Fabrication and properties of PIT Nb-Al and Nb-Sn based superconductors

Multifilamentary PIT Nb-Al and Nb-Sn strands have been fabricated and tested. Three main conductor variants were investigated; Nb/sub 3/Al, Tube-Wall-Reaction (TWR) Nb/sub 3/Sn, and Internal Reaction (IR) Nb/sub 3/Sn. Multifilament restacks of 7, 19, 30, and 37 filaments were fabricated and tested. The powders were formed by mechanical alloying in a planetary mill with subsequent jet milling for particle refinement. In the case of Nb/sub 3/Al, ductile Al was added to the intermetallic compound before filling; while for Nb/sub 3/Sn based conductors, Cu was added. All Nb/sub 3/Sn strands were alloyed with Ta. Phase formation and transport properties are described. In the case of TWR Nb/sub 3/Sn strands, the nature and thickness of the reaction layer was investigated. For monofilaments, the reaction layer was roughly 50 (mu)m thick, for 37 filament strands it was only 5 (mu)m. SC layer J/sub c/ values of 2680 A/mm/sup 2/ at 12 T were obtained, but quench limited because of the short samples used in the present work.