Temperature- and Field Dependent Characterization of a Twisted Stacked-Tape Cable

TL;DR

This study characterizes a 40-tape twisted stacked-tape superconductor cable under various temperature and magnetic field conditions, revealing how Lorentz forces and temperature affect its critical current and performance degradation.

Contribution

It provides detailed experimental data on the temperature and magnetic field dependence of a large-scale TSTC, including the effects of Lorentz forces and performance variation along the cable length.

Findings

Lorentz force causes 11.8% irreversible degradation at 12 T.

Critical current saturates after initial degradation.

Performance degradation varies along the cable length.

Abstract

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