Influence of dissipation on beam instability of negative mass type in nouniform beam-plasma waveguide

Abstract

Summary form only given. Intense microwave sources driven by relativistic electron beam are most perspective ones. In order to increase output power one must increase beam current. In this way inner degrees of freedom of the beams reveal themselves more and more efficiently. In addition static fields of the beam space charge set upper limit on beam current that can pass through given vacuum waveguide. Plasma filled sources can pass through e-beams with current several times higher than the vacuum ones. Their operation is based on induced radiation of oscillations of plasma-filled waveguide by beam electrons. Mechanisms of overlimiting beam-plasma interaction differs from that of underlimiting and depend on transversal geometry of the waveguide. Traditional concepts related to physical nature of beam-plasma instability are not applicable to such systems. It is shown that in uniform-cross-section waveguide, instability is based on aperiodical modulation of the beam density in media with negative dielectric constant. Actually negative mass type instability develops and these systems cannot be used for generation. Presence of high level dissipation transforms the instability to that of dissipative type. Present investigation shows that analogous instability develops in non-uniform-cross-section waveguide. With increase in level of dissipation it transform to instability of dissipative type with maximal growth rate that are inverse proportional to dissipation