Investigation of the yield degradation of the first shaped-pulse implosion experiments on the SG-III laser facility

Abstract

The first shaped-pulse inertial confinement fusion implosion experiments of the deuterium-deuterium (DD) gas-filled plastic (CH) capsules have been done at the SG-III laser facility [He and Zhang, Eur. Phys. J. D 44, 227 (2007); Zheng et al., Matter Radiat. Extremes 2, 243 (2017)]. The measured neutron yield is much lower than that predicted by one-dimensional (1D) simulations, and as the trough duration of the drive source increases, the neutron yield over clean decreases rapidly to less than 1%. To understand the primary reason for this decrease in yield, we numerically simulated the capsule implosion to investigate the effects of the support tent and the various capsule-surface defects on the implosion performance. The validity of the underlying 1D model is supported by the agreement between the results of the 1D simulation and experimental data for the implosion trajectory and fuel areal density. Compared with square-pulse implosions, shaped-pulse implosions exhibit a much larger growth in hydrodynamic instabilities. The numerical neutron yields of the shaped-pulse implosions are much more sensitive to perturbations seeded by inward-facing divots on the outer ablator surface. Yield degradation is mainly caused by a reduction in mechanical power exerted by the distorted shell on the central DD gas, which significantly lowers the fuel temperature and pressure.

Improving symmetry tuning with I-raum in indirect-driven implosions

“…近年来, 在我国100 kJ激光装置上, 基于直柱 黑腔开展的两台阶整形脉冲驱动内爆实验研究已 经取得较大进展 [7,8] . 为了进一步提高内爆性能, 物 理设计要求使用三台阶整形脉冲驱动开展内爆物 理实验研究.…”

“…每束激光脉冲采用相同的参 与100 kJ激光装置上其他内爆实验诊断排布 相同 [6−9] , 实验中采用多种诊断设备, 分别测量获 得表征黑腔等离子体运动、X光辐射温度、内爆不 对称性、中子发射峰值时刻和聚变中子产额等关键 物理特性的实验数据. 采用X光针孔相机从靠近 激光注入孔法线方向测量黑腔等离子体发射X光 图像, 观察激光注入和黑腔等离子体运动情况 [7] .…”

“…实验中采用X光针孔相机通过激光注入孔测 量获得黑腔等离子体发射X光的时间积分图像 [7] , 实验中, 使用背向散射光测量系统抽样测量部 分光束的背向散射光能量和份额 [9] . I n P r e s s 注入孔发射的X光辐射功率 [28] , 并给出黑腔局部…”

Predicting spherical symmetry degeneration of non-infrared deuterium ice layer in a cryogenic capsule

“…Before the DT capability is brought online, deuterium-deuterium (DD) is a good surrogate to help understand implosion physics and optimize target fabrication because of no radioactivity and low-cost manipulation [15][16][17]. In a direct-drive target, the capsule filled with DD is located at the center of a smooth and partial sphere.…”