Construction and Test Results of Coil 2 of a Three-Coil 800-MHz REBCO Insert for the 1.3-GHz High-Resolution NMR Magnet

Bascuñán, J.; Michael, Philip; Hahn, Seungyong; Lécrevisse, Thibault; Iwasa, Y.

doi:10.1109/tasc.2016.2641341

Cited by 19 publications

(6 citation statements)

References 5 publications

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“…In previous calculations, Zhang et al have also derived the non-uniform ρ t2t distribution that innermost and outermost turns have the largest ρ t2t values for an NI coil wound with a uniform pre-stress of 25 MPa [63]. Similar calculations in [64][65][66][67] have demonstrated that the innermost and outermost turns of the HTS coil theoretically have the minimum radial stress, which in the NI coil would result in the larger ρ t2t value on these turns [63]. In this work, the non-uniform ρ t2t distribution might come from; (i) the innermost and outermost turns of the HTS coil naturally have the minimum radial stress [63][64][65][66][67]; (ii) 50 Hz AC field induced Lorentz force vibrations on HTS tapes, making the winding flexible thus more liquid nitrogen penetration in the turn-to-turn intervals, especially for the inner/outermost several turns.…”

Section: Simulation Analysismentioning

confidence: 87%

Time-variant magnetic field, voltage, and loss of no-insulation (NI) HTS magnet induced by dynamic resistance generation from external AC fields

Zhong

et al. 2023

Supercond. Sci. Technol.

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High-temperature superconducting (HTS) coils serving as DC magnets can be operated under non-negligible AC fields, like in synchronous machines of maglev trains and wind turbines. In these conditions, dynamic resistance generates in HTS tapes, causing redistribution/bypassing of the transport current inside the no-insulation (NI) coil and its unique operational features. This issue was studied by experiments on an NI coil with DC current supply put into external AC fields. Due to the current redistribution induced by dynamic resistance, the central magnetic field and voltage of the NI magnet initially undergo various transient processes, and eventually exhibit a stable central magnetic field reduction and a DC voltage. These time evolutions have implications for a time-varying torque and loss of an HTS machine. These time evolutions are strongly affected by the contact resistivity distribution, and whether it is the first time of the NI magnet being exposed to the AC field, showing several qualitatively different waveforms (e.g., some are even non-monotonic with time). The magnitudes of the stable central field reductions, and their observed linear correlation with the DC voltages are found to be decided by the local contact resistivity of the innermost and outermost several turns. It is also noted that the non-insulated turn-to-turn contact help lessening the loss induced by the dynamic resistance. A numerical model is established to analyse/explain those experimental results by observing the microscopic current distribution. Two risks of quench are noticed: (i) azimuthal current of the middle part turns increases as the AC field is applied; (ii) a concentration of radial current is observed near the terminals of the NI coil.

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Section: Simulation Analysismentioning

confidence: 87%

Time-variant magnetic field, voltage, and loss of no-insulation (NI) HTS magnet induced by dynamic resistance generation from external AC fields

Zhong

et al. 2023

Supercond. Sci. Technol.

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“…Coils 2 and 3 were wound with a winding tension of 50 N. Wound with the no-insulation technique as was Coil 1, they are also compact, self-protecting, and with high mechanical robustness. Another feature, first applied to Coil 1 is the inclusion of a 1-mm thick inner stainless steel ring to prevent collapsing of the DP innermost turns, induced by the external pressure build up due to the winding tension [4].…”

Section: Coil 2: Fabrication Processesmentioning

confidence: 99%

Construction and Test Results of Coils 2 and 3 of a 3-Nested-Coil 800-MHz REBCO Insert for the MIT 1.3-GHz LTS/HTS NMR Magnet

Park

Bascuñán

Michael

et al. 2018

IEEE Trans. Appl. Supercond.

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We present construction and test results of Coils 2 and 3 of a 3-coil 800-MHz REBCO insert (H800) for the MIT 1.3 GHz LTS/HTS NMR magnet currently under construction. Each of three H800 coils (Coils 1-3) is a stack of no-insulation REBCO double pancakes (DPs). The innermost 8.67-T Coil 1 (26 DPs) was completed in 2016; the middle 5.64-T Coil 2 (32 DPs) has been wound, assembled, and tested; and for the outermost 4.44-T Coil 3, its 38 DPs have been wound and preliminary tests were performed to characterize each DP at 77 K. Included for Coil 2 are: 1) 77-K data of critical current, index, and turn-to-turn characteristic resistivity of each DP; 2) stacking order of the 32 DPs optimized to maximize the Coil 2 current margin and minimize its Joule dissipation in the pancake-to-pancake joints; 3) procedure to experimentally determine and apply a room-temperature preload to the DP stack; 4) 77-K and 4.2-K test results after each of 64 pancakes was over-banded with 75-μm-thick stainless steel tape for a radial thickness of 5 mm. Presented for each DP in Coil 3 are 77-K dada of critical current, index, and turn-to-turn characteristic resistivity.

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“…Fig. 1 shows the general arrangement of our PCS coil, which was assembled using a spare NI DP remaining after fabrication of Coil 2 of our 800-MHz REBCO insert for a 1.3-GHz spectrometer magnet [17]. Nominal conductor and coil characteristics are summarized in [17].…”

Section: Pcs Coil Configurationmentioning

confidence: 99%

A REBCO Persistent-Current Switch, Immersed in Solid Nitrogen, Operating at Temperatures Near 10 K

Michael¹,

Lee²,

Voccio

et al. 2018

IEEE Trans. Appl. Supercond.

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We present design and test results for a thermally-activated persistent-current switch (PCS) applied to a double pancake (DP) coil (151 mm ID, 172 mm OD), wound, using the no-insulation (NI) technique, from a 120-m long, 76-μm thick, 6-mm wide REBCO tape. For the experiments reported in this paper, the NI DP assembly was immersed in a volume of solid nitrogen (SN2), cooled to a base temperature of 10 K by conduction to a two-stage cryocooler, and energized at up to 630 A. The DP assembly operated in quasi-persistent mode, with the conductor tails soldered together to form a close-out joint with resistance below 6 nΩ. The measurements confirm PCS activation at heating powers below our 1-W design target, and a field decay time constant in excess of 900 h (i.e 0.1% h field decay rate), limited by the finite resistance of the close-out joint.

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Construction and Test Results of Coil 2 of a Three-Coil 800-MHz REBCO Insert for the 1.3-GHz High-Resolution NMR Magnet

Cited by 19 publications

References 5 publications

Time-variant magnetic field, voltage, and loss of no-insulation (NI) HTS magnet induced by dynamic resistance generation from external AC fields

Time-variant magnetic field, voltage, and loss of no-insulation (NI) HTS magnet induced by dynamic resistance generation from external AC fields

Construction and Test Results of Coils 2 and 3 of a 3-Nested-Coil 800-MHz REBCO Insert for the MIT 1.3-GHz LTS/HTS NMR Magnet

A REBCO Persistent-Current Switch, Immersed in Solid Nitrogen, Operating at Temperatures Near 10 K

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