Effect of coil current sweep cycle and temperature change cycle on the screening current-induced magnetic field for Ybco-coated conductor coils

Yanagisawa, Yoshinori; Kominato, Yasuaki; Nakagome, Hideki; Fukuda, T.; Takematsu, T.; Takao, T.; Takahashi, Masato; Maeda, Hideaki

doi:10.1063/1.4707063

Cited by 37 publications

(30 citation statements)

References 10 publications

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“…2(a), and the remnant screening magnetic field is as large as 140 mT. Several notches can be seen on curve-2 and curve-3 showing the magnetic field drift with time during the current holds, which are caused by the relaxation of the screening current [29].…”

Section: Hysteresis Effect Of the Central Magnetic Field Intensitymentioning

confidence: 94%

Operation of a 400 MHz NMR magnet using a (RE:Rare Earth)Ba2Cu3O7− high-temperature superconducting coil: Towards an ultra-compact super-high field NMR spectrometer operated beyond 1 GHz

Yanagisawa

Piao

Iguchi

et al. 2014

Journal of Magnetic Resonance

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High-temperature superconductors (HTS) are the key technology to achieve super-high magnetic field nuclear magnetic resonance (NMR) spectrometers with an operating frequency far beyond 1GHz (23.5T). (RE)BaCuO (REBCO, RE: rare earth) conductors have an advantage over BiSrCaCuO (Bi-2223) and BiSrCaCuO (Bi-2212) conductors in that they have very high tensile strengths and tolerate strong electromagnetic hoop stress, thereby having the potential to act as an ultra-compact super-high field NMR magnet. As a first step, we developed the world's first NMR magnet comprising an inner REBCO coil and outer low-temperature superconducting (LTS) coils. The magnet was successfully charged without degradation and mainly operated at 400MHz (9.39T). Technical problems for the NMR magnet due to screening current in the REBCO coil were clarified and solved as follows: (i) A remarkable temporal drift of the central magnetic field was suppressed by a current sweep reversal method utilizing ∼10% of the peak current. (ii) A Z2 field error harmonic of the main coil cannot be compensated by an outer correction coil and therefore an additional ferromagnetic shim was used. (iii) Large tesseral harmonics emerged that could not be corrected by cryoshim coils. Due to those harmonics, the resolution and sensitivity of NMR spectra are ten-fold lower than those for a conventional LTS NMR magnet. As a result, a HSQC spectrum could be achieved for a protein sample, while a NOESY spectrum could not be obtained. An ultra-compact 1.2GHz NMR magnet could be realized if we effectively take advantage of REBCO conductors, although this will require further research to suppress the effect of the screening current.

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Section: Hysteresis Effect Of the Central Magnetic Field Intensitymentioning

confidence: 94%

Operation of a 400 MHz NMR magnet using a (RE:Rare Earth)Ba2Cu3O7− high-temperature superconducting coil: Towards an ultra-compact super-high field NMR spectrometer operated beyond 1 GHz

Yanagisawa

Piao

Iguchi

et al. 2014

Journal of Magnetic Resonance

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“…To avoid an unexpected quench, we aim at 50% reduction of screening curren induced field (SCF) at the magnetic center of the coil and then consequently determine I tar c (r) of the coil with activation of the Thermal Eraser. Provided that the critical current is proportional to temperature at a given magnetic field 43,49 , T tar (r) can be analytically calculated with:…”

Section: Designmentioning

confidence: 99%

“…To date, multiple techniques have been reported for mitigation of screening current [43][44][45][46][47] . Among them, there is an idea to temporarily increase the operating temperature of an HTS magnet "on purpose" in order to lower the overall critical current of the magnet.…”

Section: Introductionmentioning

confidence: 99%

“Thermal Eraser” to Mitigate Screening Current by Optimal Control on Spatial Temperature Distribution in a High Temperature Superconductor Magnet

Bang¹,

Kim²,

Lee³

et al. 2021

Preprint

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The so-called “screening current” in high temperature superconductor (HTS) is a well-known phenomenon that has detrimental effects on performance of an HTS magnet. To date, many research efforts have been devoted to suppressing screening current in an HTS magnet. Here we report a customized electric-heater, named “Thermal Eraser”, to mitigate the screening current. The key idea is to optimally control spatial temperature distribution in an HTS magnet using the customized heater and the consequent temperature-dependent local critical current of HTS wires of the magnet. To validate the idea, a Thermal Eraser was designed, constructed, and installed in an actual single-pancake HTS coil. And the Thermal Eraser plus test coil system was operated at temperatures ranging 7-40 K in our in-house conduction-cooling cryogenic facility. The feasibility of the Thermal Eraser was demonstrated in terms of two aspects: 1) creation of the designated spatial temperature distribution within the HTS test coil as designed; and 2) quantitative evaluation of its effectiveness to mitigate screening current using both experimental and numerical results. We confirmed that the screening current induced field in the test coil was reduced by 0.6 mT after activation of the Thermal Eraser, which implies 60% reduction of screening current in the HTS test coil. The results demonstrate that the Thermal Eraser is a viable option to effectively reduce the screening current in an HTS magnet.

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“…In this method, which is widely used to stabilize the magnetic field drift in conventional low-T c superconducting magnets [15], the current is ramped up above the operating level and then reduced back to the desired operating level. This method was also applied to coils made out of high temperature superconductors [13], [16], [17], but these coils did not operate in persistent mode.…”

Section: Introductionmentioning

confidence: 98%

Investigation of the Relaxation of Persistent Current in Superconducting Closed Loops Made Out of YBCO Coated Conductors

Rong

Barnes

Levin

et al. 2015

IEEE Trans. Appl. Supercond.

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Coated conductors allow the fabrication of closed superconducting loops of arbitrary size. Various mechanisms can play a role in the decay of a persistent current in one such loop and in an assembly of multiple loops magnetically coupled with each other. We report recent experimental results on the relaxation rate of the persistent current in an assembly of closed superconducting loops made out of the currently manufactured coated conductors. One of the main goals of this study is to find the effective ways to control the relaxation rate so as to make it small enough to enable such high temperature persistent magnets to be considered as potential alternatives for energy storage, MRI magnets, and magnetic levitation applications. Here we report the effect of appropriately modified current sweep reversal method on the relaxation rate.Index Terms-Coated conductor, current sweep reversal method, MAGLEV, MRI, persistent current, relaxation rate, SMES, 2G HTS.

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Effect of coil current sweep cycle and temperature change cycle on the screening current-induced magnetic field for Ybco-coated conductor coils

Cited by 37 publications

References 10 publications

Operation of a 400 MHz NMR magnet using a (RE:Rare Earth)Ba2Cu3O7− high-temperature superconducting coil: Towards an ultra-compact super-high field NMR spectrometer operated beyond 1 GHz

Operation of a 400 MHz NMR magnet using a (RE:Rare Earth)Ba2Cu3O7− high-temperature superconducting coil: Towards an ultra-compact super-high field NMR spectrometer operated beyond 1 GHz

“Thermal Eraser” to Mitigate Screening Current by Optimal Control on Spatial Temperature Distribution in a High Temperature Superconductor Magnet

Investigation of the Relaxation of Persistent Current in Superconducting Closed Loops Made Out of YBCO Coated Conductors

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