ELECTRO-THERMO-MECHANICAL COUPLING AND QUENCH PROTECTION IN REBCO RACETRACK AND LAYER-WOUND NO-INSULATION MAGNETS

Abstract

No-insulation (NI) winding technology, combined with controlled bypass architecture, has become the dominant strategy for protecting REBCO insert magnets operating above 20 T.[1] Experiments in 2025–2026 have shown that quench tolerance depends not only on stored energy but, more critically, on the electro-thermo-mechanical coupling response of the coil assembly.[4] Key parameters include the inter-turn contact resistivity ρc, screening-current-induced stress[12], and localized Joule heating caused by joint or solder defects.[2] This paper synthesizes recent advances in NI racetrack and layer-wound (LW-NI) magnets[6], drawing on the CEA IRFU RT9 single-pancake test (1025 A, 2.9 T)[5], the 15 T LW-NI insert developed for a 40 T hybrid magnet platform[23], and surface-shunt quench experiments under induced fault modes.[9] We propose a multiphysics modeling framework that couples the T–A formulation[30] with anisotropic heat conduction and strain-dependent critical-current degradation.[14] Simulations identify an optimal contact-resistivity window of 10⁻⁸–10⁻⁷ Ω·m[3], which minimizes hotspot temperature while maintaining acceptable charging characteristics. Vertical-field-priority charging is shown to suppress screening-current stress by more than 30%[26], and surface-shunt integration reduces peak temperature rise by up to 40% relative to unprotected NI coils.[8] Together, these results establish a robust design baseline for next-generation 30 T-class all-superconducting magnets.[16]