Proton Radiography of Explosively Dispersed Metal Particles while Under Vacuum

A series of experiments performed at Los Alamos National Laboratory is aimed to provide validation data for numerical simulations performed at the PSAAPII Center of Compressible Multiphase Turbulence (CCMT). Five explosive tests were performed. Approximately 2.8 g of PBX-9501 was initiated by a RP-80 detonator. A 13 x 13 mm cylindrical packet of 100 µm steel particles was dispersed by the explosive. A time-series of 21 proton radiography images were collected at 2 µs temporal resolution, allowing penetration of the explosive products at early time and extraction of the particle fronts.

One of the challenges in simulation of the explosive dispersal of particles is the compaction model at early times and the subsequent particle collisions. To ease the modeling burden, two experimental design decisions were made to simplify the physics present. First, the experiments were done under vacuum. The removal of the ambient gas medium prevents the formation of an air-shock to propagate over the bed, subjecting the particles only to the contact discontinuity formed by the explosive product front moving into vacuum. Second, the volume fraction of the particle bed was reduced by substituting hollow glass microspheres for a portion of the steel particles.