Double layer formation

Results from several numerical simulations of the formation of double layers in plasmas with a constant potential drop across them are presented. The emphasis is mainly on plasma processes during the formation of double layers. With the initial condition of a uniform electric field in a uniform plasma, double layer formation involved the formation of a deep plasma-density cavity with a surplus positive space charge. In simulation runs with electron current injection in excess of the electron thermal current, from the low potential side, this ion-rich cavity transformed into a double layer and subsequently propagated toward the high potential side with a speed nearly equal to the ion-acoustic speed. During the formation phase the ion current from the high potential side was completely disrupted. It recuperated after the formation of double layers. The electron current from the low potential side was partially disrupted with the formation of an almost fully developed double layer.