THRESHOLD OF SURFACE PLASMA FORMATION BY THE INTERACTION OF LASER-PULSES WITH A METAL

An analysis is made of a model of the formation of a surface laser pla sma which takes account of the heating and vaporisation of thermally i nsulated surface microdefects. This model is used in an interpretation of experiments in which such a plasma has been formed by irradiation of a titanium target with microsecond CO2 laser pulses. A comparison w ith the experimental breakdown intensities is used to calculate the av erage size of microdefects and their concentration: the results are in agreement with the published data. The dependence of the delay time o f plasma formation on the total energy in a laser pulse is calculated.