Numerical simulation of plasma double layers

The results of a numerical simulation of a plasma double layer are presented. The model is of a finite, one-dimensional plasma with a specified potential difference across the system. Initially a single pulse is formed which traverses the system with constant velocity. This stage is followed by the formation of a potential drop across a limited region of the plasma. The relation between the spatial extent of the double layer and the potential drop is given approximately by L = 6( e dgr;φ/ kT e )½. The double layer causes electron and ion beams which tend to lead to instabilities in the upstream and downstream regions.