Winding and Testing of YBCO Coils Using Different HTS Wires

YBCO coils with epoxy resin impregnation tend to experience degraded performance, which is due to the mismatch of the thermal contraction coefficients among former, epoxy, and HTS conductors which will generate thermal stresses that induce delamination of the superconducting layer. Several coils have been fabricated and tested, using the YBCO wires from SuperPower Inc. (SP), and Shanghai Superconductor Technology Corporation (SSTC). No degradation of the coil performance was detected for small SP coils, even with epoxy resin impregnation. However, for SP coils and SSCT coils using more than 100 m of YBCO wires, they all exhibited degraded performance after the epoxy resin impregnation. A possible solution to this problem is proposed and a 400 m SSCT coil has been successfully fabricated and tested.