LLE Review 104

Review 104


This volume of the LLE Review, covering July through September 2005, features a report on backlit optical shadowgraphy, the primary diagnostic for D2 ice layer characterization of cryogenic targets for the OMEGA Laser System. Measurement of the position of the most prominent rings, caused by the reflection and refraction of light in the ice layer, in conjunction with model predictions allows constructions of a 3-D ice layer representation suitable for implosion modeling.

Another highlight is a description of velocity interferometry and optical self emission measurements from shock waves in polystyrene targets. The velocity histories, coalescence times, and transit times are unambiguously observed and are in good agreement with 1-D code predictions. The timing of multiple shock waves is crucial to the performance of inertial confinement fusion ignition targets.

Additional highlights of research presented in this issue include the following:

  • Designs set to achieve direct-drive ignition on the NIF at 1 MJ using the x-ray-drive beam configuration are examined. This approach, known as polar direct drive (PDD), achieves the required irradiation uniformity by repointing some of the beams toward the target equator.
  • Simulations of integrated fast-ignition experiments on the combined OMEGA/OMEGA EP Laser Systems with the multidimensional hydrodynamic code DRACO are presented. An OMEGA cryogenic DT target has been simulated in 2-D with and without nonuniformities. The neutron yield is predicted to be in excess of 1015 (compared to ~1014 without an ignitor beam).
  • The development of a proton emission imaging system that has been used to measure the nuclear burn regions in the cores of inertial confinement fusion implosions is described. The imaging technique relies on the penumbral imaging of 14.7-MeV D3He fusion protons.
  • A hot, Te ~ 2- to 3-keV surface plasma in the interaction of a 0.7-ps petawatt laser beam with solid copper-foil targets at intensities >1020 W/cm2 has been observed. These temperatures were inferred from Cu, Heα, and Lyα emission lines. Such lines have not previously been observed in interactions with ultrafast laser pulses.
  • A summary of LLE's Summer High School Research Program.
  • The FY05 Laser Facility Report.
  • The National Laser Users' Facility and External Users' Programs summary.

Table of Contents