激光等离子体次级不稳定性及其耦合过程研究

激光等离子体不稳定性（LPI）是激光聚变中重要的物理过程。除了受激拉曼散射、受激布里渊散射、双等离子体衰变等初级LPI外，在高强度激光条件下，初级LPI中的朗缪尔波或散射光波还可以作为泵浦源激发朗缪尔波衰变不稳定性、散射光重散等次级LPI过程。次级LPI既可以作为饱和机制限制一些初级LPI的发展，又可以作为种子源激发或加强一些初级LPI的增长，是LPI研究的重要组成部分。本项目拟针对次级LPI发展，及次级LPI与初级LPI的耦合演化，开展理论与数值模拟研究，理解多种LPI之间的相互激发与竞争机制，理清能量在驱动激光、散射光、朗缪尔波、离子声波之间的传递规律与分配关系，探索次级LPI引发的等离子体状态变化和非线性动理学效应，以及这些效应在非线性演化阶段对LPI耦合过程的影响，建立耦合过程中电子多级加速的物理图象，认识高能热电子的产生机制和能谱结构，为激光聚变的物理设计和实验研究提供理论依据。

Laser plasma instabilities (LPI) are important process in laser fusion. Besides the famous primary instabilities such as stimulated Raman scatter (SRS), stimulated Brillouin scatter (SBS), and two-plasmon decay (TPD), some secondary instabilities, such as Langmuir decay instability (LDI) and re-scatter of scattered light, can be stimulated by the Langmuir wave or scattered light of the primary instabilities under the high laser power condition. The secondary LPIs are important part in study of the multi-type LPI coupling process. Under certain conditions, the secondary instabilities can saturate some primary LPIs such as SRS and TPD, or induce some other LPIs such as SBS etc. In this project, we will investigate the secondary LPIs and their coupling process based on different laser and plasma parameters. Comprehend the competition among different LPIs and analyze the transfer of energy among the pump laser, scattered light, Langmuir wave, and ion-acoustic wave. Explore the change of plasma conditions and the nonlinear kinetic effects due to the secondary LPIs, and estimate the influence of these phenomena on the whole coupling process. Establish the multistage heating mechanism of electrons in the LPI coupling process. Study the generation mechanism and energy spectrum distribution of hot electrons. Provide scientific references to the ignition design and experiments in China.