Dynamic evolution of pressure-dependent non-uniform turn-to-turn contact resistivity in no-insulation REBCO magnets: modeling and experimental validation

The no-insulation (NI) magnets wound with REBCO coated conductors have thermal stability and quenching elasticity. This performance is driven by the current bypass on the interturn contacts. However, the resulting characteristic charging delay is controlled by complex electromechanical interactions in high magnetic fields, which are still difficult to predict. In this study, the contact resistivity of two ‘sandwich’ setups, namely ‘No-Insulation Contact’ and ‘Metal-Insulation (MI) Contact’, was investigated at 77 K and 4.2 K under pressure, specifically for copper-plated and copper-laminated tapes. A multi-exponential divergence model of contact resistivity with pressure is proposed to improve the fitting accuracy of the trend of contact resistivity with pressure. At the same time, the complete finite element method in the weak form of the T–A formulation is used to construct the simulation model of a large NI REBCO magnet based on a 2D axisymmetric coordinate system. The model directly calculates the inductance coupling through the magnetic vector potential, different from the field-circuit coupling model. This reduces the step of pre-calculating the huge mutual inductance matrix. Meanwhile, it incorporates electromechanical coupling by allowing the turn-to-turn contact resistivity (TTCR) to change dynamically in response to the instantaneous radial Lorentz force. It is verified on the ten-thousand-turn large-scale NI REBCO inserting magnet in the 35.1 T all-superconducting magnet system made by ASIPP. These results show that the charging behavior of the NI REBCO magnet in the high field is controlled by electromechanical coupling. Specifically, the Lorentz force alters the contact pressure distribution, leading to a spatially varying TTCR that determines the field stabilization time. This work provides key theoretical and model support for future electromagnetic–mechanical behavior prediction and quench robustness analysis of NI REBCO magnets.