Excitation of a surface plasma wave over a plasma cylinder by a relativistic electron beam

Abstract

A relativistic electron beam propagating in a plasma cylinder excites a surface plasma wave (SPW) via the Cerenkov interaction. The wave frequency decreases with beam velocity. The growth rate, however, initially increases with frequency ω, attains a maximum, and then falls off due to the localization of the SPW near the surface. For typical parameters, maximum growth occurs at ω∕ωP≈0.36, where ωP is the plasma frequency. With the increase in the radius of the thin plasma cylinder, the optimum growth rate increases in magnitude. The annular beam propagating outside the plasma cylinder excites the SPW with larger growth rate for the same beam current and the beam radius rb=1.02a, where a is the radius of the thin plasma cylinder.