Seeing through the Subterfuge - Spectroscopy through packaging

Some substances, including drugs and explosives, can be concealed by dissolving them in another liquid such as an innocent looking bottle of spirits or packaging them inside an...
26 June 2012

Interview with 

Professor Pavel Matousek, Cobalt Light Systems


X-ray Luggage screening device at Suvarnabhumi International Airport, BangkokHelen -   Some substances, including drugs and explosives, can be concealed by dissolving them in another liquid such as an innocent looking bottle of spirits or packaging them inside an opaque container.  This makes it very hard for security or border forces to find them without having to open and potentially compromise the contents.  But now, Cobalt Light Systems, a company spun out from research funded by the STFC have developed a device that can see through packaging and tell you exactly what is inside using a technique called Spatially Offset Raman Spectroscopy or SORS.  Professor Pavel Matousek developed this technique at the Rutherford Appleton Laboratories near Oxford. He's the Chief Scientific Officer at Cobalt Light Systems and he joins us now.  Hi, Pavel.  Thanks for joining us.

Pavel -   Hi, Helen.

Helen -   Well perhaps we'll just start off by saying, what is SORS? What is it and how does it work?

Pavel -   So, SORS is basically is a laser spectroscopy technique.  It's based around well-established technique called Raman Spectroscopy which provides a high chemical specificity or a high ability to accurately determine the chemical composition of a substance we are probing, but with a twist.  That twist, allows us to apply to a much wider range of containers which then, as a consequence, enables us to satisfy requirements of regulatory bodies for use of this technique at aviation security to determine the content of unopened bottles.

X-ray Luggage screening device at Suvarnabhumi International Airport, BangkokHelen -   So, what is it?  It's a type of laser light, is that right?

Pavel -   Indeed, so what we do is to shine a laser light onto the sample,  similar to a laser pointer, but slightly higher power.  When photons hit the sample, they scatter - most of them elastically, therefore they don't exchange energy with the material.  But a tiny, tiny fraction of these photons activate vibration within the molecules we are hitting.  And as a consequence, they lose the same amount of energy they use to activate the vibration motion and then as a consequence of that loss of energy, they change colour.  And a single molecule can have a number of energies which it can accept.  These are discreet and therefore, if you examine the spectrum of the photons which are emitted back at us from the sample, looking at the characteristic lines and different colours and their intensity pattern, we can determine as a fingerprint, what chemical component we are looking at. 

So, this is the basis of the Raman Spectroscopy technique.  The twist we are using is that we are actually not collecting the signal from the zone which is illuminated by the laser light, which you would do in conventional Raman Spectroscopy, because this would result in you being dazzled by the surface of the sample you are probing, for example, the container wall.  We probe several millimetres sideways, where we are seeing much more clearly the substance inside and we are not overwhelmed by the signal coming from the surface.  This is a situation similar, for example, to the stars in the sky.  In the day, you don't see them because you are dazzled by solar radiation.  However, if you wait long enough for the night, you can see stars clearly, or if you have a solar eclipse, you can see them clearly too.  In a similar way, we are going sideways and suppressing in effect the dazzling radiation coming from the surface.

Helen -   So in a sense, you're being able to see through the container into what's inside it.  How can you tell if something is actually dissolved in there, something that you're interested in or that security people are interested in?

Pavel -   Well, we basically examine that spectrum, that pattern of lines which we are detecting and that informs us about the content.  If we have a mixture, you would see the content of the solvent and solute very clearly.  So that's what we are doing and we are comparing those fingerprints against a library which holds prohibited substances which could be explosives. If an explosive is found, we will sound an alarm.  A unique feature of this technique is we reach extremely low false alarm rates.  So that means if you put a benign bottle into the system, the false alarm rate can be sounded in only half a percent of cases whereas conventional technology would have false alarm rates at least 10 times higher.  Therefore, disruption to airport operators is much, much lower.  This is an insignificant rate of false alarm if you like.

Helen -   So it's not going to set the alarms off when they shouldn't go off, but how sensitive is this as a technique?  Will it actually detect small quantities of the stuff that we're interested in?

Pavel -   It can certainly determine or detect the quantities which are relevant because trace quantities dissolved in something are not significant.  It can detect quantities maybe at a level of half a percent or 0.1 or 1%, but those are concentrations which are relevant for explosives to be viable.  And in security settings, this satisfies the requirements of the regulatory body, this instrument passes the so-called ECOCK test which is a European test which is required for this type of technology to be deployed at airports and passes with flying colours.

Helen -   And is this sort of technology something that we will see soon and is it quick enough that everyone can be tested, or is it going to be a case of still testing a sample of a number of people who come through security, or it will be a sort of a routine thing that we will all have?  Any liquid we have in our bags zapped by your machine and they will tell what's inside all our bags?

Pavel -   The speed of the machine is adequate to test every bottle which contains a significant amount of liquid.  The test itself takes 5 seconds, so the idea is you have the x-ray machine and if the x-ray machine identifies something suspect in your bag, they would take it out, put it inside the machine and our machine would verify that the content is benign or will sound alarm if there's an explosive found.

Helen -   And presumably, again, if terrorists and people who are trying to get these things through come up with some new molecule that isn't in the database then that's going to be a problem.  You'll have to keep up with the technology as that advances as well.

Pavel -   It's of course up to security authorities to maintain the library databases relevant to this indeed.  They would have to update the database as we go along in order to have an effective device or screening device.

Helen -   And finally, will this mean that we'll be allowed to take more liquids with us on the plane in the future?  So, no longer restricted to - is it 100 mls we're allowed now?

Pavel -   Indeed.  At the moment, it's 100 ml.  The planned anticipation is that this ban, or restriction would be lifted in April 2013 and we are expecting the final verdict on this by European Commission later this summer, we don't know whether this ban is going to be lifted in April whether it's going to be staged one year later.

Helen -   We'll wait to find out and I personally hope so because I always end up having to drink all my water before I go to security and that's...

Chris -   And then you want a wee all the way through the flight!.

Helen -   Exactly!  Thanks so much.  That was Professor Pavel Matousek from Cobalt Light Systems telling us all about SORS and how it could transform the way we experience going on an aeroplane.


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