Mitigation of Low-Mode Perturbations with 3-D Hot-Spot X-Ray Emission Tomography on Laser-Direct-Drive Implosions on OMEGA*

A demonstration of 3-D hot-spot x-ray emission tomography on OMEGA was conducted to diagnose and mitigate low-mode perturbations on spherically symmetric laser-direct-drive inertial confinement fusion implosions [K. Churnetski et al., Rev. Sci. Instrum. 93, 093530 (2022), K. M. Woo et al., Phys. Plasmas 29, 082705 (2022)]. This 3-D hot-spot x-ray emission tomography technique was initially developed on polar-direct-drive implosions [K. Churnetski et al., Rev. Sci. Instrum. 93, 093530 (2022)]. Mode-1 and -2 asymmetries were separately seeded in the initial targets by either offsetting spherically symmetric targets from target chamber center (mode 1) or by varying the mass distribution in the plastic targets to create a mode-2 asymmetry. The on-target spatial distribution of laser energy was iteratively varied to mitigate the hot-spot shape asymmetries. A mapping relation of hot-spot shape asymmetries as a function of laser-energy corrections will be presented. The upper limit of the spherical harmonics modes that can be resolved with the current x-ray diagnostic capabilities and with improved time-resolved diagnostics will be discussed. This limit was identified using single-mode perturbation simulations produced by the radiation-hydrodynamic code DEC3D [K. M. Woo et al., Phys. Plasmas 25, 052704 (2018)].