25th IAEA Fusion Energy Conference - IAEA CN-221

Investigation of a Phenomenology of the Improved Confinement Regime in T-11M Tokamak

14 Oct 2014, 08:30

4h

Green 8-9 (Hotel Park Inn Pribaltiyskaya)

Poster Poster 1

Speaker

Mrs Anastasia Shcherbak (SRC RF TRINITI)

Description

Regimes of discharge of improved plasma confinement were found in the experiments with a vertical lithium limiter on T-11M tokamak, which was manifested in spontaneous growth of the electron density up to the limit Greenwald and above. Previously, such modes arising after chamber lithiization were observed in the tokamak FTU. The analysis of data obtained in T-11M has showed that this regime of improved confinement is differed from the ordinary mode (L-mode) by the sharp profile of the plasma density N_e(r), relatively high values of N_e(0) in the center and ordinary density values N_e(a) in the edge of plasma, as if there is an internal transport barrier in the center. Another visible difference of this mode from L-mode is a significant increase of soft X-rays power from the center, while maintaining or even reducing Z_eff(0). In the central region of plasma the lifetime of particles is increased by approximately twice. The energy lifetime is increased by 30-40%. Major differences of the regime of improved confinement from remarkable limiter H-mode observed in T-11M, for example, after boronization are peaking of the density profile, absence of active ELMs and collection of impurities in the plasma center. An analogy of such regimes is carried out with previously detected on the Alcator C-Mode I-mode.