Formation of electron transport barriers under ECR control of the q(r) profile in the T-10 tokamak

The formation of transport barriers under electron cyclotron resonance heating and current drive in the T-10 tokamak is studied. In regimes with off-axis co-ECCD and qL < 4 at the limiter, a spontaneous transition to improved confinement accompanied by the formation of two electron transport barriers is observed. The improvement resembles an L-H transition. It manifests itself as density growth, a decrease in the Dα emission intensity, and an increase in the central electron and ion temperatures. Two deep wells on the potential profile (the first one at r/aL ≅ 0.6, where aL is the limiter radius, and the second one near the edge) arise during the transition. The internal barrier is formed when dq/dr ∼ 0 with q ≅ 1 in the barrier region