Use of the 447 nm He I line to determine electron concentrations |
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Authors: | Albin Czernichowski Joseph Chapelle |
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Institution: | University of Orleans, 45046 Orleans Cédex, France |
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Abstract: | The helium 447 nm complex line has been excited in a wall-stabilized arc fed at atmospheric pressure by pure He, He-H2, He-Ne-H2 or He-Ar-H2 mixtures. Photoelectric endon observations of the central part of the arc channel were made with high spatial (1/600) and spectral (53,000) resolution.A collection of 88 helium 447 nm line profiles, of which 75 were recorded simultaneously with Hβ and Ne I or Ar II line profiles, yielded information about the electron concentration (2 X 1020-2 X 1022 m-3), temperature and relative ion composition of the plasma. Plots have been made of the forbidden to allowed peak separations (S), forbidden to allowed relative intensities of the peaks (F/A) and dips (i.e. the minimum intensities between lines) to allowed peak intensities (D/A) as functions of electron concentration, temperature and ionic composition in different plasmas.The peak separations depend only on the electron concentration. Other characteristic line-profile parameters (F/A and D/A) show weak ion motion with a strong electron-concentration influence. We propose simple formulae, which may be useful for practical determinations of the electron concentrations in helium-containing plasmas with an accuracy of ±15% and without taking into account either the chemical composition of the plasma or the temperature. |
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