Mass Production of Nb–Ti Conductors for EF Coil and Feeder of JT-60SA

Nb-Ti conductors will be used for equilibrium field (EF) coils and the feeder of JT-60 Super Advanced (JT-60SA). The conductors were fabricated by pull through and compaction method. Round jackets were butt welded to a long length jacket. Then, the cable was pulled into the jacket. Finally, the conductor was formed into a square shape. Sixty-four conductors were produced. Dimensional measurements at both ends of 2183 jackets showed that the inner diameters of each production series were within ±0.1 mm. There were 2175 welding joints in total. Cut and rewelding, according to the failure detected by inspections, occurred 30 times. The maximum pulling forces through a jacket was 8.3 kN. The range of coefficients of friction for pulling was from 0.50 to 0.86. The outer dimension just after compaction satisfied the specification of ±0.2 mm in tolerance. The height of the conductor was increased by 0.19 mm in average by bending of 1.5 m in curvature radius. This modification did not affect the coil manufacturing. The minimum mass flow rate among the same EF coil's conductors was 93.5% of the average value. It was decided that orifices to uniform helium parallel flows inside coil are not used for coil manufacturing.