Portable detection system for standoff sensing of explosives and hazardous materials

Standoff Quartz Enhanced Laser Photoacoustic Spectroscopy (QE-LPAS) technique is emerging as a powerful technique for detection of hazardous chemicals, biological and explosive agents. Experimentally, we have recorded standoff photoacoustic spectrum of hazardous molecules adsorbed at diffused surfaces from a distance of up to 25 m. Tunable mid infrared quantum cascade lasers (MIR-QCL) in the wavelength range 7.0-12.0 μm are being used as optical source. Samples of Dinitrotoluene (DNT), Pentaerythritoltetranitrate (PETN) having adsorbed concentration of approximately 5.0 μg/cm2 were detected. Acetone and nitrobenzene samples in liquid having concentration 200 nl approximately sealed in polythene sachet were detected from a standoff distance of up to 25 m. All the above measurements are reported for a Signal to Noise Ratio (SNR) of 10, optimized for maintaining very less false alarm rates for field measurements. A portable trolley mounted system has been developed for field applications.