2M-LS-O2 Sep 8 - Morning (10:30-12:30 PM)
Large Scale - HTS magnets for high fields and accelerators
10:30 - 11:00 Design, construction and test of subscale coils with REBCO Roebel cable for the EuCARD-2 Future Magnets project|
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EuCARD-2 is a project partly supported by FP7-European Commission aiming at exploring accelerator magnet technology for 20 T dipole operating field. The EuCARD2 collaboration is closely liaising with similar programs for high field accelerator magnets in the USA and Japan. The focus of EuCARD2, through the work-package 10 “Future magnets”, is the development of a 10 kA-class superconducting, high current density cable suitable for accelerator magnets, to be used in a 5 T stand-alone dipole of 40 mm bore and about 1 m length. After the test as a stand-alone magnet inside an iron yoke, the magnet will be inserted in a large bore background dipole, for generating 10 to 18 tesla depending on the strength of the background field. In this paper, we report the design and test of the first technological model, called Feather-zero, wound with REBCO Roebel cable. Based on aligned block design to take advantage of the anisotropy of the REBCO tapes, Feather-zero is a precursor of the Feather-two that should reach the project goals in 2016. Feather-zero is planned to be tested both in stand-alone and as an insert mounted in the CERN Fresca facility providing 10 T background field. The progress of other designs pursued in the collaboration, one based on classical cosq lay-out with Roebel cable and the other based on coil block with stacked tape cable, will also be reported.
EuCARD-2 is co-funded by the partners and the European Commission under Capacities 7th Framework Programme, Grant Agreement 312453.
11:00 - 11:30 Influence of Magnetization on Field Qualities of Accelerator Magnets Made with Coated Conductors|
AMEMIYA Naoyuki1, SOGABE Yusuke1, SANO Takuya1, NAKAMURA Taketsune1, KAKEYA Itsuhiro1, KOYANAGI Kei2, ISHII Yusuke2, OGITSU Toru3
1Kyoto University, Japan, 2Toshiba Corporation, Japan, 3High Energy Accelerator Research Organization, Japan
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When using coated conductors in accelerator magnets, their large magnetization (screening current) caused by their wide shapes and affecting field quality is one of the serious concerns. We have to clarify its characteristics and, then, have to manage its influence on field quality. In this presentation, we focus on two topics: the influence of operating temperature on the drifts of the multipole components of magnetic field (the clarification of its characteristics); the influence of the orientations of coated conductors on the multipole components of magnetic field (the management of its influence). On the first topic, we measured the magnetic field in a dipole magnet consisting of racetrack coils at different temperatures as well as currents (magnetic fields), because E-J characteristic depends on temperature and current (magnetic field). We also measured the relaxation of the magnetization of a short coat conductor with a SQUID magnetometer to determine its E-J characteristics. Using the determined E-J characteristics, we carried out the numerical electromagnetic field analyses of the magnet to calculate the current distributions in the coated conductors. From the obtained current distributions in the entire magnet, we calculated the temporal evolutions of the dipole and sextupole components of the magnetic field and, then, compared them with the measured ones. On the second topic, there are different arguments on the good orientation of the wide faces of coated conductors: parallel to the field in a magnet; radial alignment in a cosine-theta magnet. If their wide faces are more parallel to the magnetic field, less magnetization (screening) current might be induced. If their wide faces are aligned radially in a cosine-theta magnet, perturbations in current distributions by magnetization currents are mostly radial: they might less affect the multipole components of the magnetic field, because the multipole components of the magnetic field are related closely to azimuthal current distributions. We carried out electromagnetic field analyses in magnets with various arrangements of coated conductors in their cross-sections. The discussion will be made on managements of the influence of magnetization through designs of coil configurations in magnets.
This work was supported by Japan Science and Technology Agency under Strategic Promotion of Innovative Research and Development Program (S-Innovation Program).
11:30 - 11:45 A High-field, High-homogeneity HTS Demonstration Magnet with Bi-2212 Round Wire|
TROCIEWITZ Ulf1, BOSQUE Ernesto1, HILTON David1, KIM Youngjae1, CHEN Peng1, DAVIS Daniel1, ENGLISH Charles1, MILLER Steven1, NOYES Patrick1, KAMETANI Fumitake1, JIANG Jianyi1, MATRAS Maxime1, HELLSTROM Eric1, LU Jun1, MCGUIRE David1, MILLER George1, HAHN Seungyong1, BIRD Mark1, BREY William1, LITVAK Ilya1, CROSS Timothy1, FRYDMAN Lucio1, LARBALESTIER David1
1NHMFL, Florida State University, United States
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The development of high field NMR quality magnets beyond 30 T (1 GHz) using high temperature superconductors (HTS) is a major goal at the NHMFL. To evaluate HTS conductor use in NMR magnets, we have built and characterized several test coils using conductors made from two of the most promising available materials, ReBa2Cu3O7-x (ReBCO) coated conductor tape and Bi2Sr2CaCu2O8-x (Bi-2212) round wire. In coils wound with tape, substantial screening currents can be induced, particularly in sections where the radial field components are high, thus affecting the spatial and temporal stability of the generated field. Bi-2212 can be made in the much more desirable isotropic, round wire, twisted multifilament architecture. Thus it appears to be particularly valuable for high field NMR magnets. We are in the process of building a layer-wound, round-wire Bi-2212 insert magnet, which is expected to generate about 6.5 T inside a 16.5 T low temperature superconducting (LTS) outsert magnet made by Oxford Instruments. A pair of layer-wound Bi-2212 compensation coils will be used to achieve field homogeneity (z2 component) targeting the ppm range. The implementation of Bi-2212 conductor in such magnets poses various materials and magnet manufacturing challenges. The conductor and coil R&D has generated many results essential to our ultimate technological goal of establishing Bi-2212 as a conductor of choice for the next generation of high-field, high-homogeneity HTS magnet systems. Here we present the current status and results of the ongoing project.
This work is supported by the National Science Foundation under DMR-1157490 and by a grant from the National Institute of Health under 1 R21 GM111302-01.
11:45 - 12:00 HTS dipole magnet for a particle accelerator using a twist stack cable|
HIMBELE John1, BADEL Arnaud1, TIXADOR Pascal1
1G2Elab, INPG, France
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High Tc superconducting (HTS) dipole magnet is expected to upgrade the high-energy particle accelerator. The future LHC dipole in the framework of EuCARD-2 project aims to generate a magnetic field between 17 and 20 T including a 5 T contribution of the HTS magnet. The HTS magnet is inserted into a 100 mm aperture under the high field of low Tc superconducting (LTS) outsert magnet. This has to provide a good field quality inside a 40 mm beam aperture. The HTS magnet faces the extremely large electromagnetic force. The stack cable with a ReBCO tape, which has a block-coil layout, is the simplest way to acquire the large current and the strong mechanical cable. A twist for half turn in the coil-ends transposes the positions of the tape inside the stack cable and improves the current distribution. However, the twist stack cable exposes the ReBCO tape into the bad field orientation towards the degradation of critical current density Je. The HTS dipole magnet is designed with a 4mm square block-coil. The 23 block-coils achieved the good field quality and the good mechanical performance with a 650 A/mm2 of operating current density Jop. The block-coils are aligned to the field in order to direct the force on the correct wide surface of ReBCO tape. In the coil-ends, the different strength and direction of force cause the shear stress between the tapes and complicate the mechanical architecture. We investigate the mechanical structure of coil-ends especially at twist part with a numerical model. The position of coil-ends between HTS insert and LTS outsert helps to reduce the mechanical force and keep the large Je.
12:00 - 12:15 A (RE)BCO Pancake Winding with Metallic Insulation|
LECREVISSE Thibault1, IWASA Yukikazu2
1Now CEA Saclay /IRFU/SACM/LEAS, France, 2MIT / Francis Bitter Magnet Laboratory, United States
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Due to superior mechanical performance and in-field current-carrying capacity under high fields, (RE)BCO tapes have played an important role to surpass the magnetic induction limit of LTS (Low Temperature Superconductor) wires. However, it also introduces a new challenge: the protection of (RE)BCO coil, much more complicated and costly than that of LTS counterpart, mainly because the slow normal zone propagation velocity of (RE)BCO. Also most (RE)BCO magnets with conventional insulated winding have been operated at a relatively low “overall magnet current density,” when compared with the short sample current density of (RE)BCO conductors, mainly due to the weak anisotropic in-field performance at a “local” spot of the (RE)BCO magnet.
Some new winding techniques, such as NI (Non-Insulated) and the NI-MW (NI-Multi-Width), are recently introduced for high-field (RE)BCO magnets, virtually with protection-free operation at an overall magnet current density close to the critical current density of a short sample. However, those techniques cannot be used for fast charge/discharge applications because of a long charging delay due to the bypassing currents through turn-to-turn contacts.
In this paper we are proposing an innovative winding technique: a metallic insulation (MI) technique for (RE)BCO coils, where metallic tapes are co-wound between coil turns in order to increase significantly the turn-to-turn contact resistances and reduce the charging delay, when compared to the NI counterpart. MI winding gives also a better control of the coil properties. Although the operation stability of MI coil is lower than that of NI, it is still better than its organic-insulated counterpart. Another advantage of the MI technique, when compared with its organic-insulated counterpart, is a much faster quench propagation velocity, even faster than that of typical LTS coils. The results presented here are: 1) a comparison of the overcurrent (OC) coil behaviors between NI and MI pancakes; 2) an in-depth study of electromagnetic characteristics of the MI pancake, including charging/discharging responses with various ramping rates, self-protection behaviors in case of fast pulse OC; 3) quench, stability and self-protection experimental studies with comprehensive instrumental setups at 77 K.
12:15 - 12:30 Measured and modelled AC magnetization loss of the REBCO Roebel baseline cable for the EUCARD2 accelerator insert magnet.|
BOTTURA Luca1, DHALLE Marc2, FALORIO Iole3, GAO Peng2, KIRBY Glyn1, VAN NUGTEREN Bas2, VAN NUGTEREN Jeroen1, JORGE Pelegrin3, WESSEL Sander2, YANG Yifeng3, EDUARD Young3
1CERN, Switzerland, 2University of Twente, Netherlands, 3University of Southampton, United Kingdom
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The EU FP7 collaboration EuCARD2 aims to demonstrate a HTS accelerator insert magnet that delivers a magnetic field of 5T in a background field of 13T. One of the concepts for such an insert is wound with an REBCO Roebel cable. In this paper we present the AC loss behavior of the impregnated 15-strand baseline cable to be used in this magnet, measured as function of temperature, magnetic field amplitude, frequency and field angle. The results are discussed in terms of hysteresis- and coupling loss contributions and compared to the loss predictions generated with a newly developed numerical 3D cable model.
This work is partly funded by the European Commission under GA 312453.