The Radial And Poloidal Localization Of Fast Magnetoacoustic Eigenmodes In Tokamaks
PHYSICS OF PLASMAS(2000)
摘要
Edge-localized fast magnetoacoustic eigenmodes (FME) may be responsible for the observed superthermal ion cyclotron emission in recent deuterium/deuterium (DD) and deuterium/tritium (DT) experiments. These modes can be driven unstable by resonant interaction with a small population of energetic ions (e.g., fusion alphas), having an anisotropic distribution in velocity space, provided that the mode frequency is close to the ion cyclotron frequency. In the present paper, the radial and poloidal structure of these eigenmodes is analyzed, by solving the two-dimensional (2D) eigenmode equation both numerically and analytically using a variational approach. In particular, the conditions for the mode localization and the dependence of the mode structure on aspect ratio and ellipticity are investigated. The eigenmode is found to be radially localized near the plasma edge. In a tokamak with finite aspect ratio, the mode is localized also poloidally near the outer midplane edge. The existence of localized solutions for both sign of the poloidal mode number is found to be sensitive to the ellipticity, the magnitude of parallel wave number and the plasma density profile. (C) 2000 American Institute of Physics. [S1070-664X(00)03205-5].
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关键词
aspect ratio,magnetohydrodynamics,kinetics,electromagnetic waves
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