Angular distribution of visible and near IR radiation reflected fromCO sub 2 cryodeposits

Abstract

The effect of CO2 cryodeposits on the angular distribution of visible and near IR radiation reflected from polished copper and black epoxy paint surfaces is investigated experimentally. It is found that the presence of CO2 cryodeposit on a surface causes the incident radiation to be reflected more diffusely. Also, off-specular peaks are observed in the directional distributions of reflected radiation, and the angular location of these peaks relative to the specular direction is found to be a function of deposit thickness and deposition rate as well as irradiation incidence angle. In addition, the experimental results indicate that CO2 cryodeposits scatter more in the backward direction than in the forward. Finally, patterns are seen in the angular distribution measurements for the cryodeposits formed on polished copper. These patterns are a result of interference generated by scattering at the vacuum-cryodeposit interface and they can be used to measure the thickness of thin layers of CO2 cryodeposit.