Prediction and measurement of electron density and collision frequency in a weakly ionised pine fire

Mphale, Kgakgamatso, Jacob, Mohan, and Heron, Mal (2007) Prediction and measurement of electron density and collision frequency in a weakly ionised pine fire. Journal of Infrared, Millimeter and Terahertz Waves, 28 (3). pp. 251-262.

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Abstract

Pine litter flame is a weakly ionised medium. Electron-neutral collisions are a dominant form of particle interaction in the flame. Assuming flame electrons to be in thermal equilibrium with neutrals and average electron-neutral collision frequency to be much higher than the plasma frequency, the propagation of microwaves through the flame is predicted to suffer signal intensity loss. A controlled fire burner was constructed where various natural vegetation species could be used as fuel. The burner was equipped with thermocouples and used as a cavity for microwaves with a laboratory quality network analyzer to measure wave attenuation. Electron density and collision frequency were then calculated from the measured attenuation. The parameters are important for numerical prediction of electromagnetic wave propagation in wildfire environments. A controlled pine litter fire with a maximum flame temperature of 1080 K was set in the burner and microwaves (8–10.5 GHz) were caused to propagate through the flame. A microwave signal loss of 1.6–5.8 dB was measured within the frequency range. Based on the measured attenuation, electron density and electron-neutral collision frequency in pine fire were calculated to range from 0.51–1.35 × 1016 m−3 and 3.43–5.97 × 1010 s−1 respectively.

Item ID: 2655
Item Type: Article (Refereed Research - C1)
Keywords: wildfire; microwave attenuation; microwave characterisation; weakly ionised gas; chemi-ionisation; thermal ionization; pine fire; electron density
ISSN: 1866-6906
Date Deposited: 07 May 2009 03:20
FoR Codes: 09 ENGINEERING > 0912 Materials Engineering > 091208 Organic Semiconductors @ 100%
SEO Codes: 82 PLANT PRODUCTION AND PLANT PRIMARY PRODUCTS > 8299 Other Plant Production and Plant Primary Products > 829999 Plant Production and Plant Primary Products not elsewhere classified @ 70%
86 MANUFACTURING > 8616 Computer Hardware and Electronic Equipment > 861603 Integrated Circuits and Devices @ 20%
87 CONSTRUCTION > 8799 Other Construction > 879999 Construction not elsewhere classified @ 10%
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