Advanced Scintillator Material for High Energy X-ray Imaging.

作为界面分析中心(IAC)、塞拉菲尔德(Sellafield)、贝尔法斯特女王大学(QUB)和STFC中央激光设备(CLF)之间的合作项目，这一总体项目旨在开发一种革命性的分析技术，特别侧重于监测核废料桶。通过在很短的时间内发射极高能量的激光，产生强烈的X射线辐射斑点并投射到探测器板上。与医用x射线类似，放置在明亮的x射线源和摄影胶片或数字图像板之间的任何对象都会被详细捕获。然而，由于使用了非常高的能源，所以对地球上密度最高的材料之一铀废料进行成像是可能的。自1952年以来，塞拉菲尔德一直负责英国所有核废料的安全储存和再处理。经过几十年的研究和开发，产生了更易管理的核废料形式。然而，仍然存在一系列问题，特别是自上世纪60年代S以来一直在储存的老化核废料。在考虑在地质处置设施中长期储存之前，需要确定废料和安全壳的成分和降解状态。由于储存过程中形成的放射性和危险的腐蚀产物，对废旧集装箱进行破坏性调查被认为太危险了。因此，建议对容器进行无损评估。为了对废物进行目测，需要使用高能X射线来生成储存中的样品的图像。产生x射线的典型方法既不能达到鉴定腐蚀产物所需的分辨率，也不能达到穿透大型、稠密的废旧容器所需的能量。因此，有人建议利用中央激光设施(CLF)的火神激光器来产生分析所需的必要的高能X射线。这项具体的研究建议侧重于开发用于捕获核废料容器的X射线图像的检测方法。具体地说，我们的目标是部署一种新型的透明闪烁体(称为GLO元素的首字母缩写)，能够将高能X射线转换为可见光进行成像。我们所需要的高能X射线的关键特性是能够畅通无阻地穿过物体。然而，它们带来的优势也是为什么很难从它们那里收集图像的原因--它们太容易通过大多数探测器材料！因此，使用高密度、高原子序数的材料(这是GLO闪烁体)大大增加了X射线相互作用并转化为可见光光子的可能性。然后用微光的ccd摄像机捕捉到这些，提供集装箱内容物的图片。总体项目的最后阶段包括用能够每秒发射10次(或更多)的快速发射偶极激光取代单发火神激光。这一点与我们建议的新探测器布置相结合，将实现更好的图像采集，甚至可以在采集过程中旋转鼓的情况下进行3D断层成像(如医用CT扫描)。

The overarching project aims to develop a revolutionary analysis technique with a particular focus on monitoring of nuclear waste drums as a collaborative project between the Interface Analysis Center (IAC), Sellafield, Queen's University Belfast (QUB) and the STFC Central Laser Facility (CLF). By firing an extremely high-energy laser for a very short duration, an intense spot of x-ray radiation is generated and projected towards detector plates. In a similar manner to medical x-rays, any object placed between the bright source of x-rays and either photographic film, or digital image plates, is captured in detail. However, because a very high energy source is used, imaging of uranium waste, one of the densest materials on earth, is possible. Since 1952 Sellafield has been responsible for safe storage and reprocessing of all the UK's nuclear waste. Decades of research and development have resulted in more manageable forms of nuclear waste. However, a whole host of problems remain, particularly with the ageing nuclear waste that has been stockpiled since the 1960's. Before long term storage in a geological disposal facility is considered, the composition and degradation state of the waste material and containment vessel needs to be established. Due to the radioactivity and dangerous corrosion products formed during storage, a destructive investigation of the waste containers is considered too hazardous to be performed. Therefore, a non-destructive evaluation of the containers is proposed.For a visual inspection of the waste, high-energy x-rays are desired to create an image of the sample in storage. Typical means of producing x-rays do not achieve both the resolution required to identify corrosion products nor the energy needed to penetrate through the large, dense, waste containers. Therefore, it has been proposed that the Vulcan laser at the central laser facility (CLF) is utilised to generate the necessary high-energy x-rays required for this analysis. This particular research proposal focuses on the development of the detection methods used to capture the x-ray images of nuclear waste containers. Specifically, we aim to deploy a novel transparent scintillator (referred to as an acronym of its elemental constituents as GLO - gadolinium lutetium oxide) capable of converting the high-energy x-rays into visible light for imaging. The key property of the high-energy x-rays that we require is the ability to travel through objects unimpeded. However, the advantage they present is also the reason why it is difficult to collect an image from them - they pass through most detector materials too easily! Therefore, the use of a high density, high atomic number material (which is the GLO scintillator) greatly increases the probability that x-rays will interact and convert to visible light photons. These are then captured on low-light CCD cameras providing a picture of the container contents.The final stage of the overarching project involves replacing the single-shot Vulcan laser with a rapid-fire DiPOLE laser capable of 10 shots a second (or more). This, combined with our proposed new detector arrangement, will enable far better image acquisition and even 3D tomography (like a medical CT scan) if the drums are rotated during acquisition.