2004 Annual Report
The fiscal year ending in September 2004 concluded the second year of the second five-year renewal of cooperative agreement DE-FC03-92SF19460 with the U.S. Department of Energy (DOE). This report summarizes research at the Laboratory for Laser Energetics (LLE) conducted during the year, operation of the National Laser Users’ Facility (NLUF), a status report of the new OMEGA Extended Performance (EP) laser project, and programs concerning the education of high school, undergraduate, and graduate students during the year.
The prime thrust of LLE’s ICF research is the validation of capsule designs that are hydrodynamically equivalent to the baseline cryogenic direct-drive ignition design for the National Ignition Facility (NIF). In FY04, layered and characterized cryogenic deuterium capsules were imploded using both high adiabat (α ~ 25) and low-adiabat (α ~ 5) shaped pulses. These experiments measured the sensitivity of the direct-drive implosion performance to parameters such as the inner-ice-surface roughness, the adiabat of the fuel during the implosion, the positioning precision of the capsules, and the laser power balance. Direct measurements of the compessed cryogenic deuterium capsule core temperature-density profiles were carried out using the measured primary deuterium–deuterium (DD) and secondary deuterium–tritium (DT) neutron yields, neutron-averaged ion temperature, and x-ray images at peak neutron production. For low-adiabat pulse shapes, the electron pressure, areal density of the burn region, and areal density of the triton stopping region were found to be ~2.7 Gbar, ~10 mg/cm², and ~23 mg/cm², respectively.
The report also contains accounts of the investigation of target areal-density asymmetries, measurements of the imprint efficiency on planar targets, multidimensional simulations of plastic shell implosions (using the code DRACO), the development of a variety of plasma diagnostic techniques, and a comprehensive overview of the methodology and issues involved in the preparation of deuterium ice layers in OMEGA targets.
The OMEGA EP (Extended Performance) project completed the majority of the preliminary design phase and moved into the project execution phase during FY04. Starting in FY03 with $13 million in funding, the project continued with $20 million in FY04 funding. Concomitantly, NNSA project authorizations in FY04 included the approval of the Performance Baseline (Critical Decision 2) and approval to Start Construction (Critical Decision 3). Many acquisitions were started in FY04, and some of the materials will be stored until the building is completed in the second quarter of FY05. The building that will house OMEGA EP was under construction throughout FY04 and was funded entirely by the University of Rochester. The construction of exterior mansonry, windows, loading docks, curbing, and grading were all completed in FY04. Interior work highlighted in FY04 include the the single-pour, 2000-cubic-yard concrete slab to support the laser, installation of the clean room equipment, installation and certification of the two overhead 10-ton cranes, and the installation of laser infrastructure such as the electrical subsystem, cooling water, and vacuum piping.
Significant progress is also reported on the optical technology areas that are critical for the success of the OMEGA EP project: the development of the CPA laser source, the manufacturing, assembly and initial testing of the large-aperture Pockels cell (PEPC), the testing of the prototype 40-cm aperture amplifier, the implementation of wavefront sensing and deformable mirror control hardware and software, the demonstration of multilayer dielectric diffraction gratings with a damage threshold greater than that required for 2 kJ per beam operation, and the demonstration of a subscale tiled grating compressor and closed-looped control system.
FY04 was a record year for external user experiments on OMEGA with a total of 802 target shots dedicated to the NLUF program and National laboratories (LLNL, LANL, SNL, NRL) as well as CEA and AWE users. The report contains a summary account of the eclectic external user programs carried out on OMEGA during FY04.
Finally, this report includes a summary of the LLE education programs in FY04. LLE is the only major university participant in the National ICF Program, and education is an important mission of the Laboratory. In FY04, there were 63 University of Rochester graduate students pursuing degrees in the Laboratory. In addition, 66 University undergraduates participated in work or research at the LLE. There were also 16 high school students participating in the annual Summer High School Student Research Program.