Self-pulsing discharge in hollow cathode simulated by a fluid model

Abstract

A fluid model without an external circuit is used in simulating self-pulses in hollow cathode discharge under a He-Ar gas at 10 Torr. The average discharge current increases with anode potential, and three types of self-pulsing discharge modes are obtained: (a) regular self-pulse, (b) low amplitude self-pulse, and (c) damped oscillating pulses modes. The temporal and spatial distributions of plasma parameters in the self-pulsing discharge mode are studied. Results show that the electron density, electric potential, electric field, total net electron production rates integrated over the entire discharge cell and net positive charge density change periodically in a self-pulsing period. Self-pulsing frequency ranges from tens of kHz to more than 100 kHz, and increases linearly with the average discharge current approximately. In the present average discharge current range, the peak value and current amplitude of pulsing current increases and then decreases with the increasing average current, whereas the minimum pulsing current consistently increases. The change trend of extreme self-pulsing discharge current is consistent with the change trends of total net electron production rate and net positive charge density in the discharge space. Finally, the mechanism of self-pulse in a hollow cathode discharge is proposed. Simulated results show that the phases of different plasma parameters are different in different discharge regions in a self-pulsing period. Non-equilibrium fluctuation of plasma parameters in different discharge regions is one of important factors in the formation of self-pulse. Self-pulse does not depend on an external circuit and originates from the internal microcosmic mechanism of discharge: the enhancement and weakening of the positive charge layer.