Asymmetric angular dependence of Jc in coated conductors prior to and after fast neutron irradiation

Abstract

Angular dependent measurements of Jc were performed on a commercial coated conductor (SuperPower) consisting of a 1μm thick YBCO layer grown on a MgO IBAD buffer layer. An asymmetric behavior of the angular dependence of Jc (Jc(Ф)) was found with a changing distance between the two peaks at different temperatures and applied magnetic fields. One peak always occurs when the field is oriented parallel to the tape surface, the other smaller peak is located in the perpendicular orientation at high fields, but slightly shifted (by up to 10°) at 77K and low magnetic fields. This peak shift, the overall Jc(Ф) asymmetry and the influence of fast neutron irradiation on Jc(Ф) are discussed. The spherical defects, introduced by collisions of fast neutrons with the lattice atoms, are randomly distributed, add to the as-grown defect structure and change the critical current anisotropy by altering both peaks.