties evaluation tests.
This research was supported by the Korea Electric Power Corporation. (Grant number: R18XA03). This work was also supported by a grant from National Research Foundation of Korea (NRF-2017-001901) funded by the Ministry of Science, ICT and Future Planning (MSIP), Republic of Korea.

Speaker: Hyung-Seop Shin (Andong National University)

MT26_Poster_Reliability Evaluation Procedure of REBCO CC tape_final.pdf

745 Wed-Af-Po3.24-09 [103]: Composite Mechanical Properties of Coils Made With Nickel-Alloy Laminated Bi-2223 Conductors

High-temperature superconducting magnet coils made with Sumitomo Type HT-NX are complex composite structures composed of Bi-2223 conductor filaments, silver matrix, solder, nickel-alloy laminations, polymer insulation, and epoxy or wax. The mechanical properties of these composites are required inputs to a correct stress analysis. Mechanical test specimens composed of several layers of insulated conductor are prepared by cutting to length, stacking and epoxy impregnation. Mechanical tests are performed in liquid nitrogen and liquid helium. Orthotropic elastic properties are found from tensile strain measurements in the conductor longitudinal, or coil hoop, direction and from compressive strain measurements in the conductor transverse, or coil radial and axial directions. Thermal contraction measurements are made as the specimens are cooled down. Test results are compared with rule-of-mixtures and finite element models.

Speaker: William Marshall (National High Magnetic Field Laboratory)

Wed-Af-Po3.24-09 Marshall.pdf

746 Wed-Af-Po3.24-10 [104]: An Experimental Study on “Defect-irrelevant” Behavior of No-insulation REBCO Pancake Coil in Conduction-Cooling Operation

Previously we reported the “Defect-irrelevant” behavior of a no-insulation (NI) high temperature superconductor (HTS) pancake coil in 2016. The test coil was wound with REBCO tapes having multiple “defects” and tested in a bath of liquid nitrogen at 77 K. Coil terminal voltages and magnetic constant of the test coil are essentially identical to those of its “healthy (defect-free)” counterpart in steady-state operation below the critical current, which demonstrated a potential of the defect-irrelevant-winding (DIW) approach to build an NI magnet with a substantially reduced cost. Here we report, as a continuation to our previous study, test results of a “DIW” REBCO pancake coil operated in a conduction-cooling environment below 77 K. Our primary goal is to demonstrate the DIW approach for mid-scale industrial applications of which typical magnetic field requirements range 1 – 5 T at an operating temperature ranged 30 – 50 K. Charging tests were performed and the results were analyzed by use of both lumped and distributed models.

Acknowledgement
This work was supported by the National Research Foundation of Korea as a part of Mid-Career Research Program (No. 2018R1A2B3009249).

Speaker: Uijong Bong (Seoul National University)

MT26_Wed-Af-Po3.24-10_DIW_UB_20190919.pdf

Wed-Af-Po3.25 - MgB2 and Iron-Based

Conveners: Franco Julio Mangiarotti (CERN), Kookchae Chung (Korea Institute of Materials Science)

747 Wed-Af-Po3.25-01 [105]: Effects of carbon doping on trapped magnetic field of MgB$_{2}$ bulk prepared by in-situ hot isostatic pressing method

MgB$_{2}$ bulk magnets have been strengthen by the densification, grain refining, and chemical doping. Ti-doped MgB$_{2}$ bulk fabricated by an in-situ hot isostatic pressing (HIP) method also offered the high trapped field, B$_{\rm T}$ of 3.6 T at 13 K [1]. The carbon doping is also well known to bring about the pronounced increase of both the critical current density J$_{\rm c}$ and the irreversibility field, H$_{\rm irr}$ [2]. In this paper, we report on the effects of C-doping on the trapped field properties of MgB$_{2}$ bulks, which were prepared by the in-situ HIP method. The B$_{\rm T}$ of 2.2 T at 20 K for the pristine bulk was increased to 2.5 T for the SiC10%-doped bulk. On the other hand, the B$_{\rm T}$’s of the C10%- and B$_{4}$C10%-doped bulks were decreased to 2.0 T and 1.6 T at 20 K, respectively. However, the temperature dependence of B$_{\rm T}$ indicates that the B$_{\rm T}$ of the C10%-doped bulk exceeds that of the pristine bulk below 15 K. We discuss the doping effects of carbon on the trapped field properties of MgB$_{2}$ bulks with different carbon sources.

References
[1] T. Naito et al., Supercond. Sci. Technol., Vol. 28 (2015) 095009.
[2] S. X. Dou et al., Appl. Phys. Lett. Vol. 81 (2002) 3419.

Speaker: Tomoyuki Naito (Iwate University)

748 Wed-Af-Po3.25-02 [106]: Development of MgB2 superconductor wire and coils for AC and DC applications

Hyper Tech Research will report on progress that has been made on developing magnesium diboride superconductor wires, coils and magnets for commercialization efforts, with a specific emphasis on conduction cooled MRI and AC motor/generator applications.

Speaker: Mr Michael Tomsic (Hyper Tech Research)

749 Wed-Af-Po3.25-03 [107]: Numerical simulation of drawing process of multi-filamentary MgB2 wire

In the drawing process, a non-uniform powder distribution in the MgB2 wire along longitudinal direction can cause degradation of superconducting properties of MgB2 wire and strain hardening of sheath material. It may finally results in breakage of wire due to a stress concentration at locally deformed region in sheath materials. In this study, numerical simulation of drawing process of multi-filamentary MgB2 wire was conducted to predict densification behaviour of powder and deformation behaviour of sheath materials during the drawing process. In the simulation, powder was modelled by a modified Drucker-Prager Cap (DPC) model and commercial finite element software ABAQUS was used to implement the modified DPC model. The calibration of the material parameters for the modified DPC model was performed by extracting the data from the combination of cold isostatic pressing (CIP) and die compaction tests. The initial shape and material properties of multi-filamentary wire in the simulation was modelled based on the experimental results. The predicted density of powder and deformed shape of wire were compared with experimental results to verify simulation results.

Speaker: Mr Young-Seok Oh (Korea Institute of Materials Science)

750 Wed-Af-Po3.25-04 [108]: Performance of MgB2 Superconductor developed for high-efficiency Klystron Applications

The performance of MgB2 wire (O.D. = 0.67 mm, Length = 8 km) made for a prototype solenoid magnet for X-band (12 GHz) klystron are presented. This solenoid magnet is fabricated by using Wind & React method and is operated as a cryogen-free magnet at 20 K. In this paper, tensile- and bending-stress tolerances of the non-reacted wire and the properties (Ic-B-T, RRR and homogeneity) of the reacted wire are presented. These properties are used for designing a small test coil and the magnet for the klystron application. In addition, to realize the MgB2 coils by using React & Wind method in future, the minimum bending radius of the reacted wire is discussed.

Speaker: Dr Hideki Tanaka (Hitachi, Ltd.)

MT26 Wed-Af-Po3.25-04 Hitachi tanaka.pdf

751 Wed-Af-Po3.25-05 [109]: Fabrication of (6+1)-structure superconducting cable based on 30-core MgB2 superconducting wire

In this paper, the km-grade 30-core MgB2 superconducting wire with a diameter of 1.0mm has been prepared by conventional in-situ powder-in-tube method. The metallographic analysis results show that the 30-core MgB2 wire has very good uniformity in both transverse and longitudinal directions, and the critical current (Ic) and critical current density (Jc) reach 95 A and 2.1×105 A/cm2 at 4.2 K and 4 T, respectively. Furthermore, the (6+1)-structure MgB2 superconducting cable has also been successfully fabricated with different twist pitches (TP) by the twisted and reacted (T&R) route, which uses six pieces 30-core MgB2 wires and one copper wire in the center. The critical current (Ic) of the (6+1)-structure MgB2 superconducting cable with 50 mm TP reaches 476 A at 4.2 K and 4 T in this work.

Speaker: Mr Wang Dayou (State Key Laboratory of Solidification Processing, Northwestern Polytechnical University and Western Superconducting Technol WST Co Ltd, NELSM)

MT-MgB2 WangDayou+.pdf

752 Wed-Af-Po3.25-06 [110]: Experimental and numerical study on crack evolution of Nb barriers causing Ic deterioration in multi-filament MgB2 strands during cabling process for large-scale energy storage coils.

MgB2 strands have been highly developed commercially, providing great interest in superconducting magnetic energy storage (SMES) applications with low cost by using liquid hydrogen (LH2) as a coolant due to the higher critical temperature compared to the boiling temperature of the LH2. Therefore, the MgB2 SMES is promising device, giving us a remarkable synergy effect by combining the stabilization of fluctuated power originated from renewable energy sources and supply of hydrogen gas for developing hydrogen-based society to reduce the carbon foot print. For the applications with large stored energy, the current capacity of MgB2 conductor should be large for the compensation of the power fluctuations. In this sense, we need to fabricate large scale conductors for making SMES coils with large stored energy. Our group has been investigating the feasibility study of SMES using MgB2 indirectly cooled by liquid hydrogen. In our investigation, the deterioration in critical current of Rutherford cables has been observed. Cracks in Nb barriers became apparent by measured images of the cross sections of the deformed strands with high-resolution, X-ray source CT, which are considered to be caused by strand bending and/or dents at the strand cross over points during cabling process. To clarify the mechanism of the damage of the strands, numerical simulation based on non-linear extended FEM is also performed. The calculation showed that some overlap points in the Nb barrier covering the MgB2 powders produced by CTFF method would behave as crack-initiation during loading. The experimental and numerical approach for analyzing deteriorations in superconducting characteristics of MgB2 strands shown in this report will lead to the further development of large-scale, cost effective storage device which has great potential to increase the electric power generated by uncontrollable energy sources.

Speaker: Tsuyoshi Yagai (Sophia University)

MT26(2019)_Yagai_Wed-Af-Po3.25-06[110].pdf

753 Wed-Af-Po3.25-07 [111]: The rapid heating and quenching method for MgB2 superconducting wires with kilometer-grade length

In order to reduce the long-term annealing process and prevent excessive grain growth, we attempted to fabricate MgB2 superconducting wires by the rapid heating and quenching (RHQ) method.We have successfully synthesized kilometer-length 6+1 filamentary MgB2 wires reinforced and toughened by Nb/Cu composite with in-situ powder-in-tube method, and for the first time applied the rapidly heating and quenching (RHQ) to the treatment of MgB2 wires, directly realizing the superconductivity of quenched MgB2 wires as well as the improvement of workability, thus avoiding the necessary annealing program in the conventional process. The results show that the phase composition of samples is mostly MgB2 after treatment with heating current at 350A, except for a small amount of impurities. Most importantly, at 5T and 20K, the critical current density is still as high as 1.34×103A cm-2, which fully meets the requirements of practical applications.

Speaker: Yong Zhang (Southwest Jiaotong University)

754 Wed-Af-Po3.25-09 [112]: Electromechanical Properties Evaluation of Various Multifilamentary MgB2 Wires

Multifilamentary Magnesium diboride (MgB2) wires are composed of brittle compound filaments and metallic sheath with a sufficiently strong reinforced material. A strong reinforced material provides tolerable stress that increases the filament density and enhances the grain connectivity of the MgB2. However, MgB2 wires are highly attractive for various applications due to its high critical transition temperature. It is considered a promising alternative to HTS wires at a low magnetic field which is suitable for various applications, including medical resonance imaging (MRI), fault current limiters (FCL), wind power generators. This study focused on the evaluation of the Ic-strain behavior of various kinds of multifilamentary MgB2 wires with different mechanical reinforcements. Despite having brittle superconducting filaments, the mechanical reinforcements in MgB2 wires compensate for this weakness which also enhances the electromechanical properties of the wire. In this study, the critical limits of Ic degradation in MgB2 wires were evaluated under uniaxial tension at a magnetic field and temperature, 2 T and 20 K, respectively. The influence of the different reinforcement materials was investigated. The mechanical properties were also determined at RT and 77 K and self-field.

This work was supported by a grant from the National Research Foundation of Korea (NRF-2017-001901) funded by the Ministry of Science and ICT (MSIT), Republic of Korea. This research was also supported by the Korea Electric Power Corporation. (Grant number: R18XA03).

Speaker: Mr Mark Angelo Diaz (Andong National University)

Poster-MgB2 wires.pdf

755 Wed-Af-Po3.25-10 [113]: Enhancement of high field Jc of MgB2 superconductors by carbon doping through coating process

The Tc of MgB2 superconductors, 39 K, is higher than low temperature superconductors such as NbTi and Nb3Sn, which can allow operating at 20 K by using refrigeration system without the consumption of expensive L-He. In addition to the high Tc, MgB2 has the advantages of longer coherence lengths and the lower anisotropy effect, when compared with the high temperature superconductors, and the low cost of the starting materials. These features of MgB2 superconductor could be promising for adoption of industrial superconducting applications. However, rapid decrease in critical current density (Jc) as applied magnetic fields due to relatively low upper critical field (Hc2) and weak flux pinning force leads to a restriction of practical applications. To overcome the problem, many researchers have been studied and proved carbon doping by direct addition or chemical doping approach to be effective to improve field dependence of critical current density.
In this study, therefore, we have doped carbon containing organic matter with the different doping level by coating process, which is the ease of scale-up production, and analyzed the presence of organic matter and carbon on the precursor particles. In addition, changes in microstructure of polycrystalline MgB2 induced by disorder of lattice, which is created by partial substitution of carbon atoms into boron site, were confirmed by results of broadening of FWHM of MgB2 in-plane and reduction of a-axis lattice constant. Also, superconducting properties, critical transition temperature and critical current density, were measured both by transport measurement and magnetization measurement using PPMS under different temperature and magnetic fields.

Speaker: Mr Jang Sehoon (KAT)

756 Wed-Af-Po3.25-11 [114]: Influence of chemical treatment of the raw precursors for the MgB2 superconducting applications

For the high performance of the wires, cables, and further to the various magnet applications of MgB2 superconducting materials, the important issues have been addressed on the raw precursors of their purity, relative sizes, crystallinity, and the surface conditions including MgO and B2O3 impurities. Since in situ MgB2 superconducting wires have been fabricated using the reaction of Mg and B precursors, which were contaminated inevitably from the exposure to air during the fabrication process.
In this work, B2O3 impurities can be thoroughly removed and oxygen contents are much reduced through the chemical treatment conducted at room temperature, which is more effective compared to the thermal reduction process at higher temperature of 950oC for 48 hours. It was found that Tc values are even increased and high-field Jc at both 5 & 20 K were all enhanced with the common solvents like ethanol, methanol, acetone, and even water. In addition, it is worth mentioning that the Jc at low-fields are also enhanced when the boron precursor are treated chemically with the solvents of ethanol and acetone than that of pure MgB2

Speaker: Dr Kookchae Chung (Korea Institute of Materials Science)

757 Wed-Af-Po3.25-12 [115]: Electro-mechanical properties of multifilamentary Ba0.6K0.4Fe2As2 tapes

Iron-based superconductors (IBS) are attractive for high-field applications due to the good performances including high upper critical field and low anisotropy. This work describes electro-mechanical properties of the silver-sheathed multifilamentary Ba0.6K0.4Fe2As2 (Ba-122) tape. This tape was fabricated by the ex-situ powder-in-tube (PIT) method and the number of filaments is 7. In order to know well the integrated properties, serial measurements have been done on the tape samples at Institute of Plasma Physics, Chinese academy of Sciences (ASIPP). The stress-strain curves were obtained for the free-standing Ba-122 sample at 4.2 K and critical currents have been simultaneously measured without applied magnetic field. The minimum bending radius, which is defined as the minimum radius for the bending sample with no degradation on critical current, has been measured. Combining the critical current results as function of axial strain using the so called U-spring testing device and thermo expansion properties for the based materials, the electro-mechanical properties have been analyzed for the 7-filamentary tape. Besides, the critical current characteristics as function of magnetic field B and temperature T for the tape have been measured and analyzed.

Speakers: Prof. Liu Fang (Institute of Plasma Physics, Chinese academy of Sciences, Hefei, China), Prof. Huajun Liu (Institute of Plasma Physics, Chinese academy of Sciences, Hefei 230031, China), Prof. Qin Jinggang

MT26 tianchao.pptx

758 Wed-Af-Po3.25-13 [116]: Mechanical Property of Composite MgB2 Superconducting Wires

Composite MgB2 wires have been now commercialized by a few industries in the world. In order to use them for applications, it is necessary to evaluate their mechanical property together with critical current and its stress / strain dependence. In the present study, the mechanical properties of three kinds of commercialized MgB2 wires were mainly evaluated. Their observed Young’s moduli coincided with the calculated values.

Speaker: Prof. Kozo Osamura (Research Institute for Applied Science)

Wed-Af-Or13 - High Field HTS/Hybrid Magnets for Accelerators

Conveners: Dr Tengming Shen (LBNL), Tiina Salmi (Tampere University of Technology, Finland)

759 Wed-Af-Or13-01 [Invited]: Ac loss and shielding-current-induced field in a coated-conductor test magnet for accelerator applications under repeated excitations

Ac losses and shielding currents affecting field qualities in coated conductors are concerns in accelerator magnets which must be excited repeatedly. We carried out repeated excitation experiments of a test magnet for accelerator applications of coated conductors. The magnet consists of a pair of 4-stacked racetrack coils with iron return yoke at low temperature region. It can generate 2.4 T of dipole magnetic field at its room temperature beam duct with its rated current of 200 A, and the maximum magnetic field to which the coated conductor is exposed is about 4 T.
At first, we controlled the coil temperature at 18 K, and, then, the magnet was excited repeatedly using a bipolar power supply with a saw-tooth waveform: the magnetic field was ramped up to 4 T at the conductor in 120 s and down to 0 T in 120 s. The excitation time was limited by the output voltage of the power supply. During seven times of ramping up and down, the coil temperature was controlled stably at 18 K. We successfully ramped up in 40 s once using another power supply, whose output voltage is higher but not bipolar. Next, we examined the influence of shielding current on the field quality at the steps during ramping down, where the current was hold constant. Such steps, at which constant and reproducible magnetic fields must be generated, are required in magnets for carbon gantries. In the initial 3 s of an entire step whose duration is 10 s, some field change caused by the decay of the shield current was observed, but, in the last 7 s, the relative field change was less than 0.01%. The difference between the repeated excitation was less than 0.01% as well. These values are good enough for the applications to carbon gantries.

This work was supported in part by the JSPS KAKENHI Grant Number 16H02326 and in part by the JST under the S-Innovation Program.

Speaker: Prof. Naoyuki Amemiya (Kyoto University)

760 Wed-Af-Or13-02 [Invited]: New Approach and Test Facility for High Field Accelerator Magnets R&D

The traditional approach for developing high field magnet technology has been to build a new magnet with some variations in design parameters or in material. Building a high field magnet is time consuming and expensive. This limits the development and demonstration of a new design or technology and/or forces several changes to be made at the same time which limits the clear interpretation of the results. To overcome this limitation, BNL built and successfully tested a 10 T Nb3Sn dipole DCC017 with large enough open or clear space (31 mm wide and 338 mm high) so that a pair of racetrack coils could be inserted into this opening without disassembling the magnet. The motivation behind this design was to develop a program where the new coils (with a large range in width and height accommodated) would reside in a high field region in contact with the existing coils (just as any other magnet coils) and thus become an integral part of the magnet. This approach, therefore, makes each insert coil a new magnet test, but at a much “lower cost” and in a much “shorter turn-around time”. This brings a paradigm shift from the conventional R&D approach and should encourage development and testing of innovative and so called, “high-risk, high reward” designs and technologies, as well as facilitate systematic studies of various coil parameters that requires a series of tests but were impractical because of the associated budget and time. The approach was successfully tested when the new HTS insert coils were installed and tested with the existing Nb3Sn coils to demonstrate an HTS/LTS hybrid dipole. The magnet and the facility are now becoming available for a wider use as a part of the US Magnet Development Program.

• This work was supported by Brookhaven Science Associates, LLC under contract No. DE-SC0012704, with the U.S. Department of Energy.

Speaker: Ramesh Gupta (BNL)

wed-AfOr13-02.pdf

wed-AfOr13-02.pptx

761 Wed-Af-Or13-03: Performance, diagnostic, and quench measurements of a dipole composed of two racetrack coils wound with high temperature superconducting Bi-2212 Rutherford cable

In order to address the needs of next generation particle accelerators, high $J_E$ ($>1000$ $A/mm$$^2$ at $5$ $T$ [1], [2]) HTS Bi-2212, with application of novel quench detection and protection methods is utilized in sub-scale accelerator magnets. A series of racetrack coils (RC 1-6) with the same geometry have demonstrated conductor improvements resulting in a factor of four increase in quench currents, as well as operational advantages of Bi-2212 Rutherford cables including lack of training and predictable quench behavior[3]. Demonstrating all of the key aspects of accelerator technology, a $5.6$ $T$ ($6.8$ $kA$) sub-scale common-coil magnet will be assembled from two larger LBNL racetrack coils (RC7 & RC8) made with twisted strand cables and an iron-yoke/bladder-and-key pre-loading method. We expect to reach at least $85\%$ of short sample load-line critical current, and are optimistic for more given recent Bi-2212 powder performance. The magnet includes acoustic quench detection instrumentation and will be monitored for capacitance changes during operation and quench. The inclusion of current taps between racetrack layers allows for a comparison of Coupling-Loss Induced Quench (CLIQ) protection configurations. The status of this program including coil fabrication, assembly, test results, and quench analysis will be presented.
[1] J. Jiang, “High performance Bi-2212 wires made with recent powders,” presented at the ASC 2018, Seattle, Wa, 01-Nov-2018.
[2] K. Zhang et al., “Tripled critical current in racetrack coils made of Bi-2212 ...,” Supercond. Sci. Technol., vol. 31, no. 10, p. 105009, Sep. 2018.
[3] T. Shen et al., “Stable, predictable operation of racetrack coils made of high-temperature superconducting Bi-2212 ...,” arXiv:1808.02864 [cond-mat.supr-con], Aug. 2018.

Acknowledgement: This work is funded by the DOE OHEP under the framework of the the U.S. Magnet Development Program. The NHMFL is funded by the NSF (Award No. DMR-1157490), the DOE (Award No. 227011-520-032288), and by the State of Florida. A portion of this work was funded by the U.S. DOE-WDTS-SCGSR program administered by the ORISE for the DOE under contract number DE-SC0014664.

Speaker: Daniel S. Davis (Applied Superconductivity Center, National High Magnetic Field Laboratory, Florida State University)

MT26_DSD_Racetrack_Indico.pptx

762 Wed-Af-Or13-04: Development of REBCO dipole magnets using CORC® wires

In collaboration with Advanced Conductor Technologies, the U.S. National Magnet Development Program is developing REBCO magnets with a goal of generating 5 T dipole fields. We have built several subscale magnets based on the Canted-Cos-Theta (CCT) concept using commercial REBCO Conductor on Round Core (CORC®) wires. The latest magnet C2 has four layers and a designed dipole field of 3 T in an aperture of 70 mm. It is wound with 80 m long 30-tape CORC® wires based on REBCO tapes with a 30-micron thick substrate produced by SuperPower Inc. The details of magnet fabrication are presented, including the fabrication of metal mandrels and support of conductors with Stycast. We report on the transport current performance and field generation measured at 77 and 4.2 K, and compare to expected values. The C2 CORC® CCT dipole magnet provided an important step towards 20 T hybrid dipole magnets for future circular colliders. The magnet fabrication and performance also provided effective feedback on the optimization of CORC® wires that can in turn improve the magnet performance.

Speaker: Xiaorong Wang (Lawrence Berkeley National Laboratory)

Wed_Af_Or13_04_wang_indico.pdf

763 Wed-Af-Or13-05: Integration for testing HTS Feather M2 in the FRESCA2 magnet

In 2018, FRESCA2 dipole magnet, developed within a collaboration between CEA Saclay and CERN to provide a background field for tests of cables and small coils, reached a field of 14.6 T. This represents a new world record field for dipole magnets with a clear aperture. As a continuity of the European project EUCARD-2, CERN aims at exploring accelerator magnet technology up to a 20 T operating field level. For that aim, Feather-M2.3-4 magnet utilizing REBCO Roebel cable is inserted in FRESCA2 in order to reach a higher field.
The integrated design has to be capable to deal with several challenges as the electromagnetic forces, generated in the coils of the insert magnet. The stiff external tube, made of 3D printed Ni-base alloy, of Feather-M2.3-4 is specifically designed to deal with these forces. The tube has a different thermal contraction with respect to the inner pole of FRESCA2 what can provoke mechanical interference at 4.2 K. As a result, the thickness of the shell of Feather-M2 needs to be maximized to maximize mechanical stiffness of the Feather M2, while simultaneously enabling the integration with FRESCA2 without interference. The effects of a misalignment, both radial and axial, on the stresses in both magnets are studied by using Finite Element Analysis (FEA).
The field, generated by Feather-M2.3-4, changes the field shape generated by FRESCA2. A field quality study regarding integration is presented.

Speaker: Douglas Martins Araujo (CERN)

MT-26_MARTINS_ARAUJO_Integration_25092019.pdf

MT-26_MARTINS_ARAUJO_Integration_25092019.pptx

764 Wed-Af-Or13-06: Comparison between measurements and calculations of shielding-current-induced field in a small dipole magnet wound with coated conductors

Shielding-current-induced fields (SCIFs) in magnets wound with coated conductors are one of the most serious problems for application. SCIFs cause changing of magnitude of magnetic field, error field components, and drift of magnetic field during when transport current is constant. Especially, because magnets for accelerator systems are sometimes required to generate precise magnetic field with different load ratio during repeated ramping up and down, behavior of the SCIFs in the magnets is difficult to predict. Therefore, in order to understand behavior of SCIFs in magnets for accelerator systems, comparison between measurements of SCIFs with high precision and calculations of SCIFs by precise electromagnetic field analyses is quite important.
We conduct magnetic field measurements for a small dipole magnet wound with coated conductors. The magnet is composed of four racetrack coils. Number of turns, length of straight section, and inner radius of each racetrack coil are 110, 250 mm, and 48 mm, respectively. Typical operation temperature is 20 K, and designed magnetic flux density at the center of the magnet is about 500 mT with 200 A. We measure the field quality of the small dipole magnet by rotating pick-up coil method which is able to directly measure the multipole components of the magnetic field. Current profiles are decided based on typical operation pattern of magnets in the rotating gantry of HIMAC.
Also we conduct electromagnetic field analyses in order to calculate the SCIFs in various current profiles of the magnets. In the electromagnetic field analyses, the magnet is modelled considering its exact three-dimensional geometry. Because the magnet is composed of the four racetrack coils with different coated conductors, electric field E-current density J characteristics of the conductors are formulated based on short sample measurements of them and used in the simulations. We study how shielding currents distribute in the racetrack coils and how shielding-current-induced fields change with different load ratio of the magnet.

This work was supported in part by JSPS KAKENHI Grant Number 16H02326.

Speaker: Dr Yusuke Sogabe (Kyoto University)

Wed-Af-Or13-06_Sogabe_uploaded.pptx

Wed-Af-Or14 - Novel Wire Processes and Development - in Memoriam of Prof. Kyoji Tachikawa

Conveners: Charlie Sanabria (Commonwealth Fusion Systems), Prof. Matthew C. Jewell (University of Wisconsin - Eau Claire)

765 Wed-Af-Or14-01: Memorial

766 Wed-Af-Or14-02: Reduced strain/stress sensitivity of the critical current of Nb3Sn conductors

It was found that arranging filaments in a multifilament Nb3Sn conductor under a specific angle or twist pitch length, the strain sensitivity of the critical current can be removed. The physical reason is that at such an angle the distortion of the Nb3Sn crystallographic unit cell, which is responsible for the reduction of the critical current under strain, is zero and independent of the applied uniaxial strain/stress. This is the result of a study of the Nb3Sn unit cell of Nb3Sn conductors under different axial strains carried out at the European Synchrotron Radiation Facility (ESRF) at Grenoble and modelling the distortion as a function of applied strain and angle with respect to the wire axis. In the following a Nb3Sn multifilamentary wire (OD = 1.45 mm) with different twist pitch lengths down to 5 mm were manufactured by Bruker EAS and the critical current versus strain behaviour measured at 19 T @ 4.2 K (University of Geneva). The wire with 5 mm twist pitch shows the appearance of a plateau between 0.1% and 0.6% applied strain with an almost constant critical current, as predicted by modelling. Wires with longer twist pitch length behave as usual and as known from literature. It remains the challenge for wire manufacturers to obtain short twist pitch lengths without damaging filaments.

Speaker: Dr Bernd Seeber (University of Geneva)

SEEBER-MT26-NB3SN-190919.pdf

767 Wed-Af-Or14-03: Three-fold improvement in layer critical current density in Nb₃Sn wires by using Hf addition

After over 50 years of application, Nb₃Sn remains by far the most economical superconductor for magnetic fields beyond the reach of Nb-Ti but new challenges such as the Future Circular Collider, FCC, require critical current density (Jc) values well-beyond what is possible with available commercial Nb₃Sn wire. Furthermore, future high field magnets will also require higher Jc margins to allow for the introduction of additional stabilizer and for structural elements to overcome the very high Lorentz forces. To meet the Jc challenge we have achieved a significant performance improvement by introducing Hf and other additions to the starting Nb alloy, in designs that can be adapted to existing Nb₃Sn commercial strands. This approach can be realized more readily in internal Sn strands than previous attempts that have used internal oxidation compatible only with a PIT design. In our prototype Hf addition wires, based on standard high-field Nb-Ta alloy, we can obtain Nb₃Sn layer Jc (16 T, 4.2 K) values of over 3700 A/mm² which, if extrapolated to an RRP conductor design, corresponds to a non-Cu Jc (16 T, 4.2 K) of over 2200 A/mm² (almost 50% higher than the preliminary FCC target specification of 1500 A/mm²). The Hf-addition wire has three times the layer Jc of our Nb-Ta alloyed control samples (no addition). If this level of increase can also be applied to low-hysteresis loss conductors, such as those developed for ITER, then a wide range of applications will be impacted, such as future fusion devices and NMR magnets. By systematically exploring the impact of different alloying elements, we demonstrate the potential for further improvements in properties.

Acknowledgments: This work was supported by the U.S. Department of Energy under Award DE-SC0012083 and CERN under Framework Collaboration Agreement KN2713. A portion of this work was performed at the National High Magnetic Field Laboratory, which is supported by NSF Cooperative Agreement DMR-1644779 and the State of Florida.

Speaker: Dr Peter Lee (Applied Superconductivity Center, National High Field Magnet Laboratory, Florida State University)

768 Wed-Af-Or14-04: Wire and Cable Characterization of Nb3Sn Conductor with High Heat Capacity

Accelerator magnets made of state-of-the-art Nb3Sn strands unveil relatively long training. This could be due to the low stability of high-Jc Nb3Sn wires to flux jumping provoked by mechanical perturbations in the magnet coils and/or by epoxy cracking. Conductor stability to flux jumps can be increased by reducing the superconductor filaments size while maintaining low resistivity of the copper matrix, and by increasing the composite specific heat cp, which increases the conductor enthalpy margin. A considerable increase in stability of Nb3Sn multifilamentary composite wires made with the Powder-in-Tube process with gadolinium oxide Gd2O3 and Cu powders in Cu tubes replacing a few of the Nb tubes had been demonstrated previously. Within a collaboration with Bruker EAS and Bruker OST, FNAL developed a high-Jc Rod Restack Process (RRP) composite wire with 36 superconducting subelements, 24 high-cp Cu tubes with Gd2O3 and Cu powders over 61 total hexagonal subelements. To study the response of this new billet to plastic deformation, round wires were flat-rolled to various deformation values. This method imparts a homogeneous deformation along a wire. Then Rutherford cable was fabricated to study the effect of uneven and localized plastic deformation on the wire. Critical current Ic, average critical current density JA, minimal stability current IS , minimal quench energy, MQE, and matrix RRR were measured for flat-rolled and extracted strands, and compared with round wire data.

Speaker: Emanuela Barzi (Fermilab)

Wed-Af-Or14-04_Barzi.pdf

Wed-Af-Or14-04_Barzi.pptx

769 Wed-Af-Or14-05: Evolution of Nano-particles Doping in Nb3Sn Wires

The development of Nb3Sn wires doped with artificial pinning centres (APC) from binary to ternary compounds is reported. ZrO2-doped tube-type (TT) and powder-in-tube (PIT) were manufactured by Hyper Tech Research Inc. with the aim of reaching the FCC requirements (non-Cu Jc=1500 A mm-2 at 16T and 4.2K). Short pieces of the wires were characterized by means of SQUID magnetometry in order to evaluate their critical temperature and critical current. The upper critical field was determined via resistivity measurements in a 17 T cryostat. The layer-Jc (at 12 T and 4,2 K) is significantly higher than in commercial state-of-the-art wires (Ta or Ti-doped), which can be explained by a grain refinement, as inferred from by high-resolution transmission electron microscopy (TEM) and transmission Kikuchi diffraction (TKD) analysis. An average grain size of 63 nm (in the best binary sample) was derived, resulting in a high grain boundary density which increases the pinning force. In this sense, a pinning force scaling analysis was carried out, showing a shift of the peak position close to a reduced field of 0.3. Scanning Hall probe microscopy (SHPM) was used to map the field above the wires cross-section in the Meissner and remnant-field state: a magnetization map of the individual sub-elements was obtained from the latter, and the critical currents were calculated from the field profiles at different temperatures. Meissner-state scans were used to assess the effective A-15 superconducting cross-section of the sub-elements together with the radial distribution of the transition temperature. These local properties were related to SEM-EDX data, which assessed stoichiometry variations.

Aknowledgments: This Marie Sklodowska-Curie Action (MSCA) Innovative Training Networks (ITN) receives funding from the European Union’s H2020 Framework Programme under grant agreement no. 764879.

Speaker: Mr Mattia Ortino (TU Wien)

MattiaOrtino_MT26_.pdf

MattiaOrtino_MT26_.pptx

770 Wed-Af-Or14-06: The effect of transverse loads on Nb3Sn Rutherford cables for accelerator magnets

Rutherford cables based on high critical current density Jc Nb3Sn wires are considered for next generation accelerator dipole and quadrupole magnets. The operating magnetic field of these magnets is expected to be significantly larger than that of the Nb3Sn magnets developed for the High Luminosity – Large Hadron Collider (HL-LHC) project, which is about 12 T. In particular the present designs for the main dipoles of the Future Circular Collider project consider an operating field of 16 T. At these large fields, the Lorentz forces induce a transverse load on the Rutherford cable that can exceed 150 MPa. Experimental results at CERN, Twente and Geneva Universities have recently shown that with transverse load of 150 MPa, the reversible reduction of the critical current is significant (more than 30 % at 1.9 K and 16 T) and it has to be taken into account to design the magnets and properly derive their enthalpy margins. CERN also developed a scaling law for describing the dependence of the Nb3Sn Jc on its strain state; this scaling law, coupled with finite element models, allowed to successfully simulate the reversible reduction of the Jc once a transverse load is applied on the conductor. In this paper, an overview of the present understanding of these phenomena is presented and the impact that these discoveries will have on the design of next generation Nb3Sn accelerator magnets is discussed.

Speaker: Bernardo Bordini (CERN)

771 Wed-Af-Or14-07: Recent advances in iron-based superconducting wires for high-field applications

Iron-based superconductors (IBS), especially 122 type, are very promising candidates for high-field applications because of its ultrahigh Hc2 > 70 T at 20 K, low anisotropy ( < 2 for 122) , and ease of fabrication. Recently, thanks to the great supports from Chinese government, significant progresses on the IBS wires have been made, in terms of both Jc enhancement and practical research. In this talk, the overview of the recent progress will be provided. Firstly, the highest transport Jc values have achieved 0.15 MA/cm^2 (Ic = 437 A) at 4.2 K and 10 T in densified and textured 122 tapes. The transport Jc measured at 4.2 K under high magnetic fields of 27 T is still on the level of 55 kA/cm2. Secondly, in order to reduce costs and improve the mechanical strength, high strength stainless steel/Ag and Cu/Ag 122 composite conductors have been fabricated, with transport Jc above 50 kA/cm^2 in 10 T. For round wires, the highest Jc value reached 31 kA/cm^2 in Cu/Ag composite sheathed wires at 4.2 K and 10 T, obtained by the hot-isostatic-press technology. High-Jc 7-, 37-filament 122 wires were successfully fabricated by the PIT method. Thirdly, based on the experience of high-performance short samples and multifilamentary wires process, high performance 100-m-long multifilamentary superconducting tape has been produced using the scalable rolling process, confirming the great potential for large-scale manufacture. Finally, the latest results of the first joint between 122 IBS superconducting wires will be presented.

Speaker: Prof. Yanwei Ma (Institute of Electrical Engineering, Chinese Academy of Sciences)

772 Wed-Af-Or14-08: Fabrication and Test of ϕ35 mm Iron-Based Superconductor Coils

Iron-based superconductor (IBS) is expected to be the next generation high temperature superconductor with their potential good properties for the high-field application. This study focus on exploration of the characteristics of IBS coils at high field and development of the IBS coil fabrication technology. A series of ϕ35 mm IBS coils including single pancake (SPC) and double pancakes (DPC) were designed and winded with the 7-filamentary Ba1-xKxFe2As2 (Ba122) tape which was produced by the Institute of Electrical Engineering, Chinese Academy of Sciences (IEE-CAS). The IBS coils were divided into 3 groups according to the different fabrication processes. The tests of the IBS coils were firstly carried out at 4.2 K and 10 T background field. The highest quench current of the coils at 10 T is 68.4 A, which is about 79% of the quench current at self-field and about 90% of the critical current of the short sample at 10 T. Then, two SPCs were selected and tested at 4.2 K at 24 T. The highest quench current of the coils at 24 T is 25.6 A, which is about 39% of the quench current at self-field. The test results were presented and analyzed with respect to the different fabrication processes.

Speaker: Dr Zhan Zhang (IHEP, Chinese Academy of Sciences (CAS) )

(Oral) Fabrication and Test of ϕ35 mm Iron-Based Superconductor Coils.pdf

(Oral) Fabrication and Test of ϕ35 mm Iron-Based Superconductor Coils.pptx

Wed-Af-Or15 - Rotating Machines I

Conveners: Mr Thibault Genestier (GE Power), Timothy Haugan (U.S. Air Force Research Laboratory)

773 Wed-Af-Or15-01: Key electromagnetic characteristics of non-insulation REBCO rotor windings in machines of electrical aircraft: eddy loss and ramping delay.

High temperature superconductor (HTS) No-insulation (NI) shows a great advantage on enhanced thermal stability. It is promising to improve the stability and safety of HTS machines in electrical aircrafts. A Marie Curie project under Horizon 2020 was started to develop highly safe HTS machines based on NI technique for electrical aircraft. A 2MW HTS synchronous motor prototype was developed based on NI technique in University of Strathclyde, UK. To reduce the eddy losses and magnetization loss, the NI coils are only applied on rotor windings, and the stator windings use copper wires. Due to the absence of turn-to-turn insulation, the NI coil suffer two critical challenges in machines: eddy loss and ramping delay.
The ripple fields from stator windings can generate an eddy current on NI rotor windings. The Joule loss generated on the turn-to-turn contacts may considerably affect the efficiency of the machine, which has never been studied. The ramping delay of NI HTS coils can lead to great challenges on the performance of the HTS machine during start-up and operating station changing. This study is to elucidate these issues and validate the feasibility of NI HTS machine. First, a numerical model is developed for the electromagnetic analysis of NI HTS coils. second, the eddy loss induced by ripple fields and ramping delay are measured on a laboratory-scale NI HTS coils using calibration-free methods. Model validation are conducted by comparing the results from simulation and measurements. Then, a 2 MW HTS synchronous design is presented, the eddy loss and ramping delay of the NI rotor magnet is analysed in the machine environment, and then they are compared with that of the insulated counterpart. The distribution of eddy loss on NI rotor windings is characterized, and its influence on the efficiency and performance of the HTS motor is analysed. Measures are proposed to reduce the eddy loss and ramping delay of NI rotor winding so that they can match the requirements of the engineering applications.

Speaker: Yawei Wang (University of Bath)

774 Wed-Af-Or15-02: Presentation withdrawn

775 Wed-Af-Or15-03: Conceptual design of an HTS motor for future electric propulsion aircrafts

Electric propulsion systems are attracting much attention as a revolution in the aviation industry. The key components of this revolution are electric motors and generators. However, conventional machines are limited in their rated power, power density, and are not suitable for aircraft because of their size and weight. High-temperature superconducting (HTS) power machines have the advantages of high power density due to their high current density, high magnetic field density, and low losses, thus reducing the size and weight of the machine. This paper presents the conceptual design of an HTS motor for future electric propulsion aircrafts. A 5MW HTS motor uses superconducting wire for both DC excitation and AC winding coils. The operating temperature was estimated based on the observed magnetization curves and the Ic – B – T characteristics. Effective length, air-gap, magnetic load, power loss, and diameter of the motor were designed and analyzed through both analytical solutions and numerical simulations. As a result, the motor was able to achieve 97.5% efficiency at rated output conditions. The output density is about 15 kW/kg, 1.5 times higher than that of the conventional motor. These results can be used effectively to design HTS motors for future electric propulsion aircraft.

Speaker: Mr Dinh-Vuong Le (Changwon National University)

Wed-Af-Or15-03 - PPT - DV Le -CWNU 2019.pdf

776 Wed-Af-Or15-04: Low loss HTS stator coils for high power density superconducting motors

Future hybrid and all electric aircraft require superconducting electric motors and generators in order to most readily attain power densities above 10 kW/kg, preferably at operating temperatures of >40K. Although the rotor operates at fields of up to 5 T, because it is DC, it can be wound with HTS tapes, for example 2G, that can generate these fields at > 40 K. The stator, however, operates in AC mode, for example, 0.5 T at 200 Hz, making it problematic to use tapes due to their high losses in ac fields, requiring instead, HTS as small cross-sectioned, fine-filament wires that are cabled into low-loss transposed forms. Due the challenges of attaining low AC loss with tapes, HTS usage for stators has not been an option. Recent advances however with our high performance, strong HTS 2212 wire, now enabled development of first of their kind HTS cables with loss reducing features and configurations specifically designed for HTS stators operating at 40 K or greater. As a first step, small diameter, high current density 2212 wires have been developed with features required for low ac loss, including non merged, small sized filaments, short pitch length axial twist and increased resistance between filaments. These wires were then used to develop and build prototype high current cables, followed by fabrication of stator-type test coils that demonstrated the feasibility of building HTS stator coils with 2212. A design analysis with 2212 stator coils showed several promising options for building high power density, high efficiency all HTS motors that operate at 40 K or greater.

Speaker: Dr Alexander Otto (Solid Material Solutions, LLC)

777 Wed-Af-Or15-05: Superconducting magnetic heterostructured components for electric motor applications

Trapped magnetic flux magnets made by stacking high temperature superconducting tape portray an easy assembly with already available materials, high mechanical resistance, provided by the substrate and improved thermal stability, which enhances the trapped flux compared to bulks and allowed reaching the world record of 17.7 T [1]. The presented analysis will expand the work of Patel et al. [2] with wide superconducting tapes showing further developments in this kind of devices in order to be used as source of magnetic flux in electrical motors, substituting permanent magnets. These developments aim at increasing the trapped magnetic flux during field cooling magnetization (where pulse magnetisation was studied in our earlier research [2]), reducing the demagnetization and proposing means to decrease the leakage flux at the edges of the magnet during the operation of the machine. This is expected to be achieved by introducing new materials in between the individual tapes: active, such as other superconductors, or passive, such as ferromagnetic layers. The results of simulations using the H-formulation as well as experimental measurements will be presented in detail.

Acknowledgement:

This research is financially supported partially by the European Union’s Horizon 2020 research innovation programme under grant agreement No. 7231119 (ASuMED “Advanced Superconducting Motor Experimental Demonstrator”) and also by EPSRC grant No. EP/P000738/1 entitled “Development of superconducting composite permanent magnets for synchronous motors: an enabling technology for future electric aircraft”.

References:

[1] Patel et Al., “A trapped field of 17.7 T in a stack of high temperature superconducting tape,” Superconductor Science and Technology, 31, 9 (2018).
[2] Patel A, Hopkins S C, Glowacki B A, “Trapped fields up to 2T in a 12 mm square stack of commercial superconducting tape using pulse field magnetization”, Superconductor Science and Technology, 26, 032001 (2013).

Speaker: Dr Vicente Climente-Alarcon (ASCG - Dept. Materials Science and Metallurgy, University of Cambridge)

26MT Climente.pdf

778 Wed-Af-Or15-06: Rotor Cooling Concept for the ASuMED Superconductive Motor

The consortium of the Advanced Superconducting Motor Experimental Demonstrator (ASuMED) will develop, build and test the first fully superconductive motor for aerospace applications. The cryogenic topology of the motor is based on a dual-cryostat concept, which consists of two separate cryostats for the rotor and stator. The rotor cryostat design is particularly challenging because of the cryogenic operating temperatures, the cooling requirements and the rotating parts, which include a rotary seal. A number of alternatives based on different heat transfer mechanisms were considered. The feasibility of these options was assessed by preliminary analyses, which show that a forced convection based system is the optimal solution to achieve the required cooling power in the rotor. The forced convection cooling system is realised by the forced circulation of cooling gas (gaseous helium) in the system. This is the so-called externally controlled cooling system for the rotor. A detailed flow and heat transfer analysis shows that the system has the potential to achieve the required cooling power.

Speaker: Ana Perez (Demaco Holland BV)

Wed-Af-Or15-06-Perez.pptx

779 Wed-Af-Or15-07: Analytical and Experimental Study on a Low-Speed and High-Efficiency 1 kW Class Fully High-Temperature Superconducting Induction/Synchronous Generator

Low speed direct drive generator has been widely used in the renewable energy power generation, due to the advantage of no gearbox. Our group has studied so-called high-temperature superconducting induction/synchronous motor (HTS-ISM), which has the advantages of high efficiency, high torque density and robustness against overload. Especially, its highly efficient generation characteristics at low speed would realize the above-mentioned renewable energy system.
In this paper, a low-speed and high-efficiency fully high-temperature superconducting induction/synchronous generator (HTS-ISG) is designed and fabricated. REBCO tape is adopted for the stator winding and the squirrel-cage rotor winding. Firstly, the current transport characteristics of an YBCO tape are precisely measured and characterized as a function of temperature and magnetic field vector. Then, the open circuit characteristics and load characteristics against the rotational speed of HTS-ISG are analyzed by using the above characteristics. The results show that, when the rotational speed of the HTS-ISG is set to 500 rpm, the induced electromotive force, output power, and efficiency are, respectively, 106 V (peak), 1 kW, and 96.1%. Further, the influence of stator parameters on the current transport characteristics of HTS winding is analyzed and optimized. It is demonstrated that the stator’s toroidal winding can reduce the perpendicular components of magnetic flux density with respect to the HTS tape’s wide surface. Finally, to verify the performance of the HTS-ISG, a 1kW class HTS-ISG prototype is fabricated, and various experiments are conducted. More detailed simulation and experimental studies will be shown and discussed.

Acknowledgements:
This work was supported by JSPS KAKENHI Grant Number JP17H03218.

Speaker: Dr Liangliang Wei (Kyoto University)

Analytical Study and Fabrication of a 1 kW Class Fully High Temperature Superconducting InductionSynchronous Generator-final .pdf

Analytical Study and Fabrication of a 1 kW Class Fully High Temperature Superconducting InductionSynchronous Generator-final .pptx

780 Wed-Af-Or15-08: Superconducting magnetic bearings for a high-speed electric aircraft motor

A levitating superconducting bearing assembly is being designed, built and tested to support the rotor of a 10 kW laboratory-scale prototype of a 25,000 rpm superconducting hybrid electric aircraft motor targeting an ultimate power rating of 1 MW. To this end, we have constructed a bearing test rig enabling measurements of the levitation force and stiffness of assemblies of state-of-the-art melt-textured bulk YBa2Cu3O7 superconducting pellets and Nd2Fe14B permanent magnets under cryo-cooled (liquid cryogen free) conditions over a range of realistic potential operating temperatures. We show that commonly available materials provide sufficient levitation force to support the mass of the prototype rotor under conduction cooling across an accessible temperature range, and are scalable to the full-size machine. The experimental results are supported by finite element modelling that is validated against the experiment and used to determine the optimal relative sizes of superconductor and permanent magnet to achieve maximum levitation force under any given set of operational conditions. The stiffness of the resulting bearing assembly is naturally low, and we propose and investigate novel bearing geometries involving shaping of the superconducting bulk and magnet to increase the stiffness to a level applicable to a high-speed machine. The extension of the test rig to a dynamic setup able to investigate bearing stability and damping under high-speed rotation is described. Potential issues relating to the homogeneity of the permanent magnets and our efforts to characterise this are also discussed.

Speaker: Dr James Storey (Robinson Research Institute, Victoria University of Wellington)

Storey MT26 Upload.pdf

18:30 Banquet

Thursday 26 September

07:55 Registration Open (7:00 AM - 5:00 PM)

Plenary: Timothy Coombs (University of Cambridge)

Convener: Mathias Noe (Karlsruhe Institute of Technology)

781 Thu-Mo-PL5-01: Advances in Superconducting Rotating Machinery

In 1973 A.D. Appleton writing in the Journal Philosophical Transactions of the Royal Society in London heralded the dawn of a new age of electrical machines with the title “Superconducting Machines – a new era for the electrical power industry. This was written in the very early days of the development of Niobium Titanium and records that the world’s very first superconducting machine was a 37 kW machine built in 1966 at IRD and that a further machine rated at 2.4 MW had already been built. The paper predicts that a 500 MW machine would weigh 210 tonnes just over half of the 400 Tonnes of a conventional machine. An even larger machine at 1300 MW would have an even greater weight saving. Since then the technology has moved on, machines have been designed and built with better and better efficiencies, materials and methods have been discovered and developed. Crucially there is a very real need now for lightweight highly efficient machines. For generation, wind turbines are being developed in the MW class. For propulsion motors are being developed aimed at providing greater than 20 kW/Kg which would enable the development of wide bodied electric aircraft. This talk will report on the current state of the art in superconducting rotating machinery and the prospects for the future.

Speaker: Tim Coombs (University of Cambridge)

Thu-Mo-PL5-01-Coombs_REV.pdf

Thu-Mo-PL5-01-Coombs_REV.pptx

08:45 Coffee Break (during Poster Sessions)

Thu-Mo-Po4.01 - Associated Technology II

Conveners: Thanatheepan Balachandran (University of Illinois ), Eric Sun (Jefferson Lab, USA)

782 Thu-Mo-Po4.01-02 [1]: A uniform pressure actuator with high forming efficiency based on the pulsed magnet manufacturing technique

In this paper, a novel Uniform Pressure Actuator (UPA) is designed and analyzed based upon the manufacturing technique of pulsed magnets, which has high forming efficiency as well as high strength. The UPA is a specially designed coil for use in electromagnetic forming (EMF) process, which offers a uniform pressure distribution in flat sheet forming. To improve the strength of the coil, traditional UPAs are usually fabricated by machining copper blocks. This way makes the thick cross-section of the wire and the wide turn spacing, which lead to a decrease in the current density and the magnetic flux density, resulting in a low forming efficiency of traditional UPAs. To improve the forming efficiency, a novel UPA is designed by closely winding the thin copper conductor. And in order to solve the problem of low strength of the thin copper conductor, the manufacturing technique of pulsed magnets is introduced. Considering the flat structure characteristic of the UPA, A new process of winding composite materials in both transverse and longitudinal directions is employed. The theoretical analysis for the forming efficiency is carried out. Both the numerical and experimental techniques are used to calculate and compare the forming efficiency of UPA. After that, destructive experiment is conducted to test the coil strength. The results show that the designed UPA by the manufacturing technique of pulsed magnets has considerable strength with higher forming efficiency compared to the traditional ones.

Speaker: Prof. Xiaotao Han (Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology)

783 Thu-Mo-Po4.01-03 [2]: Pulsed magnet design and fabrication for generating background magnetic field in pulse current driven forming

Pulse current driven forming (PCDF) is a forming method that directly loads a pulse current into two parallel placed workpieces, and the mutually exclusive electromagnetic force between them causes the workpieces to be deformed. Compared with electromagnetic forming (EMF), this method can improve the current density in a low-conductivity workpiece. However, the magnetic field is low due to the lack of a forming coil, which causes the formability of the workpiece poor. In order to solve this problem, a pulsed magnet based on the PCDF process of thin titanium sheets is designed in this paper, which can provide a background magnetic field with good uniformity and high intensity. The influence of design parameters (coil size, wire size, number of turns, etc.) of several common coils (solenoidal coils, Helmholtz coils and runway coils) on the magnetic field uniformity and intensity in the forming area is analyzed by finite element method using the commercial software COMSOL. After that, the background magnetic field coil is fabricated based upon the manufacturing technique of pulsed magnets, and the PCDF experiments of thin titanium sheets are conducted. The results show that the background magnetic field magnet can increase the magnetic field intensity of the forming area by 5 times, and the magnetic field uniformity of the forming area can reach more than 95%, which greatly improves the formability of the workpiece.

Speaker: Mr Pengxin Dong (Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology)

2019MT26Poster-董芃欣.pdf

2019MT26Poster-董芃欣.pptx

784 Thu-Mo-Po4.01-04 [3]: The Design of the 30kA DCCT using in the FTPMF system

The Direct-Current Current Transformers (DCCTs), which is based on the magnetic flux compensation, are the most sophisticated instruments to measure currents. In order to achieve the precision measurement of the magnet current in the flat-top pulsed high magnetic field (FTPMF) facility, the DCCT based on magnetic modulator with the range of 30kA is developed. In the conventional high precision(<100ppm) DCCT, the architecture of power amplifiers (PA) is usually based on a class AB output stage, which is characterized by features such as low total harmonic distortion (THD) and low energy efficiency. The class D amplifiers, also called “switching amplifiers”, are very high efficiency. In order to reduce the power consumption, the PREMO Group used the class D amplifier as the PA of the DCCTs, which significantly improve the energy consumption by almost 40%. However, the measurement accuracy is only 0.2%, which can not meet the requirement of FTPMF system, due to the inherent ripple of the class D amplifiers. In this paper, we proposed using resonant circuits to filter the current ripples caused by the class D amplifiers making it possible to reduce significantly the power consumption of the current transducers without affecting their performance. Base on this scheme the DCCT using in the FTPMF system is fulfillment at the Wuhan National High Magnetic Field Center in China.

Acknowledgements：We gratefully acknowledge the financial support of the National Key research and development plan project of China (2016YFA0401703).

Speakers: Dr Shaozhe Zhang (Wuhan National High Magnetic Field Center,Huazhong University of Science and Technology), Zhenglei Wang (Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology)

Thu-Mo-Po4.01-04.pdf

785 Thu-Mo-Po4.01-05 [4]: Research on Influence of High Pulse Magnet Fault on Power Supply and Protection Strategy

High magnetic fields is a basic and indispensable research tool, which has been used in physics, medicine, biology, and other corresponding sciences as an extreme condition. Wuhan National High Magnetic Field Center has been working on the research of high pulsed magnetic field and designed the 100 Tesla system to achieve higher magnetic field. The magnet adopts a three-coil structure, which is powered by three sets of the power supply. The stress of the magnet is large and there is a large risk of damage when the magnetic field reaches a high level. In order to ensure the safe and stable operation of the power system, the influence on the power supply system is analyzed when a single short circuit fault and break down fault occur in magnets at different stages. A mathematical model is established to explain the change of the power supply circuit after the fault occurs. According to the mathematical model, the current and voltage changes of each coil under fault conditions are analyzed. Combined with the existing protection system, the protection strategy for high pulsed magnetic multi-power supply system is proposed. In this paper, the simulation results verify the accuracy of the analysis and control strategy.

Speaker: Zhangfei Zhao (1.College of Mechanical and Electronic Engineering，Suzhou University 2.Wuhan National High Magnetic Field Center Huazhong University of Science and Technology)

786 Thu-Mo-Po4.01-06 [5]: Analysis of the commutation of the 24-pluse converter for high plused magnet outer coil power supply

Wuhan National High Magnetic Field Center (WHMFC) has been working on high pulsed magnetic fields and designed the 100 Tesla magnetic system. The magnet adopts a three-coil structure and the outer coil is powered by a pulse generator rectifier. In order to ensure the temperature rise of the coil is reduced, the energy stored in the coil needs to be quickly released after the combined magnetic field reaches a maximum. However, there have two disadvantages by using a forced commutation device to switch the main circuit to the Crowbar freewheeling circuit, on the one hand, the negative end of the outer coil is suspended, and on the other hand, the grounding of the coil is caused to oscillate after forced commutation. Therefore, the rectifier should work in inverter model after the discharge is completed that can feed back the energy stored in the outer coil to the pulse generator. In order to ensure the safe operation of the rectifier and prevent the inverter from failing, this paper establishes a simplified circuit model of the 24 pulse rectifier system. According to the simplified circuit model and the actual power system parameters, the circuit equation for four rectifiers is established under different commutation overlap angles. the safe area for the 24-pulse converters commutation is be obtained based on the influence of four 6-pulse rectifiers in the commutation process analyzed which can resulting in commutation failure.

Speaker: Zhangfei Zhao (College of Mechanical and Electronic Engineering; Suzhou University 2. Wuhan National High Magnetic Field Center Huazhong University of Science and Technology)

787 Thu-Mo-Po4.01-07 [6]: Properties of Selected High-strength Composite Conductors

Cu-Ag and Cu-Nb composites, which have been successfully used in high field magnets, reach their most desirable strength level when their interface spacing is below 100 nanometers. The usual fabrication methods for these composites are either cold rolling or cold drawing, both of which refine interface spacing and create anisotropy. These methods may also introduce shear-bands into the microstructure. Understanding both anisotropy and shear-bands helps to understand the deformation mechanisms of these composites under magnetic force. The goal of our research is to relate microstructural anisotropy to the mechanical and physical properties of these composites in various geometries. Our current work is shedding new light on the detailed correlation between microstructure and properties. This paper describes microstructure in different orientations, with emphasis on the impact of anisotropy and shear-band on properties.
This work was performed at the National High Magnetic Field Laboratory, which is supported by the National Science Foundation Cooperative Agreement No. DMR-1644779 and the State of Florida

Speaker: Ke Han (national high magnetic field laboratory)

MT26_Thu-Mo-Po4.01-07_Han.pdf

Thu-Mo-Po4.02 - Test Facility

Conveners: Thanatheepan Balachandran (University of Illinois), Yusuke Sogabe (K)

788 Thu-Mo-Po4.02-01 [7]: Design and Implementation of Interlock System for CFETR CSMC Testing Platform based on FMEA

The Central Solenoid Model Coil (CSMC) of the China Fusion Engineering Test Reactor (CFETR) is currently in the manufacturing process. After the manufacturing completed, the CSMC will be test on the testing platform. This platform consists of several subsystems, in order to keep the system safe and to avoid any failure possible to damage CSMC magnet during the experiment, we have designed the interlock system. Failure Mode and Effects Analysis (FMEA) are introduced help us to find potential failure mode of subsystem, and according to the FMEA OSD (Occurrence Severity Detection) marks, the system failure will be divided into three levels. Also there is one interlock strategy for each failure level, when a critical failure occurs, the related subsystems will receive the interlock signal and lock the system or initiate fast ramp down sequence. The hardware of interlock system is based on industrial PLC and the communication protocol is OPC UA. Design and implementation details will be described in the paper.

Speaker: Mr Tong Li (Hefei institutes of Physical Science Chinese Academy of Science, University of Science and technology of China)

MT26 Litong.pdf

789 Thu-Mo-Po4.02-02 [8]: Carpenter: superconducting magnet test facility management system

Superconducting magnets at CERN are being tested in one of the largest testing facilities around the world known as SM18. The test facility is equipped with ten horizontal test benches, five vertical cryostats and a cryogenic feed box allowing to test the superconducting link in He gas. This unique infrastructure requires a well-designed and optimized quality assurance and control system to follow-up, monitor and trace all ongoing activities. In 2017 we created Carpenter, a fully customized management system to improve work organization. In addition to its main functionality of quality control for tested items and assemblies, the system enables also to store all relevant test results which can be later used for automatic test report generation. Carpenter uses a web interface for easily access and database for storage. Since January 2018, Carpenter system is fully operational at SM18 and it is being introduced to other superconducting magnet test facilities. In this paper the system philosophy, user workflow and implementation details are discussed.

Speaker: Michal Duda (IFJ PAN)

MT26-poster-Thu-Mo-Po4.02-02.pdf

790 Thu-Mo-Po4.02-03 [9]: Preliminary Design of HEPdipo, a Nb3Sn Large Aperture Dipole Magnet for Cable and Insert Coil testing

The HEPdipo magnet is being designed within a collaboration among CERN, EPFL-SPC, F4E and LBNL. The goal is to provide, with a background field of 15 T, the capability of testing insert coils and cables for high energy physics and fusion applications at variable temperature.
The target field of 15 T is generated at 4.2 K over a bore aperture of 144 mm × 94 mm and a length of about 1 m. The chosen technology is based on a bath cooled Rutherford cable and flared ends block-type coils pre-loaded using a bladder-and-key support structure. The design features three double-pancake coils with the same numbers of turns.
After the initial definition of the main parameters and a comparison between different coil layouts, in this paper we report on the status of the magnet design. In particular, 3D finite element magnetic and mechanical models are used to evaluate field profiles and peak stresses on coils and structure components. The results of the quench protection analysis are also described.

Speaker: Douglas Martins Araujo (CERN)

MT26_POSTER_1.pdf

MT26_POSTER_1.pptx

791 Thu-Mo-Po4.02-05 [10]: Concept Design of magnet system of the large scale superconducting conductor test facility for future fusion reactor

“China Fusion Engineering Test Reactor (CFETR)” is a new generation of tokamak which aims to bridge the gaps between the fusion experimental reactor ITER and the demonstration reactor (DEMO). The superconducting magnet system is the core component in tokamak and future fusion reactor, and the superconducting magnet system for CFETR will be a big challenge due to the higher magnetic field is required. Base on current design, the maximum field of Toroidal Field (TF) coil is around 14.5 T, and for Center Solenoid (CS) coil, the maximum field would be even higher. Now the significant work is developing high performance Cable-in-Conduit Conductor (CICC) for these high field coils.
Obviously, a test facility is necessary for developing new CICCs. It is well known that SULTAN facility plays an important and successful role in ITER conductors development, almost all ITER sample conductors were tested at SULTAN. But it’s hard to satisfy future test work due to its magnetic field limitation (<12 T). Now in China, a new program has been launched to build a new conductor test facility which has similar functions to SULTAN, but can provide background field up to 15 T. This paper will introduce the concept design of the magnet system of the superconducting conductor test facility.

Speaker: Dr Chao Dai (Institute of Plasma Physics, Chinses Academy of Science)

Conceptual Design of 15 Tesla Conductor Test Facility for Future Fusion Reactor.pdf

Conceptual Design of 15 Tesla Conductor Test Facility for Future Fusion Reactor.pptx

792 Thu-Mo-Po4.02-06 [11]: Upgrade of sub-systems and performance improvement for a versatile multi-field test facility of superconducting wires and tapes

A versatile facility capable of providing cryogenic-electro-magnetic multifields had been successfully constructed for investigating the field-dependent and mechanical properties of superconducting wires and tapes at Lanzhou University, China. It can generate a 3.5T transverse background field, and continuous variations of temperature (4 to 77K, ~5K/min) and transport current (0 to 700 A, 3A/min) for versatile mechanical test of superconductors. With enormous efforts and R&D work, promising results have been achieved with the versatile facility. Aiming at the improvements of superconductors’ property, the versatile multi-field test facility needs to be more upgraded on operating range and sub-system structures for background superconducting magnet and variable-temperature cryogenic system. This paper presents the latest results with upgrade of the versatile multi-field test facility. In the upgraded facility, the split superconducting solenoid magnets with the helium re-condensation system to circulate the evaporated helium gas were manufactured to generate a transverse background field up to 5.5 T in a relatively larger room space of 100 mm  H1400 mm. For the purpose of experimental efficiency, an improved cryogenic system consisting of a vacuum Dewar vessel with a visible window cooled by a Gifford–McMahon (GM) cryocoolers for providing refrigeration was built independently to accommodate the room space of the background split magnet. Based on this new design, the rapid continuous variations of temperature (4 to 293 K, ~15K/min) and transport current (0 to 1000 A, 3A/min) in the superconducting wires and tapes tests can be improved well. And the advanced instrumentation and the multi-field data acquisition system allow accurate measurements of dynamic strain and current distribution, transient stability, DC behavior, and AC losses. Upgrade of operating range and sub-systems for the versatile multi-field test facility will contribute to the progress in understanding design issues for superconducting wires, taps and cables under intense field, cryogenic temperature, transport current, and mechanical loading, also including quench propagation, material segregation, coupling loss, joint and cyclic load.

Speaker: Xingzhe Wang (Lanzhou University)

Thu-Mo-Po4.03 - Novel Diagnostics and Other Techniques

Conveners: Emmanuele Ravaioli (CERN), Takanobu Kiss (Kyushu University)

793 Thu-Mo-Po4.03-01 [12]: Development of a radiation resistant magnetometer

The operation of next generation accelerator facilities like the Facility for Antiproton and Ion Research (FAIR) around the world requires novel approaches for instrumentation to survive the expected radiation doses in, for example, secondary beam production regions. As particle beams at high energies are guided with strong magnetic fields one key piece of instrumentation is a precise, radiation-resistant magnetic field sensor. However, conventionally used NMR- and Hall probes can’t survive the anticipated radiation doses. Therefore, we propose to employ a Penning trap mass spectrometer for the magnetic field measurements in such inhospitable environments. They can be made compatible with radiation, as all required electronic components can be kept shielded at a safe distance.
Penning traps have been utilized in mass spectrometry for decades by measuring strong magnetic fields via the cyclotron frequency of an ion of known charge-to-mass ratio. For the purpose of monitoring the magnetic field a miniature magnetometer was developed within the LEBIT group at the National Superconducting Cyclotron Laboratory (NSCL) demonstrating a relative precision better than 0.1ppm, being competitive to the performance of NMR probes. Its size is almost compatible to tight space conditions inside beam line magnets and will only require moderate miniaturization.
In this contribution, we are going to present the current status of the project and where these magnetometers will be employed. Additionally, we will outline our plans to miniaturize the device even further.

Speaker: Martin Eibach (GSI Helmholtzzentrum für Schwerionenforschung)

Development of a radiation resistant magnetometer.pdf

794 Thu-Mo-Po4.03-02 [13]: Development of rotating coil measurement system

A rotating coil measurement system was developed for the DC magnets of the CSNS accelerator. This system solves the compatibility problems of different center heights, masses, effective lengths, and magnetic field strengths among CSNS bulk magnets. After testing, the repeatability error of the integral field measurement is less than ±0.02%, the repeatability error of harmonics are less than 0.005%, the repeatability error of the magnetic center measurement is less than ±0.03mm. It successfully completed the task of detecting 150 magnets of the Chinese spallation neutron source. In this paper, the development plan, function, accuracy, types of finished magnets and some measurement results are introduced.

Speaker: Dr Jianxin Zhou (Institute of High Energy Physics, CAS)

795 Thu-Mo-Po4.03-03 [14]: Current Reset in Superconducting Devices

Many superconducting devices operate in persistent mode. Heat losses from current leads are one of the major design challenges, especially when limited low-volume cryogen is available during normal operations. To reduce the heat losses, the current leads are either retracted after charging, or have permanent leads carrying smaller current when in a charging mode but have small heat load when in normal operating modes. The devices may require periodic current/magnetic field adjustment. It might be advantageous to ramp the unit to zero current when there is a long-time power outage or system malfunction. The ramp and re-calibration require engagement of the current leads and establishing high-current electrical path between components located outside of the cryogenic vessel and superconducting coils in the cryogenic vessel. Significant challenges need to be addressed including operation in automated, remotely-controlled mode, multiple engagements without performance degradation, operation in a high magnetic field and Lorentz force, need in multiple monitoring sensors and appropriate redundancy, long time in operation with minimum or no maintenance, and other factors. We evaluate several options of remotely-controlled retractable high-current leads that include several current reset options, fixed permanent leads with low heat load capable of carrying enough current to couple to a flux pump that periodically replenish and maintain the operating current, and system monitoring and methods that can either improve the engagement of retractable high-current leads, or precisely adjust the current in the superconducting device.

Speaker: Michael Parizh (GE Global Research)

Thu-Mo-Po4.03-03 --- Current reset in superconducting devices.pdf

796 Thu-Mo-Po4.03-04 [15]: The Application of Coordination to Magnetic Measurement Automation: An SSW System Example

The automation of magnetic measurements prevents human operator errors from impacting measurements and ensures the repeatability of the measurements and the traceability of the results to specific measurement scenarios. The presented approach achieves automation via parametrized scripting; this offers the user additional flexibility by providing the ability to define families of measurements and to tailor measurement algorithms to match their specific requirements. The selection of Python, a popular general-purpose programming language, as a scripting language rather than inventing a new domain specific mini language, allows the use of such advanced programming language features as exception handling, encapsulation and modularization. Scripts employ coordination to direct the execution of the measurement, and, therefore, follow the principle of separation of concerns. This results in extrication of the control flow from the data flow. The system is configured from loosely coupled multi-threaded components communicating via events. The coordination of components is accomplished in two ways: a) event-based orchestration via a script that sends control events and waits for acknowledgement from components and b) data flow-based choreography via data events sent from one component to another. The application of these techniques to the construction of an automated Single Stretched Wire (SSW) system is described, along with experiences from the practical use of the system for alignment measurements.

Speaker: Dr Jerzy Nogiec (Fermilab)

Thu-Mo-Po4.03-04.docx

Thu-Mo-Po4.03-04.pdf

Thu-Mo-Po4.03-04 Poster.pdf

Thu-Mo-Po4.03-04 Poster.pptx

797 Thu-Mo-Po4.03-05 [16]: A Numerical Method to Calculate Spatial Harmonic Coefficients of Magnetic Fields generated by Screening Currents in an HTS Magnet

This paper presents a numerical method to calculate spatial harmonic coefficients of magnetic fields generated by screening currents in a high temperature superconductor (HTS) magnet. First, current density with screening currents considered in the individual turns of an HTS magnet is calculated using the 2D axisymmetric edge-element formulation and the domain homogenization technique. With these calculated results, the screening current distributions of all elements in the individual turns are transformed into equivalent “loop” currents at the center of mass of each element. Then, from the individual “loop” screening currents, spatial harmonic coefficients of magnetic fields may be obtained by use of combination of elliptic integral and Gaussian quadrature. We applied our approach to calculate spatial harmonic coefficients of selected HTS NMR magnets and compared them with the measured ones.

Acknowledgement
This work was supported by the National Research Foundation of Korea as a part of Mid-Career Research Program (No. 2018R1A2B3009249).

Speaker: Jeseok Bang (Seoul National University)

MT26_Thu-Mo-Po4.03-05_Harmonic Coefficients_JBKC_20190920.pdf

798 Thu-Mo-Po4.03-06 [17]: Design and optimization of the PCB search coils for the accelerator magnet measurements

Accurate and reliable magnetic field measurement is of great significance at various stages in the lifetime of accelerator magnets. The method of search coils is the most widely used on the magnetic measurements. Traditional search coils are machined and/or hand-wound, which have the poor repetition and weakness in the precision of the coil geometry and position. To overcome these issues, the printed-circuit-board (PCB) method is recently applied to the manufacture of search coils. This paper presents the design method and optimization procedure of the PCB search coils, comparing the electrical parameters between theoretical calculations, simulation and test results.

Speaker: Xu Liu (Huazhong University of Science and Technology)

799 Thu-Mo-Po4.03-07 [18]: A Novel Diagnosis Method through Pulse Sequence Analysis of DC Void Partial Discharge in High Temperature Superconducting Cable

In an HVDC high-temperature superconducting (HTS) cable composed of polypropylene laminated paper (PPLP), a butt-gap which is unavoidable in the fabrication process may lead to form voids. When dc voltage higher than partial discharge inception voltage (PDIV) is applied, partial discharge occurs in the void. If void discharge sustains, the electrical ageing of PPLP accelerates, and eventually dielectric breakdown may occur due to the lowering of dielectric strength. Therefore, for reliable insulation design and maintenance of HVDC HTS cable, insulation diagnosis technology is required. Since there is phase information in the AC voltage, defect identification and diagnosis in the HVAC HTS cable are performed through ac partial discharge measurement and Phase Resolved Partial Discharge (PRPD) pattern analysis. However, since there is no phase information in the DC voltage, insulation diagnosis using PRPD is impossible. Therefore, for the insulation diagnosis of the HVDC HTS cable, the DC partial discharge pattern analysis technique using the Pulse Sequence Analysis (PSA) method is required. Consequently, in this paper, to suggest the insulation diagnosis method for void defects of the HVDC HTS cable, void partial discharge was measured according to the size of void and magnitude of applied voltage. Also, patterns of the void partial discharge were obtained using PSA method and PYTHON program. From the experimental results, although the magnitude, time difference and repetition rate of partial discharge are different depending on the configuration of the void and the applied voltage, it is confirmed that the patterns of partial discharge have similar shapes. Therefore, it is considered that insulation diagnosis for void defects in HVDC HTS cable is possible through the obtained DC void partial discharge patterns.

Speaker: Mr Dong-Hun Oh (Hanyang University)

Thu-Mo-Po4.03-07[18]_Presentation.pdf

800 Thu-Mo-Po4.03-08 [19]: Feasibility Study of Distributed Optical Fiber Applied in the Temperature Measurement of HTS Cables

Abstract: Temperature measurement is very important for the state monitoring and safe operation of High Temperature Superconducting (HTS) cables. Distributed optical fiber can be used to measure the temperature along power cable because of the advantages of anti-electromagnetic interference, high voltage resistance and convenient fixing, etc. In this paper, the feasibility of distributed optical fiber used for temperature measurement of HTS cables was studied. A temperature rise test of liquid nitrogen temperature to room temperature was designed to check the temperature measurement accuracy of the optical fiber. In local thermal disturbance experiment and the critical current experiment, optical fiber was used to measure the dynamic distribution of temperature along a HTS cable. Temperature measurement results of optical fiber installed at different positions in HTS cable are analyzed, and the best installed position was determined by comparing different temperature measurement effects.
Keywords: Distributed optical fiber, temperature measurement, HTS cable, feasibility

Speaker: Mr Kao Zhou (Huazhong University of Science and Technology)

801 Thu-Mo-Po4.03-09 [20]: Characteristic Resistance Measurement of No-Insulation REBCO Pancake Coil under Different Conditions

The no-insulation (NI) winding technique improves the thermal stability of REBCO pancake coils. A radial bypass current protects an NI pancake coil from burning-out when it turns a normal state. That is, the characteristic resistance (turn-to-turn contact resistance) of NI REBCO pancake coil characterizes the electrical behavior inside the coil as a function of “self-protecting.” To estimate or predict the thermal stability, the characteristic resistances are measured through a sudden discharging test. The sudden discharging test estimates the characteristic resistance from a measured time constant and a calculated coil inductance. However, it is well known that the characteristic resistance varies depending on the temperature, the current, and the magnetic field (i.e. stress condition). It is hard to measure the changing characteristic resistance under different conditions by means of the sudden discharging test.
We have recently developed a characteristic resistance measurement method using an AC current. The developed AC-current method easily measured a characteristic resistance under zero magnetic field and zero DC transport current. As a next step, we tried to measure the characteristic resistances of NI REBCO pancake coil under different temperatures or DC operating currents. The dependency of the characteristic on the temperature and transport current is very useful information to know the electromagnetic behaviors inside NI REBCO pancake coils.

Speaker: So Noguchi (Hokkaido University)

poster_RcMeasurement.pdf

802 Thu-Mo-Po4.03-10 [21]: Design and Analysis of a Novel Two-Dimensional High Frequency Magnetic Tester for Nanocrystalline Alloy Material

Compared with other magnetic materials, nanocrystalline alloy has specific advantages. It can be made into strips that much thinner than silicon steel sheets and its conductivity is lower, which effectively reduces the high frequency loss. The permeability of nanocrystalline alloy is higher than that of ferrite, so the capacity and power density of the equipment made from nanocrystalline alloys can be larger at the same volume. In addition, the operating noise of nanocrystalline alloy is lower than that of amorphous alloy.
Nanocrystalline magnetic block cores can be used to make the high frequency electrical equipment, which exists T-joints structure. Due to the existence of magnetic flux leakage, the local two-dimensional (2-D) circular or elliptical magnetic field in the T-joints structure can cause rotational core loss. Therefore, it is necessary to study the 2-D high frequency rotational magnetic properties of nanocrystalline alloy materials.
This paper proposes a novel 2-D magnetic tester for nanocrystalline alloy material. The push-pull double-yoke vertical structure with square sheet specimen (28mm*28mm) is designed and fabricated to flexibly measure 1-D and 2-D magnetic properties up to 50 kHz. The magnetizer is made of nanocrystalline alloy sheet (0.02mm). Due to the high permeability of the material, the excitation current in the magnetization process is low and the excitation frequency can reach a higher level. The excitation effect of windings at different positions is simulated and compared. Considering the actual requirement, the 4-segment excitation winding on both sides of core is designed and every segment has ten-turn litz wire coil, which can be flexibly adjusted according to excitation frequency. A specific sensing structure with cross-shaped B needle method and double H sensing coils is adopted to guarantee the 2-D magnetic signals detection and improve the experimental precision. The losses measured by the tester under 1-D alternating excitation is compared with the official data, which has good accuracy. The 2-D magnetic rotational properties and losses of nanocrystalline alloy square sheet specimen are measured and analyzed.

Speaker: Yongjian Li (Hebei University of Technology)

Thu-Mo-Po4.03-10 [21] Design and Analysis of a Novel Two-Dimensional High Frequency Magnetic Tester for Nanocrystalline Alloy Material.pdf

803 Thu-Mo-Po4.03-11 [22]: Implementation and first operational experiences with the high voltage In-Service-Tests on the superconducting magnet system of Wendelstein 7-X

A hypothetical ground fault in the superconducting (sc) magnet system of Wendelstein 7-X would shift the midpoint of the grounding system and therefore increase the voltage to ground during a fast discharge of the sc magnet system. As this voltage could endanger the high voltage integrity of the sc magnet system, an In-Service-Test system has been developed to monitor the insulation of the sc magnet system during operation especially after changing the loads of the magnets. The system, that is associated to the power supply system, is designed to lift the electrical potential of non-planar coil system with respect to ground by 1.5 kV and to measure the resulting leak current while the magnets are operated. The leak current is used to evaluate any changes in the insulation resistance and to decide whether a fast discharge can still be done without endangering the sc magnet system. The design of the In-Service-Test was evaluated with computer simulations of the power supply and the magnet system, and a prototype that was tested at one coil group together with the corresponding power supply. In 2014, the system was finally installed for all five non-planar coil groups and commissioning took place for the first experiment campaign in 2015. Operated during the first experimental campaigns of Wendelstein 7-X from 2015 to 2017 the experiences gained led to modifications that already have been implemented and tested during the operation campaigns in 2018 and 2019.
The paper describes the implementation of the In-Serve-Test system and the associated tests for the commissioning as well as the first operational results and corresponding modifications.

Speaker: Mr Frank Füllenbach (Max-Planck-Insatitut für Plasmaphysik)

804 Thu-Mo-Po4.03-12 [23]: Presentation withdrawn

Thu-Mo-Po4.04 - Fusion VII: Joints and Terminations

Conveners: Boris Stepanov (EPFL), Louis ZANI (CEA-IRFM)

805 Thu-Mo-Po4.04-01 [24]: Design and Manufacture of a prototype Nb3Sn-NbTi full-size joint sample for the CFETR Central Solenoid Model Coil

In order to develop and verify the key techniques and manufacturing process of the full-size central solenoid (CS) coil for China fusion engineering test reactor (CFETR), the central solenoid model coil (CSMC) project has been launched in the Institute of Plasma and Physics, Chinese Academy of Sciences (ASIPP). The CFETR CS model coil is a hybrid superconducting magnet of 12 T maximum magnetic field when the running current is 47.65 kA, which consists of two Nb3Sn windings in internal high field and three NbTi windings in external low field. The five windings contains six joints and two leads for two NbTi feedthroughs are used to connect the three windings of them. The six joints contains 4 Nb3Sn-NbTi lap joints and 2 NbTi-NbTi lap joints. A full-size Nb3Sn-NbTi prototype joint sample has been designed and manufactured. This sample composed of two single conductor legs, a lower joint of praying hands structure to be placed in the high field, and two upper terminals to be connected to the transformer of the test facility. In this paper, the sample design, the techniques used for the manufacturing steps of the different conductor legs, the terminations and the assembly are described in detail. This prototype sample will be tested in the Sultan facility at Villigen (Switzerland) and will be a model for the manufacture of joints for the CSMC.

Speaker: Guanghui Ma (Institute of Plasma Physics Chinese Academy of Sciences)

Thu-Mo-Po4.04-01 [24].pdf

806 Thu-Mo-Po4.04-02 [25]: Development of CORC® Cable Terminations and Low-loss Joints for use in Magnets for Fusion

High-temperature superconductors (HTS) are promising candidates for use in the high-field magnets needed in thermal nuclear fusion reactors. Their high critical temperatures allow them to operate at temperatures far above 4 K and ease requirements on nuclear heat generation and heating during ramping of the magnetic field. Other benefits compared to low-temperature superconductors include higher mechanical strength and the possibility to operate at high magnetic fields, exceeding 16 T. Advanced Conductor Technologies is developing HTS Conductor on Round Core (CORC^®) cables and wires wound from ReBa₂Cu₃O_7-x (ReBCO) coated tapes, for use in high-field magnet applications. HTS cables can enable demountable fusion magnets that would allow easier access to the fusion experiment for maintenance and parts replacement. CORC^® cables are also developed for fusion magnets operating at currents in excess of 80 kA, requiring them to be bundled into a cable-in-conduit conductor (CICC) configuration. Major technical challenges to the use of ReBCO coated conductors in fusion magnets include the need for high current capacity magnet cables and practical, low-resistance cable joints, capable of injecting current uniformly into the many tape layers that make up the cables. Optimization steps on CORC^® cables have resulted in high current terminations that have a significantly improved contact resistance with even current injection at high ramp rates exceeding 6 kA/s. Several individual joints were constructed and tested in liquid nitrogen and liquid helium to currents up to 9,000 A with contact resistances as low as 96 nΩ at 76 K and 6 nΩ at 4 K. Schemes for bundling multiple cables together into CICC conductors are being explored to enable stable 100 kA-class joints with contact resistances of less than 1 nΩ.

Speaker: Jeremy Weiss (Advanced Conductor Technologies)

190916-Weiss - MT26-2019-Poster-Fusion terminations and joints-final-v2.pdf

807 Thu-Mo-Po4.04-03 [26]: Dependence of joint resistance on current for ITER-TF joint samples

Joint resistances of eight short samples have been measured until 2018 as a qualification test for ITER Toroidal Field (TF) coils. The joint sample consists of two short TF conductors with the length of 1.535 m, and each conductor has two joint boxes at both ends. The lower joint is a testing part that is full size joint of the TF coil. The upper joint is connected to 100 kA current leads of a conductor test facility with 9 T split coils. Voltage taps are attached at three positions in the original conductor part of the length of 0.3 m between the two joint boxes. Hall probes are attached on the lower joint box at around the center of the external field coils to measure the shielding current. The voltage drops between L-leg and R-leg conductors were measured with six voltage taps per position per conductor while holding sample currents for three minutes at 1, 15, 30, 45, 60, and 68 kA. In a few cases, the voltage drops at 3, 6, 9, and 12 kA were additionally measured. The joint resistance of the lower joint is estimated from the increase of the average voltage drop among the six taps against the currents. In all the samples, the difference among the voltages of the six taps is enlarged to the range of 0.01 mV and saturated at less than 15 kA. In addition, the obtained data show that the joint resistance is increased with current at low current and converged to a certain value. Furthermore, decay time constant of shielding currents induced in the lower joint by shut-off of the external field coils is gradually elongated with decrease of the shielding currents, which suggests that the joint resistance is decreased at low current. With a simplified electric circuit model, these phenomena can be simulated by the assumption of existence of a strand contacted to the copper sleeve with extremely low joint resistance.

Speaker: Dr Tetsuhiro Obana (NIFS)

MT26_TF-joint_A0.pdf

808 Thu-Mo-Po4.04-04 [27]: Design Optimization and Assessment of Fabrication of ITER Central Solenoid Twin Box Joints

The ITER Central Solenoid (CS) will be one of the world’s largest and most powerful pulsed superconducting electromagnet ever built; at an approximate weight of 1300 tons and a total height of 18 m consisting of a stack of six electrically independent 4.1 m diameter modules. In order to electrically connect the CS with the feeder busbars, 12 twin box joints are used to assure an efficient high current transfer while avoiding excessive losses.

The fabrication of the box entails a succession of steps: explosion bonding of the stainless steel and the copper, precision machining of the internal part of the box and the cover, introduction of the conductor bundle followed by a controlled compaction to achieve the required void fraction, closure welding the cover onto the box, and subsequent reaction heat treatment (HT) for the formation of the Nb3Sn superconductor. The combined effect of all these fabrication processes, if not optimized, can lead to significant residual stresses (before) and large localized plastic deformation during HT, which have empirically shown to result into microstructural heterogeneities and in the worst cases, cracking, and thereby component disqualification for use into a nuclear environment.

The paper summarises design optimizations that were investigated and could be implemented to remedy the present manufacturing fabrication technology process qualification failure(s). Various solutions have been realized by changing different design parameters whose effect on the response to the HT is studied. Dimensional metrology and residual stress measurements via hole - drilling method complemented with metallographic investigations were performed to assess the suitability of each of the solutions. Additionally, an innovative test bench is described, that was implemented for in – situ monitoring of one of the twin box mockups during HT.

Disclaimer: The views and opinions expressed herein do not necessarily reflect those of the ITER Organization.

Speaker: Ignacio Aviles Santillana (CERN, University Carlos III (ES))

poster TBMs.pptx

809 Thu-Mo-Po4.04-05 [28]: Demountable Coaxial Clamped Joint For ITER Central Solenoid Module Final Test Program

The ITER Central Solenoid Modules (CSM) are being fabricated at General Atomics (GA) at their Poway, CA Magnet Technologies Center. Each of the seven modules will undergo final testing at the GA facility to demonstrate their performance with full current of 48.5 kA, 11 T and at 4.5 K. In order to perform tests on multiple modules, a demountable coaxial joint using indium wires was developed to connect the modules to the feeders. Two full scale joints were fabricated to establish the assembly technique and preliminary tested (up to 3 kA) on the CSM qualification coil (Cu conductor). The same joint components were then tested using a superconducting jumper (NbTi) and their resistance measured (2.3 and 4.9 nΩ, at 4.5 K, 40 kA). In parallel to measuring the voltage across the joints, a calorimetric evaluation was also performed and it confirmed the low resistance measurements of both joints. Testing of the same coaxial clamped joints on a heat treated Nb3Sn jumper took place in February 2019 and the results are reported in the paper. With acceptable results, the same joint components and assembly techniques will be utilized to connect the 14 joints on the seven CSM (Nb3Sn) for full current testing. This work was supported by UT-Battelle/Oak Ridge National Laboratory under sponsorship of the US Department of Energy Office of Science under Awards 4000103039 and DE-AC05-00OR22725.

Keywords: Superconducting Coils, coaxial joints, Indium, resistance, Cable in conduit conductor, ITER, 4.5K test facility, Nb3Sn, NbTi

Speaker: Dr Zbigniew Piec (General Atomics)

GA Coax Joint-Poster.pdf

810 Thu-Mo-Po4.04-06 [29]: Research and Development of the Heater Chains for the ITER Current Lead Terminals

Abstract: In the superconducting magnets system of the International Thermonuclear Experimental Reactor (ITER) project, the heater chains are used to avoid heavy condensation or ice formation on the current leads of feeder. As an insulating and heat-conducting component, the heater chains should satisfy electrical insulation and thermal conduction properties at the same time. Due to no alternative commercial solutions, the heater chains for the current leads of the superconducting system of ITER were developed in the Institute of Plasma Physics, Chinese Academy of Sciences. The heater chains were manufactured with heater resistance, Al2O3 ceramic, MgO filling insulator, polyimide and aluminum (Al) at room temperature but operated at high temperatures. Development of the heater chains aims at satisfying the electrical and thermal requirements involving high electrical insulation and high thermal conductive properties at high temperature. For the 68 kA current leads for the toroidal field (TF) superconducting magnets, in order to operate without significant delays, an approximate heating power of 3 kW at the warm terminals of current leads are provisioned to compensate the overcooling at standby condition. When the TF superconducting magnet is quenching, the warm terminals of the current leads have the same electric potential (or high voltage) as the TF superconducting magnet, however, the assuming electric potential 56 kV DC of the TF superconducting magnet is much higher than the electric potential 220 V DC of the resistance wire of heater. In this paper, the electrical and thermal analyses of the developed prototype heater chains based on finite element models were performed. In particular, the relationship between the structure and the electrical field distribution and temperature distribution of the heater chains were investigated, the simulating results indicate the structural design of the heater chains is feasible. Further insulating property and thermal property tests verify that the developed prototype heater chains can satisfy the functional requirements.
Keywords: Current leads, Superconducting magnet, ITER, Insulation, High voltage, Polyimide

Speaker: Mr Wanjiang Pan (Institute of Plasma Physics, Chinese Academy of Sciences)

811 Thu-Mo-Po4.04-07 [30]: Induced currents and AC losses models for a butt-joint with rutherfords shunts

The ITER Central Solenoid (CS) has terminal butt-type joints called Coaxial joints. It was decided to study a design of this joint with rutherford shunts, and to build models for its resistive and inductive behaviors. In particular, the behavior of the joint under magnetic field transients is investigated with various analytical models that are compared with a FEM model. The key point of the study was to verify that the induced currents were reasonable and would not induce flux jumps in the rutherfords. A prototype with simplified geometry was tested in the CEA Josefa facility under various field ramps. The results are presented and discussed.

Speaker: Alexandre Torre (CEA)

PapierCoax_V0.4 - DRAFT.docx

PapierCoax_V0.4 - DRAFT.pdf

Poster AC losses_V2.pdf

Poster AC losses_V2.pptx

Thu-Mo-Po4.05 - Other High Tc Wires and Cables

Conveners: Dr Alexander Otto (Solid Material Solutions, LLC), Geonwoo Baek (Yonsei University)

812 Thu-Mo-Po4.05-01 [31]: New precursor powders fabrication technique for Bi-2223 high temperature superconducting tapes

Nowadays, although the fabrication techniques of high temperature superconductors have been far developed, Bi2Sr2Ca2Cu3O10 (Bi-2223) high temperature superconducting tapes are still the ones the most mature fabrication technique and the most stable batch production ability, not to mention their stable mechanical configuration. Therefore, for the construction of many big scientific facilities, including cables, and magnets with different design and target fields, Bi-2223 tapes are still considered to be the first candidate. However, aiming at building the magnet with large shimming area, the uniformity of Bi-2223 tapes has to be further improved. Due to the intrinsic drawbacks of the present fabrication techniques for Bi-2223 precursor powders, such as co-precipitation process and spray pyrolysis process, it is very difficult to obtain powder with highly uniformed chemical composition as well as particle size distribution. Therefore, in our study, a new technique, named frozen drying process has been adopted for the fabrication of Bi-2223 precursor powders. Based on the obtained results, with this frozen drying process and properly optimized fabrication parameters, precursor powders with exact chemical composition as nominal values, high uniformity of chemical composition, narrow particle size distribution and low carbon content have been achieved. By optimizing the calcination temperatures, it was noticed that due to the decrease of particle size, the optimal sintering temperature decreased obviously, comparing with the co-precipitated powders. At last, multifilament tapes were fabricated with frozen dried powders, and the critical current of ~100 A were obtained by optimizing the sintering process of Bi-2223 tapes. The uniformity of obtained tapes has also been proved to be effectively improved, which should be beneficial to the fabrication of magnets.

Speaker: Mr Chengshan Li (Northwest Institute for Nonferrous Metal Research)

Thu-Mo-Po4.05-01[31].pdf

813 Thu-Mo-Po4.05-02 [32]: Structure material performance evaluation for Bi2212 CICC conductor

At present, Ag- sheathed Bi2212 is considered as the most suitable superconducting material to alternate the Nb-based material for the CICC conductor operation with the magnetic field higher than 20T. However, the Bi2212 round wire application technology development encountered difficulties, due to the complicated Bi2212 CICC manufacturing processes, the low mechanical performance as well as the stress and strain sensitivity of the Bi2212 wire. Therefore, structure material for Bi2212 CICC, such as cable strengthening material, cable wrapping material, Jacket and so on, are critical for keeping its stability performance. This paper reports the investigation results of three candidate structure materials, the high Mn steel and Ni80Cr. Especially, the effects on the microstructure and performance of these three materials during the Bi2212 phase forming heat treatment.

Speaker: Ms Huan Jin (Institute of Plasma Physicas)

814 Thu-Mo-Po4.05-03 [33]: Mechanical and Electrical Testing of A Novel Enhanced Bi2212 Round Wire

Abstract-High temperature superconducting material Bi 2212 has outstanding conductor-carrying capacity at 4.2 K in magnetic field and it is the only high temperature superconducting material that can be made into isotropic round wire (RW). Therefore, it’s considered to be one potential material for CICC (Cable-in-Conduit Conductor) in high magnetic field application, especially when magnetic field is over 15T. However, Bi2212 phase is a ceramic structure, which is sensitive to strain. And Bi2212 round wire has low mechanical properties because its sheath whose composite materials are Ag and Ag Mg alloy is soft. In the process of operating CICCs, strong Lorentz force will cause the deformation of superconducting wires in CICC and, therefore, cause the degradation of superconducting performance of the wires. In this paper, a novel enhanced structure of Bi2212 round wire is presented in order to improve its mechanical performance. Mechanical and electrical tests of this novel enhanced Bi2212 round wire were operated to validate the structure. And relevant results will be also reported in the paper.

Index Terms-high-temperature superconductor, enhanced Bi 2212, mechanical and electrical tests

Speaker: Jinggang Qin (Institute of Plasma Physics, Chinese Academy of Sciences(ASIPP))

815 Thu-Mo-Po4.05-04 [34]: Critical Current under Axial Strain of High-Pressure HT Bi-2212 Round Wire

China Fusion Engineering Test Reactor project (CFETR) , the next generation of Tokamak of China, has been incorporated into the important development of nuclear fusion in the future. Compared to low temperature superconducting materials, Bi-2212 is more promising due to the high irreversible field and outstanding current-carrying capacity. In particular, its critical properties can be improved dramatically by high-pressure heat treatment, which could enlarge its application range. The axial strain measurements on Bi-2212 round wire with different heat treatments were performed at 4.2K in 12T background field at Institute of Plasma Physics, Chinese Academy of Science (ASIPP). All samples are provided by Northwest Institute for Non-ferrous Metal Research (NIN) in China. The results showed that samples in 30 bar pressure heat treatment presented a more drastic degradation in compressive and tensile side than that of 50 bar pressure heat treatment. In order to study the influence of different thermal contraction coefficient between the substrate and sample on the experiment results, two springs with different materials were used in experiment. It was found that Cu-Be alloy spring is more compatible for Bi-2212 round wire as substrate than Ti-6Al-4V alloy spring from experiment results. In this paper, the experiment setup and results will be fully presented. This results also can provide experience for superconducting magnet further design and experiment.

Speakers: Prof. Huajun Liu (Institute of Plasma Physics, Chinese Academy of Sciences Hefei, China), Prof. Fang Liu (Institute of Plasma Physics, Chinese Academy of Sciences Hefei, China), Prof. Jinggang Qin (Institute of Plasma Physics, Chinese Academy of Sciences Hefei, China)

mt26_CH .pdf

816 Thu-Mo-Po4.05-05 [35]: Tensile mechanical properties of silver alloy sheathed Bi-2212 wires

Bi2Sr2CaCu2Ox (Bi2212) has the excellent current carrying properties at 4.2K and is one of the potential materials for superconducting magnets. In the construction and use of magnets, superconducting wires are subjected to complex stresses, so it is important to determine the mechanical properties of the wires. In this paper, the mechanical properties of Bi-2212 wire before heat treatment and after heat treatment with different pressures were compared and analyzed. The samples are provided by Northwest Institute for Non-ferrous Metal Research (NIN) in China. In order to determine the uncertainty of the experiment and accurately grasp the material properties, round-robin-tests were performed in different laboratories. It was found that the higher the heat treatment pressure, the better the mechanical properties of the sample. Besides, the strain hardening phenomenon was observed on the un-reacted wire at 4.2K. This paper summarizes the effects of heat treatment on the mechanical properties of Bi-2212, which provides a reference for material applications.

Speakers: Prof. Huajun Liu (Institute of Plasma Physics, Chinese Academy of Sciences Hefei, China), Prof. Fang Liu (Institute of Plasma Physics, Chinese Academy of Sciences Hefei, China), Prof. Jinggang Qin (Institute of Plasma Physics, Chinese Academy of Sciences Hefei, China)

MT-Poster@Xintao Zhang.pdf

MT-Poster@Xintao Zhang.pptx

817 Thu-Mo-Po4.05-06 [36]: Intra-wire resistance and AC loss of multi-filamentary Bi2212 round wire

A quantitative knowledge of the intra-wire transverse resistance is essential for a proper characterization of multi-filamentary Bi2212 round wires, and a better understanding of their performance in short sample tests and thus inter-strand current redistribution in cabled conductors.
Intra-wire resistance and AC loss of various multi-filamentary Bi2212 round wires have been measured and analyzed. Two particular four-probe voltage–current methods are developed to measure the transverse intra-wire resistance distribution directly under various temperatures. The AC loss is acquired by both vibrating sample magnetometer (VSM) and magnetization measurements in a wide range of temperatures. With the aid of finite element method simulations, the filament-to-matrix contact resistance and effective transverse resistivity are derived from direct intra-wire resistance measurements. The effective transverse resistivity values are in good agreement with those analytically derived from the AC coupling loss measurements.
Here, we present the results of the experiments and simulations, and demonstrate how the extracted characteristic parameters provide a better insight into the current flow patterns within the wires.

Speaker: Prof. Chao Zhou (Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, Anhui, China )

818 Thu-Mo-Po4.05-07 [37]: Impact of Axial Tensile Strain on the Inhomogeneity of Critical Current for Bi-2212 Round Wire

Bi2Sr2CaCu2Ox has excellent electromagnetic properties under high magnetic field, and can be made into isotropic round wire (RW) form. Therefore, it is easy to use cabling technology to make them as cable in conduit conductor (CICC) for the next fusion reactors. However, the Bi-2212 phase is a ceramic structure and sensitive to strain. In application, Bi-2212 RW will be affected by thermal stress and electromagnetic stress. It may cause the local damage of the wire and then affect the inhomogeneity of the critical current. The inhomogeneity of critical current in Bi-2212 RW is one of the factors affecting the performance of the superconducting magnet. In this paper, we investigate the impact of axial tensile strain on the inhomogeneity of critical current for Bi-2212 RW by a hall sensor array system. The distribution of the perpendicular component of the remanent field in the direction along the RW radial after tension is measured by a Hall sensor array. The local critical current of the RW is calculated through the method of calibration and the inhomogeneity of the critical current is described by Weibull statistical method. The results show that when the axial tensile strain exceeds the irreversible strain limit, the inhomogeneity of critical current for Bi-2212 RW increases significantly.

Speaker: Mr Wei Chen

819 Thu-Mo-Po4.05-08 [38]: Non-destructive evaluation of the critical current for Bi-2212 cable for fusion application

High-temperature superconducting material of Bi-2212 (Bi2Sr2CaCu2Ox) is considered to be used in the next generation of fusion reactors such as China Fusion Engineering Test Reactor (CFETR) due to extremely high critical current density as well as high critical field at low temperature. The critical current as well as its inhomogeneity is one of the important factors to evaluate the performance of the Bi-2212 wire, cable and conduct, and also it is important for the design of the superconducting magnet system. Commonly, the critical current is detected by four-probe method (electric method). The electric method, however, has its limitations, such as without the local characteristics and the need of large current source. In this work, non-destructive evaluation (NDE) by using Hall sensor array, a magnetic method, will be used for testing local critical current of Bi-2212 cable. NDE is more effective and faster method for testing local critical current of high temperature superconductor compared with conventional electrical method.

Speakers: Dr Yang Xinsheng (Southwest Jiaotong University), Wei Chen (Southwest Jiaotong University)

Thu-Mo-Po4.06 - Wind, Wave, Tidal Generators II

Conveners: Kohei Higashikawa (Kyushu University), Liudmila Potanina (Russian Scientific R&D Cable Institute (JSC VNIIKP))

820 Thu-Mo-Po4.06-01 [39]: Analysis of a Double-sides Stator-PM Linear Generator for Wave Energy Conversion

Linear generators are extensively applied to direct-drive wave energy converters (DD-WECs). Low power voltage and power density can be considered the main drawbacks of DD-WECs given their low direct-drive speed. To increase the output voltage and power, and reduce the number of PMs, a double-sides stator PM linear generator is proposed and researched in this paper, based on stator flux reversal PM machine.
There are three stators in the proposed generator, inner PM stator and outer primary stators. The secondary (mover) is composed of modulated teeth. Muti-teeth design is used to increase the frequency and value of output voltage. To show the performance of the proposed generator, a parallel magnetic circuit double-sides stator PM linear generator (SPMLG2) is compared with the proposed one. The equivalent modulated tooth number, the pole pair of inner and outer primary and be designed have modulated effect. A shift between outer primaries is designed to improve the linkage of armature windings.
2D finite element method (FEM) is implemented to analyze two generators. With three-phase symmetrical resistance load, under the speed of 0.5 m/s and same excited current, the no-load performance and on-load performance of the generators are obtained and presented.
It can be seen from the results, the cogging force of the proposed generator is not more than the cogging force of another linear generator. In addition, the voltage of proposed generator has low harmonic component and higher value. The out power of the proposed generator can research 3.7kw, is higher than ones of another generator. The voltage regulation factor is lower. Therefore, by using the proposed generator, higher output voltage, higher output power and lower voltage regulation factor can be obtained, under on-load condition. All the results show the proposed have field modulated effect and well suited for wave energy conversion.

Speaker: Lei Huang (Southeast University)

821 Thu-Mo-Po4.06-02 [40]: Performance of multi-layer fractional-slot concentrated windings for superconducting wind turbine generators in normal and short circuit operation conditions

Superconducting generator (SCG) technology is being proposed for large direct-drive offshore wind turbines due to their compactness and light weight. However, SCGs have intrinsically large magnetic air gaps and therefore produce unacceptably high torque during a short circuit. Among possible solutions, using fractional-slot concentrated windings (FSCWs) can reduce the short circuit torque to an acceptable level. However, FSCWs produce sub- and super-harmonics in the MMF which induce excessive AC losses in the superconducting field winding. Multi-layer FSCWs can be employed to reduce or eliminate these harmonics and keep a low AC loss level. Together with the advantage of suppressing the short circuit torque, multi-layer FSCWs are worth investigating to increase the technology readiness level of superconducting wind turbine generators. This paper presents four designs of multi-layer FSCWs for a 10 MW superconducting generator and evaluates their performance in the generator’s normal and short circuit operation conditions. A good balance of performance between these two conditions is required and this paper therefore compares these four designs with each other and with single-layer FSCWs.

The four multi-layer designs of FSCW all adopt the 12-slot/10-pole combination, and include:
1) Three-phase double-layer winding,
2) Dual three-phase double-layer winding,
3) Three-phase four-layer winding, and
4) Dual three-phase four-layer winding.

The performance indicators for the normal operation include levelized capital cost of energy, annual energy production, usage of superconducting wires, generator mass and AC losses in the superconducting field winding. The performance indicators for the short circuit condition include torque and field current.

Speaker: Dr Dong Liu (Hohai University)

poster for MT26 paper 1 v2.pdf

822 Thu-Mo-Po4.06-03 [41]: Thermal and mechanical design of 10 MW class HTS wind power generator

A 10 MW class HTS wind power generator is under development in Korea using REBCO wires for off-shore installation. NI (No-insulation) winding technique is applied to increase the electrical and mechanical stability of the rotor magnets using REBCO wires. The REBCO magnets, having operating temperature around 35 K, are designed to be cooled using forced circulation of cold helium gas. The cold helium gas would be cooled down through a heat exchanger in a rotating neon reservoir, which have been usually used in ‘MW’ class HTS rotational machine. Prior to the development of a cryogenic refrigeration system, thermal and structural design must be preceded to withstand the mechanical stress from large torque corresponding to 10 MW power.
This paper describes the design of supporting structures and the thermal characteristics of the REBCO magnet. The supporting structures considered the Lorentz force in the REBCO magnet, fully coupled with an electromagnetic design result of 10 MW class generator, under load and no-load conditions. In a limited cryogenic space, thermal stress was also considered. Thermal loads are estimated for the conduction from supporting structures, thermal radiation and current leads. Then, thermal analysis, combined with cooling channels where the cold helium gas flows, was conducted to verify that the maximum temperature of coil met the design criteria. The analysis and design results will be used to develop a rotating refrigeration system for the 10 MW HTS wind power generator.

Acknowledgments : This research was supported by Korea Electric Power Corporation. (Grant number:R18XA03)

Speaker: Mr Jaehwan Lee (Changwon National University)

823 Thu-Mo-Po4.06-04 [42]: Comparison of Electromagnetic Performance of 10-MW HTS Double-Stator Flux Modulation Generators With Different Topologies for Offshore Direct-Drive Wind Turbines

Offshore wind power, as a clean and renewable energy, has become the main growth point of wind power development. It is a trend, for offshore wind power, that large power even above 10 MW wind generators are preferred to reduce the cost per MW. Due to the advantage of much higher magnetic loading in the high temperature superconducting (HTS) machine compared to that of the regular machines, HTS wind generator becomes a potential candidate with higher torque density and efficiency for offshore wind direct drive generator in the future.
For HTS conventional synchronous generator, the SC field windings or armature windings are rotating, which could complicate their industrial feasibility for the offshore wind generation. In order to overcome this drawback, a kind of HTS double-stator flux modulation generator (HTS-DSFMG) with stationary seal is proposed. The field and armature coils are fixed on the two stator respectively.The rotor consists of the modulation ring and its supporting structure. Besides, modular cryostat concept is adopted for this machine.
This paper compares the electromagnetic performance of 10-MW HTS double-stator flux modulation generators with three different topologies, i.e., iron-cored stators with both field and armature coils, iron-cored stator with filed windings and air-cored stator with armature windings, and air-cored stator with filed windings and iron-cored stator with armature windings. In addition, the system comparison of HTS-DSFMG with conventional synchronous machine is conducted. The objective is to intensive study the advantages and disadvantages of HTS-DSFMG with different topologies, and to establish some design guidelines for HTS double-stator flux modulation generator with stationary seal.

Speakers: Yi Cheng (Huazhong University of Science and Technology), Yuting Gao (Huazhong University of Science and Technology), Yuanzhi Zhang (Huazhong University of Science and Technology), Qian Wang (Huazhong University of Science and Technology)

MT26--Thu-Mo-Po4.06-04 [42].pdf

MT26--Thu-Mo-Po4.06-04 [42].pptx

824 Thu-Mo-Po4.06-05 [43]: Design and feasibility study of a performance evaluation system for a large-scale HTS generator under short-circuit conditions

High temperature superconductors (HTS) are being applied to electric power systems such as generators, motors and reactors. Researches on HTS wind turbine generators are now focused on increasing efficiency and capacity. In the HTS generators, a large magnetic air gap exists because of needed space for a cryostat wall and thermal insulation. Consequently, the reactance is lower than that in a conventional machine. A lower reactance provides a faster dynamic response and a higher load capacity. On the other hand, it leads to a higher fault current and a larger transient torque under short circuit conditions. It would be very challenging to design the mechanical structure of a generator to withstand such a high peak torque since usually the generator structure is designed for three times the rated torque. To do this, a performance evaluation system (PES) is required to test the HTS field coil and structures before it is installed in the HTS generator. The output torque and Lorentz force of an HTS generator must be carefully investigated due to the high current density and magnetic field of the generator. In this paper, the design and feasibility study of a PES for a large-scale HTS generator under short-circuit conditions are presented. Based on the specifications of the 10 MW class HTS generators, the stator and field current, torque, and force of the HTS coil were analyzed under normal and short-circuit conditions. The PES was designed based on the results of electromagnetic analysis using FEM program. The analysis results were compared with full generator model to confirm the possibility of PED. We conclude that the HTS field coil can be practically tested using the proposed PESs whether the structure of the coil can withstand the high torque and force of the generator under normal and short-circuit conditions through stator and field current control. The proposed PES design and analysis results can be effectively used for the development of large-scale HTS wind power generation systems.

Speaker: Byeong-Soo Go (Changwon National University)

MT_poster_Thu-Mo-Po4.06-05_Byeong-Soo Go.pdf

825 Thu-Mo-Po4.06-06 [44]: Design and property analysis of a performance evaluation system for HTS wind power generators

Software-based simulations, such as finite element method (FEM), can identify the electromagnetic forces generated by high-temperature superconducting (HTS) coils in a generator, but structural errors can occur in actual manufacturing processes based on the simulation results. Because large wind turbines have high torque, the structural errors in the manufacturing process can cause fatal damage to the system during operation. In this paper, we proposed a performance evaluation system (PES) that can physically test the structural stability of HTS coils with high torque before the generator is manufactured. The PES consists of three HTS coils and corresponding armature windings for use in a 10 MW HTS generator. In the design of the PES, both the HTS coil and the armature are fixed, and the armature is supplied with the same three-phase current as the designed 10 MW HTS generator. The various performance of HTS coils and supports can be effectively evaluated before actual production using the proposed PES. The forces of the HTS coil for the PES were calculated by the Lorentz force equation and analyzed using a 3D FEM software. In the PES, a salient pole was used to have the same force of the generator, since the detent force between the HTS coil and the armature was generated by a linear machine. Through the simulation results, the forces of the PES and the designed HTS generator were compared. As a result, when the same 3-phase current as the HTS generator was supplied to the PES, the force generated by the PES was the same as the generator. This paper is the first step to implement a hardware-based PES, and we confirmed that the output characteristics of the 10MW HTS generator and the proposed PES are the same. The PES can also be used to estimate support stresses and strains of large-scale HTS generators and will be used effectively in future research and manufacturing of large-scale HTS wind turbines.

Speaker: Mr Changhyun Kim (Changwon National University)

MT_Presention_Changhyun_Kim.pdf

826 Thu-Mo-Po4.06-07 [45]: A Novel Thermal Network Model for Double Stator Brushless Doubly-Fed Generator With Cage-Barrier Rotor Based on Improved Mechanical Structure

In order to improve the power density and efficiency of the existing generator for wind power generation, a novel double stator brushless doubly-fed generator with back-to-back cage-barrier rotor has been presented not long ago. However, the accident of toughing between inner stator and rotor inner cage-barrier has been found in the process of experiment for prototype, which results in large surface scratches on the surfaces of inner stator and rotor inner cage-barrier and a smell of burning. In order to solve this problem, the original mechanical structure has been improved in this paper. In addition, in view of the rich magnetic field harmonics existing in this new type of generator obtained by the electromagnetic field calculation, which results in generating large losses, and also because of its compact structure which makes the heat dissipation difficultly, it brings in the risk of high temperature. So it is necessary to analyze the heat transfer rules between internal structure parts before designing the cooling system subsequently. For this purpose, a novel thermal network model for the entire generator structure and thermal resistance calculation mathematical modals between special structural parts are proposed for temperature rise calculation based on the improved structure. Finally, the rationality of improved structure scheme and the correctness of the thermal network model are verified by finite element simulation and experimental study.

Speaker: Prof. Fengge Zhang (Shenyang University of Technology)

MT26_poster_Fengge Zhang （Thu-Mo-Po4.06-07[45]）.pdf

Thu-Mo-Po4.07 - Magnetization and AC Losses II

Conveners: Hiroshi Ueda (Okayama University), Dr Kathleen Amm (Brookhaven National Laboratory)

827 Thu-Mo-Po4.07-01 [46]: Core Loss Characteristics and Model Verification of Nanocrystalline Alloys Under Complex Working Conditions

In order to saving energy and reducing consumption, making full development of advanced materials has been a global consensus. Nanocrystalline alloys, compared with ferrite, have high permeability, high saturation flux density and relatively low core loss. Due to the lack of magnetic properties under complex working conditions, its application in high power density applications have been limited.
Most of the existing core loss models are based on sinusoidal excitation, thus a modified loss separation formula is first introduced and discussed. In order to establish the core loss model of nanocrystalline alloys under complex working conditions, a testing platform for the magnetic properties under complex working conditions is established. Core loss under room temperature (20℃) and sinusoidal conditions is measured to verify the original loss separation (OLS) method. The accuracy of loss separation method is improved by modifying the loss separation formula. Then it is extended to the modified loss separation method, which is suitable for prediction of core loss complex working conditions. On this basis, calculated and experimental results under complicated conditions with different ambient temperature and excitation waveform are compared. The results show that the core loss difference between the calculation and the measurement is very small, which verify the accuracy of the modified loss separation model. At the same time, compared with the existing models, this modified loss separation model has a certain improvement in calculation accuracy.

Speaker: Dr Chengcheng Liu (Hebei University of Technology)

828 Thu-Mo-Po4.07-02 [47]: Transverse field measurements in a bulk superconducting Magnetic Shell for a CLAS12 Target at Jefferson Lab

Prototype tests are underway to study the feasibility of using a bulk magnetic system to maintain a transversely polarized target within the longitudinal solenoid of the CLAS12 detector, during an experiment to measure transverse spin effects in semi-inclusive deep inelastic scattering (SIDIS) at 11 GeV. The experiment has been approved with the highest priority rating at Jefferson Lab. The main CLAS12 detector solenoid would be operated with a maximum magnetic induction of 2 T. A bulk MgB2 cylinder cooled in liquid helium is proposed both to shield this longitudinal field as well as to provide a transverse field induction up to 1.2 T to maintain the orientation of a solid hydrogen deuteride (HDice) polarized target. A test setup to measure the transverse magnetization of a MgB2 bulk cylinder cooled by a coldhead has been developed. Transverse field measurements have been performed over a wide range of temperatures in two configurations, cooling past the critical point in the presence of an external field to trap a transverse field within the MgB2, and shielding an external field that is applied after cooling. Results of these studies will be discussed.

Speaker: Marco Statera (INFN Milano - LASA)

poster_MT26_2019_MgB2_statera.pdf

829 Thu-Mo-Po4.07-03 [48]: Magnetic Measurements of MQXFA Prototype Quadrupoles during Magnet Assembly

The High-Luminosity LHC Accelerator Upgrade Project (HL-LHC AUP) is preparing for production of the US-contributed Q1 and Q3 Interaction Region Quadrupoles (MQXFA). These magnets are based on Nb$_3$Sn conductor and need to satisfy stringent requirements for operation in HL-LHC. Magnetic field measurements are performed during magnet assembly to monitor key parameters such as integrated quadrupole, magnetic axis, field angle, higher order harmonics and to correct the field errors with magnetic shims if needed. This paper presents the magnetic measurements and analysis of the most recent prototype (MQXFAP1b) which includes one new coil and three coils previously tested in MQXFAP1. The results are compared with HL-LHC requirements, numerical calculations and measurements from a previous prototype (MQXFAP2) and several short models. Project plans for assessing magnet field quality and applying corrections at the assembly stage are reviewed in light of these results.

Speakers: Xiaorong Wang (Lawrence Berkeley National Laboratory), GianLuca Sabbi (LBNL)

wm_poster.pdf

830 Thu-Mo-Po4.07-04 [49]: A simplified electromagnetic modelling of accelerator magnets wound with Conductor on Round Core wires for ac loss calculations

Conductor on Round Core (CORC(R)) wires are attractive for applications to accelerator magnets because of their large current capacity and mechanical flexibility. Because accelerator magnets are sometimes required to generate time-dependent magnetic field, ac losses and their distributions in the magnets can be problems. Because coated conductors composing CORC(R) wires have three-dimensional geometry, calculations of ac losses of coated conductors in CORC(R) wires composing accelerator magnets are quite difficult.
In order to calculate ac losses in magnets wound with CORC(R) wires, we develop simple three-dimensional electromagnetic field analysis model. In our model, at first, magnetic field seen by a cross section of a CORC(R) wire is calculated with simple three-dimensional geometry approximation. Here, instead of exact current distributions in the CORC(R) wires composing the magnet, uniform current distribution in cross sections of the three-dimensionally wound CORC(R) wires in the magnets are assumed. Second, three-dimensional magnetic field distribution in coated conductors composing the single CORC(R) wire is calculated from the two-dimensional magnetic field distribution at the cross section of the CORC(R) wire. Here, the calculated magnetic field distribution in the cross section of the CORC(R) wire is assumed as uniform along longitudinal direction of the CORC(R) wire. Third, three-dimensional electromagnetic field analysis is conducted for the CORC(R) wire, and the ac loss is calculated.
We apply this model to a magnet for a rapid cycling synchrotron. The magnet contains HTS deformed racetrack coils wound with 6-strand CORC(R) wires and an iron yoke. The ac loss distributions at some different parts of the magnet are discussed based on the calculated magnetic field and current density distributions in the cross sections of the CORC(R) wires

This work was supported in part by the Ministry of Education, Culture, Sports, Science and Technology under the Innovative Nuclear Research and Development Program.

Speaker: Dr Yusuke Sogabe (Kyoto University)

MT26_S-inov_poster_draft_rv6.pdf

831 Thu-Mo-Po4.07-05 [50]: Field Quality Measurements of High-Temperature Superconducting Canted Cosine Theta Accelerator Magnets

High-temperature superconducting (HTS) composites are being considered for use in high-field magnets for future particle accelerators, as they allow the development of very high field dipoles and quadrupoles. As part of the US Magnet Development Program, LBNL is developing Bi2212- and REBCO-based insert magnets towards 20 T hybrid dipole magnets. The field quality of the magnets is important to assess and limited reports on HTS accelerator magnet field quality measurements are available. Furthermore, drift in the field quality resulting from flux creep in HTS is an important consideration. Here we report on field quality measurements of insert magnets measured at 77 and 4.2 K, self-field. The insert coils were based on canted cosine theta design and were wound with Bi2212 Rutherford cables and REBCO CORC® wires. Hall sensors and rotating coil fluxmeters were used to measure the generated magnetic field harmonics and their evolution with time. The magnetization and decay data from M-µ0H measurements performed, at 4 K, on samples of cables of the HTS composites were used as inputs to finite element and analytical models to predict the field error of a magnet made from the cables. The data was taken in fields up to 8 T. We compare the results of the field quality measurements to calculated results from models based on the short cable sample magnetization data results. The study allowed us to better understand the field quality issues in HTS magnets and to provide important feedback on the conductor development and strategies to improve the field quality of emerging HTS accelerator magnets.

Speaker: Cory Myers (Ohio State University)

832 Thu-Mo-Po4.07-06 [51]: Maximising the trapped field of HTS ring magnets

High-temperature Superconducting tapes with high critical currents have shown a potential to be used as high-field magnets. HTS ring magnets have been proposed to use as a trapped field magnet with persistent current flowing in them after magnetization. The advantage over conventional HTS bulks is that the HTS ring magnet can be flexible in size and easy to build. This work focuses on optimizing the HTS ring magnet design and maximizing its trapped field. Several ring magnets have been made and magnetized using zero-field cooling at 20-30 K. We report the experimental measurements for the persistent currents in these ring magnets, as well as their decay. 2D H formulation has been used to calculate the trapped fields of the ring magnets and compared to experimental results.

Speakers: Dr Min Zhang (University of Strathclyde), Dr Yanwei Wang (University of Strathclyde)

833 Thu-Mo-Po4.07-07 [52]: AC Loss of Superconducting Materials- refined loss estimates for very high density motors and generators for hybrid-electric aircraft: MgB2 wires, Coated conductor tapes and wires

Superconducting winding are enabling for the development of the highest power density motors and generators for aircraft use. It is presently estimated that motors with normal conducting can reach a future limit of at best 20 kW/kg. On the other hand, superconducting winding are estimated to be able to produce more than double this, at 45 kW/kg. Superconducting windings carry very large current densities (1 kA/mm2 winding Je and more) and can generate much higher winding fields (even as high as 3-8 T in some designs), but do generate losses in the windings which must be removed at cryogenic temperatures. Here we compare loss values under realistic design constraints for the two most appropriate conductors for motor-generator applications; MgB2 and YBCO coated conductor. MgB2 is available in the form of wires (about 1 mm OD), and coated conductor either as tapes (4 mm x 0.1 mm) or wire-sized cables (2-3 mm OD). Here comparisons are made with best of class MgB2 and YBCO conductors where various loss contributions are incorporated, including applied fields, applied currents, and interaction terms. It is shown that present day MgB2 conductors are usable for motors and generators with sufficient attention to cooling design, and that filament numbers of 10-100 in a 2 mm wide YBCO tape will make it a viable candidate for use. YBCO coated conductor in the form of small wires is also quite promising, with low reductions due to twisting. Specific loss values are very dependent on rotational speed, number of poles, and conductor design, but detailed and specific losses are given for frequencies of 200-400 Hz and field amplitudes from 0.5-4 T, as well as scaling rules to extend these regimes. We in particular include here also the effect of maximum field amplitude variation in the windings, and include for the conductors a semi-bean approximation which allows for more realistic loss modelling results.

Speaker: Prof. Mike Sumption (The Ohio State University)

834 Thu-Mo-Po4.07-08 [53]: Coupling time constants measurements of spirally-wound striated coated conductors

Striation is one of the approaches to reduce ac losses and shielding-current-induced fields (SCIFs) in conductors or coils made with coated conductors. If filaments in a striated coated conductor are decoupled, the magnetization of the coated conductor is reduced, and, then, the ac loss as well as the SCIF is reduced. Striated coated conductors can be classified into two types: one in which superconductor filaments are insulated electrically and another in which superconductor filaments are not insulated electrically. If filaments are transposed ideally, filaments are decoupled ideally in the former. However, from the viewpoint of current sharing between filaments, which improves the robustness of coated conductors against quench / thermal runaway, the latter is preferable.
In this presentation, we focus on striated coated conductors in which filaments are not insulated electrically. It should be noted that the striation is effective only when a striated coated conductor is twisted. However, twisting a tape-shaped coated conductor is not practical. Instead of twisting, numerical analyses suggested that winding a striated coated conductor on a round former like CORC wire is effective to decouple filaments. We prepare striated coated conductors in which filaments are insulated electrically. Then, we fabricate sample pieces of striated coated conductors in which filaments are not insulated electrically as follows: depositing melted indium on filaments; soldering copper film on filaments. Such a sample piece is wound on a round GFRP former, and the frequency dependence of its magnetization loss is measured to determine its coupling time constant: from the peak of "magnetization loss vs. frequency" plot, we can determine the coupling time constant. At first, measurements were done with an indium-deposited striated coated conductor which was wound on a round GFRP former. The determined coupling time constant showed effect of spiral geometry to decouple filaments.

This work was supported in part by the NEDO in the Project for the Promotion to the Commercialization of High-Temperature Superconductivity Technology.

Speaker: Yang Li (Kyoto University)

Thu-Mo-Po4.07-08[53].pdf

Thu-Mo-Po4.08 - Wind, Wave, Tidal Generators - I

Conveners: Neil Mitchell (ITER Organization), Dr Tatsushi Nakamoto (High Energy Accelerator Research Organization, KEK)

835 Thu-Mo-Po4.08-02 [54]: Performance analysis of a metal-insulation type lab-scale HTS wind power generator

High Temperature Superconducting (HTS) generator for a large-scale wind power generation system draws much attention as a contemporary research item. Metal-Insulation (MI) technique greatly enhanced the thermal stability of the coil without requiring complicated protection against quenching because quench currents are bypassed through the turn-to-turn contacts, ultimately improving the mechanical integrity of the HTS pancake coil. However, there is still a question whether this technique can be applied to racetrack coils for HTS superconducting generator.
This paper deals with the performance analysis of a MI type lab-scale HTS wind power generator and examines application possibility of the MI type generator for wind turbines through hardware integration.
Total 6 double pancake coils considering MI such as stainless steel tape were fabricated. Therefore, a 5 kW class HTS generator consisted of 6 poles with MI type for the rotor. And, 36 slots copper windings for stator was designed and fabricated for the generator. The HTS coils were mounted in a vacuum vessel integrated into the rotor, and cooled down by thermosyphon cooling method with a cryogenic refrigerator.
Through the physical fabrication of the machine, we confirmed several important results as follows. The rated output power of the generator reached to 5 kW at 400 rpm, and the operating temperature was maintained at 30 K by the cooling method. The operating field current was 200 A at operating temperature. Charge-discharge and over-current tests of the MI type field coils were performed. The field coils were successfully charged with full field performance and discharged when the operating current was below its critical current value. In the case of the over-current test, the coils operated stably because the over-current was automatically diverted through the turn-to-turn contacts. The MI type coils showed enhanced thermal and electrical stabilities during over-current testing. The results will be utilized to practical design with better thermal and electrical stabilities for a large-scale HTS generator.

Speaker: Hae-Jin Sung (Changwon National University)

836 Thu-Mo-Po4.08-03 [55]: Characteristics Analysis of Fully HTS Synchronous Generators with Dual Field Windings

The superconducting synchronous generator is one of the breakthrough elements for direct-drive wind turbine because it is light and small. Normally the superconducting one has copper armature windings in the stator and superconducting field windings on the rotor. The electrical frequency of the output voltage of the direct-drive generator is very low, so the total length of the armature windings should be long for the rated line voltage. The high resistance of the armature can make large copper losses, comparing with the conventional generators with a gear box.
One of the solutions for the large copper losses could be the fully superconducting generators. But the high magnetic fields from the superconducting field windings on the rotor also make high perpendicular magnetic fields on the superconducting tapes in the armature windings. We have proposed a fully superconducting synchronous generator with dual field windings. It could immensely decrease the circumferential component of the magnetic field from the field windings at the armature windings.
In this paper, we conceptually designed 4 types of superconducting synchronous generators. The first one is normal superconducting one with only superconducting field windings. The second one is the fully superconducting one with conventional structure, which has superconducting armature windings in the stator and superconducting field windings on the rotor. The third one is the one with dual superconducting field windings and superconducting armature windings between them. The last one is the same as the third one except the structure of the armature. If the concentrated armature windings are superconducting ones with cryostats, then they cannot be installed within the span of 2 poles. So, we adopted 3 phases windings within 4 poles system. It makes more AC losses but can be manufactured really. We compared the AC losses of the 4 superconducting generators and analyzed their electrical characteristics.

Speaker: Myeonghee Lee (KoreaPolytechnicUniversity)

MT26_dualfield_v1.0.pdf

837 Thu-Mo-Po4.08-04 [56]: Electromagnetic Design of HTS DC Generator with Iron-cored Stator and Rotor

Offshore wind energy is going to take the dominated place in renewable energy due to it abundant and steady wind resource. To reduce the levelized cost of energy, the large power rate, even above 10 MW, wind generators are preferred for offshore wind farms. Compared with conventional wind generator such as induction generators and permanent magnet generators, high temperature superconducting (HTS) wind generators are lighter and smaller in size due to the much high magnetic loading produced by HTS coils. Therefore, HTS wind generator becomes a potential candidate for future offshore wind market and attracts attentions of researchers.
An HTS DC generator with ironed stator and rotor is proposed for offshore wind turbine. Unlike the traditional DC generator, the armature windings of proposed generator are equipped in the outer rotor. This structure can obvious improve the line load and torque density. HTS field coils are fixed on the inner stator and modular cryostat structure is considered in this topology. The double iron structure, as well as the modular cryostat, reduces the magnetic reluctance of this machine, which can effectively reduce the cost of HTS material with the same magnetic loading.
This paper designs and analyzes a 10MW HTS DC generator. The electromagnetic performances of proposed HTS DC wind generator are investigated by using the finite element method (FEM). In addition, the feasibility and practical value are evaluated by quantitative comparison with the same scale HTS synchronous wind generator in term of the electromagnetic performance, weight, volume and active material cost. The results show that the proposed HTS DC generator is quite comparable to the HTS synchronous wind generator.

Speakers: Ms Qian Wang (Huazhong University of Science and Technology), Prof. Ronghai Qu (Huazhong University of Science and Technology), Mr Yi Cheng (Huazhong University of Science and Technology), Dr Yuting Gao (Huazhong University of Science and Technology)

Thu-Mo-Po4.08-04 [56].pdf

838 Thu-Mo-Po4.08-05 [57]: Presentation withdrawn

839 Thu-Mo-Po4.08-06 [58]: Electromagnetic Design of an HTS Claw Pole Wind Generator

Nowadays, wind energy is developing rapidly as it is clean and renewable and the offshore wind energy is one of the most popular ones for its abundant source. To avoid frequent maintenance of the offshore wind turbine system, a large direct-drive generator is needed. Due to the advantages of the higher magnetic field in the high temperature superconducting (HTS) machine compared to that of the regular one, it becomes a great candidate for offshore wind power application for its large torque density. However, the cost of the HTS material is very high and it limits the industrialization of the HTS wind generator.
In this paper, a 10 MW HTS claw pole wind generator is designed. This generator adopts claw pole machine topology with HTS toroidal winding. Two excitation coils are used to create a magnetic field that is directed to the air gap by the C-type teeth. Compared to the conventional HTS generator, its structure is simpler with a stationary cryogenic system and it consumes less HTS materials as it has a relatively shorter end winding. What’s more, the excitation magnetic field in the core is still, which means it will have lower core losses.
The design and optimization of the HTS axial-flux generator are investigated by finite-element analysis. Firstly, the basic electromagnetic performance of this new topology is calculated by the finite-element method. Then, several optimizations such as decreasing its torque ripple are conducted and clarified by the finite-element analysis. At last, its electromagnetic performance is compared with the existing three-phase HTS synchronous generator. The comparison results show that the HTS material used reduces by 30% in this topology, which means a big decrease in the cost of the wind turbine system.

[1] Keysan O , Mueller M A . A Homopolar HTSG Topology for Large Direct-Drive Wind Turbines[J]. IEEE Transactions on Applied Superconductivity, 2011, 21(5):3523-3531.

Speakers: Yuanzhi Zhang (Huazhong University of Science and Technology), Yuting Gao (Huazhong University of Science and Technology), Yi Cheng (Huazhong University of Science and Technology)

MT26--Thu-Mo-Po4.08-06 [58].pdf

MT26--Thu-Mo-Po4.08-06 [58].pptx

840 Thu-Mo-Po4.08-07 [59]: Electromagnetic design of tens MW-class fully-superconducting wind power generators with high-performance REBa2Cu3Oy wires

Fully-superconducting generators with compactness and lightweight are promising candidates for direct-drive multi-mega-watt offshore wind turbines due to its high current density properties. The compactness and lightweight design should bring about the cost reduction of nacelles, towers and foundations. Furthermore, high-performance REBa2Cu3Oy (REBCO: RE = rare earth) tapes and the reduction method of AC losses which our research group have developed should contribute to realize tens MW-class fully superconducting wind power generators. The developed REBCO tapes have a large critical current in high magnetic fields at a wide range of operating temperatures (20-77 K), which leads to the reduction of wire length and cost. The high-performance REBCO tapes also makes it possible to operate the superconducting windings at a high temperature of 65 K via subcooled-liquid nitrogen. It also brings about high stability of the system due to its high specific heat. The objective of this study is to study the feasibility of large-capacity over 10 MW wind power generators employing the high-performance REBCO windings both on rotor and stator in the view point of cost, weight and efficiency. 10-20 MW fully-superconducting synchronous generators are designed using finite element analysis. 15 MW-class generators with 32 poles, an operating temperature of 40 K and magnetic flux density at the gap of 2 T were designed. The electrical weight of this model is below 100 tons which is much lighter than that of a conventional synchronous generator (300-400 ton).

Acknowledgement
This work was partly supported by Grants-in-Aid for Scientific Research (JP17H06931 and JP18H03783) from the Japan Society for the Promotion of Science (JSPS), JST-ALCA and Nagamori Foundation 2018.

Speaker: Dr Shun Miura (Kyushu University)

841 Thu-Mo-Po4.08-08 [60]: Presentation withdrawn

842 Thu-Mo-Po4.08-09 [61]: Investigation of multi-phase armature windings in HTS wind turbine generators

A high torque density enables high temperature superconducting (HTS) generators to be a strong candidate for lightweight, efficient and cost-effective large direct-drive (DD) wind turbines, especially for the next-generation floating wind turbines where a less top head mass is appreciated.
It is very common that 3-phase armature windings are used in HTS generators. One consequence is that AC losses induced in field windings must be well handled, by adding more cooling power or by employing an electromagnetic shield or by increasing the air gap to reduce the influence of armature windings on field windings. One feasible solution to reduce AC losses induced in field windings is to use multi-phase armature windings, which on one hand have fewer harmonics and less influence on field windings and on the other hand help to reduce the probability of sudden short circuits at generator terminals.
This paper comparatively studies effects of 3-phase, 6-phase, and 12-phase armature windings in an HTS wind turbine generator. For a fair comparison, AC losses in the HTS field winding are set to the same value. The results show that the 6-phase and 12-phase armature windings reduce the air gap by 7% and 16%, respectively. The reduction of the air gap corresponds to a torque density improvement of 11 % and 19%. The findings of the paper expand the border of designing of high-torque-density HTS wind turbine generators.

Speaker: Dr Dong Liu (Hohai University)

poster for MT26 paper 2 v2.pdf

843 Thu-Mo-Po4.08-10 [62]: Presentation withdrawn

Thu-Mo-Po4.09 - Joints Between Superconductors

Conveners: Dr Jun Lu (FSU/NHMFL), Dr Shintetsu Kanazawa (Muroran Institute of Technology)

844 Thu-Mo-Po4.09-01 [63]: Joint properties for RE123-coated conductor in CJMB method

The joint between two RE123-coated conductors with crystalline joint by melted bulk (CJMB) method [1, 2] has been developed for NMR and MRI. In this method, a Yb123 sheet is used between the coated conductors as a superconducting intermedium. We reported that a superconducting joint with critical current of 21.2 A at 77 K was obtained, and the persistent coil has a low resistance about 1 pΩ in 77 K. However, the critical current is still small that is one tenth of original coated conductor. In this study, we investigated microstructure and critical current of joint to clarify the joint mechanism, toward realization of a high critical current above 100 A at 77 K. The critical current of Yb123 sheet before joint is 7-16 A along c-axis (vertical direction of tape surface), which value is the same with that for the joint using one bulk. Multiple junctions using multiple Yb123 sheets are necessary to increase the critical current that can be greatly improved by using many Yb123 sheets, such as several tens, but it is important to prevent degradation of the coated conductor itself during heat treatment of joint. If there is no deterioration of the coated conductor, the same critical current as original coated conductor can be obtained in joint. Therefore, the measurements of critical current and microstructure for the coated conductor after heat treatment is important in current study. The obtained results will be presented in MT26 at Vancouver.

Acknowledgements:
This work was supported by JST-Mirai Program Grant Number JPMJMI17A2, MEXT project of Leading Initiative for Excellent Young Researchers (LEADER) Project ID 16810210, and JSPS KAKENHI Grant Number JP18K04719, Japan.

[1] Xinzhe Jin, Yoshinori Yanagisawa, Hideaki Maeda and Yoshiki Takano, Superconductor Science and Technology 28 (2015) 075010 (6pp)
[2] Xinzhe Jin, Yoshinori Yanagisawa, and Hideaki Maeda, IEEE Transactions on Applied Superconductivity 28 (2018) 4602604 (4pp)

Speaker: Dr Shintetsu Kanazawa (Muroran Institute of Technology)

Thu-Mo-Po4.09-01 [63].pdf

845 Thu-Mo-Po4.09-02 [64]: Development and test results of a superconducting joint resistance evaluation system

Superconducting joints are extremely important for the application of HTS magnets. Recently, various joint techniques have been proposed for connection between HTS conductors. However, suitable evaluation methods for joint resistance (R$_j$) have not been established. We have developed a joint resistance evaluation system [1]. The system consists of an HTS sample with a joint, a current injection coil, and a split-pair superconducting magnet. The HTS sample and the magnet are conductively cooled by cryocoolers. The sample is composed of a one- or several-turn closed-loop. R$_j$ of the sample is evaluated by a decay of the induced current in an LR closed circuit. Using the system, the joint resistances ranging 10$^{-14}$-10$^{-7}$ $\Omega$　were quantitatively evaluated as a function of current magnitude, temperature, magnetic field and its orientation. In this paper, we report the commissioning results of the system and some latest joint resistance evaluation results.

This work is based on results obtained from a project commissioned by the New Energy and Industrial Technology Development Organization (NEDO) [No.16100555-0] and JST-Mirai Program Grant Number JPMJMI17A2, Japan.

[1] K. Kobayashi et al., Supercond. Sci. Technol. to be submitted.

Speaker: Kensuke Kobayashi (National Institute for Materials Science)

Thu-Mo-Po4.09-02_kobayashik.pdf

846 Thu-Mo-Po4.09-03 [65]: Evaluation of Joint Resistance and Electromechanical Properties in Various Type of Ultrasonic Weld CC Tape Joints

Various types of coated conductor (CC) joints are required due to current CC tapes fabrication limited lengths and for their coil applications in high field magnets. It is essential that some CC joint fundamentals, including joint resistance, must be a consideration in dealing with such application designs. Also, joint requirements must meet both the conditions of good electrical and mechanical interconnections. In this study, ultrasonic weld (UW) joints of differently stabilized REBCO CC tapes were fabricated. Joint resistance (Rj) and critical current (Ic) measurements of adopted CC tapes depending on UW types/configurations were measured at 77 K. Bending performance of CC bridge joints as a practical evaluation for coil winding application were measured and discussed. The results of different UW joints provide an understanding on the UW type-joint resistance and electromechanical properties relationship. Surface morphologies of the cross-section and joint interface were observed using SEM, EDS, and EPMA.

This work was supported by the Korea Electric Power Corporation. (Grant number: R18XA03). This research was also supported by a grant from the National Research Foundation of Korea (NRF-2017-001109), funded by the Ministry of Science and ICT (MSIT), Republic of Korea.

Speaker: Dr Michael de Leon (Andong National University)

MT26_manuscript 2_UW of CC tapes (Poster)_Final.pdf

847 Thu-Mo-Po4.09-04 [66]: Investigations on the synthesis and melt-growth process of low melt temperature REBCO materials

The low melt temperature REBa2Cu3O7-δ (LMT RE123, RE=Yb, Er, etc.), a candidate of the joint materials, is essential to acquire superconducting joint of the 2nd HTS tape, which could be used in extreme high field NMR (≥25T). In this paper, two LMT RE123 materials have been synthesized. The synthesis parameters have been optimized to obtain RE123 materials with high superconducting properties. The effect of the Ag and Pt doping on the melt point of LMT RE123 materials is uncovered. The melt and growth process of the LMT RE123 materials have been systematically delved, in order to explore a feasible heat treatment process of superconducting joint. This work provide an important start point to fabrication superconducting joint of the 2nd HTS tapes, which will highly promote the application process of extreme high field NMR.

Speaker: Dr Zili Zhang (Institute of Electrical Engineering, Chinese Academy of Sciences)

848 Thu-Mo-Po4.09-05 [67]: Research of Nb3Sn superconducting joint by powder metallurgy

A novel Nb3Sn superconducting jointing method by means of powder metallurgy was presented to reduce the resistance for purpose of satisfactory magnetic field stability of high field NMR instrument. In this research, Nb, Sn and Cu element powders were introduced in ball milling processing to prepare the (Cu, Sn) solid-solution before pressing and sintering. The A – 15 type Nb3Sn phase was generated from the element powders during heat treatment. This jointing method is with the character of quick and high quality metallurgical bonding between the Nb3Sn filaments of wires by means of in-situ Nb3Sn phase. The crystal structures and microstructures of the joint were investigated by X-ray diffraction (XRD), Energy-dispersive X-ray spectroscopy (EDX) and scanning electron microscope (SEM) respectively. The critical performance of sinter was also tested by Physical Property Measurement System (PPMS). The joint resistance was measured in the liquid helium condition by the coil current decay method. The results show that the resistance of the joint was decreased sharply in comparison with the soldering and cold-pressing welding methods.

Speaker: Dr Junsheng Cheng (Institute of Electrical Engineering, Chinese Academy of Sciences)

849 Thu-Mo-Po4.09-06 [68]: Progress on the Superconducting Joint Technique for the Reacted MgB2 Wires for MRI Magnet Development

A superconducting joint technique has been extensively investigated to operate magnetic resonance imaging systems in persistent current mode, which enables a high-resolution level of the magnetic field. We have presented the MgB2 superconducting joint with unreacted MgB2 wires that demonstrate the feasibility of the joint technique to be utilized for the MgB2 MRI magnet development. However, when failure occurred at the already reacted MgB2 joints and/or wires, the reproduction of the joint using the unreacted joint technique cannot be achieved. Therefore, the superconducting joint technique for the “reacted” MgB2 wires fabricated via a powder processing method using Mg and B powders (in situ) and reacted MgB2 powders (ex situ) has been examined in this study. In addition, a lab-made induction furnace that allows the local heating of the joint region was fabricated and utilized for the joint procedure. The superconducting properties (i.e., critical current and index number) of the joint were evaluated with regard to heat treatment temperature and treatment duration time.

[Acknowledgement]
This work was supported by the Materials and Components Technology Development Program of KEIT [10053590, Development of MgB2 wire and coil with a high critical current and long length for superconducting medical·electric power equipment].

Speaker: Mr Byeongha Yoo (Korea University)

Thu-Mo-Po4.10 - Current Leads

Conveners: Bartlomiej Glowacki (University of Cambridge), Mike Sumption (The Ohio State University)

850 Thu-Mo-Po4.10-01 [69]: Comparative study of cryogenic NbTi/Cu and MgB2/Brass based current leads

SST-1 is a medium size superconducting (SC) tokomak operational at IPR in India. TF and PF sc coils are used to produce high magnetic field strength. Presently, 10 kA rated Vapour cooled current leads (VCCLs) for TF system is made of NbTi superconductor and copper heat exchanger. Similarly, 9 PF coils will be energised by individual power supplies requiring total 18 VCCLs under pulse operations up to 9 kA. VCCLs utilize 55% of total cryogenic plant capacity (1.3 kW at 4.5 K). Consequently, it has been envisaged to minimize the liquid helium consumption by an innovative solution to save cryogenic power with alteration of materials in the current lead specific to pulse operation. This approach adopts two folds savings, i.e. introducing MgB2 sc in lieu of NbTi and the heat exchanger material as brass instead of copper, which has more specific heat, lower thermal conductivity and higher melting temperature compared to copper. Moreover, brass can also be overloaded. MgB2 provides better temperature margin as compared to NbTi. In temperature range of 20 K – 40 K, cryo plant offers the best exergy efficiency. It has been established that the combination of MgB2 and brass based current leads have several advantages over the existing VCCLs. To support this statement, a prototype experiment was conducted using a dedicated test cryostat in which both types of current leads were installed and tested up to 1.5 kA. This test involves cryostat, current leads, feeder link, hydraulic network, 12 kA/16 V switch mode power supply, sensors and data acquisition system. This paper highlights the test set-up details and experimental results along with comparison of liquid helium consumption between NbTi/Cu and MgB2/brass current leads to assess the operational cost. It also discusses the cryo benefits of MgB2 based brass current leads.

Speaker: Mr Atul Garg (Institute for Plasma Research )

Thu-Mo-Po4.10-01-Abstract ID 1399.pdf

851 Thu-Mo-Po4.10-02 [70]: Comparison Analysis of Three Different Structures of Current Leads for the Superconducting Energy Pipeline

Current lead’s Joule-heating and conduction losses are main parts of superconducting cable’s cryogenic system total heat load. Superconducting energy pipeline is a new type of hybrid superconducting energy transmission cable, and the heat leakage of its current lead is not negligible.
In this paper, the process of superconducting energy pipeline current leads design, optimization and scale-down models’ cryogenic tests are presented. Quasi-analytical numerical method was used to design cylindrical, rectangular and variable cross-section forms current leads. To verify the validity of the designed schemes, a heat leakage measurement platform for current leads was built. Evaporated nitrogen and current lead’s temperature profile in Dewar were measured to calculate current lead heat leakage. Compared with the conventional cylindrical current lead, rectangular current lead and variable cross-section current lead both can reduce heat leakage.

Speaker: Mr Xianhao Li (Huazhong University of Science and Technology)

presentation.pdf

852 Thu-Mo-Po4.10-03 [71]: Thermal Design and Test of 4kA Current Lead based on Stacked YBCO Conductor

For the Beijing Spectrometer III (BESIII) superconducting magnet alternate upgrade project, two 4kA HTS current leads were designed, manufactured and tested. The baseline design of the current leads adopted a stacked YBCO conductor solution to achieve a lower thermal load at 4K, improve the stability of the magnet, and meet the requirements in the upgrade project that the unchanging of existing cryogenic system and of the internal space of valve box. This paper introduces optimized design of the fin resistive heat exchanger component using fluid dynamics simulation, and thermal analysis of the entire current lead. Owing to the adoption of YBCO conductor, the heat leakage was effectively controlled. The joint component connected the LTS cable adopted a conduction-cooled design, which avoided complicated liquid helium piping and made the entire current lead structure simpler. The development of a novel YBCO soldered stacked conductor is also described. Their thermal conductivity and electrical properties tests, and experimental results of the entire current lead are discussed.

Speakers: Zongtai Xie (Institute of High Energy Physic, CAS), Feipeng Ning (IHEP)

CL poster.pdf

853 Thu-Mo-Po4.10-04 [72]: Finite Element Analysis and Experimental test of current leads with parallel HTS tapes

The design, analysis and experimental test of a High Temperature Superconductor (HTS) current leads with parallel HTS tapes is presented. Two HTS tapes are electrically shunted in parallel in each positive and negative lead respectively to increase its current-carrying capability. It is essential to enable balanced current sharing between the parallel HTS tapes to prevent potential overload and quench of each HTS tape. Finite Element Analysis has been conducted to investigate the current distribution of parallel HTS tapes under the impact of various design parameters, including the geometry of copper terminals, solder interface length/thickness and solder resistivity. Analysis concludes that the electrical resistance from copper terminal to each of the parallel HTS tapes need to be relatively close to balance the current sharing between two tapes. Making the copper terminal electrical resistance dominantly greater than the solder interface resistance would result in a robust current leads design with least negative impact caused by soldering process. The FEA simulation meets well with prototype HTS leads test results.

Speaker: Dr Anbo Wu (GE Global Research)

854 Thu-Mo-Po4.10-06 [73]: Presentation withdrawn

Thu-Mo-Po4.11 - Current Limiters & Breakers

Conveners: Neil Mitchell (ITER Organization), Dr Tatsushi Nakamoto (High Energy Accelerator Research Organization, KEK)

855 Thu-Mo-Po4.11-01 [74]: Analysis on Protection Coordination of Over-Current Relay Using SFCL’s Impedance Compensation for Protection of a Power Distribution System

Recently, the magnitude of the fault current in the grid has been increased due to the development of the electric power industry and the increase of the distributed power generations. Since the increase of the fault current may cause a bigger accident than the capacity of the existing installed protective equipment, it is necessary to replace the protective device with a larger capacity or reduce the magnitude of the fault current. However, replacing protective devices requires astronomical costs, so a superconducting fault current limiter(SFCL) that has been studied as an effective way to limit fault currents should be used. The SFCL has a characteristic that limits the fault current in 1/4 cycle without causing loss in the system because the impedance is normally zero. However, when the SFCL is installed in the power distribution system, the fault current is lowered, which causes the trip delay of the installed over-current relay. Also, when the distributed power source is introduced, the magnitude of the fault current increases or decreases depending on the location of the distributed power generation and the fault location, and reverse current may occur depending on the situation. This is a problem not only in the introduction of the distributed generations of the radial system but also in the loop system.
In this paper, the SFCL’s impedance factor is used to solve the trip delay of the over-current relay. In order to compensate the problem, the SFCL’s impedance factor is used because the trip delay method uses the previously studied SFCL’s voltage factor and the correction constant must be changed according to the fault location. The bus line current and the voltage of the SFCL are used to reflect the SFCL’s impedance factor, and they are all measured, so there is no need to install additional measuring instruments. Therefore, an over-current relay using SFCL’s impedance factor with these advantages was simulated and analyzed by PSCAD EMTDC.

Speaker: Prof. Sung-Hun Lim (Soonsil University)

190922_MT26-Thu-Mo-Po4.11-01_Analysis on Protection Coordination of Over-Current Relay ~.pdf

856 Thu-Mo-Po4.11-02 [75]: Presentation Withdrawn

857 Thu-Mo-Po4.11-03 [76]: Design and Performance Evaluation of a REBCO NI-SFCL applied in Short-Circuit Faults Occurred in 350 kV Flexible DC transmission

Recently, flexible DC transmission has been developed rapidly in the Off-site grid interconnection. Inhibiting the sudden increase of DC current caused by short-circuit faults is necessary for the protection of power grid. Generally, the short-circuit faults may be caused by physical conduction or arcing and sparking. To address permanently damage the power grid, a resistance type high-temperature superconducting (HTS) short-circuit fault current limiter (SFCL), which has the advantages of large capacity, low conducting loss and simple structure, has been proposed. However, because this conventional SFCL s based on 1st generation BiSCCO HTS material lacks of thermal stability and mechanical strength, it may easily burn out owing to the thermal runaway during a quench. Moreover, the conventional resistance SFCL is also reported that needs several seconds recover from a quench.
Hence, we proposed a new resistance type REBCO SFCL based on using no-insulation (NI) winding technology. The NI coil is reported that have many excellent features: 1) hardly burn-out during an overcurrent; 2) self-protectable, never need to be paralleled a protective resistance; 3) voltage division characteristic during an overcurrent. Based on these advantages, the SFCL adopted NI winding technique is expected to inhibit the temperature increase during an overcurrent and substantially enhance the reliability itself. Hence, the NI-SFCLs becomes reusable and its recovery time can be shorter.
In this study, we designed a NI-SFCL applying in 350 kV flexible DC transmission based on numerical simulation. The feasibility of designed NI-SFCL is discussed based on the investigation of the current and voltage behaviors during short-circuit faults, boost faults and spark discharge faults. To certify the high reliability and short recovery time of NI-SFCL, we estimated the Joule-heat and the temperature during a current limiting process. Then, we also evaluate the influence of turn-to-turn contact resistance and thickness of copper stabilizer layer on voltage division and temperature increase of NI-SFCL during a current limiting process.
Key Word: Flexible DC transmission, no-insulation coil, quench, SFCL, REBCO, turn-to-turn contact resistance

Speaker: Ms Rao Jin (Nanjing University of Science and Technology)

858 Thu-Mo-Po4.11-04 [77]: Presentation withdrawn

859 Thu-Mo-Po4.11-05 [78]: Optimal Designing and Performance Evaluation of Inductive Superconducting Fault Current Limiter Combined with Low-Voltage Mechanical Circuit Breaker in DC Microgrid System

To secure the reliable dissemination of the dc microgrid system, it is essential to establish efficient protection scheme. There are various protection methods of dc microgrid system : fuse, circuit breaker (Solid-state, Mechanical, Hybrid, etc.), superconducting fault current limiter (SFCL) and fault tolerant converter. Among the mentioned methods, the mechanical circuit breaker (MCB) has the advantages of high interrupting reliability and low steady-state loss close to zero, but it has a very slow interruption time (> 30 ms) that cause serious damage and large loss to electric power equipment during fault. In this paper, to improve protection of dc microgrid system and MCB’s efficiency, we proposed the optimal designing of inductive SFCL (I-SFCL) combined with low-voltage MCB in DC microgrid system. The MCB was optimized according to the limited fault current level and improvement of the fault current interrupting performance of the MCB is verified. First, in order to select the optimal position, the one I-SFCL was located for each distributed power source and main grid in dc microgrid system. And the fault current limiting ratio and bus voltage sag were analyzed for each I-SFCL position under various fault conditions. Second, the dc CB was designed based on the voltage-current interruption curve of the actual low-voltage dc CB using the black-box arc model, and the simulation was performed each by dividing the case where the with I-SFCL or without I-SFCL. The voltage, current and loss values for each principal component in the transient area were calculated, and comparative study was performed. As a result, through the application of I-SFCL, the fault current and voltage sag in renewable sources can be effectively limited, and the interrupting performance of the MCB can be greatly improved to ensure the reliability of the dc microgrid.

Speaker: Mr Kyu-Hoon Park (Hanyang University)

MT26_Thu-Mo-Po4.11-05 [78]_Final.pdf

860 Thu-Mo-Po4.11-06 [79]: Current Limiting and Interrupting Characteristics of Flux-Lock Type SFCL with Mechanical Switch

In this paper, the flux-lock type superconducting fault current limiter (SFCL) with the mechanical switch (MS), which can be driven by self-driving coil to drive the MS unlike the previous SFCL, was suggested. The operational principle of the suggested SFCL with the MS is same as one without the mechanical switch, except that the MS is driven by electromagnetic repulsion force generated by the magnetic flux which generated between the coils comprising the suggested SFCL. To certify the operation characteristics of the suggested SFCL, the mechanical contact with the fixed plate (FP) and the moving plate (MP), which were located just above open round bobbin wound by two parallel connected coils, was designed and manufactured. The short-circuit tests of the SFCL using magnetic coupling of the coils with the suggested mechanical switch were carried out. Through the analysis on the results of the short-circuit tests, the operation time of the SFCL using magnetic coupling of the coils could be confirmed to be shortened effectively.

Speaker: Prof. Sung-Hun Lim (Soongsil University)

190922_MT26_Thu-Mo-Po4.11-06_Min-Ki Park.pdf

861 Thu-Mo-Po4.11-07 [80]: HTS Fault Current Limiting Module to Reduce Burden of a DC Circuit Breaker for 30 kV MDVC Power Grid

We have studied a DC circuit breaker with an HTS fault current limiting (FCL) module for 30 kV MDVC power grid. The attached FCL module can reduce the burden of the circuit breaker to make the system break the fault current faster as well as safer. In this paper, we will present the design of an HTS fault current limiting module with 2G REBCO conductor for the MVDC power grid with the rated voltage of 30 kV. Among several different type of 2G REBCO conductors from different suppliers, we selected the most suitable conductor, which was SuNAM’s stabilizer free REBCO conductor, based on the previous short circuit tests with sample conductors. With this material, an FCL module was designed to reduce the DC fault current from 25 kA to 1.6 kA in 2 milliseconds at most. In order to show the feasibility of the study, we fabricated a scale-down model with the selected conductor and we also carried out several short circuit tests in the low voltage testbed.

Speaker: Jooyeong So (Korea Polytechnic University)

MT26_SFCL_v1.1.pdf

862 Thu-Mo-Po4.11-08 [81]: Analysis of the recovery characteristics of superconducting coupled DC circuit breakers during reclosing operation

This paper proposes a superconducting coupled DC circuit breaker that combines a superconductor with a mechanical DC circuit breaker for DC fault current interruption. The power burden and damage possibility of superconductors are determined by the recovery characteristics of the superconductor during the reclosing operation of the proposed circuit breaker. They also affect the breaking function of the proposed circuit breaker.
This study analyzed the recovery characteristics of superconducting coupled DC circuit breakers during the reclosing operation. Superconductors RC1, RC2, and RC3 with the same critical current value were modeled and the power burdens of the superconductors were compared during the reclosing operation. The reclosing operation was based on the AC standard duty cycle.
The analysis results confirmed that the breaking time decreased by lees than 15 ms on average and the fault current decreased by 37% on average during each reclosing operation of the superconducting coupled DC circuit breaker. However, RC3 performed the reclosing operation without recovering during the reclosing operation. Due to this recovery characteristic, the power burden of RC3 increased by approximately 30% compared with RC1 and RC2.

This research was supported by Korea Electric Power corporation [grant number: R16XA01]
This work was supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIT) (No.2018R1A2B2004242)

Speaker: Mr Seon-Ho Hwang (Chosun university)

Sunho.pdf

863 Thu-Mo-Po4.11-09 [82]: Operating characteristics of arc-induction type DC circuit breaker with permanent magnets

We propose arc-induction type DC circuit breaker combining the magnets as the mechanical circuit breaker suitable for the DC system. This circuit breaker simply composes the mechanical contacts, the induction needle, the ground wire and magnets. The arc is moved the induction needle according to the Lorentz’s force and it is inducted to the induction needle. The induced arc is flowing into the ground through the ground wire and extinguished. Lorentz’s force is occurred depending on appeared arc between contacts and the magnetic field of the magnets. In this paper, we analyzed the characteristics of operating cut-off for arc-induction type DC circuit breaker combining the magnets using the Maxwell program. We studied the arc’s moving, that designed a simulation model and analyzed the flow of the electrical field according the moving the contacts. Also, we fabricated the prototype based on the simulation results and tested cut-off operation. As a results, we confirmed that the electrical force was increased about 48% in the induction needle according the combined magnets from the simulation. In addition, we got the results that the speed of the cut-off was faster about 56% according the combined magnets from the experiment.

This research was supported by Korea Electric Power corporation [grant number: R16XA01]
"This work was supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIT) (No.2018R1A2B2004242)."

Speaker: Mr Sang-Yong Park (Chosun university)

Presentation.pdf

Presentation.pptx

864 Thu-Mo-Po4.11-10 [83]: Characteristics of a Current-limiting DC circuit breaker with a superconducting coil applied to the commutation circuit

Since DC has no current zero point, an arc occurs when the DC circuit breaker performs a cuf-off operation. In this case, a fatal fault may occur in the circuit breaker or in the grid, due to the magnitude of the arc. Therefore, the cut-off operation and the reliability of the circuit breaker are important in the commercialization of HVDC. In this paper, a current-limiting DC circuit breaker combined with a superconductor coils was proposed to improve the performance and the reliability of the DC circuit breaker. The current-limiting DC CB applied a superconducting coil to the inductor of the existing a commutation circuit of DC circuit breaker. Other than limiting the initial fault current, it also creates a stable current zero point in the event of a fault current. To verify this, simulation was performed through EMTDC/PSCAD. Furthermore, the current-limiting DC CB was compared with the DC circuit breaker with a commutation circuit of normal coils.
As a result, it was found that the current-limiting DC CB with the superconducting coil limited the initial fault current further by approximately 12 kA compared to the DC circuit breaker with a normal coils. This reduced the arc extinguishing time by approximately 0.2 sec, thereby decreasing the mechanical burden on the circuit breaker.

This research was supported by Korea Electric Power corporation [grant number: R16XA01]
This work was supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIT) (No.2018R1A2B2004242)

Speaker: Ms Hye-Won Choi (Chosun University)

MT26-Thu-Mo-Po4.11-10.pdf

865 Thu-Mo-Po4.11-11 [84]: Improvement of Current Limiting and Interrupting Operation of Hybrid DC Circuit Breaker using Double Quench

In this paper, DC current limiting and interrupting operation of DC circuit breaker using double quench, which consists of DC circuit breaker (DCCB), series resonance circuit, surge arrestor and superconducting elements (SCEs), were analyzed. The suggested DC circuit breaker using double quench of SCEs can per-form twice DC fault current limiting operation in case of larger DC fault current before DC circuit breaker is open. To verify the effective operation of the suggested DC circuit breaker using double quench of SCEs, the modeling for the components of DC circuit breaker, varistor and SCE was carried out and its operational characteristics were compared with the case without the SCEs. Through the analysis on the modeling results for the suggested DC circuit breaker, the advantages of DC circuit breaker using double quench of SCEs were described.

Speaker: Prof. Sung-Hun Lim (Soongsil University)

Thu-Mo-Po4.12 - Power Applications I

Conveners: Kohei Higashikawa (Kyushu University), Erica Salazar (MIT)

866 Thu-Mo-Po4.12-01 [88]: Mobile Superconducting Magnetic Energy Storage for On-site Estimations of the Electric Power System Stability

Photovoltaic power generation and wind power generation are important renewable energy sources in the present power system. However, since these power generations are interconnected to the power system through power converters, the interconnection of large amount of renewable energy sources leads to lower the power system stability due to the lack of the inertial energy of conventional synchronous generators in the power system. The objective of this work is to discuss the feasibility of superconducting magnetic energy storage (SMES) in order to estimate the electric power system stability. SMES has higher response power control capability with a less than second order of the charge/discharge cycle. From this feature, SMES can be expected to identify the eigenvalue which expresses an oscillation mode of the power system. However, since the oscillation mode of the power system varies in real time, the SMES equipment requires the mobility and the weight saving for the on-site identification of the eigenvalue. To overcome this technical challenge, the authors propose the concept of force-balanced coils (FBCs) which are composed of helically coil windings and minimize the required mass of the structure for the SMES coils. In this work, the authors carry out a design study on a MJ class SMES equipment whose components such as SMES coils, refrigerators and power converters are installed in a 40-feet dry container.　For the further weight saving of the SMES equipment, the authors focus on the feasibility of MgB2 wires which have the lowest mass density compared with the other types of conventional superconductors. The authors investigate the engineering feasibility of the mobile SMES equipment for the on-site estimations of the electric power system stability.
Acknowledgement
The authors would like to thank RASMES: Research Association of Superconducting Magnetic Energy Storage in Japan for their valuable discussions and their collaborative works.

Speaker: Dr Shinichi Nomura (Meiji University)

Posters_MT26-Thu-Mo-Po4_12-01_[88]_Nomura.pdf

867 Thu-Mo-Po4.12-02 [89]: Multi-objective filter designing for HTS SMES considering the voltage distribution characteristic

In SMES system, the power conditioning system (PCS) interfaces the superconducting magnet and the AC system. At present, PCS generally adopts PWM converter based on the high-frequency switching devices. The converter outputs PWM pulses voltage with steep rising and falling edges. It is transmitted to the superconducting magnet via the cable, which leads to a spike overvoltage at the superconducting magnet terminals. The high frequency component of the PWM pulse voltage causes a severe uneven distribution within the magnet windings. And it can also accelerate the insulation of the magnet. An effective way to solve this spike overvoltage is to add a filter placing between PCS and superconducting magnets.
This paper firstly gives the frequency domain solving method of HTS SMES transient model. And then a frequency spectrum of the system is determined in frequency domain. According to the obtained spectrum, resonant frequencies can be found out which would provide useful information on the subsequent filter designing between PCS and superconducting magnets. However, the addition of the filter also brings the disadvantage of affecting the response speed and even control instructions of the PCS. Thus, it is need to suppress the overvoltage and ensure the response speed of PCS at the same time. Multi-objective optimized algorithm is adopted in the filter design and its parameter selection with the aim to find a balance point, which would suppress the spike overvoltage and keep the system normal operating at the same time.

Speaker: Mr Meng Liao

868 Thu-Mo-Po4.12-03 [90]: Development of a 1-T Class Force-Balanced Helical Coils Using REBCO Tapes

Applying high-temperature superconducting (HTS) tapes to superconducting magnetic energy storage (SMES) is expected to improve small sized high magnetic field coils. In developing high field coils using HTS tapes, however, large electromagnetic forces caused by a large current and high field can degrade the critical current of HTS in the winding. To decrease the electromagnetic forces, the authors proposed the force-balanced coils (FBC) concept as a feasible option for SMES. The authors design and develop a 1-T class model helical coils (HTS-FBC) based on the FBC concept using REBCO tapes. Although the FBC can minimize the mechanical stresses induced by the electromagnetic forces, the FBC may cause the decrease in the critical current due to three-dimensional complex shapes of the helical windings. In other words, since the tensile strain, the bending strain and the torsional strain simultaneously apply to the REBCO tapes, the critical current of the HTS-FBC decrease. The objective of this work is to clarify the critical current property of REBCO tapes depending on the applying complex mechanical strain due to the winding process, the winding configuration and the electromagnetic forces through the development of the HTS-FBC. In this work, the authors are carrying out to develop the HTS-FBC which has 0.3-meter diameter using REBCO tapes. The winding of the HTS-FBC will be carrying out by using a prototype helical winding machine whose motion is optimized to prevent from decreasing in the critical current during winding process. The authors are planning to carry out the excitation test of the HTS-FBC with liquid nitrogen cooling and liquid helium. This work discusses the allowable mechanical strain which prevent degradation in the critical current of the HTS-FBC thorough the helical coil development process and the excitation test with liquid nitrogen cooling and liquid helium cooling.
Acknowledgements: This work was supported by the Grants-In-Aid for Scientific Research (B), number 16H04321.

Speaker: Mr Hiroharu Kamada (Meiji University)

Thu-Mo-Po4_12-03[90]_Kamada.pdf

869 Thu-Mo-Po4.12-04 [91]: The model and characteristics of SMES coil (1MJ) constructed of corc cable

SMES coil constructed of YBCO coated conductor has been researched these years for its advantage of stored energy without loss under operated temperature. However, the flexible corc cable which can wind with small radius and can work under high magnetic field may be a promising option for smes coil for higher stored energy and higher current. Therefore, it is necessary to consider the smes coil wounded by corc cable.
We proposed a smes coil design (1MJ) constructed by corc cable which has a better performance than smes coil using Roeble cable and YBCO coated conductor.
This paper presented a smes coil model wounded by corc cable with 1MJ stored energy and 10 KA working current in COMSOL, and the maximum energy density and critical current are studied and summarized in this paper.

Speaker: Zhidun Zeng

870 Thu-Mo-Po4.12-05 [92]: Magneto-Archimedes levitation properties for metals by ferromagnetic material arrangement in magnetic fields

We have studied magnetic levitation properties for valuable metals by magneto-Archimedes effect under a high magnetic field gradient. In order to enhance the magnetic force factor BdB/dz in vertical direction, a ferromagnetic cylinder and an array of cylinders were set into the room temperature bore of a 10 T superconducting magnet. We optimized the shape and the arrangement of the ferromagnetic cylinders to increase the magnetic force. The maximum BdB/dz achieved the high value of over -1600 T2/m which was about 4 times larger than that without ferromagnetic materials. The magnetic levitation properties for several kinds of precious metals such as silver, gold and platinum in manganese chloride aqueous solution as a paramagnetic medium were studied. Each precious metal levitated at different height in relatively low magnetic fields. The ferromagnetic cylinder array made the metal grains levitate uniformly in a horizontal direction. This result proposes a new magnetic separator for valuable resource recovery in relatively low magnetic fields utilizing magneto-Archimedes levitation.

Speaker: Mr Daiki Yamamoto

International Conference on Magnet Technology 2019.pdf

871 Thu-Mo-Po4.12-06 [93]: Design and Fabrication of the Permanent Magnet Diverter for Deflecting Electrons on Wide-field X-ray Telescope

The Einstein Probe Satellite is a mission of the Chinese Academy of Sciences to explore all-sky transient X-ray sources and constantly various X-ray sources, which is planned for launch around end of 2022[1]. It will carry a Wide-field X-ray Telescope (WXT) with a large instantaneous FoV and a Follow-up X-ray Telescope (FXT) with a large effective area and a narrow field-of-view. It is dedicated to time-domain astronomy to monitor the sky in the soft X-ray band (0.5–4 keV). For the WXT, it is a key issue to remove the effect of electrons with the energy below 1 Mev out of the beam.
A Permanent Magnet Diverter (PMD) was designed and fabricated to accommodate the WXT and separate the background electrons from the x-ray detecting system by re-directing the electrons. In order to minimize the magnetic flux leakage and the magnetic moment, a design of toroidal magnetic field was considered through arranging the neodymium iron boron permanent magnet blocks appropriately, which could also help reduce the length of electrons deflecting paths when passing the magnetic field. The total weight was also taken into considerations to optimize the structure of PMD. The eigenfrequency, magnetic field shift, deformations and stresses due to the steady accelerations, vibration, shock and temperature change were analyzed, and the motion of electrons in the PMD was tracked and compared for different energies to help improve the structure of PMD. The design, fabrication, and test of the PMD will be presented detailed in the paper.

Speaker: Dr Lei Wang (Institute of Electrical Engineering, Chinese Academy of Sciences)

872 Thu-Mo-Po4.12-07 [94]: Research Magnets with High-Field Uniformity

Magnets with good field uniformity in a good-field region (GFR) of a certain volume are of interest for various research and calibration applications. Due to their simplicity and relatively low cost, Helmholtz coils have been the preferred magnet system for such projects. With air cooling, the magnetic flux density possible with Helmholtz coils is limited to typically 1 mT or below, and field uniformity in the GFR is about one percent. A novel design based on patented double-helix (DH) or Constant-Cosine-Theta (CCT) winding configurations offer better field uniformity in the GFR (order of 1x10-4) and enable much higher levels of flux density due to a much higher transfer function. The novel systems can reach flux density levels of 10 mT with air cooling based on a cooling design in which all parts of the conductor are in direct contact with the airflow. The systems can be built with one, two or all three magnetic axes. The coil configurations and complete designs of such systems with superior performance than Helmholtz coils are presented.

Speaker: Dr Rainer Meinke (AML Superconductivity and Magnetics)

873 Thu-Mo-Po4.12-09 [95]: Development and challenges of a commercial megawatt high temperature superconducting DC induction heater

The high temperature superconductor (HTS) direct current (DC) induction heater shows great advantages on high efficiency and heating quality in comparison to traditional AC induction heater. A commercial megawatt (MW) HTS DC induction heater using REBa2Cu3O7-δ (REBCO) conductors has been developed by Shanghai Jiao Tong University and JIANGXI Lianchuang Opto-eletronic Science and Technology Company Ltd., China. The heater is to preheat aluminum billets with a diameter of 446 mm and a length 800–1500 mm. The HTS magnet are wound by 18 km REBCO tapes from Shanghai Superconductor Technology Company. The HTS coils are coupled with an iron core to generate 0.5 T DC magnetic field at air gaps where aluminium billets are rotated by motors.
The development of this commercial 1-MW HTS DC induction heater has suffered three main technical challenges, which will also occurs widely on the other commercial HTS DC induction heaters. First, the inductance of the HTS magnet with iron is about 100 H, which is challenging for the quench protection of HTS coils. We have tried to apply the no-insulation coil technique to enhance the thermal stability, however, this leads to another problem of ramping delay. Based on optimization analysis, comprehensive multiple measures are developed to ensure the thermal safety this HTS magnet. The second technical challenge is how to drive the billet economically. A peak electromagnetic torque is generated during the start-up of the aluminium billets, which is more than 3 time of the operating torque. The third technical challenge is how to achieve the control of temperature gradient along the axial direction. An adjustable temperature gradient (up to 100 °C) along axial direction is achieved by adjusting the axial field distribution, which is a novel and unique feature of this heater design. The technical experiences of this project are valuable and useful for the commercial HTS DC induction heater and other industrial HTS applications.

Speakers: Ping Yang (Shanghai Maritime University), Yawei Wang (University of Bath)

874 Thu-Mo-Po4.12-10 [96]: Presentation withdrawn

Thu-Mo-Po4.13 - Levitation and Magnetic Bearings III

Conveners: Nikolay Bykovskiy (CERN), Toru Ogitsu (KEK)

875 Thu-Mo-Po4.13-01 [97]: Numerical study on dynamic characteristic of HTS Maglev system based on H-formulation with motional electromotive force

Wenjiao Yang, and Guangtong Ma*
With the merits of passive stability, energy-saved and environment-friendly, high-temperature superconductor (HTS) magnetic levitation (Maglev) is regarded as a promising candidate for the future high speed transit. Limited by the experimental conditions, numerical methods are generally employed in most of the current research on dynamic charactristics of high speed HTS Maglev. However, the governing equation of H-formulation is always employed with the fact that motional electromotive force will make a grateful difference on HTS electromagnetic property during high speed operation ignored. Thus the ultimate goal of this paper is to build a numerical model to advance the understanding of the dynamic charactristics of HTS Maglev system for the potencial high-speed Maglev vehicle applications, such as that of over 1000 km/h, with velocity-related motional electromotive force taken into consideration.
The derivation of H-formulation including motional electromotive force is finished and numerically implemented in finite element method software COMSOL in this paper. In addition, in order to reveal the influence of motional electromotive force on performance of HTS Maglev system at high speed, the dynamic responses of HTS Maglev system under identical external excitations are calculted by models with and without motional electromotive force. The impacts of it on current distribution, magnetic field distribution, temperature distribution, vibrational displacement and electromagneticn forces are deeply explored based on the calculted results. The results from two methods underlines the necessity of the consideration on displacement current in high speed range and will play a positive role to suggest the viable measures for improving the stability of the HTS Maglev system.

Key words: HTS magnetic levitation; H-formulation; motional electromotive force; dynamic response

Speaker: Dr Wenjiao Yang (Southwest Jiaotong University)

poster_YANG_20190918.pdf

poster_YANG_20190918.pptx

876 Thu-Mo-Po4.13-02 [98]: Design optimization of a real-scale REBCO magnet with stepped cross-section shape and its application to EDS train

Abstract: Superconducting magnet is capable of generating immensely strong magnetic field due to its large carrying-current capacity and low power loss, making it a promising candidate for transportation systems and power systems, such as EDS train, NMR/MRI and SMES. It is well known that the higher magnetic field can bring above systems better properties. However, the increase in local magnetic flux density or temperature will result in a decline of the critical current or carrying-current capacity of superconducting magnet, which could restrict the application of superconducting magnet. For the purpose of improving the application of superconducting magnet to EDS train, this paper is to design and optimize a REBCO magnet with stepped cross-section shape (MSCSS), which can make the distribution of the magnetic flux density inside the magnet more uniform and therefore increase the critical current of REBCO magnet. In addition, the MSCSS in EDS train is expected to make the wave form of the electromagnetic forces less harmonic because of the stepped cross-section of magnet. In order to estimate the critical current of the MSCSS, both the so-called T-A model and P-model for MSCSS are established, and the developed P-model can be validated by comparing the calculated results of T-A model. Based on the effective P-model, the geometry parameters of MSCSS are optimized to maximize the critical current of MSCSS, and then these optimal values are used to calculate the suspension force and propulsion force of EDS train. The initially obtained results show that the critical current of MSCSS increases remarkably and thereby the electromagnetic forces can get a proportional increase. Meanwhile, the harmonic component of the electromagnetic forces presents a significant decrease, which will contribute to the stability and comfort of EDS train.
Key words: REBCO magnet, EDS train, optimization, critical current, suspension force

Speaker: Dr Tianyong Gong (Southwest Jiaotong University)

Thu-Mo-Po4.13-02 [98].pdf

Thu-Mo-Po4.13-02 [98].pptx

877 Thu-Mo-Po4.13-03 [99]: Semi-Analytical Calculation of Levitation and Guidance Forces in a Superconducting EDS Train

Electrodynamic suspension (EDS) train is one of the most important ways to develop high-speed or ultra-high-speed rail transit. In order to explore the dynamic characteristics of EDS system with figure-eight-shaped coil, this paper transforms the complex electromagnetic field coupling relationship between vehicle coils and ground coils into a simplified circuit relationship, and introduces the motion characteristics to establish the field-circuit-motion coupled model based on the dynamic circuit theory. Firstly, the dynamic circuit model of the single-sided EDS system is established. The magnetic coupling calculation is carried out between vehicle coils and ground coils. The time-step iteration method is used to solve the induced current control equation of the figure-eight-shaped coil, and the induced current distribution curves under different operating conditions are obtained at the same time. Energy method is employed in transient solution of levitation force, guidance force and drag force. The field-circuit-motion coupled model is verified by three-dimensional finite element model and the experimental data in Japanese Yamanashi test line. After that, a cross-connected EDS train dynamic circuit model is built, as compared with the single sided model, the difference of system performance in suspension and guidance can be investigated. Finally, based on the cross-connected structure, the essential parameters affecting the stability of the system are explored, and the characteristics of vertical, lateral displacement and angular offset of the system are calculated and analyzed. The results of above research can provide a reference for the designing and experimental testing of the EDS train.
Key words: Superconducting electrodynamic suspension (EDS); Dynamic circuit theory; Mutual inductance calculation; Electromagnetic force

Speaker: Mr Yao Cai (Southwest Jiaotong University)

878 Thu-Mo-Po4.13-04 [100]: Dynamic Response Analysis of Superconducting EDS Train Based on Vehicle/Guideway Coupling Dynamics

As a promising candidate for future high-speed transportation, the electrodynamic suspension (EDS) train has drawn considerable attention. The dynamic response of EDS train to eternal excitations could make a great difference on its operating performance, especially in high speed range. Thus this paper focuses on the vehicle dynamics of EDS train, which is separated into two subsystems i.e., train subsystem including superconducting magnets and guideway subsystem including modular function units of the guideway. The emphasis of this paper is therefore to build a dynamic model that can accurately simulate above two subsystems and the interaction between them. The EDS train was modeled as a multibody system with 99 degrees of freedom in which three vehicles are connected by two articulated bogies. The force–gap model with a proportional-derivative controller was adopted to simulate the interaction between superconducting magnets and modular function units. It is confirmed that the proposed model could duly reproduce the dynamic interaction between the train subsystem and guideway subsystem. In addition, the application of proposed model to investigate the effect of track irregularity on EDS system is also reported. The results of this paper could be used for the evaluation and optimization of the dynamic performances of a high-speed superconducting EDS system.

Keywords: EDS train; dynamic response; coupling dynamics

• List item

Speaker: Dr Zhaoying Yan (Southwest Jiaotong University)

Poster for MT_Z.Y.Yan.pdf

Poster for MT_Z.Y.Yan.pptx

879 Thu-Mo-Po4.13-06 [101]: 3-D Analysis of High-Tc Superconductor for Magnetic levitation under High-Speed Movement

The superconducting magnetic levitation(Maglev), realized by high-Tc superconductor subject to high magnetic field generated by permanent magnet of NdFeB, has attracted special interests for applications such as transit and superconducting magnetic bearing(SMB). In the last two decades, several prototypes of HTS Maglev or SMB have been proposed and developed by different groups. Furthermore, the evacuated-tube-transport(ETT) applied HTS Maglev was developed in Southwest Jiaotong University, China, 2014. However, the ETT Maglev maximal speed is 50 km/h, which is much lower than the high-speed of commercial application, because of the finite length of track and budget. To demonstrate the feasibility of ETT HTS Maglev, numerical analysis on the dynamic and thermal stabilities of levitated superconductor subject to high magnetic field, under high-speed operation over 1000 km/s, are indispensable, as the relevant experiments are expensive and hard to perform. In the present work, we will develop a full 3-D finite-element model based on the T-formulation and nonlinear E-J constitutive relationship. The constitutive law considers the influence of magnetic and thermal fields on the critical current density of superconductor. Especially, being different from the existing related models, the effect of thermal is taken into account by the strong coupling multiphysics of electromagnetic and thermal in temporal and spatial domains. Furthermore, the induced electric field induced by the high-speed movement of superconductor is also introduced in our model. We discussed the dynamics and thermal stabilities of HTS Maglev operated under the high-speed from 600 to 1200 km/h. The results attained by this numerical prognostic work, mostly being inaccessible from the present experimental apparatus, are aimed to promote the HTS Maglev in transit and analogous applications.

Acknowledgement
This work was supported in part by the National Natural Science Foundation of China under Grants 51475389, 51722706 and 51707164, in part by China Postdoctoral Science Foundation under Grant 2017M623055, and in part by the Sichuan Youth Science & Technology Foundation under Grant 2016JQ0003.

Speakers: Dr Changqing Ye (Hohai University), Guangtong Ma (Southwest Jiaotong University)

880 Thu-Mo-Po4.13-07 [102]: Numerical study and optimization for a prototype EDS maglev system

In this work, the two major electrodynamic suspension (EDS) methods for transportation, namely the permanent magnet - metal plate method and the superconducting magnet - null flux ground coil (figure 8 coil) method, are studied analytically and numerically. Numerical models in different scales were built and the performances of levitation force, resistive force, characteristic speed, et al. are compared.
This study aims for a design of an EDS prototype system including a train weighing 1.2 t, which levitates at 15 m/s. It is shown that at smaller scale, the permanent magnet based EDS system is preferable due to 1). Without cryogenic requirements, the system is less complicated and the design is more flexible; 2). The effective air gap is smaller since no cryostat presents. However, with increasing scale, the superconducting EDS system becomes more attractive due to the larger magnetic moment of superconducting coils. The advantages include: 1). Lower operating energy dissipation; 2). Larger possible levitation distance; 3). Smaller weight and size of the magnet itself for even larger scale applications. The superconducting EDS route was picked for this project, which is proposed to be built in one year. Based on the numerical studies, the superconducting magnet and the corresponding null flux coils are specifically optimized for the size and speed of the project. The effects of the geometry parameters of the superconducting coil and the null-flux coils, especially the cross-section and the pitch of the null-flux coil will be presented.

Speaker: Xiao-Fen Li (Shanghai Jiao Tong University)

881 Thu-Mo-Po4.13-08 [103]: Study on the EDS-Maglev System Based on Dynamic Circuit Theory

An EDS-Maglev system mainly consists two parts: ground null-flux coils and superconducting magnet on a vehicle or sled. This paper forces on the study of the characteristics of the EDS-Maglev system using dynamic circuit theory. A numerical method including 4-order Runge-Kutta method and inductance space criterion was proposed to improve the calculation accuracy. The calculated results were verified by both the reported data and the simulated results using finite software. Based on the dynamic method, we analyzed the influence of different parameters, such as the distance between adjacent null-flux loops, suspension height, speed and so on, on the EDS-Maglev characteristics, especially in high-speed range. The results of this paper could provide useful information for designing the suspension guidance system of a high-speed transport system and space electromagnetic boost launch.

Speaker: Dr Daoyu Hu (nstitute of Magnetic Levitation and Electromagnetic Propulsion, CASIC)

882 Thu-Mo-Po4.13-09 [104]: Levitation and guidance force for the system of coated conductor stacks and permanent magnets in a wide temperature range.

In order to develop levitated transportation systems based on coated conductors tapes, it is important to know not only the information on the levitation force at vertical displacement, but also the data on the stability of the system at lateral displacements of the superconductor with respect to permanent magnets. Data on the lateral stability of stacks of CC-tapes above the magnetic rail can also provide important information on the axial stability of magnetic bearings based on superconducting tapes.
In this paper, we present new experimental results on the investigation of levitation force and the lateral restoring force of CC-tape stacks, which are subject to cyclic lateral displacements relative to the initial position above permanent magnet assemblies in a wide temperature range from 30 K to 80K. For the measurements, we used a commercially available 12 mm wide CC-tape, produced by SuperOx. The long tape was cut into 12 x 12 mm pieces, which were then stacked. The total number of tape pieces in the stack N ranged from 5 to 100. We measured the dependence of the levitation forces and the restoring force on the displacement for various numbers N at different temperatures. The effect of temperature on the change in levitation force and the restoring force after cyclic lateral displacements was also studied. We have found that the forces tend to decrease as the number of periodic cycles of displacement increases. It was observed that the rate of reduction of forces depends on temperature. In addition, we made a comparison with the data of experimental measurements of the axial force of a superconducting bearing based on СС-tapes.
The data obtained may be useful in the development of bearings and transport systems based on magnetic levitation. The experimental results are in good agreement with theoretical calculations of the lateral force.

Speaker: Maxim Osipov (National Research Nuclear University MEPhI (Moscow Engineering Physics Institute))

883 Thu-Mo-Po4.13-10 [105]: Vertical Dynamic Responses of the HTS Maglev System Under Track Random Irregularity

High-temperature superconducting (HTS) maglev train, with the advantages of low-energy consumption, simple mechanical structure and environment-friendly, is an ideal high-speed transportation in the future. HTS maglev dynamical characteristics considering track random irregularity is important, because the track random irregularity is ineluctable due to the defects produced in installing permanent magnet guideway. In this paper, normal HTS maglev model and vehicle-bridge coupled model are built based on UM software. In order to study the vertical dynamical response of the system, different track random irregularities and other conditions were adopted in the two models. The Sperling index is used to evaluate the system smooth performance under different working conditions. Besides, this paper compared the HTS maglev dynamical response with other maglev trains. The result shows that HTS maglev can run on lower precision guideway and more flexible bridges. And this study suggests the limit of the speed and the designs of bridges in HTS maglev under track random irregularity, as well as providing references for the engineering.
Key words: High-temperature superconductor, levitation, dynamics, vehicle-bridge coupled system, track random irregularities

Speaker: Mr Li Wang ( School of Mechanics and Engineering, Southwest JiaotongUniversity)

Thu-Mo-Po4.13-10 [105].pdf

884 Thu-Mo-Po4.13-11 [106]: A new design and exciting for HTS superconducting magnet of Maglev

Superconducting Maglev is one of the hottest research directions for superconducting applications. The speed of superconducting Maglev on rail is much faster than conventional rail. And hence the superconducting Maglev is considered as a ultimate substitute for rail traffic. The superconducting magnet made by HTS coils is the core component for superconducting Maglev. This paper illustrates a new design for HTS superconducting magnet which has low attenuation rate (which is less than 5%/day), light weight and high-speed excitation. In addition to using persistent current switch controlled by heat to excite the magnet, a flux pump module is also set in the superconducting magnet.

Speaker: Yunhao Pan (Shanghai Jiao Tong University)

885 Thu-Mo-Po4.13-12 [107]: Investigation of the Levitation Force of High Temperature Superconducting Coils using Wind-and-Flip Method

High Temperature Superconducting(HTS) magnet has been proved to be a potential candidate for the maglev system because of its stable self-suspension, low energy consumption and adjustable suspension distance. Nowadays studies on levitation force of HTS magnet are mainly carried out in electromagnetic levitation system, which is between YBCO bulks and permanent magnet guideway. In this paper, a special winding technique called “wind-and-flip” was used to fabricate a jointless HTS magnet for a perfect non-resistive closed loop. We investigated the levitation force between wind-and-flip magnet and the cylindrical permanent magnet under zero-field-cooling condition. The relaxation of levitation force at a certain suspension distance was also investigated. Experimental results showed that the hysteresis effect and the relaxation of the levitation force were both related to the vertical suspension distance between the tested magnet and the permanent magnet. Finally, we proposed a theoretical model based on R-L circuit and E-J power law to represent the change process of levitation force. The simulation results obtained by this model are consistent with the experimental data, and on basis of the model, mechanism of the experimental phenomena is also analyzed . Conclusions obtained in this paper has proved that the wind-and-flip magnet is also a possible option for future HTS electrodynamic levitation system.

Speaker: Mr Zihao Wang (Shanghai Jiao Tong University)

Thu-Mo-Po4.14 - Levitation and Magnetic Bearings IV

Conveners: Nikolay Bykovskiy (CERN), Toru Ogitsu (KEK)

886 Thu-Mo-Po4.14-01 [108]: Proposal of Magnetically Levitated Mover Using High Tc SC Coils

.
INTRODUCTION
Recently, magnetic levitation techniques have been developed for various fields such as magnetically levitated vehicles and energy storage flywheels. Thus, there are many reports about levitation techniques using high critical temperature (Tc) superconducting magnetic bearings (SMBs) composed of superconducting (SC) bulk and permanent magnet (PM). However, there are not so many reports about levitation techniques using SC coils and PMs. In this paper, a new magnetically levitated mover (MAGLEM) using SC coils running on PM guideway is discussed.
STRUCTURE OF MAGLEM
Our group has made a MAGLEM composed of an aluminum body with four SC coils. The MAGLEM runs on the guideway composed of PMs. The MAGLEM measures 0.57 kg in weight, 223 mm in length, 168 mm in width and 67 mm in height. The MAGLEM is composed of four SC coils with 25 mm in inner diameter, 49 mm in outer diameter and 20 turns. The guideway is composed of two railways with an arrangement of alternating polarity PMs. In order to get the speed of the MAGLEM, it is forced to push after the SC coils cooled down.
EXPERIMENTS AND DISCUSSIONS
In the experiments, various speeds are performed. This paper discusses the levitation force, the dynamic characteristics during the running, etc. Each speed gradually decreases with increasing time. This is because there are energy losses in the SC coils. It is found that the levitation force is periodical depending on the speed.
SUMMARY
A new MGLEM is proposed. The mover is composed of four SC coils. The guideway is composed of two railways with an arrangement of alternating polarity PMs. Several experiments are performed to verify the levitation principle.

Speaker: Prof. Mochimitsu Komori (Kyushu Institute of Technology)

Poster(Tanabe).pdf

887 Thu-Mo-Po4.14-02 [109]: Research on Electromagnetic Feasibility of Non-contact Eddy Current Brake System for Ultra-high-speed Maglev Trains

Recently, the national interest in transportation logistics is increasing due to the population aging and metropolitanization. And, it is a big issue for ultra-high-speed rail technology to meet a lot of demand in a short period of time. Germany has commercialized a 501 km/h train in Shanghai, China (2004), and the TGV in France is operating at 570 km/h. In addition, Japan is currently operating a high-speed magnetic levitation trains (Tokyo to Osaka) of 500 km/h. Korea, on the other hand, developed the high-speed train HEMU, which runs at 430km/h, and the maglev (magnetic levitation) train at Incheon International Airport is operating at a low speed of 110km/h. Most high-speed trains except for maglev trains have speeds of 200 to 350 km/h.
Therefore, the ultra-high-speed trains need to develop maglev trains rather than ordinary wheel trains. The 'Hyperloop', which is being developed by Elon Musk as a starting point, is aiming at 1,280 km/h, and a 'subsonic capsule train' with a speed of 1,200 km/h is under development in Korea. As interest in ultra-high-speed train increases worldwide, it is focused on speed-up technologies. However, emergency braking is important to prepare for safety problems. Braking technology applied to conventional trains is classified into contact type and non-contact type, and contact types have a great disadvantage that the friction material is worn because it uses friction force. The non-contact type is classified as rail brake and an eddy current brake. This ordinary contactless eddy current brake is advantageous in that it does not generate direct friction on the wheels by applying magnetic flux to the rail. However, since the attraction force between the electromagnet and the rail is very strong, the rail may be twisted due to high heat generation. Therefore, it is necessary to develop technology for braking on ultra-high-speed trains of maglev trains, not wheel trains. In this study, we analyze the feasibility of rail-contactless new eddy current braking system using the electromagnetic software MAXWELL.

Speaker: Dr Su-Jeong Lee (Yeungnam University and Gyeongbuk Technopark)

20190920_MT-26 발표자료_02.pdf

20190920_MT-26 발표자료_02.pptx

888 Thu-Mo-Po4.14-03 [110]: Guidance performance of YBCO bulks below the liquid nitrogen temperature zone

High-temperature superconducting magnetic levitation (HTS Maglev) system has the intrinsic advantage of self-stabilizing suspension without external control, and has great potential to be a new type of rail transit. The HTS bulks are core component of the the HTS Maglev train. Many experiments show that the levitation performance of superconducting bulks have been significantly improved when the temperature below the liquid nitrogen temperature zone, however, there is no research about guidance performance of multiple bulks at temperatures below 77 K. Therefore, it is necessary to investigate the guidance performance of multiple bulks at temperatures below 77 K. A low temperature experimental platform was set up based on SCML-1[1]. By this system, measurements of guidance force versus temperature and guidance force versus field cooling heights (FCHs) and working heights (WHs) can be performed at temperatures from 50 K to 92 K. According to the experimental data, the most suitable FCH and WH at different temperatures and the lowest cost can be found between the consumption of the bulks and the cryogenic system when designing the HTS Maglev cryogenic system. The results are important for the engineering application of the HTS Maglev train.
Keywords: high temperature superconductor, low temperature, guidance force, refrigerator.

Speaker: Mr Li Wang (School of Mechanics and Engineering, Southwest JiaotongUniversity)

Thu-Mo-Po4.14-03 [110].pdf

889 Thu-Mo-Po4.14-04 [111]: Levitation Force Characteristics of High-Temperature Superconducting Bulks in a High Magnetic Field

The levitation force of high temperature superconducting (HTS) bulks can be enhanced by increasing the strength of the external magnetic field. Many researchers have reached this conclusion by doing experiments above a permanent magnet guideway (PMG). However, the experimental results have limitations because the magnetic field above the PMG is relatively low. In order to obtain more comprehensive levitation force characteristics of HTS bulks, it is necessary to carry out more experiments in high magnetic field. In this paper, we studied the effects of magnetization angle and external field gradient on the levitation force of HTS bulks. We set up a levitation force measurement system based on a 5-T Cryogen-Free Magnet. The HTS bulks were cooled by liquid nitrogen in field-cooling (FC) and zero-field-cooling (ZFC) condition, and the external magnetic field was increased from 0 to 5 T. The HTS bulks were rotated 15° each time and finally rotated to 90°. Experiments show that the levitation force decreases from θ=0° to 90°, where θ is the angle between the upper surface of the HTS bulks and horizontal plane. Relationships between external magnetic field gradient and levitation force as well as magnetization angle and levitation force of the HTS bulks were found in high magnetic field.
Keywords: high temperature superconductor bulks, levitation force, high magnetic field, magnetic field gradient, magnetization angle

Speaker: Mr Shuai Zhang (School of Electrical Engineering, Southwest Jiaotong University)

Thu-Mo-Po4.14-04 [111].pdf

890 Thu-Mo-Po4.14-05 [112]: A superconducting magnetic and electrostatic hybrid suspension and feedback system for gravity measurement

A high precision superconducting levitation system for gravity measurement has been developed which used the levitation of a superconducting sphere by the magnetic field of two superconducting coils. In order to obtain high stiffness in a suspension system, an electrostatic suspension system is introduced to the superconducting levitation system. The hybrid levitation system is operated in feedback so that the sphere remains in a stable position. This method greatly improves the suspension stiffness of the existing suspension structure, and its characteristics will be introduced in the paper. It will provide a reference to expand the dynamic range of gravity measurement.

Speaker: Dr Xinning Hu (Institute of Electrical Engineering, Chinese Academy of Sciences)

891 Thu-Mo-Po4.14-06 [113]: Effect of magnetic field attenuation due to superconducting joint resistance during gravity measurement

The superconducting joint resistance in the superconducting magnetic levitation coil leads to the continuous decrease of the closed-loop current, which causes a weakening of the levitation magnetic field in the gravity measuring device. This magnetic field attenuation will cause the falling of the superconducting sphere used to measure gravity, making the measured data larger than the real data.
In this paper, the cold-welding process for superconducting joints used in gravity measuring devices is studied first, and the magnetic field attenuation caused by the joint resistance is also analyzed. Then, a finite element model was established to find the change in the position of the sphere due to the attenuation of the magnetic field. Moreover, the influence of such sphere position changes on gravity measurement is also obtained, and a compensation method for the influence is proposed.

Speaker: Dr Xinning Hu (Institute of Electrical Engineering, Chinese Academy of Sciences)

892 Thu-Mo-Po4.14-07 [114]: Research of Position Detection and Magnetic Feedback on a Superconducting Levitation Sphere for Gravity Measurement

A device for superconducting gravity measurement with high observing precision and stability is developed. In this device the test mass and spring are in the form of a superconducting sphere and superconducting magnet which is operated in the persistent mode. Once the sphere is levitated in the field generated by the superconducting magnet and the gradient adjusted, the sphere will move relative to the coils of the magnet in response to local gravity changes. In this paper a method of differential capacitance is presented to detect the position of the sphere. The levitation system is operated in magnetic feedback through the feedback coil so that the sphere remains in a position that nulls the capacitance bridge. The magnetic feedback is highly linear and automatically nulled when the capacity bridge output is zero. The position detection and feedback system must be stable, sensitive and linear and the capacitance accuracy has reached the level of ΔC/C=10-5.

Speaker: Dr Chunyan Cui (Institute of Electrical Engineering, Chinese Academy of Sciences)

893 Thu-Mo-Po4.14-08 [115]: Analysis and Experimental Test on a Permanent Magnet EDS System Employing an Annular Halbach Structure

With the rapid development of rare earth materials, the permanent magnet electrodynamic suspension (PMEDS) technology has met a new development opportunity. This paper presents a study on a special PMEDS system named as an electrodynamic wheel (EDW). In the PMEDS system, an annular Halbach permanent magnet array is designed and rotated above a flat aluminium sheet. We establish a simplified 2D and 3D finite element model by the ANSYS Maxwell, and the structural parameters of the EDW and the aluminium sheet were optimized. The relationships between the rotational speed, geometry size of the EDW, pole pairs, thickness of the aluminium sheet, and the lift-to-thrust ratio, lift-to-weight ratio were analyzed. Then, the dynamic force characteristics of the PMEDS system under different rotating speeds and levitation gaps were verified through the dynamic running experiments. This work reveals that the PMEDS scheme is feasible based on an annular Halbach structure and can achieve the stable suspension and propulsion forces.
Keywords: Permanent magnet electrodynamic suspension, Annular Halbach array, Electrodynamic wheel, Force characteristic

Speaker: Mr Shuai Zhang (School of Electrical Engineering, Southwest Jiaotong University)

Thu-Mo-Po4.14-08 [115].pdf

Thu-Mo-Or16 - High Field Magnets for LHC Upgrade

Conveners: Renuka Rajput-Ghoshal (Jefferson Lab), Soren Prestemon (LBNL)

894 Thu-Mo-Or16-01 [Invited]: Status and Plans of the MQXFA Low Beta Quadrupoles for HL-LHC

The final development and demonstration of the US made low beta quadrupoles for HL-LHC is in full swing. CERN is planning to start the upgrade of Large Hadron Collider during the Long Shutdown III, which is scheduled to start in 2024. The US is planning to contribute to this upgrade by providing the Q1 and Q3 Inner Triplet elements plus other components. The first iteration of the magnet design was completed by LARP (the US LHC Accelerator Research Program) in collaboration with CERN, which is planning to make the Q2a/b elements. The magnets in Q1/Q3 (MQXFA) and those in Q2a/b (MQXFB) have identical cross-sections and different lengths. During this phase LARP fabricated and assembled two prototypes. Subsequently, in collaboration with CERN, the US HL-LHC Accelerator Upgrade Project (AUP) finalized the design and QC procedures following the Design Criteria set by AUP and CERN. The most significant changes introduced in the final design are larger radii at shell cut-outs, and use of reduced values for heater-to-coil warm high-voltage tests after helium exposure. AUP is planning to fabricate, assemble and test three pre-series magnets with final design in order to demonstrate readiness for production. AUP has also reassembled the first prototype with a new coil and tested it.
Test results and analyses of the first two MQXFA prototypes, of the re-assembled one, and of the first pre-series magnet are compared and discussed in this paper together with the changes introduced in the final design. Plans for MQXFA magnet production are also presented and discussed.

Speaker: Giorgio Ambrosio (Fermilab)

MQXF_Status_Plans_v9.pdf

MQXF_Status_Plans_v9.pptx

895 Thu-Mo-Or16-02: Assembly of MQXFBP1 prototype, the Nb3Sn Q2 quadrupole for HL-LHC

Abstract— The High Luminosity LHC Project target is to reach an integrated luminosity of the LHC of 3000 fb-1, corresponding to a factor 10 increase in collisions with respect to the current accelerator. One major improvement foreseen is the reduction of the beam size at the collision points. This requires the development of 150 mm single aperture quadrupoles for the interaction regions. These quadrupoles are under development in a joint collaboration between CERN and the US-LHC Accelerator Research Program (LARP). The chosen approach for achieving a nominal quadrupole field gradient of 132.6 T/m is based on Nb3Sn technology. In 2019, the first prototype magnet based on 7-m-long coils has been assembled. The necessary tooling has been validated in 2018 during an assembly based on copper and low-grade Nb3Sn conductor coils. This paper will summarize the assembly of the first MQXFB prototype magnet including geometrical and electrical quality control, and reproducibility of the assembly based on magnetic measurements carried out at room temperature. The measurements taken during the final pre-loading, based on the bladder and key technique, is compared to the knowledge gained throughout the MQXFB short model program and the full length test assembly.

Speaker: Friedrich Lackner (CERN)

260919_MT26_F_Lackner_ MQXFB_P1.pdf

260919_MT26_F_Lackner_ MQXFB_P1.pptx

896 Thu-Mo-Or16-03: Test Results of the First Two Full-Length Prototype Quadrupole Magnets for the LHC Hi-Lumi Upgrade

The future high luminosity (Hi-Lumi) upgrade of the Large Hadron Collider (LHC) at CERN will include eight (plus two spares) 8.4 m-long cryostatted cold masses which will be components of the triplets for two LHC insertion regions. Each cold mass will consist of two 4.2 m-long Nb3Sn high gradient quadrupole magnets, designated MQXFA, with aperture 150 mm and operating gradient 132.6 T/m, for a total of twenty magnets. Before assembling and testing the final cold masses at Fermilab, the twenty component quadrupoles will be tested first at the vertical superconducting magnet test facility of the Superconducting Magnet Division (SMD) at Brookhaven National Laboratory (BNL), in superfluid He at 1.9 K and to 18.0 kA, in accordance with operational requirements of the LHC. Following a test of the first long single coil (in a mirror configuration) of the MQXFA design, the first two full-length prototype quadrupole magnets, MQXFAP1 and MQXFAP2, have been tested at BNL. This paper reports on the quench test and training results of these two magnets, and also the retest of the first prototype, rebuilt and designated as MQXFAP1b. The test results of these magnets will be important for validating the MQXFA design.

Speaker: Joseph F Muratore (Brookhaven National Laboratory)

Thu-Mo-Or16-03 Test Results of First Full-Length Prototypes for LHC HiLumi Upgrade.docx

Thu-Mo-Or16-03 Test Results of First Full-Length Prototypes for LHC HiLumi Upgrade.pdf

897 Thu-Mo-Or16-04: Mechanical performance of the first two prototype 4.5 m long Nb3Sn low-β quadrupole magnets for the Hi-Lumi LHC Upgrade

The U.S. High-Luminosity LHC Accelerator Upgrade Project (HL-LHC AUP) team is collaborating with CERN in the design and fabrication of the first 4.5 m long MQXFA magnets, a 150 mm aperture high-field Nb3Sn quadrupole magnet that uses the aluminum shell-based bladder-and-key technology. The first two prototype magnets, MQXFAP1 and MQXFAP2, were assembled and tested while the first pre-series structure (MQXFA03) was in fabrication. This paper summarizes the mechanical performance of these prototype structures based on the comparison of measured strain gauge data with finite element model analyses from all load steps to powering. The MQXFAP1a magnet almost reached ultimate current before a short to ground was detected and the test was stopped. The MQXFAP2 magnet experienced a low training performance due to a fractured aluminum shell. The mitigations and analyses for the pre-series magnets are discussed in the context of the transition to pre-series production. Lastly, we also report on the first magnetic and fiducialization measurements.

Speaker: Daniel Cheng

Thu-Mo-Or16-04 MQXFA Mechanical Performance_v4.pdf

898 Thu-Mo-Or16-05: A Database-Tool for Storage and Analysis of Magnet Parameters and Test Results

In recent years, several Nb3Sn high field magnet prototypes have been designed and tested in preparation for the LHC Luminosity upgrade and also for the potential Future Circular Collider (FCC). We present a Microsoft Excel -based database tool for storing magnet design parameters and the results of the magnet tests. The hierarchical, yet flexible, structure of the relational database allows for systematic and coherent analysis of the test data from different magnet assemblies, and works as a practical reference for different magnet designs. The database is accessed via an intuitive user-interface, which features several useful functions for data input, analysis, and visualization. We demonstrate the tool usefulness in analysis of results from quench protection heater delay measurements in several high-field Nb3Sn magnet prototypes. We use the data also to validate the simulation assumptions used in the design of the EuroCirCol FCC 16 T dipole magnets.

Speaker: Dr Tiina Salmi (Tampere University, Finland)

MT26_QPDB_TS260919.pdf

899 Thu-Mo-Or16-06: Prediction of the Reversible Critical Current Degradation in Nb3Sn Superconducting Accelerator Magnets

The design of Nb₃Sn superconducting magnets for particle accelerators requires the evaluation of the loads applied to the conductor. It was in fact clearly shown by numerous experiments that the loads applied to Nb₃Sn conducting elements can reduce their critical current, potentially compromising the magnet performances. This reduction can be reversible or not. Experiments, performed on uniaxially loaded strands, allowed to define clear laws to describe the evolution of the critical surface as a function of the applied current, field, temperature and strain. Among these laws, it was shown that the exponential scaling laws can be used to match the available data in the reversible region on both strands and Rutherford cables subject to transverse pressure. In this paper we explore the potential application of this law to superconducting magnets. The methodology was verified against the available test data on cables and strands. Furthermore, it was applied on the MQXF magnet, a quadrupole developed for the High Luminosity LHC project. The maximum critical current reachable as a function of the applied prestress was studied and compared with the results available from tested magnets.

Speaker: Giorgio Vallone (Lawrence Berkeley National Laboratory)

Thu-Mo-Or16-06-Vallone.pdf

Thu-Mo-Or17 - Very High Field Magnets

Conveners: Gen Nishijima (National Institute for Materials Science), Xavier Chaud (LNCMI-EMFL-CNRS, Univ. Grenoble Alpes, INSA, UPS)

900 Thu-Mo-Or17-01 [Invited]: High field cryogen-free superconducting magnet development beyond 30 T with advanced REBCO and high strength Nb3Sn conductors

After we have developed the 25 T cryogen-free superconducting magnet (25 T-CSM) with a Bi2223 insert, Nb3Sn and NbTi Rutherford outsert coils [1], we are planning two projects on high field cryogen-free superconducting magnets. One is an upgrade of the 25T-CSM to 30 T with replacing the present Bi2223 insert to an REBCO one [2]. The other plan is to build a new high field CSM beyond 30 T. For these two projects, two REBCO tapes co-wound pancake coils with an additional Hastelloy tape for reinforcement are considered as the insert coil. The primitive design of a 33 T cryogen-free superconducting magnet with a 32 mm room temperature bore was done as well as the REBCO insert for the upgrading, on the basis of the 25 T-CSM. For the REBCO insert, a EuBCO with BHO tape, which is developed by Fujikura, is a candidate [3]. In case of the LTS outsert, the NbTi and the high strength Nb3Sn Rutherford cables are used similarly to the 25T-CSM. To increase the efficiency of the LTS coil, the improvement of mechanical strength of CuNb reinforced Nb3Sn strands are carried out with Furukawa. In addition, the two REBCO tape co-wound pancake R&D coils with and without additional Hastelloy reinforcement were tested. The effects of coupling of two tapes and of large electromechanical stress on the R&D coils will be discussed in the presentation as well the overview of the projects.

[1] S. Awaji et al., SuST, 30 (2017) 065001.
[2] S. Awaji et al., IEEE TAS (2019) in press.
[3] S. Fujita et al., IEEE TAS (2019) in press.

Speaker: Satoshi Awaji (Tohoku University)

901 Thu-Mo-Or17-02: The 40 T Superconducting Magnet Project at the National High Magnetic Field Laboratory

The National High Magnetic Field Laboratory (NHMFL) has launched an innovative project to develop a 40 T all-superconducting user magnet. The first year of funding was awarded by the National Science Foundation and the project started in September 2018. Consideration of a 40 T superconducting user magnet set target specifications of a cold bore of 34 mm with a homogeneity of 500 ppm over a 1 cm diameter of spherical volume, a better than 0.01 T set-ability and stability, and with an ability to ramp up to full field 50,000 times over its 20 years design lifetime. It will be a fully superconducting magnet operated in a 4.2 K liquid helium bath, can withstand quenches at its full 40T field and provide a very low noise environment for experimentalists. These capabilities will enable the 40T SC magnet to support higher-sensitivity measurements than possible in present-day resistive and hybrid magnets, high-magnetic-field measurements that will be uniquely capable of addressing physics questions from previously inaccessible perspectives on a number of expanding frontiers in condensed matter physics. A 40 T superconducting magnet would enable more users to run long experiments at peak field with much less power consumption compared with resistive and hybrid magnets. Realization of a 40T SC magnet requires magnet technology that is beyond the present state-of-the-art. Initial analysis of different HTS magnet designs, each based upon one of the three presently viable HTS conductors: REBCO (Rare Earth Ba2Cu3Ox), Bi-2212, Bi-2223, has determined that each design faces significant technical challenges. Hence, four HTS magnet technologies consisting Insulated REBCO magnet technology (I-REBCO), No-Insulation REBCO magnet technology (NI-REBCO), Bi-2212 magnet technology, and Bi-2223 magnet technology will be developed in parallel initially. Technology gaps based on risk analysis at each stage will be closed to advance key technology components. The process repeats until the final design has emerged. The objective of the 40 T all superconducting user magnet and the current status of the project will be presented.

Speaker: Hongyu Bai (National High Magnetic Fied Laboratory)

Thu-Mo-Or17-02_Bai 40T SC Magnet at the NHMFL.pdf

902 Thu-Mo-Or17-03: Test and commissioning of the 32 T superconducting magnet

After a successful first test of the 32 T superconducting magnet, it was inspected and prepared for commissioning. Here we report on the initial result of reaching 32 T, meeting the specifications and other pertinent observations from the first test. Following is a brief description of the facilities at its permanent location as a user magnet in the expanded NHMFL MilliKelvin building. The final configuration of the magnet, including instrumentation and protection systems, is described. Progress in characterizing and addressing the non-linearity in the field-current relation is presented. Lessons learned during the commissioning of this unique magnet conclude this work.

This work was performed at the National High Magnetic Field Laboratory, which is supported by National Science Foundation Cooperative Agreement No. DMR-1157490, DMR-1644779 and the State of Florida.

Speaker: Hubertus Weijers (NHMFL/FSU)

Thu-Mo-Or17-03-Weijers.pdf

Thu-Mo-Or17-03-Weijers.pptx

903 Thu-Mo-Or17-04: Development of High Field Superconducting Magnets with Increasing Persistence and EXperimental Access

Following the development of wide bore superconducting magnets using low temperature superconductors (LTS) for integrating ultra-high field high temperature superconductor (HTS) inserts, new applications for this LTS ‘outsert’ technology require higher temporal and mechanical stability. The development of an 18 Tesla, 150mm bore magnet system designed for scanning tunneling microscopy (STM) experiments is one such application. The design and performance of this magnet system is described. A second application for compact, large bore, high field magnets is the study of dark matter. The design of a 12 Tesla, 320mm bore LTS magnet with an adjacent region low in B field is described. This system currently being developed requires a significant extension to existing ‘outsert’ technology utilizing large, reverse wound shield coils above the main solenoids.

In addition, the technical advances required for the development of solenoid 'outsert' magnets are now extending the design envelope for magnets with split access for beamline applications. Such systems are designed to run with sets of coils either side of the beam in symmetric and asymmetric modes. The increasing trend for such systems requiring active shielding to reduce B field external to the cryostat leads to new design challenges. Managing quench events with increased current densities at high magnetic field in all modes of operation is essential. The current state of the art and also the potential for further development of these wide bore superconducting systems is described.

Speaker: Andrew Twin (Oxford Instruments)

904 Thu-Mo-Or17-05: Progress in the construction of the Nijmegen 45T hybrid magnet system

The High Field Magnet Laboratory of Radboud University is constructing a 45 T hybrid magnet system. The 620 mm bore, 12.3 T, 20 kA, Nb3Sn cable-in-conduit superconducting outsert magnet has been developed and fabricated in close cooperation with the National High Magnetic Field Laboratory in Tallahassee FL. A 22 MW/40 kA resistive insert magnet will contribute another 32.7 T to the total field. After completion of the outsert coil in 2017 the cold mass has been installed at HFML. The binary (Cu/BSCCCO) current leads have been thoroughly tested and are ready for integration. The main cryogenic auxiliary systems like the Linde LR140 refrigerator, the valve box for distribution and conditioning of the supercritical helium flow, the Stirling cryo-generator for cooling of all system’s radiation shields and their connecting cryo-lines have been submitted to a partial functional system test. The present development status of the cryostat, the superconducting bus bars, system control, coil protection and the resistive insert is presented in this paper.

Speaker: Mr Andries den Ouden (High Field Magnet Laboratory, Radboud University)

Thu-Mo-Or17-05 den Ouden.pdf

905 Thu-Mo-Or17-06: From Manufacture to Assembly of the 43 T Grenoble Hybrid Magnet

The Grenoble Hybrid magnet is a modular platform applying resistive and superconducting technologies to deliver various continuous high magnetic field and flux configurations. They range from 43 T in 34 mm diameter with 24 MW down to 9 T in 800 mm with the superconducting coil alone. The key design parameters are recalled including the specifically developed conductor, the large bore superconducting outsert coil, the cryostat with the eddy-current shield and the cryogenic infrastructure. The status of the project is given together with the main problems encountered and solved.

The ongoing validation phases of the resistive Bitter and polyhelix inserts performed at up to 24 MW is also presented. Thanks to the ongoing upgrade of the electrical power installation to 36 MW at the LNCMI-Grenoble, it will be possible to increase the total field to up to 45-46 T in the future. The support structure of the superconducting outsert had already been adapted during the design phase and a material development program initiated for the resistive insert.

All major equipment of the hybrid magnet has been built, tested and delivered to LNCMI-Grenoble, where integration and assembly is close to completion. The commissioning of the overall hybrid magnet system will start in 2020 and will be followed eventually by the first run of a new axion dark matter search experiment.

AKNOWLEDGEMENTS: This project is supported by the CNRS, the French Ministry of Higher Education and Research in the framework of the “Investissements pour l’avenir” Equipex LaSUP (Large Superconducting User Platform), the European Funds for Regional Development (FEDER) and the Rhône-Alpes region.

Speaker: Dr Pierre Pugnat (LNCMI-EMFL-CNRS, UGA)

Thu-Mo-Or17-06 Pugnat.pdf

906 Thu-Mo-Or17-07: Winding and 77 K Testing of Non-Insulated Coils for the IBS 25 T, 100 mm bore HTS Solenoid

Brookhaven National Lab (BNL) is in the process of building a 25 Tesla, 100 mm cold bore HTS solenoid for the Institute of Basic Science (IBS) in South Korea for their search for Dark Matter Axions. The magnet consists of 28 coils (in a 14 double-pancake (DP) coils configuration) with an inner diameter of 105 mm and has an outer diameter of 200 mm, wound using Second Generation (2G) High Temperature Superconductor (HTS) tape from SuperPower. Each coil is wound to size using approximately 300 m of conductor with the number of turns ranging between 620 to 630 turns. Most coils have one splice, but a few have three splices. Several voltage-taps are placed in each coil during winding. Two single pancake (SP) coils will be mated through a center interconnect (splice) to make a double pancake coil. Out of the 28 scheduled coils, 16 coils have been wound and tested at 77K in Liquid Nitrogen (LN2). The LN2 test is an important step during magnet construction as it provides a means to validate the quality and integrity of each coil. A significant variation in the critical current has been observed in the coils tested so far. This paper will present the construction and test results for the 16 coils at 77K.

*This work was carried out under a research agreement between Institute of Basic Science, Korea and Brookhaven Science Associates, LLC under contract No. IBS-NF-16-32. This work was also supported by Brookhaven Science Associates, LLC under contract No. DE-SC0012704, with the U.S. Department of Energy.

Speaker: Shresht Joshi (Brookhaven National Laboratory)

MT26_SJoshi_Winding_Thu-Mo-Or17-07.pdf

MT26_SJoshi_Winding_Thu-Mo-Or17-07.pptx

Thu-Mo-Or18 - Rotating Machines II

Conveners: Rainer Meinke (AML Superconductivity and Magnetics), Yunxing Song (GE Global Research)

907 Thu-Mo-Or18-01 [Invited]: Development, test, installation, and commissioning of the 3 MW superconducing EcoSwing wind power generator

In the EU funded EcoSwing project the world’s first large-size superconducting low-cost and lightweight multi megawatt wind turbine generator was designed, built and tested in a real wind turbine.
In order to realize this generator a technology to produce high quality HTS coils for reliable industrial use was developed and successfully qualified. Due to the high magnetic fields generated by the superconducting coils in the rotor a decrease of diameter from 5.4 m to 4.0 m and corresponding weight reduction was achieved.
In 2018 the generator was first tested in a nacelle test rig on ground and then installed on an existing wind turbine with 128 m rotor diameter in a demanding coastal site in western Denmark. There, the previously installed PM direct drive generator was replaced by the much smaller superconducting EcoSwing generator. During commissioning early 2019 already more than 150 h of operation were achieved and power was delivered to the grid. Electromagnetic characteristics were met or even exceeded expectations. Cooling of the rotor was reproducible demonstrating the reliable performance of the cryocoolers.
An overview on the design and test results will be given, and main design features will be explained with a special focus on the superconducting coils and cryocooling.
Acknowledgements:
EcoSwing has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 656024.

Speaker: Markus Bauer (THEVA Dünnschichttechnik GmbH)

2019-09-26 MT26 Ecoswing Bauer.pdf

908 Thu-Mo-Or18-02: Development of non-insulated racetrack coils wound with second generation high temperature superconductor tapes for a stator system for wind generators

With the high current carrying capacity of second generation superconductors the increase of power density of electrical devices is a main research subject in the field of superconductor’s application. Several studies show a potential reduction in volume and weight of electrical rotating machines, while keeping the rated power output. Especially, compact and more lightweight generators in offshore wind turbines would result in a reduction of the levelized cost of energy. Whereas most of the superconducting wind generator designs follow the principle of a synchronous machine with a superconducting rotor, this approach investigates the implementation of the superconducting coils on the non-rotating stator, which enables a simplified cryostat and cooling system design. To avoid the use of cryogenic liquids and reach temperatures below 77 K a conduction cooling method for keeping the coils at their operating temperature is envisaged.
Furthermore, the self-protecting ability of coils without a turn to turn insulation could make the need of a complicated and sensible quench protection system redundant. To expedite the use of such coils in a real power application the design and construction of a 10 kW laboratory generator demonstrator is set as an objective. Therefore, a pancake racetrack coil is designed for the usage in the stator system of such a demonstrator and wound without any insulation between the turns. The performance of this coil, especially under conduction cooled conditions below 77 K, is investigated. The first results in terms of effectiveness of the cooling system, recording the typical parameters of non-insulated coils and investigating the thermal and electrical behavior at dynamic load situations is presented.

Speaker: Mr Fabian Schreiner (Karlsruhe Institute of Technology)

MT26_Fabian_Schreiner_Development of non-insulated racetrack coils wound with 2nd generation HTS tapes for a stator system for wind generators.pdf

909 Thu-Mo-Or18-03: Dual Superconducting Halbach Array Generator for large Direct Drive Wind Turbines

The development of off-shore wind farms will need to rely on large turbines, ideally over 10 MW, to be economically viable. Therefore, there is a need for cost effective and very reliable drive trains for large wind turbines. The first step in increasing reliability is to not use gearboxes and connect the generator directly to the turbine rotor. The very large torque required leads to very large conventional generators (usually permanent magnet generators) and the only viable option is to use high specific torque, low RPM superconducting machines. We propose a direct-drive wind turbine generator based on a non-conventional assembly of small superconducting dipole magnets assembled to focus the excitation field in a copper wound stator. The generator is based on a Dual Superconducting Halbach Array Rotor and resistive stator. The Halbach array configuration allows for the field to be intrinsically contained within the machine without the need for iron laminations thus reducing the mass to a minimum. The rotor is composed of identical individual superconducting dipole magnets based on the Double Helix configuration leading to perfect dipole fields and ideal mechanical stability. The individual, mass produced, dipole magnets are wound with very high performance REBCO tapes with no insulation allowing for stellar stability and low sensitivity to thermal transients. The stator is composed of air- or water-cooled copper conductors supported by high thermal conductivity 3D printed substrates allowing for direct cooling. The proposed generator technology is applicable to both on- and off-shore wind turbines and is scalable beyond 10 MW with excitation magnetic field of 3-5 T. The generator is composed of standardized mass-produced components that can be assembled on site which leads to an overall cost reduction. The paper deals on the first phase of the project and includes the design and optimization of a 10 MW direct drive generator based on a novel and innovative configuration and its impact on the levelized cost of energy.

Speaker: Rainer Meinke (AML Superconductivity and Magnetics)

910 Thu-Mo-Or18-04: Evaluation and Mitigation of AC Losses in a Fully Superconducting Machine for Wind Turbine Applications

Offshore wind turbines are becoming an integral part of the future large-scale renewable generation initiatives. It is envisioned that to upscale offshore wind turbines in the range of 10+ MW power, superconducting (SC) technologies must be explored. Several partial and fully SC machine designs have been proposed and demonstrated for offshore direct-drive wind turbines. It is theoretically shown that the fully SC machines can further improve the efficiency and power density of wind turbines while lowering the levelized cost of energy. However, fully SC machines pose many technical risks, which must be addressed before commercial application. A key challenge of fully SC machines is high ac losses generated in the armature winding. These losses pose a significant barrier to the use of fully SC machines in high-speed applications. But, it is expected that direct-drive wind turbine ac losses can be handled due to their low frequency.
Most of the fully SC machine designs in the literature are primarily focused on EM designs and validating their electrical performance. However, the practical implementation of these machine designs heavily depends on the accuracy of estimated ac losses and associated cryocooler design. Therefore, extensive attention must be paid to validating ac loss evaluation and mitigating these ac losses for a feasible machine design. This paper presents a detailed evaluation of ac losses of a 10-MW fully superconducting machine. An inside-out synchronous machine with MgB2 race rack coils is investigated in this research. A rigorous ac loss calculation utilizing finite-element analysis is performed using different ac loss models available in the literature. Further, these analytical results will be validated against experimental results conducted on individual race rack coils. After the ac loss models are validated, an optimized machine model will be obtained which limits the ac losses to a manageable level.

Speaker: Mr Thanatheepan Balachandran (university of Illinois at Urbana-Champaign)

MT_presentation_16_9_final.pdf

MT_presentation_16_9_final.pptx

911 Thu-Mo-Or18-05: New Type of Linear Switched Reluctance Generator for Wave Energy Applications

One promising source of clean and efficient energy comes from the ocean waves since they transport a considerable amount of energy. In the recent years there have been many highly scientific proposals for harvesting this energy in an efficient manner but in any case one of the key points to guarantee such efficiency is the selection of the PTO (Power Take Off). This conversion process is characterised by a significant fact: To achieve a considerable amount of power and since the moving speeds are low, the involved forces must be very high. On the other hand, the higher the number of conversion stages in the generation process, the lower becomes its efficiency. In this regards the ideal converter would be a very powerful single stage machine (direct drive).
Electrical machines automatically fulfil the condition of a single stage conversion but lack of the capacity for producing the higher forces that can be achieved with hydraulic actuators.
Some years ago some of the authors developed a high force density machine based on the switched reluctance principle, more reliable, robust and especially suitable for long stroke applications. A prototype was built and tested in the lab and then hosted in a so call "point absorber" and launched into the sea for producing energy.
Now the authors have proposed a novel topology of a Switched Reluctance Machine for making more efficient machines increasing its force density in order to harvest more energy from a certain wave. The idea constitutes the basis of a project which was presented to an H2020 RIA (Research & Innovation Action) type call and approved and which is now on-going. The design of a prototype is about to be finished and the construction will start in the next months.
The paper will describe the concept of the machine and its design as well as the foreseen applications in the framework of the project and beyond.

Speaker: Dr Luis Garcia-Tabarés (CIEMAT)

MT26 PRESENTATION THU-MO-OR18-05_FINAL 2 16-9.pdf

MT26 PRESENTATION THU-MO-OR18-05_FINAL 2 16-9.pdf

MT26 PRESENTATION THU-MO-OR18-05_FINAL 2 16-9.pptx

912 Thu-Mo-Or18-06: High temperature superconducting hybrid tape stacks - an enabling technology: challenges for DC and AC applications

Abstract:
Trapped magnetic flux by high temperature superconducting tape stacks manufactured by ASCG at University of Cambridge allowed to reach the current world record of 17.7 T [1]. Despite of this undisputed success there are different challenges for such tape-stacks to operate in field cooled DC conditions [1], pulse conditions [2] as well as AC conditions, where demagnetization of trapped magnetic flux may reduce applicability of the stacks in electrical motors [3,4].
We will discuss solutions to achieve the best performance for applications of such novel high temperature superconducting tape stacks in DC, transient and AC conditions.

Acknowledgement:
This research is financially supported partially by the European Union’s Horizon 2020 research innovation program under grant agreement No. 7231119 (ASuMED “Advanced Superconducting Motor Experimental Demonstrator”) and also by EPSRC grant No. EP/P000738/1 “Development of superconducting composite permanent magnets for synchronous motors: an enabling technology for future electric aircraft”.

References:
[1] Patel A, Baskys A, Mitchell-Williams T, McCaul A, Coniglio W, Hänisch J, Lao M, Glowacki B A, “A trapped field of 17.7 T in a stack of high temperature superconducting tape,” Superconductor Science and Technology, 31, 9 (2018).
[2] Patel A and Glowacki B A, “Enhanced trapped field achieved in a superconducting bulk using high thermal conductivity structures following simulated pulsed field magnetization”, Superconductor Science and Technology, 25, (12) 125015 (2012).
[3] Baskys A, Patel A and Glowacki B A, “Measurements of crossed-field demagnetization rate of trapped field magnets at high frequencies and below 77 K”, Superconductor Science and Technology, 31, 065011 (2018).
[4] Climente-Alarcon V, Smara A, Mineev N, Glowacki B A and Reis T, “Novel Architecture of Trapped-Field Superconducting Rotor for Aircraft Applications", Superconductor Science and Technology, Submitted: SUST-103237.

Speaker: Prof. Bartlomiej Andrzej Glowacki (ASCG Department of Materials Science and Metallurgy, University of Cambridge and Institute of Power Engineering)

BartekGlowacki MT Oral public.pdf

913 Thu-Mo-Or18-07: Design and testing of a gas-helium cooled REBCO magnet prototype for a 10-Mvar HTS synchronous condenser

A 10-Mvar HTS synchronous condenser is under development, including a 36-slot air-core stator, and a 4-pole HTS rotor assembled by 12 REBCO double pancake (DP) coils. In this work, a scaled superconducting magnet prototype consisting of two DP coils was designed and fabricated before full manufacturing, which has an effective length of 300 mm and was wound by 5-mm wide REBCO tapes. To avoid delamination, these ReBCO coils are vacuum impregnated with paraffin instead of epoxy. And to enhance the mechanical strengthen, reinforcement structures and epoxy are applied between the coil surfaces and frameworks. The magnet prototype was conduction cooled by 5 bar, 20 K helium gas transmitted in copper pipes embedded in the magnet base plate. The experimental results show that the magnet can be effectively cooled to 21 K. Moreover, the magnet temperature remained stable for 1 hour during the continuous operation at the rated current of 250 A. The temperature distributions at different operation currents from 200 A to 270 A were also measured and compared to the simulation results considering heat loads from soldering parts and current leads. It was proved that the cryogenic and manufacturing solutions for the magnet prototype meet the requirements of the HTS rotor.

Speaker: Dr Timing Qu (State Key Laboratory of Tribology, Department of Mechanical Engineering, Tsinghua University, Beijing 10084, China.)

Thu-Mo-Or18-07.pdf

12:45 Lunch (on your own)

Thu-Af-Or19 - High Tc Wires and Cables II

Conveners: Francesco Grilli (Karlsruhe Institute of Technology), Dr Kathleen Amm (Brookhaven National Laboratory)

914 Thu-Af-Or19-01: Progress of SuperPower 2G HTS (RE)BCO Conductor Development for Magnet Applications

Developments in 2G HTS conductor performance continue to drive the design and operating limits for a broad range of demanding magnet applications. The design, testing and fabrication technology of 2G HTS (RE)BCO conductors is presented, highlighting the ability of 2G HTS wire to function under a wide range of operating conditions. SuperPower continues to address 2G HTS conductor development and production methods to improve characteristics and performance of the wire and provide technical support in its use. In particular, extensive studies on wire properties have been carried out and processing upgrades implemented to improve both the base performance of the conductor, as well as its functionality by enhancing key characteristics such as piece length, mechanical properties and uniformity of critical current and performance in magnetic fields. Updated measurements on recent production material are presented and plans for future performance targets discussed.

Speaker: Mr Drew Hazelton (SuperPower Inc.)

MT26 Thu-Af-Or19-01.pdf

915 Thu-Af-Or19-02: New product line of SuperOx 2G HTS tapes customized for application in specific ranges of magnetic fields and temperatures

In 2018 SuperOx Japan reached production capacity of 200 km of 4 mm 2G HTS wires per year. The manufacturing of our standard 2G HTS wires was aimed at the needs of light-weight cables and superconducting fault current limiting devices (SFCL), which operate under the conditions of self-field and 70-77K. Although the standard SuperOx wires with Ic>500A for 12 mm width outperformed the needs of such applications, we could identify the growing demand for the wires requiring excellent performance in the moderate and strong magnetic field and in the range of lower temperatures, which could not be always satisfied by the existing 2G HTS wires. At the same time, the upgrade of the PLD equipment allows to double production capacity in 2019, and it created urgent need for development of the new types of HTS wires for the operation in moderate and high magnetic field.
Based on the prospective operating conditions in terms of magnetic filed strength and temperature we outlined four target areas of interest for the development of the new HTS wires: 1) superconducting rotating machines (1-3T and 65-77K); 2) accelerator magnets and coils for levitating devices (3-5T, 30-40K), 3) superconducting magnets for fusion reactors (12-20T, 20K) and 4) high-filed NMR (30T, 4.2K).
The development strategy for new line of SuperOx 2G HTS wires relied on the combination of the following approaches:
- Optimizing the overall superconducting material stoichiometry;
- Variation of chemical composition by substitution into RE-site;
- Introduction of artificial pinning centers in the PLD process;
- Heavy ion irradiation of the HTS wires to create columnar defects;
- Fabrication of multilayered superconductor structures;
SuperOx Japan is ready to supply 2G HTS superconducting wires customized for the applications operating in the various magnetic fields and temperatures.

Speaker: Dr Valery Petrykin (SuperOx-Japan LLC)

Thu-Af-Or19-02_v1.pdf

Thu-Af-Or19-02_v1.pptx

916 Thu-Af-Or19-03: Development of ReBCO coated conductors with improved properties for magnet applications by THEVA

Magnet applications require coated conductors with high in-field performance, well-defined geometry, high mechanical stability, as well as adequate stabilization. At THEVA coated conductors are produced using an all PVD approach. The high performance of the tape is enabled by ISD-MgO buffer layers and several micro meter thick GdBCO HTS layers.
High performance at fields up to 31 T was recently reported with our standard coated conductors. To improve the wire for magnet applications THEVA is now testing the applicability of artificial pinning to our technology. First results already show significant improvements below 30 K and above 5 T. Furthermore, a PVD approach for the Ag and Cu stabilization is now in production which gives a high uniformity due to the inherent features of PVD processes. This will allow a very dense packaging of the wire in magnet coils. Together with the newly developed 50 µm thick substrate wires a very significant improvement in terms of current density can be realized.
We will show a summary of the recently achieved properties and give an outlook on the next development steps on our roadmap.

Speaker: Dr Markus Bauer (THEVA Dünnschichttechnik GmbH)

2019-09-26 MT26 HTS tapes Bauer.pdf

917 Thu-Af-Or19-04: Recent Advances in REBCO Tapes and Round Wires for High Magnetic Field Applications

Through a combination of thick films (4-5 µm) and a high density (8000 – 12000/µm^2) of fine nanocolumnar defects, excellent critical currents have been achieved in REBCO tapes over a wide temperature range of 4.2K – 65K and magnetic fields of 1.5T – 30T. Record-high engineering current density (Je) of 5200A/mm^2 at 4.2K, 15T (corresponding critical current density (Jc) of 10MA/cm^2) which is more than a factor of five better than the Je of the best Nb3Sn wires and 7 times better than the Je of commercial REBCO tapes has been demonstrated. At 65K, 1.5T, critical currents exceeding 1750A/12mm have been achieved, meeting a key milestone of the Next Generation Electric Machines program funded by the DOE-Advanced Manufacturing Office. We have also developed a Symmetric Tape Round (STAR) wire technique to fabricate 1.6 to 1.9mm diameter round REBCO wires with high Je and excellent tolerance to bend strain. STAR REBCO wires can be bent to a radius of just 15mm while sustaining a Je of 600A/mm^2 at 4.2K, 20T which meets key stringent requirements of accelerator magnets. Both high performance REBCO tapes and round wires are being scaled to long lengths to fabricate prototype coils and magnets. Details of the latest advances in REBCO tapes and round wires for high magnetic field applications will be discussed in this presentation.

Speaker: Venkat Selvamanickam (University of Houston)

918 Thu-Af-Or19-05: Controllable Critical Current Degradation of ReBCO CC by Post-Manufacturing Annealing

ReBCO CC (Rare earth barium copper oxide coated conductor) is a viable candidate as a conductor for future high-field magnets due to its mechanical strength, high Tc, and favorable Jc vs. B dependence. In practice, some ReBCO coils, especially solenoids, only utilize a fraction of the full critical current throughout the winding due to the large (5-7) anisotropy of Ic, thereby developing undesired screening currents and detrimental quench behavior. By controllably deoxygenating as-manufactured tapes and creating a more homogenous distribution of effective Ic in the solenoid, a more reliable ReBCO CC magnet can be constructed. The phenomenon of critical current degradation in ReBCO due to variation of oxygen doping with temperatures is well known and has been previously studied, typically with the copper exterior removed. In our study, the effects of annealing as-manufactured ReBCO CC from various manufacturers are being explored by exposing short samples to various heat treatments to determine the Ic degradation dependence on temperature and duration. By subjecting ReBCO short samples to various heat treatments and characterizing the changes in superconducting properties, we wish to derive an empirical relation describing the critical current degradation of ReBCO CC so as to establish a repeatable methodology of degradation. By controllably removing oxygen from the ReBCO by post-manufacturing annealing, both critical current and critical temperature can be tuned for specific sections of a high-field ReBCO CC magnet, thereby reducing stress-inducing screening currents throughout the magnet, and promoting less localized quench behavior.

Speaker: Griffin Bradford (FSU - NHMFL - ASC)

Bradford_Griffin_MT26_Presentation.pptx

919 Thu-Af-Or19-06: Electromechanical Performance of CORC® Cables and Wires under Axial Tension and Transverse Compression

Advanced Conductor Technologies is developing high-temperature superconducting (HTS) Conductor on Round Core (CORC®) cables and wires for high-field accelerator, fusion and scientific magnets. One of the concerns with operating any HTS conductor in magnets that operate at currents exceeding 10,000 A at fields of over 20 T in future accelerator magnets, or 50,000 A at fields over 12 T in fusion magnets, is the effect of mechanical stress and stress cycling on the conductor performance. Detailed mechanical tests of the conductor performance under axial and transverse stress relevant for magnet operation are thus required to develop robust magnet conductors. Here we present test results of critical current (Ic) degradation as a function of applied transverse compressive load on CORC® cables and wires as well as axial tensile stress on CORC® wires at 76 K. The critical load, or stress at which Ic degrades irreversibly by at least 2 – 3 % in practical CORC® conductors is predominantly determined by the properties of the metal former and to a lesser extend by the superconducting tapes. Significant strengthening of the CORC® conductors can thus be achieved by optimization of the former size and yield stress. Fatigue cycling is performed at different stress levels up to 100,000 cycles to investigate Ic retention beyond the design life of modern user magnets and fusion devices. CORC® cables and wires presently exhibit excellent electrical performance in mechanical fatigue at stress levels where Ic degraded by only 3 – 5 %, and even at stress levels at which the initial decrease in Ic was as high as 20 %.

Speaker: Danko van der Laan (Advanced Conductor Technologies)

920 Thu-Af-Or19-07: Low cost transposed cables for coil windings made with Type NX 1G and ReBCO 2G HTS tapes

ABSTRACT BODY:
HTS tapes, because of their widths and large shape aspect ratios, have not been readily manufacturable into Rutherford or Roebel cables, even though these kinds of cables are required for many large coil applications. A type of transposed Roebel cable is under development with 2G tape, but its design flexibility is very limited, and its processing very complex, as well as requiring that much of the expensive 2G tape feedstock be discarded. However, Sumitomo Electric’s highly robust Type NX tape, based on 1G, and strain tolerant 2G ReBCO tapes, combined with our recent groundbreaking advances in cabling provide an opportunity to develop and produce long lengths of low-cost HTS transposed tape cables for fabricating large coils by the simpler react-and-wind approach. Using our cable design model, combined with the properties of NX and 2G, we have identified architectures for producing prototype transposed HTS tape cables by this new cabling approach. Test runs with a 6-strand cabling machine were completed to establish the feasibility of producing and attaining target performance levels. Degradation of Ic in the cabled tapes, as compared to their pre-cabled Ic’s was found to be minimal. Bend tolerance tests on cables comprised of 8 tapes demonstrated that Ic does not start to decrease until bend diameters go well under 20 cm. Longer length cables were produce and test coils wound – with tests confirming that these cables are well suited for the fabrication of HTS-based coils with the required large operating currents. These developments pave the way to now develop and produce long lengths with many more tapes and achieve 2, 5 and 10 kA class cables for high field usage in a large variety of magnet types.

Speaker: Dr Alexander Otto (Solid Material Solutions, LLC)

921 Thu-Af-Or19-08: Experimental research of contact mechanical behavior among YBCO tapes in HTS cable

The HTS (high temperature superconductor) cable is an important component of large magnet system due to its excellent electromagnetic characteristics. The contact mechanical properties such as friction and contact resistance are significantly affected by the contact force among the HTS tapes in HTS cable when subjected to the strong magnetic field, high current, and low temperature in extreme working conditions. It is meaningful to improve the performance of large magnet system that study the contact mechanical behavior among YBCO tapes in HTS cable. This paper focuses on CORC and TSTC cable and TSTC cable, we conducted experiments to obtain the data of contact force and contact resistance and critical current degradation among YBCO tapes under different loads at room temperature (293K) and operating temperature (77K). The relations between contact force, contact resistance, friction and different loads are obtained by organizing experimental data. This work aims to search for the contact mechanical properties among the HTS tapes in operating conditions and provide the guidance of the optimization design and application of large magnet system.

Speaker: Mr Yang Liu (Lanzhou University)

Thu-Af-Or20 - Quench Detection and Protection Systems III

Conveners: Emmanuele Ravaioli (CERN), Matthias Mentink (CERN)

922 Thu-Af-Or20-01 [Invited]: Quench detection via Rayleigh backscattering interrogated optical fibers

The application of high temperature superconductors (HTS) for the generation of high magnetic field is still limited by technical issues like quench detection. The recently developed quench detection technique based on Rayleigh backscattering interrogated optical fibers (RIOF) has shown to provide unprecedented levels of detection and advantages over conventional, voltage-based approaches. In RIOF, the optical fiber is a distributed sensing element of temperature and strain. Strengths of the technique include immunity to electromagnetic noise, mm-level spatial resolution, long interrogation length, ease of integration and reduction of instrumentation wiring that goes into the magnet. In this talk, several optical fiber integration pathways will be illustrated, along with experimental results showing embodiments of each fiber integration approach. Integration approaches include fiber co-winding, SMART Conductor and SMART Cable. The RIOF technique is based on the comparison of Rayleigh backscattering signals of a reference and perturbed state. A spectral shift quantifies the mismatch between the two conditions, which depends on temperature and strain changes between the two compared states. All optical fiber integrations were demonstrated to be practical and effective. Results of quench detection experiments include HTS test coils with co-wound optical fibers, both pancake and layer wound, Canted Cosine Theta (CCT) coils with integrated optical fibers (co-wound approach), experiments with SMART (RE)Ba2Cu3O7-x Conductor and experiments with SMART CORC® Cables.
All results show that RIOF is a viable choice for quench detection and that it is able to detect and locate perturbations that are completely undetected via voltage taps. In addition to demonstrating that the system works as a detector of normal zones, the experiments also show the different advantages of the fiber optic system over a conventional, voltage-based one.
The work was funded by the U.S. Department of Energy via an STTR program.

Speaker: Dr Sasha Ishmael (Lupine Materials and Technology)

923 Thu-Af-Or20-02: Modeling and Experimental Validation of Quench Protection Concepts for Canted-Cosine-Theta Type High-Field Magnets

An innovative high-field superconducting magnet of Canted-Cosine-Theta (CCT) type has been proposed for Future Circular Collider (FCC) 16-T dipole magnet design. The unique mechanical structure intercepts the accumulated forces lowering the stress on the windings: intrinsic stress management in high-field Nb3Sn accelerator magnets. Nevertheless, the former itself also becomes a barrier for heat to quickly propagate in case of a quench. To succeed in the CCT-type magnet design and construction, the quench protection is a challenging task which requires detailed investigation of the electrothermal behavior of this magnet. In this paper, the potential detection and protection concepts are studied on both aspects of multiphysics simulations and experiments on a two-layer short model built at Paul Scherrer Institut (PSI). The 2D User-Defined Elements (UDEs) developed by LBNL in ANSYS Mechanical APDL, which support the multi-dependence material properties and include the effect of cable-eddy currents, are adapted and used in the coupled electrothermal, electrodynamic and electric circuits calculations for two-layer CCT-type magnets with different protection methods, such as Coupling-Loss Induced Quench (CLIQ) and Energy Extraction (EE) system. The simulation predictions and the experimental results are the first steps of the conceptual design and feasibility validation of the construction of a fast and efficient quench protection system of CCT-type magnets for accelerators.

Speaker: Jiani Gao (Paul Scherrer Institut)

Jiani_Gao_PSI_MT.pdf

924 Thu-Af-Or20-03: Acoustic sensor array for quench detection of CICC superconducting cables

HTS (High Temperature Superconductor) tapes such as REBCO (Rare Earth Barium Copper Oxide) are very attractive for various industrial applications of magnets and power-cables, especially for high field, high current superconducting magnets. An implementation of a sensitive quench detection for HTS devices is ungently desired for a safe operation, since normal zone propagations of a HTS conductor are very slow and the quench detection is difficult compared with other practical superconductors such as NbTi and Nb3Sn. Recently we have been proposing a unique acoustic quench detection method using tiny sensors distributed in a cooling channel of a superconducting conductor. A linear array of MEMS (micro-electro-mechanical system) microphone chips is installed along the coolant space of a CICC (Cable In-Conduit Conductor) superconducting cable in order to detect a quench and abnormal behavior by monitoring the coolant condition. The sensor array can make possible a fast and sensitive detection of quench location. In this paper the quench detection characteristics of a MEMS acoustic sensor linear-array in a CICC type REBCO superconducting cable made of a Twisted Stacked-Tape Cable (TSTC) will be discussed both experimentally and analytically including electrical and thermal response studies of a sensor array in 77 K gas and liquid nitrogen.
Acknowledgements:
This work supported by the U. S. Department of Energy, Office of Fusion Energy Science under Grants: DE-FC02-93ER54186.

Speaker: Makoto Takayasu (MIT)

925 Thu-Af-Or20-04: Quench protection of the 16 T Nb3Sn ERMC and RMM magnets

CERN launched a high-field magnet R&D program aimed at demonstrating 16 T class superconducting magnets for future circular colliders. The program includes designing, manufacturing, and testing two Nb3Sn magnet models, namely the Enhanced Racetrack Model Coil (ERMC) and the Racetrack Model Magnet (RMM). Both magnets target a magnetic field of 16 T with 10% margin on the load line at 4.2 K. The ERMC magnet is composed of two flat racetrack coils with no bore, whereas the RMM is composed of two ERMC coils and a middle coil, with a 50 mm bore.
The quench protection of a full-scale, high-field, Nb3Sn magnet is very challenging due to the high stored energy-density and relatively high margin to quench. Thus, an active protection system that quickly detects the quench onset and transfers the winding pack to the normal state is required to avoid damage due to overheating of the hot-spot where the quench started.
The protection of the ERMC and RMM magnets is based on conventional quench heaters glued to the coil and on CLIQ (Coupling-Loss Induced Quench), an innovative technology recently developed at CERN. CLIQ is composed of a charged capacitor bank, connected to the magnet via dedicated current leads. Upon quench detection, the capacitor bank is discharged into the magnet, resulting in fast oscillations of the currents in the coil sections. Thus, a high magnetic-field change is introduced, and hence high coupling loss is generated in the superconductor, which is quickly heated above its critical temperature. This method was successfully applied to 12 T Nb3Sn magnets.
The baseline quench protection system is demonstrated on the 1-meter-long ERMC model magnet. The test parameters are selected to be representative of a 15-meter-long magnet with a cross-section identical to RMM. Furthermore, a more optimized CLIQ design, featuring leads between the two layers of each pancake coil, is discussed. This design is more challenging to implement in the magnet design, but offers a significant improvement of the magnet quench-protection.

Speaker: Emmanuele Ravaioli (CERN)

MT26_QuenchProtection_eRMC_RMM_20190926_Ravaioli.pdf

MT26_QuenchProtection_eRMC_RMM_20190926_Ravaioli.pptx

926 Thu-Af-Or20-05: Quench simulations versus experimental observations on the HL-LHC MCBRD canted-cosine-theta short models and prototype magnets

In this paper, quench simulations on the High-Luminosity Large Hadron Collider (HL-LHC) MCBRD canted-cosine-theta (CCT) magnets are compared to experimental observations on the MCBRD short models and prototypes. These magnets feature insulated NbTi/Cu strands wound in aluminium formers, where two concentric coils held in place by the formers produce a dipole field over the bore.

The magnet quench protection strategy relies on a combination of energy extraction, current transformation to the conductive formers, and quench-back from eddy current heating in the formers resulting in the onset of a normal zone throughout the magnet. Without considering quench-back and current transformation, the protection of this magnet type solely by means of energy extraction would be very challenging, given that the voltage over a single energy extraction system during the discharge would be in the order of several kilo-volts for these high-inductance magnets. The experimental observations on the MCBRD prototype showed that the transient behaviour of the magnets during the discharge is strongly affected by the presence of super-fluid helium in between the formers, which affects quench-back in a detrimental manner. In this paper the manner in which these complications are treated in the quench simulations is discussed. Finally, the quench protection strategy and its implications for the D2 corrector circuits powering the MCBRD magnets are presented.

Speaker: Matthias Mentink (CERN)

Mentink - Quench Behaviour of the HL-LHC Twin Aperture Orbit Correctors, Simulations vs. Experimental Observations, MT26, 26-9-19.pdf

Mentink - Quench Behaviour of the HL-LHC Twin Aperture Orbit Correctors, Simulations vs. Experimental Observations, MT26, 26-9-19.pptx

Thu-Af-Or21 - Novel Applications and Power Applications

Conveners: Dr Mark Ainslie (University of Cambridge), Timothy Haugan (U.S. Air Force Research Laboratory)

927 Thu-Af-Or21-01: A Superconducting Demonstrator Magnet for Magnetic Density Separation

We present the NbTi magnet system that is currently being constructed at the University of Twente for the demonstration of superconducting Magnetic Density Separation (MDS) . MDS is a new recycling technology that allows to separate non-magnetic waste materials based on their mass density, by combining a ferrofluid with a vertical magnetic field gradient.
The major challenge in the design of the planar 1.5 m by 1 m large magnet system was to minimize the distance between the conduction-cooled racetrack coils and the ambient-temperature ferrofluid. This minimization leads to the conflicting requirements of a robust and stiff mechanical structure and of low thermal cryostat losses.
The paper focusses on the design choices that were made to bring the magnet and fluid as closely together as possible. One of these is the inclusion of room-temperature pillars that run through holes in the coil yokes. These pillars support the flat top plate of the vacuum cryostat, allowing it to be made thinner. Opting for conduction-cooling avoids the need of a double-walled cryostat, bringing a further decrease of the distance between the ferrofluid and the magnet. Extra design considerations arise from the attractive force between the coils and the ferrofluid, which places additional requirements on the mechanical structure.

This work is part of the research programme “Innovative Magnetic Density Separation for the optimal use of resources and energy“ with project number P14-07, which is (partly) financed by the Dutch Organisation for Scientific Research (NWO).

Speaker: Mr Jaap Kosse (University of Twente)

MT26_Kosse_MDS.pdf

928 Thu-Af-Or21-02: A Superconducting Space Magnet for Antimatter Spectrometer

Future spaceborne spectrometers for astroparticle detection need high bending power therefore, the use of superconducting magnets is the sole applicable solution. Space magnets require high reliability that, in turn, requires high stability. Avoiding liquid helium cryogenics is also an attractive feature. The use of high temperature superconductors (HTS) or magnesium diboride (MgB2) combines both the requirements. The paper describes an MgB2 magnet operating at about 10 K that will be one of the main components of a space antimatter spectrometer. The magnet is a large toroid that will host a silicon tracker inside the toroidal volume and a 3D isotropic calorimeter in the center. The inner and outer diameters are 1 m and 4.3 m, respectively. The magnet mass is about 1500 kg.

Speaker: Riccardo Musenich (INFN e Universita Genova (IT))

MT-26 Thu-Af-Or21-02.pdf

MT-26 Thu-Af-Or21-02.pptx

929 Thu-Af-Or21-03: Practical Design and Performance Analysis Results of the First MgB2 Magnets for Superconducting Induction Heater in Korea

A superconducting induction heater has been developed and commercialized as a high efficient preheater for the Aluminum, aluminum brass and stainless steel extrusion in Korea. Also, Supercoil had a first step for the commercialization of the SIH using MgB2 magnets in Korea. He created the ‘MAGHEET’ as the brand name of the induction heater using magnets such as HTS (high temperature superconducting) and MgB2 and permanent magnets and etc.
Conventional induction heaters with a large capacity to preheat the metal billets for the extrusion product such as copper, titanium and stainless steel have low energy efficiency below 60% due to the considerable loss from the copper coils. The MAGHEET is one of the efforts to improve their efficiency in industries.
Supercoil has developed two types of superconducting magnets for large scale SIH. One is HTS magnets. The other is MgB2 magnets. In this paper, we are going to introduce design specifications and performance analysis results of two types of the superconducting magnets under the same conduction cooling condition. The cooling time, excitation, magnetic flux density, thermal stability and quench characteristics of two superconducting magnets at the near 10 K were presented and compared.
The successful heating test results will be shown in the conference. The first commercial MAGHEET will be on a sale and introduced, too.

Speakers: Jongho Choi (Supercoil Co., Ltd.), Mr Chan-Kyeong Lee (Supercoil Co., Ltd. )

930 Thu-Af-Or21-04: Development of Superconducting-Magnetic-Energy-Storage (SMES) for Aerospace Applications

Electrical energy storage devices are critical components of electric power systems of every aerospace vehicle. They are needed for many functions, such as an electrical accumulator unit (EAU) to handle transient loads both on/off the buses, for emergency power during system failure, to provide high-power for pulsed loads, and as an energy source for electric-vehicle (EV) propulsion. Superconducting-magnetic-energy-storage (SMES) devices offer unique features for aerospace applications including the highest power densities known achievable > 100 kW/kg for both charge and discharge, 100% storage efficiencies for unlimited times, and virtually no degradation for up to 108 charge/discharge cycles for some designs.
This paper will describe about the functions of SMES for aerospace application, and provide a recent update on the development and performance of SMES and large magnets being developed and built. The development of supporting technologies needed to integrate SMES into aerospace vehicles will be presented. In-house computation of the design of SMES devices optimized for mass-specific energy densities will be shown, and compared with devices presently existing or being developed. The energy density of SMES was traditionally < 10 Wh/kg, however recent computational investigations indicate the energy densities could reach > 100 Wh/kg and be competitive with Li-batteries.

Acknowledgments: The Air Force Office of Scientific Research (AFOSR) and LRIR #18RQCOR100, and the U.S. Air Force Research Laboratory Aerospace Systems Directorate (AFRL/RQ).

Speaker: Timothy Haugan (U.S. Air Force Research Laboratory)

931 Thu-Af-Or21-05: Potential of Long Solenoid Coil as Superconducting Cable with Energy Storage Function

We have proposed a novel superconducting electric power system with energy storage function. This system will overcome the obstacles for future large-scale utilization of renewable energies by compensating their output power fluctuation. In particular, the potential of a long solenoid coil as a superconducting cable with energy storage function has been investigated in this study. This means that the superconducting cable can be used not only for highly effective power transfer but also for high-power energy storage compensating output power fluctuation from renewable energies. The research and development for this concept have been proceeded as a Japanese project since 2017 with a final target in 2050. The conceptual design of the superconducting cable and the operation of its small prototype in a hardware-in-the-loop simulation (HILS) will be presented.

This work was supported by the New Energy and Industrial Technology Development Organization (NEDO), JSPS KAKENHI Grant Number JP18K18864, and The Iwatani Naoji Foundation.

Speaker: Dr Kohei Higashikawa (Kyushu University)

932 Thu-Af-Or21-06: Design and Test of 40 kV / 2 kA DC Superconducting Fault Current Limiter

The resistive type superconducting fault current limiter (SFCL) is suggested to suppress the surge current in voltage sourced converter based HVDC (VSC-HVDC) power systems. The general design scheme of 40 kV/2 kA resistive DC SFCL is discussed firstly. Furthermore the electromagnetic analysis and structure design of the current limiting element are performed in emphasis. In order to study the current limiting performance of the DC SFCL under the rapid change of fault current, the dynamic simulation model and test platform are established. Finally, the current limiting and quench recovery properties of the SFCL are tested. According to the measurement results, the maximum impact current could be limited to 10kA, the largest resistance of SFCL module is about 2 Ω,and the quench recovery time could be controlled within 300 ms if the dc circuit breaker is switched off within 5ms.

Speaker: Qingquan Qiu (Institute of Electrical Engineering, Chinese Academy of Science)

933 Thu-Af-Or21-07: Development of a 220 kV/ 1.5kA Resistive Type Superconducting Fault Current Limiter

Within a collaboration of Jiangsu Zhongtian and Beijing Jiaotong University, one phase of resistive type superconducting fault current limiter (SFCL) for the 220kV transmission voltage level has been designed and manufactured. The active part of the SFCL consists of 128 bifilar coils made of 12mm wide steel-stabilized YBCO conductor supplied by Shanghai Superconductor, and is housed in a cryostat operated at normal state liquid nitrogen. The device was completely assembled and successfully subjected to steady-state tests, fault current limiting tests and high voltage tests, and the basic design of the system and the test results are reported. In total the SFCL passed 22 power switching tests at voltages between 10 and 20 kVrms , at various prospective fault currents between 10 and 63 kArms for a fault duration of 100 ms. The power frequency test at 360 kVrms for 1 min and lightning impulse test at 850 kV(1.2 μs/50 μs) were carried out according to the Chinese national standard GB 1094.3.

Speaker: Shaotao Dai (Beijing Jiaotong University)

16:00 Coffee Break

Thu-Af-Or22 - NbTi Accelerator Magnets III

Conveners: Dr Pierre Pugnat (CNRS - LNCMI), Toru Ogitsu (KEK, High Energy Accelerator Research Organization)

934 Thu-Af-Or22-01: Improvement in training performance by enhancing coil end support of the Beam Separation Dipole for the High-Luminosity LHC

The high-luminosity LHC upgrade (HL-LHC) aims to increase integrated luminosity by a factor of ten compared to the present LHC. To focus the beam more strongly towards the interaction point, superconducting magnets in the insertion regions must be upgraded. In the framework of CERN-KEK collaboration, KEK is in charge of developing a large150-mm-aperture beam separation dipole (MBXF). The field integral of 35 T·m with the nominal dipole field of 5.6 T is produced at the operating conditions of 12 kA and 1.9 K by a 7-m-long Nb-Ti based magnet. The design option of a single layer cos coil wound with 15-mm-wide Nb-Ti/Cu Rutherford cable was selected for maximizing iron volume and higher cooling capability. In such a thin and large-aperture coil, mechanical support against Lorentz force is one of the most important design considerations.
Three 2-m-long model magnets (MBXFS1–3) have been fabricated and tested at KEK. The test results of MBXFS1showed that the azimuthal coil pre-stress in straight section plays a major role in training performance. At coil end in this magnet, cable deformation towards the bore was observed after magnet test. To enhance cable support, wet-winding with radiation resistant resin was applied to coil end in MBXFS2. However, this could not perfectly prevent cable displacement. Quench start location concentrated on coil end in the early stage of training, suggesting that pre-stress at coil end was insufficient.
In this paper, we report training performance of MBXFS3, in which mechanical support of the cable at coil end is further enhanced. The influence of azimuthal pre-stress at coil end and axial pre-load on training curve will be discussed. A unique mechanical behavior found in the model magnets, hysteresis in the azimuthal coil pre-stress as a function of the current square during training quench, will also be presented.

Speaker: Michinaka Sugano

Thu-Af-Or22-01_Sugano_finalr.pdf

Thu-Af-Or22-01_Sugano_finalr.pptx

935 Thu-Af-Or22-02: Test of the first full-length prototype of the HL-LHC D2 orbit corrector based on Canted Cosine Theta technology

In the frame of the high-luminosity upgrade project (HL-LHC) of CERN for the Large Hadron Collider (LHC), a new double aperture beam orbit corrector magnets will be installed near the recombination dipole (D2). These 2.2 m long NbTi dipoles are built with the “canted cosine theta” (CCT) technique. The two independently powered apertures are oriented such that their field vectors are perpendicular to each other and to the direction of the beams. After constructing and testing a 0.5 m model magnet, a full-length double aperture prototype was built and tested at CERN in the SM18 test facility. Here we present the power tests at 1.9 and 4.5 K: training of each aperture, magnetic field quality and cross-talk effects, quench detection system effectiveness, quench protection performance and quench-back with several energy extraction systems.

Speaker: Franco Julio Mangiarotti (CERN)

Thu-Af-Or22-02_FJMangiarotti_Presentation_v02.pdf

Thu-Af-Or22-02_FJMangiarotti_Presentation_v02.pptx

936 Thu-Af-Or22-03: Cold tests of the first nested orbit corrector prototype for HL-LHC

The first prototype of the short orbit corrector MCBXFB for the upgrade of the LHC has been fabricated at CIEMAT, in collaboration with CERN, in the framework of the HL-LHC project. It consists of two nested dipoles, with an aperture of 150 mm and physical length of 1.5 m.
A first cold test was performed without the outer dipole coils, which were replaced by a support structure to align the iron yoke with the collared inner dipole. This test was aimed to validate the coil fabrication techniques, which are innovative for a NbTi Rutherford cable.
A second cold test was done with the full assembled magnet. It showed the successful performance of the mechanical clamping which holds the torque when both dipoles are simultaneously powered.
This paper describes the test results and the analysis of the measurements. The magnet is heavily instrumented: seven voltage taps per coil, six sections of collars with strain gauges and one coil per dipole with bullet gauges.

Acknowledgments
This work was partially supported by CERN under Contract KE-2292 and the Spanish Ministry of Science, Innovation and Universities.

Speaker: Luis Garcia-Tabares (Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT))

Thu-Af-Or22-03.pdf

Thu-Af-Or22-03.pptx

937 Thu-Af-Or22-04: Assembly and Test of MQYYM: a 90 mm NbTi quadrupole magnet option for HL-LHC

For the HL-LHC project, a 90 mm double aperture NbTi quadrupole magnet is being developed as an option to replace the 70 mm aperture LHC quadrupole MQY. This cos(2theta) magnet has an operating gradient of 120 T/m at 1.9 K and a magnetic length of 3.67 m. A single aperture short model magnet with a magnetic length of 1.2 m at 1.9 K has been designed at CEA and is being manufactured in collaboration with CERN. The magnet support structure is relying on self-supporting collars. We present here the mechanical analysis along with the assembly of the short model from coil mechanical characterization to collaring and yoking. In addition, warm magnetic measurements performed during assembly at CERN and preliminary cold tests results at CEA will be reported.

Speaker: Damien Simon (Université Paris-Saclay (FR))

Thu-Af-Or22-04-Simon.pdf

938 Thu-Af-Or22-05: FAIR’s first SIS100 Accelerator Quadrupole Doublet Module – Manufacturing Update and Test

The new and unique accelerator complex FAIR is currently under construction at GSI, Darmstadt, Germany. FAIR, the Facility for Antiproton and Ion Research, will investigate matter behavior inside stars, antimatter as well as biophysics questions using its variety of physics experiments. The core of this facility is the 1100 m circumference heavy ion synchrotron SIS100 featuring 100 T/m magnetic beam rigidity, which utilizes fast-ramped iron dominated superconducting dipole -, quadrupole - and corrector magnets cooled with 2-phase helium flow.
Two units consisting of each a quadrupole and a corrector magnet are integrated together with beam diagnostic elements into a common cryostat forming the so-called Quadrupole Doublet Modules.

The series production of the dipole magnets at Bilfinger Noell has reached half production stage with testing at GSI’s magnet test facility. In comparison, the complex Quadrupole Dublets Modules are produced and tested in several stages. At JINR Dubna, the units are manufactured and tested at 4 K. Afterword’s the units are shipped to Bilfinger Noell for the integrating those into modules which are, subsequently, tested at INFN Salerno for final acceptance before installation in the tunnel.

The first prototype Quadrupole Doublet Module is prepared in spring 2019 and an extensive testing campaign is planned at GSI in summer 2019. With the test, the complicated engineering of the Doublet Module itself is evaluated, before releasing the series production of 83 Quadrupole Doublets Modules. The 1st Quadrupole Doublet is instrumented with 200 sensors measuring temperatures, voltages, strain, and beam instrumentation. The vacuum and cryogenic behavior as well as ramp losses in static and dynamic operation following various SIS100 operation modes will be examined. The precision of the aligned magnetic axes of the two magnet units in the module will be investigated.
The complexity of the Quadruple Doublet magnets integration, the intensive acceptance processes and first results of the cold testing campaign at GSI are presented.

Speaker: Dr Anna Kario (GSI Darmstadt)

QDM_MT26_25092019.pdf

QDM_MT26_25092019.pptx

939 Thu-Af-Or22-06: Status of the SIS100 dipole magnet production and testing

A new international facility for antiproton and ion research (FAIR) is currently under construction in Darmstadt, Germany. The SIS100 heavy ion synchrotron, with a magnetic rigidity of 100 Tm, will provide the high intensity primary beam required for different research experiments. The synchrotron is composed of 415 fast cycling superconducting magnets from which 108 are dipole magnets. The first dipole magnet of the series was delivered to the test facility at GSI in September 2017. Each magnet is subject to a dedicated test program comprising the verification of the geometrical dimensions, electrical integrity and magnetic field parameters among others. The status of the dipole magnet production, the testing strategy and the statistical data obtained in almost half of the series dipoles tested will be presented.

Speaker: Dr Patricia Aguar Bartolome (GSI Helmholtzzentrum fuer Schwerionenforchung GmbH)

Tu-Af-Or22-06.pdf

940 Thu-Af-Or22-07: Optimization of an Interaction Region Quadrupole Magnet for Future Electron-Ion Collider at Jefferson Lab

The Jefferson Lab Electron Ion Collider (JLEIC) is a proposed new machine for nuclear physics research. It uses the existing CEBAF accelerator as a full energy injector to deliver 3 to 11 GeV electrons into a new electron collider ring. An all new ion accelerator and collider complex will deliver up to 200 GeV protons. The machine has luminosity goals of 10^34 cm^-2 sec^-1. The whole detector region including forward detection covers about 80 meters of the JLEIC complex. The lattice file for the machine has changed to accommodate the higher energy; this change requires all the magnets in the interaction region to change. This paper will describe the requirements for both the ion and electron beam superconducting magnets around the interaction point. All the Final Focusing Quadrupole (FFQ) magnets now have preliminary designs. This paper will describe the optimization process for one of these FFQs. The optimization is performed using the optimization module of Opera FEA. An analytical design tool has also been developed to estimate the peak field in the coils. The quadrupole is optimized for peak field in the coils, magnetic length and integrated multipole components.

Speaker: Dr Renuka Rajput-Ghoshal (Jlab)

MT26-Thu-Af-Or22-07_JLab_Renuka.pdf

MT26-Thu-Af-Or22-07_JLab_Renuka.pptx

Thu-Af-Or23 - Magnets for NMR and Medical Applications

Conveners: Iain Dixon (NHMFL), Seungyong Hahn (Seoul National University)

941 Thu-Af-Or23-01: Construction and Test Results of a Cryogen-Free 23.5-T REBCO Magnet Prototype towards a Tabletop 1-GHz Microcoil NMR Magnet

We are developing a tabletop 1-GHz microcoil nuclear magnetic resonance (NMR) spectrometer of compact, low-cost, and small-footprint features while having better peak resolution and sensitivity than conventional lower field NMR spectrometers, enabled by the high-temperature superconducting (HTS) REBCO no-insulation (NI) magnet. In this paper we present construction and test results of a cryogen-free 23.5-T REBCO magnet prototype operated at 10 K. This prototype aims to validate the conductor performance, coil design parameters, and a conduction-cooling towards a subsequent full-scale tabletop 1-GHz microcoil NMR magnet. This magnet prototype is a stack of NI pancake coils each wound with 128-m long REBCO conductor: the middle 10 coils adopt 6-mm width; and the end 2 coils adopt 8-mm width. A 0.2-mm thick copper sheet, inserted between pancake coils and thermally linked to an 8W@10K cryocooler, maintains a uniform temperature throughout the magnet. This paper includes: 1) winding and joint procedure; 2) individual pancake coil test results at 77 K in liquid nitrogen; 3) magnet assembly procedure with a conduction-cooled cryogenic system; and 4) charging and operating test results at 10 K. The paper concludes with a summary of enabling features validated by this prototype and discussion of additional issues to be further investigated and resolved towards a 1-GHz microcoil NMR magnet.

Acknowledgement: Research reported in this publication was supported by the National Institute of General Medical Sciences of the National Institutes of Health under award number R21GM129688.

Speaker: Dongkeun Park (Francis Bitter Magnet Laboratory / Plasma Science and Fusion Center, Massachusetts Institute of Technology)

Thu-Af-Or23-01-Park.pdf

942 Thu-Af-Or23-02: Development and charging test of a compact 1 GHz (23.5 T)-class NMR magnet with Bi-2223 inner coils

Abstract:
We have been developing a compact 1 GHz (23.5 T)-class LTS/HTS NMR magnet. There were two options of HTS inner coils, i.e. Bi-2223 or REBCO, and we decided to employ the Ni alloy-reinforced Bi-2223 conductors for the inner coils considering a smaller screening current-induced magnetic field of a Bi-2223 coil and its lower risk of unexpected degradation under high fields. The series-connected LTS/HTS coils are operated in a power supply-driven mode and designed to generate 1050 MHz (24.7 T) at 243 A. The total magnet size is very compact; it is comparable to that of a commercialized 600 MHz (14.1 T) NMR magnet and the total weight of the magnet is ~90% lower than that of a previously developed 1020 MHz (24.0 T) NMR magnet [1]. This compactness is owing to a high current density operation of the Bi-2223 inner coils, which contributes as much as 53% of the total magnetic field. This design concept with a high field contribution ratio by HTS inner coils has also been employed for the designs of a 1.3 GHz (30.5 T) NMR magnet [2].
We finalized the magnet design based on research and development including (i) Bi-2223 joint resistance in external magnetic field, (ii) tensile stress tolerances of the Bi-2223 conductor under bending condition, (iii) high compressive stress on Bi-2223 coils and (iv) effect of screening current-induced magnetic field on the field homogeneity and stability. In 2019, we will make a magnet charging test, stabilization and shimming for the magnetic field, and various NMR measurements including those for solid-state samples.
[1] Hashi et al, J. Mag. Res. 256 (2015) 30-33
[2] Maeda et al, submitted to IEEE TAS

Acknowledgements:
This work is mainly supported by the Japan Science and Technology Agency (JST) under the Strategic Promotion of Innovative Research and Development Program and partly by the JST-Mirai Program Grant Number JPMJMI17A2.

Speaker: Dr Yoshinori Yanagisawa (RIKEN)

MT26_Thu-Af-Or23-02_yanagisawa.pdf

943 Thu-Af-Or23-03: Operation and Performance Evaluation of a Conduction-Cooled 400 MHz/66-mm Metal-Clad No-Insulation All-REBCO NMR Magnet

Since 2014, an R&D program has been conducted to design, construct, and operate a 400 MHz 66 mm room-temperature bore all-REBCO magnet for high resolution NMR application. It is a collaborative program led by the Korea Basic Science Institute (KBSI) in participation of the Korea Institute of Machinery and Materials, Kunsan National University, National High Magnetic Field Laboratory, Seoul National University, and SuNAM Co., Ltd. The metal-clad no-insulation winding technique was adopted to reduce charging-delay without sacrificing the self-protecting feature of the magnet. Once successfully fabricated in 2018, the magnet was cooled down to the target operating temperature of < 20 K and charged to its rated field of 9.4 T at a nominal operating current of 187 A. After the charging test, we performed field-shimming by use of multi-layered ferromagnetic-shims and room-temperature active shims, after which a field uniformity of 0.2 ppm within 10 mm DSV (diameter spherical volume) was obtained. The well-known field-locking technique was also adopted to improve temporal field stability. Based on our own experience, we discussed a potential of our conduction-cooled no-insulation approach for GHz-class NMR magnets.

Speaker: Jae Young Jang (Korea Basic Science Institute)

944 Thu-Af-Or23-04: Optimal Design of HTS/LTS Hybrid Magnet for 25T NMR

With the increase of the magnetic field of NMR, the traditional LTS materials cannot meet the requirements of ultrahigh field NMR magnet design. In recent years, with the development of high-temperature superconducting tapes (especially ReBCO tapes), hybrid magnets with HTS magnets as interpolating magnets have become an important choice for designing ultrahigh field NMR magnets.
International research on the design optimization of ultrahigh field magnets is extensive, but most studies often do not fully consider the various limitations in magnet design, and the computational efficiency of the program is not ideal. In order to optimize the design of ultrahigh field NMR magnets in a more comprehensive, fast and efficient manner, in this paper, a code for design optimization of ultrahigh field NMR magnets based on HTS/LTS hybrid magnets was developed. The code is divided into global optimization phase and local optimization phase. The global optimization adopts Nondominated Sorting Genetic Algorithm II (NSGA-II) algorithm, and the local optimization adopts nonlinear programming NLP algorithm. The new code has a few differences compared to previous code:
1)Considering the problem that the helium gas bubble is trapped by liquid helium, which requires that the product of B_z and (dB_z)⁄dz is less than -2100T^2⁄m;
2)Considering the anisotropy of the ReBCO strip, the Br at the top and bottom of the magnet needs to be less than 2.85T;
3)More ReBCO tapes options, when designing HTS insert magnets, you can choose a hybrid design with different width (4/6/8/12mm) ReBCO tapes;
4)Structural optimization of the original code with parallel acceleration, which improves computational efficiency and saves computation time
In this paper, we optimized the design of the HTS/LTS hybrid NMR magnet with a central magnetic field of 25T (15T LTS background magnet + 10T HTS interpolated magnet) and a cold hole diameter of 32mm using the developed code. The design results were verified by commercial finite element software. The results show that the design of the magnet meets the basic design requirements

Speaker: Mr Dongquan Wang (Institute of Plasma Physics, Chinese Academy of Sciences)

945 Thu-Af-Or23-05: Excitation Test of Superconducting Magnet for 230MeV Isochronous Cyclotron for Proton Therapy

We are developing a superconducting isochronous cyclotron for proton therapy. Its yoke weight is about 65 tons, which is less than one third of our normal-conducting 230 MeV cyclotron.The sprit pair superconducting coils using NbTi wire are conduction-cooled by four 4 K Gifford-McMahon cryocoolers. Pure iron magnetic poles have deep valleys and four sectors with higher spiral angles than 60 degree. Designed average field is 4 T on extraction radius. We have achieved the nominal magnetic field generation without quench. We measured actual current dependence of inductance, and it agreed on computation. Forced quench test were performed to test protection circuit. Protection of the magnet was sucessful, and recovery time of the magnetic field generation was 17 hours.

Speaker: Dr Jun Yoshida (Sumitomo Heavy Industries, Ltd.)

OralPresentation_SHI_Yoshida_ver1_forUPLOAD.pptx

946 Thu-Af-Or23-06: Design and Test of a Curved Superconducting Dipole Magnet for Proton Therapy

A curved superconducting magnet for proton therapy was built and tested by the Superconducting Magnet Group at Lawrence Berkeley National Laboratory (LBNL). This magnet consists of two Canted-Cosine-Theta (CCT) dipole layers with a clear bore diameter of 290 mm, bend radius of 0.9 m, and magnetic bend angle of 50 degrees. The magnet design will be discussed in the context of a reduced bend angle prototype for a 135 degree bend system with large momentum acceptance beam dynamics. The fabrication of the magnet is then presented with a focus on the challenges associated with curved CCT mandrel manufacturing, winding, and assembly. Finally, the quench training and field quality measurements will be shown from a first test in liquid helium at LBNL. The relevance of these results and future tests are discussed in the context of conduction cooled operation of the full design.

Speaker: Lucas Brouwer (Lawrence Berkeley National Laboratory)

Brouwer_MT26_Thu-Af-Or23-06_vfinal.pdf

947 Thu-Af-Or23-07: Magnetic design of superconducting toroidal gantry for hadron therapy

Hadron and proton therapy are cutting edge techniques for cancer treatment and a great development of specialized medical centers and research facilities is foreseen in the next decades. One of the main obstacles to the penetration of the use of charged particles for therapy is the construction of complex and expensive accelerating structures and rotating transfer lines, i.e. gantries, able to bend and focus the beam down to the patient.
GaToroid is a novel concept of fixed toroidal gantry, able to deliver the dose at discrete angles in the whole range of treatment energies in steady-state configuration. The absence of magnetic field and current variations is an appealing feature, implying simplified demands on stability, powering, mechanics and cooling, as well as for the clinical prospective, allowing rapid variations of beam energy and treatment angle.
In this work, we present the magnetic design of the toroidal coils composing GaToroid, focusing the analysis on an option for a proton machine with energy range of 70 MeV to 250 MeV. To create a proper magnetic field distribution, the coils have been designed with peculiar asymmetric shape and the conductors have been graded. An initial winding geometry was obtained with an optimization aiming at maximum energy acceptance of the Gantry. We are now progressing to the detailed engineering design.
We describe here the coil and conductor layout (LTS and HTS options), and mechanical studies involving the general torus structure and the analysis of the stress on the coils. Quench protection is evaluated for LTS (Nb-Ti) configuration, as well as more innovative HTS (REBCO) options. Finally, we present the design and the construction of a scaled-down demonstrator, intended as the proof of principle of winding procedure and mechanical coil structure.
This Project has been funded by the CERN Budget for Knowledge Transfer to Medical Applications.

Speaker: Mr Enrico Felcini (CERN - EPFL)

2019_09_26_MT26_EF_16_9_v2.pdf

2019_09_26_MT26_EF_16_9_v2.pptx

948 Thu-Af-Or23-08: A Design Study on No-Insulation HTS Isochronous Cyclotron Magnet for Carbon Ion Therapy

Provided that a cyclotron system requires DC magnetic field, the no-insulation (NI) HTS magnet may be a good candidate as it may enable the cyclotron magnet to be more compact and reliable, yet generate a substantially higher magnetic field than its insulated counterpart. Here we report on a design study of a NI HTS cyclotron magnet for acceleration of carbon ions under isochronous condition up to an energy of ~400MeV/u. For beam stability, HTS coils having a designated field profile with the so-called “hill” and “valley” structure is proposed. After the initial design is completed, the proposed cyclotron magnet is analyzed using a 3D finite element method. This paper presents the magnet design and performance analysis results that include: (1) electromagnetic design of radially increasing magnetic field, a.k.a isochronous magnetic field; (2) charging-discharging scenarios; (3) mechanical stress analysis with potential use of an overband; and (4) post-quench behavior of the NI HTS coils.

Acknowledgement
This work was supported by the National Research Foundation of Korea as a part of Mid-Career Research Program (No. 2018R1A2B3009249).

Speaker: Jeonghwan Park (Seoul National University)

[MT 26] Thu-Af-Or23-08.pdf

Thu-Af-Or24 - Diagnostics and Test Results of Coils

Conveners: Emanuela Barzi (Fermilab), Michael Parizh (GE Global Research)

949 Thu-Af-Or24-01: Diagnostics and control of superconducting magnets using diffuse field ultrasound

Among various superconducting magnet diagnostics, acoustic techniques are valuable for characterizing mechanical instabilities associated with lengthy training, premature quenching and other performance limitations. While acoustic emissions from magnets were studied since early 80s, techniques involving external acoustic excitation have so far been of limited use. As such techniques are already well-developed in materials science and geosciences, they offer a great potential for the superconducting magnet applications. In a typical magnet coil an acoustic pulse emitted by a coupled ultrasonic transducer would experience multiple scatterings from boundaries and interfaces along its propagation path, in resemblance to a diffusion process. The resulting diffuse ultrasonic field uniquely "encodes" geometrical constrains, scatters locations and sound velocity distribution in the propagation medium. Variation of these properties can then be tracked in real time and with high accuracy by monitoring shape distortions and temporal shift of the ultrasonic waveforms acquired by sensors coupled to the coil. In this talk, key physical principles and capabilities of the diffuse field ultrasound will be discussed, and examples given of using it for detecting mechanical instability precursors and hot spot formation in various superconducting coils and sub-scale magnets developed by the US. Magnet Development program. Also, we will discuss application of the "time-reversal" acoustic method for the focused deposition of ultrasonic energy at a specific location inside the superconductor, aiming at a possibility of using it for magnet protection and mitigation of training.

This work was supported by the Director, Office of Science, High Energy Physics, and U.S. Department of Energy under contract No. DE-AC02-05CH11231.

Speaker: Maxim Marchevsky (Lawrence Berkeley National Laboratory)

950 Thu-Af-Or24-02: Magnet diagnostic utilizing stray capacitance monitoring on a 2 m long CCT coil

Superconducting magnets include various electrically-insulated metallic parts. The stray capacitance between these elements can be monitored and utilized to acquire information about the magnet condition and behaviour.
It is well known that dedicated capacitive sensors can be used to monitor the local strain. Furthermore, it was recently proposed to use a stray-capacitance monitoring system as a quench detection system for high-temperature superconducting magnets. The latter is based on the observation that part of the helium impregnating the insulation layers boils off when local heating occurs. Since the electrical permittivity of helium drops after its transition from the liquid to the gaseous phase, a stray-capacitance reduction is an indication of local heating of the conductor.
In this paper, we describe the application of a stray-capacitance monitoring system on a 2 m long, Nb-Ti, canted-cosine-theta (CCT) magnet tested in liquid helium at 4.2 K. The capacitance between one coil former and the magnet iron yoke was continuously monitored during powering and energy-extraction tests.
The effect of electro-magnetic forces on the measured capacitance was observed with good reproducibility. Furthermore, relatively fast capacitance reduction was observed after the energy-extraction was triggered. This result is an indication of local heating due to eddy currents in the former, coupling currents in the superconductor, and ohmic loss after a quench occurs.

Speaker: Emmanuele Ravaioli (CERN)

MT26_StrayCapacitanceMonitoringCCT_20190926_Ravaioli.pdf

MT26_StrayCapacitanceMonitoringCCT_20190926_Ravaioli.pptx

951 Thu-Af-Or24-03: Novel Characterization Technique to Visualize Local Defects in a REBCO Pancake Coil Winding

It is relevant to establish a reliable coil winding techniques which is free from local defects and/or delamination of REBCO tape strand. A coil is usually tested by measuring transport current-voltage characteristics as a whole, however, the position and distribution of the defects can not be identified from such global measurements. This prevent us from clarifying the mechanism of the degladation by the coiling. In this study, we have succeeded in developing a novel method to visualize local defects in a pancake coil winding with a high spatial resolution of a single tape thickness. This allows us to collect information on local degradation in the coil winding, i.e., a powerful method as a diagnostic technique in order to screening out a degraded coil. This is also very useful to investigate degradation mechanism and to improve coil winding methods. We adopted this method to investigate the properties of a large shielding coil used for a half-size REBCO based MRI magnet. Test results using an artificial tape stack including a single non-superconducting tape with a thickness of 100 um and the measurement results on the actual sheilding coil will be presented.
This work was supported by the New Energy and Industrial Technology Development Organization (NEDO).

Speaker: Takanobu Kiss (Kyushu University)

952 Thu-Af-Or24-04: "Thermal Eraser” to Mitigate Screening Current by Optimal Control on Temperature in an HTS Pancake Coil

This paper presents a method to mitigate screening current by manipulating temperature in a high temperature superconductor (HTS) pancake coil. Named as “Thermal Eraser”, it utilizes an electric heater that is optimally designed to “create” a target temperature profile in the HTS pancake coil. The key idea is to control field and temperature dependent critical current Ic (B,T) of “individual” turns in the HTS coil by an optimal operation of the heater, i.e., Thermal Eraser. Here we report: (1) principle of operation; (2) design of an electric heater that is dedicated to an REBCO test pancake coil; (3) construction and operation of the heater to demonstrate the feasibility of Thermal Eraser experimentally.

Acknowledgement
This work was supported by Samsung Research Funding & Incubation Center of Samsung Electronics under Project Number SRFC-IT1801-09.

Speaker: Jeseok Bang (Seoul National University)

Thu-Af-Or24-04_JeseokBang_ThermalEraser_F.pdf

953 Thu-Af-Or24-05: 25 K performance of conduction-cooled solenoids wound from exfoliated filament YBCO cables

Conduction-cooled magnets are gaining popularity as Helium reserves diminish. High-temperature superconductors, such as YBCO, can theoretically deliver ultra-high, > 20 T, magnetic field while cooled by an inexpensive and efficient single-stage GM cryocooler. At 20 K common materials still maintain high thermal conductivity, which ensures fast cooldown and fast recovery of a magnet after quench. Conduction cooled operation requires dense, void-free epoxy impregnation of the winding, preferably by post-winding infusion with a low-viscosity epoxy. The second generation, 2G conductors often degrade after epoxy impregnation due to separation of the YBCO layer from the substrate.
Here we report on tests of test solenoids layer wound from stacks of exfoliated YBCO filaments. We use 15 m of 2 mm wide, 8 filament cable to wind the largest, 6 layer coil. The solenoids are impregnated after winding with a low viscosity epoxies, Stycast 1266 and Henkel W19. We do not detect any critical current degradation after multiple rapid cooldowns from room temperature to 77 K. At 77 K the six-layer coil generated the maximum 0.12 T field, 200 A current. The central field hysteresis is well explained by the critical state model which assumes that the winding magnetization originates from in-plane superconducting current, with negligible coupling current contribution.
The coils were tested in a custom conduction cooled system at 25 K. The largest 6 layer coil were excited up to 1,300 A, generating 0.7 T field in the center. Our results suggest, that temperature gradients in the winding play a critical role in the magnetic field dynamic.
The work at Brookhaven Technology Group was supported by the Department of Energy, Office of High Energy Physics under SBIR Phase II award DE-SC0013856.

Speaker: Dr Vyacheslav Solovyov (Brookhaven Technology Group)

Solovyov Thu-Af-Or24-06.pdf

954 Thu-Af-Or24-06: Design and initial test results for a canted-cosine-theta dipole subscale magnet series

The U.S. Magnet Development Program is developing Canted-Cosine-Theta (CCT) magnet technology for future high field accelerator magnets. The CCT concept prevents Lorentz force accumulation by placing turns within precision-machined grooves that are separated by ribs and a spar that intercept forces, substantially reducing the stress in the conductor. CCT technology has been advanced through the fabrication and testing of three Nb3Sn CCT (CCT3/4/5) dipole magnets, with the final magnet reaching 88% of short sample current. A subscale CCT magnet program has been initiated in order to better understand and reduce training in this type of magnet. The goal of the nominal subscale design is to reach a similar stress state as for the CCT3/4/5 series at the short sample limit, with a reduced coil size in order to achieve reduced fabrication and testing time for dedicated training studies. A similar stress state can be obtained in the smaller, lower field magnets by operating near the peak of the Lorentz force curve for the superconductor, and by optimizing the coil geometry. For reference, the short-sample bore field is approximately 10 T for the CCT3/4/5 series with a 90 mm bore and approximately 5 T with a 50 mm bore for the subscale CCT series. The design and analysis for the nominal subscale magnet will be presented, along with results for the first set of subscale magnet tests.

This work was supported by the Director, Office of Science, High Energy Physics, and U.S. Department of Energy under contract No. DE-AC02-05CH11231 in the context of broader collaboration with the US Magnet Development Program.

Speaker: Diego Arbelaez (Lawrence Berkeley National Lab)

955 Thu-Af-Or24-07: Small solenoid made from round HTS superconducting cable

In the previous systematic research on short models of round CORC-like cables the range of design parameters like the core diameter, lay angle, pulling force etc. have been identified that should be respected in long-length cable production. Based on this knowledge we have manufactured 40 m long cable with two layers each comprising four Furukawa-SuperPower tapes 4 mm wide. Tapes are laid in helical manner with lay angle of 35 degrees on Cu tube with outer diameter 6.35 mm with production rate of 6 m/hour. The cable was then used to wind the solenoidal coil with four layers each containing 20 turns. The solenoid outer diameter was 18 cm. Measurements of individually energized tapes have been performed to check the retention of critical currents during cabling and coil winding procedures. Our tests confirm that one can completely exclude critical current degradation of any tape due to handling procedures.
Because of our CORT (Conductor-On-Round-Tube) design the central tube can be used for the flow of a coolant. We report on the measurements of coil performance at different temperatures and cooling regimes.

Speaker: Fedor Gömöry (Slovak Academy of Sciences)

Souc_Thu-Af-Or24-07.pdf

Friday 27 September

07:55 Registration Open (7:00 AM - 1:00 PM)

Fri-Mo-Or25 - Accelerator Magnets - Miscellaneous

Conveners: Damien Simon (Université Paris-Saclay ), Ramesh Gupta (BNL)

956 Fri-Mo-Or25-01: Progress in the development of superconducting undulators at the Advanced Photon Source

Development of superconducting undulator (SCU) technology continues at the Advanced Photon Source (APS). Recently, a new helical SCU has been added to the portfolio of two planar SCUs operating at the APS. The concept of a novel Superconducting Arbitrarily Polarizing Emitter, or SCAPE, has been suggested and tested in a prototype. Work on a long SCU which combines two up to 1.9-m long planar SCU undulator magnets in a 4.8-m long cryostat is in progress. In addition, an advantage of Nb3Sn-based undulator over NbTi-based SCU in generating higher undulator magnetic field will be demonstrated in a new project with a goal of developing and installing in the APS storage ring a Nb3Sn undulator. Description of these projects and their status are presented.

Speaker: Yury Ivanyushenkov (ANL)

Fri-Mo-Or25-01.pdf

Fri-Mo-Or25-01.pptx

957 Fri-Mo-Or25-02: Construction and Cold Test of the Superferric Skew Quadrupole for HL-LHC

INFN is developing at LASA lab (Milano, Italy) the prototypes of five corrector magnets, from skew quadrupole to dodecapole, which will equip the high-luminosity interaction regions of the High Luminosity-LHC (HL-LHC). These magnets are based on a superferric design, which allows a relatively simple, modular and easy to construct magnet. This activity takes place within the framework of a collaboration agreement between CERN and INFN. Four prototypes, from sextupole to dodecapole, have been built and tested starting in 2016.
We present here the last prototype of the high order correctors, to be installed in LHC, the skew quadrupole: magnetic and mechanical design are discussed together with quench protection.
We report also on the overall experience gained during construction aiming toward the series production. The power test of the quadrupole, including the training, the qualification and the quench behavior in operational conditions are also described.

Speaker: Marco Statera (INFN Milano - LASA)

Fri-Mo-Or25-02-Statera.pdf

Fri-Mo-Or25-02-Statera.pptx

958 Fri-Mo-Or25-03: Longitudinal gradient bend magnets for the upgrade of the Swiss Light Source storage ring

The photon beam brightness of synchrotron light facilities is increased by reducing the beam emittance. For the upgrade of the storage ring of the Swiss Light Source (SLS2), the lattice achieving a low emittance foresees longitudinal gradient bending (LGB) magnets producing high peak field values and quasi-hyperbolic field profiles to minimize emittance at locations of radiation.
Two types of technologies are studied: a 1.7 T peak field magnet based on permanent magnet materials (PM-LGB) and a superconducting version (SC-LGB) working at 4T peak field value to be upgraded to 6T in future. The baseline scenario consists in commissioning the SLS2 with 60 PM-LGB assemblies first and to exchange at a later stage three PM-LGBs by superconducting ones providing a higher peak field value. Thus, the design must foresee interchangeability. In this paper, we focus on the magnetic and mechanical design aspects of the PM-LGB and on the main mechanical constraints of the SC-LGB.

Speaker: Ciro Calzolaio (Paul Scherrer Institut)

MT26_calzolaio.pdf

959 Fri-Mo-Or25-04: Fabrication and test of Bi-2212 Canted-Cosine-Theta coils

Future accelerator magnets for producing 20 T and beyond will require using high temperature superconductors (HTS) in combination with low temperature superconductors (LTS). Under the U.S. Magnet development Program (US-MDP), LBNL is exploring the possibility of fabricating HTS insert dipoles based on Bi-2212 conductors, using the Canted-Cosine-Theta (CCT) technology, in order to increase the field of Nb3Sn outsert dipoles and reach 20 T in the bore. In order to address the technology challenges of this type of magnets, a Bi-2212 CCT prototype magnet, called BIN4, and two Bi-2212 CCT coils, called BIN5a and BIN5b, have been fabricated and tested. In a previous work, the main issues encountered during the winding process of the coils and the pre-oxidation cycle of the mandrels, together with the solutions we adopted, were presented. This work reports on the final stage of the fabrication process, including heat treatment, impregnation and instrumentation, and the test results. Additionally, the mechanical analysis and progresses towards testing another Bi-2212 CCT insert dipole, called BIN5c, in a background field of 8.5 T, is presented. The background field is produced by CCT5, a 90 mm bore Nb3Sn magnet fabricated at LBNL. Finally, the progress of technology development towards fabricating a 0.8 m long Bi-2212 CCT magnet that produces 5 T in the bore is investigated.

Speaker: Laura Garcia Fajardo (Lawrence Berkeley National Laboratory)

960 Fri-Mo-Or25-05: Presentation withdrawn

961 Fri-Mo-Or25-06: Epoxy and quench training of Nb3Sn accelerator magnets

Nb3Sn accelerator magnets are poised to play a key role at improving the luminosity of the Large Hadron Collider (LHC) at CERN by a factor of 5-10, significantly improving its potential for exploring physics beyond the standard model of particle physics. Nb3Sn porotype magnets, based on cosine-theta design, consistently need 10-25 quenches to achieve their best performance whereas a new canted-cosine-theta design being explored at our group demonstrates a longer training but fundamentally a similar behavior. The training of Nb3Sn magnets is a critical issue to solve for future high energy proton-proton colliders that need thousands of such magnets. Fundamental to this issue is the epoxy impregnated superconducting winding technology for which helium doesn’t penetrate into the winding and only provides cooling at surfaces, and superconductors are vulnerable to quenches trigged by heat associated with failures of epoxy and insulation fibers and at their interfaces with metals. In 2018, we showed that several epoxies have a higher toughness and less tendency to crack at low temperatures than CTD-101K, the epoxy resin using which nearly all Nb3Sn accelerator magnets have been impregnated. Here we continue to explore the questions of to what degree quenching training is contributed by the failure of epoxy and their interfaces with other components (wedges and mandrels) of the superconducting coil winding, and how advanced epoxies (high toughness, high thermoconductivity, high specific heat, or epoxy with improved bonding with metal interfaces) can play a role in reducing quench training of Nb3Sn accelerator magnets, through a combination of magnet inspections and analysis, multiphysics modeling, and comprehensive materials testing that includes tensile, compressive, shear tests, and shear/compression tests with advanced instrumentations.

The work is supported by the U.S. Department of Energy (DOE), Office of Science, Office of High Energy Physics under the framework of the US Magnet Development Program. The NHMFL is funded by the National Science Foundation (Award No. DMR-1157490), the US DOE (Award No. 227011-520-032288), and by the State of Florida.

Speaker: Tengming Shen (Lawrence Berkeley National Lab)

962 Fri-Mo-Or25-07: Analysis of the transient mechanics behind superconducting accelerator magnet training

Training is a long-standing problem hindering performance of high-field superconducting accelerator magnets. Proliferation of cracks in the epoxy impregnation and mechanical motion of the conductor in a stick-slip fashion are known to be the most common factors causing premature magnet quenching, and are also responsible for the training. Identifying and understanding those processes is thus essential for solving the training problem. By acquiring acoustic emissions and voltages continuously at a rate of 1 MHz during magnet ramping to quench, we have collected a large dataset of transient mechanical events in the recently tested canted-cosine-theta Nb3Sn dipole magnets CCT4 and CCT5 developed by the U.S. Magnet Development Program. Energy release in these events and their spatial localization were estimated and compared to the superconducting margin. Acoustic signals were further analyzed by creating their wavelet-based spectrogram representations and applying unsupervised machine learning techniques to learn a representation that allows for further downstream analysis, e.g. clustering, to identify events of different kind. We followed evolution of these clusters from one current ramp to another, and developed a qualitative picture of how the underlying mechanical processes define the training rate. After the test, the magnets were disassembled, coils cut and crack formations imaged, allowing for making a direct connection between the distribution of physical epoxy cracks and the acoustic data. The results will be used towards developing a neural network model capable of recognizing different types of transient mechanics in magnets, and providing a real-time feedback to magnet designers and operators on the expected course of training and its causes.

This work was supported by the Director, Office of Science, High Energy Physics, and U.S. Department of Energy under contract No. DE-AC02-05CH11231.

Speaker: Maxim Marchevsky (Lawrence Berkeley National Laboratory)

Fri-Mo-Or26 - Fusion VIII: ITER

Convener: Alexandre Torre (CEA)

963 Fri-Mo-Or26-01 [Invited]: Progress of ITER TF coil fabrication in Japan

QST, as Japan Domestic Agency in ITER, has responsibility to procure 9 ITER Toroidal Field (TF) coils and all 19 TF Coil Cases (CC). The 9 TF coils are procured by two suppliers to ac-celerate their production. The series production of Double-Pancakes (DPs) and Winding Pack (WP) are in progress in both two manufacturing lines. 1st WP have been completed and net three WPs are in fabrication. In addition, 6 CC have been completed. Assembly of the WP and CC started from beginning of 2019. The etails of the progress of these activities are presented.

Speakers: Norikiyo Koizumi (QST), Mio Nakamoto, Hideki Kajitani (National Institutes for Quantum and Radiological Science and Te)

Fri-Mo-Or26-01-Koizumi.pdf

964 Fri-Mo-Or26-02: Progress on European ITER Toroidal Field Coil procurement: Cold Test and Insertion Work Package

The plasma confinement of the International Tokamak Experimental Rector (ITER) is provided by the magnetic field generated by 18 toroidal filed coils (TFC). Fusion for Energy, the European Domestic Agency for ITER, is responsible for the supply of 10 TFC to ITER project.
Their procurement has been divided in three main work packages: I) the production of the radial plates, structural stainless steel components housing the Nb3Sn conductors, II) the manufacture of 10 Winding Packs (WP) and III) the cold test of 10 WP plus their insertion into the Coil Cases (CC).
This article gives an update of the status of the production of third and last work package performed under the framework of a F4E contract assigned to SIMIC SpA, an Italian company.
In particular the details of the WP thermal cycle, the insertion of the firsts TF coil in their coil cases, the closure weld, the gap filling and the machining strategy adopted to optimize the final TF coil shape optimized to minimize the field errors are presented.

Speaker: Boris Bellesia (Fusion for Energy)

965 Fri-Mo-Or26-03: Current Centre Line integration in the manufacturing process of the ITER Toroidal Field Coils

The first ITER’s European Toroidal Field Coil (TFC) is going to be assembled in 2019. The TFC is composed mainly by the superconducting Winding Pack (WP - manufactured in Europe), and the Coil Cases (TFCC - manufactured in Japan), which provide structural integrity to the magnet and offer interface connections with the rest of the machine.
Dimensional measurements and other manufacturing data are taken during the WP manufacture and are used to reconstruct the Current Centre Line (CCL), which is defined as the barycentre of the as-built conductors inside the WP. The CCL is useful to characterize the magnetic field generated by the magnet and its monitoring and control can minimize the field ripple during ITER operation.
Fusion For Energy (F4E) developed a method to calculate the CCL using manufacturing data. Since the CCL represents how different the WP is manufactured from its nominal perfect conductor layout, this deviation can be corrected where there is need of a more controlled magnetic field shape, namely in the straight inboard area of the D-shaped tokamak. That is why each WP position inside its respective TFCCs is optimized, compensating the deviations detected and maintaining an allowable gap between components for the subsequent welding and resin filling operation.
This paper presents the strategy followed by F4E to calculate the CCL and optimize the WP position inside the TFCC, by means of extensive CAD and CAE modelling activity. It explains also the data management process developed and followed to ensure configuration control of all the data inputs and outputs, coming from different sources and formats, and details the successful insertion operation on the first ever ITER TFC coil manufactured in Europe, and how in the future the updated CCL coil position will be used to define the final TFC machining, after the welding and gap filling operations.

Speaker: Marc Jimenez (Fusion For Energy)

MT-26-TFC-CCL&Insertion-v1.0.pptx

966 Fri-Mo-Or26-04: Preparation of the ITER Central Solenoid Assembly

The Central Solenoid (CS) is a key element of the ITER Magnet system, including six identical coils, called modules, assembled together to form a 4 m outer diameter, 13 m high solenoid. It is a superconducting magnet, using a 45 kA Nb3Sn conductor internally cooled by circulation of supercritical helium at 4.5 K with a peak field up to 13 T. It is enclosed inside a structure providing vertical pre-compression and mechanical support. Procurement of the components and the special assembly tooling of the ITER CS is the responsibility of US ITER, the ITER Domestic Agency of the USA, while the ITER Organization (IO) will carry out the assembly of these components.

US ITER has awarded several contracts since 2011 to supply seven modules, including a spare, structure components, and the special tooling required for the CS pre-assembly. All deliveries are scheduled with the objective to start the CS assembly at IO site early 2021. IO is now actively preparing this new phase.

The paper describes the general CS pre-assembly activities from modules stacking to the pre-compression at 210 MN. The special assembly processes and related tooling are detailed. A focus is given on the module lifting operation, the busbar joint assembly and the pre-compression.
For these last two processes, IO has investigated alternative assembly options. For the busbar joint, the baseline process is a soldered joint. An alternative option based on the compaction of indium wires is presented and compared with the baseline. The CS pre-compression baseline assembly process relies on the tightening of 45 multi-jackbolt tensioners (MJT). The qualification of this process on a mockup will be presented. In parallel, an alternative option using dedicated hydraulic tensioners has been studied and compared as a matter of cost, risk and schedule to the baseline process.

The views and opinions expressed herein do not necessarily reflect those of the ITER Organization.

Speaker: Thierry Schild (ITER IO)

Preparation of the ITER Central Solenoid Assembly - Fri-Mo-Or26-07 - Final.pdf

Preparation of the ITER Central Solenoid Assembly - Fri-Mo-Or26-07 - Final.pptx

Fri-Mo-Or27 - No-Insulation and Insulated REBCO Magnet Technology

Conveners: So Noguchi (Hokkaido University), Hubertus Weijers (NHMFL/FSU)

967 Fri-Mo-Or27-01: Current Status and Challenges in No-Insulation HTS Magnet Technology

It was a milestone to generate a record-high DC field of 45.5 T by use of a 14.4 T no-insulation (NI) REBCO insert, named Little Big Coil (LBC), operated in a 31.1 T resistive background magnet by the National High Magnetic Field Laboratory. The engineering current density of the NI REBCO insert was ~1200 A/mm2 at 45.5 T, nearly 6 times larger than that of the conventional insulated HTS coils, ~200 A/mm2, yet LBC did not experience electric burn-out upon a quench. However, it did experience various patterns of mechanical damages, which delivered us some insights to deepen our understanding of causes and mechanisms on the mechanical damages in ultra-high field HTS magnets. In this paper, we first summarize the state-of-the-art NI HTS magnet technology and its widespread applications beyond the high field laboratory magnets. Then we will discuss about recent lessons that we learned regarding the potential causes and the mechanisms on the mechanical damages in high field HTS magnets, not limited to NI.

Acknowledgement
This work was supported by the National High Magnetic Field Laboratory (which is supported by the National Science Foundation under NSF/DMR-1644779,DMR-1839796), and by the State of Florida. This work was also partly supported by the National Research Foundation of Korea as a part of Mid-Career Research Program (No. 2018R1A2B3009249) and the Samsung Research Funding & Incubation Center of Samsung Electronics under Project Number SRFC-IT1801-09.

Speaker: Seungyong Hahn (Seoul National University)

968 Fri-Mo-Or27-02: 30 T generation using an intra-layer no-insulation (LNI) REBCO coil in a 17 T LTS magnet

We aim to develop a persistent-mode 1.3 GHz (30.5 T) NMR magnet with a REBCO layer-wound (LW) insert, a Bi-2223 LW midsert and LTS LW outsert. Protection of the REBCO insert is of great importance and we have employed intra-layer no-insulation (LNI) method in a magnet design [1],[2]. In the present work, we developed a model magnet similar to the 1.3 GHz NMR magnet, i.e. REBCO/Bi-2223/LTS magnet, to demonstrate 30 T high field generation and protection of the REBCO insert from a thermal runaway. A LNI REBCO coil (i.d. 17.6 mm : o.d. 70 mm : length 40.1 mm) and a Bi-2223 coil (i.d. 80 mm : o.d. 124 mm : length 384 mm) were connected in series and charged in the cold bore of a 17.2 T LTS magnet. We achieved the center magnetic field of 30 T at the REBCO/Bi-2223 coil current of 265.6 A without normal voltage and discharged the coils. We made a charging test again and continued to increase the current of the REBCO/Bi-2223 coil. The REBCO coil eventually showed a thermal runaway at 289.6 A in 31.4 T which resulted in no degradation of the REBCO coil. These results provide a promising prospect of the 1.3 GHz NMR magnet with an LNI REBCO insert.

1] H. Maeda et al., IEEE Trans. Appl. Supercond. 29 (2019) 4602409
[2] Suetomi et al 2019 SuST 32 045003

This work is supported by the JST Mirai-Program Grant Number JPMJMI17A2.

Speaker: Mr Yu Suetomi (RIKEN/Chiba University)

Fri-Mo-Or27-02_oral_suetomi_submit.pdf

969 Fri-Mo-Or27-03: Control of contact resistance of a long length REBCO conductor

In a REBCO no-insulation (NI) magnet coil, the turn-to-turn contact resistance (Rc) determines the coil’s quench self-protection ability, charging delay time and the energy loss during field ramp. Therefore it is critical to control Rc to suitable values. In our previous investigation, we measured Rc at 77 K and 4.2 K under various contact pressures and pressure cycles, and studied the effect of surface coating on Rc. Based on our experiment on short stamp samples, we found a reliable technique to control Rc by oxidizing the surface of the copper stabilizer of REBCO tapes.
In this paper, we developed a prototype reel-to-reel REBCO oxidation system to demonstrate the ability to control Rc of long lengths REBCO conductor. We will present the technical details of the process. The effect of various process parameters will be discussed. In addition, we developed a method of controlling contact resistivity of a REBCO coil by using co-wind stainless steel tapes. In this case, the control of contact resistance is done, also in reel-to-reel fashion, by treating the surface of stainless steel tape. The result of REBCO coil made by these Rc control methods will be presented. Since the understanding of the surface chemical/mechanical process in contact resistivity control is the key to obtain reliable controllable Rc, surface chemistry of both oxidized REBCO and the stainless steel tape is also studied.

Acknowledgement
This work was performed at the National High Magnetic Field Laboratory, which is supported by National Science Foundation Cooperative Agreement No. DMR-1644779 and DMR-1839796, and the State of Florida.

Speaker: Dr Jun Lu (MS&T, NHMFL)

Fri-Mo-Or27-03 Lu REBCO contact resistance rev 1.pdf

Fri-Mo-Or27-03 Lu REBCO contact resistance rev 1.pptx

970 Fri-Mo-Or27-04: MI HTS Insert for Very High Field Magnet

Because nowadays high temperature superconductors (HTS) can carry very strong currents under a high strength magnetic induction at a low temperature, the generation of continuous magnetic fields in the 25 to 50 T range, unattainable with conventional superconductors, is becoming reality.
However, HTS magnets must be effectively protected against transition to the normal state (quench), currently one of the major bottleneck in their use.
Among the possible strategies, the metal-as-insulation (MI) winding technique allows managing the quench of the insert in such manner it will not lead to destruction. The co-winding of a superconductor with a metal ribbon, without isolation nor impregnation, allows the current to redistribute in the event of a local defect, conferring on the insert a self-protected character in case of quench. This self-protected character is shared with the uninsulated coil concept, but the additional turn-to-turn resistance brought by the metal co-wound ribbon reduces drastically the important time constant observed in uninsulated coils. Moreover, in addition to thermal protection, the metal ribbon participates to the mechanical strength of the coil.
The MI concept was tested convincingly with a two double pancake assembly up to a 20 T background field in a LNCMI resistive magnet. It produced a total magnetic field of 26.9 T with mechanical constrain above 800 MPa. Based on this work, a 10 T MI HTS insert was built. This assembly of 9 MI HTS double pancake has produced stably an additional 12 T for 45 mn in a background field of 8 T. We report on further tests up to 20 T of background field to generate a total magnetic field of 30 T.

ACKNOWLEDGMENTS: The authors acknowledge the support of the LNCMI-CNRS, member of the European Magnetic Field Laboratory (EMFL), and of the French National Research Agency (ANR) through the contracts ANR-10-LABX-51-01 (Labex LANEF) and ANR-14-CE05-0005 (NOUGAT project).

Speaker: Dr Xavier Chaud (LNCMI-EMFL-CNRS, UGA, INSA, UPS)

Fri-Mo-Or27-04-Chaud.pdf

Fri-Mo-Or27-04-Chaud.pptx

971 Fri-Mo-Or27-05: Thermal stability and mechanical characteristics of multiple no-insulation pancake coil system in high field magnets.

High temperature superconductor (HTS) no-insulation (NI) coil is widely applied on high field magnets. In a multiple coil system, the quench behaviour of one coil is considerably affected by other coils through electromagnetic coupling. Meanwhile, quench on one coil can induce a current and fields changing on other coils, which may leads to eddy loss and mechanical degradation on these coils. Both the eddy loss and mechanical degradation are possible induce quenches on these coils finally. However, this has never been elucidated so far. This paper is to understand this underlying process by modelling methods. A multi-physics models are developed for multiple NI coil system by coupling an equivalent circuit network model, a T-A formulation model, a thermal model, and a structural mechanics model. The hot spot quench and over-current quench on one coils is analysed in HTS magnet consisting of 20 NI HTS coils. The current, temperature and strain/stress of all the coils are calculated during the quench. Measures are discussed to improve the thermal stability of the NI HTS magnet. The results and modelling tool developed are very useful for the design and development of high field magnet consisting of NI coils.

Speaker: Yawei Wang (University of Bath)

972 Fri-Mo-Or27-06: Field and Voltage transient behavior in REBCO HTS coils up to the limiting critical current: Comparison between Experiment and Modelling

The development of ambitious REBCO HTS coils (Rare-EarthBiCaCuO High Temperature Superconductor) is faced by two commonly acknowledged issues: Protection against thermal runaway induced by local dissipative zones, and dynamic field homogeneity. These two problems stem from two specificities of REBCO Coated Conductors: significant spatial inhomogeneity of critical current density and large conductors with high aspect ratios. We developed modelling tools to represent both the electro-thermal phenomena leading to thermal runaway [1] and the electro-magnetic phenomena that governs the current density distribution [2] and therefore the transient voltage and field behavior in simple HTS coils. We showed that to avoid dangerous thermal runaway, dissipating voltage must be detected early, at a level comparable to the transient voltage due to magneto-electric effects, which therefore must be taken into consideration in the detection scheme.
Here we present the test of several coils of different sizes using such adapted detection scheme based on modelling, up to the appearance of dissipative voltage. Experiments were conducted both in standalone and under external field, with conductors formed from single tapes and in some cases bundled tapes. The validity of the approach is evaluated on these simple coils in terms of protection efficiency and predicted transient behavior. In a second time, the errors generated by simplifying hypothesis (homogenized conductor, simplified geometries) are quantified, as such kind of approximations may be required to handle bigger systems or obtain faster results at the preliminary design step.

[1] A. Badel et al., IEEE TAS (2019) in press.
[2] B. Rozier et al., SuST (2019) in press.

Speaker: Dr Arnaud Badel (Tohoku University)

Fri-Mo-Or27-06-Badel.pdf

Fri-Mo-Or27-06-Badel.pptx

973 Fri-Mo-Or27-07: Screening current and hysteresis losses in the REBCO inserts of the 32 T magnet using a T-A homogenous model

The 32 T all-superconducting magnet of the National High Magnetic Field Laboratory was successfully tested in December 2017 and it is expected to be available for users in 2019. This all-superconducting magnet, comprised of two HTS inner coils and five outer LTS coils, is the first superconducting magnet above 30 T and some 8 T beyond the current strongest superconducting magnet in use as a science instrument. One of the challenges facing this new magnet technology is the estimation of the screening currents, and the corresponding hysteresis losses in the two insert coils. These coils are made of more than 20,000 turns of insulated REBCO conductor connected in series. The modelling of such system is complicated due to the computational load. Up to now, only medium size magnets (a few thousands of tapes) have been successfully modelled with methods based on the H formulation of the Maxwell’s equations and the use of the Finite Element Method. In the present work, we propose a new model based on the T-A formulation of the Maxwell’s equations implementing a homogeneous technique to address efficiently the estimation of the current density distributions HTS insert coils. This new method allows modelling large-scale systems on personal computers with a low computation time and memory usage.

Speaker: Edgar Berrospe (Universidad Nacional Autonoma de Mexico)

Fri-Mo-Or27-07-Berrospe.pdf

Fri-Mo-Or27-07-Berrospe.pptx

974 Fri-Mo-Or27-08: Screening current effect on the stress/strain distribution of REBCO high-field magnets: experimental verification and numerical analysis

The screening current in REBCO coils has been proved to have an important impact on the field quality, which is critical for applications with high field homogeneity requirement, such as MRI and NMR. As demonstrated in ‘Little Big Coil’ experiments by NHMFL, the screening current in REBCO coils may also have a huge influence on its strain distribution, especially for high-field operations. A 9-T insert coil with a 34-mm outer diameter wound with 4-mm wide REBCO tapes was developed and tested. In standalone test, the SCF was found to be prominent with a 173-mT remanent field on the coil top when the coil was discharged from 9 T to 0. In order to study the strain distribution along the tape width, a 3-T insert coil with a 60-mm outer diameter wound with 12-mm wide REBCO tapes was designed and fabricated. Under a 15-T background magnetic field, the testing coil was charged up and down at 4.2 K, when strain gauges and hall sensors were setup to measure the local hoop strain in the outermost turns and the screening current field (SCF), respectively. Corresponding electromagnetic models and mechanical models were developed and compared against SCF and strain measurements, which also provided an insight into the mechanism of the effect of screening current. It is found that the screening current has a strong influence on both magnetic field and strain/stress distributions, which should be taken into account for the strain/stress estimation of high-field HTS magnets.

Speaker: Yufan Yan (Tsinghua University)

Fri-Mo-Or27-08-Yan.pdf

10:00 Coffee Break

Plenary: Brandon Sorbom (Commonwealth Fusion Systems)

Convener: Michael Parizh (General Electric)

975 Fri-Mo-PL6-01: Commercialization of Superconducting Technologies - CFS, MIT and High-field Fusion

MIT and Commonwealth Fusion Systems (CFS), a new startup company focused on the rapid commercialization of fusion, are jointly pursuing a privately-funded, accelerated approach to demonstrate the feasibility of fusion energy. The CFS/MIT team is currently developing a new generation of high-field, large-bore, REBCO-based superconducting magnets to incorporate into a compact net-energy tokamak called SPARC that will demonstrate net fusion energy gain. The key performance metrics in a tokamak scale as the strength of the toroidal magnetic field to the third or fourth power times the volume of the device. One of the most important consequences of these scalings is that increasing the magnetic field in a tokamak enables a much smaller device to demonstrate net-energy production, leading to dramatic reductions in cost, timeline, and organizational complexity required to construct and operate the fusion device. Thus, the development of high-field, large-bore REBCO magnets is existential for the success of the SPARC project and motivates an aggressive plan to scale up the existing supply base of REBCO coated conductors, build an HTS TF model coil, and test it within the next two years. Over the past year, the SPARC team has performed much of the groundwork to enable the magnet development project. On the technical side, the team has collaborated with HTS centers of excellence to evaluate/improve the performance of REBCO from leading manufacturers, designed and built our own HTS measurement facilities, and performed several cable-level tests both in-house and at the SULTAN facility. On the programmatic side, we have raised $115M of private capital, grown a combined MIT/CFS team of over 100 people working on the SPARC effort, built magnet development, construction, and testing spaces at both MIT and CFS facilities, and placed orders for several hundred km of REBCO coated conductor. This talk will present a summary of the work above and discuss plans for the future.

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If you are interested in receiving Dr. Sorbom's presentation from the MT26 Conference, please contact Dr. Sorbom by email at: brandon@cfs.energy.

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Speaker: Brandon Sorbom (Commonwealth Fusion Systems)

Contact Dr. Sorbom for his MT26 presentation by email at brandon@cfs.energy.

Plenary: Mark Bird (NHMFL/FSU)

Convener: Gen Nishijima (National Institute for Materials Science)

976 Fri-Mo-PL7-01: Recent Advances in Ultra-High Field Magnet Technology

If we define ultra-high field magnets as those that provide fields more intense than the 23.4 T available from low temperature superconductors, then we see tremendous progress being made worldwide in recent years. The peak field available for science in pulsed magnets has set a new standard (100 T, 2012) while dc resistive magnets continue to raise the bar as well (41.5 T, 2017). New resistive/superconducting hybrid magnets have been commissioned (Berlin 2015, Hefei 2016, Tallahassee 2016) with higher field ones in Grenoble and Nijmegen under construction. There is also, of course, an absolute revolution underway in superconducting magnets with the high temperature superconductors (HTS) finally finding their way into user facilities (Sendai 2017, Tallahassee 2019) and NMR magnet projects being initiated (MIT 30.5 T, Bruker 28.2 T, RIKEN 30.5 T). Newer applications such as axion detection are also being enabled by this revolution (Daejeon 25 T, 10 cm).
HTS magnets are finally becoming a reality! A Bi-2223 coil has been put into service at 24 T while insulated REBCO has reached 32 T. A test coil using no-insulation REBCO made 14 T in a 31 T background (45 T total) while dramatic improvements in Bi-2212 show great potential as well. The record field from a superconducting magnet rose from 23.5 T to 24 T to 32 T in less than one year. The previous 8 T increase required >40 years! The technology is evolving at an unprecedented rate! At the same time, costs show great promise of dropping which may enable this extraordinary technology to become fairly widespread.
These ultra-high field magnets use dramatically different technologies but still share central challenges such how to manage intense Lorentz forces as well as the required energy and power. The state of the art and challenges associated with further development of a variety of ultra-high field magnet systems if presented.

Speaker: Mark Bird (FSU)

Bird_Plenary_Fri_Ultra High Field 190927.pdf

12:00 Best Poster Awards, Closing & MT27 Announcement