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  • 1
    Language: English
    In: IEEE transactions on applied superconductivity, 2019-08, Vol.29 (5), p.1-5
    Description: We recently developed an electrothermal model to study the occurrence and evolution of dissipative zones in a Rare-Earth BaCuO (REBCO) high-temperature superconductor (HTS) coils, considering the local critical current (Ic) inhomogeneity with a centimeter-scale resolution. In this study, we present an application of this model, implemented in Comsol Multiphysics, to the REBCO insert of the 25-T CSM magnet developed in the High Field Laboratory for Superconducting Material of Tohoku University. The destructive thermal runaway event or "quench" observed on that coil will be introduced, followed by the modeling approach that was used to model it. We could simulate the coil behavior with a single 2-cm-long defect and verify that a more sensitive detection system in the millivolt range could be used to safely protect such magnets even from such a local defect. In the case of a more usual inhomogeneity distribution of Ic, the temperature rise is more homogenous and safe protection can be reached even at higher detection levels.
    Subject(s): Coils ; quench propagation ; very high field and nmr magnets ; Critical current density (superconductivity) ; Magnetic domains ; Superconducting magnets ; Conductors ; Integrated circuit modeling ; HTS magnets
    ISSN: 1051-8223
    E-ISSN: 1558-2515
    Source: IEEE Electronic Library (IEL)
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  • 2
    Language: English
    In: Superconductor science & technology, 2019-03-07, Vol.32 (4), p.44008
    Description: High-temperature superconducting materials have remarkable current-carrying capabilities, even when operated under high magnetic fields. Since long rare earth-barium-copper oxide (REBCO)-coated conductors are now available (thanks to improvements in the fabrication process) this material has become an attractive option for high field magnet applications. However, such extreme operating conditions require an efficient quench protection system to prevent the coil from developing damaging hot spots, which greatly depends on the winding used. We focus here on the protection of insulated HTS coils against thermal runaways that can locally destroy the magnet. We developed a transient two-dimensional (2D) axisymmetric model using a volume integral formulation based on generalization of the partial element equivalent circuit method to compute the local current density distribution inside REBCO-insulated coils and account for local performance variations. Indeed, the most interesting property of integral methods is the requirement that only active regions are meshed, which leads to a significant reduction in the size of the problem. The formulation is introduced for general 3D cases and its adaptation to 2D axisymmetric problems is detailed. The formulation has been validated thanks to a bulk magnetization benchmark, the results of which (obtained with the finite element method) were compared with our integral formulation solution. The model has also been compared with experimental data obtained on a double pancake coil. The objective is to study the effects of magnetization on the transient voltage due to dynamic current distribution when ramping up the magnet so as to be able to determine some key parameters associated with coil protection. Such an approach is developed on a small-scale test case and the transient behaviours observed are discussed.
    Subject(s): volume integral method ; quench protection ; insulated HTS coils ; current distribution
    ISSN: 0953-2048
    E-ISSN: 1361-6668
    Source: IOPscience extra
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  • 3
    Language: English
    In: IEEE transactions on applied superconductivity, 2016-04, Vol.26 (3), p.1-5
    Description: High-T c superconducting (HTS) dipole magnets are expected to be used in the upgrade of existing particle accelerators. In the framework of EuCARD-2 project, a new dipole-generating field between 17 and 20 T is under consideration with an HTS insert providing 5 T. This has to provide a good field quality at two-thirds of 40-mm beam aperture. The HTS stacked cable is the simplest way to acquire the large current and a strong mechanical cable. A twist for a half-turn in the magnet ends partially transposes the stacked tapes and improves the current distribution. However, the twisted stacked cable exposes the ReBCO tape to magnetic fields perpendicular to their wide face, where the engineering current density J e is lower. In addition, the different strength and direction of forces cause shear stress between the tapes. The HTS twisted stacked insert is designed with a 4 × 4-mm block-coil stacked with 4-mm-wide tape. The 46-turns of stacked cable, which is almost aligned to the background field, achieve a 5 T with the required field quality. The 3-D magnet ends are designed with the racetrack and flared-ends coils. It consists of six double pancakes. One of the mechanical conditions in the coil-ends, whose block-coil is divided into four tapes, has been analyzed with the Fresca2 LTS outsert. The HTS insert is able to withstand forces on its own.
    Subject(s): Superconducting cables ; Coils ; Particle accelerator ; High-temperature superconductors ; Power cables ; Magnetomechanical effects ; Superconducting magnets ; Current distribution ; dipole magnet ; EuCARD-2
    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, 2019-08, Vol.29 (5), p.1-5
    Description: Magnetic field stability and hysteresis can be serious problems in a high-field high-temperature superconducting magnet, because of the large shielding current effect. Accordingly, the field stability of a 25 T cryogen-free superconducting magnet (25T-CSM) was investigated. This particular system can generate a central field of 24.6 T in a 52-mm room-temperature bore. It was found that the magnetic field relaxation rate of the 25T-CSM with a Bi 2 Sr 2 Ca 2 Cu 3 O y (Bi2223) insert was due to the flux creep effect, and was small enough to allow nuclear magnetic resonance (NMR) experiments. Based on these experiences in the development of the 25T-CSM, primitive designs for a 30 T cryogen-free superconducting magnet (30T-CSM) were suggested based on upgrading the present Bi2223 insert to a REBa 2 Cu 3 O y (RE123, RE: rare earth and Yttrium) insert incorporating two co-wound RE123 tapes. It was confirmed that the prototype test coil could be operated at 4.2 K under large electromagnetic stresses of up to 540 MPa without experiencing degradation.
    Subject(s): High-temperature superconductors ; Electromagnetic stress ; quench ; superconducting coil ; high temperature superconductor ; Superconducting magnets ; Magnetic noise ; magnetic field stability ; Magnetic hysteresis ; Magnetic fields ; Stress ; Magnetic shielding
    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, 2016-04, Vol.26 (3), p.1-5
    Description: New improvements in high-temperature superconductors (HTS) are encouraging for large-scale applications, particularly for high-field magnets. In this context, the "NOUGAT" project aims at designing and building a 10-T HTS insert operating inside a 20-T resistive magnet. The insert is foreseen as a stack of double pancakes wound with REBCO tapes. The combination of current and magnetic field generate large mechanical stresses. Moreover, as the conductor has strong anisotropic properties, its performances are affected by transverse magnetic fields. Therefore, they have to be studied under high magnetic field at a small disorientation, close to the longitudinal axis of the coil. The objective is to evaluate its limiting critical current. This paper reports critical current measurements on a 4-mm REBCO tape provided by SuperOx. They were performed on the tape full width under a high magnetic field of up to 23 T at 4.2 K at the Laboratoire National des Champs Magnétiques Intenses (LNCMI) at various field angles. The limiting critical current is found to be about 350 A, which represents a current margin of 57% on a basic model. Then, a preliminary test of a prototype double-pancake coil is reportedly tested at up to 16 T.
    Subject(s): Magnetic field measurement ; Critical current density (superconductivity) ; Angular dependence ; Current measurement ; high field magnet ; HTS ; Superconducting magnets ; REBCO tapes ; Magnetic fields ; Perpendicular magnetic anisotropy ; critical current ; 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, 2016-04, Vol.26 (3), p.1-7
    Description: Due to their high-current-carrying capacity, round geometry, and low cost, MgB2 wires are promising candidates for realizing high-power cables. However, their operating temperature between 4.2 K and 25 K makes ac losses a critical issue for those cables. To optimize the cable architecture for minimizing ac losses, one must be able to predict them quite accurately. As a first step in this direction, we addressed the numerical computation of a single multifilamentary MgB2 wire that forms the basic element of a high-current cable. The wire under consideration has 36 twisted MgB2 filaments disposed on three concentric layers and embedded in a pure-nickel matrix. An initial comparison between 2-D and 3-D finite elements was performed to justify the need for a full 3-D model, without which coupling losses in the matrix cannot be modeled properly. This is of prime importance since coupling loss is the dominant loss mechanism at high applied fields. Then, simulations of simpler geometries (6- and 18-filament wires) submitted to various transport currents and/or applied fields were performed to identify trends in ac losses and find the best numerical tools for scaling up simulations to the full 36-filament case. The complexity of the model was progressively increased, starting with MgB2 filaments in the air matrix and then adding electrical conductivity and magnetic properties in the nickel matrix.
    Subject(s): Geometry ; Superconducting cables ; Solid modeling ; Power cables ; Wires ; Nickel ; Numerical models ; AC losses ; power cable ; FEM modelling ; MgB2
    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, 2017-06, Vol.27 (4), p.1-5
    Description: A superconducting magnetic energy storage (SMES) is an attractive power supply for electromagnetic rail launchers (EMRL), which require pulse currents to launch projectiles at very high speeds. Moreover, the accelerating force in an EMRL may be enhanced by adding a background field, a principle known as launcher S3EL concept (Superconducting Self-Supplied Electromagnetic Launcher) consists in using the SMES both as a power supply and for background field generation. The challenge is to reach the operating current and peak magnetic field of such launchers, which can be up to hundreds of kA and up to 10 T. The use of a high-temperature superconductor is mandatory to maintain superconducting operation during a launch, though operation at 4.2 K is foreseen to benefit from the RareEarth-BaCuO (REBCO) tape high critical current densities. The aim of this work is to derive a practical design for a 1-m-long small-scale S3EL proof of concept using REBCO coated conductor, with a reduced output velocity (100 m/s). After preliminary sizing studies, the spatial constraints for the SMES-Launcher integration is presented. A parametric joint analytical and Finite Element Method (FEM) study is conducted to refine the design and maximize the operation margins while maintaining the launch performances. Finally, cable design and discharge method suitable to reach the required operating current are presented.
    Subject(s): Rails ; Couplings ; High-temperature superconductors ; Projectiles ; Friction ; HTS ; REBCO ; electromagnetic rail launcher (EMRL) ; Superconducting magnetic energy storage ; pulse power ; SMES ; Physics
    ISSN: 1051-8223
    E-ISSN: 1558-2515
    Source: IEEE Electronic Library (IEL)
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  • 8
    Article
    Article
    2012
    ISSN: 1051-8223 
    Language: English
    In: IEEE transactions on applied superconductivity, 2012-06, Vol.22 (3), p.5700204-5700204
    Description: A SMES (Superconducting Magnetic Energy Storage) is basically a pulse current source. It is an attractive power supply for electromagnetic launchers, which require pulse currents to launch items or projectiles at very high speeds. SMES brings an alternative to the capacitors used at present which requires a pulse forming inductance limiting the energy transfer efficiency. The resulting oversizing of the primary source is more the issue than the efficiency itself, as power capacitors do not show high mass/volume densities of energy. The very high current required by the launcher may be reached using the XRAM concept, which is a current multiplier for SMES. We will compare the performances of SMES and capacitors to supply a small and a large launcher for different scenarios such as a total or a partial discharge of the SMES.
    Subject(s): Coils ; Rails ; Inductance ; High-temperature superconductors ; Projectiles ; Capacitors ; pulse power systems ; Switches ; Superconducting magnetic energy storage ; Electrical engineering. Electrical power engineering ; Electrical power engineering ; Exact sciences and technology ; Electronics ; Applied sciences ; Dielectric, amorphous and glass solid devices ; Energy accumulation ; Electronic equipment and fabrication. Passive components, printed wiring boards, connectics ; Power electronics, power supplies ; Direct energy conversion and energy accumulation ; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices ; Technology application ; Usage ; Electric circuits ; Differential equations ; Innovations ; High temperature superconductors ; Methods ; Simulation methods ; Energy storage ; Engineering Sciences ; Electric power
    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, 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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  • 10
    Language: English
    In: IEEE transactions on applied superconductivity, 2021-08, Vol.31 (5), p.1-5
    Description: The use of Rare-Earth BaCuO (REBCO) coated conductors is well adapted for Resistive type SFCL (Superconducting Fault Current Limiter) thanks to their high current carrying capability and high resistance per unit length. However, in case of fault currents in the range of the critical current 〈inline-formula〉〈tex-math notation="LaTeX"〉{{\boldsymbol{I}}_{\boldsymbol{c}}}〈/tex-math〉〈/inline-formula〉, the dissipation can be highly inhomogeneous along the length, leading to localized temperature elevations in the normal zones. This so-called hot-spot regime is well predicted by simulation tools but was seldom studied experimentally in a non-destructive way. This paper presents two experimental results highlighting the existence of the hot-spot regime. First, localized dissipation on a REBCO tape is observed through high speed recording of nitrogen bubbles synchronized with electric measurements. Second, the maximum temperature at the end of the limitation is studied as a function of the prospective current through measurements carried out on the conductor developed by the European Project FASTGRID. The maximum temperature is found experimentally to be highest for prospective current close to the conductor 〈inline-formula〉〈tex-math notation="LaTeX"〉{{\boldsymbol{I}}_{\boldsymbol{c}}}〈/tex-math〉〈/inline-formula〉.
    Subject(s): Temperature measurement ; Resistance ; Current measurement ; Superconducting Fault Current Limiter ; Superconducting transmission lines ; Hot-spot ; Conductors ; Nonhomogeneous media ; 2G HTS coated conductor ; Electric fields
    ISSN: 1051-8223
    E-ISSN: 1558-2515
    Source: IEEE Electronic Library (IEL)
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