Experiment and simulation of the characteristics and mechanisms of self-oscillations in parallel-plate glow discharges

Abstract

This paper presents experimental results of the characteristics appearance and the mechanism of self-oscillation in a parallel-plate glow discharge with argon as the discharge gas at 266 Pa. The cathode and anode are molybdenum plates with a diameter of 3 cm. The distance between the electrodes is 1 cm. Discharge average voltage and current vary between 300 V and 500 μA, respectively. Light emission from the electrode gap is measured by a charge coupled device camera and argon spectra are recorded of emission lines at 650–800 nm. Results show that self-oscillations exist in the negative differential resistance region in the static V–I curve. An obvious negative differential resistance also can be observed in the dynamic of the V–I curve for the self-oscillations. The appearance and disappearance of the self-oscillating phenomenon are companied with an obvious change in all of the discharge current, discharge images, and electron excited temperature. It can be determined that the self-oscillation is a mode transition between low-current stage of Townsend discharge and high-current stage of glow discharge. The frequency range of self-oscillations starts with 0.4 k Hz up to 24 k Hz in dependence of the average discharge current and the external capacitors. When the self-oscillation disappears, the luminescence shows a significant radial contraction, the electron excitation temperature rise obviously. The frequency of oscillations exhibits a substantial linear increase with the average discharge current and decreases with the increase in the external capacitance from 0 pF up to 250 pF. A resistance–capacitance circuit model is used to simulate the self-oscillation discharge in this experimental glow discharge. Results show that the waveforms simulated by this circuit model are well consistent with those obtained experimentally at different average discharge currents and external parallel capacitances. The equivalent plasma resistance decreases with an increase in the average discharge current. The theory of charge and discharge of a capacitor provides good insights into the characteristics and mechanism of self-oscillations in parallel-plate discharges.

Numerical study of the self-pulsing of DC discharge: from corona to parallel-plate configurations

“…The discharge current can be altered either by changing the applied voltage U 0 or by the ballast resistance R. However, the external circuit does not dominate the appearance of self-pulsing, although the value of R has an influence on the pulsing characteristics. This is in agreement with the previous experimental and simulated results, e.g., in [27,29].…”

“…I TS,up . Indeed, the external circuit may have some influence on the formation of a stable subnormal mode [28,29] as well as the characteristics of self-pulsing [27,29], but it is not involved in the formation mechanism of the pulse.…”

“…Huang et al [26] found that the rising rate of the voltage has effects on the discharge current rise time and proposed a fluid model which predicted results that agreed well with experiments. He et al [27] measured the V-I characteristic of parallel-plate discharge in argon and showed that the V-I curve can be divided into three stages, i.e., Townsend discharge, self-pulsing and normal glow discharge stage. They also built an equivalent circuit model that can reproduce the pulse sequences.…”