Flux

Abstract

We consider the flux jump instability of the Bean’s critical state arising in the flux creep regime in type-II superconductors. We find the flux jump field, B j , that determines the superconducting state stability criterion. We calculate the dependence of B j on the external magnetic field ramp rate, ˙ B e . We demonstrate that under the conditions typical for most of the magnetization experiments the slope of the current-voltage curve in the flux creep regime determines the stability of the Bean’s critical state, i.e. , the value of B j . We show that a flux jump can be preceded by the magneto-thermal oscillations and find the frequency of these oscillations as a function of ˙ B e .