Excitation of high-frequency azimuthal surface waves by an annular electron beam in a waveguide with a noncircular inter
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MA ELECTRONICS
Excitation of HighFrequency Azimuthal Surface Waves by an Annular Electron Beam in a Waveguide with a Noncircular Interface of the Plasma Column1 V. O. Girka, I. O. Girka, and I. V. Pavlenko V. N. Karazin Kharkiv National University, Kharkiv, Ukraine email: [email protected], [email protected] Received June 26, 2012; in final form, November 6, 2012
Abstract—An initial stage of the interaction of an electron beam ring rotating along Larmor orbits in a gap between the plasma column and a circular metal chamber of a cylindrical waveguide with extraordinarily polarized electromagnetic waves of the surface type is studied. These waves propagate along the azimuthal angle across an axial magnetic field in the range above the upper hybrid frequency. Using numerical analysis of the dispersion relation, it is shown that by the aid of an appropriate choice of the shape of the plasma– vacuum interface one can achieve a significant increasing of growth rates of the resonant beam instability of these waves. DOI: 10.1134/S1063780X13050048 1
1. INTRODUCTION
To improve the efficiency of devices applied in microwave electronics one should solve many prob lems. The most important among them are the follow ing ones: studying the spectra of the eigen oscillations which can be excited in these devices, and transporta tion of charged particle flows which interact with these oscillations [1–3]. The usage of plasma in such devices allows one to achieve many important goals, including enhancing the limiting value of electric current, an expansion of the frequency spectrum of the excited waves, better control over the processes of excitation, etc. An interaction of charged particle flows with eigen waves of plasma is used for a long time in the plasma electronics for the generation and amplification of electromagnetic radiation [4–9]. Theory of dense electron beams, which can be used for the purposes of relativistic plasma microwave electronics, was built mainly in the papers of A.A. Rukhadze with co authors. In particular, the electromagnetic properties of the dense electron beam dealing with the problems of energy transportation in the case of their relaxation in plasma, dealing with amplification and generation of electromagnetic radiation in the plasma and vac uum microwave electronics are comprehensively and consistently considered in [10]. It presents both linear and nonlinear aspects of the beam interaction with electromagnetic waves in plasmas, waveguides, undu lators, contains a theory of plasma generators of elec tromagnetic radiation based on electron beams appli cation. Modern ideas of plasma relativistic microwave electronics, which apply pulsed highcurrent relativis 1 The article was translated by the authors.
tic beams as a source of radiation, are presented in [11]. It examines a general theory of the different mechanisms of stimulated emission of relativistic electron beams, on which the majority of various types of relativistic microwave radiation sources, generators and amplifiers, m
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