Abstract
Transition from a Townsend mode to a normal glow mode has been reported in the literature for uniform dielectric barrier discharge (DBD) at atmospheric pressure. In this paper, through a one-dimensional fluid model, more modes of uniform DBD in helium and transitions between them are found with varying rising time of a saw-tooth voltage. The results indicate that a positive discharge initiates at the positive-slope voltage phase, whose pulse duration decreases, while the peak value increases with decreasing rising time. During this process, a negative discharge initiating at the negative-slope voltage phase keeps weakening to almost zero current. The predominant positive discharge is then investigated through analyzing spatial distributions of electron density, ion density, and electric field at the peak current moment. In combination with the voltage-current curve, discharge modes of DBD are revealed to transit from a Townsend, a normal glow, to an abnormal glow with decreasing voltage rising time. These mode transitions are qualitatively explained by analyzing the gap voltage and electron density averaged in the gap just before discharge initiation. The results also suggest that by reducing the rising time or increasing voltage amplitude, DBD is prone to operate in the abnormal glow mode. Moreover, DBD in the abnormal glow mode has an increasing peak current and a decreasing pulse duration with increasing voltage amplitude. Finally, the critical voltage amplitude is given as a function of voltage rising time for the mode transitions from the Townsend to the normal glow and the normal glow to the abnormal glow.
Highlights
Low-temperature plasma at atmospheric pressure has been extensively used in various application fields, such as thin-film deposition,1 surface modification,2,3 ozone generation,4–6 and waste water treatment.7,8As one of the most promising approaches to generating lowtemperature plasma at atmospheric pressure, dielectric barrier discharge (DBD) has attracted much attention
Based on a one-dimensional fluid model, the influence of Tr has been investigated on discharge modes of an atmospheric pressure helium DBD excited by a saw-tooth voltage
Results indicate that uniform DBD initiates only once during the positive voltage phase
Summary
Low-temperature plasma at atmospheric pressure has been extensively used in various application fields, such as thin-film deposition, surface modification, ozone generation, and waste water treatment.. Golubovskii et al have proposed that uniform DBD in helium is prone to operate in the normal glow mode with a thin barrier and a wide gap. Otherwise, it belongs to the Townsend mode.. Excited by a low-frequency Gaussian voltage, argon DBD transits from the Townsend mode to the normal glow one with increasing voltage amplitude.. With increasing rising time of a pulsed voltage, DBD transits from the normal glow mode to the Townsend one in nitrogen or helium.. Besides the usual Townsend and normal glow modes, the results reveal that DBD can operate in the abnormal glow mode with decreasing voltage rising time
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