The Development of a Semtex-H Simulant for Terahertz Spectroscopy

The development and use of terahertz (THz) frequency spectroscopy systems for security screening has shown an increased growth over the past 15 years. In order to test these systems in real-world situations, safe simulants of illicit materials, such as Semtex-H, are required. Ideally, simulants should mimic key features of the material of interest, such that they at least resemble or even appear indistinguishable from the materials of interest to the interrogating technique(s), whilst not having hazardous or illicit properties. An ideal simulant should have similar physical properties (malleability, density, surface energy and volatility to the material of interest); be non-toxic and easy to clean and decontaminate from surfaces; be recyclable or disposable; and be useable in a public environment. Here, we present a method for developing such an explosive simulant (for Semtex-H) based on a database of THz spectra of common organic molecules, and the use of a genetic algorithm to select a mixture of compounds automatically to form such a simulant. Whilst we focus on a security application, this work could be applied to various other contexts, where the material of interest is dangerous, impractical or costly. We propose four mixtures that could then be used to test the spectral response of any instrument, working at terahertz frequencies, without the need for an explosive substance

Explosive Detection Equipment and Technology for Border Security

This report contains a brief survey of Explosives Detection Technology,as it is applied for inspection of goods and passengers at borders, and explains the role of European legislation and the European Commission¿s research programs in this field. It describes the techniques of trace and bulk explosives detection that are in use, the latest techniques that are in development and the characteristics of explosives that are, or might be, used to provide a signature for exploitation in detection technology. References to academic reviews are included for those wishing to study the subject in greater depth. Some additional details are given concerning plastic and liquid explosives, which are a threat of particular current importance. The report also contains a brief account of relevant European trade, safety and security legislation, a description of recent policy initiatives and tables of related European Commission funded research projects. Contact details of commercial companies selling explosive detection products are also provided.JRC.G.6-Sensors, radar technologies and cybersecurit

Advantages and limitations of spectroscopic, chromatographic and electrophoretic methods for the characterisation of synthetic cannabinoids and synthetic cathinone derivatives

Over the last decade new psychoactive substances (NPS) flooded Europe and the challenging task for drug law enforcement is how to effectively respond to the dynamically and constantly changing drug market. NPS are regarded as legal alternatives to internationally controlled drugs of abuse. NPS are sold via the internet as, inter alia, “designer drugs”, “legal highs”, or “bath salts” in colourful and professionally designed packages mixed with herbal products or as pure powder. There is a persisting race between the legal prosecution and the producers of designer drugs as those strive to be one step ahead by rapidly generating new NPS products in reaction to new legislative measures. The rapid emergence of novel products means that developing and maintaining selective analytical methods and reference standards is challenging. Beside laboratory methods, the demand for portable analytics is high given the versatile distribution channels and the related particular risk for public institutions handling these products including postal delivery facilities, custom controls and prisons. In this thesis, new analytical methods were developed for the detection of synthetic cannabinoids and synthetic cathinones, the most frequently seized NPS subgroups. An ion mobility spectrometry (IMS) method was developed as an in-field alternative presumptive test for the non-destructive and selective detection of NPS in different matrices by wiping the surface of a sample with a swab. The suitability of the method for on-site analysis was demonstrated in a prison in Rhineland-Palatinate. The contactless and non-destructive detection of NPS was investigated using THz radiation for the first time. Fast characterisation of newly emerged and unknown substances was examined using portable and laboratory-based Raman spectrometers. Data analysis used a combination of a newly developed principal component analysis model and frequency tables. In addition, it was shown, that the analysis of herbal mixtures was possible using a simple solid/liquid extraction followed by precipitation of the synthetic cannabinoid constituents. New laboratory methods were developed to complement the screening techniques. The possibility to quantify NPS via the calibration curves of a small set of NPS, for which reference material is commercially available was demonstrated and validated via the analysis of seizures using ultra-performance liquid chromatography-diode array detection. Finally, capillary electrophoresis-diode array detection with a chiral selector was used for the chiral discrimination of NPS in the form of a general unknown screening method for mixtures and bulking agents on the one hand and a high throughput method for the fast analysis of single substances on the other hand. With the methods developed here, the analytical portfolio of NPS drug analysis was greatly expanded to meet the challenges of the dynamically and constantly changing drug market. All methods were successfully applied to real samples and partly in routine analysis in different criminal investigations offices and in public institutions (Wittlich prison)

Scanning the issue: T-ray imaging, sensing, and retection

Copyright © 2007 IEEEDerek Abbott, Xi-Cheng Zhan

High-spectral-resolution terahertz imaging with a quantum-cascade laser

We report on a high-spectral-resolution terahertz imaging system operating with a multi-mode quantum-cascade laser (QCL), a fast scanning mirror, and a sensitive Ge:Ga detector. By tuning the frequency of the QCL, several spectra can be recorded in 1.5 s during the scan through a gas cell filled with methanol (CH3OH). These experiments yield information about the local absorption and the linewidth. Measurements with a faster frame rate of up to 3 Hz allow for the dynamic observation of CH3OH gas leaking from a terahertz-transparent tube into the evacuated cell. In addition to the relative absorption, the local pressure is mapped by exploiting the effect of pressure broadening

Realization of Circular Slot Frequency Selective Surfaces using Photoplotter and Wet Etching Technique for Terahertz Material Sensing Applications

This paper discusses on the analysis of band pass Frequency Selective Surfaces (FSS) for performance enhancement in material sensing application. Terahertz Spectroscopy has proved to be versatile tool for detection and sensing in measuring non-conductive materials. It is because most of the non-conductive materials have unique molecular resonance that may translate as transmission and absorption of signals within terahertz range. However, the most critical issue in detection and sensing is to improve its sensitivity therefore an extremely low concentration material still can be able to be detected in THz band. Hence, in this paper, a circular slot is modeled on a planar structure of Rogers Duroid 5880LZ substrate with thickness of 508µm using Computer Simulation Technology (CST). The simulation generates a band pass response with transmission magnitude of 0.95 at 0.66THz. Furthermore, photoplotter and wet etching fabrication process is used for the realization of terahertz FSS. Simulated and measured transmission shows a good agreement between 0.5THz to 0.7THz as only 1% shifts in frequency between simulated and measured results. Besides that, the fabrication of circular FSS shows narrower measured bandwidth as compared to its simulated counterpart. Hence, with the limitation of the wet etching to produce micron size structure both simulation and measured result shows good agreement for all the critical issues in this study

A review of Terahertz technology and Metamaterial based electromagnetic absorber at Terahertz band

 Terahertz (THz) technology, a new step towards the wireless communication is a recent topic of research. THz radiation has unique properties which make it better than microwaves, infrared, X-rays, etc. These radiations have wide applications in various fields like imaging, spectroscopy, security, biomedicine, sub-millimeter astronomy, in communication, etc. THz radiation sources and detectors play a vital role in the THz communication system.  The sources and detectors for THz radiation are still in a developing stage. As in naturally occurring materials, there is lack of good terahertz characteristic, so researchers are moving towards artificial one, i.e., the metamaterial based design. Metamaterial based design of generation and detection of THz radiation is the recent demands in the field of THz communication. Hence, we are focussing on the metamaterial based terahertz transmitter and receiver. So in this paper, a brief study of the THz technology based on metamaterial has been carried out and presented here