Study Of Impulse Coupling With Materials By Pulsed XeCl Excimer Laser

Laser induced impulse coupling to materials is one of physical phenomena in laser-target interaction, and lay a foundation for study in many fields, such as laser propulsion, laser radiation effects, anti-radiation hardening and etc. The coefficient of laser induced impulse coupling is greatly influenced by input laser parameters, ambient conditions, plasma near target surface and target properties. It will be useful to study the effects on laser induced impulse coupling by above factors. In this work, The theorectical and experimental study on impulse coupling produced by UV laser interaction with typical material (LY12 Al) are mainly concerned.Related theorectical calculations and analyses using four models are first made for better understanding of experimental results. Before plasma ignition, the transparent vapor model is used to obtain primary thermodynamic parameters for LY12 Al under different process, including laser heating before vaporation, steady and unsteady vaporation. Then, the laser induced impulse coupling coefficients in vacuum are numerically calculated. In the early stage of plasma breakdown, the main absorption mechnisms of laser with short wavelength are analyzed with the help of plasma ignition model. The depedence of several parameters characterizing the status of subcritical regime with laser condition are obtained according to a good scaling models. The ambient pressure effects on impulse coupling to target are valued through the model proposed by G.ASimons for LSD wave calculation. A 10J, 40ns XeCl laser is used for laser ablation experiments. The variation of impulse coupling coeffecients with incident intensity to LY12 Al in vacuum is obtained, and its dependence on gas pressure for LY12 A1/K9, respectively. The better agreement has been achieved between experimental data and theorectical results. The properties of plasma are analyzed with the help of the evolution of scattered laser from target. Also, plasma spectrum and integrated photo of vapor/plasma plume are recorded.