Improvements of the RFX - mod power supply system for MHD mode control

RFX - mod is a Reversed Field Pinch (RFP) machine for plasma confinement operating at up to 2MA plasma current. Key feature of RFX - mod is the large number of saddle coils (192) that completely cover the outer surface of the stabilising shell and allow the generation of precise local magnetic field to control the plasma instabilities. Each coil is fed by a dedicated switching inver ter with onboard full - digital control. For more than one decade since its installation, this power supply (PS) system has being showing a very effective and versatile control of MHD modes in many RFX - mod plasma scenarios: mitigation of Tearing Modes, contr ol of spontaneous RFP helical states and Resistive Wall Modes. A central MHD mode control system generates in real - time the 192 reference signals to drive the inverters. Recently a new faster central system based on the MARTe real - time package has been imp lemented. To take advantage of the effectiveness of the new control, an improvement of the PS dynamics is devised. To the purpose, a review of the inverter control has been undertaken with the main objective of reducing the latency. Furthermore, the possib ility to operate the inverters in open loop mode has been studied, to achieve a faster response of the overall control system of the MHD modes. The paper will report the analyses and preliminary experimental results for both solutions.