Oscillations in Synthetic Plasma Beams

Oscillations, associated with a rapid, non-collisional electron thermalization, were detected under specific conditions in a synthetic plasma beam. Experimental observations indicate that plasma oscillations only occur when the injected electron energy is greater than about twice the plasma electron thermal temperature, in reasonable agreement with two-stream instability theories. The ions were generated by contact ionization of cesium on a hot planar tungsten surface. The electrons were injected through a potential developed between the plasma and neutralizer. Oscillation frequencies were plotted as a function of the square root of the total ion current. (C.E.S.)