Bang to rights
bearing in mind that an explosive’s excitation by a laser can have unpleasant side effects! What twists and ideas have you had for that not to be issue? AF: We have been focussing on UV Raman and long as well as short-wave IR detection. What you saw at Fort Leonard Wood was their laser-induced breakdown spectroscopy (LIBS) approach and there are a number of reasons why we have backed off from LIBS as an approach for detection. We have backed off not only because of the issue you just mentioned – where you are pumping a lot of energy onto the surface to allow the molecule to break apart – but because there are some other inherent difficulties with LIBS that have been borne out in the evaluations. One is that LIBS by definition is an atomic technique, it is not a molecular technique, so it will only give you the empirical formula or a hint of the molecular content. For chemists it is vital to know how those atoms are connected, and LIBS will not give you that information. The other difficulty is that when you ablate a material from a surface, those atoms from the underlying layer also get liberated and contribute to the background and the LIBS signal, so teasing out a definitive result is challenging. LIBS is a tool that has its place, but not as a molecular detector. There are some other issues concerning eye safety with LIBS, which we felt meant that it was not ready for as rapid a development, so we have been focussing primarily on deep UV Raman for detection. When you are talking about laser detection it is still a small area on a surface as opposed to looking at active and passive long-wave and short-wave infra-red detection of explosive materials on surfaces
GW: What are the concepts of operation for your standoff? Are you at the ‘volatile plume from a large store of precursors’ end of the scale, or at the trace elements on a car door handle end? What part of the scale are you looking to detect? AF: Our biggest challenge is the detection of trace materials on surfaces, and that is what we are focussing on, not plume detection. When you have an explosive, which already has a very low vapour pressure, and you contain it in a plastic
jug and bury it six inches in the ground, there is not a lot of vapour there to detect! We have been focussing our efforts on understanding the limitations of all these detection capabilities for trace chemicals on surfaces.
GW: Explosive agent fate would seem to be a great project for civil buy-in and exploitation. Are you seeing a great deal of interest from them?
AF: The chemical fate of these explosives, especially on surfaces, has not been of tremendous interest to universities, and that is one of the reasons that we are doing it. It hasn’t been of academic interest, but it is of tremendous importance for all these sensing systems. If I can develop a system that can detect an explosive on a surface, but the explosive degrades on that surface very rapidly, then the detector will never find it! So having those questions answered before we go into an instrumental development program is clearly important. There is more work to do in this area, and we can’t do it all. We have neither the time nor the money, and whilst I would like to hear from people in academia that would be interested in pursuing this, it has not hitherto been of great interest outside the DoD
GW: I realise that I have been heavily influenced by CSI! You see all these forensics shows and you assume that this sort of research had been done years ago…
AF: If it has been done they have published it in journals I am not aware of! What you see on TV as opposed to what happens in the real world are two different things. Doing that detailed fate and transport studies may be of interest to us in understanding how systems perform, but it might not be of interest to law enforcement or the EOD tech that has a vote in what research gets done!
GW: The ATO funding is coming to an end, and whilst it is an explosive project, it is essentially a chemical detection program. How do you ensure that some of the interesting sidelines that have come up – such as the upgrades in JCAD – are not forgotten when you transition back?
AF: Even though the ATO finishes at the end of this fiscal year, the Army will continue to fund us in two areas: one is forensics and the second, detection mechanisms. We cover a broad area, not just in terms of explosives, but in terms of developing a better understanding of how we can use the tools that we have for chemical and biological programs and apply them to other threats, primarily explosives. So we will continue some of the sensor work under a 6.3 program (detection mechanisms), and our intent is to provide a solution in conjunction with JPEO for both the Shed and JCAD at some point – Shed in FY13 and a dual purpose JCAD in FY14. Our intent is to be able to mature as far as we can, at which point an acquisition authority will have to take over. That is always the hard part, because despite the fact that a project might become a ‘baby’ to a research team and that team may want to keep it with them forever, it ultimately has to leave the nest.
GW: So over the past five years we could say that Shed, JCAD and some of the forensics have been a success. If we came back at the end of the next five years what would the program look like? AF: I think Shed will transition, and we will continue to update it as new threats emerge. For the US DoD we already have some of the major threats covered and I am pretty confident that JCAD will be able to expand chemical detection beyond CWA, without introducing new interferents for the CWA. When we look back that will be a key transition. We are hopeful that we have demonstrated the capability for deep UV Raman for standoff detection of threats, not just explosives – we have been doing it for chemical for some time. That will play well with some of the work that Nato is doing with different terms; so there are detectors where the chemical has to make either close contact with or go inside the detector to be analysed, then proximity detection. In the case of deep UV Raman, anything from a few millimetres to 300 metres is in the range of the possible. True standoff, i.e., detection from one kilometre, or horizon detection, is a long way off for explosives right now.
CBRNe South America 2012, 13-14 March, Rio De Janeiro, Brazil. More information on
www.icbrnevents.com 52 CBRNe WORLD February 2012
www.cbrneworld.com
CBRNeWORLD
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