LYSO晶体光响应均匀性的研究

Excellent radiation hardness and good light response uniformity(LRU) are two essential parameters for large size inorganic scintillation crystals in High energy physics (HEP) experiments. Cerium activated LYSO crystal(LYSO:Ce) is considered to be most suitable scintillation materials for HL-LHC and SuperB experiment because of its superior scintillation properties and good radiation hardness. The LRU of large size LYSO, however, needs further improvement to meet the requirement of HEP experiments. This work will focus on the correlation between the scintillation properties and Ce concentration, self-absorption and defects in LYSO crystals. By doing so, we will try to figure out the main factors which affect the LRU. Meanwhile, this will result in the development of an effective method in measuring Ce concentration in LYSO crystal without destroying the sample itself. All these efforts will enrich the knowledge of scintillation materials and help develop high quality LYSO scintillation crystals for future HEP experiments and Medical Imaging.

高能物理用大尺寸闪烁晶体需要有良好的抗辐照损伤能力和光响应均匀性。铈掺杂LYSO晶体具有优良的闪烁性能和极高的抗辐照损伤能力，被认为是HL-LHC实验的CMS量能器和SuperB实验的首选闪烁材料。但大尺寸LYSO晶体的光响应均匀性一直未得到很好的解决，本研究拟从铈离子浓度、晶体的自吸收效应、缺陷等对晶体闪烁性能的影响入手，查明影响晶体光响应均匀性的主要因素，进而改善晶体生长工艺，为开发良好光响应均匀性的大尺寸LYSO晶体奠定基础。并提出一种方便快捷、非破坏性的红外吸收法测定晶体的Ce离子浓度的方法。

摘要..本项目针对影响LYSO光相应均匀性的因素开展了系统研究：成功制备了铈掺杂浓度的系列LYSO样品：铈浓度为0%，0.05%，0.1%，0.15%，0.175%，0.25%，0.35%，0.5%晶体。对铈离子f-f跃迁光吸收谱进行了系列研究，确定2194.6 cm-1相关吸收峰为标记峰。通过纯LYSO晶体的本底扣除，建立了吸收与铈浓度的线性关系，该线性关系可用于LYSO中铈离子的非破坏测量。系统研究了LYSO中铈的分凝系数，获得了不同工艺条件下分凝系数的规律。建立了铈浓度与光输出的关系，确定了提拉法生长LYSO中铈的优化浓度为150－400ppmw。