Time-Domain FEM Analysis of Shielding Current Density in High-Temperature Superconducting Film with Crack: Application to Permanent Magnet Method

摘要

Applicability of the permanent magnet method to the measurement of the critical current density in a high temperature superconducting (HTS) film with a crack has been investigated numerically. To this end, a numerical code has been developed for analyzing the shielding current density in an HTS film. By using the code, the permanent magnet method has been reproduced numerically. The results of computations show that the accuracy of the method degrades monotonously as the crack size increases. This is mainly due to a decrease in the maximum repulsive force. It is also found that, the accuracy degrades drastically when the crack is located around the center axis of the magnet. This result means that, by using the permanent magnet method, it is possible to detect the crack. In conclusion, the resolution of the method is about 1.7 times radius and it can be improved by using the smaller value of radius.