Shock Compression Microscopy for Tabletop Detonations in PETN-based Explosives*

We have developed a microscope system for performing shock compression experiments with km s^-1 impactors and nanosecond-duration shock waves. In the present work, this system is used to study polymer-bound explosive charges (PBXs) 1 mm in diameter and tens to hundreds of microns thick. The microscope diagnostics include particle velocity (Photon Doppler velocimetry) measurements, fast imaging, and optical pyrometry. The PBX under study is a pentaerythritol tetranitrate (PETN)-based PBX (80% PETN, 20% elastomer binder) and has been characterized using x-ray tomography and scanning electron microscopy. At lower shock-pressures we observed sub-detonative behavior and hot spots have structures which evolved over 20 ns and cooled relatively slowly. At higher shock-pressures, the shock wave was supported by fast chemical reactions and the particle velocity remained constant. In this regime the shock wave is detonation-like and the hot spot cooling rate increased dramatically.