Influence of Penning effect on the plasma features in a non-equilibrium atmospheric pressure plasma jet

Abstract

Non-equilibrium atmospheric pressure plasma jet (APPJ) is a cold plasma source that promises various innovative applications. The influence of Penning effect on the formation, propagation, and other physical properties of the plasma bullets in APPJ remains a debatable topic. By using a 10 cm wide active electrode and a frequency of applied voltage down to 0.5 Hz, the Penning effect caused by preceding discharges can be excluded. It was found that the Penning effect originating in a preceding discharge helps build a conductive channel in the gas flow and provide seed electrons, thus the discharge can be maintained at a low voltage which in turn leads to a smaller propagation speed for the plasma bullet. Photographs from an intensified charge coupled device reveal that the annular structure of the plasma plume for He is irrelevant to the Penning ionization process arising from preceding discharges. By adding NH 3 into Ar to introduce Penning effect, the originally filamentous discharge of Ar can display a rather extensive plasma plume in ambient as He. These results are helpful for the understanding of the behaviors of non-equilibrium APPJs generated under distinct conditions and for the design of plasma jet features, especially the spatial distribution and propagation speed, which are essential for application. V

Plasma “bullet” with hollow structure: formation and evolution

“…The electrode structure is shown in Fig. 2 which is the same as the electrode system used in our previous work 9 . The wider HV electrode with width of 10 cm is mainly used to eliminate the influence of discharge in DBD zone.…”

“…In our previous work 9 , we tried to interpret the abovementioned disagreement by providing some convincing experimental evidences. Based on it, in this paper, we would like to give a further demonstration and analysis to understand the formation and evolution of plasma “bullet” with hollow structure.…”

“…However, an opposite opinion on the physical mechanism of the formation continuously exists. Until our previous work was opened 9 , experimental researchers usually believed that the hollow structure of plasma “bullet” is closely related to the Penning effect on the interface of He/Air. For instance, Karakas et al .…”

Non-Thermal Equilibrium Atmospheric Pressure Glow-Like Discharge Plasma Jet

“…However, further interpretations were not obtained. Moreover, considering the Penning effect, the investigation of Chang et al [18] showed that filamentous discharge for pure Ar APPJ will transform into the same discharge morphology of pure He APPJ if a little ammonia (NH 3 ) is added into pure Ar. Therefore, electrical and optical properties of He APPJ and Ar/NH 3 APPJ are investigated in the present paper to generate a glow-like APPJ, and then the basic characteristics of glow-like APPJ are summarized.…”

A computational modeling study on the helium atmospheric pressure plasma needle discharge

“…However, by turning the Penning reactions on and off in their modes, Naidis, [19,20] and Naja et al [21] have shown that the Penning ionization is not essential for the bullets propagation and their hollow shape formation. Furthermore, Chang et al [22] reported that the annular structure of the plasma plume in ambient, in the case of He, is not due to the Penning effect on the He/air interface. To date, the mechanisms of the acceleration behavior of the plasma bullets have achieved considerable progress.…”