Three-Dimensional Hot-Spot Reconstruction from Cryogenic Deuterium-Tritium Polar-Direct-Drive Implosions on OMEGA*

The impact of laser drive asymmetry on the hot-spot shape in the polar-direct drive (PDD) beam-pointing scheme has been studied on OMEGA. The capsules were illuminated with varying ring-energy partitions while keeping the total laser energy constant, and a significant mode-2 asymmetry in the hot-spot emission was observed. Causal effects from the laser drive show the expected change in hot-spot shape from prolate to oblate. A quantitative analysis of the hot-spot shape asymmetry was performed using a 3-D elliptical model of the hot-spot emission projected into multiple quasi-orthogonal lines of sight of the x-ray imagers and compared to the measurements. The temporal evolution of the hot-spot shape will be investigated. Proof-of-principle simulations with the hydrodynamic code DEC3D [K. M. Woo et al., Phys. Plasmas 25, 052704 (2018)] assuming a mode-2 perturbation were used to demonstrate the above 3-D reconstruction procedure using synthetic x-ray images. Higher-fidelity 3-D reconstructions of the hot spot will be performed using a spherical-harmonic decomposition algorithm.