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Engineers at the U.S. Department of Energy's Argonne National Laboratory, using an emerging sensing technology, have developed a suite of sensors for national security applications that can quickly and effectively detect chemical, biological, nuclear and explosive materials.
"We can use this technology to detect chemical and biological agents and also to determine if a country is using its nuclear reactors to produce material for nuclear weapons or to track the direction of a chemical or radioactive plume to evacuate an area," explained Paul Raptis, section manager. Raptis is developing these sensors with Argonne engineers Sami Gopalsami, Sasan Bakhtiari and Hual-Te Chien.
Argonne engineers have successfully performed the first-ever remote detection of chemicals and identification of unique explosives spectra using a spectroscopic technique that uses the properties of the millimeter/terahertz frequencies between microwave and infrared on the electromagnetic spectrum. The researchers used this technique to detect spectral "fingerprints" that uniquely identify explosives and chemicals.
The Argonne-developed technology was demonstrated in tests that accomplished three important goals: Detected and measured poison gas precursors 60 meters away in the Nevada Test Site to an accuracy of 10 parts per million using active sensing.
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Identified chemicals related to defense applications, including nuclear weapons, from 600 meters away using passive sensing at the Nevada Test Site.
Built a system to identify the spectral fingerprints of trace levels of explosives including DNT, TNT, RDX and plastics explosives semtex and C-4. Current research involves collecting a database of explosive "fingerprints" and, working with partners Sarnoff Corp., Dartmouth College and Sandia National Laboratory, testing a walk-through portal system to quickly screen people for trace explosives.
Argonne engineers have been exploring this emerging field for more than a decade to create remote technology to detect nuclear facilities that may be violating nonproliferation agreements by creating materials for nuclear weapons or making nerve agents.
How it works
The millimeter/terahertz technology detects the energy levels of a molecule as it rotates. The frequency distribution of this energy provides a unique and reproducible spectral pattern – its "fingerprint" – that identifies the material. The technology can also be used in its imaging modality – ranging from concealed weapons to medical applications such as tumor detection.
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The technique is an improvement over laser or optical sensing, that can be perturbed by atmospheric conditions or X-rays which can cause damage by ionization. Operating at frequencies between 0.1 and 10 terahertz, the sensitivity is four to five orders of magnitude higher and imaging resolution is 100 to 300 times more than possible at microwave frequencies.
Other homeland security sensors
To remotely detect radiation from nuclear accidents or reactor operations, Argonne researchers are testing millimeter wave radars and developing models to detect and interpret the radiation-induced effects in air that cause radar reflection and scattering. Preliminary results of tests with the instruments located 9 kilometers from a nuclear power plant showed clear differences between the times the plant was operating and when it was idling. This technology can also be applied to mapping plumes from nuclear radiation releases.
Argonne engineers have also applied this radar technology for remote and rapid imaging of gas leaks from natural gas pipelines. The technique detects the fluctuations in the index-of-refraction caused by leaking gas into the surrounding air medium.
Early warnings of biological hazards can be made using another Argonne-developed sensing system that measures dielectric signatures. The systems sense repeatable dielectric response patterns from a number of biomolecules. The method holds potential for a fast first screening of chemical or biological agents in gases, powders or aerosols.
Other tests can be used to detect these agents, but they can take four hours or more. "While this method may not be as precise as other methods such as bioassays and biochips, it can be an early warning to start other tests sooner," said Raptis.
These Argonne sensor specialists will continue to probe the basics of sensor technology and continue to develop devices that protect the nation's security interests.
Other potential applications for these technologies in addition to security include nondestructive evaluation of parts, environmental monitoring and health applications including testing human tissue and replacing dental X-rays.
In addition to DOE, the following agencies have provided support for this research: Department of Defense, National Aeronautics and Space Administration and the National Institutes of Health.
The nation's first national laboratory, Argonne National Laboratory conducts basic and applied scientific research across a wide spectrum of disciplines, ranging from high-energy physics to climatology and biotechnology. Since 1990, Argonne has worked with more than 600 companies and numerous federal agencies and other organizations to help advance America's scientific leadership and prepare the nation for the future. Argonne is managed by the University of Chicago for the U.S. Department of Energy's Office of Science.