Advances in Direct-Drive Fusion, High-Energy-Density Physics, and Laser Technologies at the Laboratory for Laser Energetics

Abstract

The last five years have seen remarkable advances in four key missions of the Laboratory for Laser Energetics (LLE): fusion, high-energy-density physics (HEDP), laser technology, and education. By integrating theory and computation, statistical modeling, three-dimensional diagnostic methods, and improved target fabrication and diagnostics, directly driven implosions on the 30-kJ Omega Laser Facility have produced record neutron yields (>3e14) and hot spot pressures in deuterium-tritium implosions(80 Gbar). The latter indicating that the hydrodynamically scaled generalized Lawson criteria is approaching the required values for alpha heating and ignition at the few megajoules of drive energy. The recent National Ignition Facility results indicate that hotspot ignition is feasible while the Omega program is showing the promise of coupling significant energy to capsules. A key part of the enhanced coupling comes from a deeper understanding of laser-plasma interactions and instabilities. The community is moving to a more predictive capability for these physics topics and generating fundamental measurements (i.e., directly measuring the electron distribution functions). A key conclusion of this research is that future laser drivers will require increased bandwidth, >3% versus the <1% on Omega, to control cross-beam energy transfer and other instabilities. At LLE we are developing a fourth-generation laser prototype, FLUX, to demonstrate that enhanced bandwidth does provide the required control. FLUX is based on a series of laser development activities on our MTW laser and target physics test bed. The OMEGA Extended Performance (EP) facility also continues to advance our understanding many of our laser-plasma interaction experiments were conducted on OMEGA EP plus OMEGA EP is a workhorse for our HEDP research. Recent experiments have advanced an understanding of materials and pressures and densities relevant to planets and stars. For example, experiments on OMEGA EP have measured melt curves of magnesium oxide at pressures up to 1 TPa. Other experiments have measured the Hugoniot of silicon up to 2 TPa and deuterium to 1 TPa. These latter measurements are also relevant to the formation of stars and for inertial confinement fusion (ICF). They also represent the achievement of pressures 50 times greater than those achieved in the pioneering gas gun work of Nellis in 1995. Achievements in ICF and HEDP are enabled through experiments in diagnostics, fundamental understanding of laser-plasma interactions and precision control, and technology advances in fundamental laser technology. OMEGA and OMEGA EP have continued to improve laser operations and performance. In addition, smaller scale lasers such as MTW have enabled the production of 7 J, 20 femtosecond pulses to define a path to 10 to 100 PW lasers, to study the physics discussed in the Bright Light Initiative. In this talk, we will discuss progress in the LLE program and highlight pioneering achievements, many of which are led by our excellent graduate students.