Effect of airflow on the dielectric barrier discharge in ambient air at atmosphericpressure is presented.The influence of airflow on the spatial distribution and intensity of adischarge were investigated experimentally.A critical frequency of 1 kHz was found.With thefrequency above 1 kHz,when a fast airflow was introduced into the discharge gap,the dischargepatterns varied from filaments to curved stripes and the curvature degree rose with an increasein the airflow speed.At the same time,the discharge intensity decreased.However with thedischarge frequency below 1 kHz,the discharge intensity would get greater with an increase in theairflow speed.
Based on the one-dimensional fluid model, the characteristics of homogeneous dischargeswith hydrogen diluted silane and argon at atmospheric pressure are numerically investigated.The primary processes of excitation and ionization and sixteen reactions of radicals withradicals in silane/hydrogen/argon discharges are considered. The effects of hydrogen dilution onthe densities of species (e, H, SiH_3^+, SiH_3^-, SiH_3,) are analyzed. The simulation results show thatthe highest densities of e, SiH_3^+, H, SiH_3^-, SiH_3 correspond to the optimal dilution concentration ofH_2. The deposition rate of μc-Si:H film depends on the SiH_3 concentration, and atomic hydrogenin the plasma is found to play an important role in the crystallization fraction of the depositedfilms. This model explains the effects of H_2 dilution on the deposition rate and crystallized fractionof μc-Si:H film growth.
This paper performs a numerical simulation of concentric-ring discharge structures within the scope of a twodimensional diffusion-drift model at atmospheric pressure between two parallel circular electrodes covered with thin dielectric layers.With a relative high frequency the discharge structures present different appearances of ring structures within different radii in time due to the evolvement of the filaments.The spontaneous electron density distributions help understanding the formation and development of self-organized discharge structures.During a cycle the electron avalanches are triggered by the electric field strengthened by the feeding voltage and the residual charged particles on the barrier surface deposited in the previous discharges.The accumulation of charges is shown to play a dominant role in the generation and annihilation of the discharge structures.Besides,the rings split and unify to bring and annihilate rings which form a new discharge structure.
An indirect method for measuring the electron density of radio frequency atmospheric pressure plasma jets(RF-APPJ) based on the discharge voltage and current waveforms is presented.An equivalent circuit of the plasma discharge is assumed by taking into account the electrode capacitance,serial resistance and inductance of the bulk plasma,as well as the sheath impedance.Based on the circuit model,the electron density can be obtained according to Ohm's law.By using this method,the effects of the electrode shape and discharge gap on the electron density are discussed.
This paper presents the interactions between two cold atmospheric plasma jets.Bychanging the experimental conditions including the gas flow rate,the applied voltage,the powersupply frequency and the inter-electrode distance d,three different interaction modes,attraction,repulsion and combination,were observed.It is shown that the interaction modes of the two jetsare principally affected by the electrodes,the gas flow rate,the plasma jets and the power supplyfrequency.
A one-dimensional fluid model for homogeneous atmospheric pressure barrier discharges in helium is presented by considerilag elementary processes of excitation and ionization including a metastable atom effect. Using this model we investigate the behaviours of the helium metastable atoms in discharges as well as their influence on the discharge characteristics. It is shown that the metastable atoms with a relatively high concentration during the discharge are mainly produced in the active phase of the discharge and dissolved in the off phase. It is also found that the metastable atom collisions can not only provide seed electrons for discharges but also influence the concentration of ions. A reduction of matestable atom density results in a drop in the charged particle densities and causes a qualitative change in the discharge patterns.
The characteristics of homogeneous discharges in mixed gases of hydrogen diluted silane and argon at atmospheric pressure are investigated numerically based on a one-dimensional fluid model.This model takes into account the primary processes excitation and ionization,sixteen reactions of radicals with radicals in silane/hydrogen/argon discharges and therefore,can adequately represent the discharge plasma.We analyze the effects of very high frequency(VHF) on the densities of species(e,H,SiH3,SiH+3 and SiH2) in such discharges using the model.The simulation results show that the densities of SiH3,SiH+3,H,and SiH2 increase with VHF when the VHF ranges from 30 MHz to 150 MHz.It is found that the deposition rate of μc-Si:H film depends on the concentration of SiH3,SiH+3,SiH2,and H in the plasma.The effects of VHF on the deposition rate and the amount of crystallized fraction for μc-Si:H film growth is also discussed in this paper.
An atmospheric pressure nonequilibrium argon/oxygen plasma jet assisted by thepreionization of syringe needle electrode discharge is reported. With the syringe needle plasmaas its pre-ionization source, the hybrid barrier-jet was shown to generate uniform discharge witha lower breakdown voltage and a relatively low gas temperature varying from 390 K to 440 K,even when the vol.% oxygen in argon was up to 6%. Utilizing the actinometry method, theconcentration of atomic oxygen was estimated to be about in an orders of magnitude of 10^(17) cm^(-3).The argon/oxygen plasma jet was then employed to clean out heat transfer oil, with a maximumcleaning rate of 0.1 mm/s achieved.
