Eo,(R) = __4~ ~

Abstract

Linear plasma fluid theory is used to study the stability of a coldelectron beam in Brillouin equilibrium which passes through a stationarycold ion background, with particular interest in stability for parametersrelevant to EBIS devices. Dispersion is studied both analyticallyand numerically. For l = 0, the usual infinite medium two streaminstability condition is shown to correspond to a requirement thatbeam perveance exceed a minimum value, P > 33 [mu]perv; hence, thismode is stable for EBIS (P [approximate] 1 [mu]perv). The Brillouinequilibrium rotation is shown to cause an electron-ion rotating streaminstability, which is convectively unstable. The l = 1 mode is alsofound to be unstable. Higher modes numbers, l > 1, are unstable,but have reduced growth. Instability is only weakly affected by finitebeam radius and boundary conditions.