Field computations for DIII-D RWM stabilization coil systems

Stabilization of the resistive wall mode (RWM) is seen by fusion researchers as central to the ability to operate modern experimental devices in advanced tokamak (AT) regimes. On DIII-D first the external "C-" and now the internal "I-coil" arrays have been used in both static and dynamic RWM stabilization experiments. A suite of analysis routines was developed to analyze the magnetic fields produced by these two coil systems in realistic three-dimensional (3D) geometries. With these routines we are able to look at possible operating scenarios of the coil arrays, individually or in combination, and compare the fields produced by the coils to mode patterns from theoretical ideal-MHD calculations. These types of analyses can be an extremely valuable tool during the coil system commissioning and experiment startup process where there are uncertainties regarding installation details and connection of the various hardware components that comprise the complete system.