兰登效应对SRS从早期暴胀到后期二次不稳定性发展的非线性演化的影响
Investigation of Langdon effect on the nonlinear evolution of SRS from the early-stage inflation to the late-stage development of secondary instabilities
摘要：
在激光辐照等离子体中，兰登效应会产生超高斯电子能量分布函数（EEDF），对受激后向拉曼散射（SRS）产生重要影响。本文采用三波模型模拟和Vlasov-Maxwell模拟方法，研究了在高、低强度激光驱动下，超高斯EEDF对等离子体受激喇曼散射（SRS）非线性演化的影响。在SRS演化的早期阶段，研究发现除了电子俘获产生的动力学效应[Phys. Plasmas 25，100702（2018）]，兰登效应还可以显著拓宽SRS绝对增长的参数范围，在一定的参数范围内，兰登效应大大缩短了绝对SRS达到饱和的时间。在受激喇曼散射的后期，当电子等离子体波衰减为束声模、再散射和朗缪尔衰减不稳定性等二次不稳定性变得重要时，兰登效应可以通过影响二次过程来影响受激喇曼散射的反射率。了解朗顿效应对受激喇曼散射的非线性演化和饱和的影响，将有助于更好地理解和预测惯性约束聚变中的受激喇曼散射。
英文摘要：
In a laser-irradiated plasma, the Langdon effect can result in a super-Gaussian electron energy distribution function (EEDF), imposing significant influences on the stimulated backward Raman scattering (SRS). In this work, the influence of a super-Gaussian EEDF on the nonlinear evolution of SRS is investigated by three wave model simulation and Vlasov-Maxwell simulation for plasma parameters covering a wide range of kλDe from 0.19 to 0.48 at both high and low intensity laser drives. In the early-stage of SRS evolution, it is found that besides the kinetic effects due to electron trapping [Phys. Plasmas 25, 100702 (2018)], the Langdon effect can also significantly widen the parameter range for the absolute growth of SRS, and the time for the absolute SRS to reach saturation is greatly shorten by Langdon effect within certain parameter region. In the late-stage of SRS, when secondary instabilities such as decay of the electron plasma wave to beam acoustic modes, rescattering, and Langmuir decay instability become important, the Langdon effect can influence the reflectivity of SRS by affecting the secondary processes. The comprehension of Langdon effect on nonlinear evolution and saturation of SRS would contribute to a better understanding and prediction of SRS in inertial confinement fusion.
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