Nb tube processed Nb/sub 3/Al multifilamentary superconductors

In addition to microstructural studies, various characteristics of Nb tube processed Nb/sub 3/Al multifilamentary (MF) conductors needed in designing superconducting magnets are described. With decreasing Al core diameters of the Nb/Al composite, the formation rate of the A15 phase increased, and its lattice parameter decreased conversely. This was accompanied by an increase in T/sub c/ and H/sub c2/ (4.2 K), suggesting that the small diffusion spacing between Nb and Al facilitates the formation of the metastable A15 phase with stoichiometric composition. On the other hand, both the value of V-I curve and its field dependence decreased with decreasing Al core diameter below 50 nm, which suggests the sausaging of Al filaments in the heavily cold-worked sample. The reversible bending strain range was up to at least 1.4%, indicating the applicability of the react-and-wind method. The degradation in the J/sub c/ (4.2 K, 12 T) of the solenoid with 1.8% winding strain was about 20%. A decrease in temperature from 4.2 to 1.8 K caused an increase of H/sub c2/ by 2.5 T.