Kinetic Theory of Alfven Wave Heating in Tokamak.
The Alfven wave heating in tokamaks is investigated by means of a linearized kinetic model which includes electron inertia, electron Landau damping and collisional damping, finite ion gyroradius, finite (omega)/(omega)(,ci), the equilibrium current and magnetic shear. The Alfven waves are excited by an ideal sheet current which is located between the plasma edge and a perfectly conducting wall. In the cylindrical approximation, with realistic profiles of density, temperature and equilibrium current, a system of two coupled second order differential equations for perturbed fields E(,r) and E(,(PERP)) is derived and solved numerically. The wave structures, energy deposition and density fluctuations as functions of r and the total impedance are computed. Mode conversion to the kinetic Alfven wave and its damping are observed. The two tokamaks PRETEXT and PLT are used to illustrate these results. The plasma is heated through electron Landau damping and collisional damping of "high Q" resonant absorption (corresponding to discrete stable kink modes and normal modes of the kinetic shear wave in the cold plasma). The plasma impedance is sensitive to the profiles and mode number chosen. The effects of collisional damping, finite (omega)/(omega)(,ci) and equilibrium current are discussed. A comparison with previous results based on magnetohydrodynamics is given. With two exceptions, our result is consistent with theirs.
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- Physics: Fluid and Plasma; Energy