The CIT toroidal field coil and structure design and assembly approach

The Compact Ignition Tokamak (CIT) toroidal field (TF) coils are capable of providing an 11-T field at a plasma major radius of 2.1 m. The plasma current will be about 12 MA. The TF coil design is based on a bucked inner leg support concept. The liquid-nitrogen-precooled TF coils are constructed of Bitter plates and are fully encased. The bucking cylinder and the TF inner case designs are integrated into a toroidally continuous structure which also provides radial support for the ohmic heating solenoid. The all-welded support structure and coil cases are made of low-nickel austenitic stainless steel. Reinforced copper or copper-alloy conductors are required for the coils to withstand the high stresses induced by the magnetic forces and thermal fields. An important design consideration is the effect of distortion in the structure due to final welding at assembly. The assembly method presently described was selected from several alternates to minimize field welding and permit staged overlapping of the TF coil/structure and the vacuum vessel fabrication, delivery, and assembly schedules. In addition to the description of the TF coil and structure design and assembly sequence, the R&D programs leading to the qualification of the selected welded assembly method are described