U.S. Department of EnergyOffice of Scientific and Technical Information
Electron density and gas density measurements in a millimeter-wave discharge
Abstract
Electron density and neutral gas density have been measured in a non-equilibrium air breakdown plasma using optical emission spectroscopy and two-dimensional laser interferometry, respectively. A plasma was created with a focused high frequency microwave beam in air. Experiments were run with 110 GHz and 124.5 GHz microwaves at powers up to 1.2 MW. Microwave pulses were 3 microsec. long at 110 GHz and 2.2 microsec. long at 124.5 GHz. Electron density was measured over a pressure range of 25 to 700 Torr as the input microwave power was varied. Electron density was found to be close to the critical density over the pressure range studied and to vary weakly with input power. Neutral gas density was measured over a pressure range from 150 to 750 Torr at power levels high above the threshold for initiating breakdown. The two-dimensional structure of the neutral gas density was resolved. Intense, localized heating was found to occur hundreds of nanoseconds after visible plasma formed. This heating led to neutral gas density reductions of greater than 80% where peak plasma densities occurred. Spatial and temporal structure of gas heating at atmospheric pressure were found to agree well with numerical simulations.
- Authors:
-
- OSTI
- Publication Date:
- DOE Contract Number:
- FC02-93ER54186
- Research Org.:
- Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Plasma Science and Fusion Center
- Sponsoring Org.:
- USDOE Office of Science (SC), Fusion Energy Sciences (FES)
- Subject:
- 70 PLASMA PHYSICS AND FUSION TECHNOLOGY
- OSTI Identifier:
- 1880443
- DOI:
- https://doi.org/10.7910/DVN/0ZADQU
Citation Formats
Schaub, S. C., Hummelt, J. S., Guss, W. C., Shapiro, M. A., and Temkin, R. J. Electron density and gas density measurements in a millimeter-wave discharge. United States: N. p., 2018.
Web. doi:10.7910/DVN/0ZADQU.
Schaub, S. C., Hummelt, J. S., Guss, W. C., Shapiro, M. A., & Temkin, R. J. Electron density and gas density measurements in a millimeter-wave discharge. United States. doi:https://doi.org/10.7910/DVN/0ZADQU
Schaub, S. C., Hummelt, J. S., Guss, W. C., Shapiro, M. A., and Temkin, R. J. 2018.
"Electron density and gas density measurements in a millimeter-wave discharge". United States. doi:https://doi.org/10.7910/DVN/0ZADQU. https://www.osti.gov/servlets/purl/1880443. Pub date:Wed Dec 05 04:00:00 UTC 2018
@article{osti_1880443,
title = {Electron density and gas density measurements in a millimeter-wave discharge},
author = {Schaub, S. C. and Hummelt, J. S. and Guss, W. C. and Shapiro, M. A. and Temkin, R. J.},
abstractNote = {Electron density and neutral gas density have been measured in a non-equilibrium air breakdown plasma using optical emission spectroscopy and two-dimensional laser interferometry, respectively. A plasma was created with a focused high frequency microwave beam in air. Experiments were run with 110 GHz and 124.5 GHz microwaves at powers up to 1.2 MW. Microwave pulses were 3 microsec. long at 110 GHz and 2.2 microsec. long at 124.5 GHz. Electron density was measured over a pressure range of 25 to 700 Torr as the input microwave power was varied. Electron density was found to be close to the critical density over the pressure range studied and to vary weakly with input power. Neutral gas density was measured over a pressure range from 150 to 750 Torr at power levels high above the threshold for initiating breakdown. The two-dimensional structure of the neutral gas density was resolved. Intense, localized heating was found to occur hundreds of nanoseconds after visible plasma formed. This heating led to neutral gas density reductions of greater than 80% where peak plasma densities occurred. Spatial and temporal structure of gas heating at atmospheric pressure were found to agree well with numerical simulations.},
doi = {10.7910/DVN/0ZADQU},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Wed Dec 05 04:00:00 UTC 2018},
month = {Wed Dec 05 04:00:00 UTC 2018}
}