Stand-off detection of explosives particles by multispectral imaging Raman spectroscopy (original) (raw)
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Standoff Raman Detection of Explosive Materials Using a Small Raman Spectroscopy System
Journal of Al-Nahrain University-Science, 2017
In this work a standoff Raman spectroscopy SRS system has been designed, assembled and tested for detecting explosives (Ammonium nitrate, Trinitrotoluene and Urea nitrate) in dark laboratory at 4 m target-telescope distance. The SRS system employs frequency doubled Nd:YAG laser at 532 nm excitation with laser power of 250 mW and integration time of 2 second. The Cassegrain telescope was coupled to the Ventana Raman spectrometer using a fiber optics cable, and Notch filter is used to reject Rayleigh scattering light. The Raman scattered light is collected by a telescope and then transferred via fiber optic to spectrometer and finally directed into charge coupled device CCD detector. In order to test SRS system, it has been used to detect the Raman spectra of Toxic Industrial Compounds TIC such as acetone, toluene, and carbon tetrachloride. The SRS results were compared with conventional Raman microscopy results using a bench top Bruker SENTERRA Raman instrument.
Applied Physics B, 2016
spectroscopies, which are considered as most appealing means. For instance, Raman spectroscopy [5, 11-25] and its coherent variants, coherent anti-Stokes Raman scattering (CARS) [26-32] and stimulated Raman scattering (SRS) [33] have been used for explosives detection over large or short distances. These methods, based on spontaneous or coherent Raman scattering, provide relatively sharp spectral features in a broad spectral range, leading to signatures that are strongly related to specific compounds and to their spatial distribution, and ultimately allowing explosives identification, even on strongly interfering surfaces. While standoff detection was mainly used for identification of bulk quantities of explosives or of single large particles, positioned on distant targets, the point and proximal detection focused on uncovering the presence of single particles or of particles residing from fingerprints. Detection of these residues on a variety of substrates (glass, metals and clothing) was achieved using integrated tabletop microscope-based Raman systems [20-22] or a homebuilt compact system [23-25]. These approaches were used not only for measurement of Raman spectra, but also for Raman imaging of explosives residues. Imaging was achieved by point-mapping, involving laser spot or sample raster-scanning through the x and y spatial dimensions, and resulting in successive Raman spectra at each particular x, y position. The drawback of this approach is that it is extremely time-consuming. Consequently, obtaining even moderate-size Raman images, while operating the system with short integration times for each measurement point, can take several hours [23]. For instance, mapping of a 1 × 1 cm sample of potassium nitrate (KNO 3) particles, with 50 μm steps, by the compact Raman spectrometer took 8 h [24]. Essentially, by photographing the sample, prior to data acquisition, it was possible to selectively monitor spatially resolved particles Abstract Measurements of Raman scattering spectra and of Raman maps of particles of explosives and related compounds [potassium nitrate, 2,4-dinitrotoluene (DNT), 2,4,6-trinitrotoluene (TNT) and 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX)] were performed by a homebuilt compact Raman system, functioning with a 532-nm laser beam, focused as a point or line, along with full vertical binning or image readout of an intensified charge-coupled device camera. High specificity and sensitivity were obtained by line-excitation, which allowed fast detection and mapping of explosive particles with a relatively simple system.
Detection of Trace Explosive Materials by Standoff Raman Spectroscopy System
Journal of Al-Nahrain University-Science, 2017
Standoff Raman spectroscopy SRS technique is one of the most powerful technologies that can identify trace amount of explosive materials. The Raman scattered signal collected by reflective telescope and a spectrograph is used to analyze the Raman scattered light. In order to view the spectrum, the spectrograph is equipped with charge coupled device CCD detector which allows detection of very weak stokes line. In order to test the capability of SRS system of detecting explosives trace, detection of C4 and AN explosives have been achieved with limit of detection (LOD) about 20 µg for C4 and 40 µg for AN.
Remote Raman and Infrared Spectroscopy Detection of High Explosives
The remote detection of highly energetic materials (HEM) based on vibrational spectroscopy is an important topic to include in the review of the classification, composition and properties of explosives. Infrared and Raman spectroscopies allow for the detection and remote identification of chemicals and biological threats and also enable the use of chemometrics for enhanced detection and discrimination. An IR system was configured by coupling an ―open path‖ FTIR interferometer to a reflective IR telescope (for passive detection) and to a telescope coupled mid-IR source (for active detection). The RRS instrument was built by fiber coupling a spectrograph to a reflective telescope. HEM samples were detected on stainless steel surfaces as thin films (50-3400 g/cm2) for IR experiments and as particles (3-85 mg) for Raman measurements. Nitroaromatic HEMs, including TNT, DNT and RDX; HEM formulations, including C4 and Semtex-H; inorganic HEM (ammonium nitrate) and acetone peroxides (TATP)...
Standoff laser-based spectroscopy for explosives detection
Electro-Optical Remote Sensing, Detection, and Photonic Technologies and Their Applications, 2007
Real-time detection and identification of explosives at a standoff distance is a major issue in efforts to develop defense against so-called improvised explosive devices (IED). It is recognized that the only method, which is potentially capable to standoff detection of minimal amounts of explosives is laser-based spectroscopy. LDS technique belongs to trace detection, namely to its micro-particles variety. It is based on commonly held belief that surface contamination was very difficult to avoid and could be exploited for standoff detection. We have applied gated Raman spectroscopy for detection of main explosive materials, both factory and homemade. We developed and tested a Raman system for the field remote detection and identification of minimal amounts of explosives on relevant surfaces at a distance of up to 30 m.
UV gated Raman spectroscopy for standoff detection of explosives
Optical Materials, 2008
Real-time detection and identification of explosives at a standoff distance is a major issue in efforts to develop defense against so-called improvised explosive devices (IED). It is recognized that the only method, which is potentially capable to standoff detection of minimal amounts of explosives is laser-based spectroscopy. LDS technique belongs to trace detection, namely to its micro-particles variety. It is based on commonly held belief that surface contamination was very difficult to avoid and could be exploited for standoff detection. We have applied gated Raman spectroscopy for detection of main explosive materials, both factory and homemade. We developed and tested a Raman system for the field remote detection and identification of minimal amounts of explosives on relevant surfaces at a distance of up to 30 m.
Classification of Raman Spectra to Detect Hidden Explosives
IEEE Geoscience and Remote Sensing Letters, 2000
Raman spectroscopy is a laser-based vibrational technique that can provide spectral signatures unique to a multitude of compounds. The technique is gaining widespread interest as a method for detecting hidden explosives due to its sensitivity and ease of use. In this letter, we present a computationally efficient classification scheme for accurate standoff identification of several common explosives using visible-range Raman spectroscopy. Using real measurements, we evaluate and modify a recent correlation-based approach to classify Raman spectra from various harmful and commonplace substances. The results show that the proposed approach can, at a distance of 30 m, or more, successfully classify measured Raman spectra from several explosive substances, including nitromethane, trinitrotoluene, dinitrotoluene, hydrogen peroxide, triacetone triperoxide, and ammonium nitrate.
Challenges, 2016
Surface-enhanced Raman spectroscopy (SERS) measurements of some common military explosives were performed with a table-top micro-Raman system integrated with a Serstech R785 miniaturized device, comprising a spectrometer and detector for near-infrared (NIR) laser excitation (785 nm). R785 was tested as the main component of a miniaturized SERS detector, designed for in situ and stand-alone sensing of molecules released at low concentrations, as could happen in the case of traces of explosives found in an illegal bomb factory, where solid microparticles of explosives could be released in the air and then collected on the sensor's surface, if placed near the factory, as a consequence of bomb preparation. SERS spectra were obtained, exciting samples in picogram quantities on specific substrates, starting from standard commercial solutions. The main vibrational features of each substance were clearly identified also in low quantities. The amount of the sampled substance was determined through the analysis of scanning electron microscope images, while the spectral resolution and the detector sensitivity were sufficiently high to clearly distinguish spectra belonging to different samples with an exposure time of 10 s. A principal component analysis procedure was applied to the experimental data to understand which are the main factors affecting spectra variation across different samples. The score plots for the first three principal components show that the examined explosive materials can be clearly classified on the basis of their SERS spectra.
Remote Raman spectroscopy of explosive precursors
Optical Engineering
Deep ultraviolet Raman spectroscopy measurements have been performed at the German Aerospace Center (DLR) with the aim of detecting traces (μg range) of explosive precursors. In this study, a backscattering Raman system was setup and optimized to detect urea, sodium perchlorate, ammonium nitrate, and sodium nitrate at a 60-cm short-range remote detection. The sample was tested at 264-nm ultraviolet laser excitation wavelength to experimentally observe any possible trace over textiles samples. For each colored sample textile, Raman spectra were acquired and no background fluorescence interference was observed at this laser excitation wavelength. Detection limits and system sensitivity with an acquisition time up to 3 s for microgram traces are presented. © The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.
Raman and photothermal spectroscopies for explosive detection
2013
Detection of explosive residues using portable devices for locating landmine and terrorist weapons must satisfy the application criteria of high reproducibility, specificity, sensitivity and fast response time. Vibrational spectroscopies such as Raman and infrared spectroscopies have demonstrated their potential to distinguish the members of the chemical family of more than 30 explosive materials. The characteristic chemical fingerprints in the spectra of these explosives stem from the unique bond structure of each compound. However, these spectroscopies, developed in the early sixties, suffer from a poor sensitivity. On the contrary, MEMS-based chemical sensors have shown to have very high sensitivity lowering the detection limit down to less than 1 picogram, (namely 10 part per trillion) using sensor platforms based on microcantilevers, plasmonics, or surface acoustic waves. The minimum amount of molecules that can be detected depends actually on the transducer size. The selectivity in MEMS sensors is usually realized using chemical modification of the active surface. However, the lack of sufficiently selective receptors that can be immobilized on MEMS sensors remains one of the most critical issues. Microcantilever based sensors offer an excellent opportunity to combine both the infrared photothermal spectroscopy in their static mode and the unique mass sensitivity in their dynamic mode. Optical sensors based on localized plasmon resonance can also take up the challenge of addressing the selectivity by monitoring the Surface Enhanced Raman spectrum down to few molecules. The operating conditions of these promising localized spectroscopies will be discussed in terms of reliability, compactness, data analysis and potential for mass deployment.