Numerical studies of the implosion behavior and radiation field of Z-pinch dynamic hohlraums with embedded hard foam layer and capsule
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摘要: 利用自行开发的二维辐射磁流体力学程序，模拟研究在软泡沫柱外嵌套硬泡沫层、中心嵌套结构靶丸的动态黑腔整体动力学行为和热力学性能，以发现硬泡沫层对动态黑腔辐射场的影响和调制作用，以及腔靶耦合相互作用规律。对峰值50 MA、全上升时间300 ns的驱动电流，模拟结果的比较分析表明，嵌套硬泡沫层后靶丸感受到的辐射场温度开始升高时刻延后，辐射均匀更迅速，辐射温度第一峰下降，变化更顺滑，黑腔存在时间变长，达到10 ns以上，后期辐射温度大于350 eV，波形与美国靶丸点火成功实验中的黑腔辐射温度变化曲线比较接近；与没有靶丸的动态黑腔的相同区域辐射温度相比较，嵌入靶丸后，靶丸在烧蚀后期感受到的辐射驱动温度增加。故嵌套硬泡沫层和腔靶耦合都有益于聚变靶丸的烧蚀内爆。Abstract: In this paper, by means of the developed two dimensional radiation magneto-hydrodynamic Lagrangian code, the dynamic hohlraums, which are consisted of tungsten plasma shell and low density foam cylinder with or without an embedded hard foam layer on the cylinder and a capsule in the center, are simulated. We understand the effects of the hard foam layer on the hohlraum radiation field, and the coupling of capsule and hohlraum for the capsule fusion, by comparing the simulated results of different configuration hohlraums. After applying a hard foam layer on the low density foam cylinder, the time, uniformity, and the first peak value of radiation field, receipted by the capsule, is delayed, increased, and reduced, respectively. Furthermore, the radiation temperature on the capsule surface is increasing smoothly, and the dwelling time of the hohlraum is prolonged. For a driven current of peak 50 MA and full rise time 300 ns, the dwelling time can be longer than 10 ns, and the radiation temperature at the late time can be higher than 350 eV. The time variation of the radiation temperature is close to that measured in American National Ignition Facility (NIF) hohlraum in which the capsule was imploded and the fusion energy of 1.37 MJ was released. After embedding a capsule into the center of low density foam cylinder, the radiation temperature receipted by the capsule during the late process increases. This implies that both the hard foam layer and the coupling of the capsule and the dynamic hohlraum are good for the capsule ablating implosion.
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Key words:
- Z-pinch /
- dynamic hohlraum /
- radiation field modulation /
- inertial confinement fusion /
- capsule
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图 1 嵌套有硬泡沫层和靶丸的动态黑腔结构示意图
Figure 1. Used model configuration of dynamic hohlraum with a hard foam (CH) layer outside the soft foam column and an embedded capsule in the center
图 2 无靶丸情况下动态黑腔内爆流线和径向X光辐射功率随时间的变化
Figure 2. Trajectories of imploding plasma of dynamic hohlraum and X-ray power without a capsule in the center. The red lines, black lines, blue lines, and the green lines depict the W plasma, the hard foam layer, the soft foam, and the variation of X-ray power, respectively
图 3 无靶丸情况下动态黑腔内爆过程中各物质层的动能随时间变化
Figure 3. Time variations of kinetic energy of imploding plasmas in dynamic hohlraum without a capsule in the center
图 4 无靶丸情况下动态黑腔内爆过程中总动能随时间的变化
Figure 4. Time variation of total kinetic energy of imploding plasmas in dynamic hohlraum without a capsule in the center
图 5 无靶丸情况下动态黑腔内爆过程中全域平均物质温度和平均辐射温度随时间的变化
Figure 5. Time variations of averaged matter and radiation temperatures in dynamic hohlraum without a capsule in the center
图 6 无靶丸情况下，距中心0.3 cm，与中心连线与z轴成45°，60°，90° 的三个软泡沫物质点的密度和辐射温度随动态黑腔内爆形成过程的变化
Figure 6. Time variations of mass density and radiation temperature of three mass points, which are located in a circle of radius 0.3 cm with angles of 45°，60°，90° from z-axis, in soft foam (CH) without a capsule in the center
图 7 有靶丸、无硬泡沫层情况下，(a) 动态黑腔内爆流线和径向X光辐射功率随时间的变化，其中红色线为钨等离子体，青色线为软泡沫柱，品红色线为铍层，蓝色线为靶丸内层泡沫，以及绿色线为X光辐射功率; (b) 动态黑腔内爆过程中全域平均物质温度和平均辐射温度随时间的变化
Figure 7. Data of the dynamic hohlraum with a capsule but without a hard foam (CH) layer. (a) Imploding plasma trajectories and X-ray power. In figure (a), the red lines, cyan lines, fuchsine lines, blue lines, and the green lines depict the W plasma, the soft foam, the Be layer, the foam inside the capsule, and the variation of X-ray power, respectively. (b) Time variations of averaged matter and radiation temperatures over the whole simulation domain
图 8 有靶丸、无硬泡沫层情况下，动态黑腔内爆形成过程中各层等离子体动能和总动能随时间的变化
Figure 8. Time variations of the kinetic energies of all imploding plasma shells and total kinetic energy in the dynamic hohlraum with a capsule but without a hard foam (CH) layer
图 9 有靶丸、无硬泡沫层情况下，半径为0.3 cm的靶丸表面上，三个铍物质点（它们的半径方向与z轴分别成30°，60°和90°）的密度和辐射温度随动态黑腔内爆形成过程的变化
Figure 9. In the dynamic hohlraum with a capsule but without a hard foam (CH) layer, the time variations of Be mass density and radiation temperature of the three mass points, which are located in a circle of radius 0.3 cm with angles of 30°，60°，and 90° from z-axis
图 10 有靶丸和硬泡沫层情况下，动态黑腔内爆流线和径向X光辐射功率随时间的变化及动态黑腔内爆过程中总动能随时间的变化
Figure 10. Data of the dynamic hohlraum with a capsule and a hard foam (CH) layer. (a) The imploding plasma trajectories and X-ray power. In figure (a), the red lines, black lines, cyan lines, fuchsine lines, blue lines, and the green line depict the W plasma, the hard foam layer, the soft foam, the Be layer, the foam inside the capsule, and the variation of x-ray power, respectively. (b) The time variation of total kinetic energy over the whole hohlraum
图 11 有靶丸和硬泡沫层情况下，动态黑腔内爆形成过程中各层等离子体动能和靶丸中各层动能随时间的变化
Figure 11. Time variations of kinetic energies of all imploding plasma shells in the whole hohlraum and only in the capsule for the dynamic hohlraum with a capsule and a hard foam (CH) layer
图 12 有靶丸和硬泡沫层情况下，动态黑腔内爆过程中全域平均物质温度和辐射温度，及各层物质平均温度随时间的变化
Figure 12. Time variations of totally averaged matter and radiation temperatures, and individually averaged matter temperature of the shells, in the dynamic hohlraum formation, with a capsule and a hard foam (CH) layer
图 13 有靶丸和硬泡沫层情况下，(a)半径为0.3 cm的靶丸表面上，三个铍物质点的密度和辐射温度随动态黑腔内爆形成过程的变化；(b)辐射温度沿赤道（90°方向）径向的分布和演化
Figure 13. In the dynamic hohlraum with a capsule and a hard foam (CH) layer, (a) the time variations of Be mass density and radiation temperature of three mass points, which are located in a circle of radius 0.3 cm; (b) radial profile of the radiation temperature along the equator at different time
图 14 NIF上的黑腔辐射温度（文献[2]中图1）波形与Z箍缩动态黑腔中靶丸感受到的辐射温度（90°方向）变化的比较
Figure 14. Comparison between the huhlraum radiation temperature of NIF (data from Fig.1 in Ref. [2]) and the radiation temperature, which is received by the capsule in the Z-pinch dynamic hohlraum with an embedded hard foam layer, at 90° from z-axis
图 15 有靶丸和硬泡沫层情况下，模拟区域中辐射温度在几个特征时刻的空间分布伪色彩图
Figure 15. Color contour maps of radiation temperature distribution in the simulated domain in the dynamic hohlraum with a capsule and a hard foam (CH) layer
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