2006 Annual Report

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The fiscal year ending in September 2006 concluded the fourth year of the second five-year renewal of Cooperative Agreement DE-FC52-92F19460 with the U.S. Department of Energy. This report summarizes the FY06 work on laser-fusion research at the Laboratory for Laser Energetics (LLE); LLE’s progress on laser, optical materials, and advanced technology development; work on the OMEGA Extended Performance (EP) laser project, operation of the National Laser Users’ Facility (NLUF); and the education programs for high school, undergraduate, and graduate students conducted during the past year.

The laser-fusion research program at LLE is focused on Campaign-10 inertial confinement fusion (ICF) ignition and experimental support technology, operation of facilities (OMEGA), and the construction of OMEGA EP, a high-energy petawatt laser system. LLE is the lead laboratory for research in the direct-drive approach to ICF ignition and is taking a lead role in some indirect-drive tasks within the National Ignition Campaign. Progress in the laser-fusion-research program during this past year was made in three principal areas: OMEGA direct-drive experiments and targets; development of diagnostics for experiments on OMEGA, OMEGA EP, and the National Ignition Facility (NIF); and theoretical analysis and design efforts aimed at improved direct-drive-ignition capsule design.

Virtually all ignition target designs for the NIF are based on a spherical low-Z ablator containing a solid, cryogenic-fuel layer of deuterium and tritium. Techniques developed at LLE have produced targets with an inner D₂ or DT ice surface that meets the surface-smoothness requirements for ignition (=1-μm rms in all modes). The first of a series of direct-drive, ignition-scaled cryogenic capsules containing tritium were initiated in 2006. A DOE milestone was achieved in March 2006 by imploding two β-layered capsules containing tritium. A high-yield, direct-drive, ignition-scaled 50:50 DT cryogenic implosion was carried out in June 2006—the first time such a target was imploded in an ICF facility.

Other important aspects of the inertial fusion research discussed in the report include: target design and analysis for OMEGA experiments and the NIF ignition campaign; target-diagnostic development for OMEGA EP and the NIF; and the development of the polar-direct-drive concept that would allow the NIF indirect-drive beam configuration to be used for direct-drive experiments leading to ignition on the NIF.

This report also includes articles on advanced-technology-development projects under way at LLE, including design and analysis of binary beam shapers for high-power lasers; high-contrast, plasma-electrode Pockels cell (PEPC) for OMEGA EP; high-gain, polarization-preserving, Yb-doped fiber amplifier for low-duty-cycle pulse amplification; the development of fiber-coupled, single-photon detectors based on NbN superconducting nanostructures for practical quantum cryptography and photon-correlation studies; the design and synthesis of a transition metal-dithiolene near-IR dye; and the analysis of surface features of tungsten carbide composites processed by bound-abrasive microgrinding and magnetorheological finishing (MRF).

The OMEGA EP project continued on a fast-track schedule to complete the four-beam system. The full OMEGA EP “total estimated” cost is $89 million, of which $87 million was appropriated through FY06. The project is on track to begin operations in the spring of 2008. During FY06 the OMEGA Facility conducted 1394 target experiment shots; nearly half of these were for external users of the system. During this period, the system availability and experimental effectiveness averaged 93.3% and 95.3%, respectively.

As the only major university participant in the National ICF Program, education continues to be an important mission of LLE. One hundred seventy-seven University of Rochester students have earned Ph.D. degrees at LLE since its founding. There are currently 93 graduate students doing research at the Laboratory and approximately 45 undergraduate students are employed by LLE during the academic year and the summer. During the summer, up to 15 high- school students participate in a summer research program.