Anna Pettersson

Laser-based standoff detection of explosives: a critical review

AbstractA review of standoff detection technologies for explosives has been made. The review is focused on trace detection methods (methods aiming to detect traces from handling explosives or the vapours surrounding an explosive charge due to the vapour pressure of the explosive) rather than bulk detection methods (methods aiming to detect the bulk explosive charge). The requirements for standoff detection technologies are discussed. The technologies discussed are mostly laser-based trace detection technologies, such as laser-induced-breakdown spectroscopy, Raman spectroscopy, laser-induced-fluorescence spectroscopy and IR spectroscopy but the bulk detection technologies millimetre wave imaging and terahertz spectroscopy are also discussed as a complement to the laser-based methods. The review includes novel techniques, not yet tested in realistic environments, more mature technologies which have been tested outdoors in realistic environments as well as the most mature millimetre wave imaging technique. FigureStandoff detection and identification is one of the most wanted capabilities

Explosives standoff detection using Raman spectroscopy: from bulk towards trace detection

This paper gives a brief overview on our latest progress in the area of standoff detection. Standoff Raman measurements from 200 m and 470 m distance have been performed on bulk amounts of TATP and AN respectively, the former through a double sided window, the latter under heavy rain. Resonance Raman measurements on TNT, DNT and NM vapors in the ppm concentration regime are presented, showing resonance enhancement in the range of 2 200 (NM) to 57 000 (TNT) as compared to 532 nm Raman cross sections. Finally, the application of hyper spectral Raman imaging is described, exemplified by the resolution of four different samples (sulphur, AN, DNT, and TNT) in the form of 5 mm wide discs in one single image.

Classification of Raman Spectra to Detect Hidden Explosives

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.

Possibilities for standoff Raman detection applications for explosives

This paper provides a brief overview of the Raman-based standoff detection methods developed at FOI for the purpose of standoff explosives detection. The methods concerned are Raman imaging for particle detection and Resonance Enhanced Raman Spectroscopy for vapor detection. These methods are today reaching a maturity level that makes it possible to consider applications such as trace residue field measurements, on site post blast analysis and other security of explosives related applications. The paper will look into future possible applications of these technologies. Our group has extensive activities in applications of the technology, among others in projects for the Seventh Framework Program of the European Union. Some of these possible applications will be described and a look into future development needs will be made. As far as possible, applicability will be discussed with a view on realistic explosives trace availability for detection. Necessary data to make such realistic applicability assessment is not always available and a brief discussion on the applicability of using the developed Raman technology to obtain this kind of data will also be made. The aspects of transitioning from research to practical applications, considering also eye-safety of the system, will be discussed as well.

Time-of-flight mass spectrometry for explosives trace detection

This paper presents the ongoing development of a laser ionization mass spectrometric system to be applied for screening for security related threat substances, specifically explosives. The system will be part of a larger security checkpoint system developed and demonstrated within the FP7 project EFFISEC to aid border police and customs at outer border checks. The laser ionization method of choice is SPI (single photon ionization), but the system also incorporates optional functionalities such as a cold trap and/or a particle concentrator to facilitate detection of minute amounts of explosives. The possibility of using jet-REMPI as a verification means is being scrutinized. Automated functionality and user friendliness is also considered in the demo system development.

Standoff Detection of Vapor and Trace Amounts of Explosives by Raman Technique

The large distances required pose several physical difficulties: The intensity of the return light decreases inversely with the distance squared, absorption losses in air (wavelength dependent) and scattering losses in air (wavelength dependent).

Real-Time Detection of IED Explosives with Laser Ionization Mass Spectrometry

The ESSEX system (Extremely Sensitive and Selective Explo- sives detector) is a system that can be used for standoff or remote detection of suicide bombers at a distance of up to a few meters via the trace amounts of explosives present in vapor phase around explosives with a high vapor pressure. The ESSEX detection method is based on laser ionization mass spectrometry (LI-MS). Direct sampling of air with explosives in vapor phase will allow detection of explosives with relatively high vapor pressure, such as TATP (suspected to have been used in the recent suicide bombings in Lon- don as well as numerous suicide bombings in Israel) and EGDN (normally found in dynamite explosives such as the ones used in the Madrid bomb- ings). The LI-MS method has a potential to detect all or nearly all explosives. For explosives with low vapor pressure (e.g. RDX, HMX, PETN, AN) it is probably necessary to sample particles as well. Other aspects of the future potential for this method are that the number of explosives that the method targets can be increased as needed. The method is very suited for data fusion and processing, making it possible to incorporate artificial intelligence (AI) into the system. The uniqueness of LI-MS methods lies in its low detection limit, possibility of real-time detection, its versatility regarding the number of possible substances to detect and its unique selectivity, leading to very few false alarms. The ESSEX concept is appropriate for indoor and outdoor applications, it is benign to humans and property and can be applied in an unnoticeable way. Laser ionization mass spectrometry and specifically reso- nance enhanced multi photon ionization (REMPI) is an ultra-sensitive, highly selective analytical technique that can identify and quantify vapor-phase con- stituents at parts-per-trillion (ppt) levels. The REMPI technique combines the principles of optical spectroscopy and mass spectrometry to provide a two- dimensional detection scheme that yields a high degree of chemical sensitivity