Nb3Sn conductor development for fusion power applications

The progress of Nb3Sn conductor development for fusion power applications at JAERI is described. The superconductor development was carried out in connection with the research and development for four fusion coil development projects: Phoenix, Cluster test, Demo Poloidal Coil and ITER-EDA. In the Phoenix project, the reliable production of multi-filamentary Nb3Sn strands was established during the development work towards realizing a 18 T coil, and an 18 T generation coil (BC-18) with multi-filamentary Nb3Sn strands was successfully operated at 4.2 K for the first time in the world. In the Cluster Test project, a pool-cooled Nb3Sn conductor with a high heat-flux surface, and the first 1-m class bore Nb3Sn coil (TMC) in the world was constructed and operated up to 12 T. In the Demo Poloidal Coil project, which was constructed to demonstrate the possibility of a poloidal coil, a forced-cooled Nb3Sn conductor was developed. The Nb3Sn coil (DPC-EX) constructed with it was pulse-operated up to 7 T in 0.5 s. Finally, in the ITER-EDA project a CICC-type 13 T-46 kA Nb3Sn conductor was developed. A Central Solenoid Model Coil (CSMC) was fabricated using it and successfully operated up to 13 T with 0.4 T/s. (author)