Detonation of low-density explosives

Electromagnetic measurements of the particle velocity are performed in a situation when the detonation wave reaches the interface between a high explosive (HE) powder and a window made of an inert material (Plexiglas). PETN, RDX, and HMX with densities close to the natural bulk density are studied. As it is necessary to measure not only the averaged velocity profile, but also possible fluctuations at scales of the order of the HE grain size, a method of measurements by small sensors with the working arm length approximately 1 mm is developed and tested. In most experiments, profiles with clear chemical spikes are obtained; in some of the measured results, however, the chemical spike cannot be identified on the background of sharp signal oscillations, which may be considered as manifestation of the nonclassical mechanism of wave propagation (explosive combustion in Apin's classification). As compared with the previous study, the present results suggest parallel operation of the shock and convective mechanisms with domination of each mechanism at certain segments of the wave front.