The Efficiency of Ablation of Metals by Scanning Beam of Pulsed Irradiation with Nanosecond-Range Fiber Yb:YAG Laser

— Results of experiments on ablation of targets made of stainless steel and aluminum with a scanning beam of nanosecond pulses at a power density of up to q = (0.38–1.0) × 10 9 W/cm 2 are presented. The overlap of the impact zones during irradiation was found to lead to an increase in the ablation depth in proportion to the area of irradiation spot overlap. This effect is due to fact that, as the degree of overlap of irradiation spots increases, zones with a larger number of pulsed-irradiation effects are formed on the target surface, which increases the melt bath depth and leads to the ejection of larger particles. The aluminum ablation depth increases with the increase in the interpulse interval up to Δ t = 10 ms; the larger the overlap of irradiation spots, the more significant the increase. The shape of the ejected particles changes from spherical, characteristic of the particles produced from a melt, to an irregular shape, which is characteristic of the particles produced as a result of mechanical destruction of the target by an internal shock wave. The size and velocity distributions of the ejected particles were determined, and the data obtained were used to calculate the shielding coefficients for laser radiation as a function of the degree of overlap of irradiation spots. It was found that the main mechanism that drives the decrease in the efficiency of the ablation with a scanning radiation beam is the reverse flux of microparticles that are deposited on the target surface. The energy balance of the ablation of aluminum has been analyzed.