Kinetics of the formation of a surface laser plasma in the absence of surface damage

An analysis was made of the kinetics of the appearance of a plasma near the surface of a heated body. It was assumed that during the heating process the surface temperature did not exceed the boiling (sublimation) point at a given external pressure and there was no intense evaporation. A quasisteady-state breakdown model was developed for the case when the characteristic time for the change in the vapor concentration due to surface heating was long compared with the characteristic time for the establishment of the spatial distribution of the vapor. It was found that the breakdown of the vapor and of the ambient gas occurred at different laser radiation intensities while the dependences of the principal parameters of the surface laser plasma on the radiation intensity were of a hysteretic nature. An analysis was also made of the case when the vapor concentration due to the heating varied rapidly compared with the characteristic time for the vapor distribution to be established. It was found that in this case the breakdown of the vapor of the target material could be accompanied by the breakdown of the ambient gas. A comparison was made with experimental data.