Poloidal magnetics of compact ignition tokamaks

The present compact ignition tokamak (CIT) design point (R = 1.225 m, a = 0.454 m, B = 10.4 T, I = 10 MA) is optimized with respect to device size for limiter operation. The CIT poloidal field (PF) system is designed for both limiter and divertor (at I = 9 MA) scenarios. Forming a poloidal separatrix within the limiter vacuum chamber requires a divertor plasma elongation κ = 2.0 and almost twice the PF energy as the limiter case. This study examines the dependence of PF system characteristics on the plasma elongation within the context of design points optimized for divertor operation. It is shown that higher elongation κ = 2.0 considerably simplifies the CIT poloidal magnetic systems subject to device design constraints