Home – Home – Jornals – Thermophysics and Aeromechanics 2022 number 3

In laser ablation, the nonuniform distribution of energy across the laser beam leads to a nonuniform heating and evaporation of the material from the irradiated surface. The influence of nonuniform temperature and that of the nonuniform flux of evaporated material from the surface on the laser-plume expansion dynamics during the nanosecond laser ablation in vacuum were studied. It was assumed that the surface temperature depended linearly on the laser radiation energy. Direct Monte Carlo simulation of pulsed gas expansion for a flat-top laser beam and for a Gaussian beam has been carried out under the assumption of no absorption of laser radiation in the plume. For the flat-top beam, the surface temperature proved to be areally uniform over the entire irradiation spot, whereas for the Gaussian beam, the temperature varied along the spot radius. It is shown that for both beams, the final distributions of particles in the plume are almost identical. However, in the case of the Gaussian beam the plume moves a little faster in comparison with the flat-top beam, which circumstance leads to an increased kinetic energy of particles passing through the time-of-flight detector by 2-4 %.