ON THE EFFECTIVE CONDITIONS OF EROSION SURFACE PLASMA FORMATION IN AIR UPON EXPOSURE TO THE REPETITIVELY PULSED LASER-RADIATION

An exposure has been investigated of a number of materials (aluminum, copper, graphite, ebonite) to a series of periodic laser pulses (lambda = 1.06-mu-m) in air at the laser radiation power densities q = 10(7) - 10(9) W/cm2 and laser pulse repetition frequencies f less-than-or-equal-to 50 kHz in exposure spots approximately 10(-2) cm2 in area. Conditions have been revealed for the effective erosion plasma formation (q > 2.10(8) W/cm2, f greater-than-or-equal-to 5 kHz) which provide for expulsion of a screening air plasma layer produced by the first laser pulse of the series and transition to the erosion plasma formation with a low degree of target screening in the course of exposure to subsequent laser pulses.