Critical current vs. strain measurements of long length Nb3Sn wires up to 1000 A and 17 T using a modified Walters spring

We report on a new device for measuring the variation of the critical current as a function of the uniaxial strain in Nb₃Sn industrial wires. This device offers the possibility of measuring large critical currents (up to 1000 A) on long superconducting wires (about 0.8 m), thus allowing to use the 0.1 μV/cm criterion. The WASP is built out of a titanium alloy, enabling strains up to 1.4% at 4.2 K to be applied. In our design, and in contrast to the original Walters spiral, the superconducting wire lies in a machined groove and is only soldered to Cu contacts at both ends. The strain applied on the wire is directly measured by means of strain gauges. With this new device, the variation of I_c(ε) for Nb₃Sn wires with rectangular cross section as large as 1.56×1.02 mm²(I_cmax=708 A at 13 T) have been successfully measured for the first time.