Laser Driven Flyers for Investigations of Shock Initiation of Explosives

A full description and characterization of a tabletop laser-launched flyer plate system with associated high-speed diagnostics is presented. With this tabletop system, we can investigate shock initiation and detonation of energetic materials with hundreds of shots per day. The present study focuses on application of the 32-channel pyrometer developed in our group for optical temperature measurements of hot spots in shock-initiated energetic materials. Extremely high temperature (>6000 K) hot spots have been observed in fine powders of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), and the shock duration dependence on chemical kinetics has been studied. Polymer bound (PBX) charges with controllable microstructure were used to identify the origins of high temperature hot spots. Hot spot temperatures were reduced to 4000 K when an elastomeric binder was used to fill void spaces between powder grains. We attribute these high temperatures to adiabatic compression of gases in microvoids (>6000K) and in nanovoids (4000K), based on measurements where the gas composition and void sizes were varied.