Bending characteristics of multi-layer spiral HTS cable with large tape gap

Assembling high-temperature superconducting (HTS) tapes into robust cable with spiral geometry is widely adopted to achieve high current-carrying capacity and strong mechanical properties in high-field magnet applications. However, multi-layer structure of spiral HTS cable undermines its bending performance due to complex factors, which have not been comprehensively clarified yet. In this paper, the influence of the tape gap on the bending characteristics of double-layer spiral HTS cable has been investigated through both experimental and numerical methods. and we revealed a distinct mechanism of critical current degradation during bending correlated with large tape gap. Result shows that, the large tape gap, as an unneglectable geometrical irregularity, leads to the increment of the interlayer friction coefficient. Moreover, with the increase of tape gap, additional compressive strain would be imposed on tape, leading to the exacerbation of imbalance of strain distribution. Therefore, cable samples with larger tape gap exhibit inferior bending performance compared to those with smaller tape gap, and this earlier occurrence of critical current degradation during bending process is primarily manifested in the outer layer. Conclusion obtained from this paper is anticipated to assist the understanding of the mechanism of bending performance degradation, as well as the improvement of engineering production for multi-layer spiral HTS cable.