Numerical solutions to a kinetic model for sheath and presheath with charge exchange collisions of ions

Summary form only given. A kinetic model of the sheath and presheath is presented that includes the effects of charge-exchange collisions on the ions. The collisions are modeled as a sink for accelerated ions and as a source of cold ions. Solutions are obtained by numerical integration of Poisson´s equation from a point near the plasma midplane to the wall. As the mean free path is decreased, the current density at the wall decreases and the potential profile in the presheath shows a smooth transition from a parabolic profile to a nearly cubic profile determined by the ion mobility. An approximate expression is found for the ion flux to the wall in the collisional limit.