THz Reflection Spectroscopy of Explosives Measured by Time Domain Spectroscopy

Terahertz range of electromagnetic spectrum (0.1 ÷ 10) THz has focused attention of scientists for years because of many interesting features including existence of spectral fingerprints of many materials (also explosives), through clothing imaging and safety for human being. Such advantages are of great importance for biochemical, defense and security related applications. Scanning of pure explosives in transmission mode is limited to samples with thickness less than about 1 mm, which is connected with relatively high attenuation especially in absorption peaks regions. In case of thicker samples one should consider a reflection way of measurement. We examined 100% pure samples made of explosives: hexogen (RDX), penthryte (PETN), octogen (HMX), their mixtures (RDX+PETN, RDX+HMX) as well as sugar and simulants of explosives — L-tartaric acid and 4-aminobenzoic acid (PABA). Spectra were acquired using commercial time domain spectroscopy (TDS) setup from TeraView (TPS Spectra 3000) with appropriate accessories in atmosphere with humidity less than 1%. We carried out our experiments using 3 configurations: transmission, specular reflection with incident angle 45◦ and stand-off reflection with 30 and 40 cm distance to a sample.