2008 Annual Report

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The fiscal year ending September 2008 (FY08) concluded the first year of the third five-year renewal of Cooperative Agreement DE-FC52-08NA28302 with the U.S. Department of Energy (DOE). This annual report summarizes progress in inertial fusion research at the Laboratory for Laser Energetics (LLE) during the past fiscal year. It also reports on LLE’s progress on laser, optical materials, and advanced technology development; the completion of the OMEGA EP High-Energy, Petawatt-Class Laser System on time and on budget; operation of OMEGA for the National Laser Users’ Facility (NLUF) and other external users; and programs focusing on the education of high school, undergraduate, and graduate students during the year.

The research program at the University of Rochester’s Laboratory for Laser Energetics (LLE) focuses on inertial confinement fusion (ICF) research supporting the goal of achieving ignition at the National Ignition Facility (NIF). This program includes the full use of the Omega EP Laser System. Within the National Ignition Campaign (NIC), LLE is the lead laboratory for the validation of the performance of cryogenic target implosions, essential to all forms of ICF ignition. LLE has taken responsibility for a number of critical elements within the Integrated Experimental Teams (IET’s) supporting the demonstration of indirect-drive ignition on the NIF and is the lead laboratory for the validation of the polar-drive approach to ignition on the NIF. LLE is also developing, testing, and building a number of diagnostics to be deployed on the NIF for the NIC.

During this past year, progress in the inertial fusion research program was made in three principal areas: NIC experiments; development of diagnostics for experiments on OMEGA, OMEGA EP, and the National Ignition Facility (NIF); and theoretical analysis and design efforts aimed at improving direct-drive-ignition capsule designs and advanced ignition concepts such as fast ignition and shock ignition.

In FY08, LLE, in collaboration with the Plasma Science Fusion Center MIT, RSI Corporation, Naval Research Laboratory (NRL), and the Nuclear Research Center Negev, continued investigations of ignition-scaled cryogenic capsule implosions. A series of experiments were carried out on OMEGA to study the physics of low-adiabat, high-compression cryogenic capsule assembly. High-areal-density (with ?R > 0.2 g/cm²) cryogenic-fuel assembly is reported on OMEGA designs, where the shock timing was optimized using the nonlocal treatment of the heat conduction and the suprathermal electron preheat by the two-plasmon-decay instability was mitigated.

The effort to demonstrate ignition-quality cryogenic fuel layers achieved the milestone of routinely providing cryogenic DT capsules that meet the 1.0- μm (rms) OMEGA ice-surface-quality specification. The best D₂ layers achieved so far (rms roughness of 1.1 μm) are approaching the quality achieved in DT targets. Efforts to improve the consistency of this process are reported along with investigations that support the National Ignition Campaign’s study of issues relevant to ignition-scale indirect-drive and direct-drive cryogenic targets.

This report also includes articles on advanced-technology development projects at LLE, including the development of an improved laser-speckle-smoothing scheme that augments the current NIF 1-D SSD system by using multiple-FM modulators (MultiFM 1-D SSD); the development of a single-shot, high-dynamic-range cross-correlator to characterize picosecond laser pulses; the development of a novel focal-spot diagnostic for OMEGA EP; and systematic studies to improve the laser-damage resistance of multilayer high-reflector coatings for use at 351 nm on the Omega EP Laser System.

The OMEGA EP project was completed in April 2008–on time and on budget. The formal Critical Decision 4 (CD-4) milestone was approved by the NNSA Acquisition Executive on 6 May 2008. OMEGA EP accomplished all project completion criteria, demonstrating short- and long-pulse capability. A CD-4 Project Completion review was conducted on-site by NNSA on 23-24 April to validate project completion.

During FY08, a governance plan was implemented to formalize the scheduling of the Omega Laser Facility as an NNSA User Facility. Under this plan, OMEGA shots are allocated by campaign. The majority of the FY08 target shots were allocated to the National Ignition Campaign (NIC), and integrated experimental teams from LLNL, LANL, SNL, and LLE conducted a variety of NIC-related experiments primarily at the Omega Facility. Shots were also allocated in FY08 to the high-energy-density (HED) physics programs from LLNL and LANL.

Under the governance plan 25% of the facility shots are allocated to Basic Science experiments. Roughly half of these are dedicated to University Basic Science under the National Laser Users’ Facility Program and the remaining shots are allotted to Laboratory Basic Science, comprising peer-reviewed Basic Science experiments conducted by the national laboratories and LLE/FSC.

In total, nearly 49% of the 1254 Omega Facility target shots were dedicated to external users including the NLUF programs, LLNL, LANL, SNL, CEA, and AWE.

As the only major university participant in the National ICF Program, education continues to be an important mission for the Laboratory. Twenty-five University faculty from five departments collaborate with LLE’s scientists and engineers. Presently, 87 graduate students are involved in research projects at LLE, and LLE directly sponsors 39 students pursuing Ph.D. degrees. Their research includes theoretical and experimental plasma physics, high-energy-density physics, x-ray and atomic physics, nuclear fusion, ultrafast optoelectronics, high-power-laser development and applications, nonlinear optics, optical materials and optical fabrications technology, and target fabrication. Approximately 66 undergraduate students participated in work or research projects at LLE this past year.

LLE also directly funds research programs within the Plasma Science and Fusion Center–MIT, the State University of New York (SUNY) at Geneseo, the University of Nevada, Reno, and the University of Wisconsin. These programs involve a total of approximately 16 graduate students, 27 undergraduate students, and 7 faculty members.