Anisotropy analysis and AC loss performance of stepped-groove twisted stacked-tape cables for high-field applications

In order to meet the requirements of high current-carrying capability and reduced electromagnetic anisotropy in future high-field superconducting magnet systems, an improved twisted stacked-tape cable (TSTC) with stepped grooves and multidirectional tape arrangements is proposed in this paper. Inspired by quasi-isotropic strand (QIS) and conventional TSTC structures, the proposed conductor places three groups of equal-volume REBCO tape stacks with different orientations in each stepped groove. This design combines the enhanced tape-accommodation and current-carrying potential of the stepped-groove architecture with a multidirectional arrangement intended to mitigate the anisotropic response of REBCO tapes under external magnetic fields. A two-dimensional H-formulation finite-element model was developed to investigate the critical current and AC loss characteristics of the proposed conductor. Four tape-stacking arrangements of the improved TSTC were first compared to evaluate the influence of tape orientation on electromagnetic anisotropy. The selected improved TSTC was then benchmarked against conventional TSTC, stepped TSTC, and QIS cable configurations. The results show that, although the QIS cable exhibits higher or comparable critical current under some conditions, the improved TSTC achieves better angular isotropy than the conventional TSTC while maintaining a relatively high current-carrying capability. The multidirectional tape arrangement effectively reduces the dependence of critical current and AC loss on magnetic-field orientation.