The development of ITER TF model coil heat treatment conditions

The Russian Toroidal Field (TF) Coil-Insert for a model coil of the Central Solenoid (CS) with Nb₃Sn cable-in-conduit conductor (CICC) in the Ti conduit was created in frame of the International Thermonuclear Experimental Reactor (ITER) Project. The schedule of Nb₃Sn CICC heat treatment was developed and optimized during preliminary study. Heat treatments of Nb₃Sn CICC sample and "dummy" CICC (the "dummy" CICC spiral was identical to the Nb₃Sn one with one exception: the copper wires with Cr-covering of the same size were used instead of the Nb₃Sn strands) were performed. The results of the study of the CICC elements, including jacket material, before and after heat treatment are described. The heat treatment conditions were developed and the heat treatment regulations were corrected on base of the results obtained.