Improvements to Emissive Plume and Shock Wave Diagnostics and Interpretation During Pulsed Laser Ablation of Graphite
Abstract
This dissertation covers nanosecond pulsed laser ablation of graphite for 4-5.7 J/sq cm 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, xC;nd 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 difference 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 less than or equal 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.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 16, 2021
- Accession Number
- AD1151422
Entities
People
- Timothy I. Calver
Organizations
- Air Force Institute of Technology