Determining Limits of Detection for Different Detector Geometries
through Monte Carlo based Simulations

The threat from nuclear terrorism represents a complex challenge for global governments. Although current systems for detecting threats from illicit materials exist, each have inherent limitations. However, it is crucial that a system can detect when material is being transported with malicious intent and where the potential damage caused by the distribution of such material is likely to require extensive cleanup operations. One monitoring approach comprises the use of a network(s) of distributed detectors in an attempt to detect anomalous events. Quantifying the limits of detection for these small-volume and portable systems is a challenging, but vital, task. Existing work in designing a threat reduction system has not shown a good understanding of what the system is capable of detecting. To rectify this issue, work has been undertaken to create a numerical simulation capable of modelling a moving detector and stationary source with a given distance of closest approach. The algorithm is then able to estimate limits on parameters where the source stops being detectable, by cycling through variables and completing numerous pseudo-experiments at each value. Such an approach will allow any proposed network to ascribe an estimate of the threats that it will be sensitive to. Supplementary work was completed to empirically verify the simulated results. These real-world tests provided confidence that the simulations approximate the physics modelled.