Hydro-equivalent extrapolation of high performance direct-drive cryogenic implosion experiments on OMEGA

Energy constraints on OMEGA limit the ability to conduct inertial confinement fusion (ICF) experiments with sufficient alpha heating to achieve ignition. To assess the quality of OMEGA cryogenic implosions, a process known as ‘hydro-equivalent extrapolation’ is used to determine proximity to ignition by keeping intrinsic quantities such as pressure fixed, while simply increasing the size of the hotspot. Using the 1D hydrodynamic code LILAC, we recreate high-performing implosions and hydro-equivalently scale them by 4.23x. Assuming the energy required to achieve this increase in size while keeping pressure fixed goes like R³ , this corresponds to a required driver energy of 2.15 MJ. This scaling helps quantify yield amplification due to alpha heating and estimate the extrapolated Lawson parameter (𝜒) due to the hotspot conditions of the high performing OMEGA experiments. We show that advances in implosion design, such as the introduction of subcooling, have enabled experiments to approach near hydro-equivalent ignition conditions. Modifications to the hydrodynamic code ASTER are in progress to assess the impact of 3D perturbations on alpha heating dynamics in these conditions.