Synergy between LH and ECH Waves in the FTU Tokamak

The effects of the simultaneous injection of LH, up to 1 MW, and ECH power, up to 0.75 MW, have been studied in FTU. In the absence of the cold EC resonance in the plasma ( BT = 7.2T), the suprathermal electron tail generated by LHCD absorbs the ECH power effectively, up to 80%. In a restricted parameter range, additional electron heating due to ECH waves (up to 1.2 keV for PECH = 0.7MW) is also observed. With the cold resonance at the centre ( BT = 5.3T) and no absorption on the tail, the ECH power injection into a sawteeth and MHD free plasma, fully sustained by LHCD, causes a quasi-stationary large increase of the electron temperature in a region r/a < 0.5, with Te0 > 4keV for PECH = 0.35MW only. This strong heating exceeds the predictions of the mixed Bohm/gyro-Bohm model with magnetic shear correction, which, instead reproduces the LH phase well.