Optimization of HF- injection at the 2nd harmonic of ECRH on T-10 tokamak in order to obtain high energy content in plasma

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.