When built, the National Ignition Facility (NIF) will house the world's most powerful neodymium glass laser system. NIF will be 50 times more powerful than the Laboratory's Nova laser, currently the world's most powerful. The NIF will contain 192 independent laser beams, or "beamlets," each with a square aperture of a little less than 40 cm on a side. For economy and efficiency, beamlets will be stacked four high and twelve wide into four large arrays. The beamlines will require more than 9000 large-format optics (greater than 40 x 40 cm) and several thousand smaller optics. Compared to the size of the current Nova facility at LLNL, which uses a single-pass amplifier laser architecture, the compact multipass design of the proposed NIF system allows us to put a laser with a typical output that is 40 times greater than Nova's into a building only about twice the size. This article follows the path of a photon from the master oscillator and preamplifier, through the NIF main laser components, to the target. It also highlights some of the development efforts, begun many years ago, for components, such as the multipass glass amplifiers and plasma electrode Pockels cell, that allow us to design a large, multipass glass laser economically and at very low risk. Results from our recently completed Beamlet Demonstration Project, involving a prototype NIF beamline, along with the models and design codes we are testing ensure that we can have great confidence in the performance projected for NIF.
Since the end of the Cold War with the demise of the Soviet Union, the U.S. nuclear weapons program has changed dramatically. A major change has been the moratorium on underground nuclear testing, which is likely to be extended indefinitely by a Comprehensive Test- Ban Treaty. Although there are now far fewer weapons and weapon types than only a few years ago, the nuclear stockpile nevertheless remains, and U.S. policy will continue to rely on nuclear deterrence for the foreseeable future. Because the U.S. must be confident that the nuclear arsenal would perform reliably if needed, reliance on testing to assess weapon performance must be replaced by reliance on thorough scientific understanding and better predictive models of performance -- that is, science-based stockpile stewardship. The National Ignition Facility (NIF) will enable us to produce energy densities (energies per particle) that overlap with the energy densities produced in nuclear weapons, yet the total energy available on NIF will be a minuscule fraction of the total energy from a weapon. This combination of low total energy with weapons- regime energy density will allow us to pursue, besides ignition experiments, many nonignition experiments. These will allow us to improve our understanding of materials and processes in extreme conditions by isolating various fundamental physics processes and phenomena for separate investigation. Such studies will include opacity to radiation, equations of state, and hydrodynamic instability. In addition to these, we will study processes in which two or more such phenomena come into play, such as in radiation transport and in ignition. Weapons physics research on NIF offers a considerable benefit to stockpile stewardship, not only in enabling us to keep abreast of issues associated with an aging stockpile, but also in offering a major resource for training the next generation of scientists who will monitor the stockpile.
The proposed National Ignition Facility (NIF) will provide LLNL researchers as well as others in the scientific community committed to developing Inertial Fusion Energy (IFE) with the means of developing and testing data and materials that are key to the long- term goal of building and operating IFE power plants as clean, viable, environmentally safe sources of inexhaustible energy. When the NIF demonstrates fusion ignition, which is central to proving the feasibility of IFE, it will tell us much about IFE target optimization and fabrication, provide important data on fusion-chamber phenomena and technologies, and demonstrate the safe and environmentally benign operation of an IFE power plant. In accomplishing these tasks, the NIF will also provide the basis for future decisions about IFE development programs and facilities, such as the planned Engineering Test Facility (ETF). Furthermore, it will allow the U.S. to expand its expertise in inertial fusion and supporting industrial technology as well as promote U.S. leadership in energy technologies, provide clean, viable alternatives to oil and other polluting fossil fuels, and reduce energy-related emissions of greenhouse gases.
Last March, a group of scientists convened at the University of California, Berkeley, to discuss the potential scientific applications of the National Ignition Facility (NIF) -- a 192-beam, neodymium glass laser that will be used to obtain the high-energy physics data needed to maintain the nation's nuclear stockpile. The objective of the gathering was to identify areas of research in which the NIF could be used to advance knowledge in the physical sciences and to define a tentative program of high-energy laser experiments. The scientists determined that the most effective scientific applications of the NIF would be in astrophysics, hydrodynamics, high-pressure physics, and plasma physics. In astrophysics, the NIF would give scientists the ability to synthesize and analyze the plasmas that occur at all stages of stellar evolution. In hydrodynamics, it would enable them to investigate flow problems under conditions that cannot be obtained by the conventional wind tunnel or shock tube. In high-pressure physics, it would allow scientists to investigate material behavior at pressures from 1 to 100 terapascals and temperatures up to a few hundred electron volts so that they could validate their theoretical models of material behavior. Scientists would also be able to convert NIF laser energy to a wide variety of x-ray and particle sources needed to address important questions in basic and applied physics. With the NIF, scientists could push the x-ray laser interferometer to shorter x-ray laser wavelengths so that it would be a more valuable diagnostic tool in the study and characterization of large-scale plasmas. In short, the NIF would enable scientists to explore a previously inaccessible region of physical phenomena that could validate their current theories and experimental observations and provide a foundation for new knowledge of the physical world.
To ensure the safety of workers and the public and to assess potential environmental impacts, we have completed the first of a series of safety and environmental analyses related to the proposed National Ignition Facility (NIF). On the basis of its review of the Preliminary Hazards Analysis report, the DOE has concurred with the categorization of the NIF as a radiological low-hazard, non-nuclear facility. Our studies to date show that the NIF will present no significant environmental or health and safety risk. For example, the average annual biological radiation dose to a NIF worker is estimated to be about 0.01 rem. This value is less than 10% of the DOE guideline. As part of the National Environmental Protection Act (NEPA) determination process established by the DOE, the public will be invited to participate in reviewing environmental, safety, and health issues related to the NIF.
December 1994 in PDF format (3,300K)
and LLNL Disclaimers