激光等离子体不稳定性及其抑制方案研究

受激拉曼散射、受激布里渊散射等激光等离子体不稳定性（LPI）是激光等离子体物理领域最重要的研究课题之一。特别是在激光驱动的惯性约束聚变中，LPI会造成相当份额的激光能量损失，破坏辐射对称性，产生的超热电子还会预热靶丸，进而影响压缩效率和聚变能量增益。近期，在美国国家点火装置上开展的实验表明对LPI物理过程的充分理解和有效控制对成功实现ICF点火至关重要。我们对近期LPI方面的一系列研究进展进行了简单介绍与讨论。首先，回顾了描述LPI过程的三波耦合理论，由此得出了LPI在线性阶段的增长率。接着讨论了一些复杂情景下的LPI物理过程，譬如LPI的非线性发展阶段、级联LPI、多光束LPI以及LPI间的非线性耦合。最后，着重介绍了一系列抑制LPI的技术方案，包括束匀滑技术、光束时域整形、宽带激光、偏振旋转激光以及外加磁场等。

Laser plasma instabilities and their suppression strategies

The issue of laser plasma instabilities (LPIs) including stimulated Raman scattering, stimulated Brillouin scattering and so on is one of the most fascinating subjects in laser plasma physics. In particular, LPIs may cause significant laser energy loss and produce hot electrons to preheat fusion targets, which affect target compression and fusion energy gain in laser-driven inertial confinement fusion. Recent experiments carried out on the National Ignition Facility, the largest laser facility in the world for laser fusion, indicate that the understanding and the control of LPIs are essential to the realization of laser fusion. In this paper, we present a review on recent studies of LPIs. Firstly, we retrospect the classical theoretical model of LPIs, which offers a good estimation of growth rate in the linear development stage. Then, we discuss some progresses on the understanding of LPIs in more complex and real scenarios, such as LPI development in the nonlinear regions, cascaded LPIs, multi-beam LPIs, and nonlinear couplings between LPIs. Following the exploration of LPI physics, we emphasize on the strategies for the control of LPIs, including beam smoothing techniques, temporal profile shaping, broadband laser, laser polarization rotation, external magnetic field and so on.