Temperature-and field dependent characterization of a twisted stacked-tape cable

Abstract

The Twisted Stacked-Tape Cable (TSTC) is one of the major high temperature\nsuperconductor cable concepts combining scalability, ease of fabrication and\nhigh current density making it a possible candidate as conductor for large\nscale magnets. To simulate the boundary conditions of such a magnets as well as\nthe temperature dependence of Twisted Stacked-Tape Cables a 1.16 m long sample\nconsisting of 40, 4 mm wide SuperPower REBCO tapes is characterized using the\n"FBI" (force - field - current) superconductor test facility of the Institute\nfor Technical Physics (ITEP) of the Karlsruhe Institute of Technology (KIT). In\na first step, the magnetic background field is cycled while measuring the\ncurrent carrying capabilities to determine the impact of Lorentz forces on the\nTSTC sample performance. In the first field cycle, the critical current of the\nTSTC sample is tested up to 12 T. A significant Lorentz force of up to 65.6\nkN/m at the maximal magnetic background field of 12 T result in a 11.8 %\nirreversible degradation of the current carrying capabilities. The degradation\nsaturates (critical cable current of 5.46 kA at 4.2 K and 12 T background\nfield) and does not increase in following field cycles. In a second step, the\nsample is characterized at different background fields (4-12 T) and surface\ntemperatures (4.2-37.8 K) utilizing the variable temperature insert of the\n"FBI" test facility. In a third step, the performance along the length of the\nsample is determined at 77 K, self-field. A 15 % degradation is obtained for\nthe central part of the sample which was within the high field region of the\nmagnet during the in-field measurements.\n