Power Supply for NSTX Resistive Wall Mode Coils

The National Spherical Torus Experiment (NSTX) has been designed and installed in the existing facilities at Princeton Plasma Physics Laboratory (PPPL). Most of the hardware, plant facilities, auxiliary sub-systems, and power systems originally used for the Tokamak Fusion Test Reactor (TFTR) have been used with suitable modifications to reflect NSTX needs. Until 2004, the NSTX power system was feeding twelve (12) circuits in the machine. In 2004, resistive wall mode (RWM) coils were installed in the machine to suppress resistive wall modes and to correct error fields. There are six of these coils installed around the machine on the mid-plane. Since these coils need fast and accurate controls, a switching power amplifier (SPA) has been procured, installed and commissioned along with other circuit components. One of the existing thyristor rectifiers is used as the DC source to the SPA. The controls for the RWM have been integrated into the overall computer control of the DC power systems for NSTX. This paper describes the RWM power supply for NSTX