Experimental and Theoretical Analysis of Transverse Resistances in a Nb3Sn LMI-EM Strand

In Nb3Sn strands, hundreds or thousands of fine superconducting filaments are embedded in a metallic matrix for thermal and electrical stabilization. The transverse electrical resistivity between filaments plays a fundamental role in determining the ac losses, the thermal stability, and the current transfer length of the wire. The direct measurements of the transverse electrical resistances give useful information both for stability computations and to analyze the mechanical performance of the wire. In this paper, the interfilament resistances measured with a four-probe technique on a Nb3Sn wire produced by Europa Metalli have been interpreted through a simulation code. A 2-D finite element method model of the wire cross-section and of a 3-D electrical circuit model of the wire sample have been applied to derive qualitative and quantitative information about the transverse electrical resistance matrix. A comparison with measurements performed on a Nb3Sn wire with a different configuration shows the relevance of the wire layout in determining the interfilament resistance between filament bundles.