Development of a (NbTi)/sub 3/Sn strand for the ITER CS scalable model coil

As the first step in development of the center solenoid (CS) scalable model coil for the International The monuclear Experimental Reactor (ITER), development of a (NbTi)/sub 3/Sn strand with characteristics of high current density and low AC loss was started by the Japan Atomic Energy Research Institute (JAERI). One of the targets of strand development was set at the point where current density (J/sub c/) was more than 800 A/mm/sup 2/ at 12 T and effective filament diameter (d/sub eff/) was less than 10 mu m. The other target decided by JAERI was the point of more than 600 A/mm/sup 2/ for J/sub c/ and less than 3- mu m d/sub eff/, because it is possible to design the coil by using this strand performance. The 0.92-mm-diameter (NbTi)/sub 3/Sn strands were fabricated by a bronze process, a Nb tube process, and an internal tin diffusion method to attain one of two targets. Strand performance of about 800-A/mm/sup 2/ J/sub c/ at 12 T and about 5- mu m d/sub eff/ was obtained. The results from critical current measurements and effective filament diameter measurements are presented.<>