Transient Electromagnetic Wave Propagation in a Plasma Waveguide

摘要

An analytic model to describe the transient propagation of an electromagnetic wave inside a hollow constant conductivity plasma annular tube is formulated. The model neglects external radiative emission since the plasma tube wall is assumed to be several skin depths in thickness. Approximate analytic time-dependent solutions for mode propagation are obtained by a combination of integral transform techniques and the method of eigenfunction expansion with homogeneous boundary conditions. The model provides insight into wave attenuation, the dispersion relations, waveguide excitation and mode coupling due to finite wall plasma conductivity. The model is developed by first considering the transient propagation characteristics of ideal cylindrical waveguides with perfectly conducting walls. This preliminary analysis provides a consistent notation for the closed plasma waveguide and suggests possible launching modes with minimal loss. The initial condition imposed on the annular plasma waveguide is fixed by exciting a specified mode in the ideal cylindrical waveguide which is then transferred into the plasma tube.