Experimental Study on the Cabling Performance of REBCO Cable With Different Twist Pitches

The design and development of highly stable Cable-in-Conduit Conductor (CICC) technology are of paramount importance to enable REBCO fusion magnets to operate in magnetic fields exceeding 20T. As part of the ongoing efforts to advance REBCO CICC, the technique of twist-forming plays a pivotal role in the fabrication process. It is instrumental in achieving uniform current distribution, enhancing conductor stability, improving the mechanical strength of the cable, and reducing AC losses. Consequently, ASIPP has designed and developed two distinct cable structures specifically tailored for superconducting conductors in future fusion devices. Structure 1 (three-in-one) involves the twist-forming process of three highly flexible REBCO Cable (HFRC) cables to form a multi-strand cable with different twist pitches. It is mainly suitable for small current conductors. Structure 2, the "six-around-one," involves the precise twist-forming of six HFRC cables around a central hollow copper tube, resulting in the formation of a CICC cable. This structure is designed to cater to high-current conductor needs. Subsequently, their critical current performance with different twist pitches was experimentally evaluated under 77 K self-field conditions. The critical current test results indicate that for both structures, the critical current (Ic) remained around 335 A and 323 A as the twist-forming pitch decreased, with no significant performance degradation, respectively. This study preliminarily verifies the feasibility of the two twist-forming processes and demonstrates no significant influence on the cabling performance of REBCO cables with different twist pitches. These findings provide essential technical and parametric support for high-performance and full-size REBCO CICC production.