W0108

In-situ X-Ray Diffraction Studies of Lu₂SiO₅ Crystals for PET Scintillation Detectors. S.A. Speakman¹, C.R. Hubbard¹, W.D. Porter¹, M.A. Spurrier², and C.L. Melcher², ¹Oak Ridge National Laboratory, Oak Ridge TN, ²CTI Molecular Imaging, Inc., Knoxville TN.

Lu₂SiO₅ single crystals are used to make highly efficient scintillation detectors for PET scanners used to diagnose cancer, heart disease, and neurological disorders such as Alzheimer's disease. As grown, Lu₂SiO₅ crystals can have variations in the light output that affects their efficacy in scintillation detectors. Annealing of the crystals can also have significant impact on the light output. In-situ X-ray powder diffraction, differential scanning calorimetry, dilatometry, and single crystal synchrotron diffraction were used to study Lu₂SiO₅ samples in order to understand factors contributing to these variations. In-situ XRD has been used to determine thermal expansion coefficients and phase transformations that might affect the crystal when cooling from the melt at 2040 °C. Additionally, thermal expansion coefficients provide some insight into differences between crystals with high and low light output. The loss of silicon in oxygen-deficient atmospheres has also been probed using in-situ XRD. Such losses affect phase stability during crystal growth and annealing. Single crystal diffraction at the X14A beamline at NSLS has been used to explore twinning and other crystalline defects in the Lu₂SiO₅ crystals. This presentation will summarize these data, along with crystal structure analyses, and their implications in understanding the factors affecting light output in Lu₂SiO₅ crystals.

Research sponsored by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of FreedomCAR and Vehicle Technologies, as part of the High Temperature Materials Laboratory User Program, Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract number DE-AC05-00OR22725.