Numerical Simulation of Permanent Magnet Method: Relation Between Critical Current Density and Maximum Repulsive Force

The permanent magnet method for measuring the critical current density of the high-temperature superconducting (HTS) thin film is investigated numerically. The numerical code has been developed for analyzing the time evolution of the shielding current density in the HTS thin film. In the code, the initial-boundary-value problem of the shielding current density is solved numerically. After discretized by using the finite element method (FEM) and the backward Euler method, it is reduced to the problem in which the simultaneous nonlinear equations are solved at each time step. By using the numerical code, the maximum repulsive force is calculated as a function of the critical current density. The results of computations show an excellent proportional relationship between them. This is mainly because the spatial distribution of the shielding current density varies in proportion to the critical current density except for the neighborhood of the film edge.