Directional Assessment of Radiation Sources

尽管辐射是一种自然现象，但人们普遍认为它对人类和整个环境是危险的。辐射源可以是天然的，例如由于当地地质、用于建造房屋的建筑材料或宇宙辐射，或者是人工的，如核电站产生的辐射或医疗程序中使用的辐射。辐射的威胁可分为两类-由于过度暴露于电离辐射而造成的直接身体伤害和由于处于未知辐射环境中而造成的压力而对健康造成的有害影响。关于后者，值得一提的是犯罪活动，例如脏弹或无主放射性材料所构成的潜在威胁，在所有这些情况下，迅速和可靠地确定辐射源的位置和识别，并对辐射场及其相关风险进行评估，可大大有助于减轻上述有害影响，或者通过提供正确的信息，或者通过指导对辐射威胁的应急和应急后响应。后一种情况的一个恰当例子是对日本在福岛事故后的补救工作进行评估，拟议的传感器将提供一个紧凑、低功率的系统，供地面使用。它将易于携带，例如放在背包中，并直接和真实的评估辐射场的同位素组成和方向性。更基本的系统已经在背包、车载测量或轻型无人机中使用，但关键是缺乏拟议技术增加的方向灵敏度。拟议的目标是通过结合医学成像中常用的高密度无机闪烁晶体，结合紧凑的，基于硅的高度分段的光子传感器系统，直到最近技术才足够成熟，可以考虑用于这些应用。

Radiation, despite being a natural phenomenon, is widely regarded as dangerous to the human population and the environment in general. Radiation sources can be natural, e.g. due to the local geology, building material used in the construction of housing or cosmic radiation, or artificial like the radiation generated by nuclear power plants or employed in medical procedures. A threat from radiation can be classified twofold - the direct physical harm due to over-exposure to ionising radiation and the detrimental health effect due to stress of being in an unknown radiation environment. Related to the latter, it is worth mentioning the latent threat posed by criminal activity, e.g. dirty bombs or orphaned radioactive materials.In all these cases, a rapid and reliable location and identification of the radiation sources and an evaluation of the radiation field and its associated risks can greatly help to mitigate the aforementioned detrimental effect, either by providing correct information of by guiding the emergency and post-emergency response to a radiation threat. A case in point for the latter would be the evaluation of remediation efforts in Japan in the aftermath of the Fukushima accident.The proposed sensor will provide a compact, low-power system to be employed on the ground. It will be easily transportable, e.g. in a backpack and assess the isotopic composition and directionality of a radiation field directly and in real time. More basic systems are already in use in backpacks, car-borne surveys or lightweight drones, but crucially lack the directional sensitivity the proposed technology adds.The proposed aims are achieved by a combination of a high-density inorganic scintillation crystals frequently used in medical imaging, combined with a compact, highly segmented photon sensor system based on silicon which only recently became technologically mature enough to be considered for these applications.