Hyperspectral Imaging for Temperature Measurements of Hot Spots in Shocked Plastic-Bonded Explosives

Hot spots are formed when energetic microstructures are shocked, and they play a critical role in shock sensitivity. It is important to know both the time-dependent size and temperature of the hot spots, in order to generate a kinetic model to describe reaction growth in plastic-bonded explosives (PBX). Here we use a recently developed technique where PBX is fabricated in the form of a thin wafer, embedded within a transparent polymer binder, and shocked with a laser-launched flyer plate that produces pressures of about 30 GPa range. In this method, every crystal of the cyclotetramethylene-tetranitramine (HMX)-based PBX can be observed during the shock. Hot spots can be seen via their thermal emission, which is detected with both a 32-channel optical pyrometer, which gives spatial-average temperatures and emissivities, and an eight-frame nanosecond camera that images hot spots directly with 2 um resolution. Using hyperspectral imaging, we acquire four pairs of time-resolved images using red and blue filters. With simultaneous two-color imaging we can watch temperature and emissivity change with time.