Abstract
We report the standoff (up to ~2 m) and remote (~8.5 m) detection of novel high energy materials/explosive molecules (Nitroimidazoles and Nitropyrazoles) using the technique of femtosecond laser induced breakdown spectroscopy (LIBS). We utilized two different collection systems (a) ME-OCT-0007 (commercially available) and (b) Schmidt-Cassegrain telescope for these experiments. In conjunction with LIBS data, principal component analysis was employed to discriminate/classify the explosives and the obtained results in both configurations are compared. Different aspects influencing the LIBS signal strength at far distances such as fluence at target, efficiency of collection system etc. are discussed.
Highlights
The development of rapid, reliable and real-time techniques to anticipate/dissolve the threats from nefarious elements by identifying high energy materials (HEMs), improvised explosive devices (IEDs) and special nuclear materials is a top priority for many nations to safeguard their citizens
We have investigated the feasibility of fs laser induced breakdown spectroscopy (LIBS) technique for explosives detection in two configurations i.e. standoff LIBS system (ST-LIBS) and remote LIBS (R-LIBS)
A decrease in the LIBS intensity with increase in standoff distance could be attributed to the different plasma generation conditions with interaction of filaments involved in certain cases
Summary
The development of rapid, reliable and real-time techniques to anticipate/dissolve the threats from nefarious elements by identifying high energy materials (HEMs), improvised explosive devices (IEDs) and special nuclear materials is a top priority for many nations to safeguard their citizens. Fs pulses are rewarding when compared to ns pulses for LIBS studies since these short laser pulses offer lesser Continuum, smaller heat effected zones, lesser plasma-ambiance interaction and ideally minimal plasma–plume interaction [38, 39] These pulses are ideal for remote/standoff detection as they can be formed into filaments through the phenomenon of filamentation and capable of delivering high energies over the long distances and has been used in atmospheric sensing [40, 41], cultural heritage monitoring [42], analyzing metals [43, 44], chemical and biological agents [45],organic samples [46], labeling of radioactive isotopes [47] and in detection of explosives [48, 49]. Results from both the configurations are compared and complexities in obtaining standoff LIBS spectra are addressed
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