Controlling Reactive Oxygen and Nitrogen Species (RONS) Production by Atmospheric Pressure Plasma Jets Using Gas Shields

Atmospheric pressure plasma jets are a source of reactive oxygen and nitrogen species (RONS) for many applications, including plasma medicine. A current challenge is to deliver RONS to surfaces in a controllable manner. One such control strategy is using gas shields around the plasma jet to minimize the generation of less desired RONS by preventing ambient gases from interacting with the plasma jet effluent. In this paper, we report on results of a computational investigation of the production of RONS from plasma jets into ambient air consisting of helium seeded with either N$_{2}$ or O$_{2}$ surrounded by a flowing gas shield and the flux of those species to a treated surface. The model used in this study, \textit{nonPDPSIM}, solves transport equations for charged and neutral species, Poisson's equation, the electron energy equation for the electron temperature, and Navier-Stokes equations for the neutral gas flow. The shield gas has significant effects on unwanted RONS in the effluent of the plasma jet. N$_{2}$ shield gas will minimize hydroxide and other reactive oxygen species in the effluent and to the surface. Similarly, O$_{2}$ shield gas can reduce the production of nitric oxide and prevent the formation of other nitrogen compounds on the surface. Comparisons will be made to experimental measurements of optical emission from plasma jets using gas shields.