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Selection and Optimization of Radiation Detector Materials

辐射探测器材料的选择与优化

基本信息

批准号：
EP/E043151/1
负责人：
Robin Grimes
金额：
$ 12.28万
依托单位：
Imperial College London
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2007
资助国家：
英国
起止时间：
2007 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FE043151%2F1
关键词：
Selection Optimization Radiation Detector Materials

项目摘要

Threat reduction and nonproliferation activities urgently require improved radiation detectors. As such, it is vital that we move beyond the largely empirical approach of detector material discovery and optimization. We propose to integrate atomic scale computer simulation and experimental material science, to discover and optimize candidate scintillator detector material compositions. When appropriately coupled, these techniques will create a physics-based feedback loop, which will lead to an approach through which it is possible to optimize the energy resolution of candidate scintillators. Furthermore, this approach is independent of material type (system). Although single crystals are used here to determine scintillator properties, improvements in the understanding and control of defects can be incorporated into other material forms (e.g. nanophosphors or polycrystalline scintillators).While nonproliferation and security activities are beneficiaries of the proposed work, other activities will also directly benefit, such as high resolution radiography for passive evaluation of nuclear power installations. Furthermore, an active industrial market interested in detector development exists for applications such as oil well logging and medical imaging.The general requirements for detector materials are that they are dense (stopping power), bright (conversion of incident radiation energy to light output) and fast (quickly convert the incident energy to light output). While many current detector materials offer some of these properties (e.g. Tl doped NaI is bright and fast but not dense) there are families of compositions that offer improvements, in particular, rare earth oxides (which are much more dense) and halides (which are brighter).The majority of solid state systems for radiation detection require that the incident energy excites an electron that is initially associated with an activator ion embedded in a host lattice. Subsequently, the electron returns to the ground state and light is emitted (that can be detected electronically to produce a signal). This scintillation process depends crucially on the behaviour of the electron (and hole) and hence on the local environment of the activator ion in the crystal as well as the propensity for electrons or holes to become trapped at other defect sites in the lattice. Here three series of host materials and activators will be investigated, as a function of their constituent chemical species, using atomic scale computer simulation and experimental techniques and the results correlated with observed detector efficiency. By predicting defect behaviour, the atomic scale simulations will identify compositional regions of potential significance. Subsequently the experimental work, single crystal growth, luminescence, site selective excitation and Raman spectroscopy, will focus on the specific compositions and determine their properties. This provides a test of the simulation approach in addition to a verification of the efficacy of the materials as luminescence based radiation detectors. The combined approach will allow for a vital, defect property-based optimization, where historically improvements have been empirical.

减少威胁和防扩散活动迫切需要改进辐射探测器。因此，我们必须超越探测器材料发现和优化的主要经验方法。我们建议结合原子尺度的计算机模拟和实验材料科学，发现和优化候选闪烁体探测器材料成分。当适当地耦合时，这些技术将创建基于物理的反馈回路，这将导致一种方法，通过该方法可以优化候选发射器的能量分辨率。此外，这种方法与材料类型（系统）无关。虽然这里使用单晶体来确定闪烁体的特性，但可以将对缺陷的理解和控制的改进纳入其他材料形式（例如纳米磷光体或多晶闪烁体）。虽然不扩散和安全活动是拟议工作的受益者，但其他活动也将直接受益，例如用于核动力装置被动评估的高分辨率射线照相术。此外，在石油测井和医学成像等应用领域，对探测器开发感兴趣的工业市场也很活跃。探测器材料的一般要求是致密（阻止能力）、明亮（将入射辐射能量转换为光输出）和快速（快速将入射能量转换为光输出）。虽然许多当前的探测器材料提供了这些特性中的一些（例如，Tl掺杂的NaI是明亮和快速的，但不致密）存在提供改进的组合物家族，特别是，稀土氧化物（密度大得多）和卤化物（比较亮）用于辐射检测的大多数固态系统要求入射能量激发最初与活化剂离子相关联的电子。嵌入在主晶格中。随后，电子返回到基态，并发出光（可以通过电子检测来产生信号）。这种闪烁过程主要取决于电子（和空穴）的行为，因此取决于晶体中激活剂离子的局部环境以及电子或空穴被捕获在晶格中其他缺陷位置的倾向。在这里，三个系列的主机材料和活化剂将进行调查，作为其组成的化学物种的函数，使用原子尺度的计算机模拟和实验技术，并与所观察到的探测器效率的结果。通过预测缺陷行为，原子尺度模拟将确定潜在意义的成分区域。随后的实验工作，单晶生长，发光，位置选择性激发和拉曼光谱，将集中在特定的组合物，并确定其性能。除了验证材料作为基于发光的辐射探测器的功效之外，这还提供了模拟方法的测试。结合的方法将允许一个重要的，基于缺陷属性的优化，其中历史上的改进是经验性的。