Increase in Coupling-Current Losses of Superconducting Cables Due to First-Stage Cabling

II. Loss-Minimized Structure of Stabilized Sub-Cable

Abstract

We have investigated AC losses in a seven-strand superconducting sub-cable, in which a few normal-metal strands with high conductivity are located for stabilization. In a transverse magnetic field with a trapezoidal wave form, approximate expressions for coupling losses among superconducting strands through normal-metal strands were obtained in addition to intra-strand AC losses by using equivalent electrical-circuit models. The total losses measured in several types of the stabilized sub-cables were well explained by the theoretical results. An optimized arrangement of the normal-metal strands in the sub-cable was also discussed in relation to minimizing the AC loss.