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In modeling the properties of superconducting multifilamentary strands, transverse resistivity plays a crucial role in the definition of the coupling losses in ac regime, as well as of the current transfer length, that affects the transport properties of Nb3Sn wires subject to bending strain. We present the first direct measurement of the interfilament transverse resistance in superconducting strands from room temperature to 4.2 K. Results have been compared to the transverse resistance of a sample on which the outer copper stabilization layer has been removed by chemical etching, obtaining interesting indication on the preferential current paths within the wire cross section. An excellent agreement between experimental data and theoretical models has been found in describing the whole strand, while improvements are required in modeling the filamentary region alone.

We report on the effect of bending strain on the transport properties of multifilamentary Nb3Sn strands having twisted or untwisted superconducting filaments in order to clarify some aspects of the current transfer process within the wire cross section. Critical current measurements were performed on internal tin Nb3Sn strands, which were inserted and compacted inside thin stainless steel tubes before the heat treatment. With the application of a maximum bending strain of 0.5%, the strands with twisted filaments present a degradation of the critical current and of the n-index, while an enhancement of the performances is observed for the untwisted strands. The experimental results are interpreted in relation to the predictions of Ekin’s model.