Brillouin scattering from a gas subject to a temperature gradient : optical considerations

Choo, Chin Heng (1996) Brillouin scattering from a gas subject to a temperature gradient : optical considerations. Masters thesis, Memorial University of Newfoundland.

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    Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission.
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Abstract

This thesis describes an attempt to use the Brillouin light scattering technique to observe nonequilibrium effects in gaseous sulphur hexafluoride subject to a temperature gradient. Due to the inherent geometry of the experimental setup, an imaging fibre optic probe was investigated as a means of scattered light collection. The SF₆ gas was housed in a moderate pressure gas cell. The scattered light collected was analyzed with a Fabry-Perot interferometer. A computer simulation of the behaviour of temperature, density and refractive index for gaseous SF₆ subject to a temperature gradient was performed using a 2 dimensional nonconvective heat flow model. A computer simulation of the scattered ray paths from the gas cell to the optical fibre in the imaging fibre optic probe was also performed. The sound speed in SF₆ at a pressure of 1.28 MPa and a temperature of 20°C was measured to be 133 ± 6 m.s⁻¹. Sound speeds in SF₆ for pressures from 0.44 MPa to 1.83 MPa were also measured. These sound speeds showed a larger nonlinearity in its changed with different pressures than that calculated from theory. Nonequilibrium Brillouin spectra for SF₆ were observed at pressures of 0.891 MPa and 1.35 MPa with temperature gradients of about 15.3 K cm⁻¹ and 18.9 K cm⁻¹, respectively. The Brillouin components at nonequilibrium showed an intensity increase of about 16% when compared to their counterparts at equilibrium.

Item Type: Thesis (Masters)
URI: http://research.library.mun.ca/id/eprint/5792
Item ID: 5792
Additional Information: Bibliography: leaves 71-73.
Department(s): Science, Faculty of > Physics and Physical Oceanography
Date: 1996
Date Type: Submission
Library of Congress Subject Heading: Brillouin scattering; Nonequilibrium thermodynamics; Sulphur hexafluoride--Optical properties

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