The History and Future of A15s in Japan

Tapes and wires of V/sub 3/Ga were first made in Japan based on the discovery of the effect of Cu additive for the promotion of V/sub 3/Ga synthesis. The bronze process applied to V/sub 3/Ga was extended to the fabrication of Nb/sub 3/Sn. The Ti addition to the bronze matrix was also initiated in Japan so as to improve significantly high-field performance. The so-called internal tin and Nb tube processes were also initiated in Japan. These achievements on V/sub 3/Ga and Nb/sub 3/Sn lead into the recent active development of high-field, large-scale, and refrigerator-cooled superconducting magnet applications. As for Nb/sub 3/Al, which shows excellent strain tolerance, various approaches were made in Japan to achieve stoichiometry and fine grain structures. Among them the Jelly-Roll process is the most reliable method to produce long-lengths of Nb/sub 3/Al wire for fusion uses. High performance Nb/sub 3/Al conductors for high-field use are being produced by the rapidly heating, quenching and transformation annealing (RHQT) process. Future progress in the A15 conductor development in Japan may be expected through improved processes.