Study of Critical Current and n-Values of 2G HTS Tapes: Their Magnetic Field-Angular Dependence

Abstract

Since many applications of YBCO tapes operate in external magnetic fields, it is necessary to investigate the magneto-angular dependence of critical current and n-values in coated conductors. In this paper, five commercial YBCO tapes with different microstructures produced by three different manufacturers are chosen. The selected samples have width of 2.0, 4.0, 4.8, 6.0 or 12mm, with copper, brass or stainless steel laminations. The critical current density dependence Jc (B,θ) and n-values characteristics n(B,θ) of the tapes are comprehensively measured under various magnetic fields and orientations. Afterwards, the obtained experimental data sets are successfully fitted using a novel multi-objective model which considers the material anisotropy. By using this approach a fitting function Ic (B,θ) can always be obtained to accurately describe the experimental data, regardless of the fabrication and width differences of the superconducting tapes. Moreover, our experiment shows that when subject to different external magnetic fields, the angular dependence of n-values characteristics are directly correlated with the corresponding critical current profiles. Our results are helpful to predict the critical current of electromagnetically interacting 2G HTS wires and thereby improving the design and performance of the devices made from YBCO tapes.