Impact of the Design Point on the Poloidal Field Coil System for the CIT (Compact ignition Tokamak)

The poloidal field (PF) coil system in a tokamak must provide the flux swing and the equilibrium and shaping field distributions required to create, maintain, and control the plasma during the discharge. The present design for CIT calls for an 11.8 MA plasma in a double null configuration with a major radius of 2.59 m, a minor radius of 0.795 m, and an elongation (at the 95% flux surface) of 2.0. The toroidal field at the major radius is 9 T. The central solenoid is self-supporting and the TF coils wedge under the Lorentz load. The previous design point called for the TF and PF to buck against each other in order to lower the stresses in both. That design called for an 11 MA, 10 T plasma with a major radius of 2.14 m and a minor radius of 0.66 m. The impact on the PF system of this change in the design point is assessed.