Influence of Wire Parameters on Critical Current Versus Strain Characteristics of Bronze Processed ${\hbox {Nb}}_{3}{\hbox {Sn}}$ Superconducting Wires

Abstract

In order to develop bronze processed Nb3Sn wire for the ITER CS coil operating under higher compressive strain, the influence of various parameters of wires such as filament diameter, barrier materials, barrier thickness, heat treatment pattern and Ti addition on critical current (Ic) versus intrinsic strain eν(-1.0% <; eν <; +0.1%) characteristics was investigated. The change of these parameters brought significant changes to superconducting properties such as Ic and n-value. In spite of different wire parameters, the strain dependency of normalized Ic was almost the same, except that a Ti addition affects the upper critical field Bc2. This result suggests that assuming the same Ti-addition level, Nb3Sn wire with higher performance at a certain eν would exhibit higher performance at any eν in the compressive regime. Based on the result, bronze processed Nb3Sn wires with non-Cu critical current density more than 1100 A/mm2 at 12 T, 4.2 K, zero applied strain have been successfully developed for the CS coil.