Spatiotemporal measurements of striations in a glow discharge’s positive column using laser-collisional induced fluorescence

Spatiotemporal measurements of striations in a glow discharge’s positive column using laser-collisional induced fluorescence

We have observed the behavior of striations caused by ionization waves propagating in low-pressure helium DC discharges using the non-invasive laser-collision induced fluorescence (LCIF) diagnostic. To achieve this, we developed an analytic fit of collisional radiative model (CRM) predictions to int...

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Bibliographic Details
Published in:AIP advances Vol. 13; no. 8; pp. 085015 - 085015-9
Main Authors: White, Z. K., Gott, R. P., Bentz, B. Z., Xu, K. G.
Format: Journal Article
Language:English
Published: Melville American Institute of Physics 01-08-2023
American Institute of Physics (AIP)
AIP Publishing LLC
Subjects:
Diagnostic systems
discharge tube
Distribution functions
electric power
Electron density
ENGINEERING
Fluorescence
gas discharges
Gas pressure
Glow discharges
Helium
Ionization waves
Laser applications
Lasers
Low pressure
MATLAB
optical devices
plasma diagnostics
Positive columns
Striations
wave mechanics
Wave propagation
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Summary:We have observed the behavior of striations caused by ionization waves propagating in low-pressure helium DC discharges using the non-invasive laser-collision induced fluorescence (LCIF) diagnostic. To achieve this, we developed an analytic fit of collisional radiative model (CRM) predictions to interpret the LCIF data and recover quantitative two-dimensional spatial maps of the electron density, ne, and the ratios of LCIF emission states that can be correlated with Te with the use of accurate distribution functions at localized positions within striated helium discharges at 500 mTorr, 750 mTorr, and 1 Torr. To our knowledge, these are the first spatiotemporal, laser-based, experimental measurements of ne in DC striations. The ne and 447:588 ratio distributions align closely with striation theory. Constriction of the positive column appears to occur with decreased gas pressure, as shown by the radial ne distribution. We identify a transition from a slow ionization wave to a fast ionization wave between 750 mTorr and 1 Torr. These experiments validate our analytic fit of ne, allowing the implementation of an LCIF diagnostic in helium without the need to develop a CRM.
Bibliography:National Science Foundation (NSF)
NA0003525; OIA-1655280; SC0014664; SC0020232
USDOE Office of Science (SC), Fusion Energy Sciences (FES)
USDOE Office of Science (SC), Office of Workforce Development for Teachers & Scientists (WDTS)
USDOE National Nuclear Security Administration (NNSA)
SAND-2023-08996J
ISSN:2158-3226
2158-3226
DOI:10.1063/5.0096695