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[en] The National Ignition Facility at Lawrence Livermore National Laboratory was formally dedicated in May 2009. The hohlraum energetics campaign with all 192 beams began shortly thereafter and ran until early December 2009. These experiments explored hohlraum-operating regimes in preparation for experiments with layered cryogenic targets. The hohlraum energetic series culminated with an experiment that irradiated an ignition scale hohlraum with 1 MJ. The results demonstrated the ability to produce a 285 eV radiation environment in an ignition scale hohlraum while meeting ignition requirements for symmetry, backscatter and hot electron production. Complementary scaling experiments indicate that with ∼1.3 MJ, the capsule drive temperature will reach 300 eV, the point design temperature for the first ignition campaign. Preparation for cryo-layered implosions included installation of a variety of nuclear diagnostics, cryogenic layering target positioner, advanced optics and facility modifications needed for tritium operations and for routine operation at laser energy greater than 1.3 MJ. The first cyro-layered experiment was carried out on 29 September 2010. The main purpose of this shot was to demonstrate the ability to integrate all of the laser, target and diagnostic capability needed for a successful cryo-layered experiment. This paper discusses the ignition point design as well as findings and conclusions from the hohlraum energetics campaign carried out in 2009. It also provides a brief summary of the initial cryo-layered implosion.
[en] The National Ignition Facility (NIF) [J. A. Paisner, E. M. Campbell, and W. J. Hogan, Fusion Technol. 26, 755 (1994)], operating at green (2ω) light, has the potential to drive ignition targets with significantly more energy than the 1.8 MJ it will produce with its baseline, blue (3ω) operations. This results in a greatly increased 'target design space', providing a number of exciting opportunities for fusion research. These include the prospect of ignition experiments with capsules absorbing energies in the vicinity of 1 MJ. This significant increase in capsule absorbed energy over the original designs at ∼150 kJ could allow high-gain, high yield experiments on NIF. This paper reports the progress made exploring 2ω for NIF ignition, including potential 2ω laser performance, 2ω ignition target designs, and 2ω laser plasma interaction studies
[en] On the National Ignition Facility (NIF), the hot electrons generated in laser heated hohlraums are inferred from the >20 keV bremsstrahlung emission measured with the FFLEX broadband spectrometer. New high energy (>200 keV) time resolved channels were added to meet requirements for ignition and to infer the generated >170 keV hot electrons that can cause ignition capsule preheat. First hot electron measurements in near ignition scaled hohlraums heated by 96-192 NIF laser beams are presented.
[en] We analyze combustion variations in a four cylinder spark ignition engine. We apply dimensional time series analysis to heat release and construct recurrence plots for different advance angles of spark ignition. The results show that the qualitative change in combustion can be easily related to patterns in recurrence plots. Fluctuations for a larger advance angle have more deterministic nature influenced by an intermittency phenomenon
[en] In 2005, the suite of nuclear-ignition diagnostics for the NIF was defined and they are under development through collaborative efforts at several institutions. An overview of the conceptual design, the developmental status, and recent results of prototype tests on the OMEGA laser will be presented
[en] It is known that various materials are caused to spark when subjected to microwave radiation, and others can be heated to extremely high temperatures. This paper studies the behaviour of graphite under microwave radiation using a multi-mode 2.45 GHz±50 Hz microwave cavity, and its potential applications in propellant ignition systems. Evidence for a correlation between sample mass and arcing intensity is presented, and a linear relationship between sample mass and temperature is found. Both graphite powder and flakes show increasing arcing intensity with increasing mass up to ∼150 mg, after which the behaviour is more dispersed. The temperature achieved increases linearly with increasing mass, with maximum temperatures of 1,011 deg. C and 657 deg. C achieved for powder (<0.1 mm) and flakes respectively--well above thermal ignition temperatures for most common explosives.
[en] The physics of fast ignition is being studied using a petawatt laser facility at the Lawrence Livermore National Laboratory. Performance of the PW laser with deformable mirror wavefront control giving intensities up to 3x1020 Wcm-2 is described. Measurements of the efficiency of conversion of laser energy to relativistic electrons and of their energy spectrum and angular distribution including an observed narrow beam angle of ± 15 deg., are reported. Heating by the electrons to near 1keV in solid density CD2 is inferred from the thermo-nuclear neutron yield. Estimates suggest an optimized gain of 300x if the National Ignition Facility were to be adapted for fast ignition. (author)
[en] Energy resources are a major concern for the future of Mankind. With the plausible decline of fossil energy in the next decades, Nuclear Fusion is one of the major energy solutions on the long term. For many years, Europe has concentrated on Magnetic Fusion, but recently a consortium of European laboratories launched an ambitious project aiming to explore the alternative approach of Laser Fusion, the HIPER project. The main targets and challenges of this project will be presented in this talk. HIPER is based on a high repetition rate laser system, compatible with a future Laser Fusion reactor, and it aims to explore improved ignition configurations, such as Fast and Shock Ignition. The 3-years preparatory phase of this project started in 2009 is approaching its conclusion. The future of the project strongly depends on the results provided by NIF, which are at the threshold of demonstrating ignition. The mood on Fusion research is about to change. (author)
[en] The conditions for the existence and accessibility of ignited or subignited deuterium-tritium states are discussed in terms of the performance of the thermonuclear device in tritiumless discharges. The discussion includes the effects of the thermal instability of both the marginally igniting states and the nonstationary states in the start-up phase. These effects are an integral part of the problem of the accessibility to ignition under reliable conditions. Typical examples taken from the next generation of igniting tokamaks are discussed. The necessity of allowing sufficient excursion of the plasma column for a stable drive to ignition by feedback on the vertical field is underlined
[en] The National Ignition Facility (NIF), operating at green (2ω) light, has the potential to drive ignition targets with significantly more energy than the 1.8 MJ it will produce in its baseline, blue (3ω) operations. This results in a greatly increased ''target design space'', providing a number of exciting opportunities for fusion research including the possibility of ignition experiments with capsules absorbing energies in the vicinity of 1 MJ. We report the progress made exploring 2ω for NIF ignition, including potential 2ω laser performance, 2ω ignition target designs and 2ω Laser Plasma Interaction (LPI) studies