Poloidal field coil system optimization for the Compact Ignition Tokamak (CIT)

In the Compact Ignition Tokamak (CIT) design, the poloidal-field coil system (PF) is located symmetrically about the Z=0 plane. The system consists of seven pairs of coils external to the toroidal-field coil system, (TF), and two pairs of coils internal to the TF coils. The external PF coil system has three coils making up the central solenoid, and four ring coils. Previous designs for CIT called for a self-supporting central solenoid (called wedged design because the TF coil inner legs wedged under the radial inward loading) and a PF system capable of providing a flux swing and equilibrium and shaping fields for an 11 MA plasma. The current (bucked) design calls for a 12.3 MA plasma with a central solenoid that is partially supported by, and partially supports, the TF coil inner legs. A comparison of the two design options is made from the PF coil system standpoint. The operating points and structural and thermal requirements of the central solenoid lead to the selection of different conductors for the two cases