Lawrence Livermore National Laboratory, Livermore, California 94551, USA.
Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
Phys Rev Lett. 2014 May 16;112(19):195001. doi: 10.1103/PhysRevLett.112.195001. Epub 2014 May 12.
First measurements of the in-flight shape of imploding inertial confinement fusion (ICF) capsules at the National Ignition Facility (NIF) were obtained by using two-dimensional x-ray radiography. The sequence of area-backlit, time-gated pinhole images is analyzed for implosion velocity, low-mode shape and density asymmetries, and the absolute offset and center-of-mass velocity of the capsule shell. The in-flight shell is often observed to be asymmetric even when the concomitant core self-emission is round. A ∼ 15 μm shell asymmetry amplitude of the Y(40) spherical harmonic mode was observed for standard NIF ICF hohlraums at a shell radius of ∼ 200 μm (capsule at ∼ 5× radial compression). This asymmetry is mitigated by a ∼ 10% increase in the hohlraum length.
首次在国家点火装置（NIF）上对内爆惯性约束聚变（ICF）胶囊的飞行中形状进行了测量，使用二维 X 射线射线照相术。对面积背光照、时间门控针孔图像序列进行了分析，以获得内爆速度、低阶形状和密度不对称性，以及胶囊壳的绝对偏移量和质心速度。即使伴随的核心自发射是圆形的，飞行中的外壳也经常观察到不对称。在壳半径约为 200 μm（胶囊约为 5×径向压缩）的标准 NIF ICF 空心圆柱体中，观察到 Y（40）球谐模式的约 15 μm 壳不对称幅度。通过将空心圆柱体长度增加约 10%，可以减轻这种不对称性。
