Highlighting the History of the LLEOctober, 2010
Between 1971 and 1975, the first four-beam LLE system, Delta, was built and operated. Delta was an ~1-kJ Nd:glass laser used to investigate the interaction of high-power laser radiation and plasma with particular emphasis on laser fusion.
A key year in the history of LLE was 1975. The vision of Lubin’s team—to build and operate a very large, 24-beam IR laser facility to be called OMEGA—would cost tens of millions of dollars. The invaluable annual research grants from the first sponsors—energy companies and the State of New York—amounted to tens of thousands of dollars during LLE’s formative years. The underwriting of OMEGA, however, was significantly beyond their ability. Up until 1975, Washington had not been targeted for seeking funds for the program. The Atomic Energy Commission (AEC) would have been the only realistic source of the needed funds, but it had just been disbanded and a new agency, the Energy Research and Development Administration (ERDA), would replace it. President Sproull knew the newly named administrator of ERDA, Dr. Robert Seamans, Jr., and he scheduled an appointment with him the second day of ERDA’s existence. Intrigued by the University’s interest in involving industrial and state sponsors, Seamans authorized the University to present its case to Congress so that LLE might be funded in ERDA’s pending budget. Lubin’s astute testimony, along with strong support from Rochester’s congressman, Frank Horton, who had just been appointed to the Joint House-Senate Committee on Atomic Energy, resulted in LLE receiving its requested funding.
The cornerstone-laying ceremony for the new LLE building to house the new laser facility took place on 2 April 1976. The new building, with architectural design work by United Engineers and engineering design efforts by Eastman Kodak, included 100,000 square feet of laboratory and office space. The part of the building dedicated to the laser was designed for clean operations in a well-controlled temperature and humidity environment. That part was decoupled from the rest of the building’s foundations to minimize vibration coupling to the laser equipment.
Photograph of the Delta laser from the 1972 LFFP brochure.
Target fabrication was another important element of the LLE fusion experiments program during this period. LLE made significant contributions to the early state of the art of this technology including the development of drill, fill, and plug techniques; coating of smooth polymer layers; radiographic characterization of targets; target suspension techniques; and hemishell fabrication.
The early 1980s presented the LLE management with opportunities and challenges. Using shorter wavelengths appeared to be the most favorable approach for laser fusion. It was clear that embarking on such a project necessitated hard budget choices. It was also necessary to obtain the approval of the Department of Energy (DOE). The LLE management initiated a major effort to validate the physics of direct-drive inertial confinement fusion (ICF) on OMEGA with UV irradiation.
After a hard battle, approval for the conversion of the 24-beam OMEGA laser to the third harmonic was finally obtained from DOE. In return, DOE insisted on a phased implementation of the conversion over a period of three years. By the end of FY85, the full 24-beam UV conversion of OMEGA was completed–on time and on budget.
From 1983 through 1987, significant work was carried out at LLE on characterizing the physics of UV laser-matter interaction; developing tools for the design of high-performance, direct-drive capsules; and developing high-density plasma diagnostics and direct-drive capsule fabrication and characterization capabilities.
In response to a request from the White House Office of Science and Technology Policy (OSTP), the National Research Council (NRC) of the National Academy of Sciences (NAS) completed a review of the LLE in 1986. The review recognized the important worked conducted by LLE in addressing ICF research and set a goal of compressing a cryogenic direct-drive target to a density of 100 to 200 times liquid DT density as a demonstration that would justify the upgrade of the OMEGA laser to 30 kJ. To meet this objective, the Laboratory installed a KMS Fusion cryogenic target system on OMEGA and then modified the system to meet the specifications of OMEGA experiments. To meet the direct-drive uniformity objectives, LLE developed and constructed distributed phase plates (DPP’s). The use of the DPP’s on OMEGA improved the overall uniformity by a factor of 6.
With the adapted cryogenic system and the newly developed beam smoothing, LLE demonstrated the goal of 100 to 200 × liquid DT density implosions on OMEGA as reported in Nature in 1988. This was the highest compressed fuel density recorded in ICF experiments (using either the direct- or indirect-drive approach) at that time and made a strong case for the direct-drive approach.