Electromechanical characterization of REBCO twisted stack slotted-core cable under twisting and bending stress

The rapid development of high-temperature superconducting (HTS) technology has led to the emergence of HTS cables based on REBCO tapes as a key solution for future fusion magnets. The development of stacked HTS cables has become a focal point of research due to their exceptional current-carrying capacity and mechanical properties. However, the cables are subjected to complex twisting and bending stresses during the fabrication of the coils. It is therefore imperative to investigate the effects of these stresses on the electromechanical behavior of Twisted Stack Slotted-core Cable (TSSC) in order to optimize the design of fusion magnets. This paper presents a theoretical analysis of the impact of mechanical deformation of REBCO tape on the critical current (I_c) under varying twist pitch and bending radius conditions. The bending radii corresponding to the no-slip and perfect-slip models are approximately 1100 mm and 300 mm, respectively, when the criterion is taken to be 95 % I_c retention. Furthermore, an experimental comparison of the performance changes of the samples under bending stress, both before and after vacuum soldering, is conducted to evaluate the effect of the soldering process on the bending performance. The experimental results demonstrate that the pre-bending-before-soldering process can effectively control the bending radius, thereby reducing the impact of stress concentration on the superconducting performance and significantly improving the stability of the cable under complex mechanical loads. This process not only improves the reliability of HTS TSSC in fusion magnet applications, but also provides a key technical support for the manufacture and application of large-scale superconducting cables in the future.