Cu-added Nb/sub 3/Al multifilamentary superconductors having high J/sub c/ in high fields

The RHQT (rapid heating, quenching and transforming)-processed Nb/sub 3/Al multifilamentary wire shows not only excellent strain tolerance but also 2-5 time higher J/sub c/ than those of the commercialized Nb/sub 3/Sn multifilamentary wires, and is being developed as a new practical superconductor. When the Nb/Al-2at%Cu microcomposite wire was rapidly heated and quenched, disordered A15 phase filaments were formed directly in stead of Nb-Al bcc supersaturated phase filament formation in the normal RHQT-process. With annealing at 700-800/spl deg/C, its superconducting properties were improved drastically. The Cu-added Nb/sub 3/Al multifilamentary wire showed the maximum values of T/sub c/=18.6 K and H/sub c2/(4.2 K)=28.7 T, which are higher than the maximum values of T/sub c/=17.9 K and H/sub c2/(4.2 K)=25.8 T for the RHQT-processed Nb/sub 3/Al wire without Cu addition. In addition the new Nb/sub 3/Al superconductor showed higher J/sub c/ than that of the RHQT-processed Nb/sub 3/Al wire in high fields above 18 T. The maximum J/sub c/ is 360 A/mm/sup 2/ at 4.2 K and 21 T.