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

Title: Electron density and gas density measurements in a millimeter-wave discharge

Abstract

Here, 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 μs long at 110 GHz and 2.2 μs 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, where the collisional plasma frequency is equal to the microwave frequency, 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 structure and temporal dynamics of gas heating at atmospheric pressuremore » were found to agree well with published numerical simulations.« less

Authors:
ORCiD logo [1];  [1];  [1];  [1]; ORCiD logo [1]
  1. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Plasma Science and Fusion Center
Publication Date:
Research Org.:
Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES); US Air Force Office of Scientific Research (AFOSR)
OSTI Identifier:
1467854
Alternate Identifier(s):
OSTI ID: 1287753
Grant/Contract Number:  
FC02-93ER54186; FA9550-15-1-0058
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 23; Journal Issue: 8; Journal ID: ISSN 1070-664X
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; microwave breakdown; gas discharges; radiofrequency discharges; plasma diagnostics; microwave sources; visible light; microwave spectroscopy; electric fields; density measurement

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., 2016. Web. doi:10.1063/1.4959171.
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. https://doi.org/10.1063/1.4959171
Schaub, S. C., Hummelt, J. S., Guss, W. C., Shapiro, M. A., and Temkin, R. J. 2016. "Electron density and gas density measurements in a millimeter-wave discharge". United States. https://doi.org/10.1063/1.4959171. https://www.osti.gov/servlets/purl/1467854.
@article{osti_1467854,
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 = {Here, 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 μs long at 110 GHz and 2.2 μs 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, where the collisional plasma frequency is equal to the microwave frequency, 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 structure and temporal dynamics of gas heating at atmospheric pressure were found to agree well with published numerical simulations.},
doi = {10.1063/1.4959171},
url = {https://www.osti.gov/biblio/1467854}, journal = {Physics of Plasmas},
issn = {1070-664X},
number = 8,
volume = 23,
place = {United States},
year = {Tue Aug 09 00:00:00 EDT 2016},
month = {Tue Aug 09 00:00:00 EDT 2016}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record

Citation Metrics:
Cited by: 31 works
Citation information provided by
Web of Science

Save / Share:

Works referenced in this record:

Pattern formation and propagation during microwave breakdown
journal, December 2010


Optical diagnostics of atmospheric pressure air plasmas
journal, February 2003


Iterative method for computing the inverse Abel transform
journal, March 1987


Hydrogen Balmer lines for low electron number density plasma diagnostics
journal, October 2012


Computational Studies of Filamentary Pattern Formation in a High Power Microwave Breakdown Generated Air Plasma
journal, September 2010


Experimental Results for a Pulsed 110/124.5-GHz Megawatt Gyrotron
journal, May 2014


New plasma diagnosis tables of hydrogen Stark broadening including ion dynamics
journal, October 1996


Study of a Stationary Breakdown Wave Under the Conditions of Noticeable Reflection of the Incident Electromagnetic Wave from a Gas-Discharge Plasma
journal, October 2015


Observation of Large Arrays of Plasma Filaments in Air Breakdown by 1.5-MW 110-GHz Gyrotron Pulses
journal, January 2008


Ionization–diffusion plasma front propagation in a microwave field
journal, April 2011


Plasma generation using high-power millimeter-wave beam and its application for thrust generation
journal, January 2006


Accurate Atomic Transition Probabilities for Hydrogen, Helium, and Lithium
journal, September 2009


Modeling study on pressure dependence of plasma structure and formation in 110 GHz microwave air breakdown
journal, April 2011


Spectroscopic temperature measurements of air breakdown plasma using a 110 GHz megawatt gyrotron beam
journal, December 2012


Features of plasma glow in low pressure terahertz gas discharge
journal, December 2013


Plasma structures observed in gas breakdown using a 1.5 MW, 110 GHz pulsed gyrotron
journal, May 2009


Theory and Modeling of Self-Organization and Propagation of Filamentary Plasma Arrays in Microwave Breakdown at Atmospheric Pressure
journal, January 2010


Pressure dependence of plasma structure in microwave gas breakdown at 110 GHz
journal, July 2010


Theory of Filamentary Plasma Array Formation in Microwave Breakdown at Near-Atmospheric Pressure
journal, July 2009


A one-dimensional study of the evolution of the microwave breakdown in air
journal, September 2015


Dynamics of a nonequilibrium discharge in a converging cylindrical wave under the condition of intensive gas heating
journal, February 1992


Gas heating effects on the formation and propagation of a microwave streamer in air
journal, September 2015


Two-dimensional continuous wavelet transform for phase determination of complex interferograms
journal, January 2011


Observation of plasma array dynamics in 110 GHz millimeter-wave air breakdown
journal, October 2011


Millimeter wave scattering and diffraction in 110 GHz air breakdown plasma
journal, April 2013


Spatial carrier fringe pattern demodulation by use of a two-dimensional continuous wavelet transform
journal, January 2006


Refractivity of combustion gases
journal, January 1981


Gas discharge physics
journal, August 1993


Works referencing / citing this record:

Plasma fluid modeling of microwave streamers: Approximations and accuracy
journal, November 2017


Effects of pressure and incident field on visible light intensity from microwave nitrogen breakdown
journal, February 2018


Numerical analysis of plasma structure observed in atmospheric millimeter-wave discharge at under-critical intensity
journal, July 2018


Electron density measurement of a lightning stepped leader by oxygen spectral lines
journal, August 2018


Discharge from a high-intensity millimeter wave beam and its application to propulsion
journal, January 2018


Physics and application of gas discharge in millimeter wave beams
journal, October 2018


Space and time evolution of light emitted from microwave nitrogen breakdown
journal, August 2019