Separation Of Ionic Components In Laser Pulse Irradiated Solid CH Materials

Plasma usually contains multiple ion components.The diffusion of ions of different compositions driven by plasma pressure gradients can cause spatial and temporal changes in the relative abundance of ions,i.e.,the phenomenon known as ion component separation.Since a number of physical properties of the plasma depend on the ion components such as the electron thermal conductivity,plasma radiation opacity,ion equation of state,etc.,ion component separation can have many physical consequences.Recently,in inertial confinement fusion(ICF),it has been found that the implosion performance of the targe is lower than expected from radiation hydrodynamic simulations,presumably related to ion component separation,and thus the study of ion component separation effects has been a hot topic in recent years.In ICF,radiation hydrodynamic simulations are indispensable for designing experiments and explaining experimental phenomena,yet radiation hydrodynamic simulation programs often simplify the treatment of multiple ions into one ion,physically neglecting the effects of ion component separation on fluid evolution.In order to improve the physical module of radiation hydrodynamic simulation and to study the effect of ion component separation on fluid evolution,it is necessary to establish diffusion equations that accurately describe ion component separation.To this end,in this thesis,the Chapman-Enskog method is used to approximate the kinetic equations from the Landau-Fokker-Planck equation for a two-ion-component plasma to obtain the transport equations for electrons and ions in the hydrodynamic limit.The ion pressure diffusion coefficient,electron thermal diffusion coefficient,ion thermal diffusion coefficient and electric diffusion coefficient are obtained by applying Sonine polynomial expansion to the first-order velocity distribution functions of electrons and ions,and the evolution equations of ion mass abundance and mass diffusion flow as well as the complete set of hydrodynamic equations including diffusion effects are given.In addition,in this thesis,the ion diffusion equation is solved by the macroscopic state of the CH ablation layer given by the one-dimensional radiation hydrodynamics program MULTI-1D,and then the effect of the component separation phenomenon on the laser ablation of solid CH materials is investigated.The calculations in this paper show that the ion component separation effect is a first-order linear correction to the zero-order distribution function of the particles,and its effect on the fluid evolution of the CH plasma is small and can be largely ignored;however,for other physical processes that are sensitive to ion component dependence,such as Thomson scattering,the effect of ion component separation is significant,suggesting that the effect of ion component separation needs to be considered when studying laser-plasma interactions.