Measurement of gasdynamic pressure on a target subjected to CO2 laser radiation

Measurements were made of the pressure on the surface of a target subjected to high-power CO₂ laser radiation under conditions ensuring one-dimensional motion of the resultant plasma. These measurements were carried out on lead, aluminum, and titanium targets using laser radiation of 10⁷–10⁹ W/cm² power density. The pressure in the air surrounding the target was varied from 0.07 to 760 Torr. It was found that the pressure on the target surface in vacuum was due to the evaporation of the target material but in air this pressure was governed by the gasdynamics of a laser-absorption wave traveling from the target to meet the incident radiation. The transition from one interaction regime to the other occurred when the air pressure was ~80 Torr.