Electromagnetic Response of RFX-mod2 Passive Conducting Structures to Fast Termination of High-Current RFP Plasma

The electromagnetic response of the toroidal conducting structures surrounding the plasma of the RFX-mod2 experiment is investigated during the fast termination of a high-current reversed field pinch plasma discharge. The plasma equilibrium is self-consistently computed for each time instant, including the effect of the eddy currents. These are evaluated in the passive conductors together with the related electromagnetic forces. The magnetic fields at the sensor positions are also evaluated.

A comparative analysis of the plasma dynamics between the RFX-mod2 and its predecessor, RFX-mod, is conducted by isolating the electromagnetic contributions from each component of the system, including the plasma, active coils, and eddy currents. During fast termination, eddy currents up to 6 kA are induced in the equipotential cage conductors of the RFX-mod2, leading to localized magnetic field perturbations at the inner radius of the machine.

The global electromagnetic response of the passive structures suggests that RFX-mod2 is likely to exhibit faster horizontal shift during fast termination compared to the previous configuration. These findings provide critical insights into the behavior of high-current plasma discharges and the influence of passive structures on macroscopic plasma stability.