Absorption around the electron cyclotron frequency in a thermal plasma of finite density

Cyclotron absorption around the electron cyclotron frequency in a weakly relativistic plasma of finite density in thermal equilibrium is considered for both perpendicular and quasi‐perpendicular propagation. A comprehensive analysis which includes thermal effects together with finite density corrections is given and the resulting scaling of the absorption of the extraordinary and the ordinary modes is examined. The line profiles are discussed and the optical thicknesses of a typical tokamak plasma are evaluated.