Cutoff effects of electron velocity distribution to the properties of plasma parameters near the plasma-sheath boundary

Journal Article · Tue Nov 15 04:00:00 EST 2011 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.3659022· OSTI ID:22047092

Jelic, N ^[1]

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1. Association EURATOM-OeAW, Institute for Theoretical Physics, University of Innsbruck, A-6020 Innsbruck (Austria)

The plasma properties under high thermodynamic non-equilibrium condition, established due to the presence of electrically biased electrode, are investigated. Assumption of electron cut-off velocity distribution function (VDF), as done by Andrews and Varey in their investigations of the sheath region [J. Phys. A 3, 413 (1970)], has been extended here to both plasma and sheath regions. Analytic expressions for the moments of electron VDF, as well as for the electron screening temperature function dependence on the plasma-sheath local potential are derived. In deriving the ion velocity distribution the ''standard'' assumption of strict plasma quasineutrality, or equivalently vanishing of the plasma Debye length, is employed, whereas the ions are assumed to be generated at rest over the plasma region. However, unlike the standard approach of solving the plasma equation, where pure Boltzmann electron density profile is used, here we employ modified Boltzmann's electron density profile, due to cutoff effect of the electron velocity distribution. It is shown that under these conditions the quasineutrality equation solution is characterised by the electric field singularity for any negative value of the electrode bias potential as measured with respect to the plasma potential. The point of singularity i.e., the plasma length and its dependence on the electrode bias and sheath potential is established for the particular case of ionization profile mechanism proportional to the local electron density. Relevant parameters for the kinetic Bohm criterion are explicitly calculated for both ions and electrons, for arbitrary electrode bias.

• OSTI ID: 22047092
• Journal Information: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 11 Vol. 18; ISSN PHPAEN; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
BOHM CRITERION
DEBYE LENGTH
DISTRIBUTION FUNCTIONS
ELECTRIC FIELDS
ELECTRON DENSITY
ELECTRON TEMPERATURE
ELECTRONS
ION TEMPERATURE
IONIZATION
IONS
PLASMA
PLASMA DENSITY
PLASMA POTENTIAL
PLASMA SHEATH
THERMODYNAMICS