Specific features of an interaction between laser radiation and matter at high pressures of an ambient medium

Study of the development of a plasma cloud in the vicinity of the target in nitrogen has been performed. The mechanism of discharge propagation is discussed. Variations of physical characteristics of targets exposed to radiation are considered. Experimental data concerning interaction of a neodymium laser radiation with materials (metals, dielectrics) under high pressure are given. It is demonstrated that the environmental pressure increase over the range 30-100 atm with the flux density 106-107 w/cm2 results in a nearly complete screening of the target by the plasma cloud. The primary mechanism of zone formation of the laser radiation absorption in a cold gas under high pressures near the target is thermal emission (when the evaporation is insignificant) and the breakdown in the vapours of the evaporated substance. The major mechanism of sustaining the plasma cloud at flux densities of 1-10 Mw/cm2 is slow burning. It is noted that the periodic variation of brightness of plasma after the radiation effect on dielectrics has terminated can be associated with the energy production in a chemical reaction, the development of which is determined by the time of reaching the temperature that depends on the particle size. The target characteristics in the interaction zone are considered, which depend on the radiation flux density and the gas pressure in the chamber