Impulse Generation on Aluminum Target Irradiated with Nd:YAG Laser Pulse in Ambient Gas

摘要

Mechanisms of the impulse on an aluminum foil generated through laser ablation with the Nd: YAG laser with a wavelength of 1064 nm are studied by fitting computed results to the time-resolved impulse data measured by using the Velocity Interferometer System for any reflector for different ambient pressures ranging from 10~(-2) to 10~5 Pa. The computational method used accounts for thermal conduction within the aluminum target, the vaporization process under equilibrium thermodynamics through the Clausius-Clapeyron equation, and the expansion of aluminum ablation jet described by compressible gas dynamics with the laser radiation energy transfer. A constant reflectivity value on the aluminum target surface is used to replicate the time-resolved impulse data. The present study shows that the breakdown of ambient gas and the gas dynamic confinement of an ablation jet are attributed to the impulse generation at higher pressure cases after the laser power peak of the Nd:YAG laser. At lower ambient pressures, the impulse is produced due to the momentum transfer of the aluminum vapor ejected by laser ablation during the laser power peak.