An effective model for fast computation of current distribution in operating HTS tapes from magnetic field measurements in non-destructive testing

摘要

Computation of the current distribution of superconducting devices is an important topic in the understanding of the behavior of superconducting materials, in the development of their applications and in testing the quality of the materials. The most successful technique to measure the currents is based on mapping the magnetic field in the surface of the superconducting sample during or after a magnetization process. Models for solving the inverse problem have been developed based on different techniques. The inversion technique based on considering the currents as the result of a distribution of magnetic moments has been tested for many years in the description of the currents in bulks, giving a useful tool for their characterization, including junctions and porous samples. The restriction of this technique to closed loops of currents does not allow its application to the exploration of superconducting wires. Specific considerations developed for this technique have, however, allowed extension of the technique to the study of HTS tapes in a simple and fast way that can be applied to the exploration of long tapes to determine the current distribution on the fly. In this work we report on the model and the procedure to perform the calculation of currents on tapes carrying current. The specific application to the detection of defects that do not affect the ability to carry current, such as longitudinally centered scratches, is experimentally tested. Details of the application of the method for long tapes are also reported.