Real-time active control of RFX-mod plasma equilibrium

The design and implementation of a real-time control system of the plasma equilibrium was required in RFX-mod, the load assembly of the machine being characterized by a thin copper shell to prevent the growth of MHD resistive wall modes with a time constant much shorter than the typical pulse length. The control system design was carried out on a linearized model of the plasma response. Detailed schemes were developed to use a tool for automatic code generation to implement the regulators. Dedicated vacuum and plasma pulses were executed for system commissioning and characterization. The first results showed the system satisfactory accuracy in tracking the plasma position reference and its contribution to extend the pulse length. A modified version of the control system aimed at keeping the shell surface as a flux surface throughout the pulse was also successfully tested.