Relaxation of Relativistic Electron Beam in a Plasma with Random Density Inhomogeneities

Abstract

The relaxation of kinetically unstable relativistic electron beam in plasma with random density inhomogeneities is studied. Their effect is treated as angular diffusion of resonantly excited Langmuir waves in the wavenumber space. Formulas effective for obtaining the beam energy deposition rate and the Langmuir-wave fluctuation spectrum are presented. The result shows a strong reduction of the energy relaxation rate due to diffusion of Langmuir waves from linearly unstable region to the region where they are damped by the beam itself. The model attributing the formation of random density inhomogeneities to the modulational instability of the Langmuir condensate produced by the beam plasma interaction is used to estimate self-consistently the level of inhomogeneities.