Low-mode asymmetries have emerged as one of the primary challenges to achieving high-performing inertial confinement fusion (ICF) implosions. In direct-drive ICF, an important potential seed of such asymmetries is the capsule stalk mount, the impact of which has remained a contentious question. In this paper, we describe the results from an experiment on the OMEGA laser with intentional offsets at varying angles to the capsule stalk mount, which clearly demonstrates the impact of the stalk mount on implosion dynamics. The angle between stalk and offset is found to significantly impact observables. Specifically, a larger directional flow is observed in neutron spectrum measurements when the offset is toward rather than away from the stalk, while an offset at 42° to the stalk gives minimal directional flow but still generates a large flow field in the implosion. No significant directional flow is seen due to stalk only. Time-integrated x-ray images support these flow observations. A trend is also seen in implosion yield, with lower yield obtained for offsets with a smaller angle than with a larger angle toward the stalk. Radiation hydrodynamic simulations using 2D DRACO and 2D/3D Chimera not including the stalk mount and using 2D xRAGE including the stalk mount are brought to bear on the data. The yield trend, the minimal directional flow with stalk only, and the larger flow enhancement observed with the offset toward the stalk are all reproduced in the xRAGE simulations. The results strongly indicate that the stalk impact must be considered and mitigated to achieve high-performing implosions.

中文翻译：

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茎对直驱惯性约束聚变内爆的影响

低模不对称性已成为实现高性能惯性约束聚变 (ICF) 内爆的主要挑战之一。在直接驱动 ICF 中，这种不对称性的一个重要潜在种子是胶囊柄支架，其影响仍然是一个有争议的问题。在本文中，我们描述了 OMEGA 激光器的实验结果，在不同角度有意偏移到胶囊杆支架，这清楚地证明了杆支架对内爆动力学的影响。发现茎和偏移之间的角度会显着影响可观察值。具体而言，当偏移量朝向而不是远离茎时，在中子谱测量中观察到更大的定向流，虽然与茎成 42° 的偏移量会产生最小的定向流，但仍会在内爆中产生大的流场。仅由于茎，没有看到明显的定向流。时间积分 X 射线图像支持这些流动观察。内爆产量也有趋势，与朝向茎的较大角度相比，较小角度的偏移获得的产量较低。使用 2D DRACO 和 2D/3D Chimera（不包括杆支架）和使用 2D xRAGE（包括杆支架）进行的辐射流体动力学模拟对数据产生影响。在 xRAGE 模拟中重现了产量趋势、仅具有茎的最小定向流以及在向茎偏移的情况下观察到的较大流动增强。