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The plasma stability and confinement have been investigated through control of the safety factor profile q(r) by the electron cyclotron current drive in the T-10 tokamak. The regimes with dq/dr ∼ = 0 and dq/dr < 0 in the plasma core were obtained. Various types of MHD activity were observed: ordinary sawtooth, saturated sawtooth, humpbacks, hills etc. It was shown that when the minimal value q min increases from q min < 1 to q min = 2 the plasma becomes strongly unstable due to the corresponding MHD activity or passes to the steady-state improved confinement mode. The latter is realized when the electron internal transport barrier (EITB) is formed. The condition for the appearance of the EITB is dq/dr ∼ = 0, where q = m/n lies near a rational value for low m and n.

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Results of the electron cyclotron current drive experiment at the second harmonic resonance on the T-10 tokamak are presented. High frequency (HF) power up to 1.2 MW was launched from the low field side. A maximum driven current of 35 kA and current drive efficiency ηCD = 0.05 A/W at an electron temperature Tc(O) = 4 keV and a density nc(0) = 1 × 1013 cm-3 were obtained. For low HF power, the current drive efficiency was less than predicted by the linear theory unless the effect of the elliptical polarization from non-perpendicular injection is considered, in which case the efficiency is close to the theoretical value. The experimental dependence of HF on the absorbed HF power indicated a strong increase of ηCD with power. Suppression of sawtooth oscillations and improvement of confinement during electron cyclotron heating has also been demonstrated

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