Propagation of Electromagnetic Waves along an Annular Plasma

The characteristics of propagation for the lowest-order mode in a coaxial line partially filled with an annular plasma tube have been investigated theoretically. The system supports two slow waves, and a fast wave which is a perturbed form of the T.E.M. wave which would propagate if the coaxial line contained a single homogeneous dielectric. The fast wave cuts off at the plasma frequency. The effect of non-uniformity of the plasma annulus on the ω - β diagram has been derived using approximate techniques. The experimental work has been confined to the study of fast waves in the coaxial line and slow waves in the same structure but with the inner conductor removed.