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  • 1
    Language: English
    In: IEEE transactions on applied superconductivity, 2016-04, Vol.26 (3), p.1-5
    Description: The NOUGAT project is the first step toward a 30-T all-superconducting high-field magnet. It combines a 20-T resistive outsert, which is one of the test facilities in the National Laboratory for Intense Magnetic Fields (LNCMI), and a 10-T high-temperature superconductor (HTS) insert. After a brief presentation of the HTS insert, we detail the protection principle that is based on the extraction of the energy simultaneously in a discharge resistance and in copper rings located within the insert. The main role of these rings is to act as a transformer secondary and to dissipate a large fraction of the energy during the discharge. We show that this energy dissipation is not significant enough to consider the rings as passive heaters due to the large temperature margins within the HTS insert. Analytical calculations have also been led on a simple two-loop circuit, and criteria regarding the flux linkage and mutual coupling have been defined to check the efficiency of the protection principle.
    Subject(s): High-temperature superconductors ; High Field Magnet ; HTS protection ; Heating ; Superconducting magnets ; High Temperature Superconductors ; Discharges (electric) ; Copper ; Current density ; Magnetic circuits
    ISSN: 1051-8223
    E-ISSN: 1558-2515
    Source: IEEE Electronic Library (IEL)
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  • 2
    Language: English
    In: IEEE transactions on applied superconductivity, 2019-08, Vol.29 (5), p.1-5
    Description: This paper presents the construction and the test results of a metal-as-insulation (MI) HTS mock-up insert for a 10 T HTS insert. Two MI double pancake (DP) coils were fabricated using 6 mm wide GdBaCuO commercial coated conductor tapes. Each of them has an inner joint between the top and bottom pancakes. They were made using nearly the same parameters as the DP coils designed for the 10 T HTS insert. Each DP coil was tested in LN2 bath at 77 K to measure its inner joint resistance and critical current (Ic) values. After the assembling process of the DP coils, charging tests of the MI mock-up magnet were performed to evaluate current carrying capacity, stability, and mechanical strain issues of the HTS insert under various background magnetic fields in a LHe bath at 4.2 K. These results show that the MI mock-up magnet was stably charged nearly up to its calculated Ic under background fields in the range of 0-20 T without any thermal and mechanical damage even though it experienced a quench due to unstable cryogenic conditions. In addition, the HTS insert generated a field of 7 T at 417 A (engineering current density of 660 A/mm 2 ) in a background magnetic field of 20 T, which yields a combined field of 27 T.
    Subject(s): Coils ; Integrated circuits ; High-temperature superconductors ; metallic insulation ; Magnetic field measurement ; HTS quench protection ; Windings ; HTS insert ; Superconducting magnets ; High temperature superconductors ; REBCO tapes ; Magnetic fields ; Physics ; Physics archives
    ISSN: 1051-8223
    E-ISSN: 1558-2515
    Source: IEEE Electronic Library (IEL)
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  • 3
    Language: English
    In: IEEE transactions on applied superconductivity, 2016-06, Vol.26 (4), p.1-5
    Description: In the new 43-T LNCMI hybrid magnet, a good conducting shield is inserted between the resistive insert magnet and the superconducting outsert magnet. Its goal is to decrease the ac losses induced in the superconducting conductor during a fault of the insert, disruption of the resistive coils (i.e., fast discharge) by smoothing the flux variations, and avoidance of a quench of the superconducting coil. The induced currents within the shield are very large due to the presence of copper material, which is the drawback of a good screening effect. Such currents result in large Lorentz forces, particularly during the most severe fault scenario of the resistive insert with the burnout of half of the Bitter coils. Finally, the detection system must be specially designed to handle the effects of the shield on the induced voltages.
    Subject(s): Coils ; High Field Magnet ; Hybrid Magnet ; Magnetomechanical effects ; Shield ; Superconducting magnets ; Magnetic noise ; Discharges (electric) ; Helium ; Magnetic shielding
    ISSN: 1051-8223
    E-ISSN: 1558-2515
    Source: IEEE Electronic Library (IEL)
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  • 4
    Language: English
    In: IEEE transactions on applied superconductivity, 2020-09, Vol.30 (6), p.1-9
    Description: Screening currents are a major drawback in the context of rare-earth-barium- copper-oxide (ReBCO) magnets because their parasitic effects on the generated field are exacerbated by the particular shape of the conductors. Previously, we have developed numerical tools for the computation of screening currents and their effects in the cases of systems featuring two-dimensional (2-D) symmetries, axial or longitudinal. Nevertheless, 2-D models are not always adequate for every three-dimensional (3-D) shape or alternative winding configuration such as layer-wound ones. Therefore, a quasi 3-D model has been implemented in the in-house CAST3M finite-element code, using the current function T formulation. We developed CAST3M operators to take into account the superconducting behavior of the material and the anisotropic dependence of the current density on the magnetic induction. Simple scenarios, especially one solved with analytical formulations, have been defined to benchmark codes; CASTEM was successfully benchmarked against them. Finally, we compared the generation of screening currents within a small solenoid depending on the type of winding, made either of layers or pancakes. We also compared these results with a simple 2-D model made of nested turns.
    Subject(s): screening currents ; Electric potential ; Magnetic resonance imaging ; Superconducting magnets ; pancake winding ; Mathematical model ; layer winding ; Perpendicular magnetic anisotropy ; Current density ; High-temperature superconductor (HTS) coil
    ISSN: 1051-8223
    E-ISSN: 1558-2515
    Source: IEEE Electronic Library (IEL)
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  • 5
    Language: English
    In: IEEE transactions on applied superconductivity, 2015-06, Vol.25 (3), p.1-5
    Description: Longitudinal and transverse quench propagation tests were performed at the Laboratoire National des Champs Magnetiques Intenses (LNCMI) high-field test facility on instrumented double pancake coils fabricated by CEA-Saclay using co-wound high-temperature superconductor (HTS) tapes. Energy deposited on an embedded heater initiated a quench and its subsequent propagations. Following the resulting thermomechanical analysis, a conductor design with stacked HTS tapes co-wound with stabilizers was conceived. A ten-turn demonstrator racetrack coil has been fabricated from the stacked HTS conductor with an aim to investigate the operation margin of an HTS coil in a background magnetic field misaligned from the coil axis as expected for the operating condition of an accelerator magnet insert. A test setup with a high current capacity up to 3 kA and angular variability that utilizes a room-temperature 376-mm-bore 10-T resistive magnet at LNCMI in Grenoble has been built. The performances and operation margin of the racetrack coil were investigated.
    Subject(s): Coils ; High-temperature superconductors ; High-temperature superconductors (HTS) ; Art ; HTS coils ; Current measurement ; Heating ; Windings ; HTS quench propagation ; Conductors ; High-field magnet ; High temperature superconductors ; Usage ; Research ; Electric coils ; Nuclear Experiment ; Physics
    ISSN: 1051-8223
    E-ISSN: 1558-2515
    Source: IEEE Electronic Library (IEL)
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  • 6
    Language: English
    In: IEEE transactions on applied superconductivity, 2017-06, Vol.27 (4), p.1-4
    Description: Screening currents are a major concern when designing high-temperature superconducting magnets as they can have a drastic impact on the generated field level, homogeneity, and temporal stability. Thus, the this paper will present results from an experimental and numerical study of the screening current-induced effects in a small-sized ReBCO coil. On the experimental side, two small single pancakes have been wound from 4-mm-wide Kapton-insulated ReBCO tape provided by manufacturer SuperOx and high-sensitivity Hall probes were mounted on the coils to monitor their generated field. The coils have then been tested at liquid nitrogen temperature, both at the remanent state and with transport current to measure the time decay of the screening current-induced field. The experimental systems have also been modeled for magnetodynamic simulations using the free and open-source software GetDP and Gmsh. A two-dimensional axisymmetrical FEM model of the coils has been built, accounting for the detailed layer structure of the windings. An H-φ formulation was used, using an E(J) power law for the superconductor behavior and cohomology to enforce current constraints. First results obtained with this model are presented, showing its capability to simulate screening currents in coils of several tens of turns. Yet, its accuracy and computation time will need to be further improved. The presented results are a first milestone in our investigation for efficient and inexpensive methods to simulate screening currents in ReBCO HTS coils.
    Subject(s): Temperature measurement ; Finite-element methods (FEMs) ; screening currents ; Current measurement ; Atmospheric modeling ; Magnetic domains ; numerical models ; Superconducting magnets ; high-temperature superconductors ; Time measurement ; superconducting coils ; Probes ; Physics
    ISSN: 1051-8223
    E-ISSN: 1558-2515
    Source: IEEE Electronic Library (IEL)
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  • 7
    Language: English
    In: IEEE transactions on applied superconductivity, 2010-06, Vol.20 (3), p.2074-2077
    Description: The R3B-Glad superconducting Magnet provides the field required for a large acceptance spectrometer, dedicated to the analysis of Reactions with Relativistic Radioactive ions Beams. In the framework of the FAIR Project to GSI and within NUSTAR physics program, the technical study started in 2006, and the engineering fabrication is undertaken. The magnetic field and active shielding are achieved by means of 6 superconducting trapezoidal racetrack coils made of a Rutherford type NbTi superconducting cable. The coils are indirectly cooled at an operating temperature of 4.5 K by a thermo-siphon circuit, and are designed to run at a nominal current of 3.6 kA. The corresponding maximum stored magnetic energy reaches 24 MJ. The quench protection is achieved by discharging the magnet in an external resistor, with a voltage to ground of ±500 V at the beginning of the discharge. The design and the characteristics of the quench protection system are described. The computational results of the quench protection for several scenarii are presented as well as the thermal and electromagnetic behavior of the coil cases.
    Subject(s): R3B ; Spectroscopy ; quench ; superconducting magnet ; Superconducting magnets ; Magnetic analysis ; Superconducting coils ; Physics ; Ion beams ; Magnetic shielding ; Superconducting cables ; Fabrication ; Protection ; Electrical engineering. Electrical power engineering ; Telecommunications and information theory ; Exact sciences and technology ; Applied sciences ; Information, signal and communications theory ; Electromagnetic compatibility ; Electromagnets ; Connection and protection apparatus ; Various equipment and components ; Electric connection. Cables. Wiring ; Titanium alloys ; Ionization ; Analysis ; Magnetic energy storage ; Design and construction ; Maintenance and repair ; Niobium ; Magnetic properties ; Electric properties
    ISSN: 1051-8223
    E-ISSN: 1558-2515
    Source: IEEE Electronic Library (IEL)
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  • 8
    Language: English
    In: IEEE transactions on applied superconductivity, 2018-06, Vol.28 (4), p.1-5
    Description: Magnetization currents are known to be the cause of field disturbances in high-temperature superconducting REBCO magnets. The tape-like shape of REBCO-coated conductors implies that a magnetic field orthogonal to their flat surface can induce large screening current loops, which in turn generate a screening current-induced field (SCIF). This SCIF results in detrimental effects on the overall field generated by the magnet, lowering its amplitude and disturbing both the field quality and time stability. This paper focuses on the experimental investigation of two techniques for suppressing the detrimental SCIF effects. First, vortex shaking uses an auxiliary ac magnetic field of small amplitude to accelerate the relaxation of the current density in the superconductor, thus, erasing the SCIF in a short period of time. The second technique, the current overshoot, consists in charging the magnet to its nominal operating point with an initial overshoot, which creates a favorable initial current density distribution mitigating the time drift observed on the field. Those techniques were tested on small REBCO single pancake coils at 77 K with different kinds of insulation: full Kapton insulation and metallic cowinding.
    Subject(s): Coils ; High-temperature superconductors ; Insulation ; 2G HTS Conductors ; Magnetization ; Windings ; Superconducting magnets ; Magnetic field effects ; Current density ; HTS Coils ; Physics
    ISSN: 1051-8223
    E-ISSN: 1558-2515
    Source: IEEE Electronic Library (IEL)
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  • 9
    Language: English
    In: IEEE transactions on applied superconductivity, 2018-06, Vol.28 (4), p.1-5
    Description: The EuCARD high temperature superconductor (HTS) insert is a dipole magnet generating a self-field of 5.4 T and designed to operate at 18 T within the FRESCA2 test facility; it has just been successfully tested in stand-alone configuration up to 4.5 T (see M. Durante et al.). To operate in such a large field, its winding is made of a 12 mm HTS REBCO insulated conductor; each conductor is composed of four tapes in parallel to achieve a large current of 2.8 kA. The drawbacks of using parallel HTS tapes are numerous: first, they are very sensitive to orthogonal field inducing screening currents loops within the tapes. Second, the use of tapes in parallel imposes to transpose the conductor to avoid current loops between tapes, induced from the parallel field. The screening currents in return generate a magnetic field (screening current induced field), opposed to the main one and consequently lowering it and degrading the homogeneity. We have developed a finite difference code in order to simulate the induced currents within a conductor made of parallel tapes; we have calculated the screening current induced field and showed that the order of magnitude is non negligible compared to the main field. These computations have been benchmarked against measurement of the magnetic field performed during the stand-alone configuration tests.
    Subject(s): screening currents ; High-temperature superconductors ; Magnetic flux ; HTS ; Superconducting magnets ; Dipole magnet ; REBCO ; Conductors ; SCIF ; Mathematical model ; Current density ; stacked tapes
    ISSN: 1051-8223
    E-ISSN: 1558-2515
    Source: IEEE Electronic Library (IEL)
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  • 10
    Language: English
    In: IEEE transactions on applied superconductivity, 2020-06, Vol.30 (4), p.1-6
    Description: In this study, two metal-as-insulation (MI) REBCO double-pancake (DP) coils comprised of THEVA and SuperPower REBCO single pancake (SP) coils were constructed and assembled. A sapphire plate was inserted in between the two-single pancake (SP) assembled as a DP, while copper plates insulated by G10 were inserted between the DPs to enhance the cooling of the MI insert. The thermal and electrical characteristics were investigated under an applied external field in the range of 0 to 19 T at 4.2 K. The insert was pushed up to the quench at each field, such defining its real operating limit without damage. Its thermal stability was checked up to 10 A/s in self-field (SF) at 4.2 K. Characteristic resistance change, current-carrying performance, quench behavior, thermal stability of the MI insert is discussed.
    Subject(s): Coils ; Integrated circuits ; High-temperature superconductors ; high temperature superconductors ; quench behavior ; High magnetic field insert ; Windings ; REBCO coated conductors ; Superconducting magnets ; metal-as-insulation winding technique ; Thermal stability ; Physics ; Physics archives
    ISSN: 1051-8223
    E-ISSN: 1558-2515
    Source: IEEE Electronic Library (IEL)
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