Overview of the FTU Results

Experiments on runaway electrons have been performed for the determination of the critical electric field for runaways generation. A large database of post-disruption generated runaway beams has been analysed in order to identify linear dynamical models for new position and current runaway beam controllers, and experiments of Electron Cyclotron assisted plasma start-up have shown the presence of runaway electrons also below the expected electric field threshold, indicating that the radio-frequency power acts as seeding for fast electrons. A linear micro-stability analysis of Neon doped pulses has been carried out to investigate the mechanisms leading to the observed density peaking. A study of the ion drift effects on the MARFE instability has been performed and the peaking of density profile in the high density regime has been well reproduced using a thermo-diffusive pinch in the particle transport equation. The analysis of the linear stability of the 2/1 tearing mode observed in high density plasmas has highlighted a destabilization with increasing peaking of the current profile during the density ramp-up, while the final phase of the mode temporal evolution is characterized by limit cycles on the amplitude/frequency plane. A Liquid Lithium Limiter with thermal load capability up to 10 MW/m2 has been tested. The pulse duration has been extended up to 4.5 s and elongated configurations have been obtained for 3.5 s, with the X-point just outside the plasma chamber. W/Fe samples have been exposed in the SOL in order to study the sputtering of Fe and the W enrichment of the surface layer. Dusts have been collected and analyzed, showing that the metallic population exhibits a high fraction of magnetic grains. A new diagnostic for in-flight RE studies has allowed to provide simultaneously the image and the visible/infrared spectrum of the forward and backward radiation. A fast infrared camera for thermo-graphic analysis has provided the pattern of the toroidal limiter heating by disruption heat loads, and a triple-GEM detector has been mounted on one equatorial port and tested for soft-X rays diagnostic. The Collective Thomson Scattering diagnostic has been upgraded and used for investigations on Parametric Decay Instability excitation by Electron Cyclotron beams correlated with magnetic islands, and new capabilities of the Cherenkov probe have been explored in the presence of Beta-induced Alfvén Eigenmodes associated to high-amplitude magnetic islands.