Large growth, planar Rayleigh–Taylor experiments on Nova
Large growth, planar Rayleigh–Taylor experiments on Nova
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DOI：
10.1063/1.860113
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发表时间：
1992-04
期刊：
影响因子：
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通讯作者：
B. Remington;S. Haan;S. Glendinning;J. Kilkenny;D. Munro;R. Wallace
中科院分区：
文献类型：
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作者：
B. Remington;S. Haan;S. Glendinning;J. Kilkenny;D. Munro;R. Wallace
在Nova激光装置上进行了一组间接驱动实验，以研究使用成形激光脉冲的大增长瑞利-泰勒不稳定性。通过X射线消融加速氟硅平面箔。使用边缘X线摄影测量箔片轨迹。在使用正面射线照相术的单独实验中，测量光学深度的对比度作为时间的函数，从中推导出50 μm波长初始正弦表面扰动的演变。保持其他参数不变，初始扰动的幅度在单独的拍摄中变化高达30倍。相比之下，具有最小初始扰动的箔表现出75的生长因子。具有大初始振幅扰动的翼片给出了6或更小的增长因子，并显示了非线性瑞利-泰勒不稳定性的“气泡和尖峰”形状特征。如果选择合适的不透明度模型，二维计算机模拟与测量的翼型轨迹和扰动增长的比较显示出良好的一致性。在线性制度中，观察到的增长率是60%-75%的经典，减少主要归因于烧蚀稳定。观察到的谐波产生的开始，信号过渡到非线性制度，是很好地预测了三阶理论。
A set of indirect‐drive experiments to study large growth Rayleigh–Taylor instability using shaped laser pulses at the Nova laser facility has been conducted. Planar foils of fluorosilicone were accelerated by x‐ray ablation. The foil trajectory was measured using edge‐on radiography. In separate experiments using face‐on radiography, contrast in optical depth was measured as a function of time, from which the evolution of 50 μm wavelength initially sinusoidal surface perturbations was deduced. Holding other parameters fixed, the amplitude of the initial perturbation was varied by up to a factor of 30 in separate shots. The foils with the smallest initial perturbation exhibited growth factors of 75 in contrast. Foils with large initial amplitude perturbation gave growth factors of 6 or less, and displayed the ‘‘bubble‐and‐spike’’ shape characteristic of the nonlinear Rayleigh–Taylor instability. Comparisons of two‐dimensional computer simulations with both the measured foil trajectory and the perturbation growth show good agreement, provided that a suitable opacity model is chosen. In the linear regime the observed growth rates are 60%–75% of classical, the reduction attributed primarily to ablative stabilization. The observed onset of harmonic generation, signaling the transition into the nonlinear regime, is well predicted by third‐order theory.