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Explosive Detection
regular use; they can generally only work yet to provide the required level of performance requirements that could be
for brief periods, they have significant sensitivity for the robust explosives used to evaluate their operational
upkeep costs, and they are unable to detection systems needed for airports. effectiveness and suitability for a
communicate the identity of the detected Recent promising research in 2008 and security checkpoint. Many environments
explosives residue. Also, they require a 2009, however, shows that FTS operating pose serious challenges to the detection
human handler when performing their in reflection-absorption mode has of chemical weapons and explosives,
detection role. been demonstrated as a potential with problems of concealment,
Traditional detection methods for these spectroscopic technique to develop new encapsulation and false alarm rates.
materials, such as Ion Mobility methodologies for detection of explosive Among the operational requirements are
Spectroscopy (IMS) and Gas constituent chemicals deposited on sensitivity, selectivity, range of explosive
Chromatograph Mass Spectroscopy metallic surfaces. and chemicals detected, logistics,
(GCMS), do not lend themselves to easy reliability regular maintenance and cost-
deployment for high throughput of-ownership.
screening of individuals or packages with Trace Detection Agencies must ensure the safety of
high sensitivity and low false alarm rate. Trace detection is one of the most the population being screened while
Therefore, liquids restrictions at airports accurate technologies that can be used performing the continuous screening
are unlikely to be abandoned until for detecting and identifying materials. It tasks in a timely manner, so that
detection systems are able to identify detects the presence of constituent neither commerce nor traffic is
small amounts of novel explosives elements of explosive materials by significantly impacted.
promptly and accurately. collecting and analysing trace molecular The explosive peroxide compounds
evidence from the explosive or its vicinity. triacetone triperoxide (TATP) and
Standard laboratory instruments used for hexamethylenetriperoxide diamine
So What’s New? trace detection of chemicals include gas (HMTD) are difficult to detect by
When considering new detection and liquid chromatography and various conventional mass spectrometry
technologies, all chemical and physical spectroscopies, including mass methods. However, recent research by
aspects of the IED should be examined spectroscopy and Ion Mobility instrumentation manufacturer Jeol, USA
for possible exploitation. The elemental Spectrometry (IMS). These instruments shows that these compounds can be
composition of commonly used can provide definitive multi-species detected by the Direct Analysis in Real
explosives may be a means by which identification. Time (DART™) ion source. Measurements
explosives can be detected in a package One of the novel and emerging trace were made with the AccuTOF-DART mass
or in luggage. The high nitrogen and technologies is High-Frequency Quartz spectrometer operated in positive-ion
oxygen content in many explosives can Crystal Microbalance (HF-QCM). The mode under standard conditions. Dilute
provide a characteristic signal for these principle of detection of HF-QCM solutions of TATP and HMTD samples
compounds. Thermal and mechanical technology is based on the frequency of were analysed by dipping melting point
properties of IEDs may also be used for vibration of an oscillating crystal, which is tubes into the liquid and dangling the
detection. Infrared (IR) imaging of a decreased by an adsorption of a foreign melting point tubes in the DART ion
suicide bomber, sonic imaging, material on its surface. A chemical source, resulting in a positive detection
anomalous movement of cars or people, coating located on the crystal surface, for TATP. The sample was placed between
or detection of the components of a thereby increasing the weight of the the DART and the mass spectrometer
bomb such as the battery, control sensor and decreasing its frequency of without needs for solvents or sample
mechanism, detonator, or container also vibration, selectively adsorbs a gaseous preparation. The DART is claimed to be
may be utilised for explosives detection. pollutant. The decrease in the frequency able to analyse and identify samples
Full use of the electromagnetic is proportional to the increase in weight, directly on surfaces such as concrete,
spectrum may provide novel means by thus creating a unique fingerprint of the currency, food, pills and clothing.
which IEDs can be detected. For material being tested, while keeping a
example, use of radio-frequency, neutron fast recovery and ready-to-ready time.
analysis, or X-ray backscatter may offer When evaluating different detection
opportunities for finding concealed technologies, there are important
explosives. Electro-optical properties,
including millimetre wave imaging
(passive/active), radar, terahertz “...in 2010, the U.S.
imaging, and Raman spectroscopy are
just some of the other options available spectroscopy market is
for this task.
Optical IR spectroscopic techniques expected to be $5.2
such as Fourier Transform Spectroscopy
(FTS) or Laser Absorption Spectroscopy billion, increasing at an
(LAS) have been employed to examine
constituents of the Earth's atmosphere average annual growth Passenger’s tie being screened by the
and stars and can therefore detect AccuTOF-DART (Credit: Jeol)
various compounds. However, they are rate of 8%...”
18 Register now for FREE instant access to ASI online by visiting www.asi-mag.com August 2009 Aviationsecurityinternational
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