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Title: Experimental investigation of double layers in expanding plasmas

Abstract

Double layers (DLs) have been observed in a plasma reactor composed of a source chamber attached to a larger expanding chamber. Positive ion beams generated across the DL were characterized in the low plasma potential region using retarding field energy analyzers. In electropositive gases, DLs were formed at very low pressures (between 0.1 and 1 mTorr) with the plasma expansion forced by a strongly diverging magnetic field. The DL remains static, robust to changes in boundary conditions, and its position is related to the magnetic field lines. The voltage drop across the DL increases with decreasing pressure; i.e., with increasing electron temperature (around 20 V at 0.17 mTorr). DLs were also observed in electronegative gases without a magnetic field over a greater range of pressure (0.5 to 10 mTorr). The actual profile of the electronegative DL is very sensitive to external parameters and intrusive elements, and they propagate at high negative ion fraction. Electrostatic probes measurements and laser-induced photodetachment show discontinuities in all plasma parameters (electron density, electron temperature, negative ion fraction) at the DL position. The voltage drop across the electronegative DL is about 8 V, is independent of the gas pressure and therefore of the electron temperature.

Authors:
; ;  [1]
  1. Laboratoire de Physique et Technologie des Plasmas, Ecole Polytechnique, 91128, Palaiseau Cedex (France)
Publication Date:
OSTI Identifier:
20960127
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 14; Journal Issue: 1; Other Information: DOI: 10.1063/1.2424429; (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; ANIONS; BOUNDARY CONDITIONS; CATIONS; ELECTRON DENSITY; ELECTRON TEMPERATURE; ELECTROSTATIC PROBES; GASES; ION TEMPERATURE; LAYERS; MAGNETIC FIELDS; MAGNETOHYDRODYNAMICS; PLASMA; PLASMA DENSITY; PLASMA EXPANSION; PLASMA POTENTIAL; PLASMA SHEATH; VOLTAGE DROP

Citation Formats

Plihon, N., Chabert, P., and Corr, C. S.. Experimental investigation of double layers in expanding plasmas. United States: N. p., 2007. Web. doi:10.1063/1.2424429.
Plihon, N., Chabert, P., & Corr, C. S.. Experimental investigation of double layers in expanding plasmas. United States. doi:10.1063/1.2424429.
Plihon, N., Chabert, P., and Corr, C. S.. Mon . "Experimental investigation of double layers in expanding plasmas". United States. doi:10.1063/1.2424429.
@article{osti_20960127,
title = {Experimental investigation of double layers in expanding plasmas},
author = {Plihon, N. and Chabert, P. and Corr, C. S.},
abstractNote = {Double layers (DLs) have been observed in a plasma reactor composed of a source chamber attached to a larger expanding chamber. Positive ion beams generated across the DL were characterized in the low plasma potential region using retarding field energy analyzers. In electropositive gases, DLs were formed at very low pressures (between 0.1 and 1 mTorr) with the plasma expansion forced by a strongly diverging magnetic field. The DL remains static, robust to changes in boundary conditions, and its position is related to the magnetic field lines. The voltage drop across the DL increases with decreasing pressure; i.e., with increasing electron temperature (around 20 V at 0.17 mTorr). DLs were also observed in electronegative gases without a magnetic field over a greater range of pressure (0.5 to 10 mTorr). The actual profile of the electronegative DL is very sensitive to external parameters and intrusive elements, and they propagate at high negative ion fraction. Electrostatic probes measurements and laser-induced photodetachment show discontinuities in all plasma parameters (electron density, electron temperature, negative ion fraction) at the DL position. The voltage drop across the electronegative DL is about 8 V, is independent of the gas pressure and therefore of the electron temperature.},
doi = {10.1063/1.2424429},
journal = {Physics of Plasmas},
number = 1,
volume = 14,
place = {United States},
year = {Mon Jan 15 00:00:00 EST 2007},
month = {Mon Jan 15 00:00:00 EST 2007}
}