Features of braking absorption of laser radiation

Abstract

Theoretical and experimental work was carried out on establishing the parameters of the plasma with a nanosecond duration of the laser pulse and the condition of the existence of the developed gas-dynamic movement of the plasma. The authors obtained a solution to the problem of describing the absorption of laser radiation in a dense layer of hot plasma. The authors have established analytical dependencies that correspond quite well to real conditions and determine the geometric and analytical thickness of the plasma. These results cooperate with the rigorous solution of the gas-dynamic equations for the evaporation process in the "selfconsistent" regime. In real conditions, when the radiation is focused, the strong lateral expansion of the plasma leads to the quasi-spherical nature of the spread and the plasma density decreases much faster than in the onedimensional case. The authors compared the expressions for the internal energy and estimated the transition time of a planar flow into a two-dimensional one. This made it possible to discover that both in the case of a planar flow and in the case of a two-dimensional flow, the internal energy of the plasma grows according to similar laws.