This volume of the LLE Review, covering July–September 2016, features “Hugoniot and Release Measurements in Diamond Shocked Up to 26 Mbar.” This article reports on measurements of the equation of state of carbon at extreme pressures. Knowledge of the high-pressure shock and release responses of diamond are needed to accurately model an inertial confinement fusion (ICF) implosion and design ignition targets. The article presents Hugoniot and release data for both single-crystal diamond and high-density carbon (HDC). Hugoniot results indicate that HDC, which is ultra-nanocrystalline and ~4% less dense than single-crystal diamond, has a stiffer response than single-crystal diamond.
Additional highlights of research presented in this issue include the following:
- Laser direct-drive designs require reaching central stagnation pressures in the hot spot of larger than 100 Gbar. The current experiments on OMEGA have achieved inferred peak pressures of 56 Gbar. Extensive analysis of the cryogenic target experiments and two- and three-dimensional simulations are reported that suggest that power balance, target offset, target quality, and reduced laser energy coupling caused by cross-beam energy transfer are the main limiting factors in target performance. All of this must be improved in order to reach the goal of demonstrating hydrodynamic equivalence on OMEGA.
- The first complete set of measurements of a laser-plasma optical system’s refractive index, as seen by an independent probe laser beam, as a function of the relative wavelength shift between the two laser beams is reported. Both the imaginary and real refractive index components are found to be in good agreement with linear theory using plasma parameters measured by optical Thomson scattering and interferometry. The data include the first demonstration of a laser-plasma polarizer with 85% to 87% extinction for the particular laser and plasma parameters used in this experiment.
- An x-ray detection system has been developed and commissioned at the Laboratory for Laser Energetics with the intent of nondestructively extrapolating the pressure of tritium-filled targets from their measured activity.
- R. Mancini reports on the Eighth Omega Laser Facility Users Group Workshop
- This volume concludes with a summary of LLE’s Summer High School Research Program, the FY16 Laser Facility Report, and the National Laser Users’ Facility and External Users’ Programs.