| A high-power carbon dioxide laser was used to ablate bulk liquid, polymer, and thin film targets. Time-resolved force sensing measurements, ballistic pendulum impulse measurements, and quantitative shadowgraph and Schlieren imaging techniques were used to study ablation. Propulsion parameters (including imparted impulse, momentum coupling coefficient, ablated mass, specific impulse, and internal efficiency) were measured for the materials when possible. In addition, a detailed examination was conducted as to the dependence of these parameters on the absorption depth of the materials, and on the thence at the target. An initial study was made on the scaling of the propulsion parameters with the ablated spot area. The effects of varying the thin film thickness on the impulse were also noted. A calibration technique for piezoelectric force sensors was developed using impacts of spheres on the sensors. Finally, a basic physical analysis of the propulsive quantities was made that raises questions about the standard interpretation of the dependence of the coupling coefficient on the fluence. |
