PDV measurements of the chemical reaction zone of pressed TNT

In order to have a better insight into the chemical reaction zone of pressed 2,4,6-trinitrotoluene (TNT), laser interferometry has been used to record nanosecond time resolved particle velocity profiles of the free surface of detonating trinitrotoluene (TNT) charges and of the interfaces between TNT detonation products and both lithium fluoride (LiF) and PMMA windows. The experiments consisted in initiating a detonation wave in a cylinder (75 mm length, 15 mm diameter) of pressed TNT (ρ₀=1.55 g/cm³) using an explosive wire detonator associated with an explosive booster, and in measuring either the explosive free surface velocity or the explosive/window interface velocity by means of a 1550 nm frequency shifted photonic Doppler velocimetry (PDV) system. The direct comparison of free surface and interface velocity wave profiles allows us to precisely determine the von Neumann spike parameters, and also to derive values for the Chapman-Jouguet pressure and for the reaction time. Our experimental records for pressed TNT were found to be consistent with earlier reports.