THE CHARACTERISTICS AND DEMONSTRATION ON NB3AL SUPERCONDUCTOR MADE BYTHE JELLY-ROLL PROCESS

The Nb3Al superconductor has been expected to the application under th e high field, such as the one for International Thermo-nuclear Experim ental Reactor (ITER), from the standpoint of superior characteristics of J(c) under mechanical stress. We have established the manufactuing technology for long length Nb3Al wire by the Jelly-roll process, which is the most suitable method for the practical superconductor. The mic rostructure of Nb-Al compound has been studied and a non-copper critic al current density J(c) of more than 800 A/mm(2) at 12 T, 4.2 K was ac hieved. Further, a higher upper critical field B-c2 of 23.1 T and a hi gher J(c) of 1130 A/mm(2) at 12 T, 4.2 K were achieved by the 2-stage heat treatment. The residual resistivity ratio of the wire was over 40 0, and even with Chrome plating, it was over 100. For the field perpen dicular to the wire length, the effective filament diameter was almost equal to the actual filament diameter. On the other hand, the hystere sis loss for the parallel field was around one-fourth as large as that for the perpendicular one. For studying the applicability of Nb3Al to practical use, the stress-strain effect, mechanical properties and J( c)-B-T characteristics were measured. In order to demonstrate the appl icability to the large current conductor, the 40 kA-class Cable-in-Con duit conductor and the 12 T-10 kA-100 m class long length Cable-in-Con duit conductor, of which conduit is titanium, were fabricated. Recentl y, the conductor for the ITER TF coil was fabricated and the J(c)-B-T characteristics were measured at the SULTAN facility in Switzerland. W e are now fabricating more than 250,000 m wires for ITER Nb3Al Insert. In the prototype billet for ITER, the yield of the piece length over than 1500 m was greater than 90%.