skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Low pressure hydrogen discharges

Abstract

This article presents a fluid-plasma model of the free-fall regime of maintenance of high-frequency discharges in hydrogen. The obtained results are for the radial profiles of the concentrations and the velocities of electrons, positive H{sup +}, H{sub 2}{sup +}, and H{sub 3}{sup +} ions, negative H{sup -} ions, potential of the radial dc electric field, and electron temperature. The importance of the directed motion of the charged particles in the radial dc electric field, the negative ion behavior in the discharge, and the description of the discharge characteristics by continuous radial profiles, which smoothly cover the total cross section of discharge, are stresses. A strong impact of the negative ions on the formation of the self-consistent discharge structure is shown. The discussions are in terms of changing gas pressure and electron concentration at the discharge axis.

Authors:
; ; ;  [1];  [2];  [3];  [3]
  1. Faculty of Physics, Sofia University, BG-1164 Sofia (Bulgaria)
  2. (Germany)
  3. (Bulgaria)
Publication Date:
OSTI Identifier:
20782522
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 13; Journal Issue: 2; Other Information: DOI: 10.1063/1.2172541; (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; CHARGED-PARTICLE TRANSPORT; ELECTRIC FIELDS; ELECTRON TEMPERATURE; ELECTRONS; FLUIDS; HIGH-FREQUENCY DISCHARGES; HYDROGEN; HYDROGEN IONS 1 MINUS; HYDROGEN IONS 1 PLUS; HYDROGEN IONS 2 PLUS; HYDROGEN IONS 3 PLUS; ION TEMPERATURE; PLASMA; PLASMA POTENTIAL; STRESSES

Citation Formats

Paunska, Ts., Schlueter, H., Shivarova, A., Tarnev, Kh., Institut fuer Experimentalphysik II, Ruhr-Universitaet Bochum, D-44780 Bochum, Faculty of Physics, Sofia University, BG-1164 Sofia, and Department of Applied Physics, Technical University-Sofia, BG-1000. Low pressure hydrogen discharges. United States: N. p., 2006. Web. doi:10.1063/1.2172541.
Paunska, Ts., Schlueter, H., Shivarova, A., Tarnev, Kh., Institut fuer Experimentalphysik II, Ruhr-Universitaet Bochum, D-44780 Bochum, Faculty of Physics, Sofia University, BG-1164 Sofia, & Department of Applied Physics, Technical University-Sofia, BG-1000. Low pressure hydrogen discharges. United States. doi:10.1063/1.2172541.
Paunska, Ts., Schlueter, H., Shivarova, A., Tarnev, Kh., Institut fuer Experimentalphysik II, Ruhr-Universitaet Bochum, D-44780 Bochum, Faculty of Physics, Sofia University, BG-1164 Sofia, and Department of Applied Physics, Technical University-Sofia, BG-1000. Wed . "Low pressure hydrogen discharges". United States. doi:10.1063/1.2172541.
@article{osti_20782522,
title = {Low pressure hydrogen discharges},
author = {Paunska, Ts. and Schlueter, H. and Shivarova, A. and Tarnev, Kh. and Institut fuer Experimentalphysik II, Ruhr-Universitaet Bochum, D-44780 Bochum and Faculty of Physics, Sofia University, BG-1164 Sofia and Department of Applied Physics, Technical University-Sofia, BG-1000},
abstractNote = {This article presents a fluid-plasma model of the free-fall regime of maintenance of high-frequency discharges in hydrogen. The obtained results are for the radial profiles of the concentrations and the velocities of electrons, positive H{sup +}, H{sub 2}{sup +}, and H{sub 3}{sup +} ions, negative H{sup -} ions, potential of the radial dc electric field, and electron temperature. The importance of the directed motion of the charged particles in the radial dc electric field, the negative ion behavior in the discharge, and the description of the discharge characteristics by continuous radial profiles, which smoothly cover the total cross section of discharge, are stresses. A strong impact of the negative ions on the formation of the self-consistent discharge structure is shown. The discussions are in terms of changing gas pressure and electron concentration at the discharge axis.},
doi = {10.1063/1.2172541},
journal = {Physics of Plasmas},
number = 2,
volume = 13,
place = {United States},
year = {Wed Feb 15 00:00:00 EST 2006},
month = {Wed Feb 15 00:00:00 EST 2006}
}
  • A theoretical study of the complex interplay between the vibrational kinetics and the plasma dynamics in low-pressure hydrogen plasmas produced by radio frequency discharges is performed. The study is realized by means of a one-dimensional particle model with five species (e, H{sup +}, H{sub 2}{sup +}, H{sub 3}{sup +}, and H{sup -}) while the vibrational/dissociation kinetics is based on a continuum model and the two are self-consistently coupled. In particular, we analyze the influence of pressure.
  • Absolute excitation probabilities from very low to moderate-current hydrogen discharges in parallel-plane geometry are measured and used to test models. Relative emission data are obtained for the H{sub {alpha}} line, the H{sub 2} (a{sup 3}{Sigma}{yields}b{sup 3}{Pi}) near-UV continuum, and the H{sub 2} (G{sup 1}{Sigma}{yields}B{sup 1}{Pi}{sub u}{sup +}) band at pressures of 0.5 and 2 Torr, a 1.05 cm gap, and voltages from 300 to 900 V. Electron behavior is traced using the first negative (A{sup 2}{Sigma}{sub g}{yields} X{sup 2}{Pi}{sub u}, {nu}'' = 0 {yields}{nu}' = 0) band of N{sub 2}{sup +} by adding 2% N{sub 2}. Relative measurements of H{submore » {alpha}}, H{sub 2} near-UV, and N{sub 2} 1st negative emission are placed on a absolute scale by normalization to published measurements and Boltzmann calculations of electron excitation. Emission probabilities calculated using a multi-beam kinetics model for the electrons, H{sup +}, H{sub 2}{sup +}, H{sub 3}{sup +}, H{sup -}, H, and H{sub 2} are compared with the calibrated experiments. Fast H atoms are calculated to produce H{sub {alpha}} excitation that is comparable with that of electrons. The calculated emission intensities for H{sub {alpha}} and H{sub 2} near-UV continuum are within a factor of three of the absolute measurements for a range of 5000:1 in current and 4:1 in hydrogen pressure. Calculations at 2 Torr show that most of the space charge electric field responsible for the cathode fall is produced by H{sub 3}{sup +} ions.« less
  • Negative hydrogen ion sources, for instance for fusion devices, currently attract considerable attention. To generate the precursors—highly rovibrationally excited hydrogen molecules—for negative hydrogen ions effectively by electron excitation, a thin dielectric layer is introduced to cover the surface of the electrically grounded electrode of two parallel metal plates in a low-pressure hydrogen capacitive discharge driven by combined rf and pulse power sources. To understand the characteristics of such discharges, particle-in-cell simulations are conducted to study the effects that the single dielectric layer would bring onto the discharges. The simulation results show that the dielectric layer leads to a much highermore » plasma density and a much larger production rate of highly vibrationally excited hydrogen molecules compared to discharges without the dielectric layer on the electrode. Further investigation indicates that the nonlinear oscillation of the electrons induced by the nanosecond-pulse continues until it is finally damped down and does not show any dependence on the pulse plateau-time, which is in stark contrast to the case without the dielectric layer present. The physical reason for this phenomenon is explored and explained.« less
  • In low-pressure capacitively coupled plasmas, high-energy electrons are collisionlessly heated by large rf fields in the sheaths while low-energy electrons are confined in the bulk plasma by the ambipolar potential. Low-energy electrons are typically inefficiently heated due to their low collisionality and the weak rf electric field present in the bulk. It is shown, however, that as a result of the nonlinear interaction between the electron motion and the weak rf field present in the bulk, low-energy electrons can be efficiently heated. Electrons in the bulk that bounce inside the electrostatic potential well with a frequency equal to the rfmore » excitation frequency are efficiently heated by the coherent interaction with the rf field. This resonant collisionless heating can be very efficient and manifest itself as a plateau in the electron energy probability function.« less