Construction of the JFT-2M TOKAMAK (4) -- design and fabrication of coil system --

The JAERI TOKAMAK-JFT-2M is a large piece of equipment that has a main structure weighing 230 tons and consists mainly of coil systems that include iron cores. The main parts of the design, developmental tests, and the fabrication of these coils are described. The experiment on JFT-2M is in two stages; the current Phase I and the upgraded Phase II, but the toroidal field (TF) coils, S1 through S3 and H coil are scheduled to be used also in Phase II. The TF coils that consists of 16 coils and weighs 56 tons are made in D-shape to conform to the cross-sectional shape of the plasma. To be able to withstand the strong electromagnetic force applied in the Phase II tests, these coils were designed as canned coils, and the conductors were designed with as large as possible cross sections to limit heating. The direct support of the inward magnetic force by the center iron core is among the unique features of the system. Among the 9 types of PF coils, the ones inside the TF coils and the ones outside have completely different design objectives. The iron core consists of 4 blocks. The circular core at the center has OH and B coils. To support the inward magnetic force of the TF coils, the center core was designed and fabricated with high rigidity despite its laminated structure