Investigation of the effect exerted by interpulse interval on the efficiency of metal perforation by double laser pulses

To establish the conditions for the optimum effect of an additional laser pulse on metal perforation, the process of aluminum plate perforation has been studied by the laser spark spectrometry method using a LSS-1 atomic-emission multichannel laser spectrometer. It has been found that a maximal average perforation rate is attained at the interpulse interval 1-2 μs. For a more detail study of the effect exerted by the interpulse interval on the perforation process, the spectra recorded for different pumping energies and interpulse intervals were examined. It has been found that at small intervals the atomic lines in these spectra were heavily distorted due to reabsorption when radiation passed through the optically dense layers of the surface laser plasma. The optical density of the plasma was estimated with the use of the ratios for a pair of the resonance atomic lines of aluminum at 396.152 and 394.400 nm. The obtained results for the relationship between the plasma optical density and interpulse intervals correlated well with the results for the average perforation rate. (authors)