Development of RHQ-processed Nb/sub 3/Ga wire

Nb/sub 3/Ga wires fabricated by using RHQ (rapidly heating and quenching) treatment show T/sub c/ = 29.7 K and B/sub c2/ (4.2 K) = 32 T. In addition J/sub c/ of the Nb/sub 3/Ga phase is very high, comparable to those of practical (Nb, Ti)/sub 3/Sn wire and RHQT-processed Nb/sub 3/Al wire. However we cannot obtain the large overall J/sub c/ for the wire, because of small volume fraction of Nb/sub 3/Ga in the wire. By using Ta-matrix Nb/sub 3/Ga precursor wire, we performed the RHQ treatment at higher temperatures, resulting in two-times improvement of overall J/sub c/ and a little improvement in J/sub c/. We measured temperature dependence of J/sub c/ vs. B curve for the Nb/sub 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/sub 3/Ga varies from near-stoichiometry (24at%Ga) nearby the Nb/sub 5/Ga/sub 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/sub 3/Ga wire. The strain effect of Nb/sub 3/Ga wire is as large as that of Nb/sub 3/Sn wire.