Mutual triggering mechanism of flux jump and quench in type-II superconducting rectangular strips

Abstract In design of superconducting systems, type-II superconductors are tasked with carrying a transport current while typically operating in the presence of an external magnetic field. When exposed to unexpected perturbations, these systems will be susceptible to instabilities, mainly manifesting as flux jump and quench. These two phenomena can occur simultaneously or sequentially, with one potentially triggering the other. In this paper, we build a comprehensive electromagnetic-thermal-mechanical coupling model, derived from Maxwell’s equations, the heat diffusion equation and elasticity theory, to systematically investigate the flux jump and quench dynamics in rectangular MgB 2 strips subjected to a time-varying transport current and a perpendicular magnetic field. This model can capture a rich spectrum of nonlinear behaviors driven by the modified power-law relationship across wide ranges of temperature and current density. After rigorous validation against experimental data, we explore the effects of field sweep rate, current sweep rate, and ambient temperature on flux jump, quench, strain and stress. The results show that the flux jump and quench phenomena are confined to specific ranges of field and current sweep rates. Increasing ambient temperature suppresses flux jump but expedites quench initiation. As both the transport current and magnetic field increase, the instability dynamics become spatially asymmetric. The instability is suppressed on one side of the strip, while localized quenching, initiated by localized flux jump, emerges on the other side. This localized quenching prompts current redistribution, driving it away from the resistive region, triggering further flux diffusion, and ultimately leading to a global quench. These findings provide critical insights into the mutual triggering mechanism of flux jump and quench under varying magnetic field and transport current conditions.