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The National Ignition Facility (NIF), the world's largest and most energetic laser system, is now operational at Lawrence Livermore National Laboratory. A key goal of the NIF is to demonstrate fusion ignition for the first time in the laboratory. Its flexibility allows multiple target designs (both indirect and direct drive) to be fielded, offering substantial scope for optimization of a robust target design. In this paper we discuss an approach to generating gigawatt levels of electrical power from a laser-driven source of fusion neutrons based on these demonstration experiments. This 'LIFE' concept enables rapid time-to-market for a commercial power plant, assuming success with ignition and a technology demonstration program that links directly to a facility design and construction project. The LIFE design makes use of recent advances in diode-pumped, solid-state laser technology. It adopts the paradigm of Line Replaceable Units utilized on the NIF to provide high levels of availability and maintainability and mitigate the need for advanced materials development. A demonstration LIFE plant based on these design principles is described, along with the areas of technology development required prior to plant construction. A goal-oriented, evidence-based approach has been proposed to allow LIFE power plant rollout on a time scale that meets policy imperatives and is consistent with utility planning horizons. The system-level delivery builds from our prior national investment over many decades and makes full use of the distributed capability in laser technology, the ubiquity of semiconductor diodes, high volume manufacturing markets, and U.S. capability in fusion science and nuclear engineering. The LIFE approach is based on the ignition evidence emerging from NIF and adopts a line-replaceable unit approach to ensure high plant availability and to allow evolution from available technologies and materials. Utilization of a proven physics platform for the ignition scheme is an essential component of an acceptably low-risk solution. The degree of coupling seen on NIF between driver and target performance mandates that little deviation be adopted from the NIF geometry and beamline characteristics. Similarly, the strong coupling between subsystems in an operational power plant mandates that a self-consistent solution be established via an integrated facility delivery project. The benefits of separability of the subsystems within an IFE plant (driver, chamber, targets, etc.) emerge in the operational phase of a power plant rather than in its developmental phase. An optimized roadmap for IFE delivery needs to account for this to avoid nugatory effort and inconsistent solutions. For LIFE, a system design has been established that could lead to an operating power plant by the mid-2020s, drawing from an integrated subsystem development program to demonstrate the required technology readiness on a time scale compatible with the construction plan. Much technical development work still remains, as does alignment of key stakeholder groups to this newly emerging development option. If the required timeline is to be met, then preparation of a viable program is required alongside the demonstration of ignition on NIF. This will enable timely analysis of the technical and economic case and establishment of the appropriate delivery partnership.

The oxide dispersion strengthened steel MA956 was friction stir welded using eight different rotational speed/translational speed combinations using a polycrystalline cubic boron nitride tool. Weld parameter conditions with high thermal input produced defect-free, full penetration welds. Electron backscatter diffraction showed a significant increase in grain size in the stir zone, a body centered cubic torsional texture in the stir zone, and a sharp transition in grain size across the thermo-mechanically affected zone. Micro-indentation results showed an asymmetric reduction in hardness across the transverse section of the weld that was sensitive to the heat input. This change in hardness is explained by the increase in grain size and may be described using a Hall-Petch type relationship. This work was sponsored by a collaborative research agreement between the Naval Postgraduate School and Lawrence Livermore National Laboratory.

The structure of laser-shock-compressed polycrystalline iron was probed using in situ x-ray diffraction over a pressure range spanning the α-ε phase transition. Measurements were also made of the c/a ratio in the ε phase, which, in contrast with previous in situ x-ray diffraction experiments performed on single crystals and large-scale molecular dynamics (MD) simulations are close to those found in high-pressure diamond anvil cell experiments. This is consistent with the observation that significant plastic flow occurs within the nanosecond time scale of the experiment. Furthermore, within the sensitivity of the measurement technique, the fcc phase that had been predicted by MD simulations was not observed. © 2011 American Physical society.