The inter-strand contact resistance of Nb₃Sn cable-in-conduit conductor with hydrocarbon oil

The inter-strand contact resistance (RC) of Nb3Sn cable-in-conduit conductors (CICCs) is a very important parameter which strongly correlates with ac losses and current redistribution behavior of the CICCs. One way to obtain the desired RC is to apply a layer of hydrocarbon oil on the Nb3Sn strands before the CICC Nb3Sn reaction heat treatment. In this paper, we measured RC for a Nb3Sn CICC sample fabricated with hydrocarbon oil. The measurements were performed using an apparatus designed to apply transverse load and load cycling on CICCs at 4.2 K. Resistances RC between strands of different cabling stages were measured with transverse load up to 188 kN m−1 and load cycles up to 10 000. The results show that RC of the sample increases almost linearly with the first loading. With load cycling, RC increases rapidly at first, but becomes saturated after ~100 cycles. After 10 000 load cycles, RC decreases with increasing load at a decreasing rate. These behaviors are comparable to observations for CICC with Cr plated strands reported in the literature. Therefore from the RC point of view, Nb3Sn CICCs with hydrocarbon oil on strands may be used as a low cost alternative to CICCs with Cr plated strands.