Development of Nb/sub 3/Al superconductors for ITER

In the International Thermonuclear Experimental Reactor project, the Nb/sub 3/Al superconductor has been recognized as one of the candidates for the Toroidal Field Coil superconductor. An Nb/sub 3/Al Insert will be tested in the bore of the Central Solenoid Model Coil under ITER Engineering Design Activities. The authors developed the copper stabilized multifilamentary strand using the jelly-roll process for the Nb/sub 3/Al Insert. The strand had Jc above 600 A/mm/sup 2/ at 12 T under the bending strain of 0.4%, the hysteresis loss density lower than the 410 mJ/cc in the alternative magnetic field of +/- 3 T parallel to the wire axial direction and the residual resistivity lower than 1.6/spl times/10/sup -10/ /spl Omega/m. We have developed a large scale multifilamentary billet from which a 16 km wire could be obtained. Total 230 km strands were manufactured from the large scale billet. A yield of 90% was obtained for the wire longer than 500 m and 70% for the wire longer than 1500 m. The maximum unit length reached 4600 m.