TEMPORAL BEHAVIOR OF THE ELECTRON-DENSITY PROFILE DURING LIMITER BIASING IN THE HYBTOK-II TOKAMAK

A rapid change in the detailed edge electron density profile during positively biased limiter experiment is obtained with high temporal resolution of approximately 20 mus using a laser blowoff lithium beam probe technique in HYBTOK-II tokamak [IEEE Trans. Plasma Sci. PS-19, 885 (1991)]. The transient change in the electron density profile and the movement of the position where a steep density gradient is formed are experimentally observed. The temporal behavior of the electron density profile correlates well with reductions in the biasing current and H(alpha) emission in the scrape-off layer, and the suppression of electrostatic fluctuations near the edge of the core region.