The time-decaying critical current density of a type-II superconductor and its measuring method

The paper will show that a critical current which has been thought to be defined only in the critical state of a type-II superconductor is able to measure by making use of its time-decaying behavior below onset currents of the resistive state due to flux creep. This is a kind of adiabatic process, in which the measurement of critical currents is done by waiting for a quench which takes place when the persistent current induced in a superconducting sample goes cross the time-decaying critical current and also is a method measuring life of the persistent current in the sample. According to this method, potential barrier models for flux pinning and characteristic parameters about superconductors will be determined.