高光输出、快衰减 LYSO 晶体的闪烁余辉研究

With high light output, fast decay, good timing resolution and excellent radiation hardness LYSO crystal is considered to be one of the most promising scintillation materials for the next generation Calorimetry in High Energy Physics (HEP) experiments and Time-of-Flight PET (TOF-PET) machine. A commercial LYSO crystal, however, exhibits extremely high scintillation afterglow, which will lead to unwanted electronic noise. This noise will affect the performance of Calorimetry and the PET machine resulting in a relatively poor energy resolution (E.R.) of Calorimetry and imaging quality of PET machine. While most research works on LYSO crystal nowadays focusing on the crystal growth, improvement of light output and energy resolution, no study was found dedicated to suppress the afterglow in LYSO crystal. This work will focus on the study of scintillation afterglow in LYSO crystal by studying systematically the influence of the impurities, the crystal growth atmosphere as well as the volatile on the formation of defects. This project will also perform the properties of the defects and the correlation between the defects and the scintillation afterglow. By doing so, we will try to figure out the main cause of the scintillation afterglow in LYSO crystal. This work will then study the interaction between the defects and the scintillation afterglow as well as the energy transfer route of the afterglow in LYSO crystals to unveil the origin of the scintillation afterglow and its mechanism. All these efforts will enrich the knowledge of scintillation materials and help to develop high quality LYSO scintillation crystal with low scintillation afterglow for future HEP experiments and Medical Imaging.

硅酸钇镥（LYSO）闪烁晶体的光输出高、衰减快，具有良好的时间分辨率和辐照硬度，是下一代高能物理实验高亮度量能器和新一代时间飞行PET（Time-of-Flight PET, TOF－PET）的首选闪烁材料之一。但目前商品化LYSO晶体的闪烁余辉很强，较强的余辉将导致用LYSO作为闪烁材料制造的探头的噪声较高，影响量能器性能的进一步提高；也会影响PET机的成像质量。目前，对LYSO的研究主要集中在晶体生长、光输出和能量分辨率的提高上，已有的报导均未对其闪烁余辉作系统的研究。本研究将系统地从晶体中的杂质离子、生长气氛、组分挥发等方面入手，通过缺陷的形成与缺陷性质研究、缺陷与余辉相关性研究查明影响LYSO晶体余辉的主导因素；通过余辉形成的物理机制研究，阐明导致LYSO闪烁余辉的本质原因，为开发高性能、低余辉的LYSO晶体奠定研究基础。

硅酸钇镥（LYSO）闪烁晶体的光输出高、衰减快，具有良好的时间分辨率和辐照硬度，是下一代高能物理实验高亮度量能器和新一代时间飞行PET（Time-of-Flight PET, TOF－PET）的首选闪烁材料之一。但目前商品化LYSO晶体的闪烁余辉很强，较强的余辉将导致以LYSO作为闪烁材料制造的探头的噪声较高，影响量能器性能的进一步提高；也会影响PET机的成像质量。目前，对LYSO的研究主要集中在晶体生长和光输出的提高上，已有的报导均未对其闪烁余辉作系统的研究。本研究将系统地从晶体中的杂质离子、生长气氛、组分挥发等方面入手，通过缺陷的形成与缺陷性质研究、缺陷与余辉相关性研究查明影响LYSO晶体余辉的主导因素；通过余辉形成的物理机制研究，阐明导致LYSO闪烁余辉的本质原因，为开发低余辉的LYSO晶体奠定研究基础。