Influence of the density of petn-coal composites on the threshold characteristics of explosive decomposition in laser initiation

This paper presents the results of measuring the thresholds of explosive decomposition of PETN-coal under the action of laser radiation pulses ($\lambda$= 1 064 nm and $\tau$= 14 ns). Samples whose thickness is 1 mm and whose densities are 1.1 and 1.7 g/cm$^3$ with inclusions of submicron particles of brown coal (750 nm) are investigated. Matrices in composites with densities of 1.1 and 1.7 g/cm$^3$ are almost transparent for radiation. A minimum explosive threshold of 1.8 J/cm$^2$ is reached with a concentration of inclusions of 0.5% (by weight). The explosion is adiabatic. Composites with a density of 1.1 g/cm$^3$ have a scattering matrix. A minimum explosive threshold of 2.3 J/cm$^2$ is obtained for a concentration of inclusions of 1%. An extinction rate is estimated: $k_{ext}$ = 135 cm$^{-1}$. Radiation is absorbed at a depth of $<$ 0.1 mm. Explosive decomposition in an unirradiated section develops according to the shock-wave mechanism of explosive combustion.