Detecting small low emission radiating sources

In order to prevent influx of highly enriched nuclear materialthrou-gh border checkpoints, new advanced detection schemes need to bedeveloped. Typical issues faced in this context are sources with verylow emission against a dominating natural background radiation. Sourcesare expected to be small and shielded and hence cannot be detected frommeasurements of radiation levels alone.We consider collimated and Compton-type measurements and propose a detectionmethod that relies on the geometric singularity of small sources todistinguish them from the more uniform background.The method is characterized by high sensitivity and specificity andallows for assigning confidence probabilities of detection.The validity of our approach can be justified using properties ofrelated techniques from medical imaging. Results of numericalsimulations are presented for collimated and Compton-type measurements.The 2D case is considered in detail.