Abstract
The region between a Maxwellian plasma source and a floating or current-carrying surface is described by a static, one-dimensional collisionless kinetic sheath model. In the plasma source, electrons, negative ions, and several positive ion species with different temperatures can be included. The surface (wall) can emit electrons and/or negative ions. When the flux of surface-emitted negative ions and/or electrons reaches a critical value, the sheath becomes space-charge saturated, which leads to the formation of a virtual cathode in front of the emitting wall and sets the maximum current density that can be transported from the surface to the plasma. The analytical results are benchmarked against a particle-in-cell code.
Highlights
In plasma reactors, the plasma-sheath acts as a transition between the plasma and walls.[1,2,3,4] Because it is a non-Maxwellian and non-neutral region, it has a substantial influence on the particle and energy transport to a plasma-facing component
The region between a Maxwellian plasma source and a floating or current-carrying surface is described by a static, one-dimensional collisionless kinetic sheath model
When the flux of surface-emitted negative ions and/or electrons reaches a critical value, the sheath becomes space-charge saturated, which leads to the formation of a virtual cathode in front of the emitting wall and sets the maximum current density that can be transported from the surface to the plasma
Summary
The plasma-sheath acts as a transition between the plasma and walls.[1,2,3,4] Because it is a non-Maxwellian and non-neutral region, it has a substantial influence on the particle and energy transport to a plasma-facing component. The execution time of one spatial dimension particle-in-cell simulation can be several hours if many particle species with different masses or high densities in the plasma bulk and/or surface emission have to be included. Analytical models can solve tens of different cases with a time scale in the order of the second For this reason, it is very desirable to develop or extend, as done in this paper, an analytical model capable of solving sheath potential and density profiles of multiple plasma and surface-emitted species. The presented results were obtained from a fully kinetic treatment of the plasma- and wall-emitted particles It is based on the use of a cut-off particle energy leading to truncated velocity distribution functions for all the involved species, i.e., source and wallemitted particles. VII on the results presented here and Campanell’s inverse sheath theory.[29,30]
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