Collaborative Research: ARI-MA: Realizing high performance inorganic scintillators at low cost

合作研究：ARI-MA：以低成本实现高性能无机闪烁体

• 批准号: 1348139
• 负责人: Arnold Burger
• 金额: $ 13万
• 依托单位: Fisk University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-10-01 至 2015-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1348139&HistoricalAwards=false
• 关键词: Collaborative; Research; ARI; MA; Realizing

1348361 (Williams), 1348139 (Burger), and 1348341 (Biswas). The Global Nuclear Detection Architecture (GNDA) is intended to detect illicit and unregulated nuclear and radiological materials worldwide. Wide deployment calls for quick and accurate detection technology with sensitivity and resolution close to current state-of-the-art scintillators but at much lower cost. The basic premise of this approach is that there are already inorganic scintillators with light yield and proportionality close to the limits that can be achieved in their ~5 eV band gap range; and that this group haswe developed a predictive model that describes why there is a sweet spot of material parameters defining the current group of highest performance scintillators. This is used to narrow the scope of theoretical, crystal-growth, and evaluative searches in this project so that they can be targeted farther into ternary and quaternary compositions and at the same time deeper into parameters that affect cost and performance. Some of the best new scintillator hosts are in fact composed of abundant (cheap) elements. The reason for their current high cost is not materials, but low yield of growing large single crystals. This project will pursue four research avenues to solve or side-step the crystal growth problems on the way to realizing an economical detector from materials in the sweet spot of structures, compositions, and physical parameters identified from the design rules developed by Wake Forest, Fisk, LBNL, and others since about 2010. One of the approaches to reduce cost examines how to improve the proportionality of segmented index-matched assemblies of smaller crystal blocks that are difficult to grow in large sizes. Such segmented detectors combined with wavelength shifting also provide flexibility to deal with self-absorption (photon diffusion) that currently limits the size of SrI2:Eu detectors. The group will measure and model how the peripheries of blocks in segmented scintillators contribute to nonproportionality, and what can be done to improve it. One ultra-lowcost but high-risk possibility involves index-matched granular scintillators using pre-doped SrI2:Eu beads supplied in bulk by chemical manufacturers. Starting with an excellent scintillator like SrI2:Eu, guided by experience with the segmented scintillators and their modeling, and applying thermal and chemical processing to the beaded material, the group will investigate the physics of what limits the resolution of granular detectors and how to advance performance beyond prior index-matched granular scintillators. A third approach to cost reduction will raise the yield of crystal growth by hardening and toughening existing excellent scintillators while taking care that the hardening measures do not degrade proportionality and light yield. A fourth targets theoretical and experimental searches toward new ternary and quaternary crystals with cubic structures and other properties favoring large crystal growth as well as slow electron thermalization, poor hot electron mobility, good thermalized electron mobility, and low Auger rates leading to best proportionality and light yield. Three university teams bring to this quest their complementary expertise and facilities in (1) crystal growth and characterization, (2) ultrafast laser probes of scintillation and associated numerical modeling of transport, trapping, and nonlinear quenching, and (3) electronic structure calculations on candidate crystals, defects, and dopants. The intellectual merit lies in applying this complementary three university array of experimental and theoretical techniques guided by predictive physical models to attack the cost problem treated in terms of physical parameters alongside those determining proportionality and light yield in both gamma and neutron detectors. The results, positive or negative, will inform the whole field on the models and methods employed. The broader impacts will be to increase national and global security by making possible improved, affordable deployment of nuclear monitoring; increasing the pool of U.S. university graduates trained in the materials technologies necessary to build and deploy such systems widely; and instituting a 3- university bridge system of interacting undergraduate, M.S., and Ph.D. programs and opportunities among the participating universities in three southeastern states to provide a path into the nuclear detection workforce for under-represented and economically disadvantaged students.

1348361（威廉姆斯）、1348139（汉堡）和1348341（比斯瓦斯）。全球核探测架构旨在探测全世界非法和无管制的核材料和放射性材料。广泛部署需要快速准确的检测技术，其灵敏度和分辨率接近当前最先进的检测器，但成本要低得多。这种方法的基本前提是，已经有无机发光体的光产率和比例接近其~5 eV带隙范围内可以实现的极限;并且该小组已经开发了一个预测模型，该模型描述了为什么存在定义当前最高性能发光体组的材料参数的最佳点。这用于缩小本项目中理论、晶体生长和评估搜索的范围，以便它们可以进一步针对三元和四元组合物，同时更深入地研究影响成本和性能的参数。事实上，一些最好的新闪烁体主体是由丰富的（廉价的）元素组成的。其目前高成本的原因不是材料，而是生长大单晶的低产量。该项目将通过四种研究途径来解决或回避晶体生长问题，从而从维克森林、菲斯克、LBNL等自2010年以来开发的设计规则中确定的结构、成分和物理参数的最佳点材料中实现经济型探测器。降低成本的方法之一是研究如何提高难以大尺寸生长的较小晶体块的分段折射率匹配组件的比例。这种分段探测器与波长漂移相结合还提供了处理自吸收（光子扩散）的灵活性，而自吸收（光子扩散）目前限制了SrI 2：Eu探测器的尺寸。该小组将测量和建模如何在分段式蒸发器块的周边有助于非比例性，以及可以做些什么来改善它。一个超低成本，但高风险的可能性涉及指数匹配的颗粒蒸发器使用预掺杂的SrI 2：Eu珠由化学品制造商批量供应。从SrI 2：Eu这样的优秀闪烁体开始，以分段闪烁器及其建模的经验为指导，并将热处理和化学处理应用于珠状材料，该小组将研究限制颗粒探测器分辨率的物理学，以及如何提高性能，超越先前的指数匹配颗粒闪烁器。降低成本的第三种方法将通过硬化和韧化现有的优秀的晶体生长器来提高晶体生长的产率，同时注意硬化措施不会降低比例性和光产率。第四个目标的理论和实验研究新的三元和四元晶体的立方结构和其他属性有利于大晶体生长，以及缓慢的电子热化，热电子迁移率差，良好的热化电子迁移率，低俄歇率导致最佳的比例和光产量。三个大学团队带来了他们互补的专业知识和设施，（1）晶体生长和表征，（2）闪烁的超快激光探针和相关的传输，捕获和非线性淬火的数值模拟，以及（3）候选晶体，缺陷和掺杂剂的电子结构计算。智力上的优点在于应用这三个互补的大学阵列的实验和理论技术的预测物理模型的指导下攻击的成本问题处理的物理参数，以及那些确定的比例和光产额在伽马和中子探测器。研究结果，无论是正面的还是负面的，都将使整个领域了解所采用的模型和方法。更广泛的影响将是通过改进、负担得起的核监测部署来提高国家和全球安全;增加接受过广泛建立和部署此类系统所需材料技术培训的美国大学毕业生人数;建立一个由三所大学的本科生、硕士、博士和研究生组成的互动桥梁系统。和博士在东南部三个州的参与大学中提供方案和机会，为代表性不足和经济困难的学生提供进入核探测队伍的途径。