Laser sustained argon plasmas in non-lte for beamed energy propulsion

David K. Zerkle, Ayhan E. Mertogul, Herman Krier, Jyoti Mazumder

Research output: Contribution to conferencePaper

Abstract

A 5 kW continuous wave laser sustained argon plasma is investigated using spatially resolved emission spectroscopy. The mass flttx incident on the plasma is 16.6 kg/m2s resulting in velocity of 10.2 m/s at one atmosphere. The CO2 laser wavelength is 10.6 microns and the focusing geometry is f/4. Absolute line intensity measurements are made for determining the upper level populations in neutral argon, and the Stark broadened profile of the hydrogen Baimer series alpha line is measured for determining electron number density. Comparisons are made between upper level excitation temperatures found from Boltzmann plots and absolute emission coefficient temperatures which require an assumption of local thermodynamic equilibrium (LTE). Electron number densities corresponding to the LTE based absolute emission coefficient temperatures are compared to the densities found from the Stark profiles method, which does not require LTE in the plasma to be valid. Non-LTE is indicated by large differences found between the results of the two electron number density methods. The Stark profiles method gave an electron number densities as high as 2.7 × 1017 cm-3 compared to 0.7 to 1.6 × 1017 cm-3 resulting from the LTE based Calculation. Differences between the measured excitation temperature and the temperature based on emission coefficients and LTE analysis were fairly striking, but several possible sources of error render those findings less conclusive concerning the persistence of non-LTE.

Original languageEnglish (US)
StatePublished - Jan 1 1991
EventAIAA 22nd Fluid Dynamics, Plasma Dynamics and Lasers Conference, 1991 - Honolulu, United States
Duration: Jun 24 1991Jun 26 1991

Other

OtherAIAA 22nd Fluid Dynamics, Plasma Dynamics and Lasers Conference, 1991
CountryUnited States
CityHonolulu
Period6/24/916/26/91

ASJC Scopus subject areas

  • Engineering (miscellaneous)
  • Aerospace Engineering
  • Electrical and Electronic Engineering
  • Condensed Matter Physics

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    Zerkle, D. K., Mertogul, A. E., Krier, H., & Mazumder, J. (1991). Laser sustained argon plasmas in non-lte for beamed energy propulsion. Paper presented at AIAA 22nd Fluid Dynamics, Plasma Dynamics and Lasers Conference, 1991, Honolulu, United States.