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

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 (I_c) versus intrinsic strain ε_ν(-1.0% <; ε_ν <; +0.1%) characteristics was investigated. The change of these parameters brought significant changes to superconducting properties such as I_c and n-value. In spite of different wire parameters, the strain dependency of normalized I_c was almost the same, except that a Ti addition affects the upper critical field B_c2. This result suggests that assuming the same Ti-addition level, Nb₃Sn wire with higher performance at a certain ε_ν would exhibit higher performance at any ε_ν 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.