Spectral and temperature-dependent infrared emissivity measurements of painted metals for improved temperature estimation during laser damage testing

Sean M. Baumann; Cameron Keenan; Michael A. Marciniak; Glen P. Perram

doi:10.1117/12.2068435

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31 October 2014 Spectral and temperature-dependent infrared emissivity measurements of painted metals for improved temperature estimation during laser damage testing

Sean M. Baumann, Cameron Keenan, Michael A. Marciniak, Glen P. Perram

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Proceedings Volume 9237, Laser-Induced Damage in Optical Materials: 2014; 923713 (2014) https://doi.org/10.1117/12.2068435
Event: SPIE Laser Damage, 2014, Boulder, Colorado, United States

Abstract

A database of spectral and temperature-dependent emissivities was created for painted Al-alloy laser-damage-testing targets for the purpose of improving the uncertainty to which temperature on the front and back target surfaces may be estimated during laser-damage testing. Previous temperature estimates had been made by fitting an assumed gray-body radiance curve to the calibrated spectral radiance data collected from the back surface using a Telops Imaging Fourier Transform Spectrometer (IFTS). In this work, temperature-dependent spectral emissivity measurements of the samples were made from room temperature to 500 °C using a Surface Optics Corp. SOC-100 Hemispherical Directional Reflectometer (HDR) with Nicolet FTS. Of particular interest was a high-temperature matte-black enamel paint used to coat the rear surfaces of the Al-alloy samples. The paint had been assumed to have a spectrally flat and temperatureinvariant emissivity. However, the data collected using the HDR showed both spectral variation and temperature dependence. The uncertainty in back-surface temperature estimation during laser-damage testing made using the measured emissivities was improved from greater than +10 °C to less than +5 °C for IFTS pixels away from the laser burn-through hole, where temperatures never exceeded those used in the SOC-100 HDR measurements. At beam center, where temperatures exceeded those used in the SOC-100 HDR, uncertainty in temperature estimates grew beyond those made assuming gray-body emissivity. Accurate temperature estimations during laser-damage testing are useful in informing a predictive model for future high-energy-laser weapon applications.

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Sean M. Baumann, Cameron Keenan, Michael A. Marciniak, and Glen P. Perram "Spectral and temperature-dependent infrared emissivity measurements of painted metals for improved temperature estimation during laser damage testing", Proc. SPIE 9237, Laser-Induced Damage in Optical Materials: 2014, 923713 (31 October 2014); https://doi.org/10.1117/12.2068435

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