2009 Annual Report

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The fiscal year ending September 2009 (FY2009) concluded the second 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 laboratory basic science research; laser, optical materials, and advanced technology development; operation of OMEGA and OMEGA EP for the National Laser Users’ Facility (NLUF), and other external users; and programs aimed at the education of high school, undergraduate, and graduate students during the year.

The science 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 on the National Ignition Facility (NIF). This program includes the full use of the OMEGA 60-beam UV laser as well as the OMEGA EP high-energy, short-pulse laser system. During FY09, OMEGA EP was operated on target at an energy level of 2.1 kJ at 10 to 12 ps, making the laser the world’s highest-energy short-pulse 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 that are being 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 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 FY09, LLE, in collaboration with Lawrence Livermore National Laboratory (LLNL) and Sandia National Laboratories (SNL), demonstrated a key shock-timing technique for ignition targets at the NIF. This technique is critical for optimizing the drive profiles for high-performance ICF capsules, which are compressed by multiple precisely timed shock waves. These results provide confidence that shock velocity and timing can be measured in NIF ignition targets, thereby optimizing these critical parameters.

Progress was made on high-density implosions of direct-drive cryogenic capsules. Ignition-relevant areal densities of ~200 mg/cm² in cryogenic D₂ implosions with peak laser-drive intensities of ~5 x 10¹⁴ W/cm² were previously reported. The laser intensity is being increased to ~10¹⁵ W/cm² to demonstrate ignition-relevant implosion velocities of 3 to 4 x 10⁷ cm/s, providing an understanding of the relevant target physics.

The report includes an article on integrated simulations of implosion, electron transport, and heating for direct-drive fast-ignition targets. A thorough understanding of future integrated fast-ignition experiments combining compression and heating for high-density thermonuclear fuel requires hybrid (fluid + particle) simulations of the implosion and ignition process. Different spatial and temporal scales need to be resolved to model the entire fast-ignition experiment. The 2-D axisymmetric hydrocode DRACO and the 2-D/3-D hybrid-PIC code LSP have been integrated to simulate the implosion and heating of direct-drive, fast-ignition targets. These results confirm an increase in the electron-divergence angle with the laser intensity in the current experiments. The self-generated resistive magnetic field is found to collimate the hot-electron beam and increase the coupling efficiency of hot electrons with the target. Resistive filamentation of the hot-electron beam is also observed.

The annual report includes articles on advanced technology development at LLE. One such report co-authored by scientists from LLE and the UR’s Department of Mechanical Engineering discusses in-situ, simultaneous measurements of both drag and normal forces in magnetorheological optical finishing (MRF) using a spot-taking machine (STM) as a test bed to take MRF spots on stationary optical parts.

Under the governance plan implemented in FY08 to formalize the scheduling of the Omega Laser Facility as a National Nuclear Security Agency (NNSA) facility, OMEGA shots are allocated by campaign. The majority of the FY09 target shots (~56.7%) 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 on both the OMEGA and OMEGA EP Laser Systems. Twenty percent (20%) of the FY09 shots were allocated to high-energy-density stewardship experiments (HEDSE) from LLNL and LANL. Under this governance plan, 25% of the facility shots were allocated to basic science experiments. Roughly half of these were dedicated to university basic science, i.e., the National Laser Users’ Facility (NLUF) Program, and the remaining shots were allotted to the Laboratory Basic Science (LBS) Program, comprising peer-reviewed basic science experiments conducted by the national laboratories and LLE/FSC. The Omega Facility is also being used for experiments by teams from the Commissariat à l’Énergie Atomique (CEA) of France and the Atomic Weapons Establishment (AWE) of the United Kingdom. These programs are conducted on the basis of special agreements put in place by DOE/NNSA and the participating institutions.

The external users during this year included a record 11 collaborative teams that participated in the NLUF Program. Ten teams from LLNL, LANL, and LLE were allotted shots under the LBS Program. Integrated experimental teams from the national laboratories and LLE conducted 851 shots for the NIC, and investigators from LLNL, LANL, and LLE conducted over 232 shots for the HEDSE programs. A total of 56 shots were conducted by scientists from CEA and 35 shots were carried out by scientists from AWE.

During FY09 the Omega Laser Facility conducted 1153 target shots on OMEGA and 349 target shots on OMEGA EP for a total of 1502 combined target shots. Twenty-four DT and 24 D₂ low-adiabat spherical cryogenic target implosions were conducted on OMEGA. Triple-picket pulse-shaping developments highlighted the ongoing development of direct-drive cryogenic implosion capability. A planar cryogenic platform to measure spherical shock timing was validated and used extensively to support spherical cryogenic experiments. A total of 31 planar cryogenic target shots were taken. The OMEGA Availability and Experimental Effectiveness averages for FY09 were 93% and 96%, respectively.

OMEGA EP was operated extensively in FY09 for a variety of internal and external users. A total of 298 short-pulse IR target shots were conducted. Of these, 212 target shots were taken on the OMEGA EP target chamber and 86 joint target shots were taken on the OMEGA target chamber. Beams 1 and 2 were activated to target in the UV, and the first four-beam UV target shots were conducted. A total of 76 OMEGA EP target shots included UV beams. OMEGA EP averaged 4.7 target shots per day with Availability and Experimental Effectiveness averages for FY09 of 90% and 97%, respectively.

As the only major university participant in the National ICF Program, education continues to be an important mission for the Laboratory. Laboratory education programs span the range of high school to graduate education.

During the summer of 2009, 16 students from Rochester-area high schools participated in the Laboratory for Laser Energetics’ Summer High School Research Program. The goal of this program is to excite a group of high school students about careers in the areas of science and technology by exposing them to research in a state-of-the-art environment.

Approximately 60 undergraduate students participated in work or research projects at LLE this past year. Student projects include operational maintenance of the Omega Laser Facility; work in laser development, materials, and optical-thin-film–coating laboratories; computer programming; image processing; and diagnostics development. This is a unique opportunity for students, many of whom will go on to pursue a higher degree in the area in which they gained experience at the Laboratory.

Graduate students are using the Omega Facility as well as other LLE facilities for fusion and high-energy-density physics research and technology development activities. Twenty-five faculty from the five University academic departments collaborate with LLE scientists and engineers. Presently, 88 graduate students are involved in research projects at LLE, and LLE directly sponsors 37 students pursuing Ph.D. degrees via the NNSA-supported Frank Horton Fellowship Program in Laser Energetics. 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 fabrication technology, and target fabrication.

In addition, LLE directly funds research programs within PSFC–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.