CEC-ICMC 2017 - Abstracts, Timetable and Presentations

US/Central
Monona Terrace Community and Convention Center

Monona Terrace Community and Convention Center

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Description

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

Any individual presenting at and/or attending the Conference must be a registered participant. Click here for registration information.

The first character of the program number, C or M, represents the Conference designation, C for the CRYOGENIC Engineering Conference (CEC), M for the International Cryogenic MATERIALS Conference (ICMC). The second character, 1, 2, 3 or 4, denotes the day of the Conference: Monday, Tuesday, Wednesday or Thursday. The third and forth characters (Or or Po) indicate whether the presentation is in an oral or poster session. The last character, A-M, differentiates the sessions on a given day.

ALL AUTHORS are requested to electronically publish their Poster and Oral Presentations prior to or during the Conference.  Presenters of oral talks must also submit their presentation file to the Speaker Ready Room one (1) day prior to their scheduled presentation.

The Conference Program Book is now available, see left side navigation. The Technical Program detail is current as of June 13. Any changes as of June 13 will be added to an Update Sheet and handed out to Conference Participants at registration check-in.

All other conference information can be found at http://www.cec-icmc.org.

Support
• Sunday, July 9
• CSA Short Courses (08:00 - 17:00) Hall of Ideas - I, Rooms M/Q and N/R

Hall of Ideas - I, Rooms M/Q and N/R

• ICMC Short Course (08:00 a.m. - 12:00 p.m.) Hall of Ideas - E

Hall of Ideas - E

• 3:00 PM
Registration Open (3:00 - 8:00 p.m.) Reg Area 2, 3, 4

Reg Area 2, 3, 4

• 6:30 PM
Cryo Expo Open (6:30 - 8:00 p.m.) Exhibit Hall AB

Exhibit Hall AB

For a list of Exhibitors, please visit: http://www.cec-icmc.org/exhibit/exhibitors/.

• 6:30 PM
Welcome Reception (6:30 - 8:00 p.m.) Cryo Expo, Exhibit Hall AB

Cryo Expo, Exhibit Hall AB

• Monday, July 10
• 7:50 AM
Cryo Expo Open (9:00 a.m. - 5:00 p.m.) Exhibit Hall AB

Exhibit Hall AB

For a list of Exhibitors, please visit: http://www.cec-icmc.org/exhibit/exhibitors/.

• Opening & ICMC Awards (7:55 - 8:15 a.m.) Madison Ballroom

• Monday Plenary (8:15 - 9:00 a.m.) - Dr. Nateri Madavan, NASA Ames Research Center Madison Ballroom

Convener: Timothy Haugan (U.S. Air Force Research Laboratory)
• 1
A NASA Perspective on Electric Propulsion Technologies for Large Commercial Aircraft

This presentation discusses the NASA Aeronautics Advanced Air Transport Technology Project’s perspective on electric propulsion technologies for future generations of large transport aircraft. Recent system studies commissioned by NASA and other organizations have identified these technologies as promising approaches to dramatically reduce aircraft fuel consumption, noise, and emissions. These technologies are part of the Project’s overall research portfolio aimed toward developing ultra-efficient commercial aircraft in conjunction with alternative low-carbon propulsion and energy systems to enable safe and sustainable future growth in global aviation. It is anticipated that systems based on both room temperature and cryogenic electrical technologies will be needed in the future. In the near term, room temperature electric systems are likely to impact aviation by making their way onto smaller aircraft and by augmenting traditional propulsion systems on larger aircraft. Cryogenic technologies, including fully superconducting motors and generators in a superconducting and cryogenic electric grid, cryogenic inverters, low-AC-loss superconductors and lightweight cryocoolers, will likely be needed in the far term to deliver the several tens of megawatts of propulsive power needed for large transport aircraft. The presentation outlines the opportunities and challenges for electric, hybrid-electric, and related distributed propulsion technologies for commercial aviation, and describes some of the related concepts and enabling technologies that are currently being developed.

Speaker: Dr Nateri Madavan (NASA Ames Research Center)
• C1PoA - Pulse Tube Performance Exhibit Hall AB

Exhibit Hall AB

Conveners: Ali Kashani (Atlas Scientific) , Dr Alexander Veprik (SCd)
• 2
A power recovery cascade pulse tube cryocooler with displacer

Recovering the acoustic power from the Stirling-type pulse tube cryocooler is of great utility in improving cooling efficiency. In this paper, a two-stage cascade pulse tube cryocooler capable of power recovery is introduced and tested. A displacer, playing a role of phase modification and power transmission, is connected between a primary cooler and a secondary cooler. Experimental investigation was first conducted on the cooling performance of the overall system and the separated coolers. The pressure ratios and pressure waves at two sides of the displacer were then studied. The experimental results showed that displacer not only tuned the pressure wave phase but also amplified the pressure wave amplitude. To better understand the displacer, its mechanical resistance and displacement were further discussed. In addition, the power consumption ratio of the 1st cooler, the 2nd cooler and the displacer were presented. The experimental system achieved a total an exergy efficiency of 37.2 % and total cooling capacity of 371 W at 130 K.

Speaker: Jing yuan Xu (Technical Institute of Physics and Chemistry, CAS)
• 3
Design and test of the Stirling-type Pulse Tube Cryocooler

Stirling type pulse tube cryocoolers are very attractive for cooling of diverse application because it has it has several inherent advantages such as no moving part in the cold end, low manufacturing cost and long operation life. To develop the Stirling-type pulse tube cryocooler, we need to design a linear compressor to drive the pulse tube cryocooler. A moving magnet type linear motor of dual piston configuration is designed and fabricated, and this compressor could operated with the electic power of 100 W and the frequency up to 60 Hz. A single stage coaxial type pulse tube cold finger aiming at over 1.5 W at 80K is built and tested with the linear compressor. Experimental investigations have been conducted to evaluate their performance characteristics with respect to several parameters such as the phase shifter, operating pressure and operating frequency of the linear compressor.

Speaker: Dr Yong-Ju Hong (Korea Institute of Machinery & Materials)
• 4
Development status of a high cooling capacity single stage pulse tube cryocooler

Improvement of high temperature superconducting materials lead to a new development of various applications such as superconducting motor, superconducting power transmission cable and superconducting power generator, etc. Those applications require a high capacity and high reliable cooling solution to keep high temperature superconducting materials being around 80K.

In order to meet such requirement, Sumitomo Heavy Industries, Ltd. (SHI) has been developing high cooling capacity single stage pulse tube cryocoolers. In general, pulse tube cryocooler is more reliable than Gifford-McMahon cryocooler or Stirling cryocooler because there are no moving parts at low temperature.
We developed a prototype unit which can provide 364 W cooling power at 80 K and COP is 0.04. The parameters such as the flow smoother length, the regenerator size and the operating frequency, etc., are tested and optimized.

The latest development status and test results will be discussed in this paper.

Speaker: Takashi Hirayama (Sumitomo Heavy Industries, Ltd,Japan)
• 5
Glass Pulse-Tube Cryocooler

We report construction of a glass pulse-tube cryocooler with regenerator, pulse-tube, inertance tube and reservoir. The purpose of the device is as a teaching tool, and to generate curiosity. The glass system enables one to observe the inside of the cryocooler while it is operating, create curiosity for first-time observers, and encourage their subsequent questions and investigation. Frost forms on the outside of the cold head of the cryocooler since it is exposed directly to ambient conditions. However, observers cannot see any moving parts or fluid flow because the operating fluid, helium gas, is transparent. The dimensions of the glass regenerator have been determined using Regen 3.3 from given parameters of the conductive porous medium inside of the regenerator and a 150[K] target cooling temperature at the cold head. The geometry of the glass pulse-tube and glass inertance tube have been fixed using an approximate design method, and the entire system parameters checked using SAGE. The thickness of each glass component is based on a charge pressure of around 7[bar] and a pressure ratio of about 1.35. The dimensions of the after-cooler are calculated using ISOHX assuming a gas temperature of 300[K] at the inlet of the regenerator.

Speaker: Mr Zhiyi Jiang (University of Wisconsin-Madison)
• 6
High efficiency 40 K single-stage Stirling-type pulse tube cryocooler

A high efficiency single-stage Stirling-type coaxial pulse tube cryocooler (PTC) operating at around 40 K has been developed based on numerical simulation by SAGE software and previous experiment experience. The double-inlet and the inertance tubes together with the gas reservoir were adopted as the phase shifters. Under the conditions of 2.5 MPa charging pressure and 30 Hz frequency, the prototype has achieved a no-load temperature of 23.68 K with 330 W electric input power rejecting at 279 K. It can provide 5 W cooling capacity at 40 K when electric input power increases to 395 W, and 7.56% of Carnot efficiency has been realized. It only takes 11 minutes for the PTC to lower its no-load temperature at the cold end from 295 K to 40 K.

Speakers: Dr xianlin wu (Technical Institute of Physics and Chemistry, CAS) , Liubiao Chen (Technical Institute of Physics and Chemistry, CAS) , Dr Changzhao Pan (Technical Institute of Physics and Chemistry, CAS) , Prof. Junjie Wang (Technical Institute of Physics and Chemistry, CAS)
• 7
Influence of Regenerative Material on Performance of 6K Level High Frequency Pulse Tube Cryocooler

As very low temperature high frequency pulse tube cryocooler has been a hot topic in the field of pulse tube cryocooler, improving the cryocooler’s performance is a common goal of researchers. By integrating the former results, we found that regenerative material is a key factor for the improvement of pulse tube cryocooler’s efficiency. In this paper, some experi-ments were conducted to find the regenerative material which is suitable for 7K, besides this, methods of simulation and experiment were used to investigate the influence of stacking style for performance of 7K high frequency pulse tube cryocooler. Finally, the lowest temperature has dropped from 8.8K to 6.7K and more than 10mW cooling power is able to be provided at 8K with a two-stage thermal-coupled high frequency pulse tube cryocooler used. The results of the cryocooler create a possibility of space application for terahertz detectors.

Speakers: Mr Xiaoyong Li (Technical Institute of Physics and Chemistry, CAS) , Dr Yanjie Liu (Technical Institute of Physics and Chemistry CAS) , Mr Jingtao Liang
• 8
Measurements of a Parallel Channel Adjustable Inertance Tube

A recent modification to the cylindrical threaded adjustable inertance tube for pulse tube refrigerators links the two helical flow channels existing between the threads of the inner and outer screws in parallel. The phase shifting performance of an earlier design that was limited by fluid leakage occurring between the channels, is now significantly improved by connecting the two channels in parallel. Measurements of the phase shift angle over the entire operating range of the adjustable device are compared with existing models. The models predict a phase angle shift between pressure and flow waves that range from -65 degrees to +40 degrees with the new parallel flow path configuration. By comparison, the original design could only obtain a phase angle shift between 0 and -30 degrees.

Speaker: Mr Andrew Elmeer (University of Wisconsin-Madison)
• 9
Novel Simulation Model for GM type Orifice Pulse Tube Cryocooler

Numerical simulation models for GM type pulse tube cryocooler reported so far require pressure pulse as an input which does not take rotary valve geometry into the consideration and cannot predict the pressure ratio reduction while the cooling down occurs. The unique feature of the proposed model is that instead of fixed pressure waveform as an input to the numerical model, it is capable of calculating the pressure waveform from the flow area variation between stator and rotor of rotary valve. This makes the model capable of numerical simulation of the complete GM type pulse tube cryocooler system including the rotary valve. The present numerical model is based on conservation laws namely mass conservation and energy conservation for gas and solid. The complete model is solved using finite volume method with appropriate boundary conditions. The model is currently applicable to orifice mode of operation and does not take any losses into considerations. The effect of valve timing on cooling performance can be predicted by the model. As the cooling down takes place, the reduction in pressure ratio can be simulated by the model which helps to optimize the system performance by modifying the rotor geometry. The comparison between experimentally recorded waveform and simulated waveform shows the reasonable agreement between them.

Speaker: Prof. HEMANT NAIK (S. V. National Institute of Technology)
• 10
Numerical analysis of inertance pulse tube cryocooler with a modified reservoir

Pulse tube cryocoolers are used for cooling applications, where very high reliability is required as in space applications. It is achieved due to the absence of moving parts and lack of contaminations. The Pulse tube cryocooler requires an additional buffer volume depending on the temperature and cooling load. A miniature single stage Inertance Pulse Tube Cryocooler is proposed which operates at 80K to provide a cooling effect of maximum 1W. Coaxial Inertance pulse tube cryocooler with a modified reservoir is suggested, where the reverse fluctuation in compressor case is used instead of a steady pressure in the reservoir to bring about the desired phase shift between the pressure and the mass flow rate in the acceptor (cold tip). Therefore, the large reservoir of the cryocooler could replace the crank volume of the hermetically sealed compressor, and hence the cryocooler is simplified and compact in size. The Modified IPTC can be driven by a Helium compressor with a modified reservoir to become a linear compressor of Stirling-type. The components of the cryocooler consisting of a connecting tube, aftercooler, regenerator, acceptor, flow straightener, pulse tube, warm heat exchanger, inertance tube and the modified reservoir were designed and analysed. The associated losses consisting of the heat conduction through the walls of the regenerator, the pulse-tube, regenerator matrix, and radiation heat losses were taken into account. Each part of the cryocooler was analysed using Sage v11 and Ansys Fluent. The simulation results clearly show that there is about 50% reduction in the reservoir volume for the modified cooler when compared to coolers of its same kind.

Speaker: Dr Biju T. Kuzhiveli (National Institute of Technology Calicut)
• C1PoB - Cryogenic Power Cables and Leads I Exhibit Hall AB

Exhibit Hall AB

Conveners: Jonathan Demko (LeTourneau University) , Sastry Pamidi (CAPS/FSU)
• 11
Application on turbo brayton refrigerator for world first commercialization on HTS power cable system

LS Cable and System Ltd. (LS C&S) and Korea Electric Power Corporation (KEPCO) performed a project of “Development of Operating and Manufacturing Technology for applying 22.9kV HTS Cable to the Commercial Power Grid” by funding of the Ministry of Knowledge and Economy (MKE) from 2008 to 2013. Through the successful implementation of this project, LS C&S will install the 22.9 kV HTS cable system in Heungdeok-Shingal substations, Korea for the commercialization by early of next year for the first time in the world.
For the cooling system of this project, turbo brayton refrigerator and decompression system are adopted as a main system and back-up one respectively. These equipments has been manufacturing and testing of the performance at the factory. LS C&S will install this cryogenic cooling system in Heungdeok substation by this October. The detailed specifications of the cryogenic cooling system for this project are described in this paper

Speaker: Mr Yanghun Kim (LS Cable and Sysem)
• 12
Cryogenic Design of an Integrated Cooling System for Three-Phase SFCL

A cryogenic cooling system is designed for three-phase 23 kV 1.2 kA superconducting fault current limiters (SFCL) under development as part of the KEPCO New Energy Technology Program. The goal of this design is a compact, efficient, and reliable system applicable to a commercial product, based upon our successful operation of distribution level SFCL’s. The HTS components are immersed in three separate liquid-nitrogen cryostats and continuously refrigerated by two GM cryocoolers. In order to achieve the spatial uniformity in temperature and pressure around at 78 K and 0.3 MPa, three cryostats are connected each other by the tubes through which liquid or vapor nitrogen can flow. One GM cooler is located at the top of the cryostats for vapor cooling, and the other GM cooler is placed between three cryostats at the vertical height of liquid level for liquid cooling. The uniqueness of this design is to make an effective thermal connection between three cryostats for simultaneous cooling, as called an integrated cooling system. Three pairs of current leads and bushings are also designed, and the full details of thermal load calculation are presented for immediate manufacturing.

Speaker: Prof. Ho-Myung Chang (Hong Ik University)
• 13
Development of a lab-scale YBCO based High-Tc Superconducting Power cable

Since the discovery of High Tc Superconductivity in 1986, the technology of High Tc Superconducting (HTS) power cables is getting developed all over the world in a continuous manner for efficient transfer of electrical energy in power transmission. In view of the benefits that can be obtained from usage of HTS cables in future power transmission systems, Applied Superconductivity Laboratory, IIT Kharagpur, in collaboration with Central Power Research Institute (CPRI), Bangalore has developed a 1m. long lab-scale superconducting cable carrying 1 kA current at low voltages (~10 volts). Further, for testing the HTS cable under cryogenic conditions, a flexible co-axial cryostat made out of double walled SS bellows with multi-layer insulation, vacuum in the space between the walls and suitable end-connectors is fabricated. The Superconducting cable assembly containing HTS layer (2G YBCO HTS tapes wound helically around a copper former), PPLP dielectric and insulating layers cooled by liquid nitrogen is tested for superconductivity in the double walled flexible cryostat using an AC power supply (0-1500 Amps AC) and necessary measuring instruments (nano voltmeter, temperature controller). In the present paper, the Voltage – Current characteristic of the HTS cable along with its detailed development procedure is presented.

Speaker: Mr Sudheer Thadela (Indian Institute of Technology, Kharagpur)
• 14
High Temperature Superconducting Power Devices and Its Cryogenic Systems

Great achievements have been made in recent years on the development and manufacturing of high temperature superconductors (HTS) and its application to power system. A series of HTS power devices, including HTS power cable, HTS fault current limiter, HTS magnetic energy storage system, HTS transformer, and HTS motor, have been developed and demonstrated in grid. Different kind of HTS power devices may have different requirements for their cryogenic system, which is composed of a cryogenic container and refrigeration system. This report will focus on the R&D progress of the above-mentioned HTS power devices and its cryogenic systems, and look forward to the future development trend of the HTS power devices.

Speaker: Prof. Shaotao Dai (Beijing Jiaotong University)
• 15
Theoretical and Experimental Studies on a Cryogenic Thermal Storage in Superconducting Cable Terminations to Protect Against Unexpected Heat Loads

Cryogenic gaseous helium circulation has been demonstrated as a viable option for some high temperature superconducting (HTS) power system applications, particularly when lower operating temperatures (T < 65 K) are needed to achieve very high power densities. The feasibility of a superconducting integrated power system (SIPS) will depend on the development of necessary technologies that support power distribution such as high power terminations, circuit breakers, cryocoolers, and improved thermal insulation. Potential cryocooler failures and fault currents could lead to excessive heat loads at the cable terminations that need to be mitigated to maintain operability of the cable while contingency plans are activated. Gaseous helium cooled systems are particularly vulnerable for unexpected heat loads due to the low volumetric heat capacity. This study explores the possibility of designing the terminations with sufficient cryogenic thermal storage to mitigate unexpected heat loads. Incorporation of solid nitrogen storage anchored to the copper terminals of superconducting cables in the terminations is being studied as a solution. The thermal storage would maintain the operations of the cable for 5-10 minutes after a system contingency. The latent heat of the stored solid nitrogen and the heat capacities of both the solid and liquid phases are utilized for the required thermal storage. A self-contained system of thermal storage that utilizes activated charcoal in the external buffer to store nitrogen gas that condenses and solidifies during the normal operating conditions and evaporates during a heat surge is being studied as an option. This paper will present the results of cryogenic thermal modelling efforts using finite element analysis techniques. Experimental results on a model thermal storage system are used to validate the modelling results. The benefits of such cryogenic thermal storage on GHe cooled high temperature superconducting power distribution network for SIPS will be presented.

Speaker: Mr Nicholas Suttell (Florida State University)
• C1PoC - Aerospace Exhibit Hall AB

Exhibit Hall AB

Conveners: Peter Kittel (Retired) , James Tuttle (NASA / GSFC)
• 16
A Highly Reliable Cryogenic Mixing Pump with No Mechanical Moving Parts

This paper presents the design and preliminary test results of a novel cryogenic mixing pump based on the magnetocaloric effect. The mixing pump is developed to enable long-term cryogenic propellant storage in space by preventing thermal stratification of cryogens in storage tanks. The mixing pump uses an innovative thermodynamic process to generate a fluid jet to promote fluid mixing, eliminating the need for a mechanical pump. Its innovative mechanism uses a solid magnetocaloric material to alternately vaporize and condense the cryogen in the pumping chamber, and thus control the volume of the fluid inside the pumping chamber to produce pumping action. The pump is capable of self-priming and can generate a high pressure rise. This paper discusses the operating mechanism and design considerations of the pump, introduces the configuration of a brass-board cryogenic pump, and presents the preliminary test results of the pump with liquid nitrogen.

Speaker: Weibo Chen (Creare LLC)
• 17
Analysis of thermal stratification during initial active pressurization in a cryogenic propellant tank

The prediction of thermal stratification in a cryogenic propellant tank is necessary for the successful execution of space missions. For the reduction of pressuring gas mass, high temperature gas is used for pressuring which may leads to thermal stratification and hence self-pressurization. The different gravity conditions experienced by the propellant tank affect the thermal stratification. At higher accelerated condition during launch, gravity will be higher and stratification proceeds faster, during orbital insertion gravity will be very low which causes reduction in stratification. The rise in propellant temperature due to stratification leads to cavitation in pump which has to be avoided. So modeling of stratification in cryogenic tank is essential as the liquid propellant must meet the pump inlet condition. A CFD model which can simultaneously account for the heat exchanges within the propellant tank and also heat transferred from ambient during initial active pressurization phase is developed. The amount of ullage gas required, Effect of ullage gas temperature on the development of stratification, variation of pressure inside the tank etc is found out. The results show that, there will be reduction in pressure at the end of active pressurization which is due to phase change and reduction in vapor temperature. A MATLAB code has been developed to investigate thermal stratification during initial active pressurization. It is found that there is fair agreement between the results obtained from the MATLAB code and CFD simulation.

Speaker: Dr Biju T Kuzhiveli (National Institute of Technology Calicut)
• 18
Cryogenic thermal emissivity measurements on small-diameter stainless steel tubing

The cooling line for the mechanical cryocooler for the Mid Infrared Instrument (MIRI) aboard the James Webb Space Telescope (JWST) consists of several meters of small-diameter stainless steel tubing at a normal operating temperature of about 18 Kelvin. Over much of its length this line is surrounded by surfaces at significantly higher temperatures, so it is gold-plated to minimize absorption of thermal radiation. However, the length located inside the blanketed thermal volume containing the JWST science instruments is not gold-plated. Periodic warming of the entire cooling line via cryocooler recycling is required to evaporate water frozen onto the outer surface of the gold-plated tubing. During this process, the line’s temperature will be held for an extended period of time at a temperature as high as 200 Kelvin, and the amount of thermal energy radiated onto surfaces near the instruments is a concern. Thus, it was deemed important to measure the total hemispheric emissivity of the un-plated tubing used in the cooler line as a function of temperature. We describe the measurement technique and present the results.

Speaker: Dr Amir Jahromi (NASA/GSFC)
• 19
Simulation test on the performance of thermodynamic vent system with R123

Although thermodynamic vent system (TVS) has been the promising pressure control technique for the long term on-orbit storage of cryogenic propellant, the current technology readiness level of TVS is still very low, thus it is essential to conduct in-depth research on TVS. In the present study, one experimental rig is built to research the performance of TVS with R123. The tank pressurization, mixing injection and throttling refrigeration phases are separately performed with the external heating power of 795~810W and the initial liquid height of 0.595m. The results show that during the pressurization phase, the tank pressure rise rate is approximately 60.583kPa/h. While the circulation volume flow is 150L/h and the throttling ratio 11.73~13.33%, the throttling refrigeration operates 8 cycle with the total venting gas loss of 20.536kg. The corresponding refrigeration capacity of TVS is in the range of 1127~1362W. Moreover, great fluid thermal stratification forms in the pressurization phase with the maximum temperature gradient appearing in liquid-vapor interface. The liquid thermal stratification is fully developed in the mixing injection phase with 5.48 hours’ consumption for the present experiment. Great refrigeration ability of TVS is showed with the liquid temperature limited in 1.98oC, during the throttling refrigeration phase. Once the operation of TVS finishes, the experimental system is under the free cooling of the external environment air. The effect of injection cold fluid on the vapor temperature distribution has lasted 15min. Then the vapor has a parabolic temperature distribution for lasting about 45min. Under the long time free cooling, a linear vapor temperature distribution is finally formed with the minimum value on the top and the maximum value in the interface. While for the liquid, all test points’ temperature reduce with time. It has saved 41% exhaust loss for 2 hours’ operation of TVS, compared with the direct venting gas approach.

Speaker: Prof. Yanzhong LI (Xi'an Jiaotong University)
• 20
Spectral Mass Gauging of Unsettled Liquid with Acoustic Waves

Propellant mass gauging is one of the key technologies required to enable the next step in NASA's space exploration program. At present, there is no reliable method to accurately measure the amount of unsettled liquid propellant in a large-scale propellant tank in micro- or zero gravity. Recently we proposed a new approach to use sound waves to probe the resonance frequencies of the two-phase liquid-gas mixture and take advantage of the mathematical properties of the high frequency spectral asymptotics to determine the volume fraction of the tank filled with liquid. We report the current progress in exploring the feasibility of this approach in the case of large propellant tanks, both experimental and theoretical. Excitation and detection procedures using solenoids for excitation and both hydrophones and accelerometers for detection have been developed. 5% accuracy for mass-gauging was demonstrated for large (100-liter) tanks filled with water for various unsettled configurations, such as tilts and artificial ullages. A new theoretical formula for the counting function associated with axially symmetric modes was derived. Scaling analysis of the approach has been performed to predict an excellent performance for in-space applications and environment.

Speaker: Dr Ali Kashani (MEI Company)
• 21
Vapor Shroud for Liquid Hydrogen Fueling of an Unmanned Aerial Vehicle (UAV)

Filling a vehicular liquid hydrogen fuel tank presents the potential for flammable mixtures due to condensed oxygen from liquid air condensation. Current liquid hydrogen tank designs utilize insulating paradigms such as aerogel/fiberglass materials, vacuum jackets, or inert gas purge systems to keep the outer surface from reaching the condensation temperature of air. This work examines the heat transfer at the refueling connection of the tank to identify potential areas of condensation, as well as the surface temperature gradient. A shrouded inert gas purge was selected to minimize vehicle weight and refueling time. The design of a shrouded inert gas purge system is presented to displace air preventing air condensation. The design investigates 3D printed materials for an inert gas shroud, as well as low-temperature sealing designs. Shroud designs and temperature profiles were measured and tested by running liquid nitrogen through the filling manifold. Materials for the inert gas shroud are discussed and experimental results are presented with suggestions for future design improvement.

Speaker: Kevin Cavender (Washington State University)
• C1PoD - Pumps, Compressors and Expanders Exhibit Hall AB

Exhibit Hall AB

Conveners: Rich Dausman (Cryomech, Inc.) , Sonny Yi (The Aerospace Corporation)
• 22
CFD Research on Hydrodynamic Gas Bearings with Different styles of Grooves

Gas bearings are an appealing technology which is widely used in turbo-machine in large cryogenic systems due to its inherent characteristic of oil-free and high-speed capability. The hydrodynamic gas bearings are more effective to cryogenic system but less load capacity and dynamic stability by compared with externally pressurized gas bearings. Etching some grooves on shaft or bearing is proved to be effective by experiments to improve its static and dynamic performance. Due to the hydrodynamic gas bearing performance parameters, such as load capacity and stiffness, are dominated by styles and geometric parameters of groove. In this paper ，the effect of groove styles and geometric parameters to the performance parameters of hydrodynamic gas bearings was presented. And a new style of groove was designed which can effectively improve the static and dynamic performance. we conclude that based on calculation of CFD: geometric parameters of groove do have some influence on static and dynamic of hydrodynamic gas bearings, for each parameter of groove there is a best optimal objective value which makes load capacity and stiffness maximum; The new style of groove presented in this paper has better static performance than spiral style and π-style groove.

Speaker: Prof. J. H. Wu (Technical Institute of Physics and Chemistry, Chinese Academy of Sciences)
• 23
Control strategy of helium twin screw compressor unit for large cryogenic system

The twin screw compressor unit has become more and more popular than other types compressor units in large helium cryogenic system. And the new application with helium as the working medium for the screw compressor unit has some technologies to be refreshed for adapting the large helium cryogenic system. The technologies refer to the rotor profiles, oil-injection parameters, oil separation device and control strategy. The control strategy including control logic, unit warning and unit alarming is introduced in this paper. The strategy was tested with the twin screw compressor test rig. And the results indicated the strategy can be successfully used in the large helium cryogenic system.

Speaker: Dr Bingming Wang (CAS Key Laboratory of Cryogenic, Technical Institute of Physics and Chemistry)
• 24
Design and performance assessment of Cold compressor for typical Cold Box of the large tokamak machine

The Cold Compressor (CC) is used to lower the saturation temperature of liquid helium (LHe) in varying heat load condition from the application side i.e. Superconducting Magnet and Cryopumps for large tokamak machine. The CC is a key component of typical cold box, attached to the LHe bath, compresses and transfers the vapor generated during the heat exchange via Heat Exchangers as well as the flash generated downstream from the Joule-Thomson (JT) valve connected to the cryoplant.
Emphasis of the present paper is on the conceptual design and performance assessment of the CC. The CC is designed to pump ~0.33 kg/sec of 4.2 K saturated helium vapor at a pressure ratio of ~1.39; with an off-design range of 0.2 to 0.5 kg/sec. Operating speeds are between 10 and 40 krpm, with a speed of ~16 krpm at the design point. Due to different heat loads from superconducting magnets and cryopumps, different process pressure and flow rates of the CC for large tokamak machine are expected. Hence, an important component of CC such as impeller design with blade profile generation has been carried for the higher efficiency of the CC. Characteristics curves of the CC have been obtained at different speed together with system characteristics curve. The study result of the surge and choke conditions of the CC for the stable operation of the system is also presented in the paper. Analysis has been carried out using computational fluid dynamics code to analyze various situations during real operation.

Speaker: Dr Hyun-Sik Chang (ITER Organization)
• 25
Experimental investigation on charcoal adsorption for cryogenic pump application

Fusion reactors are generating energy by nuclear fusion between deuterium and tritium. In order to evacuate the high gas throughputs from the plasma exhaust, large pumping speed systems are required. Within the European Fusion Programme, the Karlsruhe Institute of Technology (KIT) has taken the lead to design a three-stage cryogenic pump, featuring an 80 K thermal radiation shield, and two charcoal coated pumping stages; at 15K – 22K for hydrogenic species adsorption and at 5K for helium (a product of the fusion reaction) adsorption. This configuration can provide a separation function of hydrogen isotopes from the remaining gases, thus tritium can be internally recycled and reinjected, limiting its inventory in the machine.
The pumping speed relates directly to the interaction between the gas and the sorbent, characterized by the sticking coefficient which depends on a complex way on the nature of the couple gas-sorbent, the sorbent and gas temperatures, the gas pressure, the specific flow rate to the sorbent surface, and the surface coverage. Since literature related to this topic is scarce and inconsistent, a dedicated experiment was conducted in the large cryogenic vacuum TIMO-2 facility at KIT. A test pump consisting in a charcoal coated panel equipped with electrical heaters for temperature regulation between 5K and 25K, and housed by an 80K thermal shield and inlet baffle, has been tested under various gases, gas mixtures and gas flows with two different geometrical configurations.
The influences of the panel temperature, the specific flow rate to the charcoal surface and the incoming gas temperature on the pumping speed have been characterized. After a description of the experimental set-up, experimental results are discussed and open questions are addressed. In a future work, supporting Monte Carlo simulations should allow for derivation of the sticking coefficient values by comparisons with the experimental results.

Speaker: Mr Matthieu Scannapiego (Karlsruhe Institute of Technology)
• 26
SNS Cryogenic Test Facility Kinney Vacuum Pump Commissioning and Operation at 2 K

The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL) has built and commissioned an independent Cryogenic Test Facility (CTF) in support of testing in the Radio-frequency Test Facility (RFTF). Superconducting Radio-frequency Cavity (SRF) testing was initially conducted with the CTF cold box at 4.5 K. A Kinney vacuum pump skid consisting of a roots blower with a liquid ring backing pump was recently added to the CTF system to provide testing capabilities at 2 K. System design, pump refurbishment and installation of the Kinney pump will be presented. During the commissioning and initial testing period with the Kinney pump, several barriers to achieve reliable operation were experienced. Details of these lessons learned and improvements to skid operations will be presented. Pump capacity data will also be presented.

Speaker: Brian DeGraff (ORNL)
• 27
Structure design and dynamics simulation study of active magnetic bearing for helium centrifugal cold compressor

Introduction of application and characteristics of active magnetic bearing for helium centrifugal cold compressor is present. With the analysis and simulation of control system, a final solution of the magnetic bearing structure is obtained through entire scheme of AMB design and parameter selection for a cold compressor with helium mass flow 30g/s, which is now being developed at TIPC, CAS. Meanwhile simulation study on electromechanical coupling dynamics of the magnetic bearing rotor system is carried out.

Speaker: Prof. Jihao Wu (University of Chinese Academy of Sciences)
• 28
The development of helium turbo expanders for a 250W helium refrigerator

Recently a prototype of 4.5K helium refrigerator with capacity of 250W cooling power is under developing in Technical Institute of Physics and Chemistry (TIPC), CAS China. The helium refrigerator is a modified Claude cycle refrigerator, two helium turbo expanders were dedicatedly designed and fabricated to meet the requirements of Claude cycle helium refrigerator. Reliable static gas bearings are used to support the expander shafts at speed of 230 krpm. During the commissioning, the adiabatic efficiency of two turbo expanders are about 65%, the cooling capacity of the helium refrigerator is 270W.

Speaker: Dr Lianyou Xiong (Technical Institute of Physics and Chemistry, CAS)
• 29
The influence of seal clearance on the performance of stirling cooler

It is an important factor the resonance between the compressive piston and expansive piston that influence the performance of stirling cooler. Moreover, the seal clearance between the displacer and expansive shell influences the resonance characteristic of displacer. There may be contact and friction between the displacer and expansive shell because of their slight seal clearance. It could influence the dynamic characteristic of displacer and the performance of the cooler. In the paper, the assembling state of displacer and expansive shell was investigated. The impacts of parameters ( for example, the friction coefficient and the quantity of seal clearance ) on the performance of stirling cooler were analyzed. The results can improve the performance, lifetime and reliability of stirling cooler.

Speaker: Dr Zheng Wang
• C1PoE - Telescope Systems Exhibit Hall AB

Exhibit Hall AB

Conveners: Vince Loung (Lockheed Martin MFC Santa Barbara Focalplane) , Peter Shirron (NASA/GSFC)
• 30
An extremely high stability cooling system for planet hunter.

The detection of exoplanets is done by measuring very tiny periodical variations of the radial velocity of the parent star. Extremely stable spectrographs are required in order to enhance the wavelength variations of the spectral lines due to Doppler effect. CARMENES is the new high-resolution, high-stability spectrograph built for the 3.5m telescope at the Calar Alto Observatory (CAHA, Almería, Spain) by a consortium formed by German and Spanish institutions. This instrument is composed by two separated spectrographs: VIS channel (550-1050 nm) and NIR channel (950-1700 nm). The NIR-channel spectrograph's has been built under the responsibility of the Instituto de Astrofísica de Andalucía (IAA-CSIC). It has been manufactured, assembled, integrated and verified in the last two years, delivered in fall 2015 and commissioned in December 2015.
Beside the various opto-mechanics challenges, the cooling system was one of the most demanding sub-system of the NIR channel. Due to the highly demanding requirements applicable in terms of stability, this system arises as one of the core systems to provide outstanding stability to the channel at an operating temperature finally fixed at 140K. Really at the edge of the state-of-the-art, the Cooling System is able to provide to the cold mass (~1 Ton) better thermal stability than few hundredths of degree within 24 hours (goal: 0.01K/day).
The present paper describes the main technical approach, which has been taken in order to reach this very ambitious performance. The last section includes the first results measured on the instrument in real operation at the telescope.

Speaker: Mr Jean Louis Lizon a l'Allemand (European Souther Observatory)
• 31
An Hybrid liquid nitrogen system to cool a large detector.

OmegaCAM is a wide field camera housing a mosaic of 32 CCD detectors. For the optimal trade-off between dark current, sensitivity, and cosmetics, these detectors need to be operated at a temperature of about 155 K. The detectors mosaic with a total area of 630 cm2 directly facing the Dewar entrance window, is exposed to a considerable radiation heat load. This can only be achieved with a very performing cooling system. In addition this system has to be operated at the moving focal plane of a telescope. The paper describes the cooling system, which is build such that it makes the most efficient use of the cooling power of the liquid nitrogen. This is obtained by forcing the nitrogen through a series of well designed and strategically distributed heat exchangers. Results and performance of the system recorded during the laboratory system testing are reported as well. In addition to the cryogenic performance, the document reports also about the overall performance of the instrument including long term vacuum behavior.

Speaker: Mr Jean Louis Lizon a l'Allemand (European Southern Observatory)
• 32
Real performance and technical commissioning of an ultra-stable cooling system for a mid-range cryogenic astrophysical instrument

CARMENES is the new high-resolution high-stability spectrograph built for the 3.5m telescope at the Calar Alto Observatory (CAHA, Almería, Spain) by a consortium formed by German and Spanish institutions. This instrument is composed by two separated spectrographs, VIS channel (550-1050 nm) and NIR channel (900-1700 nm). The NIR-channel spectrograph's responsible has been the Instituto de Astrofísica de Andalucía, IAA-CSIC. This was installed at the telescope by the end of 2015, technical commissioning and final tuning of the instrument being extended up to fall 2016.
In that sense, one of the most challenging systems in the instrument involves the Cooling System of the NIR channel. It is a key system within the stability budget and was entirely in charge of the IAA-CSIC. That development has been possible thanks to a very fruitful collaboration with ESO (Jean-Louis Lizon). The present work describes the real performance of the CARMENES-NIR cooling system, mainly focusing on the extremely high thermal stability –in the order of few mK- around the working temperature (138K), as well as the main events and upgrades achieved during commissioning. As a result of such a performance, CARMENES-NIR is a cornerstone within the field of astrophysical instrumentation and, in particular, related to discovery of earth-like exoplanets.

Speaker: Mr Santiago Becerril-Jarque (IAA-CSIC (Instituto de Astrofísica de Andalucía))
• 33
Remote refilling of LN2 cryostat for high sensitivity Astronomical application

The most sensitive observation mode of the ESO VLT (Very Large Telescope) is the interferometric mode, where the 4 Units Telescope are directed to the same stellar object in order to operate as a gigantic interferometer. The beam is then re-combined in the main interferometry laboratory and fed into the analyzing Instrument. In order not to disturb the performance of the Interferometer, this room is considered as a sanctuary where one enters only in case of extreme need. A simple opening of the door would create air turbulences affecting the stability for hours. Any cold spot in the room might also cause convection which might change the Optical Path by fraction of micron.
Most of the instruments are operating at cryogenic temperatures using passive cooling based on LN2 bath cryostat. For this reason, dedicated strategy has been developed for the transfer of LN2 to the various instruments. The present document describes the various aspects and cares taken in order to guaranty the very high thermal and mechanical environmental stability.

Speaker: Mr Jean Louis Lizon a l"Allemand (European Southern Observatory)
• C1PoF - Superconducting Magnet Systems - Magnet Design Exhibit Hall AB

Exhibit Hall AB

Conveners: Luisa Chiesa (Tufts University) , Shrikant Pattalwar (STFC, Daresbury Laboratory)
• 34
Progress in development of PANDA solenoid magnet.

BINP presents the progress in the design of the 2T solenoid for the PANDA detector at FAIR. The paper describes the calculations of mechanical and thermal loads of the changed design of the solenoid.

Speaker: Evgenii Piata (Budker Institute of Nuclear Physics (RU))
• 35
The Progress on Cryogenic Calorimeter for Superconducting Undulators at SSRF

This cryogenic calorimeter is a cryo-free cryocooler system, focus on investigating beam-based heat load. The experimental results support the R&D of superconducting undulators and superconducting wigglers.
Online experiments at various beam conditions have been started since the cryogenic calorimeter installed in storage ring of Shanghai Synchrotron Radiation Facility (SSRF) at July, 2012. Due to the accomplishment of data acquisition of online experiments, the calorimeter was removed from storage ring at July, 2016.
This paper will describe the following contents:
1) Cryogenic design: some modifications and lessons of cryostat design of this calorimeter will be discussed.
2) Experimental data, analysis and conclusion: curve and result of heat load under various beam conditions will be demonstrated. Also, some suggestions for R&D of cryostat of superconducting undulators and wigglers will be discussed.

Speaker: Jian Cui (Shanghai Institute of Applied Physics, Chinese Academy of Sciences)
• 36
The Superconducting Dipole of SIS100: Technology Optimization for Series Production

The international Facility for Antiproton and Ion Research (FAIR) in Darmstadt, Germany, is a challenging accelerator project for fundamental research in various fields of modern physics. Superconducting dipoles are used to bend the particle beam in the SIS100 heavy-ion synchrotron, the main accelerator of FAIR. The 3 m long curved dipoles of super-ferric design are operated at cryogenic temperatures and allow for fast ramping with 4 T/s. To enable sufficient beam stability in the synchrotron the homogeneity of the magnetic field of $\Delta B/B\leq\pm 6\times 10^{-4}$ is required up to the maximal field of 1.9 T. The design shows an excellent quench behavior and comparatively low AC losses, revealed by an intense measurement program on the first of series (FoS) dipole performed at GSI. However, due to mechanical inaccuracies of the yoke production the FoS magnetic field was slightly distorted. Such corresponding issues were individually proven by advanced magnetic and geometrical measurement systems. Based on a broad survey, a second yoke was produced with significant adjustments of the fabrication process which yielded in a substantially improved mechanical accuracy and, to this end, to a sufficient field quality. Details of the characteristics of the optimized FoS dipole, and the production process with the associated measures of quality control in the series production are presented. First insights in the ongoing series production of the SIS100 dipoles will be given.

Speaker: Dr Christian Roux (GSI Helmholtzzentrum für Schwerionenforschung GmbH, Darmstadt, Germany)
• 37
Thermal Model of a Quench in Superconducting Undulators

Currently there are two 1.1 m long planar superconducting undulators (SCUs) in operation in the Advanced Photon Source storage ring. Their NbTi magnets are cooled with LHe penetrating through a channel in the magnet coil formers. In this scheme, the latent heat of LHe provides an effective energy buffer that allows the magnet to return to normal operation within minutes. An FEA based dynamic thermal model of the SCU is being developed to analyze the behavior of the SCU cryogenic systems during a quench. In this paper, preliminary results of these FEA based calculations and a comparison with current operation of SCUs are presented.

• Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357.
Speaker: Yuko Shiroyanagi (Argonne National Laboratory)
• C1PoG - Large Scale Refrigeration and Liquefaction I Exhibit Hall AB

Exhibit Hall AB

Conveners: Jennifer Marquardt (Ball) , Dr John Weisend (European Spallation Source ERIC)
• 38
Adaption of the LHC Cold Mass Cooling System to the requirements of the Future Circular Collider (FCC)

The cooling of the superconducting magnet cold masses with superfluid helium (HeII) is a well-established concept successfully in operation since years in the LHC. Consequently, its application for the cooling of FCC magnets is an obvious option. The 12-kW heat loads distributed over 10-km long sectors not only require an adaption of the magnet bayonet heat exchangers, but also present new challenges to the cryogenic plants, the distribution system and the controls strategy.

The paper recalls the basic LHC cooling concept with superfluid helium and define the main parameters for the adaption to the FCC requirements. Pressure drop and hydrostatic head is developed in the distribution and pumping systems; their impact on the magnet temperature profile and the corresponding cooling efficiency is presented and compared for different distribution and pumping schemes.

Speaker: Claudio Kotnig (Graz University of Technology)
• 39
Impact of large beam-induced heat loads on the transient operation of the beam screens and cryogenic plants of the Future Circular Collider (FCC)

The Future Circular Collider (FCC) under study at CERN will produce 50-TeV high-energy proton beams. The high-energy particle beams are bent by 16-T superconducting dipole magnets operating at 1.9 K and distributed over a circumference of 80 km. The circulating beams induce 5 MW of dynamic heat loads by several processes such as synchrotron radiation, resistive dissipation of beam image currents and electron clouds. This beam-induced heat loads will be intercepted by beam screens operating between 40 and 60 K and induce challenging transients during beam injection, energy ramp-up and beam ejection on the distributed beam-screen cooling loops, the sector cryogenic plants and the dedicated circulators.

Based on the current baseline parameters, numerical simulations of the fluid flow in the cryogenic distribution system during a beam operational cycle were performed. The effects of the thermal inertia of the headers on the helium flow temperature at the cryogenic plant inlet as well as the temperature gradient experienced by the beam screens has been assessed. Additionally, it enabled a thorough exergetic analysis of different cryogenic plant configurations and laid the building-block for establishing design specifications of cold or warm circulators.

Speaker: Laurent Tavian (European Organization for Nuclear Research)
• 40
LCLSII 2K Cold Box and Internal Piping System Mechanical Design & Analysis

Both LCLS II 2K cold boxes feature a large vacuum vessel topped by a 2” thick flat plate, buttressed by a central column, that supports six cold compressors and connected piping. Multiple external bayonet arrangements permit modification of the flow path through the box so the nominal flow can be adjusted approximately 24% without altering the internal piping. All piping and the vacuum vessel are designed to meet applicable ASME and ASCE codes for operating, transportation and seismic conditions. AutoPIPE CONNECT was used to perform the piping flexibility analysis and ANSYS 17.2 was used to analyze the vacuum vessel.

Speaker: Shirley Yang
• 41
PIP-II cryogenic system and the evolution of Superfluid Helium Cryogenic Plant specifications

Proton Improvement Plant – II (PIP-II) has been planned at Fermilab for providing powerful, high-intensity proton beams to the laboratory’s experiments. The heart of PIP-II is an 800 MeV Superconducting (SC) linear accelerator (Linac), which will provide 1.2 MW proton beam needed for the Long-Baseline Neutrino Facility (LBNF). The SC Linac accelerates the beam from 2.1 MeV to 0.8 GeV and includes five types of SC cavities to cover the entire velocity range required for acceleration of protons. These cavities are Half wave resonator (HWR), Single-spoke resonator (SSR1 and SSR2), Low Beta and High Beta Elliptic 5 – cell cavities (LB650 and HB650) [1]. The PIP-II cryogenic system consists of a Superfluid Helium Cryogenic Plant (SHCP) and the Cryogenic Distribution System (CDS) to the aforementioned SC cavities. The work described in the present article lists out the static and dynamic heat loads for each SC cavity along with the static heat load of the CDS. From the total computed heat load and pressure drop values in the CDS, the basic specifications for the SHCP, required for cooling the SC Linac, have evolved. The mitigation strategies for the heat load along with cryogen delivery to the cryomodules, are discussed in the article. Project specific requirements for the SHCP are also laid out.

Reference:

[1] The PIP-II Conceptual Design Report (Draft), V 1.00, November 29, 2016, available at: http://pxie.fnal.gov/PIP-II_CDR/PIP-II_CDR_v.0._work7.pdf

Speaker: Dr ANINDYA CHAKRAVARTY (Bhabha Atomic Research Centre, India; Fermilab, USA)
• 42
Preliminary Design of CIADS Cryogenic System

The Accelerator of CIADS (China Initiative Accelerator Driven System) will be built in the nearly future at IMP in china. All the superconducting cavities will be running at 2K . So a helium cryogenic system has been designed according to the requirements of the CIADS Accelerator. The total heat load of the cryogenic system is about 4.2kW at 2K, 2.1kW at 4.5K and 7.5kW at 60K . And the total 4.5K cooling power is 17.9kW. The paper focuses on the Preliminary design of flow diagram, estimating of heat load.

1. Requirements for cryogenic system of the CIADS accelerator
The running temperature of cryogenic system for CIADS is 2K, using base-cooled mode. The cooling down time between 300K-100K is required for 2K/h, 100K-4.5K for 5K/h. The running pressure in cryomodule is 30 mbara, the maximum pressure in cryomodule is 3 bar, and the requirement for liquid stability is between ±1%.

2. The heat load of the cryogenic system
The total heat loads contains heat load of cryomodules, valve boxes, transfer lines, vertical test and horizontal test. The cooling quantity is 4.2kW at 2K, 2.1kW at 4.5K and 7.5kW at 60K. So, the design 4.5K cooling capacity is 17.9kW. And two 10 kW/4.5K equipments is selected for CIADS cryogenic system.

Speakers: Dr Xiaofei Niu , Xiaohong Guo
• C1PoH - Purification Systems Exhibit Hall AB

Exhibit Hall AB

Conveners: Pascale Dauguet (Air Liquide Advanced Technologies) , Dr Luigi Serio (CERN)
• 43
Design and Performance testing of an External helium purifier for the cryogenic system at CHMFL

The helium cryogenic system at CHMFL is constructed to supply 4.5K forced flow supercritical helium for the hybrid magnet and produce liquid helium for other cryogenic experimental facilities. An external helium purifier is designed and manufactured to remove contaminants in the helium before fulfilled to the cryogenic system. The helium purifier with operating pressure of 2 MPa is capable of reducing contaminants content in helium from 2% to 5ppm. The purifier contains a dryer, a liquid nitrogen dewar, a tube heat exchanger, cylindrical activated carbon beds submerging in liquid nitrogen bath. Moisture and CO2 are removed by the dryer while O2 and N2 are absorbed by activated carbon. The design principles of the helium purifier contain low cost, low consumption of liquid nitrogen, fast regeneration and easy operation. In this paper, Details of the purifier design is presented, and such technical performance like working capacity, liquid nitrogen consumption, regeneration time and efficiency of the heat exchanger efficiency are tested.

Speaker: Mr Shuai Zhang (University of Science and Technology of China)
• 44
SNS Central Helium Liquefier Spare Carbon Bed Installation and Commissioning

The Spallation Neutron Source (SNS) Central Helium Liquefier (CHL) at Oak Ridge National Laboratory (ORNL) has been without major operations downtime since operations were started back in 2006. This system utilizes a vessel filled with activated carbon as the final major component to remove oil vapor from the compressed helium circuit prior to insertion into the system’s cryogenic cold box. Design calculation showing the expected lifetime of 10 years for this vessel will be presented. The fabrication, installation, and commissioning of a spare carbon vessel will be presented. The plans for connecting the new carbon vessel piping to the existing infrastructure will be discussed.

Speaker: Brian DeGraff (ORNL)
• C1PoJ - Hydrogen Systems Exhibit Hall AB

Exhibit Hall AB

Conveners: Mr Peter Bradley (NIST) , Jacob Leachman (Washington State University)
• 45
Annular air leaks in a liquid hydrogen storage tank

Large liquid hydrogen (LH2) storage tanks are vital infrastructure for NASA, the DOD, and industrial users. Over time, air may leak into the evacuated, perlite filled annular region of these tanks. Once inside, the extremely low temperatures will cause most of the air to freeze. If a significant mass of air is allowed to accumulate, severe damage can result from nominal draining operations. Collection of liquid air on the outer shell may chill it below its ductility range, resulting in fracture. Testing and analysis to quantify the thermal conductivity of perlite that has nitrogen frozen into its interstitial spaces and to determine the void fraction of frozen nitrogen within a perlite/frozen nitrogen mixture is presented. General equations to evaluate methods for removing frozen air, while avoiding fracture, are developed. A hypothetical leak is imposed on an existing tank geometry and a full analysis of that leak is detailed. This analysis includes a thermal model of the tank and a time-to-failure calculation. Approaches to safely remove the frozen air are analyzed, leading to the conclusion that the optimal approach is to allow the frozen air to melt and to use a water stream to prevent the outer shell from chilling.

Speaker: Angela Krenn (NASA)
• 46
Final Test Results for the Ground Operations Demonstration Unit for Liquid Hydrogen

Described herein is a comprehensive project—a large-scale test of an integrated refrigeration and storage system called the Ground Operations and Demonstration Unit for Liquid Hydrogen (GODU LH2), sponsored by the Advanced Exploration Systems Program and constructed at Kennedy Space Center. A commercial cryogenic refrigerator was interfaced with a 125,000 liter liquid hydrogen tank and auxiliary systems in a manner that enabled control of the state of the propellant by extracting heat via a closed loop Brayton cycle refrigerator coupled to a novel internal heat exchanger. Three primary objectives were demonstrating zero loss off storage and transfer, gaseous liquefaction, and propellant densification. Testing was performed at three different liquid hydrogen fill-levels. Data was collected on tank pressure, internal tank temperature profiles, mass flow in and out of the system, and refrigeration system performance. All test objectives were successfully achieved during approximately two years of testing. Detailed results are presented in this paper.

Speaker: Bill Notardonato (NASA Kennedy Space Center)
• 47
First experiment on liquid hydrogen transportation by ship inside Osaka bay

A project to import a large amount of liquid hydrogen (LH2) from Australia by a cargo carrier, which is equipped with two 1250 m3 tank, is proceeded in Japan. It is important to understand sloshing and boil-off characteristics inside the LH2 tank during marine transportation. However, the LH2 sloshing and boil-off characteristics on the sea has not yet been clarified. First experiment on the LH2 transportation of 20 liter vessel with superconducting MgB2 level sensors by the training ship “Fukaemaru”, which has 50 m long and 449 ton gross weight, was carried out successfully inside Osaka bay on February 2, 2017. In the experiment, synchronous measurements of liquid level, temperature, pressure and acceleration, also navigation and sea weather data were done. Experimental results of the LH2 sloshing and boil-off characteristics on the sea are discussed in comparison with those under static conditions.

This work was supported in part by a Grant-in Aid for Scientific Research, JSPS KAKENHI Grant Number 24246143, Japan.

Speaker: Prof. Minoru Takeda
• 48
The Cryogenic Moderator System for the European Spallation Source

The European Spallation Source in Lund, Sweden, is going to be a neutron scattering research center that aims to provide around 30 times brighter neutron beams than any other existing facility. As one subsystem of the target station the Cryogenic Moderator System (CMS) slows down high energy neutrons from the spallation process. To gain maximum neutron flux intensities along with high system availability for condensed and soft matter research, an optimized liquid hydrogen moderator circuit has been developed. Hydrogen with a pressure below critical, a temperature around 17 K, and a parahydrogen fraction of more than 0.995 will be utilized to interact with neutrons in a unique moderator vessel arrangement. A helium refrigerator, the Target Moderator Cryoplant (TMCP), continuously recools the hydrogen mass flow. The pressure stabilization is achieved by a cold buffer vessel in a side stream and different cooling demands are met by a controlled helium bypass around the main hydrogen-to-helium heat exchanger. The safety philosophy, interaction of components, and plans on how to validate functionality prior to hydrogen operation are described in detail.

Speaker: Mr Jakub Tkaczuk (Dresden University of Technology)
• 9:00 AM
Morning Break (9:00 - 10:00 a.m.) Cryo Expo, Exhibit Hall AB

Cryo Expo, Exhibit Hall AB

• M1OrA - Focused Symposia - Propulsion I: Overview, System Level Lecture Hall

Lecture Hall

Conveners: Timothy Haugan (U.S. Air Force Research Laboratory) , Kenichi Sato (Japan Science and Technology Agency)
• 49
[Invited] High Temperature Superconductors (HTS) in Electric Aircrafts – the baseline and the perspective

For Electric Aircrafts of passenger capacity of about 20 and above, there is a clear need to have a high power weight density drive train and energy conversion concept. Conventional concepts (often referred to as “non-cryogenic concepts” are clearly limited in this figure of merit [1] to about 20 kW/kg (for MW size motors). The use of cryogenic machines or superconducting concepts might double this figure.
In addition, high efficiency is a crucial aspect of rotating machineries in propulsion (for ships and aircrafts), and we will elaborate on how HTS technology is breaking some paradigms of conventional electro engineering [2,3,4,5,6].
In addition, changing from big fossil-driven turbines located on wings to electric propulsion motors will offer some additional aerodynamic benefits and might change future aircraft design considerably [1,3].
We will focus on and discuss the state of the art of selected existing HTS machines, the critical design path and components and some functional correlations.
We will highlight foreseeable progress and impact on performance and elaborate on aspects in integration and missing links/ white spots.
Finally we will point out the future prospects and developments which can be expected.

[1] Madavan, N. – “Hybrid-electric and distributed propulsion technologies for large commercial air transports – A NASA perspective”, IEEE energy conversion congress & exposition, Montreal, Canada, Sept.20-24, 2015
[2] Luongo et al. – “Next generation more-electric aircraft: a potential application for HTS superconductors”, IEEE Trans.Appl.Supercond. 19(2009)1055
[3] Masson et al. – “HTS machines as enabling technology for all-electric airborne vehicles”, Superconducting Science and Technology 20(2007)748
[4] de Almeida et al. – “Standards for efficiency of electric motors” IEEE Industry Applications Magazine Jan/Feb.2011
[5] DOE EERE call for next generation rotating machines: enabling technologies, DE-FOA-0001467, 09.Mar.2016
[6] Arndt,T. – “Superconductivity for Electric Aircraft”, talk on workshop on “Regional Electrical Aircraft”, 29th June to 1st July 2015, Airbus Defence and Space, Munich/Unterschleißheim, Airbus Group & European Council of Academies of Applied Sciences, Technologies and Engineering (Euro-CASE)
[7] IEEE roadmap on next generation of large electric machines (sponsored by Grainger CEME, NASA and IEEE) – in preparation

Speaker: Dr Tabea Arndt (Siemens AG)
• 50
[Invited] Development of Cryogenic/Superconducting Components for Aircraft Electric Propulsion

Megawatt (MW) class electric power systems will be needed in the next 5-10 year timeframe, not only for directed energy (DE) applications, but also for hybrid-electric or electric propulsion drivetrains for aerospace vehicles. There is question whether conventional technologies already established can meet this challenge with sufficient power densities and efficiencies, or whether alternate technologies might be needed such as cryogenic and/or superconducting. It is already established that Cu-wire technologies, as heavy as steel, are simply too heavy for some aerospace applications Superconducting/cryogenic power system components have intrinsic advantages for MW power systems, such as greatly size, weight and power (SWaP) requirements. In this paper, these unique properties and technical readiness assessment of different cryogenic and superconducting components will be reviewed, and compared to alternate traditional technologies such as Cu-wire based and semiconducting. The impact of these technologies will also be provided, for case-studies of hybrid-electric aircraft.

Speaker: Timothy Haugan (U.S. Air Force Research Laboratory)
• 51
Experimental investigation into the fault response of a superconducting hybrid electric propulsion electrical power system to a DC rail to rail fault

Hybrid electric propulsion aircraft are proposed to improve overall aircraft efficiency, enabling future rising demands for air travel to be met. The development of appropriate electrical power systems to provide thrust for the aircraft is a significant challenge due to the much higher required power generation capacity levels and complexity of the aero-electrical power systems (AEPS). The efficiency and weight of the AEPS is critical to ensure that the benefits of hybrid propulsion are not mitigated by the electrical power train. Hence it is proposed that for larger aircraft (300 pax) superconducting power systems are used to meet target power densities.
Central to the design of the hybrid propulsion AEPS is a robust and reliable electrical protection and fault management system. It is known from previous studies that the choice of protection system may have a significant impact on the overall efficiency of the AEPS [1]. Hence an informed design process which considers the key trades between choice of cable and protection requirements is needed. To date the fault response of a voltage source converter interfaced DC link rail to rail fault in a superconducting power system has only been investigated using simulation models validated by theoretical values from the literature.
This paper will present the experimentally obtained fault response for a variety of different layups of YBCO superconducting tape for a rail to rail DC fault. The paper will then use these as a platform to identify key trades between protection requirements, and cable design, providing guidelines to enable future informed decisions to optimise hybrid propulsion electrical power system and protection design.
1. C.E. Jones, P. J. Norman, S. J. Galloway, M. J. Armstrong, A.M. Bollman, “Comparison of candidate architectures for future distributed propulsion aircraft”, IEEE Transactions on Applied Superconductivity, Vol.26, Issue 6, 2016.

Speaker: Mr Steven Nolan (University of Strathclyde)
• M1OrB - HTS and MgB2 Bulk I Hall of Ideas - EH

Hall of Ideas - EH

Conveners: Dr John Durrell (University of Cambridge) , Michael Susner (U.S. Air Force Research Laboratory)
• 52
[Invited] A portable superconducting cryo-magnet with magnetic field of > 3 T generated by the pulsed field magnetization

A cryo-magnet system has been constructed using a single grain GdBa2Cu3O7-δ (GdBaCuO) bulk superconductor of diameter 30 mm. The bulk superconductor was cooled by conductive cooling, employing a portable Stirling cryo-cooler with a base temperature of 51 K. The superconducting cryo-magnet can be repeatedly charged by a pulsed field magnetization (PFM) system that is considerably compact.
A flux jump behaviour was observed consistently during magnetization when the applied pulsed field, Ba, exceeded a critical value (e.g. 3.78 T at 60 K). A sharp dBa/dt is essential to this phenomenon. This flux jump behaviour enables the magnetic flux to penetrate fully to the centre of the bulk superconductor, resulting in full magnetization of the sample without requiring an applied field as large as that predicted by the Bean model. We show that this flux jump behaviour can occur over a wide range of fields and temperatures, and that it can be exploited in our practical quasi-permanent magnet system.

Speaker: Difan Zhou (University of Cambridge)
• 53
Trapped field property of iron-pnictide bulk magnet

A trapped field of over 1 T at 5 K and 0.5 T at 20 K has been measured between a stack of magnetized cylinders of bulk polycrystalline Ba0.6K0.4Fe2As2 superconductors 10 mm in diameter and 18 mm in combined thickness. The trapped field showed a low magnetic creep rate (~3% after 24 hours at 5 K), while magneto-optical imaging revealed a trapped field distribution corresponding to uniform macroscopic current loops circulating through the sample. The superconductors were manufactured by hot isostatic pressing of pre-reacted powders using the scalable powder-in-tube technique. A high Vickers hardness of ~3.5 GPa and a reasonable fracture toughness of ~2.35 MPa m0.5 were measured. Given the untextured polycrystalline nature of the cylinders and their large irreversibility field (> 90 T), it is expected that larger bulks could trap fields in excess of 10 T.

1) J. Weiss, A. Yamamoto, A. Polyanskii, R. Richardson, D. Larbalestier, E. Hellstrom, Supercond. Sci. Technol. 28, 112001 1-6 (2015).

We would like to thank W. Starch and B. Hainsey for technical. The work at ASC was supported by NSF (No. DMR-1306785) and the facilities of NHMFL are supported by State of Florida and by NSF through a facility grant (No. DMR-1157490). The work at TUAT was supported by JST-PRESTO, JSPS and MEXT Elements Strategy Initiative to Form Core Research Center.

Speaker: Dr Akiyasu Yamamoto (Tokyo Institute of Technology)
• 54
Current distribution in field-cooled $YBa_2Cu_3O_7$ and $MgB_2$ disks as deduced from levitation force and trapped field measurements carried out in a large temperature range

A classical method used for determining $J_c$, the critical current density in superconducting cylinders consists in measuring the magnetic field along the superconductor axis after field cooling the sample. Supposing that the current generating the trapped field flows in the whole sample, the trapped field is proportional to $J_c$ and the obtained curve can be reproduced with the Chen et al. expression [Chen et al. Journal of Applied Physics 72, 1013 (1992)], using $J_c$ as a fitting parameter. However, confirming some numerical simulations, a combination of trapped field and levitation force measurements carried out at 77K has shown that the current flows in a restricted region of the cylinder with thickness t, that does not depend on the magnetization process of the superconductor [P.Bernstein et al. Supercond. Sci. Technol 29 075007 (2016)]. Here, we report levitation force and trapped field measurements carried out on both a $MgB_2$ and a $YBa_2Cu_3O_7$ cylinder in a large temperature range in order to investigate the dependence of t on temperature. The results show that t decreases as the temperature decreases. A consequence is that the trapped field can no longer be considered as proportional to $J_c$. This behaviour is due to the magnetic energy stored in the superconductor, that does not depend on its temperature. As a result, t behaves as $J_c^{-2/3}$, while the trapped field along the axis of the cylinder behaves as $J_c^{1/3}$ . These claims are substantiated by the experimental results obtained with both samples.

Speaker: Pierre Bernstein (Université de Caen-Normandie)
• 55
Large Diameter, Single Grain (RE)BCO Bulk Superconductors Fabricated by Infiltration and Growth

Large, single grain bulk (RE)BaCuO [(RE)BCO] superconductors have potential to generate magnetic fields that are much greater higher than those produced by conventional permanent magnets. The top seeded melt growth (TSMG) technique has been developed over the last 25 years to fabricate large, [(RE)BCO single grain samples that eliminate current limiting grain boundaries in the bulk microstructure. Although successful, there are a number of problems associated with the nature of the TSMG technique, including porosity, sample shrinkage and inhomogeneity in the distribution RE-211 content throughout the volume of sample, which leads to inefficient flux pinning. As a result, a new process based on top seeded infiltration and growth (TSIG) has been developed relatively recently as an alternative approach for the fabrication of large (RE)BCO single grains. The TSIG technique yields samples that are more dense, more uniform and have potentially better properties than those produced by TSMG. However, it is considerably more challenging to fabricate large-sized samples by this technique due to the relative complexity of the process. We describe the TSIG process and its application to a variety of (RE)BCO bulk superconductors and report the successful fabrication of single grains of up to 37.5 mm in diameter YBCO by a novel, 2-step TSIG process. This process enables a straightforward and very reliable growth process, which has clear practical implications for the manufacture of bulk samples for commercial applications. Details of the development and optimization of the microstructures and the superconducting properties of the (RE)BCO samples fabricated by this novel
technique are presented.

Speaker: David Cardwell (University of Cambridge)
• 56
Non-destructive investigation of hybrid of ferromagnet /(RE)BCO large grain bulks by flux extraction magnetometry and levitation force

This work deals with bulk, large grain superconductors used as permanent magnet for rotating machines or levitation applications. It has recently been shown that the magnetic properties of bulk large grain superconductors can be improved easily by attaching a short section of a soft ferromagnetic material (F) to one of the faces of the bulk superconductor (S), thereby producing a hybrid F/S structure [1]. Here we investigate the contactless determination of the magnetic behavior of such structures using a recently constructed bespoke magnetometer based on the flux extraction technique [2]. This device allows magnetic moments as large as 1 Am² to be measured at 77 K and accommodates large bulk samples up to 20 mm diameter. This extends significantly the accessible measurement range of “off-the shelf” magnetometers. Unlike techniques based on recording the distribution of flux at the surface of the sample, the measured signal is representative of the superconducting currents flowing across the entire volume of the sample. In the present work we examine the properties of permanently magnetized superconductors and hybrid structures, and measure the irreversible demagnetization of these structures when they are subjected to magnetic field cycles that are not parallel to their magnetization. We also investigate the levitation behavior of hybrid structures subjected to the non-uniform field of a permanent magnet or a combination of permanent magnets used as guideway for levitation applications, and compare the results to those obtained with a bulk superconductor alone.

References:
[1] Egan R. et al., Rev. Sci. Instrum. 86 (2015) 025107
[2] M. P. Philippe et al., Supercond. Sci. Technol. 28 (2015) 095008

Acknowledgments:
We greatly acknowledge Nippon Steel & Sumitomo Metal Corporation for providing bulk large grain GdBa2Cu3O7 (GdBCO) samples.

Speaker: Prof. Philippe Vanderbemden (University of Liege)
• C1OrA - JT & Reverse Brayton Coolers (Non-Aerospace) Madison Ballroom AD

Conveners: Marcel ter Brake (University of Twente) , Mark Zagarola (Creare LLC)
• 57
Test Results on TRL5 Vibration-free Sorption-based Cooler for 15 – 30 K

At the University of Twente, a vibration-free hydrogen-based sorption cooler is under development for cooling optical detectors in future scientific space missions. Depending on the operating pressures in the system, the cooler can be used can be used as stand-alone or as a precooling stage for a helium cooler establishing 4 K. In an earlier ESA project, a hydrogen-based sorption cooler was built and tested of which the compressor cells were at a radiator temperature of 87K. A second small radiator precools the high pressure gas to 51K. The gas is compressed in two stages: from 0.1 bar to 3 bar and from 3 to 50 bar by heating the sorber cells to 200K and 240K, respectively. In this compression phase the cells are isolated from the heat sink by gas-gap heat switches. The cold tip of the JT cold stage reached 14.5K and had a net cooling power of 35 mW. In the present paper we report on an ESA-CTP (Core Technology Programme) project that aims to increase the TRL level of 4 to 5, which is carried out in cooperation with Airbus DS. The redesign of the compressor cell and the check valves will be discussed. The cell and check valves were subjected to relatively high shaker-vibration loads (45 g random). Prior to and after the shaking, the performance of the compressor cell and of the check valves is measured. Test results and further development will be discussed.

Speaker: Marcel ter Brake (University of Twente, The Netherlands)
• 58
Study of reverse Brayton cryocooler with helium-neon mixture for HTS cable

As observed in the earlier studies, helium is more efficient than neon as a refrigerant in a reverse Brayton cryocooler (RBC) from the thermodynamic point of view. However, the lower molecular weight of helium leads to higher refrigerant inventory as compared to neon. Thus helium is suitable to realize the high thermodynamic efficiency of RBC whereas neon is suitable for the compactness of the RBC. A binary mixture of helium and neon can be used to achieve high thermodynamic efficiency in the compact reverse Brayton cycle (RBC) based cryocooler. In this paper, an attempt has been made to analyze the thermodynamic performance of the RBC with a binary mixture of helium and neon as the working fluid to provide 1 kW cooling load for HTS power cables working with a temperature range of 50 K to 70 K. The basic RBC is simulated using Aspen HYSYS V8.6®, a commercial process simulator. Sizing of each component based on the optimized process parameter for each refrigerant is performed based on computer code developed using Engineering Equation Solver (EES-V9.1). The recommendation is provided for the optimum mixture composition of the refrigerant based on the trade-off factors like thermodynamic efficiency such as the figure of merit and exergy efficiency, equipment considerations, and inventory management. The outcome of this study may be useful for recommending a suitable refrigerant for the RBC operating at a temperature level of 50 K to 70 K.

Speaker: Mr Aman Kumar Dhillon (Indian Institute of Technology Kharagpur)
• 59
Performance of an ejector for application in a nitrogen JT cycle: experimental and numerical analysis

The performance of a Joule Thomson (JT) cryocooler can be improved by introducing an ejector into the JT cooling cycle. The function of the ejector is to lift the pressure of the gas leaving the evaporator to a higher level, thus reducing the cold-end temperature and/or the input power of the compressor. In this paper, the performance of an ejector operating with nitrogen gas is investigated experimentally and numerically. The effects of geometry and operating parameters on the ejector performance are analyzed. The validity of the numerical model is verified by comparison between the predicted and measured overall ejector performance. Meanwhile, the local flow features of the ejector are visualized through numerical modelling.

Speaker: Marcel ter Brake (University of Twente)
• 60
Intrinsic limitation on the cooling power of the JT cryocoolers

Several precooled JT cryocoolers (JTC) working at 4 K have been developed for space missions. Although these cryocoolers are qualified with high reliability and long life time, their efficiencies are relatively low which is worth further research.
A JT cryocooler has an intrinsic limitation on its cooling power. The intrinsic limitation is that the JTC will be warmed up continuously when the heat load exceeds a certain maximum, which is defined as the maximum specific cooling power (MSCP). The MSCP is equal to the isothermal enthalpy difference at the warm end of the recuperator determined by the high pressure and precooling temperature. The mechanism and the JTC behavior related to the intrinsic limitation will be illustrated with systematic theoretical analysis.
When the MSCP is achieved by a helium-4 JTC, the cooling temperature may be already higher than the critical point. So the maximum specific cooling power at 4 K (MSCP4) should be defined for cooling-performance optimization. The discussion on the MSCP4 explains why the JTC would have optimal high pressures not the same as those give the MSCPs.
Furthermore, the theoretical analysis will be applied to explain a real case based on the acquired experimental data.

Speaker: Mr Dongli Liu (Zhejiang University)
• C1OrB - Expanders II Hall of Ideas - GJ

Hall of Ideas - GJ

Conveners: Lars Blum (Linde Kryotechnik AG) , Dr Venkatarao Ganni (FRIB/MSU)
• 61
Development and Performance Evaluation of High Speed Cryogenic Turboexpanders at BARC, India

Turboexpander is a key focus area for Bhabha Atomic Research Centre (BARC), Mumbai, India in the program for development of helium refrigerators and liquefiers for intra departmental requirements. To start with, a turbine impeller with major diameter 16 mm and design speed of 264,000 RPM, suited for use in the 1st stage of a modified Claude cycle/ reverse Brayton cycle based standard helium liquefier/refrigerator, was developed. The turboexpander rotor was subjected to extensive testing in laboratory followed up with field trials mounted in a helium refrigerator unit developed by BARC. Isentropic efficiency exhibited by the turbine stage was computed to be about 63%. Later on, a second series of turboexpander with the same major diameter (16 mm) and design speed of 260,000 RPM was developed with “splitter” blades at the major diameter end. Yet another turboexpander series, size 16.5 mm and design speed 168,000 RPM, was also developed suited for use in the 2nd stage of a standard helium liquefier/refrigerator. The 1st stage “splitter” bladed turbine along with the 2nd stage turbine units were mounted onto a helium liquefier developed by BARC. During extensive field trials, the helium liquefier exhibited a maximum liquefaction capacity of about 32 l/hr and 195W refrigeration. The 1st and 2nd stage turbine maximum isentropic efficiencies were computed to be in excess of 72% and 67% respectively. High strength aluminium alloy was chosen as the material of construction for the turbine and brake wheel impellers to increase the maximum permissible rotor speed. The present article describes these development efforts at BARC, including results obtained during field trials with the developed helium refrigerator and liquefier.

Speaker: Dr ANINDYA CHAKRAVARTY (Bhabha Atomic Research Centre, India; Fermilab, USA)
• 62
ALAT latest magnetic bearings turbomachines commissioning

Strong of 60 years of innovation and design in the field of cryogenic turbomachines, Air Liquide Advanced Technologies is constantly developing new products. Magnetic bearings technology is used since the mid 80’s for specific applications where reliability and efficiency is a key issue. 50 cold compressors, 5 pumps and 5 high power turbomachines (moto-compressors, moto-turbo-compressors and turboalternators) have been delivered in the past years and 29 magnetic bearings turbomachines will be delivered by ALAT in 2017. The first supercritical helium pump of Air Liquide new standard range of cryomachine was commissioned successfully in 2016 for the JT60 project. The compression map of the pump was measured and in very good accordance with the calculations. A new 175kW turbomachine installed on Turbo-Brayton refrigeration system has been commissioned and characterized in 2016. The compression map of the centrifugal compressors and the efficiency of the turbine have been measured. This paper presents the commissioning results of these 2 new turbomachines on magnetic bearings.

Speaker: Cecile Gondrand (Air Liquide Advanced Technologies)
• 63
Superconducting Bearings for a LHe Transfer Pump

Superconducting bearings are used in a number of applications for high speed, low loss suspension. Most of these applications have a warm shaft and require continuous cooling, which leads to additional power consumption.
Therefore, it seems advantageous to use these bearings in systems that are inherently cold. One respective application is a submerged pump for the transfer of liquid helium into mobile dewars. Centrifugal pumps require tight sealing clearances, especially for low viscosity fluids and small sizes. This paper covers the design and qualification of the superconducting YBCO bearings for a laboratory sized liquid helium transfer pump.

Speaker: Thomas Funke (Technische Universitaet Dresden)
• 64
Use of ionic liquids in helium applications

Oil contamination is a re-occurring issue in cryogenic helium applications resulting in reduced performance and eventually the need for thorough cleaning of the coldbox internals. Main sources are the oil-injected recycle gas screw compressors. Although the systems are equipped with oil removal systems, mal-operation, improper design, and particularly the carry-over of the residual content of a few ppb will result in accumulation of oil in the coldbox over a longer period of operation. In cooperation with Kaeser, Linde Kryotechnik has modified helium screw compressors for operation with ionic liquids. Ionic liquids exhibit similar tribological properties as for example Breox oil, but are characterized by negligible vapour pressures.

The presentation will show the consequences on liquid carry-over into the coldbox, on equipment sizing of coalescers and adsorbers, as well as on efficiency and power consumption.

Speaker: Mr Klaus Ohlig (Linde Kryotechnik AG)
• 65
The Helium Turbines Design and Testing of 500W@4.5 K Cryogenic System

The indigenous design and development of helium turbines of 500 W/4.5 K cryogenic system have been started at ASIPP, China. This paper briefly discuses the design process and the fabrication drawings for the whole helium turbine system, which includes the turbine wheel, nozzle, diffuser, shaft, brake compressor, two types of bearing, appropriate housing and some other necessary parts. With the design process, it is possible to design a new turbine for any other fluid cryogenic system , since the fluid properties are properly taken care of in the relevant equations of the design procedure.
Key words：helium turbines，500 W/4.5 K Helium refrigerator, Turbine Design,Testing.

Speaker: Dr XiaoFei Lu (Institute of Plasma Physics,Chinese Academy of Sciences)
• C1OrC - Medical Systems Madison Ballroom BC

Conveners: Kathleen Amm (GE Global Research) , Patrick Kelley (TechSource, Inc.)
• 66
Conceptual design of a cryogen-free μ-MRI device

To perform Micro Magnetic Resonance Imaging (μ-MRI) analysis on small regions such as skins, articulations or on small animals, the required spatial resolution imply to dramatically improve the sensitivity of the detection. One way to go is to use miniature radio-frequency superconducting coils that allow, among others, increasing significantly the signal-to-noise ratio. The RF probes, constituted of optimized YBaCuO film coils cooled below nitrogen temperature, must be located no further than few millimeters from the biological region to be imaged in a clinical 1.5 T MRI magnet. To fulfill the medical environment and constraints, a cryogen-free cooling scheme has been imagined to maintain the superconducting coils at the working temperature. The cryogenic design is based on a pulse tube cryocooler and a solid thermal link inserted in a non-magnetic cryostat to avoid creating any electromagnetic perturbations to the MRI magnet. We report here the conceptual design of the cryogenic system with the required thermal performances, the corresponding layout and architecture of the system as well as the main technical challenges which have to be met for the construction.

Speaker: Bertrand Baudouy (CEA Saclay)
• 67
A new passive system for contamination-free long-distance cryo-transfer of biological tissues

Over the past decades cryopreservation and cryo-imaging techniques have been intensively developed for structural and functional studies of biological samples at the sub-cellular level. To achieve this, ultra-high resolution imaging techniques such as cryo fluorescence microscopy, cryo electron microscopy, or cryo mass spectrometry are employed. Often these methods make use of commercially available vitrified sample transfer systems. But nearly all these transfer systems are built for a specific cryo-imaging or –analysis instrument and cannot be used for correlation studies. The aim of the present project is to develop a more generally applicable, light-weight system for transferring vitrified samples among imaging modalities, even over significant (i.e. 200 km) distances.
Our cryogenic transfer system consists of three building blocks: a storage chamber, adaptation flanges that allow the connection to different imaging modalities, and a mobile liquid N2 refilling unit. The storage chamber is furthermore equipped with a laser-welded vacuum-isolated low consumption liquid nitrogen cryostat and an innovative thermally shielded cryo-sample stage. This system produces a high vacuum environment, optimized transfer temperature, as well as both horizontal and vertical sample exchange possibilities between high-resolution cryo-imaging instruments. A liquid N2 level monitoring system, powered by a single 3V cell battery, is developed to ensure the cryogenic transfer conditions for vitrified samples over long distances. The complete transfer system has a weight of ~ 5.3 kg and maintains stable cryo-conditions at the sample stage for 2 hours. With the mobile liquid N2 refilling unit, this transportation system can extent stable cryo-conditions that permit transport over long distances of hundreds of kilometers.
In summary, our system allows contamination-free sample transportation between different imaging modalities without active components, e.g. vacuum pumps, cryo-coolers, and other power-requiring systems. Because of its flexible configurability it can come to play a vital role in cryobiology imaging and research.

Speaker: Dr Tian Cheng (Laboratory for Biological Geochemistry, Institute of Environmental Engineering, Ecole Polytechnique Fédérale de Lausanne)
• 68
Effect of Surface Condition to Temperature Distribution in Living Tissue during Cryopreservation

The temperature distribution of the simulated living tissue is measured for the improvement of the cooling rate during cryopreservation when the surface condition of the test sample is changed. Agar with the 1.5 wt% is used as a simulated living tissue. The test sample is the cylindrical shape and the size is ϕ8.2 x 45 mm. The inside of the test sample is filled with agar. The surface of the test sample is covered with the stainless steel mesh. The variation of the transient temperature with the specification of the mesh by the directly immersion in the liquid nitrogen is measured. The temperatures on the sample surface and the inside of the sample are measured by use of type T thermo couples. It is confirmed that on the sample surface there is the slightly temperature increase than that in the saturated liquid nitrogen at the atmospheric pressure. It is found by the comparison of the degree of superheat with or without the mesh that the surface temperature of the test sample with the mesh is lower than that without the mesh. On the other hand, the time series variations of the inside temperature located in the center of the sample does not change with or without the mesh. It is considered that the center of the sample used in the present study is too deep from the surface to respond to the boiling state on the sample surface.

Speaker: Dr Masakazu NOZAWA (National Institute of Technology, Akita College)
• 69
Safety Aspects of Whole-Body Cryochamber and Cryosauna Operation

Interest in low temperature treatment is constantly increasing. Whole-body cryotherapy (WBC) devices are becoming available not only in medical centers but also in local gyms and spa centers. A new group of users are professional sport clubs where 3-minutes session of whole-body cryotherapy is post-training procedure to improve and speed up the recovery process.

Currently, there are four types of WBC devices available on the market and offered to commercial (non-medical) users. European and American market is dominated by two of them: classic cryochambers and cryosaunas, respectively. Both constructions are supplied with liquid nitrogen. Low temperature inside classic cryochamber is produced by evaporating of liquid nitrogen in two or more heat exchangers. There is never a direct contact between user and cryogenic medium in any of system operation mode. Therefore, supply system is categorized as closed one. Cryosauna is cooled down by filling with cold vapor of liquid nitrogen. Supply system is considered open because it allows for direct contact between user and cryogenic gas. Open supply system of cryosauna is primary and most questionable issue of its operational safety, particularly after tragic accident in October 2015.
This paper presents the comparative analysis of classic cryochamber and cryosauna from safety point of view. Both devices have been analyzes and tested on existing systems in operation. Paper gives detailed analysis of constructions, supply systems and working parameters. Special attention has been focused on problem of oxygen deficiency hazard. Different failure or accident scenarios have been analyzed and discussed.

Speaker: Dr Agnieszka Piotrowska (Wroclaw University of Science and Technology)
• 70
A tissue snap-freezing apparatus without sacrificial cryogens

Molecular technologies in cancer diagnosis require fresh and frozen tissue, which is obtained by means of snap-freezing. Currently, coolants such as solid carbon dioxide or liquid nitrogen are used to preserve good morphology of the tissue and to keep the molecular activity intact. Using these coolants, snap freezing of tissues for diagnostic and research purposes is often time consuming, laborious, even hazardous and not user friendly. For that reason snap-freezing is not routinely applied at the location of biopsy acquisition. Furthermore, the influence of optimal cooling rate and cold sink temperature on the viability of cells is not well known. In this paper, a snap-freezing apparatus powered by a small cryocooler, is presented that will allow bio-medical research of tissue freezing methods and is safe to use in a hospital. To benchmark this apparatus, the cool down of an aluminium cryo-vial in liquid nitrogen is measured, which has a cooling rate of -25 K/s. A forced convective helium gas flow through a gap around the cryo-vial obtained sufficient cooling rates and is chosen as the preferred cooling method. A conceptual design of the snap-apparatus with forced flow is discussed.

Speaker: Srinivas Vanapalli (University of Twente)
• 71
Efficient biostorage below -150 degrees C without sacrificial cryogen

Cold storage of biological specimens generally falls into two categories: (1) "Ultra-low" mechanical freezers, which are technologically close cousins of domestic vapor-compression freezers, and (2) liquid-cryogen-cooled dewars. The first type are expensive to run, and give off a lot of waste heat which must in turn be removed from a laboratory or work area, and can only reach moderately cold temperatures (-86 C, typically), well above the 'glass transition temperature'. The second type enable very cold storage, and don't consume electricity or waste heat--but they consume sacrificial cryogenic liquid which must continually be replenished. This is not economical or convenient without bulk cryogen storage and permanent VJ piping to automatically refill the freezers, which is not practical for many locations. Recently, Chart Inc. has combined its expertise in storage dewars with its efficient Q-Drive cryocoolers to produce efficient biofreezers that require no sacrificial cryogen. Using a dewar instead of a standard refrigerator box for the storage space reduces the heat leak to only a few watts, which can easily be overcome by a cryocooler mounted on the top of the dewar. The first such product from Chart, the "Fusion" freezer, uses an internal 50-liter cryogen tank to provide both heat exchange surface for cooling the storage space and also 'hold time' in case of a power outage. The cryocooler is mounted directly to this internal tank, and reliquifies the cryogen as it boils off. The 1500-liter storage space is maintained below -160 C for an average power draw of 320 watts. The cost of the system is expected to be comparable to existing -86 C freezers.

Speaker: Philip Spoor (Chart Industries)
• M1OrC - Focused Symposia - Propulsion II: Power Electronics Lecture Hall

Lecture Hall

Conveners: Dr Charles Rong (U.S. Army Research Laboratory) , Sonja Schlachter (Karlsruhe Institute of Technology, ITEP)
• 72
[Invited] Cryogenic Power Electronics for Superconducting Power Systems

Fully superconducting power systems in electric aircraft and all-electric ships will have many power conversion and conditioning stages between the generators, transmission cables, storage devices, and loads such as motors. The system level efficiency suffers from heat leak from ambient if the power has to leave the cryogenic environment of a superconducting device for power conversion and conditioning before entering a second superconducting device. A substantial share of the total heat leak is located at the interfaces between cryogenic devices and room temperature devices. It is, therefore, an important goal to minimize the number of non-cryogenic power devices and cryogenic to normal interfaces.

To increase the system-level efficiency, simpler designs, and to increase reliability, power electronic converters operating at cryogenic temperatures are needed. Besides minimizing the heat loads at the interfaces, cryogenic power electronics can offer other benefits such as higher power density and simpler integration of various devices. However, there are several obstacles to overcome before cryogenic power electronics technology reach maturity. While semiconductors and small power electronic devices have been studied at cryogenic temperatures and certain topologies have been identified as promising candidates for cryogenic power electronics, their packaging, interconnects, dielectric aspects, and cooling protocols are still areas of active and much needed research. The topology of the converter has to take into account the limitations and the efficiencies associated with the individual components at cryogenic temperatures. One example is the matrix converter topology, which does not require a DC link capacitor and therefore limits the risk with respect to the need for large cryogenic capacitors.

This paper presents the opportunities and challenges of cryogenic power electronic systems and the results of our attempts in developing suitable topologies and address system and device level issues related to cryogenic thermal and dielectric aspects.

Speaker: Lukas Graber (Georgia Institute of Technology)
• 73
[Invited] Future Cryogenic Switchgear Technologies for Superconducting Power Systems

Advanced superconducting generators, cables and fault current limiters have allowed highly-integrated power distribution systems to become more compact and efficient. For the purpose of constructing parallel, multi-terminal cryogenic power systems, switching devices are required to offer protection and control. However, conventional switchgear which connects superconducting components to ambient temperature may lead to substantial heat leak. This heat leak could be significantly reduced if switchgear is designed to operate at cryogenic temperature. This paper evaluates the three conventional switchgear technologies: oil circuit breakers, SF6 circuit breakers and vacuum interrupters with respect to their potential for cryogenic implementations. Their cryogenic counterparts would require substantial changes in both dielectric media and structural design. Cryogenic liquids such as liquid nitrogen (LN2), liquid methane (LCH4), liquid natural gas (LNG), and liquid hydrogen (LH2) are promising candidate fluids for classical oil circuit breakers. We compare dielectric, thermal, and arc quenching properties of cryogenic liquids with those of oil circuit breakers. Similarly, a number of cryogenic gases are compared with SF6 gas concerning their performances. The challenges for cryogenic vacuum interrupters are material compatibility and fatigue. Besides dielectric media, structural designs of cryogenic circuit breakers also need special modifications to include thermal interface between cryogenic switching chamber and control devices in ambient temperature.

Speaker: Ms Chunmeng Xu (Georgia Institute of Technology)
• 74
[Invited] An AC Homopolar HTS Generator for Flywheel Energy Storage

High speed, compact, lightweight and highly efficient motors and generators are needed for applications in power and transport systems. Here we discuss one application in an energy storage system for subway station regenerative braking energy storage. In this application high rotational speed (> 25,000 RPM) and rapid two-way high power transfer (> 500 kW) within a small footprint are key performance requirements
An AC Homopolar synchronous machine is an ideal choice for such applications. These machines employ a conventional high speed AC armature winding but utilise a stationary DC excitation winding on the stator that simplifies a design for high rotational speed. The rotor is also simplified to a ferromagnetic solid rotor, with the speed only constrained by the mechanical stress limit of the rotor material. Homopolar machines have been demonstrated that can deliver electrical frequencies in multiple kHz and rotational speeds past 60,000 RPM, but delivering power levels past 10’s of kW has been challenging at high electrical frequencies due to significant cooling losses for the DC field coils. Modern HTS materials are ideal candidates to provide low-volume, high JE, high field DC coils to meet this challenge; replacing the DC field excitation coil with a suitable superconducting coil will lead to MegaWatt class machines.
We describe the design of a homopolar machine with a high temperature superconducting DC excitation coil, an integrated novel brushless flux pump exciter, and analyse the performance for application as a flywheel energy storage unit. The brushless exciter fundamentally reduces the thermal load upon the cryogenic system by removing the need for thermally inefficient normal-conducting current leads and the impact on cryogenic overhead is discussed.

Speaker: Dr Rod Badcock (Victoria University of Wellington)
• M1OrD - Focused Session: Superconducting Thin Films for SRF and Magnets Applications Hall of Ideas - EH

Hall of Ideas - EH

Conveners: Emanuela Barzi (FNAL) , Lance Cooley (FNAL)
• 75
[Invited] Superconducting thin films and multilayers for particle accelerators

Recent advances in the Nb technology have resulted in the development of superconducting radio-frequency (SRF) resonant cavities capable of producing accelerating fields up to 50 MV/m and achieving very high quality factors exceeding 1010 @ 1-2 GHz and 2K. At such strong RF fields, the density of screening currents flowing at the inner surface of the Nb cavities approaches the fundamental depairing limit, so any further increase of accelerating gradients requires materials with thermodynamic critical fields and superconducting transition temperatures higher than those of Nb. In this talk I will give an overview of basic physics and materials mechanisms which limit the performance of SRF cavities and discuss new opportunities to increase the accelerating gradients by surface nanostructuring using Nb3Sn, NbN, MgB2 or iron-based superconductors in the form of thin films and multilayers deposited on the inner surface of the Nb cavities.

Speaker: Prof. Aleksander Gurevich (Department of Physics, Old Dominion University)
• 76
Characterizing thin films by RF and DC methods

Several particle accelerators like the LHC at CERN use superconducting cavities to increase the energy of charged particles produced by sputter coating a thin niobium film on a copper substrate. Coating technologies used are diode and DC magnetron sputtering (dcMS). Compared to the bulk niobium technology the performance of such thin film cavities is limited by the field dependent RF residual surface resistance. The current application space is therefore usually at relative low frequency (up to 400 MHz), high temperature (4.2 K) and moderate accelerating gradient (a few MV/m). Several new techniques are currently being developed to overcome this limitation. The HiPIMS technology is very similar to dcMS. Films have been deposited and tested on 1.3 GHz test cavities. Other coating techniques like electron cyclotron resonance (ECR) are not yet developed to be deposited on cavities. Here sample tests can give invaluable information on the RF performance. A suitable device which can measure the surface resistance with unpreceded accuracy is the Quadrupole Resonator from CERN, which has more recently been rebuilt and further developed at HZB. Additionally DC methods can be used to probe the superconducting properties of samples and guide the development of the coating process. Two techniques which have been proven to be very informative for SRF developments are muon spin rotation and point contact tunneling. This article reviews RF and DC methods and results on test cavities and samples for SRF application.

Speaker: Anne-Marie Valente-Feliciano (Jefferson Lab)
• 77
MgB2 thin films for SRF cavity applications

MgB2 thin films grown by hybrid physical-chemical vapor deposition (HPCVD) have been investigated for SRF cavity applications. Clean MgB2 thin films have a low residual resistivity (<0.1 µΩcm) and a high Tc of 40 K, promising a low BCS surface resistance. Its thermodynamic critical field Hc is higher than Nb, potentially leading to a higher maximum accelerating filed. The lower critical field Hc1, which marks the vortex penetration into the superconductor and the vortex motion related dissipation, is lower for MgB2 than Nb, but it can be enhanced by decreasing the film thickness. I will present results on the enhancement of Hc1 in thin MgB2 films and coatings, deposition of MgB2 films on Cu, and the coating of RF cavities by MgB2. These results are encouraging for the application of MgB2 for SRF cavities.

Speaker: Prof. Xiaoxing Xi (Temple University)
• 78
Improvement of Nb Thin FIlm MIcrostructure by HiPIMS

Bulk Niobium (Nb) SRF (superconducting radio frequency) cavities are currently the preferred method for acceleration of charged particles at accelerator facilities around the world. However, bulk Nb cavities suffer from variable RF performance, have high cost and impose material & design restrictions on other components of a particle accelerator. Since SRF phenomena occurs at surfaces within a shallow depth of <1 m, a proposed solution to this problem has been to deposit a superconducting Nb thin film on the interior of a cavity made of a suitable alternative material such as copper or aluminum. While this approach has been attempted in the past using DC magnetron sputtering (DCMS), such cavities have never performed at the bulk Nb level. However, new energetic condensation techniques for film deposition offer the opportunity to create suitably thick Nb films with improved density, microstructure and adhesion compared to traditional DCMS. One such technique that has been developed somewhat recently is High Power Impulse Magnetron Sputtering (HiPIMS). In order to test HiPIMS, a systematic study was performed in which Nb films were deposited on coupon samples in multiple “series” where only one parameter (Ion Fraction, Average Condensation Energy, Temperature, Pressure…etc.) is varied at a time. Subsequently, the sample properties were measured using: XRD, AFM, SEM, EBSD and TEM, and correlations were made between deposition parameters and film properties. Here we present the results from the systematic studies performed and show the evolution of the Nb thin film properties as a function of the deposition parameters used across the HiPIMS regime.

Speaker: Mr Matthew Burton (The College of William & Mary)
• 79
Innovative thin film technologies for nano-engineering and optimizing Nb3Sn superconductor beyond state-of-the-art

A novel patented electro-chemical technique to produce Nb3Sn thin films was reproduced in US labs. The Nb3Sn phase is obtained in a two-electrode cell, by electrodeposition from aqueous solutions of Sn layers and Cu intermediate layers onto Nb substrates. Current densities are between 20 mA/cm2 and 50 mA/cm2, and bath temperature is between 40C and 50C. Subsequent thermal treatments in inert atmosphere are realized at 700C to obtain the Nb3Sn superconducting phase, which is typically between 5 and 10 m in thickness. Nb3Sn benchmark samples were first produced at ANL. Then the technique was further optimized, and samples were characterized for superconducting properties, including Tc0 by transport and inductive measurements, using the existing FNAL infrastructure. The samples critical temperature Tc0 ranged from 17.0 K and 17.7 K, and the samples upper critical field Bc20 ranged between 22 T and 24 T. Flux pinning models in granular A-15 based on Josephson-coupled arrays and anisotropic flux pinning by grain boundaries predict that the Jc of A-15 superconductors could be largely improved by elongating their grain structure and/or nano-engineering the materials. In a next phase of this work, these thin films will be used to test theoretical predictions, as well as flux pinning properties of additional elements inexpensively and with fast turnaround.
Since the electrochemical deposition method is scalable in size and controllable on curved surfaces, applications to superconducting magnetic shields and SRF are in principle possible. In parallel to sample development and fabrication, some R&D effort was put in the electro-polishing of the samples’ outer surface at JLab for future surface resistance measurements, to test adequacy to SRF applications.

Speaker: Michela Sainato (UID)
• 80
Development of NbTiN based multi-layered structures for SRF applications

Theoretical interest has stimulated efforts to grow and characterize thin multi-layer superconductor/insulator/superconductor (SIS) structures for their potential capability of supporting otherwise inaccessible surface magnetic fields in SRF cavities. The technological challenges include realization of high quality superconductors with sharp, clean, transition to high quality dielectric materials and back to superconductor, with careful thickness control of each layer. Choosing NbTiN as the first candidate material, we have developed the tools and techniques that produce such SIS film structures and have begun their characterization. Using DC magnetron sputtering and HiPIMS (high power impulse magnetron sputtering), NbTiN and AlN can be deposited with nominal superconducting and dielectric parameters. Hc1 flux penetration field enhancement is observed for NbTiN layers with a Tc of 16.9 K for a thickness less than 150 nm. The optimization of the thickness of each type of layers to reach optimum SRF performance is underway. This talk describes this work and the rf performance characteristics observed to date.

Speaker: Anne-Marie Valente-Feliciano (Jefferson Lab)
• 12:00 PM
University of Wisconsin Lab Tour (12:00 - 2:15 p.m.; **at capacity**)
• 12:30 PM
Lunch (on your own, 12:30 - 2:00 p.m.)
• C1PoK - Instrumentation, Visualization, and Controls I Exhibit Hall AB

Exhibit Hall AB

Conveners: Austin Capers (Scientific Instruments) , Scott Courts (Lake Shore Cryotronics, Inc.)
• 81
A new cryogenic temperature measurement solution suitable for large installation and laboratory use.

The low temperature measurement station called CABTR (Centrale d’Acquisition Basses Températures Rapide) is an instrumentation, recently developed by CEA, and dedicated to the cryogenic temperature measurement.
Thanks to its data rate acquisition up to 1 kHz/channel and its lock-in measurement to be lowly sensitive to the industrial harsh environment, the CABTR permits to observe fast temperature transients, such as temperature oscillations due to pulse tube cryo-coolers..
Its bandwidth (max 100Hz) can be reduce to increase the accuracy and the distance between the sensor and the station. As an example, this paper will present 4K measurement results with a 300m long thermometric chain.
We also described all means of communication available to integrate easily the CABTR into your installation equipped for example with PLC. Different housings are available and will be described from 8 channels in lab box type to 40 channels in 19inch rack for cubicle mounting (8U).

Speaker: Mr Anthony ATTARD (CEA)
• 82
Behaviour of ITER flowmeters under operating conditions: simulation and experimentation

CEA/SBT has to deliver 277 flowmeters for the control of the ITER superconducting magnets. Some of the flowmeters will operate at room temperature while the remaining ones will operate at cryogenic temperature (5 bar and 5 K, typically). Within the framework of this contract, CEA/SBT has to measure the flow coefficient of the flowmeters that takes into account the fact that the fluid is not completely incompressible and that the pressure drops are not equal to zero. As the use of supercritical helium involves very high Reynolds number, this coefficient was chosen to be measured in the Helios loop coupled to the 400 W @ 1.8 K refrigerator available at CEA/SBT. Since all the refrigerator cooling capacity is absorbed by the cold circulator while characterizing the largest flowmeters, an optimisation of the loop was required in order not to add any electrical heater even if the operating temperature of the loop has to be higher than the temperature of the helium bath of the refrigerator. This optimization allows the whole cooling capacity to be dedicated to the circulating pump in order to maximize the mass flow rate in the flowmeters. The design of the loop was carried out with an EXCEL model resulting from a thorough work. In a second time, a model made with the Simcryogenics library for MATLAB/Simulink was used. The latter demonstrated a great ability (compared to the model made with EXCEL) to solve the problem and the results obtained were compared with those obtained with the EXCEL model. Finally, the results of these simulation tools were compared to the experimental results.

Speaker: Dr François BONNE (CEA/SBT)
• 83
Capacitive density measurement for supercritical hydrogen

A new approach for automotive hydrogen storage systems is the so-called cryo-compressed hydrogen storage (CcH2). It has a potential for increased energy densities and thus bigger hydrogen amounts onboard, which is the main attractiveness for car manufacturers such as BMW. This system has further advantages in terms of safety, refueling and cooling potential.
The current filling level measurement by means of pressure and temperature measurement and subsequent density calculation faces challenges especially for precise evaluation of the filling level. A promising alternative is the capacitive gauge. This measuring principle can determine the filling level of the CcH2 tank with significant smaller tolerances. The measuring principle is based on different dielectric constants of gaseous and liquid hydrogen, which is successfully utilized in liquid hydrogen storage systems (LH2).
The present theoretical analysis shows that the dielectric values of CcH2 in the relevant operating range are comparable to LH2, thus achieving similar good accuracy. The present work discusses embodiments and implementations for such a sensor in the CcH2 tank.

Speaker: Thomas Funke (Technische Universitaet Dresden)
• 84
Development of femtosecond laser vacuum cryogenic system

A cooling system is developed for femtosecond laser experiment. The system includes a vacuum tank and a cooling chamber. It uses liquid nitrogen and helium as cold source and resistive heater as power source which heats the cooled crystal. With the controlling strategy of PID, it can make the temperature of the cooled crystal changed continuously from 5 to 300K. In this paper, the structure of the whole system is introduced and the numerical simulation of the heat leakage and temperature field is presented. Finally, the experiment and the analysis of the difference between experiment and numerical simulation are given. From 5 to 80K, we use liquid helium as cold source, and the fluctuation of the temperature is lower than±0.5K; from 80 to 300K the liquid nitrogen as cold source and the fluctuation of the temperature is lower than±0.8K. Besides, for this system, a flexible pipeline transporting cryogenic liquid nitrogen and helium is invented. Using this flexible pipeline and a two-dimension move platform which is used for fixing the cooling chamber, the angle of the crystal can be changed more than±30°and the location can be changed more than±10mm.

Speaker: Dr Guopeng Wang
• 85
Flow balancing orifice for ITER Toroidal Field coil

Flow balancing orifice (FBO) are used in ITER Toroidal Field coil to uniform flow rate of the cooling gas in the side double pancakes which have a different length of the conductor of 99 m and 305 m,respectively.FBO consist of straight parts, elbows which are produced from 316L,tube 21.34 x 2.11 mm and orifices which are machined from the 316L rod. Each of right and left FBO contains 6 orifices, straight FBOs contain 4 and 6 orifices.Before manufacturing of qualification samples,JSC NIIEFA proposed to IO ITER new approach to provide the seamless connection between tube and plate therefore the most critical weld between orifice with 1mm thickness and tube was removed from the final design of FBOs. Since the proposed diameter of orifice is 4.5 mm which is three times less than the minimum requirement of the ISO 5167, therefore has been tasked to define correctness of calculation flow characteristic at room temperature and compare with experimental data. In 2015, the qualification samples of flow balancing orifices were produced and tested. The results of experimental data shown, that the deviation of calculated data less than 7%. Based on this result and other tests IO ITER approved design of FBO,which made it possible to start the serial production.In 2016 JSC “NIIEFA” delivered 50 FBOs to the IO ITER, i.e. 24 left side, 24 right side and 2 straight FBOs.To define the quality of FBOs has been prepared the test facility in NIIEFA.The helium tightness test at 10-9 m3·Pa/s under the pressure up to 3 MPa,the measuring of flow rate at the various pressure drops, the non-destructive tests of orifices and weld seams(ISO 5817,class B).Also other tests such as check dimensions and thermo cycling 300 - 80 - 300 K were carried out for each FBO.

Speaker: Alexander Litvinovich (JSC NIIEFA)
• 86
Frequency loss Induced Quench Protection System for High Temperature Superconductors

A fundamental problem with high temperature superconductors (HTS) is the high Tc values themselves and the stability that they impart. Low normal propagation velocities and high stability of HTS wires cause localized damage of magnet coils when there is a quench. Protection of HTS magnets for reliable operation has proven to be a challenge, particularly in Rare Earth Barium Copper Oxide (REBCO) superconductor, with the amount of energy that is required to get enough of the current into the metallic stabilizer to properly distribute the magnetic energy and minimize peak hot spot temperatures. A twist of a relatively new technique that relies on AC losses to distribute energy is Frequency Loss Induced Quench (FLIQ). FLIQ like CLIQ, drives an imbalance in the transport current between two or more sections of a magnet. In order to drive this imbalance, FLIQ uses an H-bridge design with IGBTs, whose gates are driven based on the feedback response of the voltage across the bridge. This system optimizes frequency, as current resonates at the frequency of the LC network across the bridge. This paper will discuss the novel circuit design, its working principle, and present representative data obtained on an insulated REBCO insert magnet coil.

Speaker: Kikelomo Ijagbemi (National High Magnetic Field Laboratory)
• 87
Magnetoresistance of The Cryogenic Linear Temperature Sensor

40 T hybrid magnet combining a set of resistive magnet with a superconducting outsert, was carried out at High Magnetic Field Laboratory, Chinese Academic of Science (CHMFL). The superconducting magnet is forced flow cooled with supercritical helium at a temperature of 4.5 K and pressure above 5 bar. The cryogenic Distribution Box distribute refrigeration power to the outsert superconducting magnets, and the helium temperature of the cryogenic Distribution Box is measured by cryogenic linear temperature sensor(CLTS).One CLTS nearest from 40T hybrid magnet appeared obvious magnetoresistance when superconducting outsert magnetic field is above 7T, and the magnetoresistance are plus or minus alternately with magnetic field,the largest temperature error is 1K.The magnetoresistance disappeared when superconducting magnetic field is below 7T.

Speaker: Mrs Qiumin Meng
• 88
Model-based PI tuning for the JT-60SA cryogenic system: experimental results

This papers deals with the Japan Torus-60 Super Advanced fusion experiment JT-60SA cryogenic system. It follows the results exposed in [1], in which a model of the whole JT-60SA cryogenic system has been presented, and in which PI controllers parameters have been calculated and simulated with a model-based approach. This paper will present the experimental results obtained on the refrigerator during the commissioning phase of the cryoplant. The PI loop that maintain the low pressure stable from the warm compression side has been calculated automatically with a model of the warm compression station and the resulting PI parameters have been applied to the cryogenic system. The same procedure has been applied on the pressure regulation of the supercritical helium loops using a model of the auxiliary distribution cold box. . This paper will prove that it is possible to calculate the PI parameters of the control loops before the machine has been built (with better results than the one that would have been tuned on-line) and thus to save time and reduce cost on utilities (fluids, electricity, etc.) on site, during the commissioning phase. This work is partially supported through the French National Research Agency (ANR), task agreement ANR-13-SEED-0005.

[1] : Modelling and Model-Based-Designed PID Control of the JT-60SA Cryogenic System Using the simCryogenics Library, F. Bonne, P. Bonnay, C. Hoa, G. Mahoudeau, B. Rousset. In proceedings of the 26th International Cryogenic Engineering Conference & International Cryogenic Materials Conference 2016, to be published.

Speakers: Dr François BONNE (CEA/SBT) , Christine Hoa (CEA SBT)
• 89
Overview of a low exported force and torque measurement facility

Increasingly, exported forces and torques (EFT) from cryocoolers and other mechanisms are a system level concern with lower levels becoming the norm for instruments with cryocoolers. EFT targets of ≤ 50 mN force and ≤ 25 mN-m torque in the 0-500 Hz range are expected. To meet these targets, Ball Aerospace developed both a low EFT cryocooler mount and a facility in which to make these measurements. This facility and its capabilities will be described herein.

Speaker: Ryan Taylor (Ball Aerospace and Technologies)
• 90
Pneumatic free valve actuators

Present cryogenic valves are mostly driven by pneumatic actuators. In general, PLC generated electrical analogue or digital signals are guiding control valves via an electro-pneumatic positioner and digital valves by switching an electromagnetic pneumatic pilot valve. One important advantage of pneumatic actuators is the failsafe function, either closed or open, in case of energy loss. However, the pneumatic air supply system and the electric signal cabling is complicated and the complexity increases with the number of valves. The pneumatic system is energy intensive, needs space and continuous servicing. Therefore operation and capital costs for such an electro-pneumatic system are quite high.
There are new developments in in the refrigeration, natural gas and energy industries which use pneumatic free electric driven control and shut-off valves.
Based on the positive experiences in these industries, innovative cryogenic and warm valves, actuated by an electrical stepper motor were developed. Together with the control module the full functionality including fail open or fail closed positions as well as many further control advantages are available. Using this type of valve allows a highly simplified installation. These advantages open a possibility to reduce operation and capital costs remarkably.
Already available are valves driven by an electrical stepper motor up to size DN40 depending on the requested shut-off pressure. For larger valves and higher shut-off pressures, innovative actuator systems with their own electro-hydraulic drive control system are available.
Examples of such valves will be shown and described. Development perspectives will be discussed.

Speaker: Mr Fridolin Holdener (shirokuma GmbH)
• 91
Superconducting magnet control system of JT-60SA

The JT-60U is being upgraded to a full-superconducting tokamak referred as the JT-60 Super Advanced (JT-60SA) as one of the JA-EU broader approach projects. JT-60SA will use superconducting magnets to confine the plasma and achieve a plasma current with a typical flat top duration of 100 second in purely inductive mode. The JT-60SA refrigerator will provide supercritical helium at 4.4 K for the superconducting toroidal field and poloidal field magnets, 50 K for High Temperature Superconductor Current Leads, 80 K for Thermal Shields, and 3.7 K supercritical helium for the divertor cryopumps. During typical plasma discharge scenarios magnets currents have to be ramped and controlled, helium pressures and flow rates in the cooling loops of the coils and structures have to be adjusted and temperature stability of several components has to be supervised. In abnormal situations the magnet system has to be discharged quickly and brought to a safe condition.
A supervising system called “magnet controller” is being developed to perform the different operation scenarios of the magnet system of JT-60SA.
One of the main control functions of the magnet controller is the smooth cool down of the magnet system. During the cool down, temperature differences between different sections of the magnet system and the structures have to be limited and the cooling requirements have to match the refrigerator´s capacity. Helium flow rates have to be split and distributed to the different JT-60SA loops in proportion to the their masses and specific heat capacities
In case of quench, the magnet controller triggers the ramp-down of the coil current by passing the quench signals from the quench detectors to the Supervisory Control System and Data Acquisition System (SCSDAS) and in parallel to the cryogenic system. In the contribution, the current status of the development of the magnet controller will be presented.

Speaker: Dr Koji Kamiya (Quantum radiology Science and Technology)
• 92
Testing and qualifying cryogenic safety valves at cold conditions

Cryogenic valves built into vacuum isolated coldboxes have to meet high requirements when it comes to tightness to vacuum, tightness to ambient, seat tightness or operational behavior. Since cryogenic tests are cost and time expensive, testing of valves during the manufacturing process is usually done at room temperature. Cryogenic tests however are sometimes necessary due to specific customer requirements or in form of a type test during the development and qualification process. Especially safety relevant cryogenic valves have to reach the highest operating reliability and should thus be tested under conditions as close as possible to the real operating conditions. This poster explains the different tests that were executed during the development, qualification and manufacturing process of cryogenic safety valves. It focuses in detail on the cold tests that were performed on the valves with cryogenic fluids and at cryogenic conditions.

Speaker: Pascal Erni (WEKA AG)
• 93
Theoretical analysis and coating thickness determination of a dual layer metal coated FBG sensor for Sensitivity Enhancement At Cryogenic Temperatures

Use of Fiber Bragg Grating (FBG) sensor is very appealing for sensing low temperature and strain in superconducting magnets because of their miniature size and the possibility of accommodating many sensors in a single fiber. The main drawback is their low intrinsic thermal sensitivity at low temperatures below 120 K. Approaching cryogenic temperatures, temperature changes lower than a few degrees Kelvin cannot be resolved, since they do not cause an appreciable shift of the wavelength diffracted by a bare FBG sensor. To improve the thermal sensitivity and thermal inertia below 77 K, the Bare FBG (BFBG) sensor can be coated with high thermal expansion coefficient materials. In this work, different metal were considered for coating the FBG sensor. For theoretical investigation, a double layered circular thick wall tube model has been considered to study the effect on sensitivity due to the mechanical properties like Young`s modulus, Thermal expansion coefficient, Poisson’s ratio of selected materials at a various cryogenic temperatures. The primary and the secondary coating thickness for a dual layer metal coated FBG sensor has been determined from the above study. The sensor was then fabricated and tested at cryogenic temperature range from 4- 300 K. The cryogenic temperature characteristics of the tested sensors are reported.

Speaker: Prof. Rajinikumar Ramalingam (Indian Institute of Technology Mandi)
• C1PoL - Large Scale Controls Exhibit Hall AB

Exhibit Hall AB

Conveners: Dr Bernd Petersen (Deutsches Elektronen Synchrotron) , Dr John Weisend (European Spallation Source ERIC)
• 94
ADS injector I cryogenic control system

Through the control system front pressure, temperature, flow rate and other process variables, ADS injector I cryogenic system is operated stably of 4k/2k. We adopts PlC control and EPICS integrate to realize the automatic intelligent control of the superconducting devices. The main function of PLC is building temperature realtime monitor system, logical control system, controlled by using PID of closed loop, safety interlock system, automatic SMS alarm system etc. EPICS is developed to integrate dates from pump system, refrigerator system, cryogenic equipment. This paper describes the ADS injector I cryogenic control system and how this is done.

Speaker: Mrs ye rui (yer@ihep.ac.cn)
• 95
Fermilab CMTF Multi-Level Cryogenic Distribution Control System

The Cryomodule Test Facility (CMTF) is a research and development facility, it houses a large state of the art cryogenic plant capable of providing a total of 500W of cooling capacity at 2 Kelvin. Its first test Cryomodule Test Stand (CMTS), 1.5m diameter and 9m long, is to test both 1.3 and 3.9 GHz cryomodules in Continuous Wave (CW) mode for the LCLS-II project. The cryogenic control system includes three subsystems, they are MyCom compressors, Linde super cryogenic plant and CMTS cryomodule cavity. Each subsystem control has to be independently design, but operate integrated together. Therefore, the CMTF multi-level distribution control system consist of two redundancy SIMATIC manager central controls, three Siemens PCS7-400 controllers as subsystem and seven DL205 PLCs as field control. Those authorized remote control centers are to be operate by synoptic HMI through Fermilab ACNET.

This paper presents a method which has been successfully used by many Fermilab distribution cryogenic control systems.

Speaker: Liujin Pei (Fermi National Accelerator Laboratory)
• 96
Remote monitoring system for the cryogenic system of superconducting magnets in the SuperKEKB Interaction Region

The SuperKEKB accelerator and the BELLE II detector have been developed to conduct high energy physics experiments at KEK.

A remote monitoring system was developed based on the software architecture of EPICS (The Experimental Physics and Industrial Control System) for the cryogenic system of superconducting magnets in the Interaction Region of the SuperKEKB accelerator.

These superconducting magnets are divided into three groups, the BELLE II detector solenoid, QCSL accelerator magnets and QCSR accelerator magnets. They are contained in three separated cryostats. Three helium cryogenic system are used to cool the cryostats respectively.

These cryogenic components of three groups are controlled by Hitachi integrated instrumentation system EX8000 on a dedicated local network from the perspective of security. The developed remote monitoring system enabled the persons concerned to monitor realtime data from the EX8000 on the KEK-LAN (a common local network in KEK) easily and safely. Users also can access and refer the past data easily.

EPICS offered software tools of IO control to communicate with the EX8000 using TCP/IP, archiving techniques using database and easy man-machine interface including various graphical tools.

The remote monitoring system realized to take more than 1000 data at once with the same cycle time of data acquisition as the EX8000. The data includes information of temperature, pressure, liquid-helium level, flow rate, electric current value, valve states and so on of three systems. The realtime and historical graphs, which are same as the EX8000, were made. The graphics displaying the all components of each cryogenic system were also developed to help users grasp the state of the system easily. It enabled users to refer to the same information as those on the EX8000 remotely, through the KEK-LAN.

Speaker: Ms Kanae Aoki (KEK, High Energy Accelerator Research Organization)
• 97
The control system of a 2kW @20K helium refrigerator

The automatic control of a helium refrigerator includes three aspects, that is, one-button start and stop control, safety protection control, and cooling capacity control. The 2kW@20K helium refrigerator’s control system uses the SIEMENS PLC S7-300 and its related programming and configuration software Step7 and the industrial monitoring software WinCC, to realize the dynamic control of its process, the real-time monitoring of its data, the safety interlock control, and the optimal control of its cooling capacity. This paper firstly detailed describes the control architecture of the whole system, including communication configuration and equipment introduction; and then introduces the sequence control strategy of the dynamic processes, including the start and stop control mode of the machine; finally tells the precise control strategy of the machine’s cooling capacity, including the safety interlock control strategy of the machine. Besides, in order to realize the unmanned operation, a remote control system is also simply described. Eventually, the whole system achieves the target of one-button starting and stopping, automatic fault protection and stable running to the target cooling capacity.

Speaker: Ms Wei Pan (State Key Laboratory of Technologies in Space Cryogenic Propellants ,Technical Institute of Physics and Chemistry, Chinese Academy of Sciences)
• 98
Use of Profibus for cryogenic instrumentation at XFEL

The European X-ray Free Electron Laser (XFEL) is a research facility and since December 2016 under commissioning at DESY in Hamburg. The XFEL superconducting accelerator is 1.5 km long and contains 96 superconducting accelerator modules. The control system EPICS (Experimental Physics and Industrial Control System) is used to control and operate the XFEL cryogenic system containing the XFEL refrigerator, cryogenic distribution systems and the XFEL accelerator. The PROFIBUS fieldbus technology is the key technology of the cryogenic instrumentation and the link to the control system. More than 650 PROFIBUS nodes are implemented in the different parts of the XFEL cryogenic facilities. The presentation will give an overview of PROFIBUS installation in these facilities regarding engineering, possibilities of diagnostics, commissioning and the first operating experience.

Speaker: Mr Torsten Boeckmann (DESY)
• C1PoM - Superconducting Magnet Systems - Cryogenics Exhibit Hall AB

Exhibit Hall AB

Conveners: Thomas Nicol (FNAL) , Wolfgang Stautner (GE Global Research)
• 99
Mobile Refrigeration System for Precool and Warmup of Superconducting Magnet

Conservation of helium has become more important in recent years due to global shortages in supply and increasing prices. MRI superconducting magnets use approximately 20% of the world’s helium reserves in liquid form to cool down and maintain operating temperatures at 4K. Efforts are being made to conserve helium in transporting superconducting MRI magnets by shipping them warm and cooling them down at end user locations (i.e. hospitals). These conservation efforts can also be extended to the service model at end user facilities.

This paper describes a mobile cryogenic refrigeration system that has been developed by Sumitomo Cryogenics for this purpose. The system can cool a typical magnet from room temperature to 40K in less than a week. The system consists of four single-stage Displex®-type GM expanders in a cryostat with heat exchangers integrated on the cold ends that cool the helium gas, which is circulated in a closed loop system through the magnet by a cryogenic fan.

The system is configured with heaters on the heat exchangers to effectively warmup a magnet or any remote thermal load. The system includes a scroll vacuum pump, which is used to evacuate the helium circuit with or without the remote load or magnet. Vacuum-jacketed transfer lines connect the cryostat to the magnet. The system is designed with its own controller for continuous operation of precool, warmup and evacuation processes with automatic and manual controls. The cryostat, pumps and gas controls are mounted on a dewar cart. Additionally, the compressors and system control are mounted on mobile carts to increase system flexibility.

Speaker: Mr Santhosh Kumar Gandla (Sumitomo (SHI) Cryogenics of America, Inc.)
• 100
The Connection of Refrigeration to a Superconducting Device with the Minimum amount of Cryogen

The shortage of helium, particularly liquid helium has made the use of cryogen free magnets attractive. The attractiveness of cryogen free device depends on the operating temperature of the device, the distance from the cold head to the device being cooled, the thermal conductivity of the connection, and the size of the object being cooled or cooled down. Connecting a cold source to something being cooled is similar to to connecting a vacuum pump to a device through a long pipe. This report will discuss cooling-down and cooling a device that operates over the temperature range from less than 2 K to 70 K. Two approaches will be discussed cooling using conduction through a high thermal conductivity metal straps and cooling using a thermal siphon cooling loop. The thermal siphon cooling loop can be designed to operate like a conduction cooled cryogen free device, where all of the fluid is stored in the cooling loop.

Speaker: Dr Michael Green (Lawrence Berkeley Laboratory)
• 101
The design of the new LHC connection cryostats

In the frame of the High Luminosity upgrade of the LHC, improved collimation schemes are needed to cope with the superconducting magnet quench limitations due to the increasing beam intensities and particle debris produced in the collision points. Two new TCLD collimators have to be installed on either side of the ALICE experiment to intercept heavy-ion particle debris. Beam optics solutions were found to place these collimators in the continuous cryostat of the machine, in the locations where connection cryostats, bridging a gap of about 13 m between adjacent magnets, are already present. It is therefore planned to replace these connection cryostats with two new shorter ones and a by-pass cryostats in between where the collimators can be placed close to the beam pipes. The connection cryostats, of a new design as compared to the existing ones, will still have to insure the continuity of the technical systems of the machine cryostat (i.e. beam lines, cryogenic and electrical circuits, insulation vacuum). This paper describes the functionalities and the design solutions implemented, as well as the plans for their construction.

Speaker: Arnaud Vande Craen (CERN)
• M1PoA - Focused Symposia - Propulsion III: Materials, Technologies, Drivetrain Machines Exhibit Hall AB

Exhibit Hall AB

Conveners: Dr Anna Kario (Karlsruhe Institute of Technology, ITEP) , Takanobu Kiss (Kyushu University)
• 102
Computational Investigation of Superconducting Magnetic Energy Storage (SMES) Devices to Optimize Energy Density

Superconducting magnetic energy storage (SMES) devices offer attractive and unique features including no theoretical limit to specific power, high cycling efficiencies and charge/discharge rates, and virtually no degradation with cycling. The mass-specific energy density (MSED) of SMES systems; however, falls short of many needs. This paper examines SMES energy densities of solenoid-type magnets for YBCO, MgB2 and Nb3Sn wires using present-manufactured wires and future advancements predicted from lab samples. Scaling of maximum energy density with the stored energy, length of the conductor and radius of the bore were established with numerical simulations, and studied for a range of stored energies from 0.1 MJ to 250 MJ and operating temperatures of 4.2, 18, 40 and 65 K. With dependence of critical current on field taken into account, the optimum magnet design for varying superconducting wires also including H//c is a pancake coil with scaling of energy density ε ~ E^1/3. Thus, current and magnetics limits achievable ε only at a fixed E. The overall limit on ε is also imposed by the virial theorem. Without additional structural support ε of SMES magnets is limited to ~ 30Wh/kg. However with introduction of light-weight and strong support materials the upper limit MSED of SMES is expected to exceed that of the best batteries ε ~ 150 Wh/kg.

Acknowledgments: Air Force Office of Scientific Research (AFOSR) and The U.S. Air Force Research Laboratory, Aerospace Systems Directorate (AFRL/RQ).

Speaker: Dr Thomas Bullard (UES Inc.)
• 103
Design Optimization of a Superconducting Gas-Insulated Transmission Line

It is envisioned that High Temperature Superconducting (HTS) power cables could replace conventional cables in applications where space and weight are the limiting design factors. In situations where significantly higher power densities (both volumetric and gravimetric) are required and variable power ratings are preferred, it is necessary to operate HTS cables at temperatures lower than the LN2 range. Gaseous helium (GHe) circulation has been demonstrated as a viable option for cooling HTS power cables. GHe has a lower dielectric strength compared to LN2 and low partial discharge inception voltages have been noticed due to the helium gas trapped in the butt gaps of the insulation layers. Recent efforts on enhancing the dielectric strength of GHe by the addition of small mole fraction of hydrogen (H2) have shown that this mixture can double the dielectric strength of pure GHe.
To exploit this phenomena and to avoid the limitations posed by the traditional insulation designs, a new and novel cable design has been proposed where the helium-hydrogen gas mixture acts as both the coolant and insulation medium. Proof of concept experiments demonstrated that the new cable design allows higher operating voltages than what is currently possible as well as have other potential benefits. In terms of dielectric design, this idea is similar to SF6 gas insulated transmission lines (GIL) which operate at room temperature and hence we decided to name it “superconducting gas-insulated transmission line (S-GIL)”. This study extends our previous research and focuses on the optimization of the cable design. Experimental results on the dielectric rating for the different design parameter selected for the gas insulated HTS power cables will be presented. Details of the challenges encountered and innovative solutions devised for the S-GIL design will also be presented.
This work is funded by the Office of Naval Research.

Speaker: Peter Cheetham (Center for Advanced Power Systems)
• 104
Research on High TCS project for Gobi Photovoltaic Development

Since energy deficiency and global warming become most serious, it is anticipated global PV installment will reach 230 GW. China has urgent need to use PV to replace its coal-based (over 70%) energy structure. In last 4-5 years China becomes the world largest PV produce and user. Moreover, in China’s plan, about half of the PV electricity are generated from distributed systems, the other half are from Gobi, which has an area of 1.3 million km2 and ample sunshine. In 2012, 9 GW PV power stations are completed in Gobi. Currently the largest PV stations in the world are built in Gobi (about 20 GW). There are still many problems for power transmission from these power stations in deserts. Using HTS transmission lines is promising, while the current density is uniform only within a few meters (not km), which still limit its production yields, resulting in high sale price. Advance HTS technology are still under development for low cost, which are the determined factors for future applications.
It is critical to solve the nonuniform composition problem of the YBCO films by either PVD or CVD for better quality. The composition variations in YBCO affects its critical current density. Therefore, it is challenge to control the YBCO film composition. Also, the pinning issue is still unsolved, and its relationship to the film uniformity is still not understood. In this work, we succeeded in developing Raman scattering as a tool to identify the change of film compositions. We also correlate it with XPS results. Finally we succeed in developing a Metal Organic Sputtering, which adjust the specific MO flows to tune the film compositions. In this work we will report the composition finding using Raman shifts and its correlation with XPS, which will help improve the control of YBCO current density distributions.

Speakers: Prof. Huey-liang Hwang (Shanghai Jiao Tong University) , ChengChao Jin (Shanghai Jiao Tong University)
• 105
Status of Cryogenic and Superconducting Components for MW-Class Electric Power Systems

Superconducting and cryogenic power system components are understood to have strong advantages for MW-class power systems, such as greatly reduced weight, size and heat loss and increased energy efficiency. In this work, the unique properties and technical readiness assessment of cryogenic and superconducting components will be reviewed, and compared to alternate traditional technologies such as Cu-wire based and semiconducting. For almost every component considered, superconductor devices typically provide 5-10x and sometimes larger reductions of weight and heat loss, and even 3-10x reductions at the system level. There are also other advantages such as greatly increased lifetime and potentially much higher reliability in operation, because of significantly less mechanical degradation from high heat stressing and wear. The improved properties can enable the development of new capabilities for aerospace systems, such as vertical-take-off-and-lift (VTOL) with lightweight components, 2-5x higher improved energy efficiencies from electrical propulsion, and reduced operation noise.
Acknowledgments: Air Force Office of Scientific Research (AFOSR) and The U.S. Air Force Research Laboratory, Aerospace Systems Directorate (AFRL/RQ)

Speaker: Timothy Haugan (U.S. Air Force Research Laboratory)
• 106
Study on the adjustment capability of the excitation system located inside superconducting machine electromagnetic shield

The quick adjustment capability of the excitation system plays a very important role in maintaining the normal operation of superconducting machines and power systems, but the eddy currents in the electromagnetic shield of superconducting machines will hinder the exciting magnetic field change and weaken the adjustment capability of the excitation system. To analyze this problem, a finite element calculation model for the transient electromagnetic field with moving parts is established. The effects of different electromagnetic shields on the exciting magnetic field are analyzed using finite element method. The results show that the electromagnetic shield hinders the field changes significantly, the better its conductivity, the greater the effect on the superconducting machine excitation.

A 6-pole superconducting synchronous generator without electromagnetic shield and with three different electromagnetic shields was calculated using finite element model for the transient electromagnetic field with moving parts. By means of doubling and reversing the exciting coil terminal voltage, the exciting current in the exciting coil of the superconducting machine is changed. The changing process of the magnetic field, the eddy current inside electromagnetic shield and the terminal voltage of the A phase stator armature winding with the exciting current is obtained by calculation. The better conductive property of the electromagnetic shield can improve its shielding ability, but also reduce the excitation adjustment ability of superconducting synchronous machines.

Acknowledgements
This work was supported by the National Nature Science Foundation of China (NO. 51377151).

Speaker: Prof. Dong Xia (Institute of Electrical Engineering, Chinese Academy of Sciences)
• M1PoB - YBCO Coated Conductors I: Processing & Properties Exhibit Hall AB

Exhibit Hall AB

Conveners: Lance Cooley (FNAL) , Dr Anna Kario (Karlsruhe Institute of Technology, ITEP)
• 107
Auger Electron Spectroscopy and Ar Sputtering for the Determination of Y2O3 Buffer Layer Thickness in REBCO Superconducting Tapes

Thanks to recent advances in flux pinning, current-carrying capacity, and conductor geometry, REBCO tapes are being considered more seriously for high-field magnet applications. However, the material remains intrinsically weak to transverse tensile stresses, and the buffer and/or superconducting layer in the tape can delaminate when subject to such stresses. In this work we use Auger Electron Spectroscopy (AES) to specify the composition of the delaminated layer, and use AES argon sputtering to determine the thickness of the buffer layers in a REBCO film, after fabrication and again in the delaminated layer after mechanical testing. A depth profile is created by alternating Ar sputtering and AES testing. The ratio of yttrium and aluminum (from two buffer layers in the delaminated tape) are compared and a cross-over point is defined (based on sputtering of samples with known buffer layer thicknesses) to allow quantitative comparison of the thickness of the surface buffer layer retained after delamination. Using this approach, the properties of the delaminated layer (such as the chemistry, thickness, and thickness variation) can be determined.

Acknowledgments: This work was financially supported by the U.S. Department of Energy, Office and High Energy Physics, award DE-FG02-13ER42036, and benefited from the support of the Materials Science & Engineering Center at UW-Eau Claire. The authors thank SuperPower, Inc. for providing the samples under investigation.

Speaker: Mr Christopher Hopp (Materials Science & Engineering Program, University of Wisconsin-Eau Claire)
• 108
Commercial fabrication of 2G HTS Roebel cables using the “Punch-and-Coat” approach

We will present the status of commercial production of 2G HTS Roebel cables along the advanced “Punch-and-Coat” route.

The “Punch-and-Coat” approach to 2G HTS Roebel cable fabrication was recently developed in collaboration between KIT and SuperOx. The approach is to prepare a meander-shaped strand for Roebel cable by mechanical stamping of silver-finished 2G HTS wire, and then electroplate stabilising surround copper coating onto the strand. As a result, the wire architecture, along the entire strand, is fully encased in copper and is thus geometrically symmetrical and protected from delamination. Moreover, the copper coating, added after punching, smoothens the punching burr on the substrate, making it no hazard for the adjacent strands. The “Punch-and-Coat” strand fully retains its original critical current after 200 thermal cycles between 77 K and room temperature. Before the cable is assembled, the strands are routinely characterised along the entire length by the magnetic non-contact and direct transport critical current measurements at 77 K.

SuperOx has successfully commercialised the fabrication of “Punch-and-Coat” 2G HTS Roebel cables, delivering multiple cables for HTS insert coils for high field accelerator magnets, as well as for stator coils for HTS rotating machines.

Speaker: Dr Alexander Molodyk (SuperOx)
• 109
Comparative Study on the effect of Laser Energy Density on YGBCO and HGBCO Thin Film Prepared by PLD

Y0.5Gd0.5Ba2Cu3O7-σ (YGBCO) and Ho0.5Gd0.5Ba2Cu3O7-σ (HGBCO) targets of similar density are prepared by solid-state reaction method. These targets are used to prepare superconducting thin film respectively using pulsed laser deposition (PLD). During the experiment, we alter laser energy by changing optical lens. X-Ray diffraction (XRD) is adopted to analyze the structure and texture of R0.5Gd0.5Ba2Cu3O7-σ (RGBCO, R=Y, Ho) thin film. Also, atomic force microscopy (AFM) and scanning electron microscopy (SEM) are used to observe the surface morphology, and superconducting current is measured in 77K by employing standard four-probe method. The laser energy density and different doping element can affect properties of YRBCO thin film, which may be related to target particle ejection process and size of rare earth atoms.

Speaker: Xiang Wu
• 110
Demonstration of New 3 to 4 mm Thin ReBCO-CORC Wires featuring 300 to 500 A/mm2 at 10T/4.2K

Several improvements on ReBCO tape performance made it possible to reduce tape width and thickness thereby enabling the process of making thin CORC based ReBCO wires. A major improvement has been the reduction of the tape’s substrate thickness from 100 via 50 to 30 micron and even more reduction is expected in the years to come, leading to a lower minimum bending radius of ReBCO tapes. The combination of thinner substrate and narrower tapes allows production CORC wires with enhanced flexibility while maintaining a high current density. It makes CORC round wires suitable for application in all kinds of high field magnets and insert coils. It also opens up the application area of extremely stable magnets operating in 20 to 50 K range. Several CORC wires with different tape layouts were tested in the frame of the CORC wire development program of CERN, ACT and the University of Twente. The 3.0 to 4.5 mm diameter CORC wire samples built with 2 and 3 mm wide tapes are tested as few-turns solenoids at 4.2 K in a magnetic field up to 10.5 T. The tests are performed to demonstrate the ease of use and high performance of the new CORC wires. It also allows optimization of the wire manufacturing process, wire bending procedure and exercising joint terminal production. Step by step wire production has improved and wire flexibility as well as current density increased. Developments are ongoing and further increase in current density and wire flexibility is expected.

Speaker: Tim Mulder (Twente Technical University (NL))
• 111
Post-Delamination Structural Investigation of REBCO Superconducting Tape

Rare-earth cuprate-based (REBCO) superconductors are a family of high-field, high-temperature superconductors fabricated in a tape geometry. The tape structure is composed of a nickel-based Hastelloy substrate base, with oxide buffer layers (to allow for epitaxial growth of the superconductor) and a superconducting film of thickness < 2 μm. The composite is finished with a silver cap layer and a Cu stabilizing layer. One limiting factor for REBCO tapes in a superconducting magnets is the possibility of transverse delamination within the tape; however, the microstructural features that control this delamination behavior are not fully understood. For this study we have developed new sample preparation methods (and subsequent imaging by SEM and laser confocal microscopy) to quantify the damage modes present in delaminated samples. Specifically, we investigate the morphology of the delaminated surface and the retained layers on the tape to ascertain the nature of the crack initiation and propagation. Ultimately, a more thorough understanding of the delamination behavior of this material may lead to improvements in the tape processing to minimize this effect in the future.

Acknowledgments: This work was financially supported by the U.S. Department of Energy, Office and High Energy Physics, award DE-FG02-13ER42036, and benefited from the support of the Materials Science & Engineering Center at UW-Eau Claire. The authors thank SuperPower, Inc. for providing the samples under investigation.

Speaker: Tanner Olson (University of Wisconsin-Eau Clarie)
• M1PoC - NbTi/Nb3Sn/A15 Processing & Properties I Exhibit Hall AB

Exhibit Hall AB

Conveners: Xuan Peng (Hyper Tech Research Inc.) , Xingchen Xu (FNAL)
• 112
Demonstration of a Wind and React Nb3Sn Solenoidal Coil Segment for MRI Application

A standard tube-type Nb3Sn conductor was used for the winding of a sub-size MRI-like coil segment. The conductor was 0.8 mm OD and had 217 filaments, with a 45% non-Cu fraction. The wire was twisted, reacted, and then insulated with s-glass. After insulation, the coil was wound on a 1 m OD copper former. The total length of the conductor used was 1.6 km. The coil was instrumented for low temperature testing and then epoxy impregnated. Ten sets of voltage taps and ten thermocouples were used, along with two Cernox sensors and two hall probes (these latter for field measurements). The coil was installed into a large conduction cooled cryobox for cooldown and testing. The coil was cooled by a series of Cu straps which were bolted to the coil ID and then to a Cu cooling ring which was itself connected to two Sumitomo cryocoolers (1.5 W at 4 K each). The coil was surrounded with superinsulation and then sealed in the cryobox. Cool down hit a base temperature of 4 K, with a cool down time of 2 days. A small (1 A) current was applied to the coil during cool down and the coil was seen to have a Tc of 17 K. The maximum temperature difference across the coil was 1.5 K. After the initial cooldown the coil temperature was increased, and Ic was measured as a function of temperature with decreasing temperature. The coil transitioned by n-transition. The radial field of the coil was measured on the former (near the winding) and used to compare coil Ic to short sample Ic via a load line plot.

Speaker: Mr Jacob Rochester (The Ohio State University)
• 113
Design and Performance Considerations for Superconducting Magnets in the Material Plasma Exposure eXperiment

An important step in the development of fusion as a future power source is the development of plasma facing materials that can function over long periods of time. While ITER and other devices like Wendelstein 7-X and the Joint European Torus will provide insights into divertor and first wall performance, a dedicated device to advance the understanding of material performance in representative plasma environments is needed. The Material Plasma Exposure eXperiment (MPEX) has been proposed as a linear plasma device to generate fusion reactor-like plasma energy and particle flux at the target materials with electron temperatures of 1-15 eV and electron densities of 10^20 to 10^21 m-3. A design study was completed to assess the feasibility of superconducting magnets using materials such as Nb3Sn, NbTi, MgB2, and YBCO from liquid helium to liquid nitrogen temperatures with respect to commercially available conductors. for superconducting magnets need warm bore diameters of 43.2 cm with non-uniform central fields between 0.4 T and 2.4 T. While NbTi was selected for the superconducting magnet due to its low risk the use of MgB2 and YBCO presented unique benefits that could outweigh these risks if certain performance milestones can be met.

 This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan

Speaker: Robert Duckworth (Oak Ridge National Laboratory)
• 114
Niobium for Long-Length Fine-Filament Nb3Sn Conductors

Nb used in Nb3Sn multifilamentary superconductor wire deforms throughout the fabrication process including the initial extrusion and subsequent drawing, restacking, re-extrusion, and final drawing steps. Unfortunately niobium, usually begins as a 300 mm diameter ingot with extremely large grains. While this ingot gets reduced to a 120-150 mm diameter bar before wire fabrication, the cast macrostructure persists. The result during wire fabrication is often non-uniform Nb – Cu co-deformation, the development non-circular Nb filaments, and the tendency for the filaments to sausage and fracture when the diameter gets small (5-10 microns). To improve conductor performance and meet the needs of advanced magnet applications, larger starting Nb bars and smaller diameter Nb filaments in Nb3Sn strands are needed. This can be accomplished by using highly grain-refined and homogeneous large cross section bars of Nb processed by severe plastic deformation. Microscopy including texture characterizations, and mechanical property measurements are reported on the grain refinement of a 175 mm diameter bar of Grade 1 Nb, to be used to fabricate a prototype multifilamentary Nb3Sn wire. This work presents success with scale-up of a new severe plastic deformation process as applied to starting Nb bar in the Nb3Sn wire fabrication process

Speaker: Mr Robert Barber (Shear Form, Inc.)
• 115
The study of high RRR value of wire in channel superconductor wire

This paper studies preparation process and its technology of high RRR value of Wire in channel (WIC) NbTi superconductor wires. It is generally accepted that the lower the oxygen content in the oxygen-free copper, the higher RRR value. In this paper, the results show that the RRR of WIC wire also can achieve relatively high levels under the high oxygen content condition.
The first method is online annealing on medium frequency furnace, cooling, fluxing, and then soldering using C10100 copper channel wire. When the heating power was higher, the RRR value can meet the requirement of more than 175. But the surface quality of WIC wire and inserting effect were poor.
The second method is using C10100 copper channel wire heat in the vacuum furnace, fluxing, and then soldering. The RRR values of WIC wire were 213-256, with the surface quality and inserting effect were good.
The third method is using C11000 copper channel wire to solder directly. The oxygen content of the selected C11000 copper channel wire ranges from 75 to 200 parts per million (PPM). The RRR value of WIC wire can be improved to 240-260.
In order to study the problem, using C11000 and C10100 to heat at 500 ℃ for 2 hours, and then the microstructure was observed. The C10100 still exist dislocation etc. defects. And the C11000 have no dislocation and other defects basically, which increase RRR values. In addition, the second-phase was found in grain boundary of C11000, which was Cu2O phase.
The oxygen content of C11000 can exist in the form of Cu2O, which do not affect the increase of low temperature resistance. If oxygen element exists in the form of gap element, it will greatly increase the low temperature resistance, and reduce lower RRR value.

Speaker: Mrs kaijuan yan (Western superconducting technologies co., LTD)
• 116
Thermal-mechanical properties of epoxy-impregnated Nb3Sn composites for 15 T dipole magnets

Knowledge of thermal-mechanical properties of epoxy-impregnated superconductor/insulation composite is important for designing and fabricating high field superconducting magnets towards their ultimate potentials. As a part of the 15 T dipole magnet program at Fermi National Accelerator Laboratory, we report the study of the mechanical properties and thermal contraction of epoxy-impregnated Nb3Sn Rutherford cable stacks made from the state-of-the-art RRP strands at room temperature and cryogenic temperatures. Stress-strain curves of such composite materials were tested under both monotonic and cyclic compressive loads. The effect of varying the insulation wrapping of the Rutherford cables is also investigated.

Speaker: Pei Li (Fermi National Accelerator Laboratory)
• M1PoD - NbTi/Nb3Sn/A15 Processing & Properties II Exhibit Hall AB

Exhibit Hall AB

Conveners: Lance Cooley (FNAL) , Dr Michael Eisterer (TU Wien, Atominstitut)
• 117
Advanced tube type Nb3Sn conductor in Hyper Tech

Tube type Nb3Sn conductor has been being explored by Hyper Tech Research Inc. Our standard conductor with 217 filament arrays have been generated with 12 T non-Cu Jc values of about 2400-2500 A/mm2 with filament size of 40 micros at the 0.85 mm strand. We also made 547 filament conductor which has filament size of 25 micros at the 0.85 mm strand without any drawing issue. We are working to improve the non-Cu Jc further. In this paper, creating artificial pinning centers has been used to increase flux pinning in order to raise the Jc overall in the 12-20T range within the tube type Nb3Sn strands. As a result, the artificial pinning centers refine the grain size by at least half, thereby increasing the layer Jc by at least 30%. This strand has been made to 61-filament restack and getting filament size of 45 micros at the 0.5 mm strand.

Speaker: Xuan Peng (Hyper Tech Research Inc.)
• 118
Effect of external contaminants on RRR of Nb3Sn strands for the HL-LHC Accelerator Upgrade Project

Nb3Sn wire used in accelerator magnets is purchased with a typical specification that copper residual resistivity ratio RRR should be >150, to assure that magnets have adequate thermal conductivity for quench protection. While the primary intention of the specification is to control internal contamination of copper by tin, what is not controlled is external contamination. Standard practice uses pure argon during coil reaction, which is assumed to be a clean environment. This presentation will describe results from strand procurement leading up to the HL-LHC Accelerator Upgrade Project, which cause the cleanliness assumption above to be questioned. Reproducible RRR of ~300 was obtained when 0.85 mm diameter wire samples were protected inside a 1 mm inner diameter quartz tube during reaction, or when reactions were carried out in a scientific high-vacuum furnace. However, RRR values closer to 200, and with much wider scatter, were obtained when the external strand surface was exposed to the argon environment. Evidently impurities in the argon gas or residues of furnace elements and prior heat treatments affect RRR. The difference for protected versus exposed strands has been cross-checked and validated between different furnaces at different laboratories. The presentation also explores whether the insulation on coils offers any protection, which has bearing on project risk. Actual RRR from strands extracted from insulated and exposed cables will be compared to results for raw strands. Analysis of externally introduced impurities in protected and exposed strands by secondary ion mass spectroscopy will also be presented. Guidance will be provided about reaction methods and interpretation of RRR data based on the results.

Speaker: Lance Cooley (Fermilab)
• 119
Efficacy of Tantalum Tungsten Alloys for Diffusion Barrier Applications

Traditionally either Niobium, Tantalum or a combination of both have been used as diffusion barriers in Nb3Sn Multi-filament wire. Vanadium has also been used successfully but the ultimate RRR of the copper is limited unless an external shell of Niobium is included. Niobium is preferred over Tantalum when alternating current losses are not an issue as the Niobium is more ductile but will react to form Nb3Sn. Pure Tantalum tends to deform irregularly requiring extra starting thickness to ensure good barrier qualities. Here we report that Tantalum lightly alloyed with Tungsten is compatible with the wire drawing process while deforming as well as or better than Niobium. Ta3wt%W has been processed as a single barrier and as a distributed barrier to fine dimensions. In addition, the higher modulus and strength of the Ta W alloy improves the overall tensile properties of the wire.

Speaker: David Smathers (H.C.Starck)
• 120
Improvement of stability of Nb3Sn conductors and magnets by increasing specific heat

This work aims to improve stability of Nb3Sn superconducting wires and magnets by increasing specific heat of Nb3Sn conductors. A technique is put forward to introduce substances with high specific heat (e.g., Gd2O3, whose specific heat capacities are hundreds of times larger than those of Nb3Sn wires at ≤5 K) to Nb3Sn wires. This technique is well compatible with present Nb3Sn wire manufacturing technology. Wires based on this technique have been fabricated and drawn to 25 µm subelement size without breakage. Measurement results demonstrate that this technique can noticeably improve conductor stability, without causing bad side-effects (such as reduced RRR or Jc). This new type of Nb3Sn wires are promising for large-scale applications; compared with conventional Nb3Sn conductors, they are expected to greatly suppress training and instability of superconducting magnets.

Speaker: Xingchen Xu (Fermi National Accelerator Lab)
• 121
Optimized (Nb,Ti)3Sn multifilamentary wire with ZrO2 APCs for high Jc, high Bc2, and low AC loss

In this work we explore the development of an optimum high-Jc multifilamentary (Nb,Ti)3Sn wire containing ZrO2 APCs. First, 61-filament powder-in-tube (PIT) wires containing oxide powders were explored. These wires consist of a Nb-1%Zr tube containing Cu, Sn, and oxide powders. SnO2 and CuO powders were used, and SnO2 was found to release oxygen more readily. These samples were heat-treated at 450°C for 100h and then 650°C for 200h, with a ramp rate of 50°C/h. Incomplete Nb3Sn formation was observed, indicating a need for higher Sn-Nb ratio and longer heat treatment time. New 61 subelement designs were made to achieve higher Sn/Nb ratios; these results are discussed. Next, we performed some initial work in order to develop a ternary wire. In this experiment, an externally oxidized tube-type wire was manufactured, starting from a precursor of Cu-Sn-Ti rod in a Nb-1%Zr tube. Samples were heat-treated in a vacuum sealed quartz tube with CuO present. Heat treatment schedules included 20°C/h up to 650°C for 300h, and 20°C/h up to 700°C for 100h. Grain refinement below 35nm was observed due to the influence of Ti and ZrO2. Then, a 61-filament tube-type wire was produced consisting of a Cu-Sn-Ti rod inside an oxide-containing Nb-Zr tube. Temperature ramp rates of 15, 20, and 30°C/h, as well as several final heat treatment times ranging from 100 to 300 hours at 650°C were evaluated to ensure complete diffusion of O, Ti, and Sn to maximize the quantity of ZrO2 precipitates, composition of ternary phase, and area fraction of fine-grain Nb3Sn, respectively. FG Nb3Sn grain sizes were maintained below 35nm, and superconducting layer Jc above 9600A/mm2 was observed at 4.2K and 12T.

Speaker: Mr Jacob Rochester (The Ohio State University)
• 122
The influence of processing methods and test methods on the n value of wire in channel superconductor wire

The n value of wire in channel (WIC) NbTi superconductor wires represents the deformation uniformity of internal filament, which is one of the most important properties of superconductor wire. This paper studies the influence of processing methods and test methods on the n value of WIC superconductor wire.
In the processing methods, the filaments positions, filament diameters, twist pitch and processing rate are considered. And the results show that processing methods have no significant influence on the n value. In different filaments positions, the sizes of monofilament are uniform and no foreign body sensation. With the increase of filament diameters, the filament numbers decrease, the n values show no significant changes. And With the increase of twist pitch, the n values show no significant changes. With the increase of processing rate, the n values show no significant changes.
In the low-temperature test methods, many factors are considered. The results show that there have no effects on n value in different outer diameters and different materials of barrel, the connection, sample-preparation and assembling of low temperature part, winding direction in the processing of WIC wire sample-assembling, contact area of current lead. The different groove type of barrel, the slight different sample fastening, and the n value changes slightly. With the increase of loading speed of current, n values have no obvious change. When the current lead of sample holders gives out heat, the n value has no obvious change. Different signal acquisition modes are studied in data and X-Y recorder, the n value has no change. But the lorenz force have important effect on n value. When the direction of lorenz force departs from the barrel center, the n value can increase about three times than the direction of lorenz force towards to the barrel center because the barrel become loose.

Speaker: Mrs Kaijuan Yan
• M1PoE - Superconductors I: Measurements, Mechanical, Electrical, Stability, AC Loss Exhibit Hall AB

Exhibit Hall AB

Conveners: Takanobu Kiss (Kyushu University) , Dr Milan Majoros (The Ohio State University)
• 123
AC losses of Round Superconducting Cables Subjected to Time-dependent and/or Rotating Magnetic Fields

An analytical approach is used to calculate the AC losses of round superconducting cables subjected either to external fields applied perpendicularly to the cable length. Losses for fields applied in one fixed direction but varying sinusoidally in time are compared to losses for applied fields with fixed (with time) amplitudes that rotate around the sample (rotating around an axis parallel to the cable length). Such losses are then calculated for fields which both rotate around the sample and have an amplitude which varies with rotation angle. It is shown that rotating fields can be treated as a superposition of orthogonally applied fields in some cases.
The influence of the shape of the strands that make up the cable are explored, with a round strand shape compared to a tape-like geometry. AC losses are divided into hysteresis loss, coupling loss, and eddy current loss, and the effects of both sample and field geometry are explored for each loss component. At last, the proposed analytical method is used to calculate the AC losses of some samples, and the results are compared with those from the numerical simulation based on Comsol Multiphysics and experimental data quantitatively.

Speaker: Mr Kun Dong (The Ohio State University)
• 124
Current sharing, quench, and normal zone propagation in YBCO CORC cables

A fifteen layer CORC (Cable on Round Conductor) cable, 82 cm long, was tested for stability and normal zone propagation at 77 K in liquid nitrogen bath. The cable had 15 layers, each layer containing 3 tapes, 4 mm wide each. The cable was instrumented with thermocouples, potential taps and wires including as well as excluding its current lug connections. 3 heaters were placed on top of the cable’s central part (one on each tape). The heaters were connected in series and allowed pulses of various powers and durations to be generated. Around the heaters thermocouples were distributed on each tape to measure heating during a quench. DC transport currents of some percentage of the cable critical current (1500 A) were applied. During and after the heat pulse current redistribution among the layers and within the cable current lugs was measured by high speed data acquisition card (DAQ) controlled via LabView software. These results were compared to a Roebel cable measured for quench at 4.2 K in liquid helium and 10 T.

Speaker: Milan Majoros (The Ohio State University)
• 125
Status of Round Robin Test for Tensile Test on REBCO Wires at Cryogenic Temperature

Within the framework to establish standards of test methods for superconducting technical wires, various standards have been published by the International Electrotechnical Commission IEC (standard documents IEC 61788-1 to -20). Following the experience of the successful Round Robin Test RRT for Tensile Test on REBCO Wires at Room Temperature, the effort is extended to Tensile Test on REBCO Wires at Cryogenic Temperatures and is coordinated by CryoMaK lab in KIT. A round robin test is an inter-laboratory test (measurement, analysis, or experiment) performed independently several times in different laboratories. Identical samples are tested using identical or similar test procedure. Results analysis from different participants allows evaluation of the reproducibility of the test method and processes, and the proficiency of participating labs. Different commercially available five ReBCO wires from five different manufacturers and one BiSCCO wire from another supplier are purchased for testing. Materials are provided by VAMAS TWA 16. Samples are distributed between nine participating labs from five different countries. After the measurements are performed according to specified guidelines, the results will be evaluated statistically using F test to investigate the amount of scatter in the test results. The final goal of RRT is to issue an ISO/IEC Standard for cryogenic temperature tensile test for REBCO wires.
In this report the status and details of Round Robin Test on REBCO Wires at Cryogenic Temperatures are presented and discussed.

Speaker: Nadezda Bagrets (Karlsruhe Institute of Technology – KIT)
• 126
YBCO pancake coils wound using electrically non insulated tapes: current sharing, stability, quench, and NZP measured at 4.2 K and 10 T

YBCO coated conductors are of interest in a number of possible High Energy Physics applications, like e.g. high field solenoids for muon colliders. A new approach in making YBCO magnets has been suggested recently, where the coils are neither insulated nor epoxied. It is believed that in this approach, the coil is much easier to protect, because one a given zone becomes normal, the lack of insulation lets it share its current to the next winding layer down. Essentially, the various coil windings are no longer completely in series once a normal zone forms. In principle, the current can be shared across the whole winding, thus essentially serving both to re-route the current, but also to distribute the energy, as quench heaters would in a normal active protection scheme. In the present work we have measured current sharing, stability, quench and normal zone propagation in such a YBCO pancake coil at 4.2 K in liquid helium bath. The experiments have been done in applied magnetic fields up to 10 T at transport currents of a certain percentage of the coil critical current. The coil winding was instrumented for voltage and temperature measurements at several places around the winding, such that both radial and azimuthal quench propagation could be measured. A heater was placed on the inner-most part of the winding. Heat pulses of various powers and durations were generated to measure quench and NZP. Obtained results are compared with our previous measurements on a coil wound using a kapton insulated YBCO tape.

Speaker: Dr Majoros Milan (The Ohio State University)
• M1PoF - HTS and LTS Cables I Exhibit Hall AB

Exhibit Hall AB

Conveners: Robert Duckworth (ORNL) , Arend Nijhuis (University of Twente)
• 127
DOCO-HTS-Roebel cables, a concept for higher currents

Roebel cables from HTS coated conductors are used in the first real application, in dipole insert magnets for particle accelerators, performed in a work package of the EU-project Eucard2 of CERN. Following-up the first sub-size dipole magnet demonstrator, future full-size magnets require cable designs with significantly enhanced operation currents for favorable magnet impedance, for accelerator magnets as well as for TF-magnets of the future fusion reactor DEMO. The Roebel geometry is quite flexible to enhance the number of strands, either using stacks or increasing the transposition pitch. Both methods however have disadvantages for the application in coils and may lead to higher stress load depending on the coil details.
A proposed new concept extends the existing Roebel cable design by adding an additional Roebel shaped layer of strands around the standard cable resulting in the so-called double core (DOCO) cable. By keeping the strands width constant, the cable cross-section will double in width (12 to 24 mm) and increase in thickness by two layers of coated conductors. The favorable properties of the Roebel cable as full strand transposition and excellent bending ability are nearly completely preserved. An enhancement of the current by more than a factor of 2 is achieved. We demonstrate the feasibility of the concept with a 1.3 kA sub-size cable with experiment and modeling. The effects of parallel and crossed orientation of the two cable parts is investigated. The material for a full width DOCO-cable is under development at industrial partners and the status of the efforts for a full size cable will be reported. The future current carrying potential of the DOCO-approach will be discussed on basis of prototypes and the latest improvements of the industrial coated conductors.

Speaker: Dr Wilfried Goldacker (Karlsruhe Institute of Technology)
• 128
Fabrication of long-length cable-in-conduit for superconducting magnets

Cable-in-conduit conductor has particular benefits for superconducting magnets. It is rugged and provides cable-level stress management, it has internal flow of cryogen, flared ends can be formed readily and are self-stable once formed. Fabrication of long-length cable presents several challenges: the center tube must be formed and drawn using perforated strip; the cable must be pulled through a long length of seamless sheath tube and then the sheath must be drawn down to compress the wires against the center tube and immobilize them.
Procedures and practical experience for CIC fabrication will be presented.

Speaker: Jeff Breitschopf (Texas A&M University)
• 129
Feasibility Analysis, Technical Challenges, and Potential Solutions for Cross-country Multi-Terminal Superconducting DC Power Cables

High temperature superconducting (HTS) cables are expected to play an important role in modernizing the electric power grid. Significant increase in the fraction of renewable power generation is forcing the society to rethink the structure of electrical power grid in the US and elsewhere. Multi-gigawatt capacity long distance DC power transmission and interconnection of the three US power grids are becoming essential for full integration of renewable energy sources and to manage the variability in generation capacity of the renewable sources. The most suitable sites for renewable power generation are typically located far from major load centers, requiring a substantial increase in transmission grid capacity and efficiency. HTS conductor manufacturing has matured and expanded with multiple suppliers around the world. Similarly, HTS cable manufacturing technology has been demonstrated with several demonstrations and installations in the power grid. Cross-country superconducting cables offer many benefits, but have several technical challenges that need to be addressed before making it a reality. This paper presents a study that addresses a few of the challenges for long distance DC superconducting cables: (i) high voltage dielectric and thermal designs, (ii) efficient power electronics and protection systems for multi-terminal DC cables, and (iii) costs associated with the technology. The paper discusses the technical challenges, currently available commercial solutions, gaps in technology, and potential solutions for the outstanding challenges.

Speaker: Mr Aws Al-Taie (Florida State University)
• 130
Finite element investigation of the mechanical behavior of Twisted Stacked-Tape Cables exposed to large Lorentz loads

The mechanical response of Twisted Stacked-Tape Cables (TSTC) experiencing large Lorentz loads generated during the operation of high-current, high-field magnets was investigated using finite element analysis. In previous work, the numerical analysis of an untwisted 40-tape TSTC under transverse compression was performed to identify cable configurations able to support the tapes against these loads. Two conductor configurations were originally investigated: a stack of tapes inside a solid cylindrical copper rod and a solder filled copper tube. In this paper, an optimization study is performed for the design of the solder filled tube configuration to define an optimal ratio between the thickness of the copper tube and the amount of solder used. A full scale numerical model of a twisted stacked cable is also analyzed and the results are compared with previous findings for the untwisted configuration. In addition, a study on the stress distribution inside a cable as a function of the tape width is conducted to highlight the advantages and disadvantages of using a wide tape compared to a narrow tape. Finally, based on the findings of the mechanical response of these cable configurations subjected to large Lorentz loads, the critical current performance of the TSTC conductors is discussed.

Speaker: Ms Federica Pierro (Tufts University)
• 131
Influence of Reaction Heat Treatment Conditions on Interstrand Contact Resistances of Nb3Sn Rutherford Cables

For the high luminosity upgrade of the large hadron collider the US accelerator research program is developing the quadrupole magnet MQXF wound with a 40 strand (N = 40) Nb3Sn Rutherford cable QXF. During the field ramping of accelerator magnets interstrand coupling currents flow through the crossover- and adjacent-strand contact resistances represented by Rc and Ra, respectively, and a combination of them by Reff. In order to control Rc during reaction heat treatment (RHT) thin stainless steel cores of specified widths (core cover, W%) are often included in Nb3Sn Rutherford cables. Cables with cores of various widths were prepared and reaction heat treated (RHT) under various conditions. In earlier studies by our group the cables were RHT under face-on uniaxial pressure of 20 MPa and vacuum impregnated with resin under 5 MPa. The close crossover contact produced an uncored average Rc of 0.26 μΩ. But with increasing core width Reff(Rc,Ra) increased rapidly reaching, for example, more than 240 μΩ at W ~ 90%. Reff versus W% results for QXF cable stacks agreed with prediction based on the fortran code CUDI(c) assuming Rc = 0.26 μΩ and 1000 μΩ for the uncored and cored contact, respectively. More recently cable RHT and vacuum impregnation in the absence of mechanical constraint has been recommended; the magnet winding or test cable stack is placed in a closed channel just large enough to contain it during RHT when small known expansions in both width and thickness occur. Reff versus W% results for QXF cable stacks treated in this way are compared with the earlier experimental results and the fortran prediction. It was deduced that crossover contact was absent (Rc essentially infinite) and that Reff which did not vary much with W% depended entirely on Ra (of order 20 nΩ) following the relationship Reff = (N3/20)Ra.

Speaker: Prof. Ted Collings (MSE, OSU)
• 3:00 PM
Afternoon Break (3:00 - 4:00 p.m.) Cryo Expo, Exhibit Hall AB

Cryo Expo, Exhibit Hall AB

Conveners: Ali Hedayat (NASA / MSFC) , Ian McKinley (JPL)
• 132
Cryogenic Testing of the Thermal Vacuum Chamber and Ground Support Equipment for the James Webb Space Telescope in Chamber A at Johnson Space Center

The James Webb Space Telescope (JWST) is the largest cryogenic instrument/telescope to be developed for space flight. The telescope will be passively cooled to < 50 K and the instrument package will be at 40 K with the mid-infrared instrument at 6 K. The final cryogenic test of the Optical Telescope Element (OTE) and Integrated Science Instrument Module (ISIM) as an assembly (OTE + ISIM = OTIS) will be performed in the largest 15 K chamber in the world, Chamber A at Johnson Space Center. The planned duration of this test will be 100 days in the middle of 2017. Needless to say, this ultimate test of OTIS, the cryogenic portion of JWST will be crucial in verifying the end-to-end performance of JWST. A repeat of this test would not only be expensive, but would delay the launch schedule (currently October 2018). Therefore a series of checkouts and verifications of the chamber and ground support equipment were planned and carried out between 2012 and 2016. This paper will provide a top-level summary of those tests, trades in coming up with the test plan, as well as some details of individual issues that were encountered and resolved in the course of testing.

Speaker: Michael DiPirro (NASA/Goddard Space Flight Center)
• 133
The Design and Testing of Large Cryogenic Space Radiators for the James Webb Space Telescope

The James Webb Space Telescope (JWST) is a cryogenic observatory that will provide unprecedented views of our universe. The spacecraft instruments are primarily cooled via passive cryogenic radiators. Ball Aerospace was responsible for designing, building and testing three of these radiators, the Fixed ISIM Radiators (FIR), with the largest designed to dissipate nearly 0.5W at 40K with a radiating area of 4.6m2. This paper will discuss the unique challenges in the design and fabrication of the FIR, and how these challenges were overcome to meet system requirements and deliver radiators with an emissivity of greater than 0.96 at 40K and 95% efficiency. Additionally, this paper will provide details on the thermal balance test design, which includes a large space background simulator with an emissivity of 0.98 at 13K. Testing results will also be provided which verified the performance and capacity of each radiator prior to delivery for integration on the JWST spacecraft.

Speakers: Ryan Taylor (Ball Aerospace) , Eric Marquardt (Ball Aerospace)
• 134
Thermal analysis of a prototype cryogenic polarization modulator for use in a space-borne CMB polarization experiment

We report a thermal analysis of a polarization modulator for use in a space-borne cosmic microwave background (CMB) project. A measurement of the CMB polarization allows us to probe the physics of early universe and currently this is known to be the best candidate to test the cosmic inflation experimentally. One of key instruments to achieve this science is to use a polarization modulator. The polarization modulator unit (PMU) consists of an optical element, called half-wave plate (HWP). The HWP has to rotate continuously at about 1 Hz below 10 K to minimize its own thermal emission to a detector system. A mechanical bearing produces friction, which becomes a source of heat to the cryogenic environment. The continuously rotating HWP system at cryogenic temperature can be realized by using a superconducting magnetic bearing (SMB) without significant heat dissipation.
While the SMB achieves the smooth rotation due to the nature of contactless bearing, estimation of a HWP temperature becomes challenging. We manufactured a one-eighth scale prototype model of PMU. We built a thermal analysis model based on the experimental thermal performance using the scale model and forecasted the projected thermal performance of PMU for a full-scale model based on the thermal model. From this analysis, we discuss the design requirement toward constructing the full-size model for use in a space environment.
This work is a part of study to design and build a PMU for a future CMB satellite mission, such as LiteBIRD.

Speaker: Dr Teruhito Iida (PTI CO., LTD.)
• 135
Zero Boil-Off Control Methods for Large Scale Liquid Hydrogen Tanks using Integrated Refrigeration and Storage

NASA has completed a series of tests at the Kennedy Space Center to demonstrate the capability of using integrated refrigeration and storage (IRAS) to remove energy from a liquid hydrogen (LH2) tank and control the state of the propellant. A primary test objective was the keeping and storing of the liquid in a zero boil-off state, so that the total heat leak entering the tank is removed by a cryogenic refrigerator with an internal heat exchanger. The LH2 is therefore stored and kept with zero losses for an indefinite period of time. The LH2 tank is a horizontal cylindrical geometry with a vacuum-jacketed, multilayer insulation system and a capacity of 125,000 liters. The closed-loop helium refrigeration system was a Linde LR1620 capable of 390W cooling at 20K (without any liquid nitrogen pre-cooling). Three different control methods were used to obtain zero boil-off: temperature control of the helium refrigerant, refrigerator control using the tank pressure sensor, and duty cycling (on/off) of the refrigerator as needed. Summarized are the IRAS design approach, zero boil-off control methods, and results of the series of zero boil-off tests.

Speaker: Bill Notardonato (NASA Kennedy Space Center)
• 136
Liquid Hydrogen Supported Foil Bearings for Launch Vehicle Propellant Densification

Launch vehicle propellants can be densified by an external thermodynamic vent principle operating sub-atmospheric pressure and benefits the space launch industry by reducing vehicle gross liftoff weight (1). However, this principle requires compressors to generate significant head (0.1 bara inlet to 1.1 bara discharge for hydrogen) which can either be achieved by high shaft speed or by multiple compression stages. Traditional propellant densification systems utilize compressors with grease packed ball bearings which limit shaft speed thereby driving the system design toward multiple compression stages and greater complexity while also shortening service intervals. In association with a NASA Small Business Innovative Research (SBIR) initiative to improve this process, Barber-Nichols Inc. (BNI) developed and tested liquid hydrogen lubricated foil bearings in a high-speed hydrogen gas compressor for the production of densified launch vehicle propellants. Foil bearings do not have the same shaft speed limitations allowing the compressor to run faster reducing the number of compression stages and simplifying the propellant densification system. The test results are presented here.

Speaker: Mr Robert Fuller (Barber-Nichols Incorporated)
• 137
Large Scale Production of Densified Hydrogen to the Triple Point and Below

Recent demonstration of advanced liquid hydrogen storage techniques using Integrated Refrigeration and Storage (IRAS) technology at NASA Kennedy Space Center led to the production of large quantities of densified liquid and slush hydrogen in a 125,000 L tank. Production of densified hydrogen was performed at three different liquid levels and LH2 temperatures were measured by twenty silicon diode temperature sensors. System energy balances and solid mass fractions are calculated. Experimental data reveal hydrogen temperatures dropped well below the triple point during testing, and were continuing to trend downward prior to system shutdown. Sub-triple point temperatures were seen to evolve in a time dependent manner along the length of the horizontal, cylindrical vessel. The phenomenon, observed at two fill levels, is detailed and explained herein. The implications of using IRAS for energy storage, propellant densification, and future cryofuel systems are discussed.

Speaker: Adam Swanger (NASA Kennedy Space Center)
• C1OrE - Superconducting RF Systems Madison Ballroom BC

Conveners: Thomas Nicol (FNAL) , Vincent Roger (FNAL)
• 138
Serial testing of XFEL cryomodules: results of the cryogenic heat load measurements

The European X-ray Free Electron Laser (XFEL) is under commissioning at DESY. The superconducting XFEL linac will produce pulsed electron beam with energy of 17.5 GeV. The linac consist of 800 superconducting niobium 1.3 GHz nine cell cavities and 100 superconducting magnet packages assembled in 100 cryomodules. Each cryomodule has 12 m length and includes the 2K helium II bath circuit for the cavities and two radiation shields at temperatures of 5-8K and 40-80K. Before installation in the XFEL linac tunnel all cryomodules were tested in the Accelerator Test Facility (AMTF).We report about methods and results of static and dynamic heat load measurements of all XFEL cryomodules in AMTF and compare with first integral heat load mesurements in the XFEL linac.

Speaker: Dr Bernd Petersen (DESY)
• 139

The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL) is preparing for the Proton Power Upgrade (PPU) project to increase the output energy of the accelerator from 1.0 GeV to 1.3 GeV. As part of this project with the combination of increasing the output energy and beam current, the beam power capability will be doubled from 1.4MW to 2.8MW. In this project, seven new high beta cryomodules housing 28 superconducting niobium cavities will be added to the LINAC tunnel. Lessons learned from over ten years of operation will be incorporated into the new cryomodule and cavity design. The design and the fabrication of these cryomodules and how these will be integrated into the existing accelerator will be detailed in this paper.

Speaker: Matthew Howell (UT Battelle/ORNL)
• 140
LCLS-II 1.3 GHz Cryomodule Design - Lessons Learned from Testing at Fermilab

Fermilab’s 1.3 GHz prototype cryomodule for the Linac Coherent Light Source Upgrade (LCLS-II) has been tested at Fermilab’s Cryomodule Test Facility (CMTF). Aspects of the cryomodule design have been studied and tested. The cooldown circuit was used to quickly cool the cavities through the transition temperature, and a heater on the circuit was used to heat incoming helium for warmup. Due to the 0.5% slope of the cryomodule, the liquid level is not constant along the length of the cryomodule. This slope as well as the pressure profile caused liquid level management to be a challenge. The microphonics levels in the cryomodule were studied and efforts were made to reduce them throughout testing. Some of the design approaches and studies performed on these aspects will be presented.

Speaker: Joshua Kaluzny (Fermilab)
• 141
Operational Experience from LCLS-II Cryomodule Testing

This paper describes the initial operational experience gained from testing Linac Coherent Light Source II (LCLS-II) cryomodules at Fermilab’s Cryomodule Test Facility (CMTF). Strategies for a controlled slow cooldown to 100K and a fast cooldown past the niobium superconducting transition temperature of 9.2K will be described. The test stand for the cryomodules at CMTF is sloped to match gradient in the LCLSII tunnel at Stanford Linear Accelerator (SLAC) laboratory, which adds an additional challenge to stable liquid level control. Control valve regulation, Radio-Frequency (RF) power compensation, and other methods of stabilizing liquid level and pressure in cryomodule 2.0 K SRF cavity circuit will be discussed. Several different pumping configurations using cold compressors and warm vacuum pumps have used on the cryomodule 2.0 K return line and the associated results will be described.

Speaker: Mr Benjamin Hansen (Fermilab)
• 142
Effects of Thermal Acoustic Oscillations On LCLS-II Cryomodule Testing

Thermoacoustic Oscillations (TAOs) are a well known phenomenon in cryogenics and in most cases is an undesirable effect. During LCLS-II prototype Cryomodule testing, TAOs were observed in both the Cryogenics Distribution System and in the LCLS-II Cryomodule JT and Cooldown Valves. The TAOs manifested themselves through the usual effect of added heat load to the cryogenic system and ice formation on the oscillating device. However, during cavity testing, the TAOs were also found to negatively affect microphonics detuning of the SRF cavities. Systematic studies were carried out and it was discovered that the TAOs could be "turned off" or substantially decreased by operating at subcritical pressures on the supply. Lastly, various dampening techniques were employed to allow operations at supercritical pressure with improved microphonics and reduced heat load.

Speaker: Mr Benjamin Hansen (Fermilab)
• C1OrF - Gas Mixture Properties and Behavior Hall of Ideas - GJ

Hall of Ideas - GJ

Conveners: Mr Peter Bradley (NIST) , Prof. Sangkwon Jeong (KAIST)
• 143
Experimental Effervescence Measurements of Nitrogen in Liquid Methane-Ethane Mixtures to Support an Extraterrestrial Submarine for Titan

NASA is designing an unmanned submarine to explore the depths of the hydrocarbon-rich seas on Saturn’s moon Titan. Data from Cassini Huygens indicates that the Titan polar environment sustains stable seas of variable concentrations of ethane, methane, and nitrogen, with a surface temperature around 93 K. The submarine must operate autonomously, study atmosphere/sea exchange, interact with the seabed, hover at the surface and at any depth within the lake, and be capable of tolerating different concentration levels of hydrocarbons. One of the major challenges with the thermal portion of the design is predicting the degree of nitrogen gas effervescence within the multicomponent sea (due to heat from the submarine) and the impact of nitrogen gas bubbles on science instruments, ballast systems, and submarine propellers. Effervescence measurements on various liquid methane-ethane compositions with dissolved gaseous nitrogen are presented from 20 psi to 80 psi at temperatures from 92 K to 96 K to simulate the conditions of the seas. These experimental effervescence measurements will be used to update the current design the Titan Submarine.

Speaker: Ian Richardson (Washington State University)
• 144
Low Temperature Binary Gas Mixtures

Application of partial pressure technology to combinations of one gas above its critical temperature (helium) mixed with a two-phase liquid (nitrogen) can result in liquid temperatures down to and below the nitrogen triple point. The thermodynamics of this process is developed and an experimental apparatus is described which was used to produce a helium/nitrogen bath temperature of 59.17 K, 4 K lower than the 63.2 K nitrogen triple point and lower than any liquid nitrogen temperature reported in the literature.

Speaker: Dr Glen McIntosh (McIntosh Cryogenics LLC)
• 145
Application of the Langmuir Probe Plasma Diagnostics into the Investigation of the Dielectric Properties of Cryogenic Gas Mixtures

In this study, we use the Langmuir probe plasma diagnostics technique to investigate the dielectric properties of gas mixtures for cryogenic applications. In our previous studies we reported substantial enhancement in the dielectric strength of gaseous helium by adding small mole fractions of gaseous hydrogen. We performed the Boltzmann analysis to predict the dielectric strengths of several helium-hydrogen gas mixtures and validated the theoretical results by breakdown measurements conducted at 77 K and pressures up to 2 MPa. The present study uses the Langmuir probe, a well-known plasma diagnostics method, to obtain basic plasma characteristic parameters that represent the dielectric properties of gas media. The coefficients of electron kinetic processes such as the ionization and attachment coefficients are derived based on the measured electron energy distribution function and the electron scattering cross sections of helium and hydrogen. This paper presents the details of the Langmuir probe plasma measurements, the derivation of the ionization and attachment coefficients, and the comparison between the results of the Langmuir probe method and those of our previous studies.

Speaker: Chanyeop Park (Georgia Institute of Technology)
• 146
The Dielectric Strength of Cryogenic Gas Mixtures for Various Sections in Shipboard Cryogenic Power Systems

This study investigates the dielectric strength of cryogenic gas mixtures containing helium, hydrogen, and nitrogen under the operating conditions of a continuous cryogenic cooling loop for shipboard power systems. Substantial enhancement in the dielectric strength of gaseous helium, a relatively weak dielectric medium compared to liquid nitrogen, the standard cooling medium for high temperature superconducting devices, has been achieved by adding various mole fractions of gaseous hydrogen and nitrogen as reported in our previous studies [1—3]. The continuous cryogenic cooling loop for shipboard power systems consists of several sections including those of power generation, power distribution, and power conversion, each operating at its optimum operating temperature. In the present study, we extend our investigations to the various cryogenic operating conditions of each section in the continuous cryogenic cooling loop. This work includes the estimation of the dielectric strengths of the cryogenic gas mixtures and maps the feasible mixtures of helium, hydrogen, and nitrogen gases with the goal of identifying those with highest dielectric strength. We conduct the Boltzmann analysis to estimate the dielectric strength of the gas mixtures in terms of the electron energy distribution function and the coefficients of electron kinetic processes. The chemical phase equilibrium is solved in this study to map the mole fractions of helium-hydrogen-nitrogen gas mixtures, which can serve as a cooling and dielectric media without condensing the hydrogen or nitrogen in the mixture. The study results serve as a practical guideline for the dielectric design of gas-cooled shipboard cryogenic systems containing superconducting power devices.

Speaker: Chanyeop Park (Georgia Institute of Technology)
• 147
Experimental Studies on the Cryogenic Dielectric Properties of Gas Mixtures for Superconducting Power Applications

Prototypes of gaseous helium cooled High Temperature Superconducting (HTS) power cables and other high power density devices have been demonstrated. Additional superconducting power applications cooled with closed loop helium circulation are being explored either to exploit the higher power density of HTS cables at low temperatures (< 77 K) or to utilize superconducting materials such as MgB2 with lower Tc values. One of the challenges posed by gaseous helium is its low dielectric strength. We have reported significant enhancement of dielectric strength of gaseous helium when 4 mol% of hydrogen gas added [1,2]. We have extended this work with systematic studies on the effect of hydrogen mol% on the dielectric strength in an attempt to optimize the gas mixture that will further enhance the dielectric properties without causing safety concerns of the flammability. Studies have also been undertaken on tertiary gas mixtures containing hydrogen, helium, and nitrogen. Theoretical modelling of the tertiary mixtures predicts a significantly higher dielectric strength than pure helium. Details of the experiments, results of the variation of dielectric strength of the binary and tertiary mixtures compared to pure helium gas are presented.
The work is funded by the Office of Naval Research.

Speaker: Peter Cheetham (Center for Advanced Power Systems)
• 148
Cryogenic Thermal Conductivity of Gaseous Helium mixtures with Neon and Hydrogen at High Pressures

Many high temperature superconducting (HTS) power devices have been successfully demonstrated in the power grid. Most of the HTS devices are cooled using liquid nitrogen as the cryogen. Gaseous helium is being explored as a viable option for cooling HTS power devices where higher power density is required making the operation at temperatures less than 65 K is necessary. Helium gas is versatile in terms of the operating temperature of HTS systems. However, challenges in using helium gas as a cryogen exist due its weak dielectric strength and volumetric low heat capacity compared to that of liquid nitrogen. Gaseous helium mixed with small mole fractions of hydrogen has been shown to have enhanced dielectric strength. To be an effective cryogenic medium for HTS power systems with required cooling power, gaseous helium systems typically operate at pressure of over 1 MPa. When considering to use helium gas mixtures, it is essential that the additives such as hydrogen for helium gas need to preserve the thermal characteristics of pure helium gas. Thermal conductivity of high pressure gas mixtures at cryogenic temperatures is not available and is not easy to estimate using mixing theory. In this study, cryogenic thermal conductivity was measured experimentally for pure helium gas and helium gas mixtures containing up to 4 % volume fraction of hydrogen at 77 K and pressures higher than 1 MPa. These thermal properties would be useful for identifying a gas mixture with optimal dielectric and thermal characteristics essential for using the mixtures as cooling media for HTS power applications. Results of the experimental studies on thermal characteristics of gaseous helium mixtures are presented and their implication in gas cooled HTS applications is discussed.

Speaker: Dr Jin-geun Kim (Center for Advanced Power Systems)
• 149
Transient model of carbon dioxide desublimation from nitrogen

A transient model for a cryogenic carbon dioxide capture (CCC) pump is presented. The pump separates carbon dioxide by desublimation from nitrogen in the gas mixture exhaust from power plants. Compared with other CCC methods, desublimation is commonly considered to be competitive when the concentration of carbon dioxide is low. It is necessary to explore the fully detailed physical mechanisms associated with the flow as well as mass and energy conservation. The pump is modeled as a tube-in-tube counter-flow heat exchanger including four control volumes, the nitrogen (or helium) coolant, the wall, the solid carbon dioxide layer and the mixture. The main task of the model is to study the speed and location of deposition and the capacity of the pump based on thermodynamics combined with numerical analysis. In order to verify the model, deposition processes under various pump conditions are simulated and the simulation results are compared with corresponding calculations that do not consider the solid carbon dioxide layer and with experiment data. The results demonstrate an improved accuracy by taking the solid layer into consideration. The model captures a variety of deposition parameters, and gives primary attention to the role of the frost deposition rate. The analysis approach also provides generic value to other systems with a gas-solid phase change.

Speaker: Ms Yaning Wang (Zhejiang University)
• C1OrG - Pulse Tube Components Hall of Ideas - FI

Hall of Ideas - FI

Conveners: Jeff Olson (University of Wisconsin Eau Claire) , Philip Spoor (Chart Industries)
• 150
Influence of Minor Geometric Imperfections on Stirling Pulse Tube Cryocooler

Minor geometric features and imperfections are commonly introduced into the basic design of multi-component systems in order to simplify or reduce the expense of manufacturing. In this work, detailed 3D Computational Fluid Dynamic (CFD) models were used to investigate the impact of such apparently minor geometric imperfections on the performance of Stirling type pulse tube cryocoolers. A series of CFD simulations based on a prototypical cold tip was carried out. Temperature and velocity distributions in perfect and imperfect geometries were compared and analyzed. Predictions of cooling performance and gravity orientation sensitivity were compared with experimental results obtained with cryocooler prototypes. The results indicate that minor geometry imperfections in cold tip assembly can have considerable negative effects on the gravity orientation sensitivity of pulse tube cryocooler.

Speaker: Tao Fang (Georgia Institute of Technology)
• 151
Miniature PT Cryocooler Activated by Resonant Piezoelectric Compressor and Passive Warm Expander

A novel type of PZT-based compressor operating at mechanical resonance, suitable for pneumatically-driven Stirling-type cryocoolers, was presented at CEC-ICMC 2015. The detailed concept, analytical model and the test results on the preliminary prototype were reported earlier and presented at ICC17. Despite some mismatch between the impedances and insufficient structural stiffness, this compressor demonstrated the feasibility to drive our miniature Pulse Tube cryocooler MTSa, operating at 103 Hz and requiring an average PV power of 11 W, filling pressure of 40 Bar and a pressure ratio of 1.3.
At ICC19 the prototype of a miniature passive warm expander (WE) was presented. The WE mechanism included a phase shifting piston suspended on a silicone diaphragm, a mass element, and a viscous damping system. Several technical drawbacks prevented perfect matching between the WE and MTSa; however, the presented prototype proved the ability to create any flow-to-pressure phase appropriate for a PT cryocooler.
This paper concentrates on integration of the MTSa cryocooler with the recently modified PZT compressor operating at corrected mechanical resonance and the modified WE, which was also updated recently to match the MTSa requirements.

Speaker: Mr Sergey Sobol (Technion - Israel Institute of Technology)
• 152
Study on the flow nonuniformity in a high capacity Stirling pulse tube cryocooler

High capacity Stirling-type pulse tube cryocooler (PTC) has promising application in high temperature superconductor cooling and gas liquefaction. However, with the increase of cooling capacity, its performance deviates much from that simulation by well-accepted one-dimensional model, such as Sage and Regen, mainly due to the strong field nonuniformity. In this study, several flow straighteners placed at both ends of the pulse tube are investigated in order to improve the flow distribution. A two-dimensional model of the pulse tube based on the computational fluid dynamic method has been built to study the expansion efficiency of the pulse tube under different flow straighteners including stainless steel screens, copper screens, taper transition and taper copper slots. The gas temperature, flow and pressure distributions are compared and analyzed. A PTC set-up which has more than one hundred watts cooling power at 80 K has been built and tested. The flow straighteners mentioned above have been applied and tested. The results showed that with the best flow straightener, the cooling performance of the PTC can be significantly improved. Both CFD simulation and experiment show that the straighteners have much great impacts on the flow distribution and the performance of the high capacity PTC.

Speaker: Mr Xiaokuan You (Institution of Refrigeration and Cryogenics, Zhejiang University)
• 153
Investigation on characteristics of inertance tube at different operating frequencies: coiled type and material

An inertance tube is widely used to provide appropriate impedance at the warm end of the pulse tube in pulse tube refrigerator (PTR). The inertance tube is usually coiled around the outer surface of a linear compressor or in a reservoir to reduce installation space, which affect the cooling performance. The materials of the inertance tube would also influence the pressure drop of the helium gas within inertance tube and change the phase angle between pressure and mass flow. The influences are dependent on the operating frequencies. A numerical model is built to simulate the cooling performance of the PTR with different coiled types and materials (copper and stainless steel) operating at different frequencies. The results show that the phase shift ability of the inertance tube would decrease while increasing the number of coiling turns, which cause more PV power for the same cooling capacity. More PV power would also consume while change the material of the inertance tube from stainless steel to copper. The differences will be weakened while increasing the operating frequency. The results provide a new perspective that why the inertance tube can have better applications under higher frequency. Experiments are performed to verify the simulation results.

Speaker: Dr Shaoshuai Liu (Shanghai Institute of Technical Physics of Chinese Academy of Science)
• 154
Study on a three-stage cascade pulse tube cryocooler

By using a well-designed transmission tube to recover the dissipated acoustic power at the hot end of the former PTC, the efficiency of the multi-stage cascade PTC is capable to approach Carnot efficiency. Based on this theory, a third pulse tube cryocooler (PTC) was connected in series with the existing two-stage cascade PTC. Experiments showed that the cooling power of the three-stage cascade PTC was 253.6 W @233 K, which was improved by 39.9% compared with that of the single-stage PTC. This moved the PTC efficiency forward one more step to approach Carnot efficiency.

Speaker: Mr Qinyu Zhao
• 155
Numerical and experimental study of an annular pulse tube used in the pulse tube cooler

Multi-stage pulse tube cooler normally uses U-type configuration. For compactness, it is attractive to build a completely co-axial multi-stage pulse tube cooler. In this way, annular shape pulse tube is inevitable. Although there are a few reports about annular pulse tube used in a cooler system, a detailed study and comparison with a circular pulse tube is lacking. In this paper, a numeric model based on CFD software is firstly carried out to compare the annular pulse tube and circular pulse tube used in a single stage in-line type pulse tube cooler with about 10 W cooling power at 77 K. The length and cross sectional area of the two pulse tubes are kept the same. The simulation results show that enthalpy flow in annular pulse tube is lower by 1.6 W (about 11% of the enthalpy flow) than that in circular pulse tube. Flow and temperature distribution characteristics are also analyzed in detail. Experiments are then conducted for comparison on an in-line type pulse tube cooler. With the same acoustic power input, the pulse tube cooler with a circular pulse tube obtains 7.88 W cooling power at 77 K, while using annular pulse tube leads to a cooling power of 7.01 W, a decrease of 0.9 W (11.4%) on the cooling performance. The study sets the basis for building a completely co-axial two-stage pulse tube cooler.

Speaker: Xiaomin Pang (Key Laboratory of Cryogenics, Chinese Academy of Sciences)
• 156
Displacer Diameter Effect in Displacer Pulse Tube Refrigerator

With the development of the pulse tube refrigerator, the efficiency increasing meets a technology neck with traditional phase shifter such as double inlet or inertance tube. A displacer as phase shifter is one method to overcome this problem. The displacer with a rod is the ideal phase shifter till now, the phase adjustment is free, and the stroke can be controlled by the rod diameter. Unlike Stirling refrigerator in which the diameter of the displacer is limited by the diameter of the cold finger, the diameter of the displacer in the displacer pulse tube refrigerator is free for design. The diameter effect of the displacer is investigated by numerical simulation, which shows that the diameter of the displacer with optimum displacer rod diameter has no big influence to the efficiency and cooling power while the stroke decreasing with the increasing of the displacer diameter. The regenerator length effect to the displacer is also investigated, too

Speaker: Prof. Shaowei Zhu (Institute of Refrigeration and Cryogenics, School of Mechanical Engineering, Tongji University)
• M1OrE - Focused Symposia - Propulsion IV: Power Electronics, Energy Lecture Hall

Lecture Hall

Conveners: David Cardwell (University of Cambridge) , Eric Hellstrom (ASC / NHMFL / FSU)
• 157
[Invited] Cryogenically Cooled 1-MW Inverter

We describe the general design and development progress of a cryogenically cooled 1-MW inverter. The goal is to achieve an efficiency of 99.3% at 500-kW power and a specific power of 26 kW/kg. The design must be compatible and scalable with cooling by both liquid hydrogen and liquid natural gas, but the experimental prototype will be cooled by liquid nitrogen. The input dc voltage is 1000 V, and the output frequency is 200-3000 Hz. The inverter requires sufficient filters to meet DO-160 EMI standard, and both conventional and superconducting inductors were evaluated for this purpose. The candidate commercial off-the-shelf power semiconductors were characterized from 77 K to room temperature for on-state resistance, breakdown voltage, and switching energy loss. The inverter design uses a three-level active neutral-point clamped topology that uses different power switches for the fast and slow switching. A calorimeter was developed that can measure the efficiency of the 200-kW and 1-MW prototypes by the dissipated losses to the liquid nitrogen to better than 0.1% of the total power. Phase I of the project is complete, with a design that meets the project goals. Phase II of the design is ongoing with fabrication of a 200-kW inverter to reduce the risk of key design elements. Phase III of the project will be construction and test of the 1-MW inverter.

This project was partially funded by NASA AATT under Contract No. NNC15AA01A.

Speaker: John Hull (Boeing Research & Technology)
• 158
A Review of Cryogenic Power Electronics Progress

Cryogenic Power Electronics, or CryoPower, has been proposed as an innovation for over two decades as a means of integrating power electronics and superconducting devices, particularly magnets, motors, and generators at cryogenic temperatures close to the operational temperature of superconductors. In these systems, power electronics specifically designed to operate in the cryogenic environment are installed in cryostats and in close proximity to superconducting devices. Among the benefits of cryogenic operation of semiconductors are reduced conduction losses, increased switching times, higher power density (reduced size and weight), and reduced system-level losses. Potential applications include wind turbines, maglev, all-electric aircraft and ships, utility-scale energy storage and transmission and distribution, and power systems for advanced computers, all of which may benefit from superconductivity in one form or another. Much progress has been made recently in scaling prototypes to commercial power levels.

To make CryoPower attractive, a large number of ancillary hardware and electronic components qualified for cryogenic operation is required. Most electronic components are not qualified to operate over an extreme temperature range. Consequently, difficult choices must be made and extensive testing is required to meet the demands of even a simple circuit. In addition, testing of circuits and sub-circuits often requires several cooling cycles, which must be done in a controlled fashion. As a consequence, development is much slower and more tedious than for room temperature circuits. However, this is a necessary process because of the critical reliability demands of power networks.

MTECH will summarize its most recent progress in developing fully integrated CryoPower systems, including development of a Superconducting Magnetic Energy Storage (SMES) system.

Speaker: Dr Michael Hennessy (MTECH Laboratories, LLC)
• 159
Experimental Characterization of Gallium-Nitride Field-Effect Transistors at Cryogenic Temperatures and Application in Multilevel Inverter

GaN-based field-effect transistors have shown great potential in the development of high-density power converters and also hold promise for cryogenic applications. In order to explore this potential, the cryogenic performance of an EPC gallium-nitride (GaN) power field-effect transistors (FETs) has been evaluated. At -195 C, an 85 % reduction in on-state resistance, and a 16 % increase in threshold voltage were experimentally measured without observing carrier freeze-out effects. Moreover, using a double-pulse test, no major changes in switching characteristics were noted.

Building on these results, a 1 kW, GaN-based, 3-level power converter was designed and successfully tested from room temperature down to -140 C, using a custom milled cold-plate. At -60 C, a 16% reduction in losses was achieved at rated power. An estimated power loss breakdown was performed by taking into account the decreasing conduction losses of the GaN FETs and estimates of losses for the passive components. It is clear that there is significant opportunity for additional gains in efficiency by combining high-performing GaN FETs with passive components optimized for low temperature operation. This work is the first demonstration of a flying capacitor multi-level converter and associated components at such low temperature, and highlights opportunity for further gains in density and efficiency in liquefied natural gas applications which offer readily available low temperature cooling.

Speaker: Mr Christopher Barth (University of Illinois at Urbana Champaign)
• 160
Development of high-temperature superconducting CORC® power transmission cable systems

Next generation electric power systems on Navy ships require higher capacity, efficiency, and stability to meet the demands of increasingly complicated grid systems. High-temperature superconducting (HTS) Conductor on Round Core (CORC®) power transmission cables provide unique solutions by offering high operating currents and current densities in a very small cable cross-section. Advanced Conductor Technologies is developing 2-pole dc and 3-phase ac power transmission cables, cable terminations and connectors to be cooled with pressurized cryogenic helium gas for shipboard use. The development and initial test results of 2-pole dc CORC® power transmission cables, rated at 4,000 A per phase, will be discussed. The development is not limited to only the power transmission cables, but also includes CORC® feeder cables that form the connection between the room temperature bus bar and the CORC® power transmission cable located inside the helium gas environment. Methods to significantly increase the current rating to exceed 10 kA per phase, and current densities of over 500 A/mm2 will be discussed. Efforts are underway to develop advanced dielectrics that are sealed against helium gas penetration, to enable operation of superconducting power transmission cables at a voltage in the order of 10 kV or above, resulting in a cable power rating of 10-100 MW.

Speaker: Danko van der Laan (Advanced Conductor Technologies)
• 161
[Invited] Application of SMES for Hybrid-electric Power Systems

As desired for a sustainable economy, efficient renewable energy generation, conversion, distribution, and storage technologies are indispensable to meet society’s increased need in energy utilization. Propulsion is one of the major functions the modern society needs, and electric-propulsion, rather than internal combustion based propulsion, will be a key player to help reach the goal of sustainability by directly linking the renewable energy sources to energy applications.

Unlike other energy storage means available, electricity storage in the form of electric current provides potential advantages of high performance, high conversion efficiency, and unique capability to meet high demand in power output in energy applications. Superconductivity at reasonable cryogenic temperatures will provide the foundation to develop energy related technologies.

This presentation will briefly overview some current effort in developing SMES as a means of energy storage that can be applicable in areas of hybrid-electric propulsion, power conditioning for a microgrids, and pulsed power source development for special energy applications. An example will be given for a first generation of HTS solenoid magnet design, fabrication, and test as an integrated SMES system.

Speaker: Dr Charles Rong (U.S. Army Research Laboratory)
• 162
[Invited] Development of High Energy Density Superconducting-Magnetic-Energy-Storage (SMES) for Aerospace Electric Propulsion

Electrical energy storage devices are critical components of electric power systems of every aerospace vehicle. They are needed for many functions, such as to provide high-power for pulsed loads, as an electrical accumulator unit (EAU) to handle transient loads both on/off the buses, for emergency power during generator or hydraulic-system failure, and as a high-capacity energy source for hybrid-electric-vehicle (HEV) or electric-vehicle (EV) propulsion. Hybrid-electric propulsion for airborne vehicles is understood to provide significant energy efficiency benefits, including during taxiing, for climb, cruise and descent phases, and regenerative (regen) power during descent which has been successfully demonstrated. As electric propulsion of aircraft progresses to 1-10 MW expected in the next 5-10 years, SMES is considered one of the few technology options that can provide high power capability particularly for fast charging, with reasonable weights. SMES along with supercapacitors are the only two technologies able to provide pulsed power for railgun applications, and to handle MW-class transient pulse loads such as high-energy-laser (HEL) shots or absorb high-power-system-faults.
Superconducting-magnetic-energy-storage (SMES) devices offer attractive and unique features for airborne vehicles including the highest power densities known achievable for any technology of 10-1000+ kW/kg for both charge and discharge, 100% storage efficiencies for unlimited times, and for some designs virtually no degradation for up to 10^8 charge/discharge cycles. 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. This paper will describe about the functions of SMES for aerospace electric propulsion, and provide a recent update on the development and performance of SMES devices being designed and built. 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.

Speaker: Timothy Haugan (U.S. Air Force Research Laboratory)
• M1OrF - Focused Session: Pushing Nb3Sn Conductors Beyond the State of the Art Hall of Ideas - EH

Hall of Ideas - EH

Conveners: Peter Lee (NHMFL / FSU / ASC) , Xingchen Xu (FNAL)
• 163
[Invited] Pinning Landscape Enhancement by Means of Irradiation

Over the past couple of years we have carried out the thus far most extensive neutron irradiation study on Nb3Sn. Samples of five types of state-of-the-art multifilamentary wires as well as high-purity polycrystals were exposed to sequential fast neutron irradiation in the TRIGA Mark-II reactor in Vienna. Irradiation induced changes in the superconducting properties were assessed by means of magnetometry and transport measurements, and transmission electron microscopy was used to examine the defect structure resulting from the particle bombardment. We found a large increase in the volume pinning force up to very high neutron fluences, which can be described using a two-component pinning force model. Within this model irradiation induced defects are treated as point-like pinning centers, which enhance the original grain boundary pinning landscape. We put our results into context with other irradiation studies, and argue that the concept of pinning landscape enhancement through nano-scale defects should be transferrable to an industrial production process.

Speaker: Dr Michael Eisterer (Atominstitut, Vienna University of Technology)
• 164
[Invited] Prospects for further improving Jc of Nb3Sn conductors

The record Jc of Nb3Sn conductors has plateaued since the early 2000s; however, new target has been put forward for the planned future circular colliders. This presentation aims to discuss prospects for further improvement of Nb3Sn conductors. The factors determining the non-Cu Jc are summarized, which include current-carrying Nb3Sn fraction in subelements, Nb3Sn Bc2, and pinning capacity; then prospects to improve each factor are analyzed respectively. A model is introduced for phase fractions in subelements; the limit of current-carrying Nb3Sn fraction in subelements is obtained based on this model. A model is also proposed to explore what determines Nb3Sn phase stoichiometry during diffusion reaction. It is seen that among all the possible means, the only opportunity for significantly improving non-Cu Jc relative to the present record values lies in improving pinning. To improve pinning, a comprehensive review of an internal oxidation technique is given in this talk, including its opportunities, challenges, and its applications in major types of Nb3Sn wires (PIT, RRP, and single-barrier wires). Recent progress in optimizing this method for further improving the performance of Nb3Sn conductors is also reported.

Speaker: Xingchen Xu (Fermi National Accelerator Lab)
• 165
Reexamining the heat treatment of RRP® Nb3Sn and the potential for further improvements

The heat treatment of internal tin Nb3Sn wires has historically used multiple low temperature stages designed to mix the Cu and Sn as to minimize liquid contact with the Nb filaments, to inhibit Kirkendall void formation, or to increase the Sn concentration surrounding the Nb filaments prior to the A15 reaction. Our recent studies have shown that the unique geometry of high-Jc RRP® wires, where Nb filaments in a Cu matrix are densely packed around the Sn core, benefits from a very different approach to optimization. In such wires the low Cu:Sn ratio requires the Cu-Sn mixing to occur within the sub element cores. This is facilitated by the early formation of a membrane-like ring of the Sn Nb Cu ternary phase Nausite around the core that allows Cu diffusion from within the filaments into the Sn-rich core, while inhibiting Sn diffusion into the filament pack. Although beneficial as a membrane, the growth of this layer must be controlled as it ultimately decomposes to a disconnected A15 phase. Extensive quantitative image analysis has allowed us to show the relationship between heat treatment temperature and time, the net Cu inward diffusion and the Nausite ring thickness, allowing us to develop optimized low temperature heat treatments that balance the amount of low melting point Cu-Sn with the amount of Sn and Nb lost to Nausite formation. We show that this new heat treatment strategy can significantly increase the Jc of RRP® strands, especially for small diameter sub-elements.

Speaker: Charlie Sanabria (NHMFL)
• 166
RRP® Nb3Sn Wire Optimization with Bruker-OST

For cost-effective 15-16 T accelerator magnets, the critical current density Jc(15T,4.2K) of commercial Nb3Sn composite wires has to be pushed from the present state-of-the-art for RRP® wires of ~1,650 A/mm2 to ~2,000 A/mm2. Only so much improvement can be obtained through heat treatment optimization. Wire development was therefore carried out in collaboration with Oxford Instruments - Superconducting Technology (OST), which produced three R&D billets to optimize design and layout parameters of their trademarked RRP® process. These wires were studied and characterized virgin and deformed to at a number of sizes through flat-rolling process. The virgin OST 169-restack conductor within this study had an average Jc(4.2K, 16T) ~ 1,300 A/mm2 and its cost was ~$1,700/kg. This was obtained with a Nb to Sn ratio of 3.4:1, which corresponds to ~53%at. Nb, which is presently the achievable upper limit for Nb content in a wire. Results indicate that the Jc of Nb3Sn wires has plateaued. It is clear that to achieve the cost reduction required in magnets for a Hadron Collider, the target increase in Jc can only be achieved by disruptive progress, and that for this reason it is now necessary to invest in research aimed at improving the inherent flux pinning of Nb3Sn. Speaker: Emanuela Barzi (Fermilab) • 167 The development of high pinning site densities in multifilamentary PIT wires using the internal oxidation route Prior to his passing in late 2016, Leszek Motowidlo developed a method of applying the Nb-1Zr/SnO2 internal oxidation method to APC Nb3Sn through a powder-in-tube (PIT) approach that used low-cost Cu5Sn4 powder as the Sn source. Two designs of multifilamentary PIT wire were successfully produced and fine-grain A15 layers with average grain diameters as small as 30 nm were obtained. High resolution field emission SEM also indicated the presence of point pinning sites, particularly at grain boundaries. Magnetization and transport critical current tests showed a shift in the peak of the pinning force curve toward higher magnetic field. Deconvolution of the pinning force curves indicated a strong point pinning component, perhaps produced by the ZrO2 precipitates. It was found that the degree of microstructural refinement was very sensitive to the volume percent of SnO2 in the core. This presentation will also look at some limitations of this technique, which included a strong gradient in grain size, uneven distributions of point-pinning sites and relatively low levels of conversion of Nb6Sn5 to Nb3Sn. Such compromises will need to be addressed to make this approach competitive with more fully developed conventional internal Sn and PIT Nb3Sn wires. Support The work is funded by the High Energy Physics division of the US Department of Energy under a Phase I SBIR award DE-SC0009605. A portion of this work was performed at the National High Magnetic Field Laboratory, which is supported by National Science Foundation Cooperative Agreement No. DMR-1157490 and the State of Florida. Speaker: Peter Lee (Florida State University) • 168 Novel Methods for Improving Nb$_3$Sn Powder in Tube Conductors for the FCC and Beyond The relatively low cost of multifilamentary Nb$_3$Sn strand compared to HTS alternatives makes it highly valuable to magnet builders to improve the critical current densities (J$_c$) beyond the current production limits of ~ 3 kA/mm$^2$(12 T,4.2 K) available today. Future applications such as the proposed Future Circular Collider demand increased J$_c$at higher fields (≥16 T) that current heat treatments have not been optimized for. The two commercially developed high J$_c$Nb$_3$Sn strands, Powder In Tube (PIT) method, and Rod Restack Process, can be improved primarily in four ways; increase the fine-grain A15 area, increase T$_c$and H$_{c2}$homogeneity within the A15 volume, reduce A15 grain size to increase grain boundary pinning density, or introduce point pinning which favorably shifts the maximum pinning force to higher fields. Ideally, any method which accomplishes this should be utilized within the existing manufacturing processes to prevent long or costly R&D projects or impacting yield. Thus optimizing the heat treatment to reduce grain size, while increasing the volume of fine-grain A15 and increasing the H$_{c2}$homogeneity would be the most desirable route, however, higher temperature heat treatments that better favor H$_{c2}$also increase the grain size and thus the benefit of improving H$_{c2}$is offset by fewer pinning sites. In conventional PIT strands, however, 30% of the superconducting A15 phase volume is large-grain (LG) A15, which does not contribute to transport current, and converting this volume to fine grain A15 would be highly beneficial. The LG A15 has proven historically difficult to avoid or control, however, in the past 5 years we have been able to identify the origin of the LG A15 morphology in PIT wires and have demonstrated heat treatments that control its nucleation and growth. Here we summarize our progress in improving the high field J$_c$of Nb$_3\$Sn PIT conductors.

Speaker: Chris Segal (National High Magnetic Field Laboratory)
• 6:00 PM
Exhibitor Reception (6:00 - 7:30 p.m.) Cryo Expo, Exhibit Hall AB

Cryo Expo, Exhibit Hall AB

• Tuesday, July 11
• 7:50 AM
Cryo Expo Open (9:00 - 5:00) Exhibit Hall AB

Exhibit Hall AB

For a list of Exhibitors, please visit: http://www.cec-icmc.org/exhibit/exhibitors/.

• CEC Awards (7:55 - 8:15 a.m.) Madison Ballroom

• Tuesday Plenary (8:15 - 9:00 a.m.) - Richard Riley, Highview Power Storage Madison Ballroom

Conveners: Eric Marquardt (Ball Aerospace) , Jennifer Marquardt (Ball Aerospace)
• 169
Liquid Air Energy Storage: How cryogenics can support a greener grid.

The drive for a greener grid is seeing baseload power generation increasingly displaced by intermittent renewables, forcing a change in how grid operators manage their networks. Energy Storage is a key component of the strategy to maintain a stable and reliable supply of electricity, shifting "wrong-time" energy and providing ancillary services from clean sources.

The bulk storage of energy represents a particular challenge. Even with recent cost reductions in battery technologies their costs are high, and the incumbent technologies used for large-scale storage are constrained by geographical requirements.

Liquid Air Energy Storage is based on components proven through decades of use in the Industrial Gas, Oil & Gas and Power Generation sectors and provides a low-cost solution for bulk-scale storage that is ready to be deployed today and can be located where the value is greatest.

Speaker: Richard Riley (Highview Power Storage)
• C2PoA - Thermal Insulation Systems I Exhibit Hall AB

Exhibit Hall AB

Conveners: James Fesmire (NASA / KSC) , Jennifer Marquardt (Ball)
• 170
Computational Fluid Dynamics Model of a 3D Printed Liquid Hydrogen Tank with Vapor Cooled Shielding for Use in Unmanned Aerial Vehicles

Lightweight engineering polymers and additive manufacturing have enabled development of a new cryogenic liquid storage paradigm. State of the art cryogenic storage dewars typically conform to a vacuum jacketed thin wall stainless steel vessel with multi-layer insulation design. While resulting in low boil-off rates, the specific energy is often insufficient for use in weight sensitive aerospace applications. Using 3D printed polymers can increase the specific energy of the tank system by reducing the mass of structural components while matching the boil-off rate to that of the nominal flow demand from a fuel cell. This study investigates the performance of vapor cooled shielding using boil off vapors in a 3D printed polymer liquid hydrogen storage tank using experimental data from a prototype tank. COMSOL computational fluid dynamics is used to model the transient thermal performance during a liquid hydrogen fill and steady state boil-off with liquid nitrogen and liquid hydrogen. Steady state liquid nitrogen boil-off was modeled assuming half the surface area was cooled with vapor through natural convection, with the remaining surface area modeled by liquid natural convection or nucleate boiling. Empirical liquid nitrogen boil-off data was derived from measuring the change in tank mass over time which was 4% greater than modeled performance.

Speaker: Patrick Adam (HYdrogen Properties for Energy Research (HYPER) Laboratory, Washington State University)
• 171
Cryogenic Permeation of Helium and Hydrogen through Polymer Films

Cryogenic permeation of helium and hydrogen is important for the development of light-weight insulation systems. In this work, we utilized a custom membrane support structure to measure helium and hydrogen permeation rates with a calibrated Adixen Graph D+ variable mass leak detector. Preliminary steady-state and thermal-transient tests of cryogenic helium and hydrogen permeating through 1 mil polyethylene terephthalate (PET) have been conducted between 30 – 90 K. Initial results confirm early experimental efforts that cryogenic permeation strongly deviates from classical Arrhenius-based diffusion. Transient tests conducted with PET and helium have also been conducted between 30 – 300 K, and confirm that permeability begins to deviate from the Arrhenius relation at 150 K.

Speaker: Kjell Westra (Washington State University)
• 172
Cryogenic Upgrade of the Low Heat Load Liquid Helium Cryostat used to House the Cryogenic Current Comparator in the Antiproton Decelerator at CERN

The Cryogenic Current Comparator (CCC) and its purpose built cryostat were installed in the low-energy Antiproton Decelerator (AD) at CERN in 2015. A pulse-tube cryocooler recondenses evaporated helium to liquid at 4.25 K filling the inner vessel of the cryostat at an equivalent cooling power of 0.55 W. To reduce the transmission of vibration to the highly sensitive CCC the titanium support systems of the cryostat were optimised to be as stiff as possible while limiting the transmission of heat to the liquid helium vessel.
During operation the liquid helium level in the cryostat was seen to reduce, indicating that heat load was higher than intended. To verify the reason for this additional heat load and improve the cryogenic performance of the cryostat an upgrade was undertaken during the 2016 technical stop of the AD.
This article presents the studies undertaken to understand the thermal performance of the cryostat and details the improvements made to reduce heat conduction, techniques employed to reduce transmission of thermal radiation, and procedures used to reduce the diffusion of helium to the vacuum space through ceramic isolators. Finally the upgraded cryogenic performance of the cryostat is presented.

Speaker: Mr Torsten Koettig (CERN)
• 173
Development and testing of a thermal switch used in an integrated cooler system

In this paper, a thermal switch used in an integrated cooler system, which consists of a single stage pulse tube refrigerator integrated with a small amount of a phase change material, will be introduced. During the heat load operation, the phase change unit absorbs heat loads by melting a substance in a constant pressure-temperature-volume process, meanwhile, the refrigerator is stopped to avoid vibrations and the thermal switch automatically turns off to reduce the heat leakage between the refrigerator and the phase change unit. Once the substance has been completely melted, the refrigerator begins to work and the thermal switch automatically turns on to reduce the thermal resistance and then the phase change material can refreeze.
The working principle, structure and material selection criteria of the thermal switch will be described in detail in this paper. In addition, the corresponding experimental device was set up and the performance of the thermal switch has been tested. At present, the measured temperature difference between the cold end and the warm head of the thermal switch is less than 0.2 K. The tested “on” and the “off” resistance ratio is 2245, and the “on” resistance and the “off” resistance is 0.224 K/W and 503 K/W, respectively. The heat loss of the test thermal switch is 137.5 mW, while without the thermal switch, the leakage heat is 549.9 mW.

Speakers: Dr Liubiao Chen (Chinese Academy of Sciences Key Laboratory of Cryogenics, Technical Institute of Physics and Chemistry) , Prof. Junjie Wang (Chinese Academy of Sciences Key Laboratory of Cryogenics, Technical Institute of Physics and Chemistry)
• 174
Qualification of a vertical test cryostat for MLI performance tests between 20 to 60 K and 4.5 K

Boil-off calorimetric measurements of Multilayer Insulation (MLI) performances between 4.2 K and shield temperatures varying between 20 K and 60 K are in preparation at CERN for an extensive characterization of MLI blankets of the LHC type. These tests will extend the performance measurements of the blankets to thermal shield temperatures lower than nominal as well as providing performance data for MLI systems with thermal shields operated at lower temperatures as is being proposed for new large accelerators like the Future Circular Collider (FCC). Tests will also cover MLI with different number of layers and layer densities and measure the performance in degraded vacuum. The vertical test cryostat in use has been formerly developed by Wroclaw University of Technology, and consists of an inner liquid Helium tank surrounded by a liquid Nitrogen vessel. In order to have a thermal shield at variable temperatures, an aluminium screen has been designed to be inserted between the two vessels and in thermal contact through a weak link with the guard LHe chamber, thus ensuring a lowest temperature of 20 K. Higher temperatures are obtained by electrical heating of the shield. This paper presents the design of the cryostat and the first qualification tests of the system. The experimental campaign will also be outlined.

Speaker: Valentina Venturi (CERN)
• 175
Research of the vapor cooled shield in cryogenic liquid storage

Long duration storage of cryogenic fluids is an essential requirement for space missions. Thermal optimization of the storage system is a key objective of the design process to minimize environmental heat leak. The objective of this research is to focus on the thermal optimization of the vapor cooled shield (VCS) in cryogenic liquid storage. Two types of the vapor cooled shield have been studied: those that use the boil-off gasses from the cryogen and those that require additional fluid mass to compensate for the boil-off losses. The effects of the VCS positon, the VCS temperature, the VCS flow rate on the insulation performance on the insulation performance will be simulated and analyzed. An insulation performance testing device has also been designed, built and tested. The simulation results, together with the typical test results of VCS, will be presented in this paper.

Speakers: Dr Liubiao Chen (Chinese Academy of Sciences Key Laboratory of Cryogenics, Technical Institute of Physics and Chemistry) , Prof. Junjie Wang (Chinese Academy of Sciences Key Laboratory of Cryogenics, Technical Institute of Physics and Chemistry)
• C2PoB - Expanders I Exhibit Hall AB

Exhibit Hall AB

Conveners: Kenichi Sato (Japan Science and Technology Agency) , Yatming Than (BNL)
• 176
A study of solid lubricant coating for gas bearing of turbine-expander

Abstract：In the start-stop phase, the foil in the gas foil bearing and the shaft are in a dry friction state. The solid lubricating coating on the foil and rotor has a crucial effect on bearing‘s using life. The friction and wear characteristics of several coating materials， like molybdenum disulfide, aluminum oxide, dense Cr, polyamide，were tested on the friction and wear test rig. The parameters（the bonding strength of the coating and the base material, surface roughness, friction coefficient，etc.） were measured to analyze the effect of the different friction pairs and the preparation process of coating. In this paper, the test materials were also tested on the turbine start-stop test rig.
Keywords：gas foil bearing； tribological properties； start-stop performance； solid lubricant coating
coating

Speaker: xingrui liu (Technical Institute of Physics and Chemistry CAS)
• 177
Effect Of Leading-edge Geometry And Thickness On The Performance Of Miniature Cryogenic Expansion Turbine

Speakers: Mr Changlei Ke , Dr Lianyou Xiong (Technical Institute of Physics and Chemistry, CAS) , Dr Nan Peng (Technical Institute of Physics and Chemistry, CAS) , Prof. Liqiang Liu (Technical Institute of Physics and Chemistry of CAS-Academia Si)
• 178
Numerical and Experimental Study of the Performance Effect of Varying Vaneless Space in Turboexpander Nozzles

An extensive experimental program has been carried out on a 22 mm tip diameter radial-axial flow cryogenic turboexpander, in order to directly compare performance characteristics by varying the vaneless space. A reference nozzle with radial clearance 0.5 mm was used in the refrigeration system, and seven other nozzles were designed with radial clearance of 0.1 mm, 0.2 mm, 0.8 mm, 1.0 mm, 1.2mm , 1.5 mm and 2mm. As part of the design process a series of CFD simulations were carried out in order to guide design iterations towards achieving a matched flow capacity for each design. In this way the variations in the stage efficiency could be attributed to the different vaneless space only, thus allowing direct comparisons to be made. Interstage measurements were taken to capture the static pressure distribution at the rotor inlet and these measurements were then used to validate subsequent numerical models. The overall losses for different stators have been quantified and the variations in the measured and computed efficiency were used to recommend optimum values of the ratio of the nozzle vane trailing edge radius to the rotor leading edge radius (Rte/rle).

Speaker: Dr Lianyou Xiong (Technical Institute of Physics and Chemistry, CAS)
• 179
Optimization Design of Turbo-expander Gas Bearing for a 500W Helium Refrigerator

Turbo-expander is the core machinery of the helium refrigerator. Bearing as the supporting element is the core technology to impact the design of turbo-expander. The perfect design and performance study for the gas bearing are the premise to ensure the stability of turbo-expander. In this paper, numerical simulation is used to analyze the performance of gas bearing for a 500W helium refrigerator turbine, and the optimization design of the gas bearing has been completed. And the gas bearing structure parameters have a guiding role in the processing technology. Finally, the turbine experiments verify that the gas bearing has good performance, and ensure the stable operation of the turbine.

Speaker: shanshan LI
• 180
Parametric studies on floating pad journal bearing for high speed cryogenic turboexpanders

Speaker: Dr Anindya Chakravarty (Bhabha Atomic Research Centre, India; Fermilab, USA)
• 181
Thermodynamic Analysis on of Skid-Mounted Coal-bed Methane Liquefaction Device using Cryogenic Two-Phase Turbo-Expander

Coal-bed methane (CBM) reserves are rich in Sinkiang of China, and liquefaction is a critical step for the CBM exploration and utilization. Different from other CBM gas fields in China, CBM distribution in Sinkiang is widespread but scattered, and the pressure, flow-rate and nitrogen content of CBM feed vary significantly. The skid-mounted liquefaction device is suggested as an efficient and economical way to recover methane. Turbo-expander is one of the most important parts which generates the cooling capacity for the cryogenic liquefaction system. Using the two-phase turbo-expander, more cooling capacity and higher liquefied fraction can be achieved. In this study, two skid-mounted CBM liquefaction processes are analyzed: one process is based on the direct expansion of feed gas and another process is based on nitrogen expansion cooling cycle. Cryogenic two-phase turbo-expander is employed to improve the efficiency of CBM liquefaction process. The unit liquefaction power consumption for CBM feed gas is used as the object function for process optimization, and optimum parameters of the two liquefaction processes with different pressure, flow-rate and nitrogen content are obtained. Based on the optimal results, the off-design performance in a wide operation range and the effects on liquefaction performance of two-phase turbo-expander are investigated.

Speaker: Mr Lu Niu (State Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University)
• C2PoC - Aerospace Cryocoolers I Exhibit Hall AB

Exhibit Hall AB

Conveners: Bradley Moore (JPL) , Mr Tanh Nguyen (Northrop Grumman)
• 182
Attenuation of cryocooler induced vibration in infrared imagers using multimodal tuned dynamic absorbers

Modern infrared imagers often rely on split Stirling linear cryocoolers comprising compressor and expander units interconnected by the configurable transfer line. The relative position of the cryocooler components is governed by the optical design along with packaging constraints.
Vibration export produced by such a cryocooler is a pair of tonal and coherent forces. The resulting angular and translational vibration may produce excessive line of sight jitter and defocusing affecting imaging performance in the long range and high resolution infrared imagers.
Since linear cryocooler is usually driven at a fixed and precisely adjustable frequency, a tuned dynamic absorber is ideally suited and cost effective tool for attenuation the cooler induced vibration and improving optical performance. As different from the traditional unimodal concept, the authors are considering multimodal tuned dynamic absorber made in the form of weakly damped mechanical resonator, where the frequencies of useful dynamic modes are essentially tuned to the driving frequency. Dynamic analysis and experimental testing show that the dynamic reactions (forces and moments) produced by such a device may simultaneously attenuate both translational and angular components of cryocooler-induced vibration, thus improving the imagery quality. The authors are considering different embodiments and their suitability for different packaging concepts. The outcomes of theoretical predictions are supported by full scale experimentation.

Speaker: Dr Alexander Veprik (SCD)
• 183
Numerical simulation of the heat and mass transfer within a sorption-compressor cell for cryogenic cooling

Sorption compressor is the most critical component in a sorption-based cooler that is appealing to many applications because of its plausible feature of vibration-free. To design a sorption compressor, it is essential to understand the thermal and hydraulic behaviors within the sorption cells. In this paper, based on a dynamic model developed previously, the detailed heat and mass transfer in the sorption-compressor cell has been numerically simulated. The simulated results reveal the inhomogeneous desorption/adsorption phenomenon due to the temperature and pressure distribution within the sorbent during a sorption-cycling period. The analysis is useful to help further optimizing the cell configuration to improve the performance and reduce the size.

Speaker: Dr Yingzhe Wu (Zhejiang University)
• 184
Simulation of Diffusion Process of Contamination Gas in Pulse Tube Cryocooler

Contamination gas is one of the four key factors degrading the long life of pulse tube cryocooler. In this paper, in order to optimize the contamination control measure and improve the life of cryocooler, the transmission of contamination gas had been deeply studied. The fluent software was used to simulate the diffusion of contamination gas among piston clearance, intermediate connecting pipe and regenerator. Mass flow of contamination gas and gas partial pressure in the regenerator were calculated. It would provide support for mechanism of contamination gas condensation and studying regenerator failure.

Speakers: Xiaohua Zhang (Technical Institute of Physics and Chemistry, CAS) , Prof. Houlei Chen (Technical Institute of Physics and Chemistry, Chinese Academy of Sciences) , Dr Yuexue Ma
• 185
The experimental optimization of the linear compressor for space 4K JT cooler

JT compressor is one of the Key components in space 4K JT cryocooler. The oil-free linear compressor becomes issue of the space JT compressor research because of its high reliability, high efficiency, long life and simple structure.
In this paper, the linear JT compressor developed by our laboratory is experimentally studied for the purpose of improving its pressure ratio. The stiffness of the plate spring is optimized. Besides, the influence of charge pressure, input power and operating frequency are tested to find out its optimum working condition. And the stroke of the piston is measured to evaluate the performance of the JT compressor. Eventually, pressure ratio of the JT compressor increases from 7.5 to 12 in two-stage compression. And pressure ratio of 17.6 is gained in three-stage compression.

Speakers: Mr Yuexue Ma , Dr Juan Wang , Dr Yanjie Liu (Technical Institute of Physics and Chemistry CAS) , Dr Jianguo Li , Prof. JingTao Liang
• 186
The study on high efficiency and low vibration flexure bearing stirling cooler

A high efficiency and low vibration stirling cooler has been demonstrated for cooling down the sensitive IR devices. A high efficiency compressor implementing the technology of dual opposed moving magnet and flexure bearing has been optimized to drive pneumatically a stirling cold finger also implementing flexure bearing technology. Through theoretical study and experimental study on the spring stiffness and the stroke of the displacer, the cooler could reach performance of 3W/80K under 60 W of electrical power.
It is also particular important that the suppression of the vibrations coming from the compressor and the stirling cold finger. The vibration of the compressor was caused by the unbalance force between dual opposed structures. It was suppressed by reducing the weight of moving-mass and controlling the process of assembling. The vibration suppression of the stirling cold finger was implemented in terms of a mass-spring passive balancer. The vibration of compressor and the stirling cold finger could decreased to 10mg and 5mg respectively under the above solutions.

Speaker: Dr Chuanlin Yin
• 187
The study on the effect of gas contamination in stirling cooler

One of the most important characteristics of spaceborne stirling cryocooler is its reliability over a lifetime. The wear abrasion and gas contamination existing in stirling cryocooler are the most failure modes that influence the reliability of spaceborne stirling cryocooler. While design improvements have reduced the probability of the wear abrasion, the excessive gas contamination is still a major risk, typically in excess of 10 years.
Aimed at gas contamination failure mode in stirling cooler, experiments were realized in order to study the effect of contamination on the working gas of stirling cryocooler operating at 80 K. The accelerated contamination experiments were performed to quantify the effect of impurity gas. The curve of the outgassing rate as a function of the time in the stirling cooler was obtained and discussed. The results supported the reliabilty design and test of stirling cooler.

Speaker: Dr Chuanlin Yin
• C2PoD - Gas and Fluid Mixtures Exhibit Hall AB

Exhibit Hall AB

Conveners: Dr Amir Jahromi (NASA/GSFC) , Jacob Leachman (Washington State University)
• 188
Analytical analysis of mixture enthalpies

Investigating cooling cycles operating with gas mixtures require the ability to evaluate the thermodynamic properties of mixtures, usually as a function of temperature, pressure, and composition. Working with mixed refrigerants for Joule-Thomson (JT) cryocoolers, it is desired to calculate the enthalpy of mixtures for determining their specific cooling power. Evaluating the mixture enthalpies is essential at the earliest stage of the research, in order to determine the mixture composition. Most researchers use available data bases for determining the properties of mixtures; however, it appears that data base results are often limited by temperatures, pressures, and components.
In this paper an analytical method for calculating the enthalpy of mixtures is presented. The method consists of equation of state calculations, and the results are compared with the enthalpies provided by REFPROP™ data base. This method is implemented in our research procedure for developing mixed refrigerant JT cryocoolers.

Speaker: Dr Nir Tzabar (Ariel University)
• 189
Cryosorption of helium and nitrogen on activated carbon-combined experiment and simulation study

Cryogenic adsorber is essential in large cryogenic engineering system due to the high quality gas demand, the design of the adsorber requires accurate adsorption data. A cryosorption setup has been built to investigate the cryogenic adsorption of helium and nitrogen on commercial PICA activated carbon, molecular simulation of helium and nitrogen on activated carbon is also studied based on amorphous carbon model. Combined with the cryosorption data, a revisit to the design of a 80K cryogenic adsorber is also included, it helps in the lateral design of the cryogenic adsorber in large cryogenic engineering.

Speaker: Hengcheng Zhang (Technical Institute of Physics and Chemistry of Chinese Academy of Sciences)
• 190
Modelling the Effects of Dissolved Helium Pressurant on a Liquid Hydrogen Rocket Propellant Tank

For decades NASA has used helium to pressurize liquid hydrogen propellant tanks to maintain tank pressure and reduce boil-off. This process causes helium gas to dissolve into liquid hydrogen creating a cryogenic mixture with thermodynamic properties that vary from pure liquid hydrogen. Traditional NASA models have been unable to account for this dissolved helium due to a lack of fundamental property information. Recent measurements of parahydrogen-helium mixtures enabled the development of the first multi-phase EOS for parahydrogen-helium mixtures. This new EOS has been implemented into NASA’s Generalized Fluid System Simulation Program (GFSSP) to determine the significance of mixture non-idealities. A model was developed for a simple self-pressurization of a liquid hydrogen propellant tank due to boil-off. The model was run assuming that the liquid propellant was pure liquid hydrogen and then assuming helium dissolved into the liquid using the new helium-hydrogen EOS. The analysis shows that having dissolved helium in the propellant does not have a significant effect on the tank pressurization rate but does affect the rate at which the propellant temperature rises.

Speaker: Ian Richardson (Washington State University)
• 191
Numerical model of cryogenic gas dispersion with phase change of water

Numerical study of cryogenic gas dispersion benefits for the risk reduction of leakage of hazard cryogenic gases. Up to now, phase change physics of small quantity of water involved in the cryogenic gas has not been considered in numerical modeling of the dynamic dispersion behaviors of cryogenic gas in the atmosphere. The present study develops a computational fluid dynamic (CFD) model considering water phase change to simulate the atmospheric cloud flow resulting from the cryogenic gas leakage. Numerical simulation of liquefied natural gas (LNG) dispersion was performed, in which two-phase flow was modeled based on the single-fluid mixture model, and the species dispersion of natural gas, water vapor, oxygen and nitrogen in the atmosphere were calculated based on the respective convective-diffusion conservation equations. The original Hertz-Knudsen relation was modified to determine the mass transfer between the water vapor and the droplet, in which, the sensitivity of condensation and evaporation coefficients on simulating results were examined. The results of the calculation were compared with the counterparts without accounting for the phase change, the experimental data from Burro and Coyote trials and the simulation results with software SLAB and FEM3. The comparisons validate the improvements of the present two-phase modeling approach. Simulations and analysis of nitrogen gas dispersion were also presented.

Speaker: Mr Jingfeng Li (Zhejiang University)
• C2PoE - Industrial Applications Exhibit Hall AB

Exhibit Hall AB

Conveners: Mr Joseph Hurd (FNAL) , Jennifer Marquardt (Ball)
• 192
Design and Manufacturing of the Cryogenic Cooling System for the Rotating Magnetic Validator of the 10 MW SUPRAPOWER Offshore Superconducting Wind Turbine

The SUPRAPOWER consortium, an EU FP7 funded research project, is developing an innovative 10 MW class superconducting generator (SCG) to provide an important breakthrough in the offshore wind industry. It is a partial SCG with MgB2 wires used in the field coils while conventional copper conductors are used in the armature coils. Due to the requirements of handling, maintenance, reliability of long-term offshore operation, the cooling system of SUPRAPOWER SCG adopts a modular and cryogen-free design. The SCG contains 48 identical superconducting coils and each coil is enveloped in one of the 48 identical modular cryostats.
Benefiting from the modular concept, the key challenges of such innovative 10 MW SCG e.g. the modular superconducting (SC) coil and associated cryogenic systems could be validated through a scale-down experiment. This validator consists of two modular SC coils rotating together with the iron poles and yoke to generate the magnetic field. The modular cryostat enveloping the coil consists of a vacuum vessel, an active cooled thermal shield with multi-layer insulation and corresponding supporting structures. In order to achieve the SC coils working temperature of 20 K, a two-stage G-M cryocooler will be installed and linked to the two modular cryostats by means of conductive copper connection. A non-modular cryostat was developed to envelop the cold head of the cryocooler, the thermal link, and three binary current leads to feed electrically the coils while keeping the heat load from ambient as low as possible. A rotary union with Ferrofluid sealing was developed to transfer the helium gas between the rotating cold head and stationary oil-lubricated compressor. In this paper, the design and manufacturing of each component will be described, and the assembly and some preliminary experimental test of the cryogenic cooling system for the validator will be also presented.

Speaker: Dr Jiuce Sun (Institute for Technical Physics (ITEP))
• 193
Development of a rotary union for Gifford-McMahon cryocoolers utilized in a 10 MW Offshore Superconducting Wind Turbine

The SUPRAPOWER, an EU FP7 funded research project, are developing an innovative 10 MW class superconducting generator (SCG) to provide an important breakthrough in offshore wind industrial solutions. It is a partial SCG with MgB2 wires used in the field coils while copper wires at ambient temperature are implemented in the armature coils. The cryogenic cooling system of SUPRAPOWER SCG adopts a cryogen-free design in view of the handling, maintenance, and reliability of long-term offshore operation, that is, the superconducting coils are cooled down to working temperatures with regenerative cryocoolers by means of conduction.
By evaluating the availability and required cooling capacity in the temperatures range around 20 K, we finally selected a Gifford-McMahon (GM) cryocooler among all the candidates since GM cryocoolers are becoming readily available from many manufacturers at relatively low cost and service periods of one or two years. The cold head of GM cryocooler will be directly attached or linked to the rotating superconducting coil. Hence, the cold head is supposed to rotate together with the rotor. However, the compressor of GM cryocooler is sensitive to pitch, and must not be kept beyond 5 degrees, not to mention rotating conditions since it normally utilizes oil lubricated Helium scroll compressor which is well commercialized and extensively used in the refrigeration industry. As a consequence, a rotary union (RU) utilizing Ferrofluidic® sealing technology was developed to transfer helium gas between the rotating cold head and stationary helium compressor at ambient temperatures. It contains a high-pressure and low-pressure helium path with multiple ports, respectively. Besides the helium path, slip rings with optical fiber channels are also integrated into this RU to transfer current and measurement signals. In this paper, the design, manufacturing and preliminary test of the RU will be conducted.

Speaker: Dr Jiuce Sun (Karlsruhe Institute of Technology)
• 194
Gas propagation following a sudden loss of vacuum in a pipe cooled by He I and He II.

Many cryogenic systems around the world for cost, preventative damage, safety or other reasons are concerned with the sudden catastrophic loss of vacuum.
The experiments in this paper were designed to simulate the sudden vacuum break in the beam-line pipe of a liquid helium cooled superconducting particle accelerator. This paper expands previous research conducted at the NHMFL and looks at the differences between normal helium (He I) and superfluid helium (He II). For the experiment, a straight pipe was evacuated and immersed in liquid helium at 4.2K and 2 K. Vacuum loss was simulated by opening a solenoid valve on a buffer tank filled with 760 Torr nitrogen gas. The nitrogen passed through a venture tube so the mass flow rate could be metered. Temperature was monitored along the tube at regular intervals and a measured temperature rise indicated the arrival of the gas front.
Our preliminary results suggested that the speed of the gas front through the experiment decreased exponentially along the tube for both normal liquid helium and super-fluid helium. Furthermore, the decay of the gas front speed does not show obvious difference between the two distinct helium phases despite the difference in helium heat transfer mechanisms: convection vs thermal counterflow. More systematic measurements are planned in a helical tube system to further verify the results.

Keywords: Air Propagation, Loss of vacuum, Superfluid helium, Particle accelerator

Speaker: Nathaniel Garceau (National Magnetic Field Labortory - FSU)
• 195
Investigation of a working fluid for cryogenic energy storage systems.

Cryogenic energy storage (CES) systems are promising alternative to existing electrical energy storage technologies such as a pumped hydroelectric storage (PHS) or compressed air energy storage (CAES). In CES systems the electrical energy is used to liquefy a cryogenic fluid. The liquid can be stored in large cryogenic tanks for a long time. When a demand for the electricity is high the liquid cryogen is pumped to high pressure and then warmed in a heat exchanger using ambient temperature or an available waste heat source. The vaporized cryogen is then used to drive a turbine and generate the electricity. Most research on the cryogenic energy storage focuses on the liquid air energy storage, as atmospheric air is widely available and therefore it does not limit a location of the energy storage plant. Nevertheless, the CES with other gases as the working fluids can exhibit a higher efficiency. In this research a performance analysis of simple CES systems with several working fluids was performed.

Speaker: Paweł Wojcieszak (Wroclaw University of Science and Technology)
• 196
Production of LNG with an Active Magnetic Regenerative Liquefier

Production of LNG with an Active Magnetic Regenerative Liquefier
By Corey Archipley1, John Barclay1, Jamie Holladay2, Kerry Meinhardt2, Evgueni Polikarpov2, and Edwin Thomsen2
1 Emerald Energy NW, LLC. (EENW); 2 Pacific Northwest National Laboratory (PNNL). The support of this work by the U.S. DOE/EERE/FCTO is appreciated.
The figure of merit (FOM) of a liquefier is the ratio of ideal to real specific work required to liquefy a unit mass of gas. Because liquid cryogens are excellent for storage, transport, and delivery of industrial gases and cryofuels like LNG and LH2, conventional gas-cycle liquefier technology has been well developed with a maximum FOM of ~0.35. Demonstration of regenerative magnetic cycles near room temperature in 1976 and invention of the active magnetic regenerator in 1982 identified the potential of magnetic liquefaction technology for higher FOMs. We have designed an efficient active magnetic regenerative liquefier (AMRL) to liquefy ~1000 gallons/day of LNG at 123 K using 200 psia natural gas feedstock at 280 K. Eight stages with different magnetic refrigerants with large magnetocaloric effects near the average hot temperature of each stage were selected. A numerical model was used to calculate thermodynamic performance as a function of key design choices. The 1-D transient model updates pressure, temperature, flow, magnetic-field dependent properties of magnetic refrigerants and helium heat transfer gas each microsecond time step. It uses a finite difference Eulerian technique to solve five coupled non-homogeneous partial differential equations that describe operation of each AMRR stage in the AMRL. The model tracks each regenerator vs time through the four AMR cycle steps: hot-to-cold flow in demagnetized regenerators; no flow during magnetic field changes; cold-to-hot flow in magnetized regenerators and no flow during opposite magnetic field changes. The design performance, size, cost, and FOM of this LNG liquefier are presented and discussed in this paper.

Speaker: Dr John Barclay (Emerald Energy NW, LLC.)
• 197
Thermodynamic characteristics of a novel wind-solar-liquid air energy storage system

Due to the nature of fluctuation and intermittency, the utilization of wind and solar power will bring a huge impact to the power grid management. Therefore a novel hybrid wind-solar-liquid air energy storage (WS-LAES) system was proposed to solve the problems. In this system, wind and solar power are stored in the forms of liquid air by cryogenic liquefaction technology and thermal energy by solar collector, respectively. Owing to the high density of liquid air, the system has a large storage capacity and no geographic constraints. The WS-LAES system can store unstable wind and solar power for a stable output of electric energy and hot water.Combined with organic Rankin cycle (ORC), the energy cascade utilization was also achieved. Moreover, the thermodynamic analysis was carried out to investigate the best system performance. The result shows that the increase of ambient temperature has a negative effect on the system performance, while the increase of turbine inlet temperature has a positive effect.

Speaker: Liubiao Chen (Key Laboratory of Cryogenics, Technical Institute of Physics and Chemistry, CAS)
• C2PoF - Novel Devices I Exhibit Hall AB

Exhibit Hall AB

Conveners: Dr Mark Kimball (NASA / GSFC) , Peter Kittel (Retired)
• 198
Analytical and numerical performance models of a Heisenberg Vortex Tube

Analytical and numerical investigations of a Heisenberg Vortex Tube (HVT) are performed to estimate the cooling potential with cryogenic hydrogen. The Ranque-Hilsch Vortex Tube (RHVT) is a device that tangentially injects a compressed fluid stream into a cylindrical geometry to promote temperature separation between inner and outer flows. The HVT is the result of lining the inside of a RHVT with a hydrogen catalyst. This is the first concept to utilize the endothermic heat of para-orthohydrogen conversion to aid primary cooling. A review of 1st order vortex tube models available in the literature is presented and adapted to accommodate cryogenic hydrogen properties. These first order model predictions are compared with Computational Fluid Dynamics (CFD) simulations.

Speaker: Mr Carl Bunge (Washington State University )
• 199
Design and experimental measurements of a Heisenberg Vortex Tube for hydrogen cooling

Small, modular, efficient hydrogen liquefiers are needed to expand use of hydrogen as an energy currency. The Heisenberg Vortex Tube (HVT) is a novel cooling concept based on the Ranque-Hilsch Vortex Tube (RHVT) with a catalytic liner – the first concept to reverse the exothermic ortho-parahydrogen conversion to directly aid primary hydrogen cooling. Analysis of the design parameters of the HVT and experiment are presented. Initial experimental measurements are presented of the efficiency gains by the HVT concept over traditional RHVT.

Speakers: Elijah Shoemake (Washington State University) , Carl Bunge (Washington State University)
• C2PoG - Superconducting Magnet Systems - Experimental Studies Exhibit Hall AB

Exhibit Hall AB

Conveners: Luisa Chiesa (Tufts University) , Owen Christianson (NDI)
• 200
Cooldown studies for the superconducting coils of the hybrid magnet at CHMFL

A hybrid magnet which includes a water-cooled magenet and a superconducting magnet has been developed at the High Magnetic Field Laboratory of the Chinese Academy of Sciences. The superconducting coils which are made of Nb3Sn cable-in-conduit conductor (CICC) are forced-flow cooled by 4.5 K supercritical helium. In this paper, a mathematical method is proposed to simulate the pressure, temperature and mass flow rate distribution of each coil in the process of cooldown from room temperature to 4.5 K with maximum temperature differences of 50 K. The experimental results show that it takes 24 days to cool down all the superconducting coils to 4.5 K and the characteristics of the supercritical helium in CICCs are measured. As a conclusion, the functions of the input temperature for the cooldown, the distributions of mass flow rates in each coil are summarized, and the friction factor, as well as heat transfer coefficient in each CICC channel is calculated and the related former empirical formula has been revised.

Speaker: Ms Yu Xie
• 201
Superconducting Magnet Stability and Wire Insulations

In order to improve the stability of the superconducting magnets, e.g. MRI magnets, the NbTi superconducting wires were used to wind magnets without electrical insulation layers. The magnets were made with different induction values. As comparisons, the same kind of wires with insulation layers were used to wind magnets of similar induction values. The magnets were tested at 4.2K in a LHe bath. The results were analyzed and theoretically investigated. The results reveal that non-insulation winding is beneficial to magnet stability, however, the long charging and discharging period make it unacceptable for the technique to be put into practical applications.

Speakers: Mr Q.Y. Hu (Ningbo Jansen Mechanism Co., Ltd) , Mr X.Q. Duan (Ningbo Jansen Mechanism Co., Ltd)
• C2PoH - Large Scale Refrigeration and Liquefaction II Exhibit Hall AB

Exhibit Hall AB

Conveners: Lars Blum (Linde Kryotechnik AG) , Dr John Weisend (European Spallation Source ERIC)
• 202
An overview of a repair of internal leak in the cold box of Helium liquefier made by Linde

This article mainly introduces the treatment of the internal leakage of the helium liquefier. The Linde L70 helium liquefier I run was found to be difficult to maintain the vacuum, the system is difficult to carry out. Gradual investigation of the problem, that is cold box internal pipeline leakage. Then I and my colleagues in the Linde company's proposal to develop a maintenance plan, the first pipeline separation, and then split the cold box, leak detection, welding repair. Because the leak is very small, leak detection takes a lot of time, try a variety of leak detection methods, and ultimately find the leak and repair successfully. After the repair, helium liquefier works well so far.The maintenance was carried out at the location of the plant, to avoid the cold box sent back to the original factory testing and maintenance. It is hoped that these experiences will help the helium liquefier users in a similar situation.

Speaker: Mr Zezhang Wang (National Institute of Metrology/China)
• 203
Balanced Design and Commissioning of a 500W@4.5K Helium Refrigerator and its Liquefier

In this paper, a 500W@4.5K helium refrigerator for ADS (Accelerator Driven Subcritical) project of CAS (Chinese Academy of Sciences) has been designed and constructed. The function requirements and process analysis of this helium refrigerator are described. Based on the floating pressure cycle, the balanced design between the refrigerator and its liquefier for an equal Carnot work with the same high efficiencies is presented. The constraints of components and operation strategies in refrigeration mode and liquefaction mode are discussed. Commissioning results indicate that this 500W/4.5K helium refrigerator can provide 5.17g/s (or 150L/h) LHe in liquefaction mode or 500W at 4.5K in refrigeration mode with the FOM (Figure of Merit) of 14%. Exiting problems are analyzed and discussed through comparing the theory calculation, dynamic simulation and experimental data, and some suggestions end this paper.

Speaker: Dr Xiaofei Lu (Institute of Plasma Physics,Chinese Academy of Sciences)
• 204
Commissioning and Testing of a new 4.5K Cold Box for JLab Cryogenic Test Facility

A new 4.5K cold box at Jefferson Lab (JLab) Cryogenic Test Facility (CTF) was recently installed and commissioned to upgrade the existing 4.5 K refrigeration system and work in parallel with the existing 4.5 K cold box. This new 4.5 K cold box is equipped with two turbo-expanders and, at its maximum capacity condition, can support up to 6.6 g/s of helium liquefaction or 650 W of refrigeration at 4.5 K. It can also handle up to 10 g/s 30 K return flow for 2 K refrigeration recovery that supports cryo-module and superconducting cavity testing. Performances of the cold box at its maximum capacity conditions as well as several other operating modes were tested for acceptance. We will briefly review the new 4.5 K cold box design features and discuss the commissioning and performance testing results.

Speaker: Mr Thilan Wijeratne (Thomas Jefferson National Accelerator Facility)
• 205
Design, Fabrication, Installation and Commissioning of the Helium Refrigeration system Supporting Superconducting Radio Frequency Testing at Facility for Rare Isotope Beams at Michigan State University

The Facility for Rare Isotope Beams (FRIB) will be a scientific user facility for the Office of Nuclear Physics in the U.S. Department of Energy Office of Science (DOE-SC). The FRIB LINAC will be comprised of cryomodules each with multiple Superconducting Radio Frequency (SRF) cavities operating at 2 K. A helium refrigeration system was designed, fabricated, installed and commissioned in the SRF high bay building to test and certify these cavities and cryomodules before installation in the FRIB LINAC tunnel. The helium refrigeration system includes a helium refrigerator which has nominal capacity of 900 W at 4 K, 5000 L liquid helium storage dewar, helium gas storage, two room temperature vacuum pumps capable of 2.5 g/s each for 2 K testing, purifier, purifier recovery compressor, and the distribution system for liquid nitrogen and helium. The helium refrigeration system is now operational supporting three below grade cavity testing dewars and one cryomodule testing bunker meeting the required throughput of 1 cavity per day.

Speakers: Adam Fila (FRIB Michigan State University) , Chinh Nguyen (FRIB Michigan State University)
• 206
The Progress on 2K Cryogenic System for Superconducting Cavity of SSRF II

The Shanghai Synchrotron Radiation Facility (SSRF) is an intermediate energy light source built at Zhang-Jiang Hi-Tech Park in Shanghai, China. The SSRF consists of a 432 m circumference storage ring with operating energy of 3.5 GeV and minimum emittance of 2.9 nm-rad, a full energy booster, a 150 MeV electron Linac. The RF power and voltage required for storing the electron beam are provided by means of three SC cryomodules, each containing one 499.654MHz superconducting cavity. The cavities, made of Niobium, are bath-cooled with saturated liquid helium at 4.5 K. A cryogenic plant with cooling capacity of 650 W at 4.5 K has been in operation since August of 2008 to provide cooling for the three superconducting cavities.
In order to further improve the performance of SSRF, the following SC devices will be applied as the SSRF Phase II project:
1) One third harmonic SRF cavity with 1.5 GHz，to be positioned at the SSRF storage ring, will run at 2 K (31 mbar) by bath cooling.
2) One superconducting wiggler is to be used for one of the new-built beam lines, ultra-hard multi-functional beam line. The SC wiggler will be cooled by cryocoolers at 4.2 K region by bath cooling.
For the purpose of supporting operation of the above SC devices, a new cryogenic system ( SSRF-II cryoplant) with equivalent cooling capacity of at least 650 W at 4.5 K (including at least 60 W at 2 K) will be designed, fabricated, test and operated for the SSRF-II.
Additionally, the new cryoplant will be used as the back-up of current 650 W refrigeration system at 4.5 K to support normal operation of the online three 500MHz SRF cavities in case of any failure occurred to the current 4.5 K cryoplant.
This paper will present the whole plan of SSRF-II cryoplant.

Speaker: Jieping Xu (Shanghai Institute of Applied Physics. CAS)
• C2PoJ - Fluid Mechanics, Heat Transfer and Cryogen Properties I Exhibit Hall AB

Exhibit Hall AB

Conveners: Jaroslaw Fydrych (European Spallation Source ERIC) , Prof. John Pfotenhauer (University of Wisconsin-Madison)
• 207
Designing Calculation and Experimental Study of Sub-atmospheric Plate-fin Heat Exchanger for Superfluid Helium Refrigeration System

Based on the traditional heat exchanger design method, the sub-atmospheric plate-fin heat exchanger in superfluid helium refrigeration system is designed by calculating with distributed parameter differential element method. This enables to obtain the geometry，temperature distribution and the pressure drop inside the heat exchanger. So that the optimal solution can be selected after comparing a series of calculation and experimental results. Such method can provide a reference for the design and further exploration of sub-atmospheric heat exchangers.

Speaker: Wang Kunxiang (The Technical Institute of Physics and Chemistry of the Chinese)
• 208
Experimental and Computational studies of Heat Transfer for Wall-type and Fin-type Heat Exchanger

Wall-type heat exchanger(WTHX) and Fin-type heat exchanger(FTHX) are attached to the first and second stage cold head of two G-M crycoolers respectively in the simulating experimental platform of the internal purifier(SEPEIP). WTHX and FTHX play a significant role in SEPEIP, WTHX is designed to remove heat from helium and freeze-out extremely few impurities, FTHX is for further cooling the helium. In this study, numerical simulation and experimental results for WTHX and FTHX are carried out. According to the comparison, Numerical results are well consistent with the theoretical results. It is presented the better performance of the WTHX and FTHX..

Speakers: Prof. Laifeng Li (Technical Institute of Physics and Chemistry of the Chinese Academy of Sciences) , Dr Dong Xu (Technical Institute of Physics and Chemistry of the Chinese Academy of Sciences) , Hengcheng Zhang (Technical Institute of Physics and Chemistry, Chinese Academy o)
• 209
Numerical and analytical modeling of cryogenic carbon capture in a de-sublimating heat exchanger

Both numerical and analytical models are developed to characterize the heat and mass transfer processes in a cryogenic CO2, N2 mixture gas de-sublimating within a cross-flow finned duct heat exchanger system. Heat is transferred across the exchanger from the mixture gas to a flow of cold gas (either nitrogen or helium). The approach follows analyses similar to those used to characterize the condensation of water vapor out of a moist-air mixture. The models enable variations in the outlet temperatures of the gas mixture and coolant, the CO2 mole fractions at the outlet, and the temperature distribution and de-sublimating rate of CO2 to be studied as a function of the mixture and coolant flow rates, the inlet mixture composition, and the geometric parameters of the finned heat exchanger.

Speaker: Mr Zhitao Yu (University of Wisconsin-Madison)
• 210
Numerical investigation on shell side heat transfer and pressure drop in gas flow for spiral-wound heat exchangers

A computational fluid dynamics (CFD) model with simplified structure and periodic boundary conditions is applied to the shell side of spiral-wound heat exchangers. And a series of numerical investigations on heat transfer and flow characteristics are carried out using this model. The heat transfer coefficients on the bottom of tubes increases first and then decreases with radial angle, because of the influence of the back flow and the axial velocity for inclined tubes. The mean absolute deviation between simulated heat transfer coefficients and measured values for methane, ethane, nitrogen and a mixture (methane/ethane) is within 5% for Reynolds number over 30000. As for the pressure drop, the simulated values are smaller than the measured values and the mean absolute deviation is within 9%. The results of numerical simulation show that the pressure drops and heat transfer coefficients on shell side of spiral-wound heat exchangers decrease with the increase of the winding angle of the tubes. To consider of the winding angle, the modified correlations of Nusselt number and friction factor, and , are proposed.

Speakers: Qixiong Tang (Technical institute of physics and chemistry of CAS) , Dr M.Q Gong (Key Laboratory of Cryogenics, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences) , Dr X ZOU (Key Laboratory of Cryogenics, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences) , Dr G.F CHEN (Key Laboratory of Cryogenics, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences)
• 211
The Effect of Geometric Parameters on Multi-stream Parallel Flow Plate-Fin Heat Exchangers’ Effectiveness and Pressure Loss

To design the heat exchanger, whose effectiveness and pressure loss meet the process requirements, by using the minimum volume, the effects of geometric parameters on multi-stream parallel flow pilate-fin heat exchangers’ effectiveness and pressure loss should be studied. Using both numerical and experimental methods, this paper studies these effects. The results obtained in this paper are valuable for the optimum design of multi-stream plate-fin heat exchanger.

Speakers: Dr Peng Xu (The Technical Institute of Physics and Chemistry of the Chinese Academy of Sciences) , Dr Weiping Zhu (Chinese Academy of Sciences)
• 212
The effect of the natural convection of supercritical helium on the temperature stability in cryogenic system

With high specific heat and density, supercritical helium can be used to reduce the temperature fluctuation and improve temperature uniformity in the low temperature conditions. However, the natural convection of the supercritical helium has a great influence on the suppression of the temperature oscillation. In this paper, a transient three-dimensional numerical simulation is carried out for the natural convection in the cylinder with aspect ratio of 3 to analyze the effect of natural convection on transferring of temperature fluctuations. According to the results of numerical calculation, a cryogenic system cooled by GM cryocooler is designed to study the influence of natural convection of supercritical helium on temperature fluctuation suppression.

Speakers: Dr gang zhou (Technical Institute of Physics and Chemistry, CAS) , Ms Wei Pan (Technical Institute of Physics and Chemistry, CAS )
• 9:00 AM
Morning Break (9:00 - 10:00 a.m.) Cryo Expo, Exhibit Hall AB

Cryo Expo, Exhibit Hall AB

• M2OrA - Focused Symposia - Propulsion V: Motors & Generators Lecture Hall

Lecture Hall

Conveners: Tabea Arndt (Siemens AG, CT REE PEM) , Kiruba Haran (University of Illinois)
• 213
[Invited] Development toward all Superconducting Motors in Japan

Fully superconducting rotating machines produce the advantages of lightweight, compactness and high efficiency compared with conventional ones. When those are applied to electric propulsion aircrafts, tremendous innovation will be brought about to air transportation. To realize that, it is necessary to reduce the ac loss in superconducting armature windings, also to enhance the current capacity and to develop cooling systems with lightweight and availability of cold heat of liquid fuel such as hydrogen and methane. Our research group has developed these required techniques for REBCO superconducting transformers so far. The ac loss of REBCO superconducting windings was reduced by laser-scribing of a REBCO tape and its special winding. The current capacity of windings was enhanced without increment of ac loss by forming transposed parallel conductors. Turbo-Brayton refrigerators with neon gas as a working fluid were also developed. The compressor and expander both had turbines with a non-contact magnetic bearing. As a result, a 3φ-66kV/6.9kV-2MVA model transformer was successfully built with REBCO superconducting tapes. Currently, we are developing fully superconducting rotating machines applying the developed techniques to field and armature windings under the support of JST. Our first task was the verification of the applicability of ac loss reduction technique for transformer windings to the armature windings. The current sharing properties among the filaments in laser-scribed REBCO tapes wound into the armature winding of a small test motor were investigated during the operation in liquid nitrogen at 77K. The almost even current sharing among the filaments suggested the fact that no shielding current was induced and the ac loss was reduced in proportion to the filament width since the shielding current is a loop current. In addition we are developing superconducting triaxial cables. In this conference we will introduce out recent works in relation to the development of electric propulsion aircrafts.

Speaker: Masataka Iwakuma (Kyushu University)
• 214
[Invited] Flux Pump Brushless Exciters for HTS Rotating Machines

Synchronous generators employing rotor coils wound from high-Tc superconducting (HTS) wire, are attractive for a range of applications requiring very high torque and power densities. However, the injection of large DC currents into rotating HTS coils presents a technical challenge. In this paper we discuss the development of a new type of brushless exciter for HTS rotors, which is based on a dynamo-type HTS flux pump. This device applies a rotating magnetic field across the cryostat wall which leads to the injection of a DC superconducting current into the rotor coil circuit.

Our approach fundamentally reduces the thermal load upon the cryogenic system by removing the need for thermally inefficient normal-conducting current leads. It also obviates the need for high current slip-rings which can be subject to very high wear rates.

We report results from an experimental laboratory device and show that it behaves as a constant DC voltage source with an effective internal resistance. We then discuss the design of a prototype brushless exciter based on our experimental device, and describe its integration with a demonstration 10 kW HTS generator. We estimate the thermal load presented by our prototype exciter, and show that this can be further minimised by utilising duty cycle operation of the device. In this manner, the steady-state heat load is reduced by more than an order of magnitude below that of equivalently-rated metal current leads.

References:

1. Z. Jiang et al., Appl. Phys. Lett. 105, 112601 (2014)
2. Z. Jiang et al., Supercond. Sci. Technol. 28, 115008 (2015)
3. C.W. Bumby et al., Supercond. Sci. Technol. 29, 024008 (2016)
4. C.W. Bumby et al., Appl. Phys. Lett. 108, 122601 (2016)
Speaker: Chris Bumby (Victoria University of Wellington)
• 215
[Invited] High Power Density Electric Motors for Electric Aircraft: Superconductor and Permanent Magnet Approaches

Interest in fully electric and hybrid electric aircraft is being driven by gains in efficiency, fuel savings, noise and emission reductions and increased flexibility of aircraft and propulsion system design. magniX is developing and prototyping superconducting electric machines with the goal of demonstrating power densities in excess of 25 kW/kg.

Superconducting generators and motors are synonymous with enhanced efficiency, reduced weight and compact size compared to conventional technologies. magniX is building superconducting generators and motors suitable for intense energy and efficiency sensitive applications such as all electric aircraft motors and generators —it is the only known technology capable of satisfying these requirements.

magniX has unique capabilities and proven intellectual property in high power density electric motors suited to aircraft propulsion embodied in our magnifluxTM technology. Our approach overcomes many of the historical issues associated with superconducting machines by eliminating rotating cryogenic joints through the use of a stationary cryostat and non-cryogenic normal conducting rotor. Our novel flux directing coil arrangements maximize the air gap flux density while also eliminating the need for ferromagnetic shielding reducing overall weight significantly. A discussion of the progress of the magniflux alpha prototype design, construction and testing will be presented.

In the short and medium term, permanent magnet machines have a place in the electric aircraft segment. Results of the development and testing of our magni5 permanent magnet motor with a power density of 5kw/kg will be presented along with a discussion on thermal management and the optimization of the electromagnetic design of this class of machine.

Speakers: John Kells (magniX Technoliges Pty Ltd) , Dr Jason Chaffey (MagniX Technologies Pty Ltd)
• M2OrB - YBCO Coated Conductors II: Processing & Properties Hall of Ideas - EH

Hall of Ideas - EH

Conveners: Lukas Graber (Georgia Tech) , Arend Nijhuis (University of Twente)
• 216
[Invited] Description of temperature-, magnetic-field, and position-dependent current-voltage characteristics in high Tc superconducting long length coated conductors

In-field current transport property is one of the most important properties of high Tc superconducting tapes for practical applications. Usually the current-voltage (I-V) characteristics or critical current (Ic) are characterized by the four probe transport measurement or magnetization measurement using a short piece sample. In a practical application, however, the piece length of the tape strands reach more than hundreds of meters or km scale. This indicates that the influence of positional variation of Ic should also be taken into account to describe the I-V characteristics in a real device. In fact, the characterization of spatial Ic variation attracts much attention as a quality control of the long length tapes. However, the relationship between the spatial Ic variation and the local- and/or global-I-V characteristics are not well established. In this study, we have succeeded in measuring in-field Ic variation as a function of longitudinal coordinate, x, in reel-to-reel manner under external magnetic fields up to 4 T at 77 K and 65 K, respectively. We also obtained position-dependent I-V characteristics by site specified transport measurements using the same sample. We proposed an analytical model to describe the position-dependent I-V characteristics based on the Ic(x) in the long length tape. It has been shown that the analytical expression shows good agreement with the position-dependent in-field transport measurements. Namely, this approach allows us to describe the I-V characteristics as function of B, T, and x including position dependent n-index and localized flux flow dissipation in the long length tape.

Acknowledgements: This work was supported by “JSPS KAKENHI (16H02334)”.

Speaker: Prof. Takanobu Kiss (Kyushu University)
• 217
REBCO cable AC loss, inter-tape resistance and critical current reduction for mechanical bending

The AC loss of different HTS cable types were measured in alternating magnetic fields including Conductor On Round Core (CORC) cables, stacked tape conductors and Roebel cable. The applied AC magnetic field is sinusoidal with amplitudes in the range of 5 to 400 mT and frequencies up to 0.1 Hz. The AC loss of CORC and Roebel cable was measured at 4.2 and 77 K. Inter-tape contact resistance measurements showed differences for current sharing between REBCO tapes in HTS cables.
In addition detailed method of stress-strain state modeling in CORC conductors was developed. The model is based on Finite Element Method (FEM) and extensive strain measurements on REBCO tapes. Systematic measurements on single REBCO tapes were carried out combining axial tension and torsion as well as transverse loading. The FE model takes into account temperature dependence and the elastic-plastic properties of the tape materials and includes initial processing conditions during tape manufacture up to magnet operating conditions. Furthermore a comparison of FEM simulations with CORC cable bending experiments is presented with special attention for the critical bending radius as the threshold where the tapes in the CORC become irreversibly degraded. The influence of tape inter-layer friction was also investigated. A brief overview of the results is presented.

Speaker: Arend Nijhuis (University of Twente)
• 218
Calorimetric Measurements of Varying YBCO Conductors and Cables at High dB/dt in a Stator Machine Environment

A new facility for the measurement of AC loss in superconductors at high dB/dt has been developed, and recently tested and calibrated for operation. The test device has a spinning rotor consisting of permanent magnets arranged in a Halbach array; which exposes samples in a stator position with a peak radial field of 0.57 T, and with high rotation speeds up to 3600 rpm achieves a radial dB/dt is 543 T/s and tangential dB/dt is 249 T/s. Loss is measured by calorimetry using nitrogen boiloff from a double wall calorimeter feeding a gas flow meter, and the system was calibrated using power from a known resistor. For calibration, Cu-tape and YBCO-tape losses were measured and compared to results of a solenoidal magnet AC loss system measurement of the same samples but limited to a field of amplitude 0.1 T and a dB/dt of 100 T/s. Herein the use of this system for measuring AC losses of a variety of YBCO coated conductors and cables will be performed, and results will be compared to measurements with a a solenoid magnet system and theory. Coated conductors are provided by several manufacturers with different architectures including filamented, varying width, and different quench protection metal layers with varying thickness. Also AC losses will be reported on several types of cable structures, including stacked tapes and conductor-on-round-core (CORC) structures.

Acknowledgement: Air Force Office of Scientific Research (AFOSR), U.S. Air Force ResearchLaboratory – Aerospace Systems Directorate (AFRL/RQ)

Speaker: John Murphy (University of dayton Research Institute)
• 219
Single-strand excitation for measuring current sharing and ICR in cored and non-cored Nb3Sn Rutherford Cable at 4.2 K up to 12 Tesla

Measurements were performed on a 40 centimeters length of 27-strand cored (F095) and 27-strand RRP non-cored Nb3Sn Rutherford cable which were mounted onto a U-shaped holder. For the cored cable: the core material was 316 S.S, the core was centered and had a width of 10.8mm, the cable was keystoned with a 0.95 degree angle, and the strands were OST-RRP with a 1.0mm OD and 60 filaments. For the un-cored cable: the cable wasn’t keystoned and the strands were OST-RRP with a 1.0mm OD and 60 filaments. All samples were reacted under 20 MPa and one of each sample was epoxy impregnated using standard magnet protocols. Current was injected into a single strand at varying I/Ic and a heat pulse from a carbon paste heater was used to initiate current sharing. Current-distribution was measured using voltage taps. The ICR for the un-cored cable was less than that of the cored cable and the current sharing was greater for the un-cored cable. These measurements were performed as a screening for cable and cable preparation protocol for larger scale measurements.

Speaker: Chris Kovacs (The Ohio State University)
• 220
Active acoustic quench detection for high-temperature superconductor wires and stacks

A robust detection of spontaneous quenching is essential for protecting superconducting magnets and machinery from thermal damage. In coils of high-temperature superconductors (HTS) slow propagation of the normal zone makes common voltage-based quench detection schemes unreliable. Here, we propose and validate an alternative quench detection technique for HTS conductors based on monitoring their internal temperature with acoustic waves. Periodic pulsed excitation is applied using a piezo-transducer to a conductor or coil under test, and the transient mechanical response is recorded, providing a unique acoustic "fingerprint" of the system. Temperature-induced variations of the Young's modulus of <0.01% can then be readily detected by comparing the transient waveform to its undisturbed reference. We demonstrate by simulations and experiments a capability to resolve a temperature rise of < 1 K in the conductor quenching inside a stack at 77 K, on par with voltage detection at 1 microvolt/cm. Acoustic quench detection in a single 120 cm-long HTS conductor at an equivalent voltage sensitivity of 10 microvolt/cm is also demonstrated. The technique is simple, non-invasive, and applicable to a wide range of superconductor devices and beyond where thermal monitoring of interior of a solid object is required.

Speaker: Maxim Marchevsky (Lawrence Berkeley National Laboratory)

Conveners: Dr Jacob Kephart (Navy Ships Systems Engineering Station (NAVSSES)) , Jennifer Marquardt (Ball)
• 221
Air Liquide Turbo-Brayton refrigeration system commissioning

Air Liquide Advanced Technologies started the development of Turbo-Brayton refrigerators with the goal to have a reliable, plug and play, maintenance-free and efficient solution, introducing oil-free centrifugal compression and single skid system. These refrigerators are able to cover a wide range of temperature between 35K and 150K. This product is particularly adapted for High Temperature Superconductivity refrigeration at 65-70K. The development of HTS cables technology and the market growing will lead to the need for higher cold power as the length of the cable is increasing. This is why the range has been extended and new products are now available, going from 7 to 50kW@77K. As an illustration of this need, 20kW@70K are requested for the ComEd project in Chicago and a TBF-350 unit will be delivered in 2017. The first TBF-350 was manufactured and tested in June 2016. A complete test protocol was defined and this paper presents the commissioning results of the refrigerator.

Speaker: Cecile Gondrand (Air Liquide Advanced Technologies)
• 222
Superconducting transmission line for power distribution

A superconducting transmission line is being developed for applications requiring distribution of electric power among a number of locations along its length.

Speaker: Peter McIntyre (Texas A&M University)
• 223
Computational Electro Dynamic (CED) Analysis to Estimate the AC losses in High Temperature Superconducting Cables

AC losses are inevitable to be considered for effective design of High Temperature Superconducting (HTS) cables. Various analytical techniques are available to estimate these AC losses however not sufficient to accurately predict the same. Hence, computational methods are being widely used in the prediction of AC losses as the experimental techniques are complicated to be implemented. YBCO (Tc=90K @ 0T) and BSCCO (Tc=110K @ 0T) are generally used in the construction of HTS cables. However, the critical temperature reduces as the external magnetic field is experienced by the tapes increases giving lower temperature margin for cooling purposes. In the present work, Computational Electrodynamics (CED) is used to predict the AC losses in coated conductors (Second Generation) HTS tapes used in constructing the HTS cables. These losses which are dissipated as heat must balanced by the cooling the requirements. The effect of external magnetic field on the degradation of critical current is examined. Finite Difference Time Domain (FDTD) approach is used for discretization of governing equations in solving for the AC losses. Further, electric field distribution in coated conductors due to the applied magnetic field is investigated. Hence, the results of the present analysis guide the thermohydraulic design of HTS cables.

Speaker: Mr Mohit Kalsia (Lovely Professional University)
• 224
Effect of electrical breakdown on critical current of second generation HTS tapes

Typically high temperature superconducting (HTS) cables utilize solid dielectric materials such as PPLP and Cryoflex for electrical insulation layer. A solid dielectric is destroyed once an electrical breakdown has occurred. However, a gaseous dielectric design retains the same dielectric strength once breakdown has occurred. Research at the Center for Advanced Power Systems (CAPS) has focused on developing a gaseous helium (GHe) cooled HTS cables in which GHe acts as the sole dielectric material. To assess the ruggedness of gas insulated HTS cables against multiple breakdown events, it is necessary to assess the effect of breakdown events not just on the gaseous insulation medium, but also on the HTS tapes. It was therefore decided to study the effect breakdown events on the critical current of HTS tapes. The superconductive layer only represents approximately 1% of the total crossection of a typical second generation HTS tape. Studies have been performed on the critical critical current of HTS tapes before and after breakdown events. The ability of a HTS cable to be suitable for operation after multiple electrical breakdown events is an important characteristic of a superconducting gas insulated cables. This paper will present the details of the breakdown experiments performed and their effect on the critical current of several types of commercially produced HTS tapes. This work is funded by the Office of Naval Research.

Speaker: Peter Cheetham (Center for Advanced Power Systems)
• 225
Recent Progress of HTS Application Prototypes in JST/Strategic Innovation Program

In the stage Ⅲ(2016 – 2018) of JST/Strategic Innovation Program, 4 teams are developing HTS application prototypes to demonstrate to verify fundamental component technologies such as DC power cables for railway, compact accelerator magnets, high field NMR systems, and SQUID systems. Main targets of this program are to establish fundamental component technologies for each application and to demonstrate prototypes incorporating these technologies.
Typical achievements to date are as follows;
(1) Design of HTS DC cables for railway application and demonstration of application of HTS DC cable in a commercial railway was tried.
(2) Prototype of HTS model magnet for accelerators have been developed.
(3) High-field NMR system have been developed, including high sensitive probe and compact NMR magnets using HTS materials.
(4) HTS SQUID systems for medical and biotech have been developed.

Details of R&D achievements will be introduced.

Speaker: Dr Kenichi Sato (Japan Science and Technology Agency)
• C2OrB - Expanders, Pumps, Compressors and Regenerators Madison Ballroom BC

Conveners: Alexander Martinez (FNAL) , William Soyars (FNAL)
• 226
Commissioning of multistage cold compressor systems

Refrigeration at 2 K and below has become the new standard in cryogenically cooled particle accelerators. Up to four cryogenic turbo compressors need to be operated in series in order to reach the required sub-atmospheric helium bath pressure. Such highly developed systems shall operate at high reliability not interrupting the entire research facility. Linde Kryotechnik successfully supplied several cold compressors over the last 20 years. This long experience is the basis for a deeper understanding of the behavior of such sophisticated systems. Typical process arrangements for transient and part load operation, optimized control concepts as well as potential risks and corresponding mitigation measures will be discussed.
Together with the unique in-house developed control logics for multistage cold compressors these machines present a fully packaged solution for highly efficient and reliable refrigeration at 2 K and below.

Speaker: Mr Lutz Decker (Linde Kryotechnik AG)
• 227
Integration of Prototype Cryoviscous Compressor into SNS Cryogenic Test Facility for Demonstration Performance Characterization

In order to effectively characterize the performance of the cryo-viscous compressor (CVC) prototype, supercritical helium (SCHe) was required in order to mimic the conditions that the CVC would see in its installation site at ITER. Given the specific requirements for SCHe (2.0 g/s, 4.5 K, and 3.0 bara), a collaboration between US ITER and the Spallation Neutron Source Research Accelerator Division cryogenic group resulted in the utilization of existing infrastructure, the Cryogenic Test Facility (CTF), to achieve these conditions. While the CTF is normally used in superconducting radio frequency R&D, it has the ability to provide two distinct SCHe flows with a total flow rate of 10.0 g/s, temperatures near 4.5 K, and at pressures approaching 6 bar. A network of vacuum jacketed transfer lines piping and flow control interfaces was designed, fabricated, and installed to supply 2.0 g/s of SCHe to the CVC, while utilizing the remaining SCHe as a shield supply to minimize heat load to the supply and provide a 100 L liquid He precooler to reduce the supply temperature. A description of the individual components and their performance in the successful demonstration testing of the CVC will be presented.

This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan. The views and opinions expressed herein do not necessarily reflect those of the ITER Organization.

Speaker: Robert Duckworth (Oak Ridge National Laboratory)
• 228
Full-Scale Prototype Cryoviscous Compressor Demonstration at SNS Cryogenic Test Facility for ITER Vacuum System

To effectively process the mixed exhaust from the regeneration of the ITER torus cryopumps, a cryo-viscous compressor (CVC) prototype has been designed, fabricated, and subjected to successful performance testing. This testing, which was performed at the Spallation Neutron Source Cryogenic Test Facility, involved cooling a set of twenty-four 5-cm diameter, 1.27-m long stainless steel tubes with embedded static mixer flow enhancements with supercritical helium (SCHe) at flow rates between 1.0 g/s and 8.0 g/s, supply temperatures near 5 K, and supply pressures near 2.6 to 2.7 bara. The CVC prototype was able to cryopump deuterium at all SCHe flow rates from helium/deuterium process gas mixtures at helium percentages between 0.1% and 2.0% and at peak process gas flow rates up to 366 Pa-m3/s (0.6 g/s). Once the deuterium was cryopumped, regeneration operations were completed over a 15 to 20 minute period through the introduction of 30 K “warm” He gas to remove the deuterium from the CVC. In addition to the functional responses of the CVC prototype, performance considerations for the CVC once installed within the ITER vacuum system are presented.

This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan. The views and opinions expressed herein do not necessarily reflect those of the ITER Organization.

Speaker: Robert Duckworth (Oak Ridge National Laboratory)
• 229
Available Pressure Ratio of A Linear Compressor Based on Mechanical Phasor Model

The linear compressor for cryocoolers possesses the advantages of long-life operation, high efficiency, low vibration and compact structure. It is significant to study the match mechanisms between the compressor and the cold head, which determines the working efficiency of the cryocooler. However, the output characteristics of linear compressor are complicated since it is affected by many interacting parameters. The existing matching methods are simplified and mainly focus on the compressor efficiency and output acoustic power, while neglecting the important output parameter of pressure ratio. In this study, a mechanical phasor model basing on analyzing the forces of the piston is proposed. It can be used to predict not only the output acoustic power, the efficiency, but also the pressure ratio of the linear compressor. Calculated results agree well with the measurement results of the experiment. By this phasor model, the theoretical maximum output pressure ratio of the linear compressor can be calculated simply based on a known charge pressure and operating frequency. Compared with the mechanical and electrical model of the linear compressor, the new model can provide an intuitionistic understanding on the match mechanism with faster computational process. The model can also explain the experimental phenomenon of the proportional relationship between the output pressure ratio and the piston displacement in experiments. By further model analysis, such phenomenon is confirmed as an expression of the unmatched design of the compressor. The mechanical phasor model may provide an alternative method for the compressor design and matching with the cold head.

Speaker: Mr Chaoxiang Duan
• C2OrC - Safety Hall of Ideas - GJ

Hall of Ideas - GJ

Conveners: Wesley Johnson (NASA / GSFC) , John Jurns (European Spallation Source ERIC)
• 230
Safety Studies on Vacuum Insulated Liquid Helium Cryostats

The loss of insulating vacuum is often considered as a reasonable foreseeable accident for the dimensioning of cryogenic safety relief devices. The cryogenic safety test facility PICARD was designed to investigate such events. In the course of first experiments, discharge instabilities of the spring loaded safety relief valve occurred, the so-called chattering and pumping. These instabilities reduce the relief flow capacity, which leads to impermissible over-pressures in the system. The analysis of the process dynamics showed first indications for a smaller heat flux at opening pressure than the commonly assumed 4 W/cm2, resulting in an oversized discharge area for the correspondingly reduced relief flow rate.
This contribution presents further experimental investigation, where the insulating vacuum was vented with atmospheric air under variation of the venting diameter, the size and the set pressure of the safety relief valve and the helium filling level. Based on dynamic process analysis, the results are discussed in terms of effective heat fluxes and operating characteristics of the spring-loaded safety relief valves.

Speaker: Christina Weber (Karlsruhe Institute of Technology)
• 231
Relief device sizing for helium and hydrogen applications

The sudden loss of insulating vacuum is a potentially severe event to be considered in the safety analysis of cryogenic applications. When insulating vacuum is broken, large heat fluxes can heat up and expand cryogenic fluids inside the vacuum-insulated apparatus in a very short time.
The effect is particularly pronounced in applications involving helium, hydrogen and neon at temperatures below the condensation temperature of air, where air condensation on the cold surfaces leads to instantaneous peak heat fluxes that have been reported to be on the order of tens of kilowatts per square meter in some cases.
The effect is currently being investigated at several institutions worldwide. However the incorporation of the vacuum loss scenario into the safety design, and particularly the sizing of relief devices of cryogenic apparatus based on existing norms and standards, is not immediately obvious. We take a look at existing norms and present a way forward which we consider to be prudent and appropriate.

Speaker: Mr Rainer Soika (Linde Kryotechnik AG)
• 232
Cryogen Risk Assessment in Underground Mining

Reclassification of diesel engine exhaust as a carcinogen, has led to the mining industry exploring zero-emission alternatives to power underground mining equipment. Most interest lies with electric driven mining machines, however a new possibility is engines fueled with cryogens. This research conducts a formal risk assessment for cryogenic fueled equipment in underground environments. These include fans, load haul dump units, and trucks. The motivating advantage is zero-emissions production in the subsurface and simultaneous provision of cooling for ultra deep mine workings. The driving force of the engine is the expansion of the reboiled cryogen following flash evaporation using ambient temperature heat. The cold exhaust mixes with warm mine air and cools the latter further. The use of cryogens as 'fuel' leads to much increased fuel transport volumes and motivates special considerations for distribution infrastructure and process including: cryogenic storage, distribution, handling, and transfer systems. Detailed specification of parts and equipment, numerical modelling and preparation of design drawings are used to articulate the concept. The conceptual design process reveals new hazards and risks that the mining industry has not yet encountered, which may yet stymie execution. The major unwanted events include the potential for asphyxiation due to oxygen deficient atmospheres, or physical damage to workers due to exposure to sub-cooled liquids and cryogenic gases. The Global Minerals Industry Risk Management (GMIRM) framework incorporates WRAC and Bow-Tie techniques and is used to identify, assess and mitigate risks. These processes operate upon the competing conceptual designs to identify and eliminate high risk options and improve the safety of the lower risk designs.

Speaker: Mr Justin Sivret (Laurentian University / MIRARCO)
• 233
Cryogenics for Mining Safety

In the event of an underground mine emergency that makes the ambient air irrespirable, mineworkers need to use Self-Contained Breathing Apparatus (SCBA) for escaping or to be rescued, and if trapped, be provided with breathable air to sustain life in shelters termed Refuge Alternatives. NIOSH explored cryogenic technologies for these applications and with the help of NASA built Cryogenic Breathing Apparatuses (CryoBA) for continued escape, Air Storage and Filling Stations (CryoASFS) for refilling CryoBAs along the escape route, Refuge Alternative Storage Systems (CryoRASS) for life support and cooling and a Liquid Oxygen Kit (LOXK), for closed circuit long duration rescue breathing apparatuses. The prototypes developed are described in this presentation together with their design specifications. Two versions with single and twin dewars of the CryoBA, which are open-circuit SCBA were built with refilling capability via a CryoASFS while being worn on the user’s back. The CryoASFS and CryoRASS stored the cryogen in large dewars, preventing commodity loss before use by employing cryocoolers in their designs. The CryoRASS employs a delivery module that recirculates and adds breathing gas within and into the shelter, while providing cooling inside it including removing moisture. The prototypes functioned well and were demonstrated on the surface and underground. The cryogenic SCBA prototypes were shown to be capable of meeting performance standards for subsequent approval of production grade units for underground mine use in USA. One manufacturer has shown an interest towards producing the CryoBA and CryoRASS and getting the respective approvals.

Speaker: Mr Rohan Fernando (CDC-NIOSH)
• 234
Cryogenic safety in helium cryostat at CERN

Cryostats contain large cold surfaces, cryogenic fluids, and sometimes large stored energy (e.g. energized magnets), with the potential risk of sudden liberation of energy through thermodynamic transformations of the fluids, which can be uncontrolled and lead to a dangerous increase of pressure inside the cryostat envelopes. The consequence, in the case of a rupture of the envelopes, may be serious for personnel (injuries from deflagration, burns, and oxygen deficiency hazard) as well as for the equipment. Performing a thorough risk analysis is an essential step to identify and understand risk hazards that may cause a pressure increase and in order to assess consequences, define mitigation actions, and design adequate safety relief devices to limit pressure accordingly. Lessons learnt from real cases are essential for improving safety awareness for future projects. We cover in this paper our experience on cryostats at CERN and the design-for-safety rules in place.

Speakers: Yann Leclercq (CERN) , Vittorio Parma (CERN)
• M2OrC - Focused Symposia - Propulsion VI: Motors & Generators, Cryocool Technologies Lecture Hall

Lecture Hall

Conveners: Masataka Iwakuma (Kyushu University) , Teruo Izumi (AIST)
• 235
[Invited] Development of Superconducting PM Machines

High-temperature superconducting (HTS) materials offer a mature core-technology for propulsion motor/generators in transportation. In Japan, 1-3 MW synchronous motors for ship propulsion have been developed by industry-national institute-academia liaison using HTS wires. As alternative choice for field poles, melt-growth bulk HTS provides a successful design and making of prototype modules for 10-30 kW rotating machines. An effective magnetization for the HTS bulks is a key to achieving a high magnetic flux density, which provides a superior field pole compared with conventional machines. For practical applications, the pulsed field magnetization (PFM) after cooling below Tc continues to be developed to attain a compact fixture. Employing several milliseconds rise time and a duration of four seconds with a waveform control made by active feedback of the Hall sensor voltage as a function of time, the HTS bulk traps a high magnetic flux density that exceeds 90 % of that obtained by conventional and slow field cooled magnetization. In a rotating machine application, the design of the armature/magnetization coil must meet the requirements of the field-pole bulks and be compact and light weight. In contrast to HTS tape-wound coils, using either 1G and/or 2G wires, active control of the magnetic flux generated by dc pulsed current control can be accomplished by applying complementary magnetization or demagnetization. Research also continues on the magnetic flux dynamics towards an optimum set of PFM parameters. A Neon thermosyphon cooling has been applied to enhance and control useful field pole strength. In large output power applications, such as wind/ocean renewable energy generators and ship/aeronautic propulsion motors, these machines are highly desirable because of their potential for high energy density per weight/volume. In this paper, we review the current status, and the worldwide progress with the development of superconducting PM machines.

Speaker: Mitsuru Izumi (TOKYO UNIVERSITY OF MARINE SCIENCE AND TECHNOLOGY (TUMSAT))
• 236
AC Loss Analysis in Fully Superconducting Machines

Superconducting electric machines have shown potential for dramatic increases in power density for applications such as offshore wind generation, marine propulsion, and turbo-electric distributed aircraft propulsion. Superconductors exhibit zero loss when in dc conditions, though ac current produces considerable loss due to hysteresis, eddy currents, and coupling. For this reason, many present machines are designed to be partially superconducting, meaning that the dc field components are superconducting while the ac armature coils are normal copper conductors. Fully superconducting designs can also provide increases in power density due to a significantly higher peak armature current; however, ac loss analysis is then required to determine the feasibility of the machine’s intended operating conditions.

This research aims to characterize the expected losses in a fully superconducting machine targeted towards aircraft, whose design is based on an actively-shielded, partially superconducting machine from prior work. Various factors are examined such as magnet strength, operating frequency, temperature, and machine load to produce a model for the loss in the superconducting components of the machine. This model is then used to optimize the design of the machine for minimal ac loss while maximizing power density.

Speaker: Mr Matthew Feddersen (University of Illinois, Urbana-Champaign)
• 237
Present Status of Turbo-Brayton Cycle Cooling System in Japan

High temperature superconductive (HTS) power machines, such as a power cable, a transformer and a fault current limiter, have been tried to approach commercialization recently. In commercializing of HTS power machines, a cooling system shall have cooling capacity from 2kW to 10kW at 70 K, long maintenance interval and high efficiency (low input power). The HTS power machines are cooled by circulating of sub-cool liquid nitrogen and returned liquid nitrogen from HTS power machines will be cooled down using refrigerator. There are few kind of refrigerator for cryogenic field. A Stirling cycle refrigerator and a turbo-Brayton cycle refrigerator will be candidate to cool HTS power machines.
Taiyo Nippon Sanso Corporation had been developed a 2kW class turbo-Brayton cycle refrigerator in NEDO project from FY 2008 to FY 2012. The 2kW refrigerator is using Neon gas as working fluid. And an active magnetic bearing was adopted for turbo-compressor and turbine of the refrigerator. That is one of an advantage for applying HTS power machines. Because the magnetic bearing can levitate the shaft of the turbo machines therefore the refrigerator can become long term maintenance interval. After developing of 2kW refrigerator, 10kW turbo-Brayton refrigerator also has been developed for long length HTS power cable. Two types of refrigerator have operation experience about one year in field test.
Present status and technology detail of turbo-Brayton cooling system will be introduced in this presentation. And also subjects of turbo-Brayton cooling system for applying to electric propulsion aircrafts will be discussed.

Speaker: Hirokazu Hirai (Taiyo Nippon Sanso Corporation)
• 238
Updated Survey of Cryogenic Cooling Technologies for Superconducting Power Systems

As useful applications for superconductors continue to expand, required cooling methods still tend to be custom tailored for each application. The performance, capabilities, and economies of varying cryogenic cooling options are therefore an important concern for machine designers and end users. Features that are critical in the initial design and must be included in trade-offs when analyzing the options include many criteria, including weight, size, geometry, capacity at temperature, cooling rate from ambient, sensitivity to the environment (gravity, vibration, motion etc..), machines lifetimes, and also machine acquisition and lifetime costs. Since weight is critical for air and space applications, and short mission cycles from minutes to days are typical, different options for cooling need to be considered, including liquids with freezing points from 112K (natural gas), to 20K (liquid hydrogen), to 4.2K liquid He, and hybrid systems incorporating cooled liquids as upper reservoirs with multi-stage cryocoolers for lower temperatures. Solid-cryogens are also of interest for short-missions. AFRL is interested in cutting edge applications incorporating both low- and high-temperature-superconductors (LTS and HTS), and therefore has great interest in a broad range of cryocooling capabilities.
Herein we present a survey and comparison of cryocooling technology options, including traditional mechanical cryocoolers, and also properties of liquid cryogen cooling storage and liquification technologies. Efforts are made to include the parameters critical for aerospace systems, and transient missions. While many reviews are available in the literature, they do not always consider specific masses for varying machine input powers. Also updates for cryocooler technologies will be provided, for a limited survey.

Acknowledgements: Air Force Office of Scientific Research (AFOSR) and The U.S. Air Force Research Laboratory, Aerospace Systems Directorate (AFRL/RQ)

Speaker: Michael Susner (Air Force Research Laboratory)
• 239
Overview of Cooling Technologies for Cryogenic Transportation Machines

The authors give an overview of cooling technologies for cryogenic transportation machines that are most promising, followed by a brief survey and analysis in which way commercially available cryocoolers could be applicable.

Speakers: Wolfgang Stautner (GE Global Research) , Timothy Haugan (U.S. Air Force Research Laboratory)
• M2OrD - HTS and LTS Cables II Hall of Ideas - EH

Hall of Ideas - EH

Conveners: Sastry Pamidi (CAPS / FSU) , Herman Ten Kate (CERN)
• 240
Development of 2G HTS wire production at SuperOx

This talk will review the status of 2G HTS wire production and integration at SuperOx, with an emphasis on the recent facility expansion at the Moscow location.

As of January 2017, full production cycle of 2G HTS wire has been established at SuperOx in Moscow. This includes the commissioning of a new buffer deposition line in January 2016 and of a new PLD-HTS deposition system in December 2016. These new facilities were installed in addition to the similar existing production facilities at SuperOx Japan LLC, which remain in operation. The expansion essentially doubled 2G HTS wire production capacity of the SuperOx group of companies. The wire produced at both locations is of identical high quality.

We will also present an overview of our industrial R&D programmes run in parallel with wire production, which are aimed at improving the wire performance in magnetic field, optimising buffer layer architecture, expanding the range of customisation options, etc.

In addition to the HTS material production, SuperOx has been developing HTS devices such as cables, fault current limiters, coils, rotating machines, current leads, and 2G HTS composite bulk. Examples of the SuperOx HTS device activities will be given in the talk.

Speaker: Dr Alexander Molodyk (SuperOx)
• 241
[Invited] Intermediate Roebel cable lengths as a first HTS cable used in the HTS demonstrator accelerator type coil.

REBCO coated conductors are produced nowadays in lengths long enough for first demonstrative applications. Due to that also several HTS cable concepts are being developed, as Roebel Assembled Coated Conductor (RACC) cable, Coated Conductor on Round Core (CORC) cable and diverse stack cable concepts.
Approaching demonstrative applications, middle lengths of the RACC cable need to be assembled and supplied. Going from short length (couple of meter) to intermediate lengths (∼ 30 m) is a significant development step due to coated conductor geometrical inhomogeneity’s and strand forming technology issues. Up to now in the HTS cable development the focus is mostly on critical current (Ic) requirements. Thinking about long length not only Ic criteria but also geometrical homogeneity and superconducting properties homogeneity across and along the tape need to be taken into account.
Thanks to EU project EuCARD2 and its ‘’future magnets’’, development task for HTS magnets for accelerator use the cable development is pushed forward. Such accelerator focused demonstrators need customized intermediate HTS cable length which were prepared by advanced routes and supplied for coiling.
The crucial steps from short lengths of the RACC cable (below 6 m) towards intermediate lengths (∼ 30 m) will be addressed in this contribution. Geometrical irregularities of the coated conductor will be quantified, qualified and compared with RACC strand inconsistency. Internal tape inequalities of the critical current will be quantified and qualified using transport methods as well as induction measurement methods. A new punching tool for strand preparation in collaboration with CERN designed on basis of the collected experience led to significantly improved strand performance. First results with the impact on the cable performance will be shown.

Speaker: Dr Anna Kario (Karlsruhe Institute of Technology, Institute for Technical Physics)
• 242
New ReBCO-CORC Cable-In-Conduit Conductors for 80kA@12T/4K with stainless steel and copper jackets for use in Fusion and Detector Magnets

Two new ReBCO-CORC based Cable-In-Conduit Conductors are developed by CERN in collaboration with ACT-Boulder. Both conductors feature a critical current of about 80 kA at 4.5 K and 12 T. The first conductor is designed for operation in large detector magnets, while the second is aimed for application in fusion type magnets. The conductors are using the six-around-one cable geometry with six flexible ReBCO CORC strands twisted around a central tube. Each cable comprises six CORC strands each having 42, 4mm wide Superpower SCS4050 tapes with a 5 µm copper layer for a total of 252 tapes per conductor. The cable layout in both conductors is practically the same but they feature different jacket material and cooling mode. Detector type magnets require stable, high-current conductors and conduction cooling is highly preferred for its simplicity. Therefore, this CORC Cable-In-Conduit Conductor comprises an OFHC copper jacket with external conduction cooling. Contrary the heat load on most superconducting magnets in a fusion plant is too high for allowing a conduction cooled conductor. Therefore, the second conductor has internal forced flow cooling through the central tube and voids between the CORC strands. In addition, the cable is enclosed by a stainless steel jacket to cope with the high level of Lorentz forces in such magnets. A 2.8 m long sample of each conductor is manufactured and prepared for testing in the Sultan facility at PSI Villingen. In the paper the conductor design and assembly steps for both record size CORC type Cable-In-Conduit Conductors is highlighted.

Speaker: Tim Mulder (CERN / Twente Technical University (NL))
• 243
Transposed, high current HTS cables made with reinforced, narrow Bi2212 wire

A Bi2212-based rectangular wire approach has been developed, with up to 400 MPa stress tolerances and useful current densities for building transposed cables that are problematic with wide HTS tapes, and that need to operate beyond the field and temperature limits of low temperature superconductors. We are applying this recently established Bi2212-wire capability to develop robust, transposed, HTS cables for use in winding large, relatively low inductance magnets where ramped- or ac-field conditions require narrow, low-loss wires in transposed, high winding current, cabled configurations. As a first step, we modified a commercial, planetary 6-strand machine for cabling our wires with thicknesses / widths in the 0.5 – 1 mm / 0.8 – 2 mm ranges. The operational capability of the setup, as well as settings and calibrations were established using copper wires with similar dimensions to our Bi2212 wires. Bend tests of the reinforced Bi2212 wires in their pre-reacted conditions also demonstrated that they could be edge bent to ~1 cm diameter without indications of damage, and following reaction after bending, without adverse effects on Ic / Je, thereby underpinning our development objectives. Subsequently, transposed 6-wire samples were cabled to an ~ 4.5 cm pitch length using wires in their pre-reacted conditions. The cables exhibited flat top and bottom surfaces, without indications of wire damage. Bend tests indicated that they could be bent to minimum diameters of about 5 cm, and as a result a number of 6 cm inner diameter initial test coils have been produced, followed by reaction to form high Jc 2212. Ic test data demonstrated that they exhibited very useful transport current density levels. These results pave the way towards development of first-of-their-kind, transposed, robust, high-current, narrow-wire HTS cables that are of interest for winding some advanced particle accelerator and fusion reactor development magnets.

Speaker: Dr Alexander Otto (Solid Material Solutions, LLC)
• 244
Canted-Cosine-Theta accelerator magnets wound from high-temperature superconducting CORC® magnet wires

Advanced Conductor Technologies is developing high-temperature superconducting Conductor on Round Core (CORC®) magnet wires, wound from REBCO tapes with 30 μm thick substrates, for use the accelerator magnets. Round, isotropic CORC® wires of 3-4 mm thickness could offer operating currents in excess of 10,000 A and engineering current densities Je of over 600 A/mm2 at 4.2 K and 20 T, while allowing bending to diameters below 50 mm. CORC® wires are a very attractive candidate for use in Canted-Cosine-Theta (CCT) magnets in which the dipole field is generated by winding an even number of layers at opposite tilt angles.
Lawrence Berkeley National Laboratory is developing magnet technologies for dipole fields beyond 16 T by combining a CCT outsert, wound from low-temperature superconductors, with a CCT insert wound from high-temperature superconductors. Here we focus on insert magnets based on the CORC® wires. The CCT insert magnet will be developed in several steps, including a double-layer, 40 turn per layer CCT magnet (C1) wound from CORC® wires containing 16 superconducting tapes and a 4-layer, 40 turn per layer CCT magnet (C2) wound from high-Je CORC® wires containing 29 tapes. The results of two double-layer, 3-turn, sub-scale CCT magnets containing CORC® wires with the C1 and C2 architecture, and that of CCT magnet C1 wound from a total of 40 meters of CORC® wire are presented. The dipole field in the magnet aperture was measured in self-field in liquid nitrogen and liquid helium up to the critical current. The results show a clear path forward to achieve at least 5 T in the CCT insert magnet that would operate in a background field of 15 T resulting in a total field of 20 T.

Acknowledgement

This work was supported by the US Department of Energy under agreement numbers DE-SC0009545, DE-SC0014009, DE-SC0015775 and DE-AC02-05CH11231.

Speaker: Danko van der Laan (Advanced Conductor Technologies)
• 12:30 PM
Poster Session Lunch (12:30 - 1:00 p.m.) Cryo Expo, Exhibit Hall AB

Cryo Expo, Exhibit Hall AB

• C2PoK - GM, VMPT, Stirling and JT Coolers (Non-Aerospace) Exhibit Hall AB

Exhibit Hall AB

Conveners: Prof. Zhihua Gan (Zhejiang University) , Dr Chao Wang (Cryomech, Inc.)
• 245
Characteristics of a 1.6 W Gifford-McMahon cryocooler with a double pipe regenerator

This paper focuses on the second stage regenerator of a 4K Gifford-McMahon (G-M) cryocooler. A three-layer layout of lead (Pb), HoCu2 and Gd2O2S spheres in the second stage regenerator derives a good performance at the temperature of 4 K. From the latest test, we confirmed that the cooling power of 1.60 W at 4.2 K was achieved by using this three-layer layout. The two-stage G-M cryocooler is RDK-408D2 (SHI) and the compressor is C300G (SUZUKISHOKAN) with an electric input power of 7.3 kW at 60 Hz. In order to further improve, a new regenerator structure that was named a double pipe regenerator developed by Masuyama in 2016 was applied to the second stage regenerator. As a double pipe, a stainless steel pipe with thin wall was inserted in the coaxial direction into the second stage regenerator. The helium flow in the second stage regenerator is expected to be non-uniform flow because of the distribution of helium density and the imperfect packing of regenerator material. The double pipe regenerator is considered to have an effect which rectifies the helium flow. From the experimental result, the cooling power was improved by 1.67 W at 4.2 K. This result proves that the double pipe regenerator is an effective method to improve the cooling power.

Speaker: Prof. Shinji Masuyama (NIT, Oshima College)
• 246
Comparative Analysis of Linear motor geometry for a Stirling Cryocooler

Compared to rotary motor driven Stirling cryocoolers, linear motor coolers are characterized by small volume and long life, making them more suitable for space and military applications. The linear motor Stirling coolers are directly driven by a linear motor and both the components are integrated as a single unit. Therefore, the motor characteristics have direct effect on the operation of the cooler. In this context, plenty of scope exists in understanding the behavioral features of linear motor systems. In the present work, the authors compare and analyze the moving magnet linear motor with and without teeth to finalize the geometry suitable for the Stirling cryocooler. The required axial forces in the linear motors are generated by the current flowing in a magnetic field. The compact size, commercial availability of permanent magnets and low weight requirement of the system are quite a few constraints for the design. The finite element analysis using Maxwell software serves as the basic tool to analyze the magnet movement, flux distribution in the air gap and the saturation levels on the core. A number of material combinations are tried out for core before finalizing the design. The effect of varying the core geometry on the flux produced in the air gap is also analyzed. From the analysis, it is observed that the motor without teeth is advantageous over the motor with teeth in terms of effective utilization of magnetic flux in the air-gap in order to provide the required force.

Speaker: Dr Biju T Kuzhiveli (NIT Calicut)
• 247
Cooling Down Time Optimization of the stirling cooler

The cooling power of stirling cooler is the most important performance. But in some special field, for example in IR seek, the cooling down time was more important. Thus, it is a great challenge for improving cool down time of the stirling cooler. A new model SCI09H split Stirling linear cryogenic cooler was designed by us. A new structure of linear motor was used in the compressor, and the machine spring was used in expander. In order to reducing the cooling down time, the stainless steel mesh of regenerator is optimized. The cooler’s weight is 1.1 Kg, the cooling down time to 80K is 2 min at 23℃ with a 250J thermal mass, the cooling power is 1.0W at 80K, and the input-power is 60Wac.

Speaker: Dr Ming Xia (Kunming Institute of Physics)
• 248
Experimental progress of a 4K VM/PT hybrid cryocooler for pre-cooling 1K sorption cooler

Sub-kelvin refrigerator has many applications in space detector and manned space station, such as for the transition-edge superconducting (TES) bolometers operated in the 50 mK range. In order to meet the requirement of space applications, the high efficient, vibration free and high stability refrigerator need to be designed. VM/PT hybrid cryocooler is a new type cryocooler capable of attaining temperature below 4K. As a low frequency Stirling type cryocooler, it has the advantages of high stability and high efficiency. Combined with the vibration free sorption cooler and ADR refrigerator, a novel sub-kelvin cooling chain can be designed for the TES bolometer. This paper presents the recent experimental progress of the 4K VM/PT hybrid cryocooler in our laboratory. By optimizing of regenerators, phase shifters and heat exchangers, a lowest temperature of 3K was attained. Based on this cryocooler, a preliminary sorption cooler was designed and built.

Speaker: Dr Changzhao Pan (Technical Institute of Physics and Chemistry, CAS)
• 249
Liquid nitrogen cooling test with linear driven Stirling cryocooler

We have been developing large Stirling cryocooler for cryogenic cooling system of HTS electric power devices. The developed Stirling cryocooler is driven by a dual-opposed linear compressor and has a gamma-type configuration. Three Stirling cryocoolers are integrated to produce 2 kW of cooling capacity. The liquid nitrogen circulation loop is prepared to simulate the cooling system of HTS cable. The cold head of cryocoolers is designed and fabricated to remove heat from subcooled liquid nitrogen flow. The cooling capacity is measured from enthalpy difference between inlet and outlet of liquid nitrogen. In experiments, temperature and pressure at several points are measured as varying mass flow rate of liquid nitrogen. With experimental results, temperature distribution in cold-head, characteristics of heat exchanger for liquid nitrogen, and performance of liquid nitrogen pump are discussed.

Speaker: Dr Junseok Ko (Korea Institute of Machinery & Materials)
• 250
Mixture Optimization for Mixed Gas Joule-Thomson Cycle

An appropriate mixed gas fluid can provide lower temperatures and higher cooling power when used in a Joule-Thomson (JT) cycle than is possible with a pure substance. However, selecting gas mixtures to meet specific cooling loads and cycle parameters is a challenging design problem. Previous research at UW-Madison has been focused on developing computational tools that optimize compositions of gas mixtures for specific operating parameters. This study expands on prior research by exploring higher heat rejection temperatures, lower cold-end temperatures, and smaller recuperator sizes than previously investigated. A thermodynamic model of a mixed gas JT system has been developed and will be integrated with a mixture optimization model. This allows optimal mixture compositions and operating parameters to be determined for a mixed gas JT system with cold-end temperatures down to 110 K and hot-end temperatures above room temperature.

Speaker: Ms Jennifer Detlor (Solar Energy Laboratory)
• 251
Modelling of a stirling cryocooler regenerator under steady and steady - periodic flow conditions using a correlation based method

Regenerative heat exchanger is the most vital component in a Stirling cryocooler. The performance of the cooler depends on the thermal and hydrodynamic properties of the regenerator used in the system. The computational fluid dynamics (CFD) modeling is the best technique to design and predict the performance of a Stirling cooler. But the accuracy of the results depends on the hydrodynamic and thermal transport parameters used as the closure relations for the volume averaged governing equations. This paper proposes a new friction factor correlation based method to obtain the viscous resistance term D and the inertial resistance term C required for modeling the regenerator as a porous media using FLUENT. Using standard friction factor correlations, friction factor was obtained for flow of helium through different wire matrices and compared with the correlation proposed by Clearman et al. in terms of permeability and Forchheimer's inertial coefficient. Friction factor data obtained from Blass and Tong/London correlations are in agreement with that of Clearman et al. Viscous resistance term D and inertial resistance term C are calculated from this data and used to model the steady and oscillatory flow through the regenerator. Comparison of the predicted and experimental pressure drop reveals good predictive power of the correlation based method. For oscillatory flow, the predicted pressure amplitude and the phase at the regenerator exit are compared with the experimental data. The correlation based method could predict the pressure amplitude and the phase difference accurately. Using this method, Darcy permeability and Forchheimer's inertial coefficient are obtained for 200, 250, 300, 450 and 500 mesh regenerators. Parametric investigation was conducted on these regenerators under steady and steady - periodic flow conditions. The effect of different operating and geometric parameters on the performance of the regenerator are presented.

Speaker: Dr Biju T Kuzhiveli (Centre for Advanced Studies in Cryogenics (CASC), Department of Mechanical Engineering, National Institute of Technology Calicut, India ,673601)
• 252
Numerical Study of a Cryogen-free Vuilleumier Type Pulse Tube Cryocooler Operating below 10 K

This paper mainly presents a numerical investigation on a VM type pulse tube cooler. Different from previous systems that use liquid nitrogen, Stirling type precoolers are used to provide the cooling power for the thermal compressor, which offers the flexibility of changing working temperature range of the thermal compressor. Firstly, main component dimensions were optimized to achieve a lowest no-load temperature. Then the dependency of system performance on average pressure, frequency, displacer displacement amplitude and thermal compressor cold end temperature were studied. Finally, based on the simulation results, distributions of acoustic power, enthalpy flow, phase relationship between pressure wave and volume flow rate are presented. A lowest no-load temperature of 5.15 K was predicted with an average pressure of 2.5 MPa, a frequency of 3 Hz, displacer displacement amplitude of 6.5 mm, ambient end and cold temperature of 300 K and 90 K, respectively.

Keywords
VM type Pulse Tube Cryocooler; Thermal Compressor; Cryogen-free; Numerical Simulation

Speaker: Prof. Wei Dai
• 253
Numerical study of a novel coupled VM-PTC cryocooler with He3 as working fluid by Sage

Under the situation of sufficient heat energy and shortage of electric energy,the heat-driven refrigerators can exploit their advantages sufficiently. The experimental study of heat-driven coupled VM-PTC cryocooler with He4 has already obtained the on-load temperature blow 4K. For enlarging the application limits,the refrigerating capacity of VM-PTC cryocooler with He3 as the working fluid ,which has more potential physical properties,should be researched further. This paper bases on a VM-PTC model established by Sage software. In numerically study,the no-load temperature under different precooling temperature on intermediate cavity and heating temperature on hot cavity are considered. Also, the structure parameter of VM-PTC machine and its attachments are optimized by Sage. On the basis of above,the relationship between variable load and cold end temperature is studied at last.

Speaker: Dr Changzhao Pan (Key Laboratory of Cryogenics, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing, 100190, China)
• 254
Numerical study of a VM type multi-bypass pulse tube cryocooler operating at 4K

VM cryocooler is one kind of Stirling type cryocooler working at low frequency. At present, we have obtained the liquid helium temperature by using a two-stage VM/pulse tube hybrid cryocooler. As a now kind of 4K cryocooler, there are many aspects need to be studied and optimized in detail. In order to reducing the vibration and improve the stability of this cryocooler, a pulse tube cryocooler was designed to get rid of the displacer in the first stage. This paper presents a detail numerical investigation on this pulse tube cryocooler by using the SAGE software. The low temperature phase shifters were adopted in this cryocooler, which were low temperature gas reservoir, low temperature double-inlet and multi-bypass. After optimizing, the structure parameters and the best diameters of orifice, multi-bypass and double-inlet were obtained. With the pressure ratio of about 1.6 and operating frequency 2Hz, this cryocooler could supply above 40mW cooling power at 4.2K, and the total input power needs no more than 60W at 77K. Based on the highest efficiency of 77K high capacity cryocooler, the overall efficiency of this VM type pulse tube cryocooler is above 0.5% relative Carnot efficient.

Speaker: Dr Changzhao Pan (CAS Key Laboratory of Cryogenics, Technical Institute of Physics and Chemistry)
• 255
Performance estimation of an oil-less linear compressor unit for a new compact 2K Gifford-McMahon cryocooler

Since 2012, a new, compact Gifford-McMahon (GM) cryocooler for cooling superconducting single photon detectors (SSPD) has been developed and reported by Sumitomo Heavy Industries, Ltd. (SHI). It was reported that National Institute of Information and Communications Technology (NICT) developed a multi-channel mounted on a GM cryocooler of SSPD system. However, the size and power consumption reduction becomes indispensable to apply such system to the