The Influence of Magnetic History on the Stability of Critical State and the Dynamics of Flux Jumps in Conventional NbTi Superconductor

We studied the influence of magnetic history on the stability of critical state and the dynamics of flux jumps in conventional NbTi superconductor. We have found that both the stability of critical state and the dynamics of flux jumps are strongly influenced by the magnetic history and by the magnetic field distribution induced within the sample by preceding jumps. This magnetic field distribution can be particularly complex in the region of the hysteresis loop where the external magnetic field changes its sign (region of remagnetization), because of demagnetizing effects. For this reason, the most complex structure of the flux jumps is observed in the third quadrant of magnetization hysteresis loop. Flux jumps observed in the region of remagnetization have different dynamics in comparison to the jumps observed in other regions of the magnetization hysteresis loop. Duration of these jumps is usually significantly longer than others, and their structure is more complex.