Stability and Current Sharing in YBCO Cables – Impact of Broken Elements – FEM Modeling

Abstract

High field superconducting magnets require a high number of ampere-turns in their windings. To avoid large self-inductances in such magnets they must be wound using high current superconducting cables. Unlike other presently available HTS cables REBCO Roebel and CORC cables have their strands transposed or twisted to reduce both AC loss and magnetization. This improves field homogeneity and makes the magnets less ramp rate sensitive. Stability and current sharing is crucial in these cables. Here we present FEM modeling results on isothermal current sharing in tape-stack and CORC cables containing broken elements of different size and intensity located in different places of the cables. The FEM model assumed a magnetic field of 8 T at a temperature of 4.2 K. The stability of CORC cables can be simply controlled by modifying the size and thermal conductivity of their cores. Conclusions on stability and quench of these cables in magnet windings are made.