AbstractThe experiments proposed with active MHD mode control in RFX require the installation of new saddle coils and the substitution of the present thick stabilizing shell with a much thinner one. In this framework, the dynamic behaviour of plasma, shell and poloidal field circuit has been simulated to verify the operating scenarios of the modified machine, the dynamic control of plasma axisymmetric equilibrium and on the gas ionisation conditions, also based on the past operation experience. The results have given indications and constraints for the design of a layout, which assures the existence of an operating region compatible with both plasma active position control and gas ionisation.