Development of RHQ-processed Nb3Ga wire

Nb 3 Ga wires fabricated by using RHQ (rapidly heating and quenching) treatment show T c = 29.7 K and B c2 (4.2 K) = 32 T. In addition J c of the Nb 3 Ga phase is very high, comparable to those of practical (Nb, Ti) 3 Sn wire and RHQT-processed Nb 3 Al wire. However we cannot obtain the large overall J c for the wire, because of small volume fraction of Nb 3 Ga in the wire. By using Ta-matrix Nb 3 Ga precursor wire, we performed the RHQ treatment at higher temperatures, resulting in two-times improvement of overall J c and a little improvement in J c . We measured temperature dependence of J c vs. B curve for the Nb 3 Ga wire. The pinning force vs. B curves did not show any agreement with Kramer's scaling law. TEM observations clarified that the composition of Nb 3 Ga varies from near-stoichiometry (24at%Ga) nearby the Nb 5 Ga 3 phase to Ga-poor composition (21.8at%) nearby the Nb-Ga bcc phase. We also measured the tensile strain effect on the superconducting properties of Nb 3 Ga wire. The strain effect of Nb 3 Ga wire is as large as that of Nb 3 Sn wire.