Coil requirements for control plasma shape and divertor flux surfaces in the compact ignition tokamak (CIT)

Coil-position optimization studies were made to determine the desirable locations for coils which can compensate for selected plasma operational disturbances in the Compact Ignition Tokamak (CIT). Control of heat deposition on diverter plates will be dependent on the ability of the coils to respond, for example, the changes in plasma current profiles, in a manner which controls the flux surfaces in the vicinity of the X-point or separatrix. In addition, it may be desirable to use the control coils to continuously oscillate the flux surfaces as they intersect the diverter plates to help distribute the heat load. Results of studies are presented showing the relative effectiveness of different coil locations for these functions. The need for coils internal to the toroidal-field coil system is demonstrated. Contour plots are given that map the region around the X-point in a general way which allows the impact of changing location to be evaluated to estimate changes in coil current requirements and facilitate trade studies.