Experimental Demonstration of 3D Hot-spot Shape Symmetry Control in Laser Direct-Drive Inertial Confinement Fusion Implosions*

The OMEGA laser facility has demonstrated the feasibility of achieving symmetric implosions through corrective on-target laser energy adjustments. The symmetry control experiment applied a real-time (between shots) machine-learning based 3D reconstruction of hot-spot plasma emissivity from multi-angle x-ray imaging. This enabled quantification of the magnitude and orientation of low-mode (L = 1-2) asymmetries, which were separately seeded by a 40-μm target offset and a shimmed shell with 3-μm thickness variation along the polar axis. The large L = 2 prolate asymmetry was successfully mitigated, while the mitigation of L = 1 asymmetry was also observed. The methodology of controlling 3D low-mode hot-spot shape asymmetries through on-target laser energy adjustments and 3D reconstruction is being integrated with an artificial intelligence system, aiming to achieve symmetric and high-performance implosions. Three major frameworks are developed, including an evolutionary optimization that generates optimal laser pulse shapes achieving high measured yields of 1.82E14, a convolutional neural network model for fast (between shots) 3D tomography of hot-spot and shell structures, and a quantum-inspired data analysis model identifying correlations between input non-uniformities and measured hot-spot flow asymmetries.