Influence of Collisions on the Ion-Acoustic Instability in a Weakly Ionized Plasma

Abstract

The influence of collisions on the onset and linear stage of the ion-acoustic instability in a dc-discharge in Helium is studied experimentally. The threshold values of the drift velocity and frequency and the range of the unstable frequency spectrum are in good agreement with the values calculated from the dispersion relation based on the Vlasov equation with inclusion of ionneutral collision. The intensity of charged particle density fluctuation has been measured over 4 orders of magnitude covering the range from thermal level to the fully developed instability.