DEVELOPMENT OF Nb₃Sn SUPERCONDUCTING WIRES FOR AC USE.

The development of P/M (powder metallurgy)-processed Nb//3Sn wires for ac use is reported. The Nb content was chosen as small as 22. 5 wt% to avoid the appearance of interfilamentary coupling inside the wire. The smallest effective diameter d//e//f//f obtained was 37 mu m, while the average diameter of Nb//3Sn filaments was 1 mu m. The critical current density J//c of the filamentary region was 1. 7 multiplied by 10**9 A/m**2 at 4. 2 K at 1 T. A test coil with the coil length of 160 mm, inner diameter of 34 mm and outer diameter of 146. 5 mm was wound by a (3 multiplied by 7)-strand cable of P/M-processed Nb//3Sn wires by the wind-and-react method, and a pulse-mode operation was carried out. A test coil with coil length of 50 mm, inner diameter of 20 mm, and outer diameter 30. 4 mm was also wound by three-strand cable of external diffusion-processed Nb//3Sn wires in the wind-and-react method, and utilized at 60-Hz.