Performance Characteristics of a Third-generation Spectroscopic Vehicle Portal Monitor based on High Purity Germanium Detectors

The general need for improved detection performance and reduced decision time for portal monitors, freight container scanners, and mobile search systems is being achieved with systems utilizing High-Purity Germanium (HPGe) detectors. Highly specialized software analyzes the spectroscopic data to produce accurate results in live time. To meet the need, a new generation monitor has been developed using eight integrated gamma-ray spectrometers, video recording of the container, automatic spectroscopic and video data collection, analysis, reporting, alarming, and archiving all raw data and results. Previous work reported on the modeling of the performance of a primary cargo portal based on similar HPGe detection systems with 12 HPGe detectors on each side of the traffic lane. The expected performance of this 24-detector cargo portal was shown to exceed the ANSI N42.38 requirements. In other work, performance data were presented of a secondary freight portal monitor with 4 detectors on each side of the traffic lane. Operational experience from the installed system has been reported. These results were used in a new design of a portal monitor providing primary inspection capabilities to comply with the performance requirements of ANSI N42.38, with 16 HPGe detectors along with improved identification algorithms. This paper will describe the elements of the new primary portal design and present test results on its performance relative to previous systems.