Measurement of AC current distributions in HTS tapes

It is important to evaluate the characteristics of the current distributions in the HTS tapes and conductors in order to realize HTS power devices. In this study, we have developed a simple measurement method to evaluate the current distributions in HTS tapes. In this method, the current distributions are indirectly found from the results of the field distributions measured by an array of precise pickup coils arranged on the upper surface of the sample tape. To confirm the accuracy and sensitivity of this method, current distributions in a test conductor made of copper wires are measured. Numerical and measured current distributions are compared, and it is found that our method is accurate enough to measure the current distributions in HTS tapes. Using this method, the current distributions in a multifilamentary Ag-alloy sheathed Bi-2223 tape are measured at 77 K. In addition, the effectiveness of our method as detection method of degradation areas of the HTS tapes is examined.