Flux jumps in hot-isostatic-pressed bulk Mg B 2 superconductors: Experiment and theory

An experimental and theoretical study of flux jumps in magnetization curves of a highly dense polycrystalline $\mathrm{Mg}{\mathrm{B}}_{2}$ superconductor was performed. The local temperature increments in the vortex phase were modeled. For the theoretical analysis, a critical-state model was employed which considers Joule's heat dissipation due to temporal evolution of the magnetic induction. We used an adiabatic approximation to define an instability criterion on the shielding field with the Maxwell equations coupled to the thermal diffusion equation. Comparing experimental and theoretical magnetization loops, we found that the flux jump occurrence depends on the flux jump size.