Experimental Evaluation of Loss Generation in HTS Coils Under Various Conditions

Hemmi, T.; Yanagi, N.; Seo, K.; Maekawa, R.; Takahata, K.; Mito, T.

doi:10.1109/tasc.2005.849263

Cited by 14 publications

(5 citation statements)

References 8 publications

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“…For the charging process, B 0 was slightly smaller than a calculated magnetic field B cal (the dashed-dotted line) as indicated by arrow-a. This was caused by a screening current [29][30][31] induced in the Bi-2223 conductor. For I Bi =30 A in the charging process, B 0 was 31.8 mT which is 96.4% of B cal .…”

Section: Behavior Of the Central Magnetic Fieldmentioning

confidence: 99%

Combination of high hoop stress tolerance and a small screening current-induced field for an advanced Bi-2223 conductor coil at 4.2 K in an external field

Yanagisawa

Iguchi

et al. 2015

Supercond. Sci. Technol.

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An advanced Bi-2223 conductor with Ni–Cr reinforcement is a likely candidate to achieve a compact super-high field nuclear magnetic resonance (NMR) magnet capable of operation beyond 1 GHz (23.5 T). However, the conductors must show both high hoop stress tolerance, typically >300 MPa, and a small screening current-induced magnetic field, both of which are essential for a compact magnet generating a highly accurate field. These two conditions have not yet been demonstrated in a working coil. This is the first paper to systematically investigate both characteristics for a layer-wound coil made with the advanced Bi-2223 conductor operated mainly at 4.2 K in an external field of ≤17 T. The coil tolerated a hoop stress of 370 MPa, even though the conductor had a bending strain corresponding to a diameter of 120 mm. On the other hand, the coil showed a notable screening current-induced field in a low external field, which may be explained by weak-link and direct contacts between highly packed Bi-2223 filaments in the silver matrix. The field sharply decreased with increasing external field between 0–1 T. Thus, the conductor should be useful for inner coils in compact super-high field NMR magnets.

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Section: Behavior Of the Central Magnetic Fieldmentioning

confidence: 99%

Combination of high hoop stress tolerance and a small screening current-induced field for an advanced Bi-2223 conductor coil at 4.2 K in an external field

Yanagisawa

Iguchi

et al. 2015

Supercond. Sci. Technol.

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“…1). The logarithmic decay of the shielding currents is supposed to play the key role to affect the transport current in place of the coupling currents in the LTS wires [5], [6]. However, the current decay behavior of HTS coils has been evaluated only by the joint resistance and E-J characteristics of the HTS tapes, so far, on the other hand, the effect of shielding currents on the current decay behavior of the HTS coils has been discussed in [7].…”

Section: Improvements Of Current Decay Behavior Of Hts Coils In Persimentioning

confidence: 99%

Improvements of Current Decay Behavior of HTS Coils in Persistent Current Operations

Hemmi

Yanagi

Seo

et al. 2007

IEEE Trans. Appl. Supercond.

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In order to improve the current decay behavior of high-temperature superconducting (HTS) coils using silversheathed Bi-2223 tapes in persistent current operations, the effect of the shielding current on the current decay behavior has been studied for magnetically levitated superconducting coils in internal ring devices. Generally, the current decay behavior of HTS coils is evaluated by the inductance of the HTS coils, the joint resistance and electric field versus current density relationship of the HTS tapes. In this paper, the effect of shielding currents in HTS tapes is discussed. It is shown that improvements of their properties of HTS tapes, which are the n-value and the critical current, are not so effective to decrease the shielding current in HTS tapes. Numerical electromagnetic analysis using finite element method and experiments have been carried out. Furthermore, improvements of the current decay behavior using excitation techniques are discussed.Index Terms-Current decay behavior, high-temperature superconducting coil, internal ring device, persistent current operation.

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“…The details of the present experiment are discussed in [11] and one of its highlights is briefly introduced in the following. In the present experiment, the magnetic field above the sample coil was measured using a Hall probe and the change of magnetization of the sample coil was monitored.…”

Section: Investigation Of the Mechanism Of Additional Loss Generatmentioning

confidence: 99%

“…This observation indicates that the decaying process of the shielding current is mitigated due to the increase of the critical current density in the HTS tape. Further analysis for the experimental results is given in [11].…”

Section: Investigation Of the Mechanism Of Additional Loss Generatmentioning

confidence: 99%

Effective Resistance of the HTS Floating Coil of the Mini-RT Project

Yanagi

Mito

Hemmi

et al. 2005

IEEE Trans. Appl. Supercond.

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Abstract-A magnetically levitated superconducting coil device, Mini-RT, has been constructed using high temperature superconductors for the purpose of examining a new magnetic confinement scheme of high-beta plasmas. The floating coil is wound with Bi-2223/Ag tapes, and it is operated in the temperature range of 20-40 K. The excitation tests of the coil were carried out and persistent current was sustained for magnetic levitation. The decay time constant of the persistent current was measured and the effective resistance of the coil cables was evaluated. The obtained resistance shows a considerable increase than that predicted by the n-value model. This might be caused by some electromagnetic effects such as the loss generation with long-lived shielding currents. This consideration was examined by measuring the magnetization of an HTS sample coil.

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Experimental Evaluation of Loss Generation in HTS Coils Under Various Conditions

Cited by 14 publications

References 8 publications

Combination of high hoop stress tolerance and a small screening current-induced field for an advanced Bi-2223 conductor coil at 4.2 K in an external field

Combination of high hoop stress tolerance and a small screening current-induced field for an advanced Bi-2223 conductor coil at 4.2 K in an external field

Improvements of Current Decay Behavior of HTS Coils in Persistent Current Operations

Effective Resistance of the HTS Floating Coil of the Mini-RT Project

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