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Title: Kinetic model for the collisionless sheath of a collisional plasma

Abstract

Collisional plasmas typically have mean-free-path still much greater than the Debye length, so the sheath is mostly collisionless. Once the plasma density, temperature, and flow are specified at the sheath entrance, the profile variation of electron and ion density, temperature, flow speed, and conductive heat fluxes inside the sheath is set by collisionless dynamics, and can be predicted by an analytical kinetic model distribution. Finally, these predictions are contrasted in this paper with direct kinetic simulations, showing good agreement.

Authors:
 [1];  [1]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24); USDOE Office of Science (SC), Advanced Scientific Computing Research (ASCR) (SC-21); USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1409762
Report Number(s):
LA-UR-16-21847
Journal ID: ISSN 1070-664X
Grant/Contract Number:
AC52-06NA25396
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 23; Journal Issue: 8; Journal ID: ISSN 1070-664X
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; plasma sheaths; plasma temperature; plasma flows; collision theories; heat conduction

Citation Formats

Tang, Xian-Zhu, and Guo, Zehua. Kinetic model for the collisionless sheath of a collisional plasma. United States: N. p., 2016. Web. doi:10.1063/1.4960321.
Tang, Xian-Zhu, & Guo, Zehua. Kinetic model for the collisionless sheath of a collisional plasma. United States. doi:10.1063/1.4960321.
Tang, Xian-Zhu, and Guo, Zehua. 2016. "Kinetic model for the collisionless sheath of a collisional plasma". United States. doi:10.1063/1.4960321. https://www.osti.gov/servlets/purl/1409762.
@article{osti_1409762,
title = {Kinetic model for the collisionless sheath of a collisional plasma},
author = {Tang, Xian-Zhu and Guo, Zehua},
abstractNote = {Collisional plasmas typically have mean-free-path still much greater than the Debye length, so the sheath is mostly collisionless. Once the plasma density, temperature, and flow are specified at the sheath entrance, the profile variation of electron and ion density, temperature, flow speed, and conductive heat fluxes inside the sheath is set by collisionless dynamics, and can be predicted by an analytical kinetic model distribution. Finally, these predictions are contrasted in this paper with direct kinetic simulations, showing good agreement.},
doi = {10.1063/1.4960321},
journal = {Physics of Plasmas},
number = 8,
volume = 23,
place = {United States},
year = 2016,
month = 8
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record

Citation Metrics:
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  • Cited by 1
  • Collisional plasmas typically have mean-free-path still much greater than the Debye length, so the sheath is mostly collisionless. Once the plasma density, temperature, and flow are specified at the sheath entrance, the profile variation of electron and ion density, temperature, flow speed, and conductive heat fluxes inside the sheath is set by collisionless dynamics, and can be predicted by an analytical kinetic model distribution. These predictions are contrasted here with direct kinetic simulations, showing good agreement.
  • 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 {ital et} {ital al}. (Phys. Fluids {bold 23}, 803 (1980)) and Bissell and Johnson (Phys. Fluids {bold 30}, 779 (1987)) (and various combinationsmore » of these) are used for the injection of both ions {ital and} electrons. The values of the potential drops obtained from the PIC simulations are compared to those from the theories of Emmert {ital et} {ital al}., Bissell and Johnson, and Scheuer and Emmert (Phys. Fluids {bold 31}, 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.« less
  • Cited by 4
  • Sheath energy transmission governs the plasma energy exhaust onto a material surface. The ion channel is dominated by convection, but the electron channel has a significant thermal conduction component, which is dominated by the Knudsen layer effect in the presence of an absorbing wall. First-principle kinetic simulations reveal a robustly supersonic sheath entry flow. The ion sheath energy transmission and the sheath potential are accurately predicted by a sheath model of truncated bi-Maxwellian electron distribution. The electron energy transmission is further enhanced by a parallel heat flux of the perpendicular degrees of freedom.