Dynamic simulator of RWM control for fusion devices: modelling and experimental validation on RFX-mod

A new integrated simulator for experiments of resistive wall mode (RWM) closed-loop control and its benchmark against experimental data are presented. The numerical tool couples in a self-consistent way a full 3D finite element description of the machine boundaries (Cariddi code), a 2D toroidal model of RFP plasma stability (MARS-F code) and a realistic representation of the RFX-mod control system producing an overall dynamic model cast in the state variable space. In this way a full dynamic 'flight simulator' of RWM control experiments has been implemented where the interaction of proportional-integral-derivative controller gains and plasma equilibrium parameters can be explored. As an application of the new integrated tool, closed-loop RWM stability analyses have been benchmarked against experimental data. In this way it was possible to experimentally prove that the control simulator correctly reproduces closed-loop RWM growth rates under different control conditions. Time domain simulations were also run to assess the overall accuracy of the model including the presence of non-linear blocks. The achieved results are discussed in connection with the broader international effort towards an effective control of RWMs in both tokamak and RFP configurations.