Application of structured illumination to gas phase thermometry using thermographic phosphor particles: a study for averaged imaging

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title = "Application of structured illumination to gas phase thermometry using thermographic phosphor particles: a study for averaged imaging",
abstract = "Structured laser illumination planar imaging (SLIPI) is combined with gas phase thermometry measurements using thermographic phosphor (TGP) particles. The technique is applied to a heated jet surrounded by a coflow which is operated at ambient temperature. The respective air flows are seeded with a powder of BaMgAl10O17:Eu2+ (BAM) which is used as temperature-sensitive gas phase tracer. Upon pulsed excitation in the ultraviolet spectral range, the temperature is extracted based on the two-color ratio method combined with SLIPI. The main advantage of applying the SLIPI approach to phosphor thermometry is the reduction of particle-to-particle multiple light scattering and diffuse wall reflections, yielding a more robust calibration procedure as well as improving the measurement accuracy, precision, and sensitivity. For demonstration, this paper focuses on sample-averaged measurements of temperature fields in a jet-in-coflow configuration. Using the conventional approach, which in contrast to SLIPI is based on imaging with an unmodulated laser light sheet, we show that for the present setup typically ~40{\%} of the recorded signal is affected by the contribution of multiply scattered photons. At locations close to walls even up to 75{\%} of the apparent signal is due to diffuse reflection and wall luminescence of BAM sticking at the surface. Those contributions lead to erroneous temperature fields. Using SLIPI, an unbiased two-color ratio field is recovered allowing for two-dimensional mean temperature reconstructions which exhibit a more realistic physical behavior. This is in contrast to results deduced by the conventional approach. Furthermore, using the SLIPI approach it is shown that the temperature sensitivity is enhanced by a factor of up to ~2 at ~270 °C. Finally, an outlook towards instantaneous SLIPI phosphorescence thermometry is provided.",
author = "Florian Zentgraf and Michael Stephan and Edouard Berrocal and Barbara Albert and Benjamin B{\"o}hm and Andreas Dreizler",
year = "2017",
month = "7",
day = "1",
doi = "10.1007/s00348-017-2364-4",
language = "English",
volume = "58",
journal = "Experiments in Fluids",
issn = "1432-1114",
publisher = "Springer",
number = "7",