Analogue feedback control system of RFX

The paper deals with the design and the experimental results of the first feedback control system of the main plasma quantitites for a reversed field pinch (RFP) machine. It was designed for RFX (Reverse Field eXperiment), the largest presently operating RFP device. The peculiar aspects of RFP with respect to Tokamaks are highlighted by considering their influence on the specifications of the control system design and the choice of the controlled quantities. Three feedback loops were implemented: the control of the plasma current, the toroidal magnetic field at the wall and the poloidal magnetic field configuration. The main purpose of the last loop is to minimize the field errors at the poloidal cuts of the conducting shell which surrounds the RFX vacuum vessel. The evaluation of the transfer functions of the systems and the regulator design are presented together with the experimental results obtained till now. The validation of the models used for the regulator synthesis was also performed and its results are reported.