Numerical Simulation of Permanent Magnet Method: Applicability to Crack Detection in High-Temperature Superconducting Film

Applicability of the scanning permanent-magnet (SPM) method to crack detection in a high-temperature superconducting film is assessed by means of the numerical simulation. As a measure of crack detection, a defect parameter is defined by using the electromagnetic force acting on the film. After the defect parameter is calculated along various scanning lines, the sensitivity and the resolution are determined numerically. The results of computations show that both the sensitivity and the resolution are hardly affected by the scanning speed. On the other hand, the resolution of the SPM method is much inferior to that of the inductive method. In this sense, the SPM method is a high-speed but low-resolution method for detecting cracks.