Transport and MHD studies at high Te in FTU tokamak

Magnetohydrodynamic (MHD) activity and energy transport at rational-q surfaces is analysed on the basis of experimental results on current density profile control obtained with localized electron cyclotron resonance heating (ECRH) on FTU tokamak. The MHD response, in particular 2/1 and 1/1 modes, to ECRH is in agreement with expectations from a theoretical model including resistive wall braking and toroidal mode coupling. It is also shown that the magnetic shear at rq = 1 could control m = 1 mode saturation and magnetic reconnection. Heating results with ECRH at steady state indicate that transport enhancement is the dominant effect on confinement at the q = 2 surface, and suggest that conduction and convection inside the asymmetric m = 1 island should both be taken into account for a proper description of the thermal response to localized ECRH.