The study of laser-induced flare discharge on dielectric and semiconductor macroparticles in vacuum: plasma production and ablative acceleration

An injector was used that allowed the multiple triggering of a beam of particles (of a size of several to 100 mu m) in a region where laser irradiation was focused. By varying the experimental conditions, the particles could be either completely or partially evaporated and strongly accelerated by ablation. The maximum measured velocities were 4*10/sup 6/ cm/s, plasma velocities were about (1-2)*10/sup 7/ cm/s, and the temperature was about 100-150 eV. Only 30% of the substance (particles of B/sub 4/C with dimensions greater than 40 mu m) was evaporated before destruction. The particles of B/sub 4/C that were smaller than 30 mu m were completely evaporated under a laser power density of about 10/sup 12/ W/cm/sup 2/ and a half-duration of 30 ns. For the particles smaller than 100 mu m and made of materials with a low evaporation temperature, such as paraffin, LiH, and polystyrene, no accelerated fragments were detected, i.e. these particles were completely evaporated during less than 10 ns.<
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