In operando measurements of high explosives.

Abstract

In operando studies of high explosives involve dynamic extreme conditions produced as a shock wave travels through the explosive to produce a detonation. Here, we describe a method to safely produce detonations and dynamic extreme conditions in high explosives and in inert solids and liquids on a tabletop in a high-throughput format. This method uses a shock compression microscope, a microscope with a pulsed laser that can launch a hypervelocity flyer plate along with a velocimeter, an optical pyrometer, and a nanosecond camera that together can measure pressures, densities, and temperatures with high time and space resolution (2ns and 2 µm). We discuss how a detonation builds up in liquid nitromethane and show that we can produce and study detonations in sample volumes close to the theoretical minimum. We then discuss how a detonation builds up from a shock in a plastic-bonded explosive (PBX) based on HMX (1,3,5,7-Tetranitro-1,3,5,7-tetrazocane), where the initial steps are hotspot formation and deflagration growth in the shocked microstructure. A method is demonstrated where we can measure thermal emission from high-temperature reactions in every HMX crystal in the PBX, with the intent of determining which configurations produce the critical hot spots that grow and ignite the entire PBX.