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Title: Langmuir Probe Measurements in Plasma Shadows

Abstract

When immersing a target into a plasma streaming along magnetic field lines, a distinct shadow region extending over large distances is observed by the naked eye downstream of the target.In this work we present an experimental study of the effect applying Langmuir probes. In contrast to expectations, there are only marginal changes in the profiles of temperature and density behind masks that cut away about 50% of the plasma cross-section. On the other hand, the mean density is drastically reduced by an order of magnitude. First attempts to simulate the observations by solving the classical 2D diffusion equation were not successful.

Authors:
 [1]; ;  [1];  [2]
  1. Max-Planck-Institut fuer Plasmaphysik, TI Greifswald, Wendelsteinstr. 1, 17491 Greifswald, EURATOM Association (Germany)
  2. (Germany)
Publication Date:
OSTI Identifier:
20797955
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 812; Journal Issue: 1; Conference: PLASMA 2005: International conference on research and applications of plasmas; 3. German-Polish conference on plasma diagnostics for fusion and applications; 5. French-Polish seminar on thermal plasma in space and laboratory, Opole-Turawa (Poland), 6-9 Sep 2005; Other Information: DOI: 10.1063/1.2168881; (c) 2006 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; DIFFUSION EQUATIONS; DISTANCE; ELECTRON TEMPERATURE; ION TEMPERATURE; LANGMUIR PROBE; MAGNETIC FIELDS; PLASMA; PLASMA DENSITY; PLASMA DIAGNOSTICS; RADIATION TRANSPORT

Citation Formats

Waldmann, O., Koch, B., Fussmann, G., and Humboldt-Universitaet zu Berlin, Institut fuer Physik, PLA, Newtonstr. 15, 12489 Berlin. Langmuir Probe Measurements in Plasma Shadows. United States: N. p., 2006. Web. doi:10.1063/1.2168881.
Waldmann, O., Koch, B., Fussmann, G., & Humboldt-Universitaet zu Berlin, Institut fuer Physik, PLA, Newtonstr. 15, 12489 Berlin. Langmuir Probe Measurements in Plasma Shadows. United States. doi:10.1063/1.2168881.
Waldmann, O., Koch, B., Fussmann, G., and Humboldt-Universitaet zu Berlin, Institut fuer Physik, PLA, Newtonstr. 15, 12489 Berlin. Sun . "Langmuir Probe Measurements in Plasma Shadows". United States. doi:10.1063/1.2168881.
@article{osti_20797955,
title = {Langmuir Probe Measurements in Plasma Shadows},
author = {Waldmann, O. and Koch, B. and Fussmann, G. and Humboldt-Universitaet zu Berlin, Institut fuer Physik, PLA, Newtonstr. 15, 12489 Berlin},
abstractNote = {When immersing a target into a plasma streaming along magnetic field lines, a distinct shadow region extending over large distances is observed by the naked eye downstream of the target.In this work we present an experimental study of the effect applying Langmuir probes. In contrast to expectations, there are only marginal changes in the profiles of temperature and density behind masks that cut away about 50% of the plasma cross-section. On the other hand, the mean density is drastically reduced by an order of magnitude. First attempts to simulate the observations by solving the classical 2D diffusion equation were not successful.},
doi = {10.1063/1.2168881},
journal = {AIP Conference Proceedings},
number = 1,
volume = 812,
place = {United States},
year = {Sun Jan 15 00:00:00 EST 2006},
month = {Sun Jan 15 00:00:00 EST 2006}
}
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  • Measurements of the plasma potential, electron density, effective electron temperature, and electron energy distribution function (EEDF) have been performed with Langmuir probes in planar, electrostatically shielded, low-pressure inductively coupled plasmas. The plasma source is a modification of the Gaseous Electronics Conference RF Reference Cell [P. J. Hargis {ital et al.}, Rev. Sci. Instrum. {bold 65}, 140 (1994)] with the upper electrode replaced by a five-turn planar coil and a quartz vacuum interface. Four different rare gases (Ar, Kr, Xe, and Ne), a He:Ar (96:4) mixture, and O{sub 2} and N{sub 2} were investigated. We found that with increasing ionization potentialmore » of the rare gas the electron density decreases, while the effective electron temperature and the plasma potential increase. Non-Maxwellian EEDFs were observed for all energies for O{sub 2} and N{sub 2} discharges as well as for the rare gases above the energy range for elastic collisions. Spatially resolved measurements confirm that the EEDF is determined by spatially averaged quantities instead of the local electric field. {copyright} {ital 1997} {ital The American Physical Society}« less