Bullet Velocity Distribution of a Helium Atmospheric-Pressure Plasma Jet in Various N2/O2 Mixed Ambient Conditions

Spatial bullet velocity distribution of an atmospheric-pressure plasma jet (APPJ) in the N₂ and O₂ mixture gas were investigated by varying the gas mixing ratio. The bullet propagation from the discharge tube exit was observed by an ICCD and the bullet velocity had three phases as the acceleration, the constant velocity, and the deceleration phases. These velocity phases were analyzed using the simple and analytical fluid model. The density of neutrals and the transport parameters of electron were obtained from CFD-ACE+ and BOLSIG+. It can be envisaged that each of three propagation phases are influenced closely by the Penning ionization effect of helium metastable on N₂ and O₂ ionization, the induced electric field in an APPJ discharge tube, and the formation of negative oxygen molecules, respectively. It is expected that this paper explains the effects of grounded or floated target under the jet on bullet and vice versa.