Influence of wire parameters on critical current versus strain characteristics of bronze processed NbSn superconducting wires

Miyatake, Takayuki*; Murakami, Yukinobu*; Kurahashi, Hidefumi*; Hayashi, Seiji*; Zaitsu, Kyoji*; Seeber, B.*; Mondonico, G.*; Nabara, Yoshihiro

In order to develop bronze processed NbSn strands for ITER TF and CS coils, the influences of various parameters of NbSn strands such as filament diameter, barrier materials, barrier thickness, heat treatment pattern and Ti addition on critical current () vs. axial strain characteristics were investigated. The change of theses parameters brought significant changes to superconducting properties involving and n-value at zero applied strain. In spite of different strand parameters, the strain dependency of normalized was almost the same, except for Ti-addition affecting the critical field . Based on the results, bronze processed NbSn strands with non-Cu critical current density more than 1,100 A/mm at 12T, 4.2K have been successfully developed for the CS coil.