Imaging and Detection of Radioactive Material - Portable Gamma Ray Imaging Spectrometer (PGRIS)

对英国的恐怖主义威胁有多种形式，通常缩写为CBRNE(化学、生物、辐射、核和爆炸)。该项目将生产一种先进类型的手持辐射探测器的原型，能够成像和精确的光谱分析，这与后三个领域相关。我们的设备可以精确地识别和定位发射伽马射线的放射性物质。我们的便携式伽马射线成像光谱仪将被用来追踪和表征触发通用门户扫描仪的辐射。辐射威胁来自有时被称为“脏弹”的东西，或者更广泛地说，来自任何释放放射性物质的方法，其方式对公众造成威胁。为了应对辐射威胁，有必要能够快速定位和识别放射性物质。此外，一旦发生脏弹爆炸，至关重要的是能够通过确定发射了什么辐射及其位置来监测影响。核威胁来自核武器扩散，在这种情况下，需要检测特殊的核材料(铀和钚)。我们的设备将能够探测和定位这些材料发出的微弱伽马射线。爆炸物不能被辐射探测器直接探测到，因为它们通常不发射伽马射线。然而，如果它们受到中子的轰击，它们就会被激活，并发出特征伽马射线，这使得它们能够被探测和识别。同样的技术也可以用来搜索非法药物。已经有了便携式辐射探测器，但通常这些探测器使用闪烁体来探测伽马辐射，因此能量分辨率有限，这意味着能量接近的伽马射线无法相互区分。另一种选择是使用锗作为探测器元件。在这种情况下，分辨率非常好，但探测器非常昂贵，只有当锗冷却到-200摄氏度左右时，它才能作为探测器运行良好。我们的探测器使用一种名为碲化锌镉(CZT)的半导体，它在室温下工作得很好。它的能量分辨率比闪烁体好得多，几乎和锗一样好。还有其他一些使用CZT探测器的便携式探测器，但没有一个将这种良好的光谱分辨率(通过其特征伽马射线能量来识别材料)与定位放射源的成像能力相结合。

Terrorist threats to the UK take many forms, often abbreviated to CBRNE (Chemical, Biological, Radiological, Nuclear and Explosive). This project will produce a prototype of an advanced type of hand-held radiation detector capable of imaging and accurate spectroscopy, which is relevant to the last three of these areas. Our device can identify precisely and locate radioactive materials that emit gamma rays. Our portable gamma-ray imaging spectrometer will be used to track down and characterise the radiation which has triggered a general purpose portal scanner.The radiological threat comes from what are sometimes called "dirty bombs" or more generally from any method used to release radioactive material in such a way as to cause a threat to the general public. In order to deal with the radiological threat it is necessary to be able to locate and identify radioactive materials quickly. In addition, in the event that a dirty bomb is exploded, it is vital to be able to monitor the effects by establishing what radiation was emitted and its location.The nuclear threat comes from nuclear weapons proliferation and in this case the need is to detect special nuclear materials (Uranium and Plutonium). Our device will be able to detect and locate the weak gamma rays emitted by these materials.Explosives cannot be detected directly by a radiation detector because they normally do not emit gamma rays. However, if they are bombarded by neutrons then they will be activated and will emit characteristic gamma rays, which enable them to be detected and identified. The same technique can be used to search for illegal drugs.There are already portable radiation detectors, but generally these use scintillators to detect gamma radiation and so the energy resolution is limited which means that gamma rays that are close in energy cannot be distinguished from each other. An alternative is to use Germanium for the detector element. In this case the resolution is very good, but the detector is very expensive and Germanium only operates well as a detector when it is cooled to temperatures around -200C. Our detector uses a semiconductor called Cadmium Zinc Telluride (CZT) which works well as a detector at room temperature. It has much better energy resolution that scintillators and is nearly as good as Germanium. There are a few other portable detectors using CZT detectors, but none which combine this good spectroscopic resolution (for identifying materials by their characteristic gamma-ray energy) with imaging capability to locate the sources of the radioactivity.