Technical Insights' Homeland Security Alert
Palo Alto, Calif. January 27, 2004 The terrorist acts of September 11, 2001, triggered large-scale deployment of explosive detection systems as well as explosive trace detectors, as airports across the United States rushed to protect themselves against further attacks.
"To enforce the post-9/11 requirement that all check-in baggage be inspected for traces of explosives and chemicals, at least 429 American airports use CAT scanners, each costing three-quarters of a million dollars, to scrutinize the 1.5 billion pieces of luggage inspected annually," notes Technical Insights Analyst Michael Valenti.
While explosive detection systems scan for explosives, explosive trace detectors track the molecules given off by target explosives. Both systems are attracting greater funding and resources for research and development as they become increasingly important in the drive to prevent acts of terrorism.
Some of the leading technologies employed in explosive detection systems are derived from medical applications. Examples are computed tomography and quadrupole resistance analysis, which is similar to magnetic resonance imaging.
Quadrupole resistance is used to detect explosives in baggage that has been checked or placed in aircraft cabins. Its primary advantage is that it does not use ionizing radiation or strong magnetic fields. This asset boosts its safety levels, which is important in its application and during transportation.
The main technical challenge facing quadrupole resistance is the need to improve its signal-to-noise ratio and response to various explosives. These challenges have spurred companies to develop new ways of stimulating quadrupole resistance response from explosives to yield more information in a given period.
"The quest to develop new types of explosive detection systems has resulted in the creation of a hybrid system that integrates computed tomography and quadrupole resistance technologies," says Valenti.
Equipped with enhanced detection capabilities, this combination system allows for higher probability rates and lower false alarm rates, as well as a higher throughput than an individual computed tomography or quadrupole resistance system.
Interestingly, companies are attempting to use quadrupole resistance technology to screen not only baggage but also passengers, for explosives or weapons. Prototype quadrupole resistance-based products for monitoring passengers include shoe scanners and a portal that scans people for explosives as they walk through it. This is particularly helpful in identifying liquid explosives such as Piccatinny and other flammables, at checkpoints.
Mass spectrometry is rapidly gaining importance for use in explosive detection systems. Mass spectrometry, when compared with ion mobility spectrometry, provides higher resolution that minimizes false positives. By using mass spectrometry, scientists have developed an explosive trace detector that can identify traces of explosive on passengers' air tickets.
Mass spectrometry systems are significantly more expensive than currently deployed X-ray and ion mobility spectrometry technologies, making it difficult to present a compelling cost-benefit analysis to end users. Nevertheless, mass spectrometry is likely to be preferred to ion mobility spectrometry because of its higher chemical specificity and ability to inherently register few false negatives or positives.
Increased research funding and miniaturization may help bring down the high costs of mass spectrometry. In fact, with the development of miniature, portable mass spectrometry devices, mass spectrometry is likely to dominate explosives detection.
Scientific research on using neutrons to uncover explosives has yielded two patented technologies: thermal neutron analysis and pulsed fast neutron analysis. The thermal neutron analysis technology forms the basis of mobile security inspection systems. Installed in an unmarked truck, mobile explosive detection systems surreptitiously scan vehicles for explosives, and can be used to great effect at high-profile terror targets such as sporting events and government buildings.
Source: Eurekalert & othersLast reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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