The physics of laser-plasma interaction is studied on the Shenguang III prototype laser facility under conditions relevant to inertial confinement fusion designs. A sub-millimeter-size underdense hot plasma is created by ionization of a low-density plastic foam by four high-energy (3.2 kJ) laser beams. An interaction beam is fired with a delay permitting evaluation of the excitation of parametric instabilities at different stages of plasma evolution. Multiple diagnostics are used for plasma characterization, scattered radiation, and accelerated electrons. The experimental results are analyzed with radiation hydrodynamic simulations that take account of foam ionization and homogenization. The measured level of stimulated Raman scattering is almost one order of magnitude larger than that measured in experiments with gasbags and hohlraums on the same installation, possibly because of a greater plasma density. Notable amplification is achieved in high-intensity speckles, indicating the importance of implementing laser temporal smoothing techniques with a large bandwidth for controlling laser propagation and absorption.

中文翻译：

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神光III原型机上低密度目标的激光-等离子体相互作用物理学用于直接驱动惯性约束聚变的研究

在与惯性约束聚变设计有关的条件下，在神光三号原型激光设备上研究了激光-等离子体相互作用的物理学。通过使用四束高能（3.2 kJ）激光束对低密度塑料泡沫进行电离，可产生亚毫米大小的密集热等离子体。发射延迟延迟的相互作用光束，以评估在等离子体演化的不同阶段的参数不稳定性的激发。多种诊断可用于等离子体表征，散射辐射和加速电子。利用辐射流体动力学模拟分析了实验结果，该模拟考虑了泡沫离子化和均质化。所测量的受激拉曼散射水平比同一装置上使用气袋和大喇叭的实验所测量的水平高出近一个数量级，这可能是因为血浆密度更高。在高强度散斑中实现了显着的放大，表明实施具有大带宽的激光时间平滑技术以控制激光传播和吸收的重要性。