Determination of critical energy criteria for hexanitrostilbene using laser-driven flyer plates

Abstract

Laser-driven flyer plates comprise of one or more thin layers forming a foil coated onto a transparent substrate. Irradiation of the foil/substrate interface with a Q-switched laser pulse produces a plasma, the expansion of which forms a flyer plate, which can reach velocities in excess of 5 km/s. These plates impart shocks in excess of 50 GPa, with duration of less than a nanosecond. This shock is sufficient to initiate secondary explosives such as Hexanitrostilbene (HNS) and Pentaerythritol Tetranitrate (PETN). Thresholds of detonators based on laser-driven flyer plates are typically measured in terms of energy. By using a Photonic Doppler Velocimeter (PDV) we measure the velocity of the flyer plate at the threshold energy. This allows calculation of the shock pressure and duration imparted to the explosive. By initiating HNS with a variety of flyer thicknesses, from 3 to 5 mm, we are able to evaluate Pnt in this extreme shock regime. The calculated value of n is compared to published values and discussed for similar systems. We are also able to use the James Criterion to analyze the initiation, with values of Ec and Sc being determined from experimental data, providing a predictive capability to model other configurations such as different flyer thicknesses and materials.