Directional Assessment of Radiation Sources

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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.