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In pulse-modulated (PM) radio frequency (RF) atmospheric pressure glow discharges (APGDs), the alpha–gamma mode transition is analyzed and confirmed with $I$ – $V$ characteristic curve. The behaviors of alpha–gamma mode transition in PM RF APGDs are more complicated than that in continuous wave (CW) RF APGDs. In terms of amplitude of applied RF voltage just before a pulse falling edge ( $V_{\mathrm {appls}}$ ), the critical $V_{\mathrm {appls}}$ at the alpha–gamma mode transition in a PM RF APGD increases with the decreasing duty ratio and is higher than that of a CW RF APGD. The feature of the alpha–gamma mode transition in a PM RF APGD is attributed to the gas temperature rise depending on both the RF voltage and duty ratio. The alpha–gamma mode transition is verified to occur at the initial phase of a PM RF APGD and the onset is earlier at a higher transient RF voltage. As the mode transition occurs, a RF voltage spike is formed in the pulse waveform.

In this paper, an atmospheric pressure polyethylene terephthalate dielectric barrier discharge is produced in a helium–argon mixture. The influences of the electrode voltage on the discharge mode are experimentally investigated. The results show that, at a fixed argon content of 50%, the discharge transits from local uniform, through the isolated pattern, to whole uniform with the increase in the electrode voltage. Both the peak value of current pulse and argon spectra (696.54, 763.13, 772.09, 811.17, and 911.81 nm) intensities are captured to clarify the characteristics of the discharge mode transition. The different discharge characteristic regions are obtained by varying the argon content. In addition, the influence of the argon content on the above-mentioned argon spectra intensities is also researched. The spectra intensities enhance at 696.54, 763.13, and 772.09 nm but weaken at 811.17 and 911.81 nm with the increase in the argon content when the discharge operates in the whole uniform mode. The physical reasons for these results are discussed.

In a pulse-modulated radio frequency atmospheric pressure dielectric barrier discharge in helium, the influence of the pulse width on the transition from a patterned glow discharge to a homogeneous glow discharge is experimentally investigated. The experimental results show that the discharge mode can transit from a patterned glow to a homogeneous glow at a moderate pulse width ( 7 μ s) but only has a patterned glow at a short pulse width ( 4 μ s) or a homogeneous glow at a long pulse width ( 18 μ s). The characteristic regions of patterned and homogeneous glow discharges are also acquired. The results can be explained using the breakdown characteristics of the pulse-modulated radio frequency atmospheric pressure discharge.

The influences of the pulse off-time on the breakdown voltage of the first pulse and the stable pulse discharge (having repeatedly undergone a process of ignition, maintenance, and extinction) are experimentally investigated in a pulse-modulated radio-frequency atmospheric pressure argon discharge. The experimental results show that the first pulse discharge breakdown voltage decreases, but the stable pulse discharge breakdown voltage increases with increasing the pulse off-time. In a large region of the pulse off-time, the luminescence property of the initial breakdown stage is studied using a high speed camera. The captured images at different pulse off-times demonstrate that the gas breakdown exhibits five key characteristics: single-point random breakdown, multi-point random breakdown, stable uniform breakdown, stable glow mixed with pattern breakdown, and stable nonuniform pattern breakdown. The physical reasons for these results are discussed.

Summary form only given. Pulse-modulated RF atmospheric pressure discharges were investigated in recent years to reduce the thermal accumulation of the discharge and extend the operation region of the stable apha glow mode. Different pulse-voltage and current waveforms were acquired in previous experiments, but no attention was paid to the interpretation. We investigated this issue by the aid of positive and negative feedback effects deducted by varying the series capacitor in the inversely L-shaped matching network employed in our pulse-modulated RF atmospheric pressure discharge. The evolution of the RF pulse is found to be influence by the igniting voltage and the feedback effect, as a result, a variety of waveforms present by igniting the discharge in the rising edge or the plateau, and the positive or negative feedback region. The spikes or the bird-heads of the pulsed waveforms appear in the negative feedback region. The pulse undershot in final stage of the spike could be substantial that the RF discharge extinguished within a time interval and subsequently re-ignited. The positive feedback region is relatively narrower, and the pulsed RF discharge originally ignited in the positive feedback region can develop into the negative feedback region.

In pulsed RF atmospheric pressure glow discharges, the gas breakdown judged by the rapid drop in the amplitude of the pulsed RF voltage is no longer universally true. The steep increment of the plasma-absorbed RF power is proposed to determine the gas breakdown. The averaged plasma-absorbed RF power over a pulse period is used to evaluate effects of the preceding pulsed RF discharge on the breakdown voltage of the following one, finding that the breakdown voltage decreases with the increment in the averaged plasma-absorbed RF power under constant pulse duty ratio. Effects of the pulse off-time on the breakdown voltage and the breakdown delay time are also studied. The obtained dependence of the breakdown voltage on the pulse off-time is indicative of the transitional plasma diffusion processes in the afterglow. The breakdown voltage varies rapidly as the plasma diffuses fast in the region of moderate pulse off-time. The contribution of nitrogen atom recombination at the alumina surface is demonstrated in the prolonged memory effect on the breakdown delay time vs. the pulse off-time and experimentally validated by introducing a trace amount of nitrogen into argon at short and long pulse off-times.