Navy

Trace vapor generator for explosives detector verification

Device provides a uniform, reliable method for evaluating detection systems used for personnel and facility protection

Electronics Sensors

The U.S. Naval Research Laboratory has built a compact trace vapor generator for explosives and narcotics (TV-Gen) for testing and calibrating trace chemical detectors used by law enforcement officials. The device is available, via patent license agreement, to businesses for commercialization.

The TV-Gen, left, and the control box. (NRL photo)

The trace vapor detection of explosives and narcotics is critical to guarding borders and high-value targets.

Sensors used by law enforcement officials and transportation security officers are designed to detect extremely small concentrations of explosives and narcotics in the parts-per-million range.

Scientific research and development efforts are currently underway to produce new sensors with parts per quadrillion detection capabilities. Both current and future trace chemical detectors require initial calibration and periodic testing for reliability and accuracy.

Many narcotics and explosives have chemicals with low vapor pressures that make it difficult to accurately produce trace vapors in the small amounts needed.

The dual-manifold and Pneumatically Modulated Liquid Delivery System. (NRL illustration)

Current vapor generation techniques, such as ink-jet droplet formation or chemical deposition on quartz wool or glass beads placed in temperature controlled zones, are used to generate trace vapors but are hampered by pulsed or steadily declining streams. It can also be difficult to change concentrations for dynamic range studies with these techniques. And none of these techniques offer the capability of switching between clean and analyte air streams.

To address the above deficiencies, Navy researchers built the TV-Gen to consistently and accurately generates trace vapors of low vapor pressure compounds in the parts per quadrillion to parts per million range.

The TV-Gen consists of a control box and an oven that can be heated to 130°C. Trace compounds are introduced to a diluent air-vapor stream via nebulization, which effectively vaporizes compounds that otherwise decompose at elevated temperatures.

The perfluoroalkoxy total-consumption microflow nebulizer is coupled to a Pneumatically Modulated Liquid Delivery System. The manifold is contained within the oven to ensure minimal adsorption of analytes or explosives to the surfaces and was designed to be easily exchanged and can be totally disassembled for thorough cleaning.

The TV-Gen was used in the advancement of the silicon nanowire trace chemical detection technology also from NRL. These trace vapor technologies are available for license to U.S. and foreign companies, together or separately, depending on business needs.

These technologies are capable of government trace chemical vapor standards compliance in the U.S and abroad.

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