Optical stand-off detection of explosives and improvised explosive devices - OFDEX

The Fraunhofer Society pooled its know-how in the fields of explosives, laser spectroscopy, semiconductor-laser design and system integration in order to develop optical technologies for the stand-off detection of explosives. Within the framework of a comprehensive research and development project called OFDEX, four Fraunhofer institutes are working jointly towards the development of a demonstrator remote detection system. Many explosives can be detected because they exude gas which may form a "vapour cloud" (plume) above a potential assassin. Moreover, as most explosives are absorbed well by surfaces of many kinds, it is likely that persons (e.g. their clothing) or parts of cars (e.g. door handles) will be contaminated, a fact that is similarly useful in remote detection. For both detection scenarios (gas phase and traces on surfaces) very small quantities of explosives must be detected. However, the concentrations necessary in practice are largely unknown. Using experimental methods and mathematical modelling, the Fraunhofer ICT aims to determine the dispersion of explosive gases and particle traces. Particular emphasis is placed on the dispersion behaviour of the substances used in so-called Improvised Explosive Devices (IEDs). The Fraunhofer IAF developed a new type of spectrally-tunable quantum cascade (QC) laser modules, which enables an increase of the tuning range by at least one order of magnitude in comparison to the established current-temperature tuning techniques. With the QC laser module it is possible to detect surface contaminations of around 10 µg/cm2 TNT performing imaging backscattering spectroscopy. The Fraunhofer IPM achieves a detection limit of 5 ppm*m for TATP-detection in the gas phase with a special measurement set-up. The Fraunhofer ILT is able to detect ANFO and TNT at surface coverage levels of 100 µg/cm2 against backgrounds of both organic and inorganic materials with remote Raman spectroscopy.