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

Coal position optimization studies have been done 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 divertor plates will be dependent on the ability of the coils to respond, for example, to changes in plasma current profiles or β 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 divertor plates to help distribute the heat load. This paper presents the results of studies showing the relative effectiveness of different coil locations for these functions. The need for coils internal to the toroidal field coil system is demonstrated. In addition, contour plots are given which 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