Abstract
The problem of drift stabilization of the internal resistive-wall modes (RWMs) in tokamaks is theoretically investigated. The basic assumption of the model is that, when the drift effects are neglected, these modes are unstable in the absence of a conducting wall and stable in the presence of a close-fitting perfectly conducting wall. In the former case, the instability condition is expressed as Δ′∞>0, where Δ′∞ is the matching parameter calculated under the assumption that the wall is removed to infinity. In the latter case, one has Δ ′W <0, where Δ ′W is the external matching parameter of tearing modes calculated assuming a perfectly conducting wall at the plasma boundary. In the case with a resistive wall, the relevant parameter can be either Δ′∞ or Δ ′W , depending on whether the value of the dimensionless parameter ωτs/2m is small or large, respectively (here ω is the mode frequency, τs is the resistive time constant of the wall, and m is the poloidal mode number). In the presence of drift effects, the mode frequency ω is approximately equal to the electron drift frequency, ω≈ω*e . The value of the parameter ω*e τs/2m, which therefore determines the behavior of internal RWMs, is estimated for several existing tokamaks, namely, AUG (ASDEX-Upgrade), DIII-D, JET, TFTR, and JT-60U, as well as for the projected ITER-FEAT. It is shown that, although drift effects do not stabilize internal RWMs in current devices, they should be efficient in suppressing these modes in reactor-grade tokamaks.
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Translated from Fizika Plazmy, Vol. 29, No. 9, 2003, pp. 841–846.
Original Russian Text Copyright © 2003 by Konovalov, Mikhailovskii, Tsypin, Galvão, Nascimento.
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Konovalov, S.V., Mikhailovskii, A.B., Tsypin, V.S. et al. Drift stabilization of internal resistive-wall modes in tokamaks. Plasma Phys. Rep. 29, 779–784 (2003). https://doi.org/10.1134/1.1609581
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DOI: https://doi.org/10.1134/1.1609581