Formation and dynamics of plasma bullets in a non-thermal plasma jet: influence of the high-voltage parameters on the plume characteristics

Abstract

Non-thermal plasma jets in open air are composed of ionization waves commonly known as 'plasma bullets' propagating at high velocities. We present in this paper an experimental study of plasma bullets produced in a dielectric barrier discharge linear-field reactor fed with helium and driven by microsecond high-voltage pulses. Two discharges were produced between electrodes for every pulse (at the rising and falling edge), but only one bullet was generated. Fast intensified charge coupled device camera imaging showed that bullet velocity and diameter increase with applied voltage. Spatially resolved optical emission spectroscopy measurements provided evidence of the hollow structure of the jet and its contraction. It was shown that the pulse amplitude significantly enhances electron energy and production of active species. The plasma bullet appeared to behave like a surface discharge in the tube, and like a positive streamer in air. A kinetics mechanism based on electron impact, Penning effect and charge transfer reactions is proposed to explain the propagation of the ionization front and temporal behavior of the radiative species.

Electrical, Thermal and Optical Parametric Study of Guided Ionization Waves Produced with a Compact μs-Pulsed DBD-Based Reactor

“…A time lag (ΔtGIWs) is established between the zero-crossing point of the positive current impulse and the rising voltage edge. The corresponding ΔtGIWs in the case of negative impulse is negligible under our experimental conditions, which is in agreement with other published works [16,23,42]. Hereafter, the results section will refer to the peak value (IPeak) of the positive current impulse, its corresponding accumulated charge (Qmain, obtained through integration of the current impulse over time), and the time lag ΔtGIWs (see Figure 3b for definition).…”

“…These are indirectly associated with the plasma current in the inter-electrode region. The positive impulse refers to a primary discharge that is formed in the reactor, with characteristics depending strongly on the system operating parameters [16,25,43,44]. It is now well known that this primary discharge is due to the development of a guided ionization wave or guided streamer [3,4]; it is formed in the DBD region once the space charge electric field becomes comparable to the external one, and it propagates fast (velocities up to some 100 s km/s) outside the reactor, being confined in the noble gas channel.…”

“…It is now well known that this primary discharge is due to the development of a guided ionization wave or guided streamer [3,4]; it is formed in the DBD region once the space charge electric field becomes comparable to the external one, and it propagates fast (velocities up to some 100 s km/s) outside the reactor, being confined in the noble gas channel. The negative impulse refers to a secondary discharge, which in the case of linear-field GIWs, is attributed to the release of charges accumulated in the dielectric tube during the rising slope of the voltage [16,23]. A time lag (ΔtGIWs) is established between the zero-crossing point of the positive current impulse and the rising voltage edge.…”

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

“…These three distinct phases of the guided streamer head, during its travel through ambient air, may be also considered as launching (with increasing velocity), propagation (roughly constant velocity) and ending/landing (in mid air or upon a surface, with decreasing velocity) [48][49][50].…”

The density and velocity of plasma bullets propagating along one dielectric tube

“…[4][5][6][7][8][9][10] Dielectric tube may be utilized to efficiently generate and guide the plasma bullets or ionization waves when an AC voltage or pulsed voltage is applied onto the microelectrodes. 11,12 It has been widely accepted that, the plasma bullets usually appear as a cathode-directed streamer guided by the helium jet in air, and the propagation of an ionization front leads to a rapid increase in plasma density. 1,13 Helium plasma jet and Neon plasma plume under effect of atmospheric-pressure guided streamers were explained before.…”