Appearance of a layer absorbing laser radiation near the surface of a metal target

The results are given of calculations of the formation of an absorbing vapor layer during irradiation of an aluminum target in air with neodymium laser pulses of ~1 msec duration and maximum power of the order of 10 MW/cm². It is assumed that the illuminated spot is of ~1 cm radius. The role of various physical and gas-dynamic processes in the general interaction between the radiation and target is discussed. The main process which governs the most characteristic observable features is the screening of the laser radiation by an absorbing plasma layer. The calculated results are in satisfactory agreement with the experimental data.