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In this paper, we report results from the computational study of the intersection of the atmospheric pressure plasma jet with a dielectric surface having high conductivity and high dielectric constant. In this case, multiple reflections of the ionization wave (IW) between the jet tube and the surface are observed. We consider the mixture of helium with a small percentage of oxygen (He/O2 = 99.8/0.2), which flows through the jet tube into the ambient humid room air (N2/O2/H2O = 79.5/20/0.5). We evaluate the production and delivery of main ions and reactive oxygen and nitrogen species, which are important for applications in biomedicine. The fluxes and fluences of these species to the dielectric surface are recorded during a single plasma jet pulse of negative polarity. We show that the electron density behind the IW front increases with each passage of the IW between the tube and the surface. With the forward, reflected, and secondary forward IW, there is an essential increase of ions and radicals behind the IW front. The highest increase of radicals and their fluxes is observed after the secondary forward wave bridges the gap and touches the surface. [ABSTRACT FROM AUTHOR]

In this paper, a review of general and specific properties of ionization waves—streamers is presented. Characteristics of streamers in gases and liquids, sprites in the Earth's atmosphere and guided streamers in cold atmospheric-pressure plasma jets are discussed. Information on streamer structure, propagation velocity and radius, parameters of the streamer plasma (electron density in the streamer channel, peak electric field in the streamer head) in various media, obtained using diagnostic methods, numerical modeling and analytical approach, is analyzed. [ABSTRACT FROM AUTHOR]

The information on typical values of ion energy and angular distributions (IEADs) on surfaces delivered by plasma jets is equally important for the plasma processing and plasma medicine. In this paper, we report on results from a 2D computational investigation of the IEADs when plasma jet interacts with a weakly conductive dielectric surface. The IEADs are computed using Monte Carlo techniques. The ion fluxes to surfaces are recorded simultaneously with IEADs. The results of this investigation suggest that ion energies on surfaces delivered by plasma jets can be rather high. In particular, we demonstrate that an ionization wave (IW) in plasma jets of positive cycle or pulse can produce ions with energies of a few eV. In case of negative IW the ions are almost thermalized. [ABSTRACT FROM AUTHOR]

In this paper, we discuss the results from the computational investigation of the effect of a metal grounded target, metal target at a floating potential and dielectric targets (conductive and non-conductive) on the plasma bullet propagation and reflection. We show that the intensity of the primary ionization wave (IW) is the highest for the metal target, while it is significantly lower for the non-conductive dielectric. For the conductive dielectric, the wave intensity is greater than that for the non-conductive dielectrics, but lower than for a metal target. After the primarily forward IW touches the target, the reflected waves are observed for all the targets under investigation. For a metal target the reflected IW changes its direction and transforms into the secondary forward wave. We did not observe secondary forward IWs for dielectric targets. For dielectric targets, the reflected waves gradually decayed without changing their direction. The 'stopping' path for the reflected wave is introduced and the increase/decrease of this path is discussed in dependence on the target properties. [ABSTRACT FROM AUTHOR]