Abstract
Non-traditional scheme of HF-injection has been used in T-10 tokamak for ECRH at the 2nd harmonic of ECR in X-mode. Two HF-launcher systems, with focusing beams, injected power in opposite directions under toroidal angles +/-20˚. Input power from each launcher was about the same (Phf =0.8 ÷ 0.85MWt). Absorbed energy was deposed in central area of plasma column. The new phenomenon has been found in some shots with W-limiter and Li-coating in the regime mentioned above. The spontaneous rise of the electron density nearly in the all plasma column occurs simultaneously with the rise of Te in the wide region (0<r/a<0.8) at the steady-state of ECRH. The value of the energy confinement time abruptly rises by ~15%. The absolute value of the electron heat and density fluxes reduces abruptly in the whole plasma column similarly to that of at non-local (or global) L-H transitions found earlier in JET and JT-60U. The accumulation of tungsten and light impurities is absent. In a series of shots, without L-H transitions, measurements of X-ray spectra (PHA data) showed a significant difference in comparison with the ECCD co-injection by two gyrotrons.
Highlights
The main part of experiments on the ECR plasma heating are concentrated on local energy deposition of HF – power in a rather narrow zone (ECRH – perpendicular launching) and generation of noninductive current (ECCD – oblique launching at toroidal angle ~ - 30o)
The new phenomenon has been found in some shots with W-limiter in the plasmas with two EC
The value of Dbeta falls, the positive value of dW/dt appears and the value of the energy confinement time τE abruptly rises by ~15%
Summary
The main part of experiments on the ECR plasma heating are concentrated on local energy deposition of HF – power in a rather narrow zone (ECRH – perpendicular launching) and generation of noninductive current (ECCD – oblique launching at toroidal angle ~ - 30o). In order to increase the electron energy in the ECR area, HF power was injected by two gyrotrons simultaneously in two opposite toroidal directions (co+contr injection). The spontaneous rise of the electron density nearly in the all plasma column occurs simultaneously with the rise of Te in the wide region (0
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