Progress toward hydro-equivalent ignition in OMEGA directdrive DT-layered implosions

Considerable progress has been made in DT-layered implosion experiments on the OMEGA Laser System, bringing the possibility of thermonuclear ignition in direct-drive configurations with megajoule-class lasers closer to reality. Doing so has required navigating the balance between improved 1D performance and multidimensional stability. Using statistical modeling based on over 350 cryogenic implosions to identify various degradation mechanisms, and combined with multidimensional simulations and experimental techniques such as target offsets to combat residual flows, core conditions have repeatably been achieved that extrapolate to the burning-plasma state when scaled to 2.15MJ of symmetric laser illumination. Using high implosion velocities (> 450km/s) and moderately high adiabats (∼ 5), these experiments produced record-high scaled Lawson parameters in direct drive equal to 89 ± 2% of that required for ignition with expected yields of up to 1.5 ± 0.2 MJ. To improve these results still further, focused-physics studies are performed to improve physics understanding and identify routes to even greater performance. Recent studies include investigations into the impact of mounting features, laser imprint, reduced fuel temperatures, and greater on-target intensities through subscale experiments. This manuscript gives a summary of the cryogenic direct-drive program on the OMEGA laser, including routes taken to achieve the current best performance, the status of recent focused-physics investigations, and future designs—such as target solutions to laser imprint and reducing vapor density to increase convergence—that are expected to soon produce hydro-equivalent ignition on OMEGA.