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 heat ing and current drive in the T-10 tokamak is studied. In regimes with off-a xis co-ECCD and q(L) < 4 at the limiter, a spontaneous transition to improv ed confinement accompanied by the formation of two electron transport barri ers is observed. The improvement resembles an L-H transition. It manifests itself as density growth, a decrease in the D-alpha emission intensity, and an increase in the central electron and ion temperatures. Two deep wells o n the potential profile (the first one at r/a(L) approximate to 0.6, where a(L) is the limiter radius, and the second one near the edge) arise during the transition. The internal barrier is formed when dq/dr similar to 0 with q approximate to 1 in the barrier region. (C) 2001 MAIK "Nauka/Interperiod ica".