Effect of air pressure on the spatial and emission characteristics of an aluminum laser torch under subthreshold conditions of ablation

The spatial characteristic of an aluminum laser-induced plasma are studied at a laser radiation intensity of (3.8–4.8) $\times$ 10$^8$ W/cm$^2$ and an air residual pressure of 6.7–133.3 Pa. It is found that the duration of the aluminum plasma glow is 50 $\mu$s and decreases with decreasing laser power output. The glow intensity reaches a maximum at $t$ = 1.4 $\mu$s and rises with laser energy. Typical sizes of the emitting area on the laser torch are determined.