The Research On Expansion Dynamics Process Of Nanosecond Laser Plasma Use Shadow Mapping

Recent years, with the wide applications of the shock wave produced by laser-induced plasma in the fields of thin-film deposition, laser shock strengthen, laser propulsion and so on, people have paid more and more attention to the dynamic characteristics of shock wave produced by laser-induced plasma, especially to laser-supported detonation wave (LSD). Therefore, the deep understanding for the characteristics of shock wave produced by laser-induced plasma, especially the characteristics of LSD is required.In this letter, the research on dynamic characteristics of the shock wave produced by laser-induced plasma is developed, based on the different shock characteristics of the shock wave produced by laser-induced plasma under different experiment conditions. The main works are as follows:(1) The effects of different laser energies on the air and aluminum targets using acoustic diagnose when the nanosecond laser pulse irradiates are studied. The relation between the intensity of acoustic signals of shock wave and laser fluence is obtained, and the range of the ignition threshold of the LSD wave for different targets is confirmed.(2) The effects of different laser energies on the shock wave produced by laser-induced plasma which is produced by the irradiation of nanosecond laser pulse on air and aluminum targets is carried on. Shadowgraph imaging technique is used in this study and the time delay is fixed. Also, the range of the ignition threshold of laser-supported detonation is illustrated using the method of making the target at the angle of30degrees to the normal direction.(3) Time-resolved shadowgraph imaging is used to study the propagation rule of shock wave produced by laser-induced plasma which is produced by the irradiation of nanosecond laser pulse on target under the same laser energy and different time delay and the curves for propagation distance and velocity under different time delay is given. The propagation rule of the shock wave produced by laser-induced plasma is compared between longitudinal and transverse direction. The propagation dynamic characteristic of shock wave produced by laser-induced plasma is explained.