Latest results on quiescent and post-disruption runaway electron mitigation experiments at Frascati Tokamak Upgrade

Analysis of experimental data collected in the last FTU campaigns provide interesting results on the deuterium large (wrt FTU volume) pellet capability of REs suppression, mainly due to the induced burst MHD activity expelling REs seed, on discharges with 0.5 MA and 5.3T. Clear signs of avalanche multiplication of REs after single pellet injection on 0.36 MA flat-top discharges is shown as well as quantitative indications of dissipative effects in terms of critical electrical field increase due to fan-like instabilities. Analysis of large fan-like instabilities on post-disruption RE beams, that seem to be correlated with current inversion in the central solenoid current as well as with background density drops, revealed the strong capability they have to suppress RE energy indicating a new possible strategy for RE energy suppression controlling large fan instabilities. We show how such useful density drops can be induced using modulated ECRH power.