Electromagnetic modeling for the active control of MHD modes in RFX

The new RFX load assembly is characterized by a thin copper shell with a 50 ms time constant, for the vertical field penetration, and 192 active saddle coils all around the torus. The active control of resistive wall modes (RWMʹs) is considered a basic issue to extend the pulse duration to its nominal value. An open loop state space model was developed in view of the simultaneous control of different harmonic components of the magnetic field. It integrates a lumped parameter electromagnetic model of the saddle coil system and a linear model of the plasma magneto-hydro-dynamic (MHD) evolution. Reduction techniques have already been tested in order to obtain a model suitable for the design of the control system of the plasma modes.