3rd Workshop on Accelerator Magnets in HTS (WAMHTS-3)

10 Sept 2015, 14:00 → 11 Sept 2015, 19:45 Europe/Zurich

Roseraie 1 & 2 (Lyon Convention Centre)

We are pleased to announce the third workshop in the series, WAMHTS-3. This meeting will be held in Lyon, France, on 10 and 11 September 2015. It will immediately follow the closing of EUCAS’2015 and will be held in the same venue in order to facilitate participation. The workshop is organized by the EuCARD2-WP10 (Future Magnets) collaboration.

While WAMHTS-1 was dedicated to “Conductor” and WAMHTS-2 to “Coil Technology”, WAMHTS-3 will have a strong focus on “Magnet Protection”, though maintaining a broad overview of all general issues on HTS for accelerator magnets. It is the opinion of most designers that HTS materials ease magnet stability at the detriment of quench detection and, consequently, magnet protection. We intend to:

• review the various techniques for quench detection;
• assess the actual needs for accelerator magnets in terms of active protection and time scale;
• compare simulation codes and data on quench evolution measured in a suitable experimental set up and in real magnets.

The workshop will start on Thursday 10th September 2015 at 2 PM and will last until Friday 11th September at 5 PM. On Thursday afternoon we will review the status of conductor and magnet design options for the EuCARD-2-Future Magnets program, as well as the US and Japanese companion programs, which will provide the framework for the quench protection discussion. Friday will be fully dedicated to detection and protection issues. A workshop dinner is planned on the evening of Thursday 10th September, hosted by the workshop organisers. Participation in this event is by invitation only. People not having received an invitation and who wish to participate can contact the member of the IOC of their region.

Lucio Rossi, WAMHTS-3 Chair

Photos.7z

Thursday 10 September

14:00 → 15:50 EuCARD-2 "Future Magnets"

Convener: Philippe Fazilleau (CEA)

14:00 Welcome and scope of the workshop

Speaker: Lucio Rossi (CERN)

1 - Lucio Welcome Scope WAMHTS-3.pdf

1 - Lucio Welcome Scope WAMHTS-3.pptx

14:10 Characterization of EuCARD-2 first cables (20'+5')

Speaker: Luca Bottura (CERN)

status WP10.2.pdf

status WP10.2.pptx

14:35 Roebel cables for EuCARD-2: experience and options (20'+5')

A. Kario, S. Otten, A. Kling, A. Jung, B. Runtsch, R. Nast, W. Goldacker, Institute for Technical Physics, Karlsruhe, Institute of Technology, Karlsruhe In frame of EuCARD2 project WP10 HTS Roebel cables for accelerator magnet applications are developed. The Roebel coated conductor cable is foreseen as conductor for 5 T stand-alone magnet winding which will be also tested in background field up to 20 T. In such conditions as low temperature (4.2 K) and high background magnetic field, different aspects of the cable architecture need to be explored. Effects like defects in coated conductor itself macroscopically (width, flattens) and microscopically (non-superconducting phases) need to be taken into account. Burr caused by superconducting tape punching, additional defects coming from strand punching process like a delamination need to be taken into account and solved. In that talk we focus on different aspect of Roebel cable geometry and possible alternatives in Roebel geometry for EuCARD2 HTS magnet.

Speaker: Anna Kario (KIT)

WAMHTS3_Lyon_9092015.pdf

WAMHTS3_Lyon_9092015.pptx

15:00 EuCARD-2 baseline design: Aligned block design status (Feather M0/M2) (20'+5')

Speaker: Glyn Kirby (CERN)

WAMHTS 3 Lyon 2015.pptx

15:25 Alternative EuCARD-2 dipole designs: cos theta design and YBCO stack dipole status (20'+5')

In the EuCARD2 WP10 Future Magnets project an accelerator quality magnet has to be built with HTS conductors generating 5 T in stand-alone mode and as much as possible in insert mode to increase a 13 T background field. The baseline design is a block coil magnet made of Roebel cable under development at CERN. Nevertheless, two alternative designs are investigated: a cos-theta design with the same Roebel cable (CEA) and a block coil design with a conductor made of a stack of tapes (INPG). The presentation aims at providing the status of both of the alternative designs: Electromagnetic and mechanical analysis as well as magnet ends designs and very first results on dummy cable windings.

Speaker: Clement Lorin (CEA/IRFU,Centre d'etude de Saclay Gif-sur-Yvette (FR))

Lorin_Costheta-BlockINPG_WAMHTS3_10sep2015.pdf

Lorin_Costheta-BlockINPG_WAMHTS3_10sep2015.pptx

15:50 → 16:10 Coffee break

16:10 → 17:20 Accelerator Programs

Convener: Lucio Rossi (CERN)

16:10 Japanese HTS accelerator programs (25'+10')

Speaker: Toru Ogitsu

WAM-HTS3-ogts150910.pptx.pdf

16:45 US HTS accelerator programs (25'+10')

Speaker: Bruce Strauss

17:20 → 18:20 Criteria

Convener: Toru Ogitsu

17:20 HTS magnet quench experience (25'+10')

Comprehensive quench analyses of the NHMFL 32T all superconducting magnet. Our approach to a quench simulation, detection and protection of REBCO-coated-conductor-wound coils. A.V. Gavrilin, H.W. Weijers, D.K. Hilton, W.D. Markiewicz, P.D. Noyes, D.V. Abraimov, Z. Johnson, A. Khan, J. Lu, H. Bai, and M.D. Bird National High Magnetic Field Laboratory, Tallahassee, Florida, USA The National High Magnetic Field Laboratory (NHMFL) has embarked on an effort to build a unique all-superconducting DC magnet system to generate 32T. The system is envisioned to consist of a REBCO-coated-conductor/tape-wound two-nested-coil inner magnet (insert) and a multi-coil LTS outer magnet (outsert). The outsert is already built and tested by Oxford Instruments, and delivered to and installed at the NHMFL. The insert is under construction at the NHMFL. A complex approach to a quench modeling was developed and a sophisticated computer code for full-scale quench simulations of a magnet system consisting of a multi-coil REBCO insert and a multi-coil LTS outsert, with due regard for the electrical circuit complexity, was created at the NHMFL. Analytical models of the processes governing a REBCO magnet quench behavior have been developed and appropriately included in the code. A special attention was paid to modeling of the insert active and passive quench protection and quench detection systems’ operation and actual conductor/tape layout in the REBCO coils, along with many other aspects. The active protection system includes the tailor-made quench heaters to normalize promptly the winding in the event of quench. The layout was optimized to have high uniformity of the field and a desired margin from the quench protection standpoint. Also, it is worthy of note that the transport critical current dependence on the magnetic flux density orientation (“field angle”) was appropriately included. The dependence was measured at a number of fixed temperatures that enabled one to suggest a series of practical and convenient fit functions for the IC (versus the field magnitude, field angle and temperature data) [1] to be used in the quench simulations. The problems of AC losses, screening currents and LHe penetration in the insert winding are viewed as well, though some uncertainties and difficulties still exist here to be addressed and understood better further. Numerous quench test measurements on the insert prototypes helped us develop, verify, and adjust our approach to the quench modeling and enhance our understanding of the quench development phenomenon in REBCO coils in various case scenarios. [1] D.K. Hilton, A.V. Gavrilin and U.P. Trociewitz, “Practical fit functions for transport critical current versus field magnitude and angle data from (RE)BCO coated conductors at fixed low temperatures and in high magnetic fields”, Superconductor Science and Technology, Volume 28 , Number 7, 2015; available on-line: http://iopscience.iop.org/0953-2048/28/7/074002/article.

Speaker: Andrey Gavrilin (Florida State University, Florida, USA)

WAMHTS-3 Gavrilin.ppt

17:55 HTS magnet quench criteria (20'+5')

The protection of HTS magnets against quench and the induced damages is still considered as a key issue for HTS material use in reliable magnets. After a brief reminder about quench principle and the risk for HTS magnet, a way to improve the protection will be introduced from the adiabatic hot spot criteria. Examples of winding optimization for better detection and protection scheme for quicker dumping will be mentioned. The talk will finally introduce two magnet winding techniques under development for self- or nearly self-protecting HTS magnets.

Speaker: Thibault Lecrevisse (CEA)

WAMHTS-3_HTS-quench-criteria_final.pdf

WAMHTS-3_HTS-quench-criteria_final.pptx

18:20 → 21:20 Dinner at Le Caro restaurant in Lyon - buses depart directly from the Convention Centre at the end of the meeting

Friday 11 September

09:00 → 10:15 Detection

Convener: Bruce Strauss

09:00 Review of quench detection methods in superconducting magnets (20'+5')

This talk gives a summary of quench detection methods used so far in superconducting magnets, both in already operating facilities and in experimental test stations. An special emphasis will be given to quench detection issues in large scale, superconducting magnet machines like LHC and the future ITER. Results from experiments specifically designed for studies and from operational experience will be presented. Finally, potentials of the different methods in view of future applications to HTS magnets are briefly discussed.

Speaker: Felix Rodriguez Mateos (CERN)

Lyon_2015_FRM.pdf

Lyon_2015_FRM.pptx

09:25 A New Detection Method of Normal Transition in HTS Coils by using Poynting's Vector Method (20'+5')

Speaker: Akifumi Kawagoe (Kagoshima University)

presentation-kawagoe.pdf

presentation-kawagoe.ppt

09:50 Optical fibers for quench detection (20'+5')

Due to slow quench propagation, early quench detection remains an unresolved challenge for HTS magnets. An emerging new approach, co-wound optical fibers interrogated via Rayleigh scattering, offer very high spatial and temporal resolution and the ability to detect a disturbance before the hot-spot temperature exceeds the current-sharing temperature. This talk will review recent progress on this technique, discuss the remaining challenges and possible solutions.

Speaker: Justin Schwartz (NC State University)

Schwartz WAMHTS3 2015 FINAL.pdf

Schwartz WAMHTS3 2015 FINAL.pptx

10:15 → 10:35 Spot presentations

Convener: Luca Bottura (CERN)

10:15 Stress and strain evolution in a REBCO coated conductor and coil during a quench (10')

An electro-thermo-structural finite element REBCO coated conductors (CCs) model and a hybrid coil model wound with the REBCO CC are used to perform stress/strain analyses. The CC model includes all constituent layers, including the silver, REBCO and buffer layers, with temperature-dependent elastoplastic material properties in real dimensions. Each turn in the coil is wound independently under winding tension for realistic simulation. Static residual stresses induced by conductor fabrication, bending under winding tension and cooling are first calculated. Based on the residual stresses, stress/strain evolution induced by a quench are then studied. Critical stress/strain limits as failure criteria are used to predict potential failures induced by a quench.

Speaker: Wan Kan Chan

WAMHTS-3_2015_WanKan_V1.pdf

10:25 NZPV and MQE from the electrical and thermal properties of commercial REBCO tapes (10')

Marco Bonura and Carmine Senatore, University of Geneva. Normal zone propagation velocity (NZPV) and minimum quench energy (MQE) of REBCO coated conductors have been analytically estimated starting from an experimental characterization of the electrical (critical current) and thermal (thermal conductivity and specific heat) properties of the tapes. The study has been carried out on conductors produced by different manufacturers. The results obtained in the tape from SuperPower have been compared with experimental data from the University of Twente [J. van Nugteren, master thesis].

Speaker: Marco Bonura (University of Geneva)

Bonura_WAMHTS-3.pdf

10:35 → 10:55 Coffee break

10:55 → 12:20 Protection

Convener: Naoyuki Amemiya (Kyoto University)

10:55 Quench detection and protection for HTS accelerator magnets (20'+5')

Quench protection of the future HTS-based accelerator magnets is a challenging task. I will outline key differences between HTS and LTS conductors that impact their quench behavior, and show simulation results for the hot spot temperature and time margin in quenching HTS conductor using adiabatic approximation. Next, I will give an overview of the recently reported activities related to HTS quench detection and protection and compare existing approaches. Finally, I will propose a combined quench detection and protection technique for HTS accelerator magnets based on split conductor geometry.

Speaker: Maxim Marchevsky (Lawrence Berkeley National Lab. (US))

MM_WAMHTS3.pdf

MM_WAMHTS3.pptx

11:20 Optimisation of CLIQ for HTS (20'+5')

Speaker: Emmanuele Ravaioli (Twente Technical University (NL))

LightWeight - WAMHTS-3_CLIQonHTS_Ravaioli.pdf

LightWeight - WAMHTS-3_CLIQonHTS_Ravaioli.pptx

WAMHTS-3_CLIQonHTS_Ravaioli.pdf

WAMHTS-3_CLIQonHTS_Ravaioli.pptx

11:45 No protection device: non-insulated magnets (20'+5')

Speaker: Seungyong Hahn (FSU)

03[WAMHTS-3]Self-Protecting.NI.HTS.Magnets_20150911_SH2.pdf

03[WAMHTS-3]Self-Protecting.NI.HTS.Magnets_20150911_SH2.pptx

12:10 Report from WAMHTS-2 (10')

Speaker: Naoyuki Amemiya (Kyoto University)

Report_from_WAMHTS-2-Amemiya.pdf

Report_from_WAMHTS-2-Amemiya.pptx

12:20 → 13:50 Lunch Break - participants are invited by the organisers

13:50 → 14:15 Experiments

Convener: philippe fazilleau (cea)

13:50 Protection experience and HTS magnets at BNL (20'+5')

BNL has built a large number of HTS coils and magnets. This presentation will summarize the quench protection strategies and experience during the design and operation of those magnets. The presentation will also give update on the BNL HTS programs related to accelerator magnets.

Speaker: Ramesh Gupta (BNL)

wamhts-3-gupta-rev.pdf

wamhts-3-gupta-rev.pptx

14:15 → 15:05 Simulations

Convener: Lucio Rossi (CERN)

14:15 Current redistribution in cables and its influence on quench (20'+5')

Speaker: Jeroen Van Nugteren (Twente Technical University (NL))

WAMHTS Lyon 2015 JvN.pdf

WAMHTS Lyon 2015 JvN.pptx

14:40 Quench in a Pancake Wound Superconducting Coil with Low Resistance Between Turns (20'+5')

The introduction of no-insulation superconducting coils is a major development in the technology of superconducting magnets. NI coils are characterized by high current density compact coils that are also very stable. The high current density in the conductor makes it important to understand the quench behavior of these coils. Modeling of quench in a REBCO pancake wound test coil shows the onset and propagation of quench in a superconducting coil with low resistance between turns. The evolution of temperature, critical current, and internal distributed currents is observed.

Speaker: Denis Markiewicz

MarkiewiczWAMHTS3.mp4

15:05 → 15:15 Spot presentations

15:05 Quench studies in Bi-2212 coils (10')

Speaker: Tengming Shen (Fermilab)

Shen-WAMHTS.Lyon.2015.pdf

Shen-WAMHTS.Lyon.2015.pdf

Shen-WAMHTS.Lyon.2015.pptx

15:15 → 15:35 Coffee break

15:35 → 17:00 Simulations

Convener: Lucio Rossi (CERN)

15:35 The actual quenches of HTS coils (20'+5')

The presentation introduces actual quenches of HTS coils due to conductor degradation caused by thermal stress and electromagnetic force. Such a degradation leads to an irrecoverable thermal runaway, resulting in a catastrophic damage on the coil. NI method is a promising to protect HTS coils. The applicability of the method to pancake-winding and layer-winding is examined with experimental and simulated results. Based on those results, the HTS winding method strategies in the light of protection is discussed.

Speaker: Yoshinori Yanagisawa (RIKEN)

WAMHTS-3_yanagisawa.pdf

WAMHTS-3_yanagisawa.pptx

16:00 Finite Element Modelling of quench dynamics in 2G HTS coated conductors (25'+5')

Commercial second generation (2G) high temperature superconductor (HTS) coated conductors (CCs) possess a low normal zone propagation velocity (NZPV) in comparison with low temperature superconductor wires. One consequence of a low NZPV is that 2G HTS CCs must be over-stabilized in order to prevent the appearance of hot spots, which reduces their engineering critical current and their resistance per unit length. Recently, a tape architecture called “current flow diverter (CFD)” was proposed to enhance by orders of magnitude the NZPV of 2G HTS CCs [1]. In the CFD concept, the interfacial resistance between the HTS and silver layers is strongly increased at the center of the tape but kept low at the tape edges. The current flow is then diverted towards the tape edges when it transfers from the HTS layer to the stabilizer, which results in an important increase of the current transfer length and the NZPV, with only a minor impact on tape stability, characterized by the minimum quench energy (MQE). In this work, we developed an electro-thermal model using the finite element method to investigate the effects of various parameters, such as the temperature, critical current, stabilizer thickness, applied current, etc., on the performance of the CFD architecture in comparison with commercial 2G HTS CCs. Our results show that the CFD architecture increases the NZPV for the whole range of operating temperature considered (4 – 90 K). Also, we found out that the benefits of the CFD architecture, in terms of NZPV, are higher when the stabilizer is thinner and the critical current gets higher. An enhancement of the NZPV of more than two orders of magnitude is predicted for specific tape configurations. Finally, we compared our numerical results with experimental ones and discuss the possible improvements to the model in order to fully reproduce the experimental behavior of CFD tapes. The results are directly applicable to the design of more robust fault current limiters and magnet quench protection systems. (C. Lacroix, F. Sirois, J-H. Fournier-Lupien) [1] C. Lacroix and F. Sirois, « Concept of current flow diverter for accelerating the normal zone propagation velocity in 2G HTS coated conductors », (2014) Supercond. Sci. Technol., v27, p035003.

Speaker: Frédéric Sirois (Ecole Polytechnique de Montréal)

Lacroix_Sirois_WAMHTS_2015_public.pdf

16:35 Feather M2 quench modeling (20'+5')

EuCARD-2 project aims to construct an HTS dipole magnet producing 5 T with an accelerator magnet level coil current density. One main ingredient is the study of quench protection. First, prototype magnets are currently being constructed for quench detection experiments, later the final delivery must be characterized. Because of the high current density and high fraction of non-stabilizing material (substrate), quench protection is in essential role. In this talk we discuss about the quench onset heater design for the detection experiments and the quench analysis of the 5 T magnets - so called Feather-M2.

Speaker: Antti Aleksis Stenvall

stenvall-vrs150910.pdf

17:00 → 17:15 Closing