Superconducting property of Nb/sub 3/(Al, Ge) conductors prepared by diffusion process

Nb/sub 3/(Al, Ge) conductors were prepared with a diffusion reaction process at a temperature around 1400/spl deg/C, from multifilamentary Nb/Al-25at%Ge precursors. Critical current densities of 300 A/mm/sup 2/ at 21 T and 220 A/mm/sup 2/ at 23 T at 4.2 K have been obtained after a diffusion reaction at 1400/spl deg/C for 7 h followed by 10 h/800/spl deg/C heat treatment. The H/sub c2/ in excess of 28.5 T is about 2 T larger than that of the so-called RHQT Nb/sub 3/Al. Large Al-Ge filament size in the precursors over a few microns might be acceptable to improve high-field J/sub c/ performance, significantly reducing fabrication difficulty of the Nb/Al-Ge precursors. Small matrix ratio of 0.8 and piece-length of 30 m was achievable in the precursor preparation at our laboratory workshop without intermediate annealing. In addition, the current capacity up to values higher than 300 A at 21 T, 4.2 K has been given by an enlarged cross-section sample.