Numerical and experimental research of the screening current mitigation under shaking field in no-insulation coils

The screening current problem is one of the most critical challenges in high-temperature superconducting (HTS) coated conductors (CCs), severely degrading both the magnetic field amplitude and stability of HTS inserts in high-field superconducting magnets. A promising strategy to mitigate screening current is the application of a shaking field perpendicular to the Penetrating field. However, existing studies lack an effective computational model for vortex shaking process and a comprehensive investigation into the unique characteristics of no-insulation (NI) coils under shaking field. In this paper, a T-A formulation that considering coil thickness is used to simulate the electromagnetic behavior of NI coils during the shaking process. By combining simulations and experiments, the reduction of screening current induced field (SCIF) under varying coil parameters and operation condition is investigated. The results indicate that the radial current has a dominant influence on SCIF in NI coils with low contact resistivity. The rapid change in radial current induced by the shaking field leads to a sharp mitigation in the screening current within a short period, exhibiting a strong dependence on the shaking duration and coil contact resistivity. Moreover, this study demonstrates the effectiveness of shaking field in accelerating radial current decline and evaluates the additional AC losses. These findings offer insights into the different mechanism of shaking field on SCIF reduction and radial current decline in NI coils, contributing to a better understanding of strategies for mitigating large screening current in REBCO magnets.