The longitudinal permittivity elements of a toroidal plasma with elliptic magnetic surfaces are evaluated by solving the drift kinetic equation as a boundary-value problem for waves in the frequency range much more than the drift frequency. The linearized drift kinetic equation is solved separately for untrapped, and three groups of trapped particles. The quadratic corrections over the inverse tokamak aspect ratio are taken into account to approximate the equilibrium magnetic field. Some physical features related to the absorption of monochromatic kinetic Alfvén waves in collisionless elongated tokamaks are analysed for the case when only usual untrapped and trapped particles-electrons can exist in the plasma volume. The radial structure of the imaginary part of the longitudinal permittivity is calculated for a toroidal plasma having the main Joint European Torus (JET) parameters. For simplicity, the parabolic profiles are considered for plasma density and temperature. It is shown, that the kinetic Alfvén wave dissipation, in cold/warm plasmas, occurs mainly by the effective interaction with untrapped electrons. There is another situation and other dissipation mechanisms for the slow Alfvén waves in plasmas with high-temperature electrons, when the bounce resonant interaction between the wave and the trapped electrons becomes substantial.
Intrinsic suppression of turbulence in linear plasma devices