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Title: Electrode microwave discharge in nitrogen: Structure and gas temperature

Abstract

Electrode microwave discharges in nitrogen at pressures of 1-16 Torr and input microwave powers of 30-180 W have been studied by space-resolved emission spectroscopy. It is shown that the discharge is highly nonuniform. The relative intensities of the first and second positive nitrogen bands, as well as of the first negative band of nitrogen ions, are found to vary significantly throughout a discharge because, in different discharge regions, emitting particles are excited by different mechanisms. The gas temperature was determined by the method of the unresolved rotational structure of different sequences of the emission spectra of the second positive system of nitrogen.

Authors:
; ;  [1]
  1. Russian Academy of Sciences, Topchiev Institute of Petrochemical Synthesis (Russian Federation)
Publication Date:
OSTI Identifier:
21100201
Resource Type:
Journal Article
Resource Relation:
Journal Name: Plasma Physics Reports; Journal Volume: 33; Journal Issue: 2; Other Information: DOI: 10.1134/S1063780X07020109; Copyright (c) 2007 Nauka/Interperiodica; Article Copyright (c) 2007 Pleiades Publishing, Ltd; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; ELECTRODES; EMISSION SPECTRA; EMISSION SPECTROSCOPY; HIGH-FREQUENCY DISCHARGES; MICROWAVE RADIATION; NITROGEN; NITROGEN IONS

Citation Formats

Lebedev, Yu. A., Solomakhin, P. V., and Shakhatov, V. A.. Electrode microwave discharge in nitrogen: Structure and gas temperature. United States: N. p., 2007. Web. doi:10.1134/S1063780X07020109.
Lebedev, Yu. A., Solomakhin, P. V., & Shakhatov, V. A.. Electrode microwave discharge in nitrogen: Structure and gas temperature. United States. doi:10.1134/S1063780X07020109.
Lebedev, Yu. A., Solomakhin, P. V., and Shakhatov, V. A.. Thu . "Electrode microwave discharge in nitrogen: Structure and gas temperature". United States. doi:10.1134/S1063780X07020109.
@article{osti_21100201,
title = {Electrode microwave discharge in nitrogen: Structure and gas temperature},
author = {Lebedev, Yu. A. and Solomakhin, P. V. and Shakhatov, V. A.},
abstractNote = {Electrode microwave discharges in nitrogen at pressures of 1-16 Torr and input microwave powers of 30-180 W have been studied by space-resolved emission spectroscopy. It is shown that the discharge is highly nonuniform. The relative intensities of the first and second positive nitrogen bands, as well as of the first negative band of nitrogen ions, are found to vary significantly throughout a discharge because, in different discharge regions, emitting particles are excited by different mechanisms. The gas temperature was determined by the method of the unresolved rotational structure of different sequences of the emission spectra of the second positive system of nitrogen.},
doi = {10.1134/S1063780X07020109},
journal = {Plasma Physics Reports},
number = 2,
volume = 33,
place = {United States},
year = {Thu Feb 15 00:00:00 EST 2007},
month = {Thu Feb 15 00:00:00 EST 2007}
}
  • The parameters of the electrode region of an electrode microwave discharge in nitrogen are studied by emission spectroscopy. The radial and axial distributions of the intensities of the bands of the second (N{sub 2}(C{sup 3{Pi}}{sub u} {sup {yields}}B{sup 3{Pi}}{sub g})) and first (N{sub 2}(B{sup 3{Pi}}{sub g} {sup {yields}}A{sup 3{Sigma}}{sub u}{sup +})) positive systems of molecular nitrogen and the first negative system of nitrogen ions (N{sub 2}{sup +} (B{sup 2{Sigma}}{sub u}{sup +} {sup {yields}}X{sup 2{Sigma}}{sub g}{sup +})), the radial profiles of the electric field E and the electron density N{sub e}, and the absolute populations of the vibrational levels v{sub C}more » = 0-4 of the C{sup 3{Pi}}{sub u} excited state of N{sub 2} and the vibrational level v{sub Bi} = 0 of the B{sup 2{Sigma}}{sub u}{sup +} excited state of a molecular nitrogen ion are determined. The population temperature of the first vibrational level T{sub V} of the ground electronic state X{sup 1{Sigma}}{sub g}{sup +} of N{sub 2} and the excitation temperature T{sub C} of the C{sup 3{Pi}}{sub u} state in the electrode region of the discharge are measured. The radius of the spherical region and the spatially integrated plasma emission spectra are studied as functions of the incident microwave power and gas pressure. A method for determining the electron density and the microwave field strength from the plasma emission characteristics is described in detail.« less
  • Excitation of a microwave discharge at the end of a cylindrical electrode in nitrogen at a pressure of 1 Torr and incident powers of 60-140 W was investigated experimentally by using K-008 and K-011 video cameras and analyzing oscillograms of discharge emission. The times during which the discharge is established in the radial and axial directions are found to be on the order of 10{sup -4} and 10{sup -2} s, respectively. The results obtained are analyzed using one-dimensional simulations of a discharge in nitrogen in a quasistatic approximation. The kinetic scheme includes 50 processes involving electrons, ions, and excited moleculesmore » and atoms. The time evolution of the concentrations of molecular nitrogen in the N{sub 2}(C{sup 3}II{sub u}) and N{sub 2}(B{sup 3}II{sub g}) states, responsible for the recorded discharge emission, is compared with the experimental data.« less
  • Spatial distributions of charged particle concentration, electron temperature, and DC potential in an electrode microwave discharge in nitrogen at a pressure of 1 Torr have been measured using the double electric probe method. It has been shown that, near the electrode/antenna, the charged particle concentration exceeds a critical value. The concentration and heterogeneity of the discharge increase with increasing microwave power.
  • Nitrogen vibrational level population in the electronic ground state is charge in air are determined by active Raman spectroscopy. (AIP)
  • The creation of powerful microwave generators using relativistic electron beams has stimulated theoretical and experimental investigations of gas discharges in ultrahigh microwave fields. The quiver energy {var_epsilon}{sub {approximately}} of the electrons in such a discharge is substantially greater than the ionization potential of the gas molecules: {var_epsilon}=eE{sup 2}/2m({omega}{sup 2}+v{sup 2}){much_gt}1, where E and {omega} are the amplitude and frequency of the high-frequency field, e and m are the electron charge and mass, and v is the effective collision frequency of electrons with molecules. The electron energy distribution function which develops under these conditions is quite far from equilibrium, and themore » ionization frequency v{sub i} becomes a weak function of the field amplitude. The dependence of the other constants of the critical processes, in this range of E/{omega} can be strongly decreasing in energy, due to the behavior of the corresponding cross section as a function of the electron energy. In experiments this gives rise to effects such as the delay in the optical emission of the discharge relative to the microwave pulse, and disparities in the spatial distribution of the emissivity and the electron density. These kinetic processes can exercise considerable influence on the parameters of a nanosecond microwave discharge, determining the instability of the discharge plasma and its decay and emissivity. In this work we present results of calculations of the excitation coefficients for electronic levels of nitrogen molecules in an ultrastrong microwave field. 11 refs., 2 figs.« less