ECRH: A Tool To Control Disruptions In Tokamaks

ECRH is suited for MHD control in tokamaks and this is well known since the several pioneering experiments investigating MHD stabilization either for confinement increase or for avoidance of disruptions originated by such instabilities. The first of these objectives has been strongly pursued up to the design of a system for neoclassical tearing mode stabilization in ITER based on the use of ECRH/ECCD, whereas the second one has been mostly neglected, despite the initial good results obtained on small tokamaks (RTP, T-10 and JFT-2M) in which ECRH was used to avoid disruptions originated by MHD limits or strong gas puffing. In the last years ECRH has been used again for disruption control on the Frascati Tokamak Upgrade (FTU) and on ASDEX Upgrade (AUG). Disruptions have been obtained by density limit and by impurity injection and an accurate power deposition scan has been performed. Full avoidance has been demonstrated on both tokamaks, confirming the need of a precise power localization and of the existence of a power threshold. The results of past experiments will be reviewed on the basis of the results recently obtained in FTU and AUG, together with a preliminary analysis of the applicability of this disruption control technique to ITER, by extrapolation of the power thresholds found in AUG and FTU. © 2009 American Institute of Physics