Light-sharing interface for dMiCE detectors using sub-surface laser engraving

• Published in: 2013 IEEE Nuclear Science Symposium and Medical Imaging Conference (2013 NSS/MIC) Vol. 2013; pp. 1 - 7
• Main Authors: Hunter, William C. J., Miyaoka, Robert S., MacDonald, Lawrence, McDougald, Wendy, Lewellen, Thomas K.
• Format: Conference Proceeding Journal Article
• Language: English
• Published: United States IEEE 01.10.2013
• Subjects: Calibration; Crystals; Detectors; Optical coupling; Optical films; Optical sensors; Photodetectors
• ISSN: 1082-3654; 1095-7863; 2577-0829
• DOI: 10.1109/NSSMIC.2013.6829407

We have previously reported on dMiCE, a method of resolving depth or interaction (DOI) in a pair of discrete crystals by encoding light sharing properties as a function of depth in the interface of this crystal-element pair. A challenge for this method is the cost and repeatability of interface treatment for a crystal pair. In this work, we report our preliminary results on using sub-surface laser engraving (SSLE) as a means of forming this depth-dependent interface in a dMiCE detector. A surplus first-generation SSLE system was used to create a partially reflective layer 100-microns thick at the boundary between two halves of a 1.4-by-2.9-by-20 mm^3 LYSO crystal. The boundary of these paired crystal elements was positioned between two 3-mm wide Geiger-Müller avalanche photodiodes from Hamamatsu. The responses of these two photodetectors were acquired for an ensemble of 511-keV photons collimated to interact at a fixed depth in just one crystal element. Interaction position was then varied to measure detector response as a function of depth, which was then used to maximum-likelihood positions events. Despite use of sub-optimal SSLE processing we found an average DOI resolution of 3.4 mm for front-sided readout and 3.9 mm for back-sided readout. We expect DOI resolution can be improved significantly by optimizing the SSLE process and pattern.