Excitation and amplification of hybrid modes in circular-elliptic combined plasma waveguides including relativistic electron beam

The dispersion relation and the growth rate of the hybrid electromagnetic waves propagating in the two types of combined waveguides with complete conductor walls including isotropic cold plasma column that powered by relativistic electron beam, have been studied.The conducting wall cross section of the first waveguide is elliptical that plasma column with circular cross section is located in its core and the rest of interior regions is filled with dielectric material from the plasma boundary to the waveguide boundary. But the second waveguide has acircular cross section that elliptical plasma column is situated in its center. Electron beams as source energy are injected inside it coaxially with plasma column. By calculation of electromagnetic fields components in each of regions in the considered configurations, applying the boundary conditions, operating frequency and growth rate are obtained. The results of numerical computations are graphically presented.