Superconducting cable joint resistance

This paper reports on results of a parametric study of the 4.2 K resistance of lap joints between two 27-strand cables of multifilamentary Nb3Sn wire. All joints were between ribbon terminations made rolling copper-encapsulated cable ends flat. Resistances as functions of current were inferred from current decay time constants of cable-in-conduit conductor loops connected by the joints. The resistances of twenty three samples were measured (range of 0.2 to 3 nΩ). It was found that lap joint resistance was a function of current. The influences of solder versus no solder, solder thickness, indium versus tin-lead, ribbon surface oxidation, solder flux, cable twist pitch, wire chrome plating, clamping pressure during heat treatment, ribbon aspect ratio, and joint length are reported