论文标题
用泡沫过涂料缓解激光印迹
Mitigating laser imprint with a foam overcoating
论文作者
论文摘要
有人建议由于其低密度而减少激光烙印。在本文中，使用二维辐射流体动力代码闪光灯来研究和表征激光印迹的强度，通过分析面积密度扰动。除了传导区域的热平滑（在消融前部和临界密度表面）和消融前部的质量消融外，还有两个重要因素用于缓解激光烙印。首先，辐射消融动态调节密度分布不仅增加了扰动消融前振荡的频率，而且还可以减少振荡的振幅。其次，较大的冲击压缩区域可降低扰动的冲击前振荡的幅度。消融前部和冲击前方的扰动越小，面积密度摄入越小。基于上述物理机制，用泡沫来减轻激光烙印的最佳方法是，当泡沫的面积密度驱动振荡时，动态调制的密度分布进一步降低了摄动的振幅达到固体CH的幅度。借助尺寸分析提出了泡沫参数的最佳范围来减轻激光痕迹：泡沫厚度约为扰动波长的2〜3倍，泡沫密度约为与关键密度相对应的质量密度的1/2〜3/2倍。
Foam has been suggested to reduce laser imprint because of its low density. In this paper, the two-dimensional radiation hydrodynamic code FLASH is applied to investigate and characterize the strength of laser imprint through analyzing areal density perturbation. There are two important factors for the mitigation of laser imprint besides the thermal smoothing of the conduction region (between the ablation front and the critical density surface) and the mass ablation of the ablation front. First, radiation ablation dynamically modulates density distribution not only to increase the frequency of the perturbed ablation front oscillation but also to decrease the amplitude of oscillation. Second, a larger length of the shocked compression region reduces the amplitude of the perturbed shock front oscillation. The smaller the perturbation of both ablation front and shock front, the smaller the areal density perturbation. Based on the above physical mechanisms, the optimal way of mitigating laser imprint with foam is that the dynamically modulated density distribution further reduces the amplitude of perturbation reaching the solid CH when the areal density perturbation of foam oscillates to the first minimum value. The optimal ranges of foam parameters to mitigate laser imprint are proposed with the aid of dimensional analysis: the foam thickness is about 2~3 times the perturbation wavelength, and the foam density is about 1/2~3/2 times the mass density corresponding to the critical density.
