Numerical Simulation of Conventional/Enhanced Permanent Magnet Method: Influence of Crack on Accuracy

The conventional and enhanced permanent magnet methods for measuring the critical current density in a high-temperature superconducting (HTS) tape have been simulated numerically. Moreover, the influence of the crack on the accuracy of the conventional method has been investigated. In order to simulate both permanent magnet methods, two types of numerical code have been developed for analysing the time evolution of a shielding current density in an HTS tape. The results of computations for the conventional method show that the maximum repulsive force acting on the tape drastically decreases when the symmetric axis of the magnet approaches the crack. On the other hand, the results of computations for the enhanced method show that the electromagnetic force near the center of the tape is roughly proportional to the critical current density. It is also found that the accuracy of the enhanced method compared with the conventional one hardly changes except for near the tape edge. Therefore, the enhanced method is a speedy and efficient method for measuring the spatial distribution of the critical current density.