Study of Thermal Decomposition Roots and Detection of Explosives from Defense Test Range Soil Samples Using a Tunable Mid IR Qcl Laser Based Photoacoustic Thermal Analyzer

Abstract

The paper reports the identification of  by-products gases released during the thermal decomposition process of pure explosives like RDX and TNT,  and  their trace level presence in soil samples collected from the defence range. We have experimentally validated the REAFFX model reported by Strachan et al. related to root of thermal decomposition mechanism of RDX1 and release of  by-product gases such as HCN, HNO2, and CH4.  The detected percentage of HCN and CH4  for TNT were 5.6 % and 22.5 % of NO2, whereas, RDX releases HNO2 and CH4  of the order of 17% and 8.5% of NO2. A  photoacoustic cell in direct and multi-pass geometry modes was used. Quantum Cascade Laser (QCL) tunable between 5.3 to 7.3 µm ranges at 50 ns pulse duration at 2MHz repetition rate was used as a pumping source. The detection limit of these gases lies between 65- 164 ppbv range.

Keywords: Photo acoustics, TNT, RDX, Quantum Cascade Laser