An investigation of the shock front generated by detonation of single particle explosives using a novel system for high-speed time-resolved holography.

摘要

A configuration for sequential holographic recording based on a new system for obtaining a train of spatially separated light pulses was developed. The multipulse system uses a single high energy Q-switched Nd:YAG laser pulse as a light source, and incorporates a phase-front preserving optical delay line and a specially graded beamsplitter to divide the initial pulse into ten spatially separated light pulses of nearly equal energy. The temporal spacing between successive output pulses may be varied discretely from 28.3 ns to 169.8 ns in steps of 28.3 ns.; The time-resolved holographic system was developed to study detonation dynamics in dispersed solid particulate explosives. The research effort described in this dissertation was the first phase of this study--the investigation of shock wave generation and propagation arising from detonation of single 100 {dollar}mu{dollar}m diameter explosive lead azide (PbN{dollar}sb6){dollar} particles. This required a holographic system capable of recording a rapid sequence of exposures during the approximate 1 {dollar}mu{dollar}s lifetime of the detonation event. Using the time-resolved holographic system, it was possible to image the detonation process, specifically the generation and decay of a reaction volume, and the formation and propagation of a shock front. Measurements taken from the holographic images were used to obtain relationships for shock front extent, shock front velocity, and shock overpressure as a function of time after detonation. For example, it was found that initial shock velocities approaching Mach 9 decayed to near acoustic velocities (Mach 1.5) within 2 {dollar}mu{dollar}s. In addition, the feasibility of using the time-resolved holographic system to investigate multiple particle interactions has been demonstrated.