Reaction of Nb3Sn wires in an Icology 908 conduit in the presence of oxygen can decrease the conduit's fracture toughness. This may be avoided by reacting in a reducing atmosphere of 5% hydrogen-95% argon. The effects of the hydrogen reaction on the superconductive properties of bronze-process and internal-tin-process Nb3Sn wires were investigated. Compared with the standard heat treatment in partial vacuum, critical currents decreased in the bronze wire by 12% at 12 T and 14% at 5 T, and in the internal-tin wire by 4% at 12 T and 10% AT 8 t. Hysteresis losses over a ±3 T field cycle were reduced by 14% for the bronze wire and by 8% for the internal-tin wire by the hydrogen heat treatment, approximately proportional to the reduction in critical current. The critical temperature was reduced by 0.5 K. There was no significant effect on the residual resistivity ratio of the stabilizing copper.
Citation: Advances in Cryogenic Engineering
Pub Type: Journals
hysteresis losses, niobium-tin, superconductors, critical current, hydrogen gas