Impact of Bending on the Critical Current of HTS CrossConductors

Abstract

Fusion applications require high magnetic fields for plasma confinement, which results in magnet coils with high operational currents. To achieve these high currents, high temperature superconductor (HTS) strands like the HTS CrossConductor (HTS CroCo) are an option. However, to reach the required high currents, multiple HTS CroCo strands have to be assembled as cable. These cabling processes as well as the winding of the magnet coil induce mechanical strain in the HTS CroCo. In this work the results of modelling critical currents of HTS CroCos at different bending radii are discussed and validated by experiments. The simulation uses the finite element method and is capable to calculate the critical current of the ideal HTS CroCo at different bending radii as well as predicting the possible range of the critical current degradation due to production tolerances of the HTS CroCos. For the experimental tests the examined samples were bent to radius at room temperature, afterwards the critical current measurement took place at T = 77 K and self-field conditions. Each sample was characterized at different bending radii in decreasing order. After the sequence of measurements, cross-sectional images of the samples were prepared to analyze macroscopic damage of the HTS CroCo.