Experiments with ECRH performed during 1998-2000 are presented. An operating regime with an edgetransport barrier, interpreted as the H mode, has been studied with both on-axis and off-axis ECRH.Experimental data imply formation of an internal transport barrier simultaneously with the external transportbarrier in the case of off-axis ECRH. Strong evolution of plasma potential in the regions of the external andinternal transport barriers has been observed using heavy ion beam probe diagnostics. The mode of improvedconfinement with peaked density profiles and increased ion temperature has been observed after pellet injectioninto ECRH plasmas. Instabilities, identified as neoclassical tearing modes, have been found to limit β in the regimes with ahigh fraction of bootstrap current. The dependence of the critical β on the q(r) profile has been observed. Asystematic study of plasma turbulence has been started using correlation reflectometry diagnostics.
Transport studies with the ECH system on FTU tokamak