Anisotropy and angular dependence of critical currents in rectangular Nb3Sn superconductors made by the bronze method

Publisher Website
Google Scholar
Abstract
An experimental study of the critical current angular dependence in flat mono- and multifilament bronze-processed Nb3Sn wires, oriented in different directions in a transverse magnetic field, is presented. The influence of various parameters, such as the shape aspect ratio and the heat treatment time and temperature, is examined. It is shown that in monofilament wires, the critical current anisotropy, defined as the ratio of the currents in the parallel and perpendicular orientations of the flat face to the magnetic field, is greater than one at low heat-treatment conditions and changes to less than one with more intensive heat treatment. The multifilament wires behave in the same manner, except that the effects of the gentle and intensive heat treatments are related to the filament size. The mechanical deformation of the niobium core determines the character of the anisotropy at relatively low heat-treatment conditions, while the morphology of the grown Nb3Sn layer is decisive at more intensive heat treatment. The critical current anisotropy of flattened conductors is very important from the theoretical (pinning) as well as from the technical (magnet winding) point of view.