Vortex penetration and flux relaxation with arbitrary initial conditions in non-ideal and ideal superconductors

Abstract

Vortex penetration and flux relaxation phenomenon carry the information about the pinning ability, and consequently current-carrying ability, of a type-II superconductor. However, the theoretical descriptions to these phenomena are currently limited to the cases with special initial conditions. A generalization to the recently developed infinite series models is presented here. It is shown that one can convert a vortex penetration process with a non-zero initial internal field into a process with a zero initial internal field by introducing some time parameters. Similarly, one can also convert a flux relaxation process starting with an arbitrary internal field into a process starting with a melting internal field by introducing a virtual time interval. Therefore, one can predict the melting internal field (or critical current density) from a flux relaxation process starting with a lower internal field. Finally, it is shown that the vortex penetration process in an ideal superconductor is strongly time dependent because of the surface barrier and internal field repulsive force. But the flux relaxation process does not occur in the ideal superconductor.