19 March 2014 Reflection properties of scintillator-septum candidates for a pixelated MeV detector
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Abstract
In order to predict and improve the performance of pixelated detectors, it is important to understand the optical properties of the basic unit of the scintillating structure in the detector. To measure one of the essential optical properties, reflectance, we have used a device composed of a laser and photodiode array. We have also developed an analytical model of the optical phenomena based on Snell's law and the Fresnel equations to simply analyze measured results and reflectance parameters at the interface. The computed and experimentally measured results typically have good agreement, validating the analytical model and measurements. The optical parameters are used as inputs to GEANT4 [1]. The simulations are then leveraged to optimize an imager design before a prototype is built. The optical reflectance was measured by using relatively inexpensive samples. A sample has scintillator, glue, and septum (reflector) layers, and each sample has a different scintillator surface (polished/rough) and/or reflector [ESR film/aluminum-sputtered (coated) ESR film] condition. A high-refractive-index hemisphere was attached on the top surface of a sample to increase the maximum incidence angle at the scintillator-glue interface from 27° to 52°. The sample including ESR film demonstrated average reflectance approximately 1.3 times higher than that from the sample with aluminum-sputtered ESR film as a reflector, and the polished surface condition showed higher reflectance than the rough-cut surface condition.
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Mihye Shin, Josh Star-Lack, Martin Janecek, Eric Abel, Daniel Shedlock, Rebecca Fahrig, "Reflection properties of scintillator-septum candidates for a pixelated MeV detector", Proc. SPIE 9033, Medical Imaging 2014: Physics of Medical Imaging, 90331H (19 March 2014); doi: 10.1117/12.2043281; https://doi.org/10.1117/12.2043281
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