Measurement of the Transverse Resistivity of NbTi and Internal-Tin Nb₃ Sn Strands

A 4-probe method, which directly measures the transverse resistivity in multi-filamentary superconducting strands, has been developed at ENEA. The technique has been applied to NbTi strands in order to compare the results with the ones obtained through indirect approaches. Samples with different external diameters have been considered, for evaluating the effect of the Cu:non-Cu ratio into the wires. For Nb3Sn strands with either a distributed Nb-Ta diffusion barrier design, or with a single Ta diffusion barrier between the filamentary region and the stabilizing copper shell, a detailed mapping of the transverse resistivity of the matrix has been achieved. The temperature and magnetic field dependence of the transverse resistance has been measured for Nb3Sn samples.