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Title: Effect of electron temperature fluctuations on slowly swept Langmuir probe measurements

Abstract

Swept Langmuir probes are widely used to measure electron temperature (T{sub e}) in laboratory plasmas by performing an exponential fit to the measured volt-ampere (I-V) characteristic. Often the probe voltage sweep frequency is much lower than the characteristic frequencies of the plasma fluctuations and a time-averaged I-V characteristic is used for the fit. We show by numerical modeling that in the presence of T{sub e} fluctuations with frequencies well above the voltage sweep frequency this standard technique applied to a swept single probe tends to read higher than the actual time-averaged T{sub e} provided no correlated plasma potential (V{sub p}) fluctuations are present. In the presence of coupled T{sub e} and V{sub p} fluctuations a slowly swept single probe may read either higher or lower than the average T{sub e}, depending on the relative amplitude and phase of the temperature and potential fluctuations. In contrast, swept double probe measurements of T{sub e} are virtually unaffected by either T{sub e} or V{sub p} fluctuations.

Authors:
; ; ; ; ;  [1]
  1. Center for Energy Research, University of California, San Diego, La Jolla, California 92093 (United States)
Publication Date:
OSTI Identifier:
20641310
Resource Type:
Journal Article
Journal Name:
Review of Scientific Instruments
Additional Journal Information:
Journal Volume: 75; Journal Issue: 10; Conference: 15. topical conference on high temperature plasma diagnostics, San Diego, CA (United States), 19-22 Apr 2004; Other Information: DOI: 10.1063/1.1789623; (c) 2004 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0034-6748
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; AMPLITUDES; ELECTRIC CONDUCTIVITY; ELECTRON TEMPERATURE; FLUCTUATIONS; ION TEMPERATURE; LANGMUIR PROBE; PLASMA; PLASMA POTENTIAL; SIMULATION

Citation Formats

Rudakov, D L, Boedo, J A, Moyer, R A, Stangeby, P C, McLean, A, Watkins, J G, University of Toronto Institute for Aerospace Studies, Toronto, Ontario M3H 5T6, and Sandia National Laboratories, Albuquerque, New Mexico 87185. Effect of electron temperature fluctuations on slowly swept Langmuir probe measurements. United States: N. p., 2004. Web. doi:10.1063/1.1789623.
Rudakov, D L, Boedo, J A, Moyer, R A, Stangeby, P C, McLean, A, Watkins, J G, University of Toronto Institute for Aerospace Studies, Toronto, Ontario M3H 5T6, & Sandia National Laboratories, Albuquerque, New Mexico 87185. Effect of electron temperature fluctuations on slowly swept Langmuir probe measurements. United States. https://doi.org/10.1063/1.1789623
Rudakov, D L, Boedo, J A, Moyer, R A, Stangeby, P C, McLean, A, Watkins, J G, University of Toronto Institute for Aerospace Studies, Toronto, Ontario M3H 5T6, and Sandia National Laboratories, Albuquerque, New Mexico 87185. 2004. "Effect of electron temperature fluctuations on slowly swept Langmuir probe measurements". United States. https://doi.org/10.1063/1.1789623.
@article{osti_20641310,
title = {Effect of electron temperature fluctuations on slowly swept Langmuir probe measurements},
author = {Rudakov, D L and Boedo, J A and Moyer, R A and Stangeby, P C and McLean, A and Watkins, J G and University of Toronto Institute for Aerospace Studies, Toronto, Ontario M3H 5T6 and Sandia National Laboratories, Albuquerque, New Mexico 87185},
abstractNote = {Swept Langmuir probes are widely used to measure electron temperature (T{sub e}) in laboratory plasmas by performing an exponential fit to the measured volt-ampere (I-V) characteristic. Often the probe voltage sweep frequency is much lower than the characteristic frequencies of the plasma fluctuations and a time-averaged I-V characteristic is used for the fit. We show by numerical modeling that in the presence of T{sub e} fluctuations with frequencies well above the voltage sweep frequency this standard technique applied to a swept single probe tends to read higher than the actual time-averaged T{sub e} provided no correlated plasma potential (V{sub p}) fluctuations are present. In the presence of coupled T{sub e} and V{sub p} fluctuations a slowly swept single probe may read either higher or lower than the average T{sub e}, depending on the relative amplitude and phase of the temperature and potential fluctuations. In contrast, swept double probe measurements of T{sub e} are virtually unaffected by either T{sub e} or V{sub p} fluctuations.},
doi = {10.1063/1.1789623},
url = {https://www.osti.gov/biblio/20641310}, journal = {Review of Scientific Instruments},
issn = {0034-6748},
number = 10,
volume = 75,
place = {United States},
year = {Fri Oct 01 00:00:00 EDT 2004},
month = {Fri Oct 01 00:00:00 EDT 2004}
}