Effect of heating and bending on localized critical current in 2G HTS tapes with non-contact trapped field measurements

Abstract

Current-voltage measurement (I–V curve) is a typical method to identify the critical current (Ic) of second-generation high-temperature superconducting tapes (2G HTS tapes). However, it is difficult to characterize the local Ic of 2G HTS tape on the millimeter (mm) scale due to the set spacing of the voltage electrodes (several centimeters), so non-contact trapped field distribution measurements have been used to define local defects in Y–Ba–Cu–O bulks and 2G HTS tapes, especially for the quality analysis for long lengths of 2G HTS tapes. In order to discuss the possible degradation of 2G HTS tape during heating and bending (both important parameters in joining process), this study used both trapped field measurement and I–V measurement to characterize the effect of heating (190 °C–230 °C) and bending (radius = 3.75 mm–22.35 mm) processes on the degradation of 2G HTS tape Ic. In addition, according to electromagnetic calculations, the local Ic (within a few millimeters) of the 2G HTS tape can be obtained from the flux density and distribution of the trapped magnetic field. Comparing the two sets of Ic measurements showed very good agreement. This study demonstrates the accuracy of optimized heating and bending parameters as well as spatial position and local Ic values of processed 2G HTS tape through non-contact trapped field measurements.