Distributed real time control in RFX-mod nuclear fusion experiment: commissioning and first results

The RFX-mod experiment is resuming operation after a five-year shutdown during which significant machine modifications have been done to improve plasma controllability. Its scientific program is focused on the exploitation of innovative plasma control techniques, including magneto-hydrodynamic mode control. To allow a variety of control schemes on the experiment, a distributed, digital, real time control system has been developed and commissioned. This includes a set of computing nodes (currently seven), exchanging data in real time during the plasma discharge. Characteristic figures of the control schemes implemented in the experiment are: pulsed operation with one 200 ms pulse every 10 minutes, large amount of input/output channels (currently about 740 input and 270 output channels), maximum latency time in the range 0.3-2 ms depending on control applications. The paper, after a brief discussion on the system architecture, presents the control operational scenarios, focusing on the system commissioning and the first results achieved in operation.