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Title: Dependence of Langmuir probe data on distance from the axis of a collisionless plasma

Abstract

A cylindrical Langmuir probe in a low-density, collisionless plasma (density {approx}10{sup 8} cm{sup -3}, electron temperature 0.2 eV) has been scanned radially through the presheath region to determine the effect of distance from the axis on the current-voltage characteristic. In the ion part of the probe characteristic, the collected ion current decreases with distance from the axis as a consequence of ion acceleration by the presheath. The part of the ion current from charge-exchange collisions remains relatively constant. In the electron part of the probe characteristic, the collected current decreases with distance from the axis, consistent with the existence of a small potential barrier from the presheath between the axis and the probe. The electron temperature from the slope of the probe characteristic is nearly constant across the presheath region. The plasma potential from the Langmuir probe characteristic is also nearly constant, indicating that the probe analysis finds the plasma potential on the axis, even when the probe is not on the axis. The plasma potential from an emissive probe shows an approximately parabolic profile. The plasma potential from the emissive probe and the Boltzmann relation give nearly the same density profile in the presheath that is obtained from themore » Langmuir probe data.« less

Authors:
;  [1]
  1. Center for Integrated Plasma Studies and Department of Physics, University of Colorado, Boulder, Colorado 80309-0390 (United States)
Publication Date:
OSTI Identifier:
20982748
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 101; Journal Issue: 6; Other Information: DOI: 10.1063/1.2709524; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; BOLTZMANN EQUATION; CHARGE EXCHANGE; COLLISIONLESS PLASMA; ELECTRON TEMPERATURE; ION TEMPERATURE; IONS; LANGMUIR PROBE; PLASMA DENSITY; PLASMA POTENTIAL; PLASMA SHEATH

Citation Formats

Knappmiller, Scott, and Robertson, Scott. Dependence of Langmuir probe data on distance from the axis of a collisionless plasma. United States: N. p., 2007. Web. doi:10.1063/1.2709524.
Knappmiller, Scott, & Robertson, Scott. Dependence of Langmuir probe data on distance from the axis of a collisionless plasma. United States. doi:10.1063/1.2709524.
Knappmiller, Scott, and Robertson, Scott. Thu . "Dependence of Langmuir probe data on distance from the axis of a collisionless plasma". United States. doi:10.1063/1.2709524.
@article{osti_20982748,
title = {Dependence of Langmuir probe data on distance from the axis of a collisionless plasma},
author = {Knappmiller, Scott and Robertson, Scott},
abstractNote = {A cylindrical Langmuir probe in a low-density, collisionless plasma (density {approx}10{sup 8} cm{sup -3}, electron temperature 0.2 eV) has been scanned radially through the presheath region to determine the effect of distance from the axis on the current-voltage characteristic. In the ion part of the probe characteristic, the collected ion current decreases with distance from the axis as a consequence of ion acceleration by the presheath. The part of the ion current from charge-exchange collisions remains relatively constant. In the electron part of the probe characteristic, the collected current decreases with distance from the axis, consistent with the existence of a small potential barrier from the presheath between the axis and the probe. The electron temperature from the slope of the probe characteristic is nearly constant across the presheath region. The plasma potential from the Langmuir probe characteristic is also nearly constant, indicating that the probe analysis finds the plasma potential on the axis, even when the probe is not on the axis. The plasma potential from an emissive probe shows an approximately parabolic profile. The plasma potential from the emissive probe and the Boltzmann relation give nearly the same density profile in the presheath that is obtained from the Langmuir probe data.},
doi = {10.1063/1.2709524},
journal = {Journal of Applied Physics},
number = 6,
volume = 101,
place = {United States},
year = {Thu Mar 15 00:00:00 EDT 2007},
month = {Thu Mar 15 00:00:00 EDT 2007}
}