Explosive detection: Difference between revisions

Revision as of 22:37, 20 September 2022

Revision as of 09:04, 29 September 2022

Line 5:

===Colorimetrics & automated colorimetrics===

The use of colorimetric test kits for explosive detection is one of the most established, simplest, and most widely used methods for the detection of explosives. Colorimetric detection of explosives involves applying a chemical reagent to an unknown material or sample and observing a color reaction. Common color reactions are known and indicate to the user if there is an explosive material present and in many cases the group of explosiveexplosives from which the material is derived. The major groups of explosives are [[Nitroaromatic compound|nitroaromatic]], [[nitrate ester]], and [[Nitroamine|nitramine]] explosives, as well as inorganic nitrate -based explosives. Other groups include [[Chlorate|chlorates]] and [[Peroxide|peroxides]] which are not nitro based explosives. Since explosives usually contain nitrogen, detection often is based around spotting nitrogenous compounds. As a result, traditional colorimetric tests have a disadvantage: some explosive compounds (such as [[acetone peroxide]]) do not contain nitrogen and are therefore harder to detect.<ref>{{Cite book |last=Marshall |first=Maurice |url=https://www.worldcat.org/oclc/316212529 |title=Aspects of explosives detection |last2=Oxley |first2=Jimmie |date=2009 |publisher=[[Elsevier]] |isbn=978-0-08-092314-7 |edition=1st |___location=Amsterdam |doi=10.1016/B978-0-12-374533-0.X0001-3 |oclc=316212529}}</ref>

===Dogs===

Line 25:

{{main|Explosives trace detector}}

{{see also|Machine olfaction}}

Several types of machines have been developed to detect trace signatures for various explosive materials. The most common technology for this application, as seen in US airports, is [[ion mobility spectrometry]] (IMS). This method is similar to [[mass spectrometry]] (MS), where molecules are ionized and then moved in an electric field in a vacuum, except that IMS operates at atmospheric pressure. The time that it takes for an ion, in IMS, to move a specified distance in an electric field is indicative of that ion's size-to-charge ratio: ions with a larger cross -section will collide with more gas at atmospheric pressure and will, therefore, be slower.

[[Gas chromatography]] (GC) is often coupled to the detection methods discussed above in order to separate molecules before detection. This not only improves the performance of the detector but also adds another dimension of data, as the time it takes for a molecule to pass through the GC may be used as an indicator of its identity. Unfortunately, GC normally requires a bottled gas, which presents logistical issues since bottles would have to be replenished. GC columns operated in the field are prone to degradation from atmospheric gases and oxidation, as well as bleeding of the [[Stationary phase (chemistry)|stationary phase]]. Columns must be very fast, as well, since many of the applications demand that the complete analysis be completed in less than a minute.{{Citation needed |date=January 2020}}

===Spectrometry===

Technologies based on [[ion mobility spectrometer]] (IMS) include [[ion trap mobility spectrometry]] (ITMS), and [[differential mobility spectrometry]] (DMS). [[Amplifying fluorescent polymers]] (AFP) use a molecular recognition to "turn off" or quench the [[fluorescence]] of a polymer. [[Chemiluminescence]] was used frequently in the 1990s, but is less common than the ubiquitous IMS. Several attempts are being made to miniaturize, ruggedize and make MS affordable for field applications; such as an [[aerosol]] polymer that fluoresces blue under UV but is colorless when it reacts with nitrogen groups.<ref>{{Cite web |last=Barras |first=Colin |date=2008-06-03 |title=Glowing spray lets CSI operatives 'dust' for explosives |url=https://www.newscientist.com/channel/tech/dn14048-glowing-spray-lets-csi-operatives-dust-for-explosives.html |archive-url=https://web.archive.org/web/20220920223601/https://www.newscientist.com/article/dn14048-glowing-spray-lets-csi-operatives-dust-for-explosives/?ignored=irrelevant |archive-date=20 September 2022 |publisher=[[New Scientist]]}}</ref>

One technique compares reflected [[ultraviolet]], [[infrared]] and [[visible light]] measurements on multiple areas of the suspect material. This has an advantage over olfactory methods in that a sample does not need to be prepared. A patent exists for a portable explosive detector using this method.<ref>{{Cite web |last=Mullins |first=Justin |date=2008-05-28 |title=Portable explosives detector |url=https://www.newscientist.com/blog/invention/2008/05/portable-explosives-detector.html |archive-url=https://web.archive.org/web/20080911045557/https://www.newscientist.com/blog/invention/2008/05/portable-explosives-detector.html |archive-date=11 September 2008 |website=[[New Scientist]] Blogs}}</ref>

Line 39:

Specially designed [[X-ray machine]]s can detect explosives by looking at the density of the items being examined. They use [[computed axial tomography]] based systems that are enhanced with dedicated software, containing an explosives threat library and false-color coding, to assist operators with their dedicated threat resolution protocols.{{Citation needed|date=July 2008}} X-ray detection is also used to detect related components such as [[detonator]]s, but this can be foiled if such devices are hidden inside other electronic equipment.<ref>{{cite magazine |url= https://www.newscientist.com/channel/tech/weapons/dn9715|title=Analysis: Explosive detection technologies| first =Will | last = Knight|date=10 August 2006 |magazine=[[New Scientist]] news service |archive-url=https://web.archive.org/web/20220920215223/https://www.newscientist.com/article/dn9715-analysis-explosive-detection-technologies/ |archive-date=20 September 2022}}</ref>

Recently, [[machine learning]] algorithms have been developed that can automatically detect threatthreats in x-ray scans. <ref>{{Cite journal|last1=Heitz|first1=Geremy|last2=Chechik|first2=Gal|title=Object separation in x-ray image sets|date=2010|journal=IEEE Computer Society Conference on Computer Vision and Pattern Recognition|pages=2093–2100|publisher=[[IEEE]] |doi=10.1109/cvpr.2010.5539887|isbn=978-1-4244-6984-0|s2cid=2643208}}</ref><ref>{{Citation|last=Mery|first=Domingo|title=Simulation in X-ray Testing|date=2015|work=Computer Vision for X-Ray Testing|pages=241–266|place=Cham|publisher=[[Springer International Publishing]] |doi=10.1007/978-3-319-20747-6_7|isbn=978-3-319-20746-9}}</ref><ref>{{Cite journal|last1=Akcay|first1=Samet|last2=Breckon|first2=Toby P.|title=An evaluation of region -based object detection strategies within X-ray baggage security imagery|journal= IEEE International Conference on Image Processing (ICIP)|publisher=[[IEEE]]|date=2017|pages=1337–1341|doi=10.1109/icip.2017.8296499|isbn=978-1-5090-2175-8|s2cid=3451234}}</ref>

===Neutron activation===

Specially designed machines bombard the suspect explosives with neutrons and read the resulting [[gamma radiation]] decay signatures to determine the chemical composition of the sample. The earliest developed forms of [[Neutron Activation Analysis]] use low -energy neutrons to determine the ratios of nitrogen, chlorine, and hydrogen in the chemical species in question, and are an effective means of identifying most conventional explosives. Unfortunately, the much smaller thermal [[Neutron cross section]]s of carbon and oxygen limit the ability of this technique to identify their abundances in the unknown species, and it is partly for this reason that terror organizations have favored nitrogen absent explosives such as [[Acetone peroxide|TATP]] in the construction of [[Improvised explosive device|IED]]s. Modifications to the experimental protocol can allow for easier identification of carbon and oxygen -based species, (e.g. the use of [[inelastic scattering]] from [[fast neutron]]s to produce detectable gamma rays, as opposed to simple absorption occurring with the [[thermal neutron]]s), but these modifications require equipment that is prohibitively more complex and expensive, preventing their widespread implementation.<ref>{{Cite journal | url= https://www.researchgate.net/publication/264561529 | doi=10.1007/s10967-014-3260-5 | title=A review of conventional explosives detection using active neutron interrogation | journal=[[Journal of Radioanalytical and Nuclear Chemistry]] | volume= 301| issue=3| pages=629–39| year= 2014 | last1=Whetstone| first1=Z. D. | last2= Kearfott| first2=K. J.| s2cid=93318773 }}</ref>

===Silicon nanowires for trace detection of explosives===

Line 51:

==Bogus detection devices==

The [[United States Department of Justice|US Department of Justice]] warned in a [[National Institute of Justice]] publication, "Guide for the Selection of Commercial Explosives Detection Systems for Law Enforcement Applications (NIJ Guide 100-99)," about the ongoing trend of "bogus" explosives detection equipment being sold to unsuspecting consumers. The report mentions by name the [[Quadro Tracker]], an apparent [[dowsing rod]] with a freely pivoting radio antenna rod with no functioning internal components. On August 8–9, 2005 the [[Naval Explosive Ordance Disposal Technical Division]] via the United States Counter -Terrorism Technology Task Force conducted testing on the [[Sniffex|SNIFFEX]] and concluded that "the SNIFFEX handheld detector does not work".<ref>{{Citation | title = Test Report: The Detection Capability of the Sniffex handheld Explosives Detector |date=September 2005 |author=[[Naval Explosive Ordnance Disposal Technology Division]] | url = http://s3.amazonaws.com/propublica/assets/docs/NavyReport.pdf |archive-url=https://web.archive.org/web/20220814000040/http://s3.amazonaws.com/propublica/assets/docs/NavyReport.pdf |archive-date= 14 August 2022}}</ref>

{{Quote | …There is a rather large community of people around the world that believes in [[dowsing]]: the ancient practice of using forked sticks, swinging rods, and pendulums to look for underground water and other materials. These people believe that many types of materials can be located using a variety of dowsing methods. Dowsers claim that the dowsing device will respond to any buried anomalies, and years of practice are needed to use the device with discrimination (the ability to cause the device to respond to only those materials being sought). Modern dowsers have been developing various new methods to add discrimination to their devices. These new methods include molecular frequency discrimination (MFD) and harmonic induction discrimination (HID). MFD has taken the form of everything from placing a xerox copy of a Polaroid photograph of the desired material into the handle of the device, to using dowsing rods in conjunction with frequency generation electronics (function generators). '''None of these attempts to create devices that can detect specific materials such as explosives (or any materials for that matter) have been proven successful in controlled double-blind scientific tests.''' In fact, all testing of these inventions has shown these devices to perform no better than random chance…<ref>{{cite web |author=[[Office of Justice Programs|US Department of Justice Office of Justice Programs]] |url= http://www.ojp.usdoj.gov/nij/pubs-sum/178913.htm |title= Guide for the Selection of Commercial Explosives Detection Systems for Law Enforcement Applications: NIJ Guide 100-99 |date= September 1999 |archive-url=https://web.archive.org/web/20220320180553/https://www.ojp.gov/pdffiles1/nij/178913.pdf |archive-date=20 March 2022}}</ref>}}