A Possible Way for the Detection and Identification of Dangerous Substances in Ternary Mixtures Using THz Pulsed Spectroscopy

Abstract

We discuss an effective tool for the detection and identification of substances in ternary mixtures with similar spectral properties using a broadband reflected THz signal. Nowadays, this is an urgent problem; its effective solution is still far off. Two ternary mixtures of the explosives (RDX+TNT+HMX and RDX+TNT+PETN) were used as the examples for demonstration of the efficiency of the method proposed. The identification is based on the pulsed THz spectroscopy. We follow the spectral intensities together with the use of integral correlation criteria. They use the spectral line dynamics of the THz pulse reflected from the substance under investigation and that of the standard THz signal from database. In order to increase the accuracy and reliability of the identification, we analyze the partial non-overlapping time intervals, containing the main pulse of the reflected THz signal and the sequential sub-pulses. The main pulse is shown to contain information about high absorption frequencies (ν > 2.6 THz) of the mixture components. In the sub-pulses, the absorption frequencies of the components are detected in the range of low (ν < 2.6 THz) and high (ν > 2.6 THz) frequencies. The opportunity of distinguishing the mixtures with similar spectral properties is also shown.

Antenna-Coupled Titanium Microbolometers: Application for Precise Control of Radiation Patterns in Terahertz Time-Domain Systems

“…Terahertz time-domain spectroscopy (THz-TDS) is a distinctive example of a wideband electromagnetic radiation system invented more than three decades ago [ 1 ]. The THz spectroscopy is very powerful technique for the test and discrimination of different kind of materials [ 2 , 3 , 4 ]; it can successfully serve for a medical inspection [ 5 , 6 ], security aims [ 7 , 8 ], photovoltaics industry [ 9 , 10 ] as well as food control purposes [ 11 , 12 ].…”

Spurious Absorption Frequency Appearance Due to Frequency Conversion Processes in Pulsed THz TDS Problems

“…Our approach is based on an analysis of the time-dependent spectral intensities (SDA-method) on both the absorption frequencies and the emission ones. Earlier, the SDA-method was successfully applied for the detection and identification of neutral and dangerous substances under real conditions [47][48][49][50][51][52][53][54], including the cases of very noisy THz signal and a sample with inhomogeneous surface. Therefore, we also follow this approach below.…”

“…In the time interval t =[40,70], the correlation coefficients decrease: c 1.2,0.4 = 0.712 (a), c 1.4,0.4 = 0.648 (b). Note that, in the short time interval t ≈[50,65]…”

Surface Persistence of Trace Level Deposits of Highly Energetic Materials

“…The residence time of a highly energetic material (HEM) on a surface can be defined as the time that the material persists on the surface after its deposition. The concept is essential for the development of samples and standards for trace detection systems [1][2][3][4][5][6][7][8][9][10][11][12]. Aside from adhesion considerations, the residence time mainly depends on the vapor pressure of the compound and surface-HEM interactions.…”