Abstract
The self-organized discharge behaviour occurring in a non-thermal radio-frequency plasma jet in rare gases at atmospheric pressure was investigated. The frequency of the azimuthal rotation of filaments in the active plasma volume and their inclination were measured along with the gas temperature under varying discharge conditions. The gas flow and heating were described theoretically by a three-dimensional hydrodynamic model. The rotation frequencies obtained by both methods qualitatively agree. The results demonstrate that the plasma filaments forming an inclination angle α with the axial gas velocity uz are forced to a transversal movement with the velocity , which is oriented in the inclination direction. Variations of in the model reveal that the observed dynamics minimizes the energy loss due to convective heat transfer by the gas flow. The control of the self-organization regime motivates the application of the plasma jet for precise and reproducible material processing.
Highlights
The broad variety of material processing ranging from surface treatment, thin film synthesis to in-flight nanoparticle synthesis has driven the development of different plasma jet designs both nowadays and in the past
Nonthermal atmospheric pressure plasma jets have been subject to numerous scientific studies during the last decade. They instantiate a unique combination of interesting properties regarding high chemical reactivity or gas dynamics in a localized region under normal pressure conditions
The application of nonthermal atmospheric pressure plasma jets (nt-APPJ) for homogeneous surface treatment, such as activation of polymer surfaces, cleaning and thin film deposition [11] is still hampered by the presence of steep local gradients of the plasma parameters due to the chaotic nature of the filamented discharge channels
Summary
The broad variety of material processing ranging from surface treatment, thin film synthesis to in-flight nanoparticle synthesis has driven the development of different plasma jet designs both nowadays and in the past. In this context, nonthermal atmospheric pressure plasma jets (nt-APPJ) have been subject to numerous scientific studies during the last decade. The application of nt-APPJs for homogeneous surface treatment, such as activation of polymer surfaces, cleaning and thin film deposition [11] is still hampered by the presence of steep local gradients of the plasma parameters due to the chaotic (erratic) nature of the filamented discharge channels (plasma filaments) Their formation in a discharge gap is usually a random function of time and an averaging of spatial filament distribution can be only achieved considering longer time intervals. In the framework of this study, we attempt to tackle this task by a systematic investigation of the flow dynamics and neutral gas temperature in the LM by means of laser schlieren deflectometry (LSD) [26] and by a three-dimensional hydrodynamic modelling of the plasma jet which approximates the plasma action by heat profiles embedded in the gas volume
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