间接驱动相关条件下的大空间尺度对流受激拉曼侧向散射

Large-spatial-scale convective stimulated Raman side scattering under indirect drive conditions

利用基于光线追踪和对流放大模型的模拟程序PHANTAM,对神光Ⅲ原型装置间接驱动相关条件下的大空间尺度受激拉曼散射进行了研究.模拟结果表明,在该参数条件下,真空腔和充气腔中均会发生较强的对流受激拉曼侧向散射过程.入射光的焦斑大小是影响对流受激拉曼侧向散射的关键因素:在光强保持不变的条件下,真空腔和充气腔中受激拉曼侧向散射的对流增益会随焦斑增大而增大,而在功率保持不变的条件下,会随焦斑增大而减小.因此改变焦斑尺寸是调控受激拉曼侧向散射对流增益的有效途径.

The large-spatial-scale stimulated Raman scattering relevant to the SG-III prototype indirect drive parameters is investigated by using the code PHANTAM,which is based on ray tracing and convective amplification.The simulations show that strong stimulated Raman side scattering processes occur in both empty hohlraum and gasfilled hohlraum.The incident laser spot size is found to be the critical factor affecting stimulated Raman side scattering:under the constant laser intensity conditions,the convective gain of stimulated Raman side scattering increases with the laser spot size increasing in both types of hohlraums.In our simulations,the wavenumber mismatch leads to a saturation of the convection gain of the stimulated Raman side scattering in empty hohlraum,while in gas-filled hohlraum the convection gain of the stimulated Raman side scattering keeps increasing as the spot size increases.Under constant laser power conditions,the convective gain of stimulated Raman side scattering decreases while laser spot size increases,and the convective gain of stimulated Raman side scattering decreases faster in empty hohlraum in our simulations.The convective gain of Raman side scattering can be adjusted by laser spot size.