Impacts of Hot-Spot Flows from Drive Asymmetry on Implosion Performance at the National Ignition Facility (NIF)

Asymmetries in laser indirect drive during inertial confinement fusion dramatically reduce performance, due to implosion energy being transferred into residual plasma motion instead of hot spot compression and heating. A dedicated set of NIF experiments characterized these effects, using a simplified platform and single-variable changes to isolate physics and diagnostic signatures of low-mode asymmetries. Results provided clear measurements of performance degradation from a Legendre l = 1 asymmetry. [1] These results are now used to interpret more complex, ignition-relevant DT-ice layer implosions. Experimental signatures are directly applicable, and strong flows within the hot-spot with corresponding large variances, often correlate with large apparent-T_ion asymmetries. Apparent ΔT_ion measured at different locations around the plasma can be used to estimate hot spot residual kinetic energy (RKE). 2D simulations of simplified and complex platforms show qualitative agreement but both overpredict measured apparent ΔT_ion. Observation of time-resolved flows within the hot spot during an implosion are directly compared to flow-fields from 2D HYDRA simulations. Higher-order flows are quantified and shown to directly contribute to RKE and performance degradation.