| Inertial confinement fusion (ICF) is one of the approaches to the controlled release of energy derived from the fusion of atomic nuclei. In this approach, intense laser light is focused onto a target filled with a nuclear fuel. Laser-plasma instabilities are important in the field of ICF because they scatter laser light away from the target, which reduces the laser energy available to drive the compression of the nuclear fuel, or generate energetic particles that preheat the fuel, which makes the fuel harder to compress. Stimulated Brillouin Scattering (SBS) is a laser-plasma instability in which a pump light wave decays into a Stokes light wave and an ion-acoustic (sound) wave. The mechanisms that provide coupling between the light and sound waves are the nonlinear current and the pondermotive (PM) force. Landau damping, pump depletion, and hydrodynamic and kinetic nonlinearities can limit SBS. Much is known about the linear growth and nonlinear saturation of SBS in one-ion plasmas. Despite the fact that most ICF experiments involve plasmas with two (or more) ion species, little is known about SBS in such plasmas. All the interesting properties of SBS in multiple-ion plasmas can be deduced from the study of SBS in two-ion plasmas. Fully-ionized hydrocarbon (CH) plasmas are very important in practice. The average-ion model used previously gives inaccurate values for the SBS reflectivity. In reality two types of sound wave (fast and slow) exist in two-ion plasmas, each of which can participate in SBS. In this thesis a fluid model with phenomenological Landau damping terms is used to compare the effects of Landau damping, pump depletion and hydrodynamic nonlinearities on SBS in multiple-species plasmas. |
