Simulations of laser imprint for Nova experiments and for ignition capsules. Revision 1
Simulations of laser imprint for Nova experiments and for ignition capsules. Revision 1
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Nova 实验和点火胶囊的激光压印模拟。
DOI：
10.1063/1.872339
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发表时间：
1996
期刊：
影响因子：
--
通讯作者：
J. Knauer
中科院分区：
文献类型：
--
作者：
S. Weber;S. Glendinning;D. Kalantar;M. Key;B. Remington;J. Rothenberg;E. Wolfrum;C. Verdon;J. Knauer
在直接驱动ICF中，激光照射的不均匀在烧蚀前沿的种子波纹中被称为‘’印记‘’。这些不均匀在胶囊内爆过程中增长，如果最初足够大，可能会穿透胶囊外壳，阻碍点火，或降低烧伤。最近在LLNL的Nova激光器上进行的测试各种光束平滑条件的实验模拟了IMPRIME。最常用的激光强度类似于点火胶囊脉冲形状的早期部分，1{大约等于}10{sup 13}W/cm{sup 2}。模拟结果与印迹调制的大部分测量结果相吻合。还模拟了印迹对国家点火设施(NIF)直接驱动点火胶囊的影响。据预测，印迹将提供与本征表面光洁度相当的调制，其表面光洁度为{约}10 nm rms。调制生长是使用Haan[Phys.A{BOLD 39}，5812()]模型，由解析色散关系得到线性增长因子作为球谐模数的函数。据预测，烧蚀前沿的幅度将变得基本上是非线性的，因此饱和校正很大。还对二维多模生长进行了直接数值模拟。预计胶囊外壳将保持完好，这为相信可以实现点火奠定了基础。参考文献27，图10。
In direct drive ICF, nonuniformities in laser illumination seed ripples at the ablation front in a process called ``imprint``. These nonuniformities grow during the capsule implosion and, if initially large enough, can penetrate the capsule shell, impede ignition, or degrade burn. Imprint has been simulated for recent experiments performed on the Nova laser at LLNL examining a variety of beam smoothing conditions. Most used laser intensities similar to the early part of an ignition capsule pulse shape, 1 {approx_equal} 10{sup 13} W/cm{sup 2} . The simulations matched most of the measurements of imprint modulation. The effect of imprint upon National Ignition Facility (NIF) direct drive ignition capsules has also been simulated. Imprint is predicted to give modulation comparable to an intrinsic surface finish of {approximately}10 nm RMS. Modulation growth was examined using the Haan [Phys. Rev. A {bold 39}, 5812 (1989)] model, with linear growth factors as a function of spherical harmonic mode number obtained from an analytic dispersion relation. Ablation front amplitudes are predicted to become substantially nonlinear, so that saturation corrections are large. Direct numerical simulations of two-dimensional multimode growth were also performed. The capsule shell is predicted to remain intact, which gives a basis for believing that ignition can be achieved. 27 refs., 10 figs.