IN SITU MEASUREMENT OF THICKNESS AND OTHER PROPERTIES OF CARBON DIOXIDE CRYODEPOSITS BY OPTICAL TECHNIQUES
Technical rept. 1 Jan-31 Jul 1967
ARNOLD ENGINEERING DEVELOPMENT CENTER ARNOLD AFB TN
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Measurements of interference patterns in filtered light reflected from thin 77K CO2 cryodeposits are reported. Analysis indicated that these patterns are a result of interference between light rays scattered by reflection from the cryodeposit surface with rays which are scattered by passage through the surface and specularly reflected by the substrate. A simple light scattering model for cryodeposits is proposed which allows accurate determination of the deposit thickness from the interference patterns. Application of the scattering theory required knowledge of the refractive index of the cryodeposit. Consequently, the index of refraction for CO2 cryodeposits was determined from separate Bragg interference tests at wavelengths from 0.6 to 1.0 micron. Cryodeposit thicknesses up to 100 microns were determined from the scattering model equation. Utilizing mass conservation principles, the thickness calculations were further used to determine the mean cryodeposit density. A few scattering interference tests on other types of cryodeposits are also briefly reported.
- Test Facilities, Equipment and Methods