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Posted: November 16, 2009
New detector can reliably and rapidly identify liquid explosives
(Nanowerk News) Soft drinks, cosmetics, medications, and more still – since an attempted terrorist attack on a commercial airliner was thwarted at the last second in 2006 air passengers are only allowed to carry limited amounts of liquids and gels in their hand luggage. Different principles for monitoring devices for the identification of hazardous liquids have since been suggested, but none of them have yet gained acceptance at airports around the world. Jülich physicists are now proposing a promising new method. In the science journal Superconductor Science and Technology ("Liquid identification by Hilbert spectroscopy"), Jülich physicists presented (20 October 2009) their prototype of a new detector that can reliably and rapidly distinguish between liquid explosives and harmless substances.
"Explosive liquids or liquid components that can be used to concoct explosives on board an aircraft can be identified by our method within a fraction of a second. Our process for screening liquids is therefore not only much faster than other methods, but also much more reliable. Only if hazardous substances can be reliably identified without long detection times and false alarms, therefore avoiding long queues, will passengers be allowed to carry liquids on board aircraft in their hand luggage again," said Prof. Knut Urban, head of the institute involved at Forschungszentrum Jülich.
For their detector, Urban and his team at the Institute of Solid State Research exploit a particular form of spectroscopy that allows substances to be analysed with the aid of electromagnetic radiation. All liquids absorb and reflect radiation of various wavelengths in a different way and can thus be identified on the basis of their specific "fingerprint".
The experimental setup shows a prototype of the detector on the left, the light source on the right, and the liquid being examined in a bottle in the middle. (Picture: Forschungszentrum Jülich)
The idea of using electromagnetic radiation for tracking down hazardous liquids is not new. However, previous systems have only used a very narrow frequency range of electromagnetic radiation and can thus only identify a small section of the fingerprint. It is not therefore possible to distinguish hazardous substances from harmless liquids and there is a danger of false results if different liquids are mixed.
Jülich scientists have developed a system which can perform measurements over a broad frequency range from a few gigahertz up to several terahertz within just 200 milliseconds. In this way, a detailed molecular fingerprint can be compiled for each measurement permitting a reliable comparison with the reference data of hazardous liquids. At the heart of the so-called Hilbert spectrometer is a novel nanoelectronic component – a so-called Josephson junction. It functions as a highly sensitive, ultrafast broad-band sensor and, with computer control, converts the recorded spectrum into an electronic signal by means of which the suspicious liquids can be identified.
The Jülich researchers have successfully demonstrated that their system can rapidly and reliably detect different liquids such as water, ethanol, methanol, propanol and acetone. Dr. Yuri Divn, the lead researcher in this project, says: "We have thus proved that our method functions successfully. We are now working on reducing the size of the device and optimizing the details and also investing other applications. We are convinced that industry will show interest and that, with our support, they will be able to develop a marketable product."