Development of a Roebel structure transposed cable with in-plane bending of REBCO tapes

Abstract

A compact High Temperature Superconductor (HTS) cable that can carry large current is crucial for developing high field superconducting accelerator magnets. Herein, we are reporting a high current and low AC loss REBCO cable that adopts the Roebel structure, but it is implemented by in-plane bending stacked REBCO tapes directly to realize the transposition, instead of by punching REBCO tapes to the desired shape. The cable maximizes the utilization of the original REBCO tapes, so that the material cost is significantly reduced comparing with the present “Roebel” REBCO cable. Recently, a prototype cable has been successfully fabricated. The critical current of each REBCO tape after cabling shows no degradation, and the cable’s measured critical current is 1939.8 A at 77 K and self-field, which is very close to the predicted critical current by simulation. Calculations also show that the AC loss of the cable is lower compared with that of a simple REBCO stack with the same cross-section and current-carrying capacity. In this paper, we first introduce the fabrication process of the cable. What follows is the measurement of the in-plane bending performance of REBCO tapes. Then, we present the design and fabrication of the prototype cable together with current-carrying performance tests. Finally, the AC loss calculation and analysis of the cable are reported.