Standoff Quantum Cascade Laser Photoacoustic Spectroscopy based Explosive Detection System

Abstract

This paper focuses on the design and development of measurement technique and processing of signal for the detection of various explosive simulants like RDX(cyclo-trimethylene-tri-nitramine), TNT(Trinitro toluene), Sarin, TATP(Tri acetone triperoxide), their simulants like nitrobenzene, DNT(Dinitro toluene), DMMP(DiMethyl Methyl Phosphonate), acetone, propanol, etc. (in different states of matter) adsorbed on a metallic surface from a standoff distance ranging from few meters up to a distance of 25 meters in the wavelength range of 7-9 µm. The focus also lies on the measurement methodologies and the instrumentation employed in these systems. A dedicated single screen, single user, user friendly Graphical User Interface(GUI) for controlling the entire system, acquisition and processing of the incoming signal and demonstration of results has been developed with the help of Laboratory Virtual Instrument Engineering Workbench (LABVIEW). The dual phase sensitive detection technique has been employed. The “Data Acquisition for Explosive Detection System” (DAEDS) also carries out precise operation sequencing, parameter control, parameter measurement and storage of data. The incoming signal profile has been normalized with respect to the reference laser profile to obtain the resultant graph. Various experiments have been conducted and the resultant graphs have been plotted with intensity on the y-axis and wave-number on the x-axis as shown in the results section of this paper. Furthermore, online determination of the explosive or the simulant has been carried out. An engineering proto-type system has been developed which indicates the detected explosive/ simulant using the developed software. Keywords: