Stimulated Brillouin scattering behaviors in multi-ion species plasmas in high-temperature and high-density region

Abstract

Different IAW modes excited by stimulated Brillouin scattering (SBS) and different SBS behaviors in several plasmas composed of ion species relevant to inertial confinement fusion in the high-temperature and high-density region have been studied by Vlasov-Maxwell simulations. Firstly, the linear theory is taken to analyze the linear process of IAW and SBS in multi-ion species plasmas. Secondly, the nonlinear effects on SBS in CH and AuB plasmas have been studied in detail. Especially, particle trapping will lead to nonlinear Landau damping and nonlinear frequency shift (NFS) of IAW. Particle trapping will decrease IAW Landau damping and make SBS in CH plasmas transform from convective instability in the linear regime into absolute instability. The NFS from particle trapping and harmonic generation in AuB plasmas will lead to a positive shift of the IAW frequency and make the frequency of SBS scattering light experience an obvious negative shift. And, the nonlinear model can give a good explanation of the nonlinear phenomena. Lastly, the saturation mechanisms are analyzed. The main nonlinear saturation mechanisms of SBS include NFS from particle trapping and harmonic generation, energy dissipation by spectrum broadening, and pump depletion. Microscale kinetic simulations of SBS are interesting, difficult, and could have an impact on the current understanding of the instability, particularly in the nonlinear regime where wave-particle interactions contribute to the saturation of reflectivity.