Anomalous burning through of thin foils at high brightness laser radiationheating

The results of the experiments at the installation "PICO," with thin foils heating by laser radiation pulses of nanosecond duration are reported. The Al foils with thickness in the range from 3 mu up to 40 mu were used as tar gets. The flux density was varied from 10(13) W/cm(2) to 10(14) W/cm(2). Th e sharp dependence of the portion of laser energy that passed through the t arget on foil thickness was observed. This phenomena was accompanied by a r elatively small decrease of the passed radiation pulse duration. The anomal ously high speed burning through of thin foil was observed in these experim ents and the conclusion on,the possible mechanism of this phenomena has bee n done on the base of comparison of experimental data with theoretical calc ulations. The observed phenomena can be interpreted with:a conjecture about the local burning through of a target, in the small areas of the target su rface, with many more values of flux density than the average one following laser radiation self-focusing and formation of "hot spots."