Energy Confinement and Sawtooth Stabilization by ECRH at High Electron Density in FTU Tokamak

The dependence of the local effective electron thermal diffusivity and of the global energy confinement on the intensity and the distribution of the heat source is explored in ECRH experiments performed on FTU tokamak. Energy transport is analysed by applying a dominant EC heating with Pecrh 0.8MW and Poh 0.2MW during ECRH, at the frequency of 140 GHz correspondent to the fundamental electron cyclotron resonance at Btor = 5T. In order to discriminate the underlying diffusive transport against internal disruptions events, ECRH is also used to stabilize sawteeth. In these conditions, the predominance of ECRH over OH allows a good estimate of heat fluxes. Ion heating in the order of Ti/Ti 30% is observed in experiments with central density up to 1020m- 3.