SEARCH FOR ULTRA FAST, HEAVY ATOM SCINTILLATORS

描述（来自申请人摘要的逐字描述）： 研究的重点是开发具有快速发光的新型发光器。 关于光衰，和高原子序数，密度，和光度。这些 性能将提高检测效率，死区时间，空间 分辨率、正电子断层扫描的散射和随机排斥。的时序 +100 ps的分辨率将使有效灵敏度增加一个系数， 六个用于人脑和胸腔的图像，并允许逐个事件切片 3D断层扫描中的确定。低成本闪烁体的研制 这些性质将提高PET在医疗领域的可用性和准确性， 在世界各地的研究。 实验和计算工作的快速，明亮的闪烁体氧化锌：镓 使我们了解了它的激发和发射机制，并提出了 本发明的目的是在对PET具有良好阻止能力的晶体中实现它们。一 第二个目标是鉴定重原子晶体， Ce ~（3+）活化的良好基质。 为了实现这些目标，我们将继续改进我们的方法， 利用嵌入的分子轨道簇和电子能带结构 模拟发光机制的计算，并将其首先应用于 已知的替代品，然后到未开发的材料，以指导选择 用于合成和实验测量的候选物。的处理 模拟包括（1）施主电子，空穴， 和激子，（2）晶格弛豫，（3）基态和激发态 杂质原子;（4）热猝灭。候选材料将是 以粉末形式合成并使用我们的脉冲X射线系统进行测试。

DESCRIPTION (Verbatim from Applicant's Abstract): The objective of this research is the development of new scintillators with very rapid lum aboutnescence decay, and high atomic number, density, and luminosity. These properties would improve the detection efficiency, deadtime, spatial resolution, and scatter and randoms rejection of positron tomographs. A timing resolution of +100 ps would increase the effective sensitivity by a factor of six for images of the human brain and thorax, and allow event-by-event slice determination in 3D tomography. Development of a low-cost scintillator with these properties would improve the availability and accuracy of PET for medical studies throughout the world. Experimental and computational work on the fast, bright scintillator ZnO:Ga has led us to understand its excitation and emission mechanisms and to propose the objective of achieving them in a crystal with good stopping power for PET. A second objective is the identification of heavy-atom crystals that would be good hosts for Ce3+ activation. To accomplish these objectives, we will continue to improve our methods for using embedded molecular orbital cluster and electronic band structure calculations for simulating luminescence mechanisms, and apply them first to known scintillators, and then to unexplored materials to guide the selection of candidates for synthesis and experimental measurement. Processes to be simulated include (1 ) the formation and transport of donor electrons, holes, and excitons, (2) lattice relaxation, (3) the ground and excited states of impurity atoms, and (4) thermal quenching. Candidate materials will be synthesized as powders and tested using our pulsed x-ray system.