间接驱动装置中柱形腔内激光束传输叠加特性研究

在惯性约束聚变装置中，激光集束在腔内的传输叠加特性对实现靶丸的有效压缩极为重要。为了更为深入地了解激光集束在腔内的传输叠加特性，针对典型的柱形腔结构及其光路排布，建立了真空腔内的光传输模型，数值模拟和讨论了多集束激光在腔内的传输叠加情况。考虑到激光束的交叉重叠会带来交叉光束能量转移、激光等离子体相互作用等问题，提出通过确定集束间相互分离的特征面位置，进而从偏振特性和热斑占比等方面对多集束激光在腔内的传输及叠加特性进行分析。结果表明，多集束激光在腔内传输时，内环集束和外环集束激光先分离，之后内环相邻集束之间和外环相邻集束之间各自分离。单端集束在腔内传输过程中，其均匀性从靶腔注入孔到腔壁的过程中呈现先变差后变好、再变差的趋势，而热斑的峰值强度随着离焦量的增加不断减小，热斑所占的面积则先增加后减小。此外，激光束在腔内传输时偏振度随腔内传输距离的大小并无明显变化。

Abstract

In inertial confinement fusion facilities, the propagation characteristic of laser quads in the cylindrical hohlraum is especially important for achieving the effective compression of target. In order to understand the irradiation characteristics of laser quads in hohlraum, the propagation model of laser quads in vacuum cylindrical hohlraum for the typical structure and beam configuration has been built up. The propagation characteristics of multiple laser quads have been numerically simulated. Considering the crossing beam energy transfer and laser plasma interaction caused by laser quads overlapping and crossing, the method for determining the characteristic plane where laser quads separate with each other in cylindrical hohlraum has been proposed, and the propagation and overlapping characteristics of the quads from the aspects of polarization characteristics and fractional hot spots have been further analyzed. The results show that during the propagation of multiple quads in cylindrical hohlraum, the inner cone and outer cone separate initially, followed by the separation of adjacent laser quads of both the inner cone and outer cone. When all quads for a single laser entrance hole propagating inside cylindrical hohlraum, the irradiation uniformity of the superposition spots first degrades and improves, then degrades again while propagating from the laser entrance hole to the wall, but peak intensity of hot spots degrades with the increasing of the defocusing distance，and the proportion of hot spots first increases and degrades. In addition, the polarization degree of the multiple laser quads remains almost unchanged during the propagation in hohlraum.

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文萍, 李泽龙, 钟哲强, 张彬. 间接驱动装置中柱形腔内激光束传输叠加特性研究[J]. 光学学报, 2016, 36(1): 0114001. Wen Ping, Li Zelong, Zhong Zheqiang, Zhang Bin. Study on Propagation Characteristics of Laser Quads in Cylindrical Hohlraum for Indirect Drive Facility[J]. Acta Optica Sinica, 2016, 36(1): 0114001.

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