Experimental investigations of plasma bullets

Abstract

Recently several investigators reported on various means of generating cold plasma jets at atmospheric pressure. More interestingly, these jets turned out to be not continuous plasmas but trains of small high velocity plasma packets/bullets. However, until now little is known of the nature of these ‘bullets’. Here we present experimental insights into the physical and chemical characteristics of bullets. We show that their time of initiation, their velocity and the distance they travel are directly dependent on the value of the applied voltage. We also show that these bullets can be controlled by the application of an external electric field. Using an intensified charge coupled device camera we report on their geometrical shape, which was revealed to be ‘donut’ shaped, therefore giving an indication that solitary surface ionization waves may be responsible for the creation of these bullets. In addition, using emission spectroscopy, we follow the evolution of various species along the trajectory of the bullets, in this way correlating the bullet propagation with the evolution of their chemical activity.

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

“…This is representative of a faster establishment of the discharge in the DBD due to more efficient excitation/ionization of the gas [16,25]. It means that the propagation velocity of the guided streamers is also amplified, which was confirmed in [16,29,30,44]. Depending on the duty cycle value, ΔtGIWs decreases from ~250 ns at Vp = 6 kV to ~100 ns at Vp = 8 kV, values that are in the range of the ones published in the bibliography [16,25].…”

“…Other studies, referring to similar designs do exist as well [27][28][29][30][31]. Although, the electrodes that are used therein are in the form of very thin rings, which are entirely enclosed in the dielectric material, thus avoiding any contact with the atmospheric air for better insulation.…”

Influence of helium mole fraction distribution on the properties of cold atmospheric pressure helium plasma jets

“…Recent numerical simulations and experimental studies have made significant advances in the understanding of the cold plasma jets [10][11][12][13][14][15][16] . The detailed studies have revealed that the cold plasma jet produced by nano-second or micro-second pulsed discharges is typically composed of a series of rapidly propagation streamer discharges.…”

“…The detailed studies have revealed that the cold plasma jet produced by nano-second or micro-second pulsed discharges is typically composed of a series of rapidly propagation streamer discharges. The streamer with a luminous head propagates at very high speed in order of 10 4 -10 5 m/s over several centimeters 15,17,18 . The experimental images reveal that the luminous zone of the helium plasma jet is a ring-shaped [13], and the peak of luminance is shifted off the jet axis 19 .…”

Single channel atmospheric pressure transporting plasma and plasma stream demultiplexing: physical characterization and application toE. colibacteria inactivation

“…Although the discharges in plasma jets typically appear as continuous plasma, high-speed imaging shows that the plasma in fact comprises discrete, fast moving plasma bullets [10][11][12], or ionization waves (IWs). The plasma jet strongly resembles the cathode-directed streamers in some aspects, and some authors speculated that it may be initiated in a way independent of the capillary dielectric barrier discharge [13].…”