Absorption of high-frequency guided waves in a plasma-loaded waveguide

Abstract

A kinetic theory model for the absorption of high-frequency guided plasma waves is presented for a warm, inhomogeneous, magnetized plasma column loaded inside a waveguide. Electron cyclotron resonance (ECR) absorption and Landau damping terms, derived as the anti-Hermitian part of the susceptibility tensor, are included in the model for a loss-free plasma-loaded waveguide developed earlier [A. Ganguli et al., Phys. Plasmas 5, 1178, (1998)]. In this formulation, the imaginary part of the complex propagation constant (in the presence of absorption) is obtained using a perturbation technique treating the anti-Hermitian part of the dielectric tensor as small in comparison to the Hermitian part, for the loss-free plasma. In this paper, we present the formulation for the inclusion of ECR absorption and Landau damping along with numerical results describing the role of a small population of warm electrons in wave damping in such a discharge. Numerical results are presented in the form of dispersion curves (plots of Vphase versus ω∕Ωe) and damping curves (plots of ∣Imkz∕kv∣ versus ω∕Ωe). It is seen that although the warm electrons have a marginal effect on wave dispersion, their presence produces a marked increase in the damping rates away from the ECR region. It is also shown that damping occurs primarily through Doppler-shifted ECR resonance and not Landau damping, even well away from ECR. Power absorption calculations are also presented for two magnetic field profiles.