PNNL

Abstract

Searching for hidden illicit sources of gamma radiation in an urban environment is difficult. Background radiation profiles are highly variable and are cluttered with transient naturally occurring radioactive materials and medical isotope sources. Potentially threatening sources will likely be nearly hidden in this noice and will likely be encountered at high standoff distances and low threat count rates. We discuss an anomaly detection algorithm that characterizes low count sources as threatening or non-threatening and operates well in the presence of high benign source variability. We discuss the algorithm parameters needed to reliably find sources both close to the detector and far away from it. These parameters include the cutoff frequencies of background tracking filters and the integration time of the spectrometer. This work is part of the development of the SORIS Standoff Radiation Imaging System as part of DNDO's Standoff Radiation Detection System Advanced Technology Demonstration (SORDS-ATD) program.