Competition between the stimulated Raman and Brillouin scattering instabilities in 0.35- microm irradiated CH foil targets.
Competition between the stimulated Raman and Brillouin scattering instabilities in 0.35- microm irradiated CH foil targets.
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DOI：
10.1103/physrevlett.62.2829
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发表时间：
1989-06
影响因子：
8.6
通讯作者：
Baldis;Young;Drake;Kruer;Estabrook;Williams;Johnston
中科院分区：
文献类型：
--
作者：
Baldis;Young;Drake;Kruer;Estabrook;Williams;Johnston
由于受激布里渊散射的显着水平的存在下，受激拉曼散射的散射光谱的修改的第一个实验证据。所观察到的光谱，以及在这个和其他实验中观察到的光谱拉曼间隙，解释在离子波的存在下的拉曼散射的修改后的增长。PACS编号：52.40.Nk，52.35.Fp，52.35.Mw受激拉曼散射（SRS）已成为激光等离子体中最重要的参量不稳定性。SRS是一种三波相互作用，其中泵浦波（激光）衰减为电子等离子体和散射光波。受激喇曼散射除了在激光等离子体中具有重要意义外，由于激光能量可以大量地转换为拉曼光，它在惯性约束聚变（ICF）中也具有重要意义。[2]在理解受激布里渊散射（SBS）中，一个重要的和相对较新的问题是它在存在离子声波的情况下的增长。近年来，这个问题引起了大量的理论研究。使用汤姆逊散射的实验已经诊断出与这些不稳定性相关的电子等离子体波和离子声波的时间演化，并清楚地表明，SRS的生长可以通过存在大水平的离子波来修改。在这些实验中，通过直接探测与不稳定性相关的电子等离子体波和离子声波，观察到SRS和SBS之间的竞争。这些实验是用比我们在这里讨论的波长长得多的激光波长（10.6 pm）进行的，他们使用的是预先形成的等离子体，没有SRS光谱。在本文中，我们提出的第一个实验证据的修改的散射电磁频谱的SRS由于SBS的存在下，感兴趣的ICF的激光等离子体条件下。随时间变化的散射光谱显示出特征性的拉曼间隙，其时间行为可以用观察到的SBS散射光来解释。在所有已发表的实验中，SRS谱中都出现了差距;虽然我们的结果没有提供关于差距的全面解释，但它们给出了与两种不稳定性之间耦合或竞争的假设一致的解释。
The first experimental evidence of modification of the scattered light spectrum of stimulated Raman scattering due to the presence of significant levels of stimulated Brillouin scattering is presented. The observed spectrum, as well as the spectral Raman gap observed in this and other experiments, is explained in terms of the modified growth of Raman scattering in the presence of ion waves. PACS numbers: 52.40.Nk, 52.35.Fp, 52.35.Mw Stimulated Raman scattering (SRS) has become the most important parametric instability in laser-produced plasmas. SRS is a three-wave interaction in which the pump wave (laser light) decays into an electron plasma and a scattered light wave. Apart from the intrinsic interest of SRS in laser-produced plasmas, it has important implications in inertial confinement fusion (ICF) due to the large conversion of laser energy into Raman light. 2 An important and relatively new issue in the understanding of SRS is its growth in the presence of ion acoustic waves from stimulated Brillouin scattering (SBS). This problem has attracted considerable theoretical work ' in recent years. Experiments using Thomson scattering have diagnosed the temporal evolution of electron plasma waves and ion acoustic waves associated with these instabilities, and clearly demonstrated that the growth of SRS can be modified by the presence of large levels of ion waves. In those experiments, the competition between SRS and SBS was observed by directly probing the electron plasma waves and ion acoustic waves associated with the instabilities. Those experiments were performed with a much longer laser wavelength (10.6 pm) than we will be discussing here, they used preformed plasmas, and no SRS light spectrum was available. In this paper, we present the first experimental evidence of modification of the scattered electromagnetic spectrum of SRS due to the presence of SBS, under laser-plasma conditions of interest to ICF. The timedependent scattered spectrum shows the characteristic Raman gap, with a temporal behavior that can be explained in terms of the observed SBS scattered light. The gap in the SRS spectrum has been seen in all published experiments; although our results do not provide a total explanation about the gap, they present an explanation consistent with the assumption of coupling or competition between the two instabilities.