Multifilamentary Nb3Sn wires reacted in hydrogen gas

Reaction of NbsSn wires in an Incoloy 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 pct hydrogen-95 pct 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 pct at 12 T and 14 pct at 5 T, and in the internal-tin wire by 4 pct at 12 T and 10 pst at 8 T. Hysteresis losses over a +/- 3 T field cycle were reduced by 14 pct for the bronze wire and by 8 pct 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. (Author)