Numerical Investigation of Inductive and Permanent-Magnet Methods to Measure Critical Current Density of HTS Thin Films

Abstract

The inductive method/permanent-magnet method for measuring the critical current density <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">j</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</sub> in a high-temperature superconducting (HTS) tape have been simulated numerically. To this end, a numerical code has been developed for analyzing the time evolution of a shielding current density in an HTS sample. The results of computations show that, in the inductive method, the edge effects lead to the degradation of the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">j</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</sub> -measurement accuracy. In contrast, it is found that, even if the magnet is placed near the edge, the maximum repulsive force is roughly proportional to <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">j</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</sub> . This means that the permanent-magnet method is applicable to measure <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">j</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</sub> near the edge.