Plasma and Fusion Research

Volume 9, 1405014 (2014)

Regular Articles

Design, Fabrication, and Persistent Current Operation of the REBCO Floating Coil for the Plasma Experimental Device Mini-RT

Yuichi OGAWA, Junji MORIKAWA, Kenichiro UCHIJIMA, Yuichiro HOSAKA, Chika KAWAI, Kenzo IBANO, Toshiyuki MITO¹⁾, Nagato YANAGI¹⁾, Kyohhei NATSUME¹⁾, Yoshiro TERAZAKI²⁾, Masataka IWAKUMA³⁾, Akira TOMIOKA⁴⁾ and Shinichi NOSE⁴⁾

: Graduate School of Frontier Sciences, University of Tokyo, Kashiwa 277-8568, Japan
1): National Institute for Fusion Science, Toki, Gifu 509-5292, Japan
2): Graduate University for Advanced Studies, Toki, Gifu 509-5292, Japan
3): Graduate School of Information Science and Electrical Engineering, Kyushu University, Fukuoka 819-0395, Japan
4): Fuji Electric Co., Ltd., Ichihara, Chiba 290-8511, Japan

(Received 21 October 2013 / Accepted 18 December 2013 / Published 14 March 2014)

Abstract

High-temperature superconductor technology has become remarkably advanced, and components such as current leads and magnets have been explored for their applicability to fusion. Especially, REBa₂Cu₃O_7-δ (RE = rare-earth: REBCO) tape has been developed in research fields other than fusion, because of superior performance of REBCO in high magnetic fields. Here, we fabricated a REBCO coil with a radius of 150 mm and a total coil current of 55.2 kA, to be applied as an internal floating coil in Mini-RT, a plasma experimental device. This newly fabricated REBCO coil has replaced the Bi₂Sr₂Ca₂Cu₃O₁₀ (BSCCO) coil developed in 2003, and has improved coil performance and plasma operation. A REBCO tape of width 4.3 mm was employed, and a 0.1 mm-thick copper laminate was attached for the countermeasure at the quench. In addition, the REBCO tape was wrapped in a polyimide sheet for electric insulation, increasing the total thickness of the REBCO tape to 0.27 - 0.28 mm. A persistent current switch was constructed from a small-turn REBCO winding with a heater formed from a stainless steel sheet. Solder joint of two REBCO tapes over a 30 mm length were employed, by overlapping their copper laminates. Persistent current, with a decay time ∼320 h, has been successfully achieved at 25 K operation temperature. This decay time corresponds to a resistance of ∼125 nΩ, roughly consistent with the total resistance of the seven joint sections in the persistent current circuit.

Keywords

High Temperature Superconductor (HTS), REBCO tape, persistent current, Persistent Current Switch (PCS), internal floating coil

DOI: 10.1585/pfr.9.1405014

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This paper may be cited as follows:

Yuichi OGAWA, Junji MORIKAWA, Kenichiro UCHIJIMA, Yuichiro HOSAKA, Chika KAWAI, Kenzo IBANO, Toshiyuki MITO, Nagato YANAGI, Kyohhei NATSUME, Yoshiro TERAZAKI, Masataka IWAKUMA, Akira TOMIOKA and Shinichi NOSE, Plasma Fusion Res. 9, 1405014 (2014).