This article outlines the main results of a research and development cooperation between Philips Research Eindhoven; Peter the Great St. Petersburg Polytechnic University; Ioffe Institute, St. Petersburg; Utrecht University; and Philips Healthcare. It reviews the properties of garnet ceramics in the (Lu,Gd)3(Ga,Al)5O12:Ce system for medical imaging, especially time-of-flight positron emission tomography (PET). Thermally stimulated luminescence (TSL) peaks are attributed to impurities, verified by intentional codoping of samples. A lately developed method allows extraction of carrier lifetimes, thermal trap depths, and frequency factors from TSL and afterglow measurements. A detailed analysis reveals the presence of a distribution of trap depths, allowing a more accurate afterglow modeling. Activation energies of thermal ionization and trap depths obtained from TSL show the influence of Ga/Al substitution on thermal quenching and on trap position. The resulting nonmonotonic dependence of the conduction band edge with Ga content in (Lu,Gd) garnets is consistent with earlier predictions. Shallow traps determine both signal decay and short-term afterglow. The impact of signal height, rise, and decay times on coincidence resolving time and further on PET image quality is described by analytical models.

中文翻译：

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透明石榴石闪烁体陶瓷中的带隙变化和陷阱分布

本文概述了飞利浦研究院埃因霍温研究与开发合作的主要成果；彼得大帝圣彼得堡理工大学；圣彼得堡约夫研究所；乌得勒支大学；和飞利浦医疗保健。它回顾了石榴石陶瓷在用于医学成像，尤其是飞行时间正电子发射断层扫描 (PET) 的 (Lu,Gd)3(Ga,Al)5O12:Ce 系统中的特性。热激发发光 (TSL) 峰归因于杂质，通过样品的有意共掺杂进行验证。最近开发的一种方法允许从 TSL 和余辉测量中提取载流子寿命、热阱深度和频率因子。详细分析揭示了陷阱深度分布的存在，从而可以进行更准确的余辉建模。从 TSL 获得的热电离活化能和陷阱深度显示了 Ga/Al 替代对热淬火和陷阱位置的影响。由此产生的导带边缘与 (Lu,Gd) 石榴石中 Ga 含量的非单调相关性与早先的预测一致。浅陷阱决定了信号衰减和短期余辉。分析模型描述了信号高度、上升和衰减时间对重合解析时间以及进一步对 PET 图像质量的影响。