FIELD PERFORMANCE EVALUATION OF A PROTOTYPE VEHICLE PORTAL BASED ON TRACE EXPLOSIVES DETECTION

Screening vehicles for large vehicle bombs is one of the most important and challenging problems that currently exists in the field of explosives detection. Terrorist incidents involving large vehicle bombs have tragically demonstrated their catastrophic effects. Sandia National Laboratories (SNL) has developed a prototype trace explosives detection portal for screening vehicles. The vehicle portal performs localized sampling to detect explosives particle contamination on the vehicle’s exterior. The operating principle of the portal is derived from a personnel portal developed at SNL and now commercially available. The portal combines 1) air jet nozzles for dislodgment of particle contamination from the exterior of a vehicle, 2) specially designed air flows to transport explosives vapor and airborne particles, 3) two stages of preconcentration of the sample using technology based on a patented Sandia design, and 4) a commercially available ion mobility spectrometer that is employed as the chemical sensor. The vehicle portal and its mobile version have undergone performance evaluation testing in laboratory and field environments. The mobile version provides drive-up access for vehicles of varying sizes and has an improved throughput rate, in comparison to the original prototype. Highlights of the laboratory and field test results of the vehicle portal with key explosives are described. It was demonstrated that the vehicle portal provides sub-fingerprint sensitivity to key explosives, and a high detection rate (> 90%) and a low false alarm rate (< 10%). Even with the throughput rate limitation, the existing vehicle portal can be deployed for applications with less stringent throughput requirements such as “checkpoint” vehicle inspections at borders, military facilities, embassies, etc.