Sheffield detector

Sheffield explosive-detector reaches second milestone

The Mid-IR CERPAS project, funded by Find A Better Way and based at the University of Sheffield, is an extremely sensitive explosive detector that looks for trace amounts of explosive material in the air above buried landmines. After seven months since the project launch the team, led by Dr Michael Hippler, has passed the second of six milestones and is on course for a good result at the project completion in Q4 of 2018.

Even when buried, explosive materials emit tiny amounts of particles into the atmosphere – an estimated 5 parts per billion for TNT, for example. Though a tiny amount, this is still enough for the Sheffield device to detect which it does by acting as a sort of artificial nose.

The device works by pumping an air sample into a chamber and then firing a laser beam inside it, which is tuned to the exact frequency that TNT particles will absorb. This absorption creates a vibration that is picked up by a tiny microphone – once the sound is heard the device can confirm explosive material is nearby. To make the device more sensitive, the laser beam is passed between a set of highly reflective mirrors that ‘trap’ the beam, causing it to go back and forth thousands of times, increasing the chances of a laser coming into contact with a TNT molecule.

When developed into a portable device, the Mid-IR CERPAS detector could have some notable advantages over other detector types. By not using electromagnetic waves as metal detectors or ground penetrating radar devices do, there is no problem with interference from mineral-rich or wet soil. It is also hoped that the Mid-IR CERPAS device will benefit from a very low false-alarm rate as, unlike metal, TNT and other explosive materials are only present in landmines and unexploded ordinance.

Trying to ‘sniff’ for explosive material is already established practice for humanitarian demining, mostly by trained dogs. The ability of dogs to smell explosive material can be limited by climate, attention spans, and other distractions, however.

Other artificial nose technology devices are in development, but these are searching for chemical by-products of explosive material. The Mid-IR CERPAS device detects explosive material directly. Once operational it is hoped the Mid-IR CERPAS will be more durable and reliable than canine detectors, and more accurate than other artificial nose devices.

Using technology previously developed for the Home Office for use in airports, the Sheffield team now have a working detector in their laboratory. The next eighteen months will be spent redesigning the detector, making it smaller and more durable, resulting in a field-deployable apparatus.

Speaking of the Sheffield team’s progress, Find A Better Way CEO Lou McGrath commented, ‘We are hoping that this technology will add another detection option to the deminers toolkit and if it can be developed into a detector that is robust yet light as well as cost effective, then I am certain it will have a distinct advantage for the humanitarian mine clearance sector.’