Absorption of a plasma of finite density around the electron cyclotron harmonics

Abstract

An analytical and numerical study of the absorption of a thermal plasma of finite density around the electron harmonics is presented. The absorption coefficient is evaluated by means of the energy conservation law and the finite-density effects in the wave absorption are analyzed in terms of both the dispersion and polarization of the wave. For a wide range of angles around perpendicular propagation the absorption, around the second harmonic, of the fast extraordinary mode is found to increase with respect to the value obtained when the limiting expression for vanishing plasma density is adopted, polarization effects being larger than dispersion effects. Furthermore, the absorption (emission) line width and the optical thickness of a Tokamak plasma are given.