Transition from moving to stationary, double layers in a single-ended Q machine

Summary form only given. When the cold end-plate of a single-ended Q machine is biased positively, large amplitude (<100%) relaxation oscillations are observed in the plasma potential and plate current. These oscillations are associated with double layers that form near the hot plate and travel toward the end-plate at about the ion-acoustic velocity where they dissolve. They then form again at the hot plate, the entire process repeating in an oscillatory manner. The effect of applying a large positive bias (>30 V) to the end-plate of a Q machine when variable amounts of a neutral gas (Xe, Kr, Ar, Ne, and He) are added to the system in both potassium and cesium plasmas has been studied. As the neutral pressure is increased, the frequency of the oscillations, decreases up to some critical value of the neutral pressure where the oscillations cease. This decrease in frequency is associated with the slowing-down of the moving double layer up to the critical pressure, P_c. At P_c, a stationary, strong double layer is observed. The ions required for the formation of the stationary double layer are created by ionization of the neutral gas by the electrons which are accelerated through the double layer