STANDOFF RAMAN SPECTROSCOPY SYSTEM FOR DETECTION OF EXPLOSIVES, CHEMICAL WARFARE AGENTS SIMULANTS AND TOXIC INDUSTRIAL COMPOUNDS By

In this work a remote Raman system has been designed, assembled and tested for detecting explosives, Toxic Industrial Compounds (TIC) and Chemical Warfare Agents Simulants (CWAS) at laboratory scale up to 7 m target-telescope distance. The prototype system consists of a Renishaw Raman Microspectrometer, model RM2000, equipped with a charge-coupled device (CCD) detector, a telescope, a fiber optic assembly and a single wavelength/frequency laser source (514/488 nm and 532 nm). The telescope was coupled to the Raman microscope using an optical fiber and filters for rejection of laser radiation and Rayleigh scattering. Two convex lenses collimate the light from the telescope output, which is directed into the fiber optic from which the focusing objective was removed. The output of the fiber was directly coupled to the Raman system by a 5x objective. To test the standoff sensing system, the VIS Raman Telescope was used in detection of secondary explosives: 2,4,6-trinitrotoluene (TNT), 2,4-dinitrotoluene (2,4DNT), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), triacetone triperoxide (TATP) and plastic explosive C4, with detection limits below 10 mg. The TICs used were benzene, toluene, xylenes, chloroform, CCl4 and CS2. Other compounds studied were Chemical Warfare Agents Simulants dimethylmethyl phosphonate (DMMP), 2-chloroethyl ethyl sulfide (2-CEES). Solid samples (explosives) were deposited on stainless steel plates and liquid samples were transferred into 5 mL glass vials. Both types of samples were placed at a distance of 7 m from the telescope. Raman spectra of compounds were acquired in the Raman shift range of 100-3200 cm using laser powers varying from 50 mW to 1 W and integration times of 1 to 30 s.