Optimising the neutron environment of Radiation Portal Monitors

辐射入口监测仪目前安装在港口和机场的交通阻塞点，很少考虑其运行环境。简单的分析表明，这些系统的中子成分的信噪比可以通过明智的屏蔽、准直和改变环境来改善，并且这些都可以在提高吞吐量的同时实现。本建议将提供这些改进的详细分析、量化和成本计算。除了rpm打算探测的威胁中子通量外，还有一个中子本底通量，主要是宇宙射线在大气、探测器下面的地面以及邻近的基础设施、车辆及其货物中引起反应的结果。该背景通量与预期威胁通量具有完全不同的方向分布，因此通过屏蔽和准直，可以显著减少背景计数，提高整体信噪比。这将直接导致威胁材料的最低可检测量的减少。或者，可以使用改进的统计数据在更短的时间内做出相同的诊断。

Radiation portal monitors (RPMs) are currently installed at traffic choke points at ports and airports with little regard to their operating environment. Simple analyses suggest that the signal-to-noise ratio of the neutron components of these systems can be improved by judicious shielding, collimation and modifications of the environment, and that these can be done while improving throughput. This proposal will provide a detailed analysis, quantification and costing of these improvements. In addition to the threat neutron flux which the RPMs are intended to detect, there is a background flux of neutrons, predominantly the result of cosmic ray induced reactions in the atmosphere, in the ground below the detectors and also in adjacent infrastructure, in vehicles and their cargos. This background flux has quite a different directional distribution to the expected threat flux, so by shielding and collimation, it is possible to significantly reduce the background counts, improving the overall signal-to-noise ratio. This will result directly in a reduction of the minimum detectable amounts of threat material. Alternatively, the improved statistics can be used to make the same diagnosis in reduced time.