Investigation of Electron Temperature Profile Details during Plasma Column Displacement and ECRH Power up to 1.5 MW in the T-10 Tokamak

Abstract

The question of the existence of internal transport barriers (ITBs) around low-rational number values of the stability factor q = 1, 2, … in the usual L-mode of tokamaks with central additional heating and positive magnetic shear remains open. To clarify the existence of such ITBs, experiments were carried out with a programmed linear time shift of the plasma column, in which the positions of the electron temperature measurements T_e of the emission at the second electron cyclotron harmonic are shifted relative to the plasma column, which allows one to study the T_e profile details. A series of experiments with perpendicular input of EC radiation with a power of 0.4 and 0.85 MW at a central ECRH and a fast (60 ms) shift of the column by 0.13a (minor plasma radius a) were carried out on the T-10 tokamak in plasma with a carbon limiter. In both cases, outside the q = 1 surface narrow (about 0.03a wide) and weak (a decrease in the coefficient of electron thermal conductivity χ_e by approximately two times) ITBs detected, which disappeared when the discharge parameters changed. These ITBs are 2–3 times narrower and an order of magnitude weaker than the ITBs near the surface q = 1, which was previously proposed to explain the RTP tokamak results. ITBs were not detected in the L-mode in experiments with simultaneous generation of a co-current and counter-current in the plasma center by two gyrotrons with a total power of 1.5 MW in a plasma with a tungsten limiter (column shift by 0.1a in 30 ms). This article appears to be the first journal publication on the study of T_e profile details with rapid movement of the plasma column.