Time growth rate optimisation of terahertz electromagnetic wave generation by converting occupied plasma region from annular plasma to filled plasma in the core, in an elliptical Cherenkov maser with two energy sources

Abstract

In this work, a comparison between two different cases of an elliptical Cherenkov maser with two electron beams for the generation and amplification of terahertz electromagnetic waves has been presented. The waveguide is made of a hollow dielectric layer filled with a cold collisionless unmagnetised plasma. In the above-mentioned configuration, there are two electron beams with opposite velocities. The dispersion relation graph and its characteristics, such as its dependence on geometrical dimensions and characteristics of the electron beam, are presented. The growth rates of the hybrid modes are numerically calculated and their diagrams in some operating frequencies are studied. The effective factors on the time growth rate of hybrid electromagnetic waves, such as geometrical dimensions, dielectric constant of the dielectric layer, accelerating voltage, plasma frequency and applied current intensity, are analysed. It is shown that the injection of background plasma into the core region of the waveguide can enhance the output frequency and the wave growth rate of the beam–wave interaction.