Numerical Simulation of Inductive Method for Measuring $j_{\rm C}$ and Detecting Crack in an HTS Film

A numerical code has been developed for analyzing the shielding current density in a high-temperature superconducting (HTS) film with multiple cracks. By using the code, the inductive method for measuring the critical current density has been successfully reproduced, and the detectability of the multiple cracks in the HTS film has been investigated. The results of computations show that the estimated value of the threshold current always decreases when the coil approaches a crack. This tendency does not depend on the number of cracks. Moreover, if the crack distance is the outer diameter of the coil or less, it is difficult to detect the multiple cracks. From these results, the outer diameter of the coil must be adopted so as not to affect the cracks and the edges. Therefore, it is desirable to use a smaller the outer diameter as possible.