Instabilities Due to Interaction between a Slow Electron Beam and a Plasma

A mercury plasma is perturbed experimentally by a slow electron beam whose velocity is of the order of a thermal velocity of medium electrons. A special but a simple gun is used to drive the slow electron beam into a plasma region. The beam is therefore considered to be of the drifted Maxwellian distribution. Instabilities are classified into the two types; one of them is a wave of beam-electron coupling and the other is a wave of beam-ion coupling. Unstable regions are shown as a function of the frequency and the electron beam velocity, and explained on the basis of the theory of drift instability in three-component plasma system.