Evaluation of critical current performance of 13 T–46 kA steel-jacketed Nb3Al conductor

A 13 T–46 kA Nb3Al conductor with steel jacket has been developed in the framework of ITER-EDA. The thermal strain will appear on the Nb3Al strands after heat treatment, when the steel jacket is used because of difference in their thermal expansion. The conductor critical current performance is degraded by this process. The critical current performance of this conductor was then studied to verify no degradation during the fabrication and small deterioration in the critical current performance even when the steel jacket is used. The thermal strain is evaluated to be <0.4% for the developed Nb3Al conductor. The critical current deterioration for this case is <10%. Also, the critical current of the conductor without the thermal strain shows good agreement with that calculated by the critical current of a strand multiplied by its number, 1152. Consequently, no degradation during the conductor fabrication process can be verified. Moreover, the critical current is expected to be more than 90 kA for the thermal strain of 0.4%, resulting in a large margin against the nominal current, 46 kA.