Modeling of atmospheric pressure Helium/Oxygen mixture discharges in extremely narrow gap

Recently, applications for atmospheric pressure discharges have been developed on various fields, such as biomedical treatment and material surface modification. In such fields, radicals are very important species for treatment and modification. But the lifetime of radicals is very short, so they should be generated close to specific area. To achieve this, atmospheric pressure plasma jets, atmospheric pressure dielectric barrier discharges are capable. Among these plasmas, pulsed atmospheric pressure discharge plasmas with extremely narrow gap have been focused on for its characteristics of high plasma density generation and less loss of radicals. To investigate this plasma, electrons properties are simulated using Monte Carlo method with narrow gap configuration electric fields in Helium. As a result, electron properties have been shown nonequilibrium in Helium. This means fluid model would not be suitable for this model. And in most of the conditions, electrons have run away with less ionizations. So, in the present paper, the electrons have been accelerated using fine cylinder and mesh electrodes with 10 micro meter gap and applied ~800V pulsed voltage[1] in Helium and Oxygen(10%) mixture. It is found that the effect of adding Oxygen has been significant. In the case of pure Helium, electrons run away without ionizations in low electric field, but the same condition in the mixture gas case, electrons ionize Oxygen and Helium about 7 times more.