NDLI: A passive method for determining plasma dissociation degree using vacuum UV self-absorption spectroscopy

Content Provider	IEEE Xplore Digital Library
Author	Laity, G. Fierro, A. Hatfield, L. Dickens, J. Neuber, A. Frank, K.
Copyright Year	2013
Description	Author affiliation: Dept. of Phys., Friedrich-Alexander Univ. at Erlangen-Nurnberg, Erlangen, Germany (Frank, K.) \|\| Dept. of Electr. Eng., Texas Tech Univ., Lubbock, TX, USA (Laity, G.; Fierro, A.; Hatfield, L.; Dickens, J.; Neuber, A.)
Abstract	Summary form only given. There has been a continued interest in utilizing streamer and spark discharges for new technologies that require low temperature plasma generation at atmospheric pressure, but diagnostics of these plasmas typically require external sources of probing radiation such as UV lamps or laser systems. Specifically, it is desired to measure the dissociated gas density from pulsed surface flashover plasmas, without the use of potentially invasive optical techniques such as two-photon absorption laser induced fluorescence (TALIF) spectroscopy, which may artificially increase the dissociation degree. We demonstrate a method for determining the dissociated gas density of N and H atoms in an $N_{2}/H_{2}$ surface flashover plasma by passively monitoring the self-absorption of intrinsic radiation produced by the $2s^{2}$ $2p^{2}$ $3s→2s^{2}$ $2p^{3}$ NI transition(s) at 120.0 nm, and the 2p→ls HI Lyman-α transition at 121.57 nm. This radiation is partially trapped by the spark plasma, assumed to be of Gaussian cylindrical shape with 500 μm diameter. The resulting emission line shapes can be calculated by inferring the plasma temperature, gas mixture, and the estimated dissociated atom density of each species in the plasma volume of measurement. For example, 80%/20% $N_{2}/H_{2}$ discharges with a measured electron temperature of ~3.0 eV produce peak dissociated concentrations of 2% and 9% for atomic N and H, respectively, during the spark phase ~100 ns after voltage collapse. By assuming the quasi-contiguous approximation of the Holtsmark micro-field due to local electron perturbation of the HI radiators, the Stark line width of Lyman-α radiation yields electron densities on the order of $10^{18}$ $cm^{3}$ during the spark phase. This self-absorption method has been extended to provide density information of surface flashover plasmas in air environments by passively monitoring the $2s^{2}$ $2p^{3}$ $3s→2s^{2}$ $2p^{4}$ OI transitions) at 130.2 nm / 130.5 nm / 130.6 nm, which yield peak dissociated concentrations of 20% and 7% for atomic O and N, respectively.
Starting Page	1
Ending Page	1
File Size	152175
Page Count	1
File Format	PDF
ISBN	9781467351713
ISSN	07309244
DOI	10.1109/PLASMA.2013.6635196
Language	English
Publisher	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Publisher Date	2013-06-16
Publisher Place	USA
Access Restriction	Subscribed
Rights Holder	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subject Keyword	Temperature measurement Atomic measurements Physics Sparks Discharges (electric) Plasma temperature
Content Type	Text
Resource Type	Article
Subject	Atomic and Molecular Physics, and Optics Condensed Matter Physics Electrical and Electronic Engineering

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