The effect of HF electrical field on beam-plasma interaction in a plasma waveguide

Abstract

In this paper we investigate the stabilizing effect of a strong HF (pump) electrical field on a two-stream (Buneman) instability in a plane and cylindrical plasma waveguide. Starting from the two-fluid plasma model we separate the problem into two parts. The "temporal" (dynamical) part enables us to find the frequencies and growth rates of unstable waves. This part within the redefinition of natural (eigen) frequencies coincides with the system describing HF suppression of the Buneman instability in a uniform unbounded plasma. Natural frequencies of oscillations and spatial distribution of the amplitude of the self-consistent electrical field are obtained by solving a boundary-value problem ("spatial" part) considering a specific spatial distribution of plasma density. It is shown that, independent of the geometry of the problem, the conclusion that HF stabilization of Buneman instability in plasma waveguides remains valid. The influence of the HF electric field on the instability of a low-density electron beam passing through a plasma waveguide is reported. It is found that the HF field has no essential effect on the frequencies and growth rates of unstable surface waves which are excited by the beam in the plasma waveguides. The region of instability only slightly narrows and the growth rate decreases by a small factor.