Numerical Investigations on Inductive Method for Film/Bulk Superconductors

The inductive method for measuring the critical current density in a high-temperature superconductor (HTS) has been investigated numerically. In the method, an ac magnetic field is generated by a small coil placed just above a HTS sample and, simultaneously, the third-harmonic voltage V ₃ induced in the coil is measured. In order to simulate the inductive method, a numerical code has been developed for analyzing the time evolution of the shielding current density. By using the code, the I ₀-V ₃ curves are determined and, subsequently, the critical current density is estimated. The results of computations show that, even if the power law is assumed as the J-E constitutive relation, the critical current density can be accurately estimated by the inductive method. In addition, it is found that, for both a film HTS and a bulk HTS, the assumed B-dependence of the critical current density can be successfully reproduced by the estimating formulas of the inductive method.