Numerical investigation on the ion-neutral relaxation phenomenon of ion emission from plasma sheath at atmospheric pressure

Abstract

Collisions between ions and neutral particles are often ignored in plasma numerical simulations. However, when studying plasma jets, the collision between neutral particles and ions is significant for ion transport, so calculations cannot ignore this. Therefore, this study adopted a two-fluid model and numerically simulated the process of ion emission from the sheath edge in atmospheric pressure plasma. In this study, particle collisions are treated as Maxwellian particle collisions. We analyze the influence of several parameters, such as sheath thickness and potential drop within the sheath. We also discuss the relaxation phenomenon of relative motion between ions and neutral particles. The research results show a transition from a non-equilibrium state to an equilibrium state in the ion migration region. Based on this change process, the ion migration region can be divided into relaxation and equilibrium zones. The relaxation zone is very thin, where the velocity and temperature of ions vary greatly. In the equilibrium zone, ions and neutral particles can be regarded as a single fluid. This study explores the interaction theory between neutral particles and ions in numerical simulations of plasmas.