Performance of the Roadside Tracker Portal-Less Portal Monitor

We have developed a proof-of-concept prototype, rapid-deployment, gamma-ray portal monitor that can uniquely link the radiation signatures and visible-light images of vehicles in the system´s field of view from the side of a multilane roadway. The instrument uses both visible-light and gamma-ray imaging to accomplish this. Vehicles entering the field of view of the visible-light imaging system are identified and tracked by an automated target acquisition and tracking software engine. The vehicle locations provided by this code are reported to the gamma-ray imager which uses them to locate the vehicles in the gamma-ray images and to collect the vehicle-specific radiation signatures from those images. Using this technique the gamma-ray data is integrated over the entire residence time of the vehicle in the gamma-ray imager field of view. The complete instrument comprises ~ 1-m²CsI(Na) detector area split between two units. The system has been designed to handle up to five-lanes of traffic at highway speeds, with one unit located on either side of the roadway. Because no equipment is required in the roadway, the instrument can be deployed without impacting the flow of traffic. The results of a test and evaluation campaign indicates that the system meets its design goal of detecting 37 MBq-class sources in any of five-lanes of traffic at up to 113 km/h.