ジェリーロール法Nb<SUB>3</SUB>Al超電導線の特性と実用化の実証

Abstract

The Nb3Al superconductor has been expected to the application under the high field, such as the one for International Thermo-nuclear Experimental Reactor (ITER), from the standpoint of superior characteristics of Ic 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 microstructure of Nb-Al compound has been studied and a non-copper critical current density Jc of more than 800 A/mm2 at 12 T, 4.2 K was achieved. Further, a higher upper critical field Bc2 of 23.1 T and a higher Jc of 1130 A/mm2 at 12 T, 4.2 K were achieved by the 2-stage heat treatment.The residual resistivity ratio of the wire was over 400, and even with Chrome plating, it was over 100.For the field perpendicular to the wire length, the effective filament diameter was almost equal to the actual filament diameter. On the other hand, the hysteresis 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 Jc-B-T characteristics were measured.In order to demonstrate the applicability to the large current conductor, the 40 kA-class Cable-in-Conduit conductor and the 12 T-10 kA-100 m class long length Cable-in-Conduit conductor, of which conduit is titanium, were fabricated. Recently, the conductor for the ITER TF coil was fabricated and the Jc-B-T characteristics were measured at the SULTAN facility in Switzerland.We 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%.