Dynamic Control Of The Current Density Profile And MHD Instabilities By ECH/ECCD In Tokamaks

The paper describes experimental work performed in this field on FTU tokamak, and it deals in particular with the implementation of a system for automatic detection of TM onset, and stabilizing reaction with ECH/ECCD. The system is composed by a particular arrangement of the 140 GHz, 2 MW ECH set-up, and a DSP-based (Digital Signal Processor) unit for the analysis of ECE and Mirnov data, and for the control of gyrotron power supplies. The detection/reaction system, successfully tested in the experiments described in the paper, is very fast since no mirror motion is foreseen. This might be a possible scheme for a fast reaction to "early warning" NTM suppression in fusion devices, in which the application of ECCD, localized on the O-point radial position, is performed as soon as the seed island is detected and much before it reaches saturation. ITER perspectives are discussed.