Progress in modelling ignition implosion experiments on the National Ignition Facility

Abstract

The recently completed National Ignition Campaign on the National Ignition Facility showed significant discrepancies between 2-D simulations predictions of implosion performance and experimentally measured performance, particularly in thermonuclear yield. This discrepancy between simulation and observation persisted despite concerted efforts to include all of the known sources of implosion degradation within a reasonable 2-D simulation model, e.g., using measured surface imperfections and radiation drives adjusted to reproduce observed implosion trajectories. Since this simulation study was undertaken, more recent experiments have brought to light several effects that can significantly impact implosion performance, in particular large inflight long-wavelength shell asymmetries and larger than expected perturbations seeded by the capsule support tent. These effects are now being included in the simulation model and show improved agreement with observation. In addition, full-capsule 3-D simulations with resolution adequate to model the dominant unstable hydrodynamic modes are being run and show further improvements in agreement with experiment.