Standoff Detection Of Explosives Research Articles

Raman spectroscopic and advanced signal processing analyses for real time standoff detection and identification of explosives

Laser Raman spectroscopy is a powerful instrument commonly used for detection of bulk and trace amounts of explosives. The work carried out in this paper is divided into two phases; the first phase is to propose a real time standoff explosive detection and identification system based on Raman spectroscopy that can be deployed in static checkpoints. The measurement is performed for samples placed in contact and at distances up to 1 m in ambient light conditions. The second phase is to propose a novel sophisticated signal processing and pattern recognition techniques for accurate identification and classification of the investigated materials.

Double-pulse stand-off explosive vapour detection system for flexible perilous materials

The paper presents the analyses of explosive material sensors. Sensors are described and assigned to the X and radiation, optical radiation sensors, as well as detectors applied in gas chromatography, electrochemical and chemical sensors. Furthermore, neutron techniques and magnetic resonance devices were analysed; the particular attention of the optoelectronic sensors of explosive devices. These robots used in the military applications employed with the integrated system, including video screens, sensors, gripper and cameras. The fighting robots also have different shapes according to the purposes of each robot. Here, the new system is proposed with the help of low power Zigbee wireless sensor network to trace out the intruders (unknown persons) and the robot will take the necessary action automatically. Thus, the proposed system, an intelligent unmanned robot (IUR) using Zigbee saves human life and reduces manual error in defence side. The specially designed robotic system to preserve human life and protects the country from enemies.

Standoff Detection and Identification of Explosives and Hazardous Chemicals in Simulated Real Field Scenario using Time Gated Raman Spectroscopy

The detection of hazardous chemicals, explosives, improvised explosive materials, energetic materials and their associated compounds for security screening, forensic applications and detection of unexploded ordnance is an active area of research. The results based on comprehensive experimental study and performance of time gated Raman spectroscopy (TGRS) for stand-off detection of explosives and hazardous chemicals under realistic scenario are presented. Representative results drawn from the experimental study for detection of explosives and hazardous chemicals in simulated real field scenario are given.

Arctic counterterrorism: can Arctic cooperation overcome its most divisive challenge yet?

ABSTRACT This article examines the potential for international cooperation in Arctic counterterrorism. Focus is on cooperation involving Russia and its immediate Arctic neighbours, the United States and Norway. The article discusses the evolution of hard security cooperation in the Arctic through freezes and thaws in international relations. It further discusses cooperation between Russia and NATO in the global war on terror, and how this common cause turned into a core for contention. The article draws attention to two fundamental and critical impediments to international cooperation in Arctic counterterrorism: aversion to information sharing and the problem of labelling terrorists. Throughout its discussions, the article illustrates lingering trust issues between Russia and its Western neighbours. This mistrust underscores challenges to hard security cooperation among the Arctic states in general, and to cooperation in the highly politicised field of counterterrorism in particular. Abbreviation: NATO: North Atlantic Treaty Organization; OSCE: Organization for Security and Co-operation in Europe; CSIS: Center for Strategic and International Studies; SAR: search and rescue; OSR: oil spill response; STANDEX: Stand-off Detection of Explosives; CAI: Cooperative Airspace Initiative; US: United States, HQ: headquarters; UN: United Nations, ISIS: Islamic State of Iraq and Syria

Real-time stand-off detection of improvised explosive materials using time-gated UV–Raman spectroscopy

A transportable, trolley-mounted stand-off explosive material detection system based on the time-gated Raman spectroscopy was developed and tested in our laboratory. This system is capable of identifying the explosives and improvised explosive materials located up to a distance of 30 m. A frequency tripled Nd:YAG, nanosecond pulsed laser (355 nm, 6 ns) operated at 10 Hz was used as an excitation source to induce Raman spectra of explosive materials under investigation. A reflected type 200 mm aperture telescope designed using Zemax optical design software was used to collect the backscattered Raman signals. Raman signals were recorded using the gated intensified charge coupled device (ICCD) spectrograph. A LabVIEW-based data acquisition and analysis software for real-time identification of materials was developed and used. It gives audio as well as text alarm to the operator about threat identification.

Standoff Detection of Explosives at 1 m using Laser Induced Breakdown Spectroscopy

<p class="p1">We report the ‘standoff detection’ of explosives at 1 m in laboratory conditions, for the first time in India, using Laser Induced Breakdown Spectroscopy combined with multivariate analysis. The spectra of a set of five secondary explosives were recorded at a distance of 1 m from the focusing as well as collection optics. The plasma characteristics viz., plasma temperature and electron density were estimated from Boltzmann statistics and Stark broadening respectively. Plasma temperature was estimated to be of the order of (10.9 ± 2.1) .103 K and electron density of (3.9 ± 0.5) .1016 cm-3. Using a ratiometric approach, C/H and H/O ratios showed a good correlation with the actual stoichiometric ratios and a partial identification success could be achieved. Finally employing principle component analysis, an excellent classification could be attained.<span class="Apple-converted-space"> </span></p>

Nonlinear Electromagnetic Interactions in Energetic Materials

We study the scattering of electromagnetic waves in anisotropic energetic materials. Nonlinear light-matter interactions in molecular crystals result in frequency-conversion and polarization changes. Applied electromagnetic fields of moderate intensity can induce these nonlinear effects without triggering chemical decomposition, offering a mechanism for non-ionizing identification of explosives. We use molecular dynamics simulations to compute such two-dimensional Raman spectra in the terahertz range for planar slabs made of PETN and ammonium nitrate. We discuss third-harmonic generation and polarization-conversion processes in such materials. These observed far-field spectral features of the reflected or transmitted light may serve as an alternative tool for stand-off explosive detection.

Standoff detection of explosives and buried landmines using fluorescent bacterial sensor cells

A standoff detection scheme for buried landmines and concealed explosive charges is presented. The detection procedure consists of the following: Live bacterial sensor strains, genetically engineered to produce a dose-dependent amount of green fluorescent protein (GFP) in the presence of explosives' vapors, are encapsulated and spread on the suspected area. The fluorescence produced by the bacteria in response to traces of the explosive material in their microenvironment is remotely detected by a phase-locked optoelectronic sampling system.This scheme enables fast direct access to a large minefield area, while obviating the need to endanger personnel and equipment. Moreover, the employment of phase locking detection efficiently isolates the bacterial sensors' fluorescent output from the background optical signals. This facilitates the application of bacterial sensors in an outdoor environment, where control of background illumination is not possible. Using this system, we demonstrate standoff detection of 2,4-DNT both in aqueous solution and when buried in soil, by sensor bacteria either in liquid culture or agar-immobilized, respectively, at a distance of 50m in a realistic optically noisy environment.

Review of explosive detection methodologies and the emergence of standoff deep UV resonance Raman

Due to terrorist use of explosive devices, intense interest has been directed towards the development of techniques and instrumentation to detect explosives. A number of analytical techniques are currently under investigation for trace explosive detection. Several methods have been successfully commercialized including colorimetric kits, fluorescence quenching sensors, and ion mobility spectrometers that see widespread field use. A key limitation of all currently utilized field techniques is that they require close proximity or physical interaction with the object being analyzed. The ideal trace explosive detection technique would be able to detect trace amounts of explosives from a distance to ensure personnel safety. Laser‐based spectroscopies are the only currently viable techniques that can be utilized to sense trace amounts of explosives at standoff distances. This review compares currently used explosive detection techniques with recently developed standoff methods. We emphasize the development of UV resonance Raman spectroscopy for standoff explosive detection. This work has recently been enabled by advances in laser and spectrometer design. Trace explosive detection has also been advanced by the recently developed understanding of deep UV photochemistry for several explosive molecules. Copyright © 2016 John Wiley & Sons, Ltd.

On the Thermomechanical Response of HTPB-Based Composite Beams Under Near-Resonant Excitation

Currently, there is a pressing need to detect and identify explosive materials in both military and civilian settings. While these energetic materials vary widely in both form and composition, many traditional explosives consist of a polymeric binder material with embedded energetic crystals. Interestingly, many polymers exhibit considerable self-heating when subjected to harmonic loading, and the vapor pressures of many explosives exhibit a strong dependence on temperature. In light of these facts, thermomechanics represent an intriguing pathway for the stand-off detection of explosives, as the thermal signatures attributable to motion-induced heating may allow target energetic materials to be distinguished from their more innocuous counterparts. In the present work, the thermomechanical response of a sample from this class of materials is studied in depth. Despite the nature of the material as a polymer-based particulate composite, classical Euler–Bernoulli beam theory, along with the complex modulus representation for linear viscoelastic materials, was observed to yield predictions of the thermal and mechanical responses in agreement with experimental investigations. The results of the experiments conducted using a hydroxyl-terminated polybutadiene (HTPB) beam with embedded ammonium chloride (NH4Cl) crystals are presented. Multiple excitation levels are employed and the results are subsequently compared to the work's analytical findings.

Nanosecond Gated Raman Spectroscopy for Standoff Detection of Hazardous Materials

Laser Raman spectroscopy is one of the most powerful technologies for standoff detection of hazardous materials including explosives. Supported by recent development of laser and sensitive ICCD camera, the technology can identify trace amount of unknown substances in a distance. Using this concept, we built a standoff detection system, in which nanosecond pulse laser and nanosecond gating ICCD technique were delicately devised to avoid the large background noise which suppressed weak Raman signals from the target sample. In standoff detection of explosives which have large kill radius, one of the most important technical issues is the detection distance from the target. Hence, we focused to increase the detection distance up to 54 m by careful optimization of optics and laser settings. The Raman spectra of hazardous materials observed at the distance of 54 m were fully identifiable. We succeeded to detect and identify eleven hazardous materials of liquid or solid particles, which were either explosives or chemical substances used frequently in chemical plants. We also performed experiments to establish the limit of detection (LOD) of HMX at 10 m, which was estimated to be 6 mg.

Estimation of the Efficiency of Stand-Off Detection of Traces of Explosives by the Method of Active Formation of Spectral Images Using a Tunable Co2 Laser

A method of active formation of spectral images promising for stand-off detection of explosives is considered. The capabilities of the method in the IR range with the use of a tunable CO2 laser and a thermal imaging receiver are estimated. It is suggested to estimate the efficiency of detection of substances based on their spectral features and difference between the spectra of substances and substrate materials. Results of calculations are presented.

Quantum cascade lasers (QCL) for active hyperspectral imaging

Abstract There is an increasing demand for wavelength agile laser sources covering the mid-infrared (MIR, 3.5–12 µm) wavelength range, among others in active imaging. The MIR range comprises a particularly interesting part of the electromagnetic spectrum for active hyperspectral imaging applications, due to the fact that the characteristic ‘fingerprint’ absorption spectra of many chemical compounds lie in that range. Conventional semiconductor diode laser technology runs out of steam at such long wavelengths. For many applications, MIR coherent light sources based on solid state lasers in combination with optical parametric oscillators are too complex and thus bulky and expensive. In contrast, quantum cascade lasers (QCLs) constitute a class of very compact and robust semiconductor-based lasers, which are able to cover the mentioned wavelength range using the same semiconductor material system. In this tutorial, a brief review will be given on the state-of-the-art of QCL technology. Special emphasis will be addressed on QCL variants with well-defined spectral properties and spectral tunability. As an example for the use of wavelength agile QCL for active hyperspectral imaging, stand-off detection of explosives based on imaging backscattering laser spectroscopy will be discussed.

Communication: Two-dimensional gas-phase coherent anti-Stokes Raman spectroscopy (2D-CARS): Simultaneous planar imaging and multiplex spectroscopy in a single laser shot

Coherent anti-Stokes Raman spectroscopy (CARS) has been widely used as a powerful tool for chemical sensing, molecular dynamics measurements, and rovibrational spectroscopy since its development over 30 years ago, finding use in fields of study as diverse as combustion diagnostics, cell biology, plasma physics, and the standoff detection of explosives. The capability for acquiring resolved CARS spectra in multiple spatial dimensions within a single laser shot has been a long-standing goal for the study of dynamical processes, but has proven elusive because of both phase-matching and detection considerations. Here, by combining new phase matching and detection schemes with the high efficiency of femtosecond excitation of Raman coherences, we introduce a technique for single-shot two-dimensional (2D) spatial measurements of gas phase CARS spectra. We demonstrate a spectrometer enabling both 2D plane imaging and spectroscopy simultaneously, and present the instantaneous measurement of 15,000 spatially correlated rotational CARS spectra in N2 and air over a 2D field of 40 mm(2).

Comparison of Visible and Near-Infrared Raman Cross-Sections of Explosives in Solution and in the Solid State

Raman cross-sections of explosives in solution and in the solid state have been measured using visible and near-infrared excitation via secondary calibration. These measurements are valuable for both fundamental scientific purposes and applications in the standoff detection of explosives. The explosive compounds RDX, HMX, TNT, 2,4-DNT, 2,6-DNT, and ammonium nitrate were measured using discrete excitation wavelengths ranging from 532 nm to 785 nm. A comparison of the spectral features and cross-sections between the solid state and solution was performed. Comparison is also made to cross-sections measured with deep ultraviolet excitation.

Standoff detection of explosives with external cavity quantum cascade lasers

Standoff detection of explosives with external cavity quantum cascade lasers

Remote Explosives Detection (RED) by Infrared Photothermal Imaging

ABSTRACTRED is a technique we have developed for stand-off detection of trace explosives using infrared (IR) photo-thermal imaging [1,2,3]. RED incorporates compact IR quantum cascade lasers tuned to strong characteristic absorption bands and may be used to illuminate explosives present as particles on a surface. An IR focal plane array is used to image the surface and detect any small increase in the thermal emission upon laser illumination. We have previously demonstrated the technique at several meters to 10’s of meters of stand-off distance indoors and in field tests [4,5], while operating the lasers below the eye-safe intensity limit (100 mWcm2) [6]. Sensitivity to traces of explosives as small as a nanogram has been demonstrated. By varying the incident wavelength slightly, we can readily show selectivity between individual explosives such as TNT and RDX. Using a sequence of lasers at different wavelengths, we increase both sensitivity and selectivity. A complete detection protocol can be performed in a sub-second time domain. More recently, RED has been used to emphasize measurements with cooled detectors in addition to examining the utility of filtering the collected thermal emission signal which is rich in analyte-specific spectroscopic information. A next generation RED system and detection algorithm is being developed to take advantage of these more powerful features. This manuscript will include an overview of the approach and recent experimental results.

Use of the Gerchberg–Saxton algorithm in optimal coherent anti-Stokes Raman spectroscopy

We are utilizing recent advances in ultrafast laser technology and recent discoveries in optimal shaping of laser pulses to significantly enhance the stand-off detection of explosives via control of molecular processes at the quantum level. Optimal dynamic detection of explosives is a method whereby the selectivity and sensitivity of any of a number of nonlinear spectroscopic methods are enhanced using optimal shaping of ultrafast laser pulses. We have recently investigated the Gerchberg-Saxton algorithm as a method to very quickly estimate the optimal spectral phase for a given analyte from its spontaneous Raman spectrum and the ultrafast laser pulse spectrum. Results for obtaining selective coherent anti-Stokes Raman spectra (CARS) for an analyte in a mixture, while suppressing the CARS signals from the other mixture components, are compared for the Gerchberg-Saxton method versus previously obtained results from closed-loop machine-learning optimization using evolutionary strategies.

New Raman–Laser-Induced Breakdown Spectroscopy Identity of Explosives Using Parametric Data Fusion on an Integrated Sensing Platform

The principal goal of sensors for the detection of explosives is to establish the identity of the interrogated target as a key to threat assessment and decision making. Despite the fact that both Raman spectroscopy and laser-induced breakdown spectroscopy (LIBS) have shown their capability in standoff detection of explosives, such techniques are not exempt from certain limitations, in terms of sensitivity and selectivity, to carry out this purpose when they are used individually. For this reason, the idea for the fusion of data reported by these orthogonal techniques, Raman and LIBS, has been around for a while. The present manuscript proposes an approach for the combination of the spectral outputs of Raman and LIBS sensors (data fusion strategy) in order to obtain knowledge about the identity of compounds better than that achieved when each technique acts alone. After simple mathematical treatment, a new pattern of identification (two-dimensional, 2D, image) of several compounds (explosives, confusants, and supports) was generated from the assembly of their Raman and LIBS spectra. The efficiency of this strategy was evaluated by comparing the results obtained for differentiation between compounds using simple correlation coefficient values from the 2D images and those achieved using Raman and LIBS spectra separately. Additionally, the effect of two spectral pretreatments (autoscaling and normalization) on the generation of the 2D image was evaluated. The results derived from this study demonstrate that the 2D image improves the identification of compounds, mainly in those critical situations in which it is not easy to differentiate them when Raman spectroscopy or LIBS is used separately.

Deep Ultraviolet Resonance Raman Excitation Enables Explosives Detection

We measured the 229 nm absolute ultraviolet (UV) Raman cross-sections of the explosives trinitrotoluene (TNT), pentaerythritol tetranitrate (PETN), cyclotrimethylene-trinitramine (RDX), the chemically related nitroamine explosive HMX, and ammonium nitrate in solution. The 229 nm Raman cross-sections are 1000-fold greater than those excited in the near-infrared and visible spectral regions. Deep UV resonance Raman spectroscopy enables detection of explosives at parts-per-billion (ppb) concentrations and may prove useful for stand-off spectroscopic detection of explosives.