H mode in the TUMAN‐3 tokamak triggered by edge plasma perturbations

• Published in: Physics of fluids. B, Plasma physics Plasma physics, 1993-07, Vol.5 (7), p.2420-2427
• Main Authors: Askinazi, L. G., Golant, V. E., Lebedev, S. V., Levin, L. S., Rozhansky, V. A., Tendler, M.
• Format: Article
• Language: English
• Subjects: 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; 700330 > Plasma Kinetics, Transport, & Impurities-- (1992-); ALKALI METAL COMPOUNDS; CLOSED PLASMA DEVICES; CONFINEMENT; DEUTERIDES; DEUTERIUM COMPOUNDS; ELECTRIC FIELDS; HYDRIDES; HYDROGEN COMPOUNDS; LITHIUM COMPOUNDS; LITHIUM DEUTERIDES; LITHIUM HYDRIDES; PELLET INJECTION; PLASMA CONFINEMENT; PLASMA DENSITY; POLARIZATION; THERMONUCLEAR DEVICES 700310 > Plasma Confinement-- (1992-); TOKAMAK DEVICES; TRANSPORT
• ISSN: 0899-8221; 2163-503X
• DOI: 10.1063/1.860726

Several types of edge plasma perturbations in the TUMAN‐3 tokamak [Proceedings of the 13th International Atomic Energy Agency Conference on Plasma Physics and Controlled Nuclear Fusion Research, 1990 (International Atomic Energy Agency, Vienna, 1991), Vol. 1, p. 509] have been demonstrated to trigger the Ohmic H‐mode transition. It is shown that three different methods, (1) radial electric field of either sign imposed by an electrode biased up to 500 V, (2) perturbation of the edge plasma density by strong gas puffing, and (3) LiD pellet injection, bring about the Ohmic H mode. In biasing experiments, the degree of improvement of particle and energy confinement depends on the polarity of the electric field and is higher for negative biasing. The evaporation of a LiD pellet (V∼150 m/sec, size ∼0.3 mm, density perturbation∼50%) in the peripheral region of the plasma column can also lead to the H‐mode transition. Experimental results are shown to be in reasonable agreement with the theory of radial electric fields in tokamaks.