Mechanical Action Analysis And Numerical Simulation Of Laser Plasma To Solid Target

Combining key problems of laser propulsion technique, the physical models have beendeveloped and the numerical simulations have been finished for the formation andexpansion of pulse laser-induced plasma or vapor under different condition. The impulseand its coupling efficiency of laser action on the solid target have been obtained further.And all the results agree with correlative experiments.According to the characteristic of the action process for laser to solid target, a newmethod has been adopted for measuring the impulse of laser and target by using thetraditional pendulum device: Considering the influence of the air drag, the movingequation of the pendulum has been deduced for this device. Measuring the pendulumperiod and the speed of pendulum passing its equilibrium position on the second time andusing the moving equation, the impulse delivering from laser to target can be obtained.The experimental difficulty has been avoided that the initial speed of the pendulum cannot be measured accurately since the instantaneous action of laser to the target.Furthermore, according to the interaction mechanism of laser and materials, a physicalmodel about the process of optical breakdown and plasma formation induced by laser hasbeen developed. The evolution of plasma has been simulated numerically by using a highorder accurate finite difference computational method. The evolution process of air plasmahas been obtained. Comparing numerical results with experimental ones reporting by otherresearchers, it has been made sure that the validity of this numerical method. Basing onthe result, adopting an advanced method of "ghost fluid" to deal with reflecting boundaryof curved surface, the expanding and reflecting process of air plasma induced by laserproducing on the focus of a parabolic surface has been simulated numerically, the actionrule of the impulsive force for the plasma to the parabolic surface has been obtained.Analyzing the formation process of target vapor and plasma induced by laser ablativetarget material in vacuum, the expanding process of target vapor and plasma has beensimulated numerically. The changing rule of impulse coupling from laser ablative targetmaterial in quasi-vacuum has been found. Analyzing the formation process of plasmainduced by laser in air ambient, the expanding process of plasma has been simulatednumerically and the impulsive force acting on the solid target has been obtained. The impulse delivering efficiency of laser to the solid target in vacuum and in air ambient havebeen analyzed and compared. Which provide a research way to improve the impulsecoupling efficiency.The research methods and results reported presently not only reveal the interactionmechanism and detail between laser and solid target, but also supply a useful routine foroptimization of laser propulsion capability and quantitative calculation of impulsioncoupling of laser-solid target in corresponding conditions.