An integrated system for gamma-ray spectral mapping and anomaly detection

For security, environmental, and regulatory purposes it is useful to monitor wide areas for unexpected changes in radioactivity. Background radiation from naturally radioactive materials presents the largest challenge to detection sensitivity. Most commonly, a single background spectrum is recorded and all subsequent spectra are compared to this static background. We have developed a temporal anomaly detection algorithm which uses multiple passes across an area to build a spatial map of background spectra, allowing increased sensitivity to anomalies. By comparing spectral shape rather than count rate we increase sensitivity and limit the influence of the background-dominated low-energy region. To demonstrate this technique, we performed source injection simulations, simple source detection tests, and blind tests at University of Texas football games. Applications in wide-area monitoring through detectors on vehicles, such as buses, are explored. We also probe the feasibility of using kriging methods from geostatistics to provide more accurate anomaly mapping.