Influence of Deviatoric Strain for Superconducting Parameters of Nb₃Sn Wires

The tensile strain dependence of the upper critical field Bc2for Nb3Sn wires was measured using a new apparatus for applying tension at low temperature. The critical current Iccalculated from the strain-dependent Bc2measurements is the almost consistent with the measured Ic. In the measurements by a new apparatus, the axial and the lateral applied strains were examined by the strain gauges attached onto the wire. The deviatoric strain epsivdevand the hydrostatic strain epsivhydwere estimated by the axial and the lateral strain. We found the deviatoric strain dependence of Bc2is different between the tensile and compressive strain states. This means that the hydrostatic strain also should be taken into account in order to understand the strain effects on the superconducting properties of Nb3Sn.