Experimental Verification of the Temperature and Strain Dependence of the Critical Properties in Nb3Sn Wires

The critical current density in NbJSn conductors is described with an improved scaling formula for the temperature, magnetic field and strain dependence. In an earlier study it is concluded that the largest uncertainties in this description arise from the temperature dependence that is described with various slightly different empirical relations. For the optimization of the numerical codes, used to predict the stability of large magnet systems, a more accurate description is required. Therefore, two different bronze processed conductors for the ITER CS model coil are analyzed in detail. The critical current is measured at temperatures from 4.2 K up to the critical temperature, in magnetic fields from 1 T to 13 T and with an applied axial strain from -0.6 % to +0.4 %. The axial strain is applied by a U-shaped bending spring and a comparison is made between brass and Ti-6A1-4V, as substrate material.