A fully kinetic, self-consistent particle simulation model of the collisionless plasma–sheath region

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Abstract
A fully kinetic particle‐in‐cell (PIC) model is used to self‐consistently determine the steady‐state potential profile in a collisionless plasma that contacts a floating, absorbing boundary. To balance the flow of particles to the wall, a distributed source region is used to inject particles into the one‐dimensional system. The effect of the particle source distribution function on the source region and collector sheath potential drops, and particle velocity distributions is investigated. The ion source functions proposed by Emmert et al. [Phys. Fluids 2 3, 803 (1980)] and Bissell and Johnson [Phys. Fluids 3 0, 779 (1987)] (and various combinations of these) are used for the injection of both ions and electrons. The values of the potential drops obtained from the PIC simulations are compared to those from the theories of Emmert et al., Bissell and Johnson, and Scheuer and Emmert [Phys. Fluids 3 1, 3645 (1988)], all of which assume that the electron density is related to the plasma potential via the Boltzmann relation. The values of the source region and total potential drop are found to depend on the choice of the electron source function, as well as the ion source function. The question of an infinite electric field at the plasma–sheath interface, which arises in the analyses of Bissell and Johnson and Scheuer and Emmert, is also addressed.