Plasma formation due to interaction of a $CO_2$ laser pulse with an aluminum target

A theoretical model is developed for the formation of a plasma due to the interaction of $CO_2$ laser pulses with an aluminum target in air. This model allows for the heating and evaporation of the target and for the absorption of the laser radiation in the moving vapor whose state is described in the two-temperature approximation. Use is made of the experimental shapes of the laser radiation pulses of 1–400 MW/cm${}^2$ intensity and 0.01–10 $\mu s$ duration. The calculated plasma-formation times are in agreement with the experimental data, especially when allowance is made for the possibility of existence of thermally insulated microregions on the irradiated target surface.