Speaker
Description
Recent progress in direct-drive inertial confinement fusion has considerably improved the prospects for achieving thermonuclear ignition with direct illumination. When hydrodynamically scaled to laser energies typical of the National Ignition Facility, recent OMEGA implosions are expected to produce over 800 kJ of fusion yield and 80% of the Lawson triple product required for ignition at 2 MJ of symmetric illumination. Those implosions have benefited from a significant increase in implosion velocity obtained through larger-diameter targets, new laser pulse shapes, and the use of silicon doping to increase laser-energy absorption. A new statistical approach used in designing OMEGA targets has demonstrated a considerable predictive capability, thereby enabling the design of targets with improved performance, leading to recent record neutron yields up to ~3 1014 or about 1 kJ of fusion yield. Systematic experiments such as scans of smoothing by spectral dispersion bandwidth, age of the DT fill, and beam-over-target size are used to identify mechanisms of performance degradation and implosion optimization. Pre shot predictions of the fuel areal density are complicated by low-mode nonuniformities and validating new designs require many shots to acquire statistically meaningful measurements of the average areal density. Ongoing experiments on OMEGA are designed to improve the target convergence and the fuel areal density to achieve the highest value of the Lawson parameter. Implications of these results for direct-drive ignition using multi-megajoule lasers and fourth generation broadband lasers for suppression of laser–plasma instabilities are discussed. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0003856, the University of Rochester, and the New York State Energy Research and Development Authority.
