Dr. Kendall D. Hughey Profile

Dr. Kendall D. Hughey

at Pacific Northwest National Lab

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Author

Publications (4)

Proceedings Article | 14 June 2023 Presentation + Paper

Using synthetic infrared spectra derived from n/k optical constants for standoff detection of chemical deposits

Charmayne Lonergan, Jeremy Erickson, Molly Rose Kelly-Gorham, Oliva Primera-Pedrozo, Michael Wilhelm, Brenda Forland, Kendall Hughey, Bruce Bernacki, Timothy Johnson, Tanya Myers

Proceedings Volume 12541, 1254109 (2023) https://doi.org/10.1117/12.2663579

KEYWORDS: Reflectivity, Aluminum, Statistical analysis, Film thickness, Infrared radiation, Standoff detection, Coating thickness, Solids, Reflection, Infrared detectors

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We report results from a recent field experiment to test the validity of using physics-based synthetic infrared spectra to serve as endmembers in a spectral database targeted at chemical deposits. Specifically, the optical constants n and k, (the real and imaginary part of the refractive index) were used to first model infrared reflectance spectra for different thicknesses of chemical layers (e.g. acetaminophen, methylphosphonic acid – MPA, etc.) on various conducting and insulating substrates such as aluminum, wood, and glass. In the experimental portion of the research, thin films of the solid and liquid analytes were deposited onto such substrates to form micron-thick layers of the analytes at different thicknesses: Standoff data from an imaging instrument were then recorded and analyzed to not only identify the different analytes, but also quantify the layer/deposit thickness. To gauge success, the detection results using the synthetic data were compared to the results from laboratory hemispherical reflectance (HRF) spectra that were collected for the same sample planchets measured in the field via standoff methods. Preliminary results indicate good agreement between the synthetic reference data as compared to the lab-measured HRF data in terms of their ability to quantitatively reduce longwave infrared data. Specifically, modeled IR spectra for acetaminophen on an aluminum planchet at various thicknesses (1, 2, 5, 10, 15, and 20 μm) were synthesized and compared with standoff field reflectance data as well as HRF laboratory reflectance spectra for two samples: a 5.2 μm- and 12.8 μm-thick layer of acetaminophen on aluminum. Using a first-order approximation, analysis of the field data estimates the thicknesses of the samples to be 2 and 10 μm for the two samples, respectively, while the HRF laboratory data yields thickness estimates of between 5-10 μm and 10 μm, respectively. Both yield reasonable estimates, with the uncertainty most likely due to factors yet to be accounted for in the synthetic spectra such as light scattering.

Proceedings Article | 31 May 2022 Presentation + Paper

A hybrid FTIR/QCL sensing system for gas-phase kinetics using a long-path gas cell

Megan Dunlap, Kendall Hughey, Russell Tonkyn, Warren Harper, Tanya Myers, Timothy Johnson

Proceedings Volume 12098, 120980F (2022) https://doi.org/10.1117/12.2619856

KEYWORDS: Photolysis, Quantum cascade lasers, FT-IR spectroscopy, Absorption, Spectroscopy, Mirrors, Infrared spectroscopy, Absorbance, Infrared radiation, Spectral resolution

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Proceedings Article | 24 April 2020 Presentation + Paper

Quantitative far-infrared band strengths of iodine monochloride (ICl), a molten salt off-gas product

Kendall Hughey, Ashley Bradley, Heather Felmy, Andrew Clifford, Richard Cox, Amanda Lines, Samuel Bryan, Timothy Johnson

Proceedings Volume 11416, 114160Q (2020) https://doi.org/10.1117/12.2557555

KEYWORDS: Infrared radiation, Iodine, FT-IR spectroscopy, Absorbance, Infrared spectroscopy, Raman spectroscopy, Liquids, Molecules, Temperature metrology, Databases

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Proceedings Article | 24 April 2020 Presentation + Paper

Impact of pellet preparation on reflectance measurements of ammonium sulfate by single-angle reflectance spectroscopy for optical constants

E. Diaz, K. Hughey, A. Dohnalkova, T. Myers, T. Blake, S. Burton, T. Johnson

Proceedings Volume 11416, 1141604 (2020) https://doi.org/10.1117/12.2559989

KEYWORDS: Reflectivity, Particles, Reflectance spectroscopy, Scanning electron microscopy, Crystals, Reflection, Surface roughness, Solids, Specular reflections

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