Rapid flux motion and critical state dynamics in a superconducting disk

Abstract

A disk of superconducting thin film partially screens an externally applied magnetic field. If the film temperature is increased, the depression of the critical current density allows the excluded flux to move in. When the film is driven to its resistive state by rapid heating, the fast decay of the screening currents results in rapid flux motion. We have developed a numerical technique for analyzing this transient flux motion along with the temporal variation of current density and magnetic field. Our theoretical model has been verified experimentally by heating a high-temperature superconducting film with short laser pulses and by measuring the induced voltage across a coil coupled closely to the film. This concept can be used to make a fast contactless opening switch for high-power applications, such as energy extraction from inductive energy storage systems.