New insights on the propagation of pulsed atmospheric plasma streams: From single jet to multi jet arrays

Abstract

Atmospheric pressure plasma propagation inside long dielectric tubes is analyzed for the first time through nonintrusive and nonperturbative time resolved bi-directional electric field (EF) measurements. This study unveils that plasma propagation occurs in a region where longitudinal EF exists ahead the ionization front position usually revealed from plasma emission with ICCD measurement. The ionization front propagation induces the sudden rise of a radial EF component. Both of these EF components have an amplitude of several kV/cm for helium or neon plasmas and are preserved almost constant along a few tens of cm inside a capillary. All these experimental measurements are in excellent agreement with previous model calculations. The key roles of the voltage pulse polarity and of the target nature on the helium flow patterns when plasma jet is emerging in ambient air are documented from Schlieren visualization. The second part of this work is then dedicated to the development of multi jet systems, using two different setups, based on a single plasma source. Plasma splitting in dielectric tubes drilled with sub millimetric orifices, but also plasma transfer across metallic tubes equipped with such orifices are reported and analyzed from ICCD imaging and time resolved EF measurements. This allows for the design and the feasibility validation of plasma jet arrays but also emphasizes the necessity to account for voltage pulse polarity, target potential status, consecutive helium flow modulation, and electrostatic influence between the produced secondary jets. V

Time Behaviour of Helium Atmospheric Pressure Plasma Jet Electrical and Optical Parameters

“…These values are in agreement with previous computational results [33] which shows that around 70% of the total energy is dissipated by plasma electrons, while most of the remaining energy could be dissipated by plasma ions. Electric field measurements using spectroscopic measurements returns values of around 20 kV/cm along the along the outside plasma jet [34], consistent with the time resolved measurements using Pockels effect based probes [35].…”

The 2017 Plasma Roadmap: Low temperature plasma science and technology

“…The magnitude of typical electric fields experienced at tissue surfaces was shown to be comparable with field strengths that are known to be biologically important [90]. One of these possible effects is the observation that plasma jets applied to mouse skin induces a significant increase in local blood flow and blood O 2 content [91].…”

Jet‐to‐jet interactions in atmospheric‐pressure plasma jet arrays for surface processing

“…[15][16][17] In a single plasma jet, the effects of fluid field, electrical field, and device structure on the electrical characteristics, propagation dynamics, and plume length have been widely investigated with optical and electrical diagnosis, ICCD imaging, and Schlieren photography. [18][19][20][21][22][23] It has been found that the plasma plume propagates in different modes, [10,24] there are strongly nonlinear coupling effects of ionization waves determining streamer propagation, [25] the gas heating is the dominant factor for the transition of laminar to turbulent of plasma jet and the plume length, [3,26] and the linear-field and cross-field structures APPJs have also been compared and studied. [27] For jet arrays, there are strong jet-to-jet coupling interactions causing by gas flowing and electrical field from adjacent plasma plumes, which leads to plume divergence, [10,28] different discharge modes, [14,29] and thus affects the downstream plume uniformity and treatment effects.…”

“…[27] For jet arrays, there are strong jet-to-jet coupling interactions causing by gas flowing and electrical field from adjacent plasma plumes, which leads to plume divergence, [10,28] different discharge modes, [14,29] and thus affects the downstream plume uniformity and treatment effects. [18,30] To obtain economic, uniform, and large scale APPJ arrays for diverse applications, it is important to understand the mechanisms of the plasma jets interaction and jets propagation of the jet array in the surrounding air. However, most of the reported works on plasma arrays were about the realization of the uniform and large scale plasma area, and only a few of them conducted the experimental measurements and theoretical studies of the plasma jets interactions.…”