Cu-added Nb3Al multifilamentary superconductors having high Jc in high fields

The RHQT (Rapid Heating, Quenching, and Transforming)-processed Nb3Al multifilamentary wire shows not only excellent strain tolerance but also 2-5 time higher J(c) than those of the commercialized Nb3Sn 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 bce supersaturated phase filament formation in the normal RHQT-process. With annealed at 700-800 degreesC, its superconducting properties were improved drastically. The Cu-added Nb3Al multifilamentary wire showed the maximum values of T-c = 18.6 K and H-c2(4.2 K) = 28.7 T, which are higher than the maximum values of T-c = 17.9 K and H-c2(4.2 K) = 25.8 T for the RHQT-processed Nb3Al wire without Cu addition. In addition the new Nb3Al superconductor showed higher J(c) than that of the RHQT-processed Nb3Al wire in high fields above 18 T, maximum J(c) is 360 A/mm(2) at 4.2 K and 21 T.