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Title: Sheath structure in a magnetized plasma

Abstract

The sheath formed between a magnetized plasma and a particle absorbing wall is examined for the case in which the magnetic field intercepts the wall at a small angle 0[degree][lt][epsilon][approx lt]9[degree], where sin [epsilon]=[bold B][center dot][ital [cflx n]]/[vert bar][ital B][vert bar], and [ital [cflx n]] is the unit normal to the wall. The model is time-independent and one-dimensional (1-D) with all functions varying only in the direction normal to the wall. The ions are modeled by a Maxwellian velocity distribution which is modified by the condition that ions, which would have hit the wall, are absent. For the electrons a fluid description is used, including the effects of electron--neutral collisions. The transport of particles due to turbulent electrostatic fluctuations is modeled by a constant electric field perpendicular to both [bold B] and [ital [cflx n]]. It is found that in the range of angles under consideration, there are two distinct regimes of sheath formation. If [epsilon][approx lt][bar [nu]]=[nu]/[Omega][sub [ital e]] (grazing incidence), where [nu] is the electron--neutral collision frequency and [Omega][sub [ital e]] is the electron cyclotron frequency, then the properties of the sheath are determined by a parameter [lambda] which is the ratio of the convective ([bold E][times][bold B])more » and diffusive electron flows. If [lambda][approx lt]1, the wall potential is negative and the sheath scale length is on the order of an ion gyroradius. If [lambda][approx gt]1, the wall potential is positive and, for large [lambda], the sheath is characterized by two scales: a short length, which is a decreasing function of [lambda], adjacent to the wall, and the ion gyroradius farther from the wall. For [epsilon][much gt][bar [nu]], (oblique incidence) the potential at the wall is negative with a magnitude close to that of the unmagnetized plasma and is only weakly dependent on [epsilon].« less

Authors:
; ;  [1]
  1. Department of Physics, University of California, Los Angeles, Los Angeles, California 90024-1547 (United States)
Publication Date:
OSTI Identifier:
6493853
Resource Type:
Journal Article
Journal Name:
Physics of Fluids B; (United States)
Additional Journal Information:
Journal Volume: 5:6; Journal ID: ISSN 0899-8221
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; PLASMA SHEATH; MAGNETIC FIELDS; MAGNETIZATION; ONE-DIMENSIONAL CALCULATIONS; ORBITS; WALL EFFECTS; 700350* - Plasma Production, Heating, Current Drive, & Interactions- (1992-)

Citation Formats

Holland, D L, Fried, B D, and Morales, G J. Sheath structure in a magnetized plasma. United States: N. p., 1993. Web. doi:10.1063/1.860806.
Holland, D L, Fried, B D, & Morales, G J. Sheath structure in a magnetized plasma. United States. https://doi.org/10.1063/1.860806
Holland, D L, Fried, B D, and Morales, G J. 1993. "Sheath structure in a magnetized plasma". United States. https://doi.org/10.1063/1.860806.
@article{osti_6493853,
title = {Sheath structure in a magnetized plasma},
author = {Holland, D L and Fried, B D and Morales, G J},
abstractNote = {The sheath formed between a magnetized plasma and a particle absorbing wall is examined for the case in which the magnetic field intercepts the wall at a small angle 0[degree][lt][epsilon][approx lt]9[degree], where sin [epsilon]=[bold B][center dot][ital [cflx n]]/[vert bar][ital B][vert bar], and [ital [cflx n]] is the unit normal to the wall. The model is time-independent and one-dimensional (1-D) with all functions varying only in the direction normal to the wall. The ions are modeled by a Maxwellian velocity distribution which is modified by the condition that ions, which would have hit the wall, are absent. For the electrons a fluid description is used, including the effects of electron--neutral collisions. The transport of particles due to turbulent electrostatic fluctuations is modeled by a constant electric field perpendicular to both [bold B] and [ital [cflx n]]. It is found that in the range of angles under consideration, there are two distinct regimes of sheath formation. If [epsilon][approx lt][bar [nu]]=[nu]/[Omega][sub [ital e]] (grazing incidence), where [nu] is the electron--neutral collision frequency and [Omega][sub [ital e]] is the electron cyclotron frequency, then the properties of the sheath are determined by a parameter [lambda] which is the ratio of the convective ([bold E][times][bold B]) and diffusive electron flows. If [lambda][approx lt]1, the wall potential is negative and the sheath scale length is on the order of an ion gyroradius. If [lambda][approx gt]1, the wall potential is positive and, for large [lambda], the sheath is characterized by two scales: a short length, which is a decreasing function of [lambda], adjacent to the wall, and the ion gyroradius farther from the wall. For [epsilon][much gt][bar [nu]], (oblique incidence) the potential at the wall is negative with a magnitude close to that of the unmagnetized plasma and is only weakly dependent on [epsilon].},
doi = {10.1063/1.860806},
url = {https://www.osti.gov/biblio/6493853}, journal = {Physics of Fluids B; (United States)},
issn = {0899-8221},
number = ,
volume = 5:6,
place = {United States},
year = {Tue Jun 01 00:00:00 EDT 1993},
month = {Tue Jun 01 00:00:00 EDT 1993}
}