Investigation of Source Detection Algorithms for Gross Counting Portal Monitors

In recent years, heightened security concerns have prompted increased interest in radiation portal monitors, instruments capable of detecting, and in some cases identifying, gamma-ray and neutron-emitting radioactive material passing through them. Along with efficient and reliable physical detectors, such monitors need software capable of analyzing the resulting signals in order to effectively catch weak radioactive sources. The software should be able to distinguish between the sometimes subtle signals due to weak sources and the varying background. After investigating several possible source-detection algorithms, a program has been developed to locate signals from weakly radioactive sources in real time. By including corrections for background suppression due to trucks shielding the detector and changing background levels, this program is capable of detecting significantly weaker sources than current software. The limitations of this method will also be discussed.