Sheath structure due to cold negatively charged particles in low pressure plasma

Abstract

The aim of the brief report is to discuss the effect of collisions on the sheath structure in presence of cold multi species ions. Using fluid model it is shown analytically that at the sheath edge the drift velocity of the plasma can be smaller than the dust acoustic speed in a low pressure collisional plasma. Under these condition Bohm criterion is sufficient condition for the existence of a positive boundary sheath, but it is not a necessary condition.