Numerical Simulation of Contactless Method for Measuring $j_\mathrm{C}$ in Multiple-Layered Superconducting Film With Cracks

Applicability of the scanning permanent magnet method to the measurement of the critical current density in a high-temperature superconducting (HTS) film containing a crack with the consideration of a depth has been investigated numerically. To this end, a numerical code has been developed for analyzing the shielding current density in a multiple-layered HTS film with a crack. By using the code, the scanning permanent magnet method has been reproduced numerically. The results of the computations show that the disturbed area around a crack can be quantified by the introduction of a defect parameter. Moreover, it is found that the area increases with a strength of the magnetic flux density. On the other hand, the distinction between internal and surface cracks is not always obvious since the defect parameter for an internal crack is approximately equal to its parameter for a surface crack. However, the scanning permanent magnet method proved to detect the even internal crack.