Extension of the p-Spectrum Method to the Higher Frequencies

N. Palka
Institute of Optoelectronics, Military University of Technology, S. Kaliskiego 2, 00-908 Warsaw, Poland

Abstact
The p-spectrum method is a time domain spectroscopy-based technique for re flection analysis of materials (including explosives) that takes into account only part of the re flected signal, which is next analyzed via the Fourier transform. The method is limited to the frequencies of about 1.8 THz due to the pulse properties of our time domain spectroscopy setup. In this paper we theoretically prove that application of a shorter pulse can increase this frequency range up to 2.2 THz, that enables analysis of penthrite and octogen, two important explosives.

ACTA PHYSICA POLONICA A Vol. 124(3) 543 (2013)

..........The proposed TDS-based p-spectrum method uses an external free standing module with a fiber-fed emitter and detector (Fig. 1a). This module is connected to the core unit of the Spectra 3000 from Teraview Company by means of optical fibers. The THz beam thanks to a set of the o -axis parabolic and at mirrors is focused on the sample and after specular re flection is collected and focused on the detector.   ..............

see full paper at http://przyrbwn.icm.edu.pl/APP/PDF/124/a124z3p40.pdf

Experimental Explosive Characterization for Counterterrorist Investigation

D. Etayo, 

I. Maestrojuan, 

J. Teniente, 

I. Ederra, 

R. Gonzalo

Abstract

A THz spectral characterization of different explosives of special interest for the Spanish National Security Forces “Guardia Civil” is presented in this paper. This forensic analysis has been done in the frequency range from 0.060 THz to 3.5 THz using the Teraview TPS Spectra 3000 system in laboratory conditions. With this equipment the refractive index, absorbance and complex permittivity of the explosive samples have been obtained. In this study, some of the most common used explosives (Bullet gunpowder, mine gunpowder, PETN, TNT, RDX) are analysed paying special attention to differences related to the manufacturing process used to elaborate some of them and to the purity of the samples. The different fabrication processes of the explosives lead to the same spectral behaviour and characteristics. At the same time, the inclusion of some additives in the explosive samples does not alter their main electromagnetic properties. The sensitivity limit of the measurement system has been found to be to 10 mg of explosives. These results will be used to design future THz imaging systems that allow to detect and identify them in security and defence applications and/or to complete laboratory studies after a terrorist action.

Detection of covered materials in the TDS-THz setup

Proc. SPIE 8716, Terahertz Physics, Devices, and Systems VII: Advanced Applications in Industry and Defense, 871608 (May 31, 2013); 
doi:10.1117/12.2015373

Authors:
Norbert Palka
Military Univ. of Technology (Poland)

More details at: http://proceedings.spiedigitallibrary.org/proceeding.aspx?articleid=1693464

Abstract

We report on a new method for extracting the characteristic features of covered materials, including Hexogen, in the range 0.5–1.8 THz. This time domain spectroscopy-based technique takes into account only part of the signal reflected from a covered sample, and analyzes it by Fourier transform. The obtained power spectrum has distinctive peaks that correspond to peaks measured in the transmission configuration and can be applied for further identification. We showed results obtained for the samples of hexogen, lactose, and tartaric acid covered with commonly used packaging materials such as plastic, foil, paper and cotton. © (2013) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

Topics
Fourier transforms ; Packaging ; Spectroscopy ; Terahertz radiation

In 2011 TeraView supplied two TPS Spectra 3000 systems with a stand-off explosives detection module and a fibre-fed scanning system with multiple gantry options for research into terahertz imaging and non-destructive testing. Military University of Technology (MUT) in Poland is one of the country’s most prestigious research institutes for terahertz research and materials characterisation. Read more...

Terahertz spectra of materials measured by the OPO-based system

Proc. SPIE 8716, Terahertz Physics, Devices, and Systems VII: Advanced Applications in Industry and Defense, 87160Y (May 31, 2013); doi:10.1117/12.2015375

Authors: 
Michał J. Walczakowski, Norbert Palka, Przemyslaw Zagrajek, Mieczyslaw Szustakowski

Military Univ. of Technology (Poland)

Abstract

We report on measurements of transmission spectra of chosen materials (Hexogen, sugar, L-tartaric acid, 4-aminobenzoic acid) in the range 0.7-2.0 THz. The measurements were carried out by means of a setup, which bases on the optical parametric oscillator (OPO) combined with the hot electron bolometer (HEB). The setup consists of the commercially available tunable OPO working in the range 0.7-2.0 THz with repetition rate 53 Hz, duration of the impulse of about 20ns and energy 10nJ. The beam was detected by the fast and sensitive HEB. The spectra were compared to results obtained from a standard time domain spectroscopy (TDS) setup. Only small discrepancies between spectra measured by both methods are observed. For the range 0.7-2.0 THz typical features can be identified using both methods. Above 2 THz the TDS setup seems to have better performance in terms of signal-to-noise ratio and sensitivity. © (2013) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

Topics
Bolometers ; Electrons ; Optical parametric oscillators ; Signal to noise ratio ; Spectroscopy ; Terahertz radiation

Citation
Michał J. Walczakowski ; Norbert Palka ; Przemyslaw Zagrajek and Mieczyslaw Szustakowski" Terahertz spectra of materials measured by the OPO-based system ", Proc. SPIE 8716, Terahertz Physics, Devices, and Systems VII: Advanced Applications in Industry and Defense, 87160Y (May 31, 2013); doi:10.1117/12.2015375;http://dx.doi.org/10.1117/12.2015375

The TPS Spectra 3000 was used in this study

Influence of surface of explosive on its detection and identification using the SDA method for analysis of the reflected THz signal

Proc. SPIE 8734, Active and Passive Signatures IV, 87340Q (May 23, 2013); doi:10.1117/12.2015604;http://dx.doi.org/10.1117/12.2015604

Authors: Vyacheslav A. Trofimov; Svetlana A. Varentsova; Mieczyslaw Szustakowski; Norbert Palka


Vyacheslav A. Trofimov, Svetlana A. Varentsova
Lomonosov Moscow State Univ. (Russian Federation)

Mieczyslaw Szustakowski, Norbert Palka
Military Univ. of Technology (Poland)

Abstract

The SDA (Spectral Dynamics Analysis) method is used for the detection and identification of the PWM C4 explosive with the surface having inhomogeneity, caused by action of the sandpaper with different grit on the explosive surface, or with the surface having various curvature of its surface. We show that the SDA-method is good tool for the detection and identification of the explosive using THz signal reflected from the PWM C4 explosive. We propose (see as well [24]) integral criteria for the identification of substances. These criteria allow to detect the explosive despite an influence of its shape on the THz spectrum. Proposed assessments and algorithms for computation of the identification probability show both high probability of the substance identification and a reliability of realization in practice. © (2013) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

The TPS Spectra 3000 system (TeraView Ltd., Cambridge, UK) was used in this study. 

click here to find more information

The influence of smoke on the THz imaging

Photonics Letters of Poland, Vol. 4 (3), 94-96 (2012)
doi: 10.4302/plp.2012.3.04

Authors: Paweł S. Jung1,  Mirosław A. Karpierz1, Norbert Pałka2 and Elzbieta Rurka2

1. Faculty of Physics, Warsaw University of Technology, Koszykowa 75, 00-662 Warszawa, 
2. Institute of Optoelectronics, Military University of Technology, S. Kaliskiego 2 , 00-908 Warszawa

Abstract

The influence of smoke on THz imaging was examined. We tested experimentally a passive THz camera - TS4 from ThruVision Systems Ltd. The camera detects natural human radiation at a frequency of 0.25 THz. The distance camera-target could be 3-15 meters. Moreover, Time Domain Spectroscopy was used to investigate the  influence of the amount of smoke on transmission in the (0.1÷2.5) THz range.

Full text available at:
http://photonics.pl/PLP/index.php/letters/article/viewFile/4-34/233

...In order to check the influence of smoke on transmission in the THz range, we exploited Time  Domain Spectroscopy (TDS) [2, 4, 5] . The TDS gives us  opportunity to measure transmission in the (0.1 ÷2.5) THz  range. In the experiment setup we applied a spectrometer TPS Spectra 3000 from TeraView [7]...

More on terahertz technology for Homeland Security and Defense applications:
http://www.teraview.com/applications/homeland-security-defense-industry/index.html

Towards optoelectronic detection of explosives

Opto-Electronics Review, June 2013, Volume 21, Issue 2, pp 210-219

doi 10.2478/s11772-013-0082-x

Authors: J. Wojtas, T. Stacewicz, Z. Bielecki, B. Rutecka, R. Medrzycki, J. Mikolajczyk
More details at: http://link.springer.com/article/10.2478/s11772-013-0082-x

Abstract

Detection of explosives is an important challenge for contemporary science and technology of security systems. We present an application of NOx sensors equipped with concentrator in searching of explosives. The sensors using CRDS with blue — violet diode lasers (410 nm) as well as with QCL lasers (5.26 μm and 4.53 μm) are described. The detection method is based either on reaction of the sensors to the nitrogen oxides emitted by explosives or to NOx produced during thermal decomposition of explosive vapours. For TNT, PETN, RDX, and HMX the detection limit better than 1 ng has been achieved.

... Time domain spectroscopy (TDS) is especially useful in the THz range [12,13]. Observation of explosives' transmission and reflection are conducted by using TeraView TPS Spectra 3000 instrument at the Institute of Optoelectronics, MUT ...

Author Affiliations: Institute of Optoelectronics, Military University of Technology, 2 Kaliskiego Str., 00-908, Warsaw, Poland

In 2011 TeraView supplied two TPS Spectra 3000 systems with a stand-off explosives detection module and a fibre-fed scanning system with multiple gantry options for research into terahertz imaging and non-destructive testing. Military University of Technology (MUT) in Poland is one of the country’s most prestigious research institutes for terahertz research and materials characterisation. Read more...