Utilization of advanced clutter suppression algorithms for improved spectroscopic portal capability against radionuclide threats

The threat posed by terrorist use of nuclear or radiological weapons is of serious concern to the United States. Portal monitoring and inspection systems provide a major domestic layer of defense against the transportation of these materials. Recent efforts have focused on the development of spectroscopic radiation portal monitors (RPM) for inspection of commercial cargo at ports of entry and border-crossings. However, reduced detection sensitivity encountered by these systems in cluttered conditions imposes limits on how fast traffic can move through the portals. This limitation results in unacceptable disruptions to the flow of commerce. Physical Sciences Inc. (PSI) and Raytheon Integrated Defense Systems (RTN) have recently demonstrated significant performance enhancement from existing Advanced Spectroscopic Portal (ASP) systems through the use of new advanced detection and identification algorithms. The Poisson Clutter Split (PCS) algorithm, developed by PSI under DHS/DNDO (Domestic Nuclear Detection Office) sponsorship, has been integrated with a RTN ASP unit and evaluated in field trials. In this paper, we present a detailed quantitative analysis of PCS-ASP performance against field data collected against check sources embedded in a commercial cargo truck. Utilizing only 4 out of 12 NaI detectors in the ASP system, we show that the capability achieves a high probability of detection and identification, with low false alarm rates, while observing cargo moving through the portal at significantly higher speeds than previously possible.