LOW-FREQUENCY CURRENT OSCILLATIONS IN A LINEAR HOT-CATHODE DISCHARGE

Low-frequency (omega much less than omega(pi)) plasma oscillations in the transition regime between the high and the low current mode of a t hermionic hot-cathode discharge are investigated experimentally. This type of current oscillation often shows chaotic dynamics. The current oscillations are related to nonlinear short wavelength potential struc tures which are identified as ion bunches formed by a fluctuating ioni zation front. These ion bunches are separated by ion holes and move at ion thermal speed rather than ion acoustic speed. By entering the neg ative space charge region of the cathode sheath, the ion bunches trigg er electron current fluctuations that provide the required feedback me chanism for the observed wave train formation.