Date of Award

9-2021

Document Type

Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Department of Engineering Physics

First Advisor

Glen P. Perram, PhD

Abstract

This dissertation covers nanosecond pulsed laser ablation of graphite for 4-5.7 J/cm2 fluences with 248 nm and 532 nm lasers in 1-180 Torr helium, argon, nitrogen, air, and mixed gas. Three experiments were performed to improve the interpretation of common diagnostics used to characterize pulsed laser ablation, find simple but universal scaling relationships for comparing dynamics across different materials and ablation conditions, and provide a systematic analysis of graphite emissive plume and shock wave dynamics. A scaling of the Sedov-Taylor energy ratio was developed and validated for a range of studies despite differences in wavelength, pulse duration, fluence, and target material. Normalized shock thickness for Mach 48 plumes were compared to prior ablation and shock tube studies (Mach ≤ 10) using a common analytical model. Shock detachment distances were identified by comparing plume and schlieren shock propagation trajectories. The shock detachment points were used to improve Sedov-Taylor blast analysis, allowing for enhanced estimates of laser-plume energy coupling. Finally, plume and shock wave morphology were compared.

AFIT Designator

AFIT-ENP-DS-21-S-023

DTIC Accession Number

AD1151422

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