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.

The results of electron cyclotron current drive experiments on the T-10 tokamak are presented.The total RF power was up to 2.5 MW, the electron temperature was up to 7 keV and the maximum driven current was 110 kA. The current drive efficiency qcD was approximately 0.1 A/W. The value of qcD and its dependence on the plasma parameters agree satisfactorily with the linear theory, corrected for the finite confinement time of resonant electrons. In discharges with large beta poloidal, ,9, = 3, complete replacement of the inductive current by non-inductive electron cyclotron current drive and bootstrap current was obtained.

This article has been downloaded from IOPscience. Please scroll down to see the full text article. 2011 Nucl. Fusion 51 094019

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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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Hard x-ray correlation analysis as a diagnostic tool for the measurement of magnetic turbulence in tokamaks Rev.The detailed design of the magnetic diagnostic for ITER is presented. The system consists of groups of pickup coils and flux loops on the vessel wall, the back plate, and the divertor. These sensors provide the measurements for the equilibrium reconstruction and the fluctuation analysis. The system is supplemented by Rogowski coils for halo current measurements and by a diamagnetic loop. The complete system meets the measurement requirements, matching those of contemporary large divertor tokamaks. The maximum radiation exposure is such that the sensors will survive for the lifetime of the ITER.