Performance enhancement under bending of Nb3Sn strands with untwisted filaments.

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. [ABSTRACT FROM AUTHOR]