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Title: Particle-in-cell study of the ion-to-electron sheath transition

Abstract

The form of a sheath near a small electrode, with bias changing from below to above the plasma potential, is studied using 2D particle-in-cell simulations. When the electrode is biased within T e/2 e below the plasma potential, the electron velocity distribution functions (EVDFs) exhibit a loss-cone type truncation due to fast electrons overcoming the small potential difference between the electrode and plasma. No sheath is present in this regime, and the plasma remains quasineutral up to the electrode. The EVDF truncation leads to a presheath-like density and flow velocity gradients. Once the bias exceeds the plasma potential, an electron sheath is present. In this case, the truncation driven behavior persists, but is accompanied by a shift in the maximum value of the EVDF that is not present in the negative bias cases. In conclusion, the flow moment has significant contributions from both the flow shift of the EVDF maximum, and the loss-cone truncation.

Authors:
 [1];  [1];  [2];  [2];  [2]
  1. Univ. of Iowa, Iowa City, IA (United States)
  2. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Publication Date:
Research Org.:
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1326057
Report Number(s):
SAND-2016-3872J
Journal ID: ISSN 1070-664X; PHPAEN; 647402
Grant/Contract Number:
AC04-94AL85000; AC05-06OR23100; AC04-94SL85000
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; electrodes; plasma sheaths; plasma flows; tensor methods; Boltzmann equations

Citation Formats

Scheiner, Brett, Baalrud, Scott D., Hopkins, Matthew M., Yee, Benjamin T., and Barnat, Edward V. Particle-in-cell study of the ion-to-electron sheath transition. United States: N. p., 2016. Web. doi:10.1063/1.4960382.
Scheiner, Brett, Baalrud, Scott D., Hopkins, Matthew M., Yee, Benjamin T., & Barnat, Edward V. Particle-in-cell study of the ion-to-electron sheath transition. United States. doi:10.1063/1.4960382.
Scheiner, Brett, Baalrud, Scott D., Hopkins, Matthew M., Yee, Benjamin T., and Barnat, Edward V. 2016. "Particle-in-cell study of the ion-to-electron sheath transition". United States. doi:10.1063/1.4960382. https://www.osti.gov/servlets/purl/1326057.
@article{osti_1326057,
title = {Particle-in-cell study of the ion-to-electron sheath transition},
author = {Scheiner, Brett and Baalrud, Scott D. and Hopkins, Matthew M. and Yee, Benjamin T. and Barnat, Edward V.},
abstractNote = {The form of a sheath near a small electrode, with bias changing from below to above the plasma potential, is studied using 2D particle-in-cell simulations. When the electrode is biased within Te/2e below the plasma potential, the electron velocity distribution functions (EVDFs) exhibit a loss-cone type truncation due to fast electrons overcoming the small potential difference between the electrode and plasma. No sheath is present in this regime, and the plasma remains quasineutral up to the electrode. The EVDF truncation leads to a presheath-like density and flow velocity gradients. Once the bias exceeds the plasma potential, an electron sheath is present. In this case, the truncation driven behavior persists, but is accompanied by a shift in the maximum value of the EVDF that is not present in the negative bias cases. In conclusion, the flow moment has significant contributions from both the flow shift of the EVDF maximum, and the loss-cone truncation.},
doi = {10.1063/1.4960382},
journal = {Physics of Plasmas},
number = 8,
volume = 23,
place = {United States},
year = 2016,
month = 8
}

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