High-Pressure Laser-Fusion Compression Results

Abstract

There are two principal approaches to inertial confinement fusion (ICF): direct and indirect drive. In the indirect or approach to fusion, pursued primarily at the national weapons laboratories at Los Alamos and Livermore, the driver-beam energy is absorbed and converted to x rays by a radiation case made of a high-atomic-weight element, the x rays are then used to drive the target implosion. In the alternative direct-drive approach, a short-wavelength high-intensity laser pulse directly illuminates a bare, spherical target. The implosion of capsules by direct laser drive may be more efficient than indirect drive. The University of Rochester's Laboratory for Laser Energetics (LLE) is the primary focus in the United States used to investigate directly driven spherical target experiments. The LLE research program in ICF has two principal objectives: (1) to demonstrate the scientific feasibility of the direct-drive concept for inertial fusion, and (2) to investigate the fundamental physics of the interaction of intense laser radiation with matter. The first of these objectives is addressed by a program aimed at the demonstration of high compression (peak DT densities in the range of 10-20 g/cm 3 ) with short-wavelength (0.35-μm) laser radiation and direct-drive targets. The primary elements of this program include (a) development and implementation of high-density diagnostic systems on the OMEGA facility; (b) theoretical simulations of laser-driven target implosions using one-dimensional and two-dimensional hydrocodes; (c) the achievement of a high degree of drive uniformity (±5%) on the 24-beam OMEGA laser; and (d) the development and implementation of solid and liquid fuel layer targets. The second objective (laser-matter interaction physics) is addressed by an experimental and theoretical effort including (a) laser-target coupling studies; (b) studies of parametric instabilities occurring in the coronal plasma; (c) investigations of electron-thermal energy transport; and (d) research on the hydrodynamic behavior of ablatively driven targets , including the study of Rayleigh-Taylor instabilities. Even though the specific research topics covered under this part of the program are motivated by the primary mission, the demonstration of the feasibility of direct-drive inertial fusion, the fundamental laser-matter interaction physics issues are also important to hohlraum driven targets.