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辐射冲击波波后物质具有辐射属性, 它通过扰动界面引起的Richtmyer-Meshkov(RM)不稳定性的增长有别于通常的冲击波. 在高功率激光装置上开展冲击波波后辐射效应对界面不稳定性增长影响的实验研究, 认识波后辐射对界面增长的影响过程及规律, 有助于提高高能量密度条件下RM不稳定性演化规律的认识水平及预测能力. 基于神光III原型高功率激光装置, 设计并开展了两种激光驱动条件下的界面流体力学不稳定性实验, 研究波后辐射效应对界面RM不稳定性增长的影响. 实验中在较高功率密度驱动条件下CHBr扰动样品未见明显的扰动增长, 结合模拟分析发现较高功率密度条件下辐射前驱波波阵面和冲击波波阵面明显分离, 辐射前驱波在冲击波到达扰动界面前烧蚀扰动界面, 改变了界面的初始状态, 界面不稳定性增长过程中密度梯度的增大和界面Atwood数的减小抑制了界面RM不稳定性的增长.
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关键词:
- 辐射冲击波 /
- Richtmyer-Meshkov不稳定性 /
- 密度梯度尺度 /
- 烧蚀速度 /
- Atwood数
Radiative shocks are ubiquitous in stellar environments and are characterized by high temperature plasma emitting a considerable fraction of their energy as radiation. Radiative shocks occur commonly in nature, especially in astronomical systems and inertial confinement fusion. The study of the effects of radiation on Richtmyer-Meshkov (RM) instability will improve our ability to understand and predict the evolution of RM instability under high energy density conditions. A few experiments have been performed to compare the radiative case with the non-radiative case in Rayleigh-Taylor (RT) instability, thereby studying how the radiative effects change the evolution of RT instability, but the interplay between RM instability and radiative shock has been studied rarely. This paper reports mainly the role of radiation in the changing of the RM instability. Two experiments are performed at Shenguang III prototype laser facility, the RM instability growth data are obtained by varying the laser intensity. The laser intensity for high-drive experiment is approximately 60% greater than that for low-drive experiment. The target consists of a multiple layer in the axial direction, in which the first layer is a 15μm-thick CH sample serving as an ablator, followed by a 10 μm-thick aluminum used as a shield layer to prevent the preheat effect. The next layer is a 350-μm-thick SiO2 foam, which is used as a material to produce a radiative shock. The last layer is the CH perturbed sample. There is a sinusoidal perturbation on the surface of CH sample which is adjacent to the SiO2 foam. The target is irradiated by four overlapping laser beams, and the laser beams produce a large pressure that drives a shock wave, whose velocity can be changed by varying the laser intensity, into the target package. In the experiments, shock-generated radiative fluxes first ablate the unstable interface which the shock has not passed through, then the shock transmits the unstable interface to produce the RM instability. The images of unstable interface are captured using side-on x-ray radiography, and the experimental results show that the RM growth is suppressed in the experiment for the higher laser intensity. Radiation hydrodynamic code Multi1D is used to evaluate the electron temperature, shock velocity, and electron density. The simulations show that the foam temperature in the high-drive case can reach 80 eV in the front of shock, this energy flows away from the shock front, generating a radiative precursor ahead of the shock. The radiative precursor velocity of 270 km/s is much larger than the shock velocity of 170 km/s, the radiative precursor arrives at the unstable interface before the shock and ablates the unstable interface, so the radiative flux changes the initial conditions of unstable interface. When the shock propagates through the unstable interface, the ablation increases the density gradient length scale and reduces the Atwood number of the unstable interface, so the RM growth is suppressed in the high-drive case because of the ablation of the radiative precursor. -
Keywords:
- radiative shock /
- Richtmyer-Meshkov instability /
- density-gradient scale /
- ablation velocity /
- Atwood number
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Zhuang L X, Yin X Y, Ma H Y 2009 Fluid Mechanics (Hefei: University of Science and Technology of China Press) p268 (in Chinese)
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图 1 激光驱动界面不稳定性研究主靶结构示意图
Fig. 1. Schematic view of the hydrodynamic instability target driven by laser.
图 4 激光驱动界面不稳定性实验示意图
Fig. 4. Schematic of the laser driven hydrodynamic instability experiment.
图 5 激光功率密度1 × 1015 W/cm2条件下CHBr样品的RM不稳定性增长图像
Fig. 5. RM growth image at a laser intensity of 1 × 1015 W/cm2.
图 6 激光功率密度1.6 × 1015 W/cm2条件下CHBr样品的界面不稳定性增长图像
Fig. 6. RM growth image at a laser intensity of 1.6 × 1015 W/cm2.
图 7 激光功率密度1 × 1015 W/cm2条件下CHBr样品阴影区X轴方向光强分布
Fig. 7. Horizontal lineouts of perturbation sample images at a laser intensity of 1.6 × 1015 W/cm2.
图 8 激光功率密度1.6 × 1015 W/cm2条件下CHBr样品阴影区X轴方向光强分布
Fig. 8. Horizontal lineouts of perturbation sample images at a laser intensity of 1 × 1015 W/cm2.
图 9 模拟激光功率密度1.6 × 1015 W/cm2条件下各层物质运动及冲击波、辐射前驱波阵面
Fig. 9. Simulated shock trajectory, radiative precursor trajectory and the movement of materials at a laser intensity of 1.6 × 1015 W/cm2.
图 10 模拟SiO2泡沫和CHBr层电子温度变化
Fig. 10. One-dimensional profiles of electron temperature of SiO2 foam and CHBr.
图 11 模拟不同时刻SiO2泡沫中电子密度和电子温度的变化 (a) 0.9 ns; (b) 2.0 ns
Fig. 11. Simulated one-dimensional profiles of electron temperature and electron density at different time: (a) 0.9 ns; (b) 2.0 ns.
图 12 模拟激光功率密度1 × 1015 W/cm2条件下各层物质运动及冲击波、辐射前驱波阵面
Fig. 12. Simulated shock trajectory, radiative precursor trajectory and the movement of materials at a laser intensity of 1 × 1015 W/cm2.
图 13 模拟不同时刻SiO2泡沫中电子密度和电子温度的变化 (a) 1.2 ns; (b) 2.5 ns
Fig. 13. Simulated electron density and electron temperature in SiO2 foam for different time: (a) 1.2 ns; (b) 2.5 ns.
图 14 模拟激光功率密度1.6 × 1015 W/cm2条件下 (a) CHBr样品烧蚀速度, (b)界面处密度梯度标长
Fig. 14. Simulated (a) ablation velocity and (b) density-gradient scale length on the surface at a laser intensity of 1.6 × 1015 W/cm2.
图 15 模拟两种激光功率密度条件下界面处密度梯度标长变化
Fig. 15. Simulated density-gradient scale length on the surface at the different laser intensity.
图 16 模拟两种激光功率密度条件下扰动界面处的Atwood数变化
Fig. 16. Simulated Atwood number on the surface at the different laser intensity.
表 1 激光功率密度1 × 1015 W/cm2条件下激光参数统计
Table 1. Laser parameters at a laser intensity of 1 × 1015 W/cm2.
发次号 记录图像
时刻/ns设计能
量/J实际输出
能量/J实际输出能量与
设计能量偏差/%057 5 2000 1931 –3.45 056 6 2000 1983 –0.85 054 8 2000 1988 –0.60 
下载: 导出CSV
表 2 激光功率密度1.6 × 1015 W/cm2条件下激光参数统计
Table 2. Laser parameters at a laser intensity of 1.6 × 1015 W/cm2.
发次号 记录图像
时刻/ns设计能
量/J实际输出
能量/J实际输出能量与
设计能量偏差/%061 5 3200 3080 –3.75 055 8 3200 2812 –12.1
下载: 导出CSV
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[1] Remington B A, Drake R P, Takabe H, Arnett D 2000 Phys. Plasmas 7 1641
Google Scholar
[2] Remington B A, Drake R P, Ryntov D D 2006 Rev. Mod. Phys. 78 755
Google Scholar
[3] Kuranz C C, Park H S, Remington B A, et al. 2011 Astrophys. Space Sci. 336 207
Google Scholar
[4] Trantham M R, Kuranz C C, Malamud G, et al. 2013 High Energy Density Phys. 9 303
Google Scholar
[5] Flaig M, Plewa T, Keiter P A, Drake R P, Grosskopf M, Kuranz C, Park H S 2014 High Energy Density Phys. 12 35
Google Scholar
[6] Li J W, Pei W B, He X T, Li J H, Zheng W D, Zhu S P, Kang W 2013 Phys. Plasmas 20 082707
Google Scholar
[7] Pak A, Divol L, Gregori G, et al. 2013 Phys. Plasmas 20 056315
Google Scholar
[8] Reighard A B, Drake R P, Dannenberg K K, et al. 2006 Phys. Plasmas 13 082901
Google Scholar
[9] Stehlé C, González M, Kozlva M, et al. 2010 Laser Part. Beams 28 253
Google Scholar
[10] Kuranz C C, Drake R P, Huntington C M, et al. 2013 High Energy Density Phys. 9 315
Google Scholar
[11] Michaut C, Vinci T, Boireau L, et al. 2007 Astrophys. Space Sci. 307 159
Google Scholar
[12] Chaulagain U, Stehlé C, Larour J, et al. 2015 High Energy Density Phys. 17 106
Google Scholar
[13] Cotelo M, Velarde P, Varga A G, Portillo D, Stehlé C, Chaulagain U, Kozlova M, Larour J, Suzuki-Vidal F 2015 High Energy Density Phys. 17 68
Google Scholar
[14] Vinci T, Koenig M, Benuzzi-Mounaix A, Michaut C, Boireau L, Leygnac S, Bouquet S, Peyrusse O, Batani D 2006 Phys. Plasmas 13 010702
Google Scholar
[15] Michel T, Albertazzi B, Mabey P, Rigon G, Lefevre F, Som L, Barroso P, Egashira S, Kumar R, Michaut C, Ota M, Ozaki N, Sakawa Y, Sano T, Falize E, Koenig M 2020 Astrophys. J. 25 888
[16] Keiter P A, Drake R P, Perry T S, Robey H F, Remington B A, Iglesias C A, Wallace R J 2002 Phys. Rev. Lett. 89 165003
Google Scholar
[17] Nilsen J, Kritcher A L, Martin M E, Tipton R E, Whitley H D, Swift D C, Döppner T, Bachmann B L, Lazicki A E, Kostinski N B, Maddox B R, Collins G W, Glenzer S H, Falcone R W 2020 Matter Radiat. Extremes 5 018401
Google Scholar
[18] Huntington C M, Shimony A, Trantham M, et al. 2018 Phys. Plasmas 25 052118
Google Scholar
[19] Kuranz C C, Park H S, Huntington C M, et al. 2018 Nat. Commun. 9 1564
Google Scholar
[20] 庄礼贤, 尹协远, 马晖扬 2009 流体力学(合肥: 中国科学技术大学出版社) 第268页
Zhuang L X, Yin X Y, Ma H Y 2009 Fluid Mechanics (Hefei: University of Science and Technology of China Press) p268 (in Chinese)
[21] Motl B J 2008 Ph. D. Dissertation (Wisconsin: University of Wisconsin- Madison)
[22] Dimonte G, Frerking C E, Schneider M, Remington B 1995 Phys. Plasmas 3 614
[23] 张璐, 杨家敏 2012 61 045203
Google Scholar
Zhang L, Yang J M 2012 Acta Phys. Sin. 61 045203
Google Scholar
[24] Martinez D A, Smalyuk V A, MacPhee A G, et al. 2017 Phys. Plasmas 24 102707
Google Scholar
[25] 肖德龙, 孙顺凯, 薛创, 张扬, 丁宁 2015 64 235203
Google Scholar
Xiao D L, Sun S K, Xue C, Zhang Y, Ding L 2015 Acta Phys. Sin. 64 235203
Google Scholar
[26] 蒙世坚, 黄展常, 甯家敏, 胡青元, 叶繁, 秦义, 许泽平, 徐荣昆 2016 65 075201
Google Scholar
Meng S J, Huang Z C, Ning J M, Hu Q Y, Ye F, Qin Y, Xu Z P, Xu R K 2016 Acta Phys. Sin. 65 075201
Google Scholar
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