Plasma and Fusion Research

Volume 17, 2405066 (2022)

Regular Articles

Simulation of Non-Uniform Current Distribution in Stacked HTS Tapes
Diego GARFIAS1), Maria MORBEY2), Yoshiro NARUSHIMA1,3) and Nagato YANAGI1,3)
1)
The Graduate University for Advanced Studies, SOKENDAI, 322-6 Oroshi-cho, Toki, Gifu 509-5292, Japan
2)
Dutch Institute for Fundamental Energy Research (DIFFER), De Zaale 20, 5612 AJ, Eindhoven, The Netherlands
3)
National Institute for Fusion Science, 322-6 Oroshi-cho, Toki 509-5292, Japan
(Received 8 January 2022 / Accepted 5 April 2022 / Published 8 July 2022)

Abstract

Low-Temperature Superconductors (LTS) are sensitive to non-uniform current distribution, which produces quenching. So, transposition of strands is indispensable in LTS cables to help current redistribution. In contrast, High-Temperature Superconductors (HTS) have higher thermal stability, which is expected to help current redistribution among strands (tapes) without quenching. Generally, HTS cable designs consider transposition to reduce quench likelihood and better handling AC operation. However, transposition causes mechanical strain in the tapes, reducing their performance. Recently, a 20-kA-class Stacked Tapes Assembled in Rigid Structure (STARS) conductor is being developed at NIFS, for the next-generation helical devices. To weigh the simple stacking feasibility of HTS tapes, a previous experiment confirmed, that 5 non-transposed HTS tapes can stably conduct a worst-case non-uniform current distribution without quenching. This further suggests that when using HTS tapes for DC HTS cables, transposition may be optional, but not strictly required. A numerical simulation was developed, dealing with the current distribution among the HTS tapes in a worst-case scenario, reproducing the previous experimental observation, and a second experiment was performed to give insights into the contact resistance between HTS tapes. The self-magnetic field effect and temperature fluctuations are to be explored for quench scenarios.

Keywords

HTS, ReBCO, current distribution, STARS, fusion magnet

DOI: 10.1585/pfr.17.2405066

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