Characteristics of radio-frequency, atmospheric-pressure glow discharges with air using bare metal electrodes

Abstract

In this letter, an induced gas discharge approach is proposed and described in detail for obtaining a uniform atmospheric-pressure glow discharge with air in a γ mode using water-cooled, bare metal electrodes driven by radio-frequency (13.56MHz) power supply. A preliminary study on the discharge characteristics of the air glow discharge is also presented in this study. With this induced gas discharge approach, radio-frequency, atmospheric-pressure glow discharges using bare metal electrodes with other gases which cannot be ignited directly as the plasma working gas, such as nitrogen, oxygen, etc., can also be obtained.

Electrical Features of Radio-frequency, Atmospheric-pressure, Bare-metallic-electrode Glow Discharges

“…In addition, as indicated in previous studies, the discharge with many thin filaments or micro-discharges can transfer to a glow discharge in APDBD plasmas provided that there are enough seed electrons to turn on the discharge under a low electric field [1,2]. Based on the preceding discussions, if we define the gas which can be ignited directly to form the RF APGD plasma as the plasma-inducing gas, e.g., helium or argon, while on the other hand, the gas which cannot be used to generate the RF APGD plasma directly at the present time, e.g., air, nitrogen, oxygen, etc., as the plasma-forming gas, in this paper, the induced gas discharge approach can be expressed as [33,34]: first, generating a glow discharge plasma operating in a a and/or c mode after breakdown with the plasma-inducing gas (e.g., helium or argon); second, transferring the discharge mode to the c mode (or a-c co-existing mode) if the plasma operates in a pure a mode after breakdown by increasing the RF power input; third, increasing the flow rate of the plasma-forming gas (e.g., air, nitrogen, oxygen, etc.) to generate the c mode discharge with the plasma-inducing-forming gas mixture; decreasing the plasma-inducing gas flow rate, and finally, a stable glow discharge plasma operating in the c mode is obtained when no plasma-inducing gas is added into the plasma-forming gas any more.…”

“…In this paper, an induced gas discharge approach [33,34] is described in detail for obtaining the RF APGD plasmas of pure nitrogen or air operating in a c mode. The discharge features of the RF APGDs of helium, argon, nitrogen, air and their mixtures are also discussed.…”

“…In Fig. 2b, there is a much brighter positive column across the gap between two electrodes, which is surrounded by a less bright discharge region [33]. Then, decreasing the flow rate of helium, a c-discharge with pure air can be achieved when no helium is added into air any more (Q Air = 1.0 slpm), as shown in Fig.…”

“…[30][31][32], RF discharges in air at atmospheric pressure using water-cooled bare copper electrodes were initiated by first touching the electrodes together, setting the current to the desired value, and then drawing the electrodes apart, the discharges operating as either RF glow or RF arc discharges, which resulted in the asymmetric voltage-current characteristics. Recently, a kind of RF APGD plasma of air operating steadily in a c mode with fixed initial gap spacings of 1.5-6.4 mm was reported using an induced gas discharge approach [33]. And the similar method was also subsequently employed to produce pure nitrogen RF APGD plasmas [34].…”

Capacitive discharge mode transition in moderate and atmospheric pressure

“…For such RF capacitive discharges, two different discharge modes of a and c and the mode transition between the two have been studied for gas pressures from 10 mTorr to several tens of Torr [5][6][7][8]. Recent investigations also reported the existence of the c-mode and the a-c mode transition at the atmospheric pressure [9][10][11]. However, not much work has been pursued in the moderate to atmospheric pressure range.…”