Plane shock initiation of detonation in γ-irradiated pentaerythritol tetranitrate

Abstract

The effect of γ irradiation on shock initiation sensitivity of pentaerythritol tetranitrate (PETN) single-crystal explosive was studied experimentally. Shock input strength was 8.6 GPa and detonation transition occurred after 7.3 mm of shock run for as-grown {110} crystals. Other crystals were given γ-ray doses of up to 1 Mrad from a 60Co source. Crystals were sensitized by doses greater that 0.6 Mrad, with 1 Mrad shortening the distance to detonation transition by almost 40%. The initiation process is apparently still of the homogeneous type. Irradiated crystals were studied by optical microscopy. Evidence of the presence of gas molecules produced by decomposition of PETN molecules induced by γ rays was observed. Platelets 20-50 μm in diameter and about 0.25 μm thick were noted inside the crystal 30 days after irradiation. Growth of penny-shaped crack-flaws was observed and attributed to buildup of internal strains generated by the decomposition gas pressure. It is hypothesized that the source of the increased shock sensitivity after irradiation is due to the additional decomposition sites generated by decomposition of PETN molecules by γ-ray excitation. These sites act as additional nuclei for thermal decomposition in the shocked material.