Cellular structures found in the detonation front of liquid nitromethane with tabletop shock compression

After accumulating data on hundreds of nitromethane (NM) experiments, it was verified the tabletop shock compression microscope could produce detonations with properties that are consistent with bomb sized charges. This was not initially obvious, due to the multiple orders of magnitude difference in material amount (0.09 – 0.7 µL) and shorter input shock duration (4 ns). Due to the short shock duration, the time it takes the shock to transition into a detonation, the shock-to-detonation, was reduced by orders of magnitude, nearing an ultimate minimum. Using photon Doppler velocimetry (PDV), optical pyrometry and a nanosecond imaging this work shows that the NM reaction falls into three specific regimes dependent on input shock strength. Images of these regimes revealed patterns that form on a shock font when oblique reactions waves race forward and collide with the front, referred to as cellular structures. Although these structures have been speculated to exist in pure liquid NM, they have not been directly imaged until now because high spatial (2 µm) and temporal (5 ns) resolution was needed to capture these dynamic events. This work shows that spherical explosions behind the planar shock font in print unique cellular patterns on the front. These patterns can determine exactly when, where, and how many explosions occurred.