Abstract
The formation of a peaked bell-shaped profile of the electron density n e (r) in the T-11M tokamak (B t=1 T, R/a = 0.7/0.2 m, I p = 100 kA, t shot ≤ 300 ms, Li and C limiters) was observed in Li experiments carried out in the near-plateau collisionality regime (the collisionality parameter at one-half of the minor radius was v* ≥ 0.5) under the conditions of low hydrogen recycling and intense hydrogen influx from the plasma edge. It is well known that peaked n e (r) profiles are observed in collisionless regimes at v* values as low as 10−1–10−2 or in impurity-contaminated discharges, in which this effect can be attributed to the impurity accumulation on the plasma column axis. Moreover, a bell-shaped n e (r) profile in discharges with low n e can result from the ionization of hydrogen atoms at the column axis, where they arrive from the plasma edge due to cascade charge-exchange. In quasi-steady lithium discharges in T-11M, however, peaked n e (r) profiles were observed at a relatively high central electron density n e (0) and relatively high collision frequency, such that the influence of impurities on the n e (r) profile could be ignored (Z eff = 1.1±0.1). To explain this effect, one has to assume that the pinching of hydrogen ions in T-11M is anomalous. The lower estimate of the observed pinch velocity is 4 ± 1 m/s, which is three to five times higher than the velocity of the neoclassical (Ware) pinch, characteristic of these conditions. The work is devoted to the experimental study of this effect.
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Original Russian Text © V.G. Petrov, A.A. Petrov, É.A. Azizov, A.G. Alekseev, V.B. Lazarev, V.G. Merezhkin, S.V. Mirnov, 2007, published in Fizika Plazmy, 2007, Vol. 33, No. 9, pp. 771–781.
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Petrov, V.G., Petrov, A.A., Azizov, É.A. et al. Anomalous pinch in the T-11M tokamak in an enhanced-collisionality regime. Plasma Phys. Rep. 33, 703–713 (2007). https://doi.org/10.1134/S1063780X07090012
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DOI: https://doi.org/10.1134/S1063780X07090012