[en] Analysis and radiation hydrodynamics simulations for expected high-gain fusion target performance on a demonstration 1-GWe Laser Inertial Fusion Energy (LIFE) power plant in the mid-2030s timeframe are presented. The required laser energy driver is 2.2 MJ at a 0.351-(micro)m wavelength, and a fusion target gain greater than 60 at a repetition rate of 16 Hz is the design goal for economic and commercial attractiveness. A scaling-law analysis is developed to benchmark the design parameter space for hohlraum-driven central hot-spot ignition. A suite of integrated hohlraum simulations is presented to test the modeling assumptions and provide a basis for a near-term experimental resolution of the key physics uncertainties on the National Ignition Facility (NIF). The NIF is poised to demonstrate ignition by 2012 based on the central hot spot (CHS) mode of ignition and propagating thermonuclear burn (1). This immediate prospect underscores the imperative and timeliness of advancing inertial fusion as a carbon-free, virtually limitless source of energy by the mid-21st century to substantially offset fossil fuel technologies. To this end, an intensive effort is underway to leverage success at the NIF and to provide the foundations for a prototype 'LIFE.1' engineering test facility by ∼2025, followed by a commercially viable 'LIFE.2' demonstration power plant operating at 1 GWe by ∼2035. The current design goal for LIFE.2 is to accommodate ∼2.2 MJ of laser energy (entering the high-Z radiation enclosure or 'hohlraum') at a 0.351-(micro)m wavelength operating at a repetition rate of 16 Hz and to provide a fusion target yield of 132 MJ. To achieve this design goal first requires a '0-d' analytic gain model that allows convenient exploration of parameter space and target optimization. This step is then followed by 2- and 3-dimensional radiation-hydrodynamics simulations that incorporate laser beam transport, x-ray radiation transport, atomic physics, and thermonuclear burn (2). These simulations form the basis for assessing the susceptibility to hydrodynamic instability growth, target performance margins, laser backscatter induced by plasma density fluctuations within the hohlraum, and the threat spectrum emerging from the igniting capsule, e.g., spectra, fluences and anisotropy of the x rays and ions, for input into the chamber survivability calculations. The simulations follow the guidelines of a 'point design' methodology, which formally designates a well-defined milestone in concept development that meets established criteria for experimental testing. In Section 2, the 0-d analytic gain model to survey gain versus laser energy parameter space is discussed. Section 3 looks at the status of integrated hohlraum simulations and the needed improvements in laser-hohlraum coupling efficiency to meet the LIFE.2 threshold (net) target gain of ∼60. Section 4 considers advanced hohlraum designs to well exceed the LIFE.2 design goal for satisfactory performance margins. We summarize in Sec. 5.

[en] Progress in simulation and experiment enhances prospects for NIF double-shell ignition in FY2011. Simulation studies have identified a stable double-shell ignition design based on graded density shells and metallic foams. Recent double-shell implosion experiments on Omega have shown unprecedented performance. Identification of possible failure mechanisms has motivated new and improved double shell designs: e.g., like-material outer surface of inner shell and foam; greatly reduced gap size; and density-matched glue. Progress in double-shell research has inspired many exciting materials science advances on the path to ignition

[en] Analysis and radiation-hydrodynamics simulations for expected high-gain fusion target performance on a demonstration 1-GWe Laser Inertial Fusion Energy (LIFE) power plant are presented. The required laser energy driver is 2.2 MJ at a 0.351-μm wavelength, and a fusion target gain greater than 60 at a repetition rate of 16 Hz is the design goal for economic and commercial attractiveness. A scaling-law analysis is developed to benchmark the design parameter space for hohlraum-driven central hot-spot ignition. A suite of integrated hohlraum simulations is presented to test the modeling assumptions and provide a basis for near-term experimental resolution of the key physics uncertainties on the National Ignition Facility.

[en] A major challenge in achieving ignition with double-shells is controlling the mix of the dense, high-Z pusher into the DT gas. During implosion, interface perturbations become unstable as they are subjected to either impulsive (Richtmyer-Meshkov) or time-dependent (Rayleigh-Taylor) accelerations. These processes are especially critical for double-shells since density gradient stabilization mechanisms (that play a key role in the baseline cryogenic target) are not present. To study the nonlinear RT evolution for such a large range in modes we use the parallel 3-D rad-hydro code HYDRA. Simulations have revealed a new pathway for the RT instability of perturbations on the outer surface of the inner shell leading to shell disruption. We demonstrate that this instability can be controlled by tamping the inner shell with a low-Z material but it is not entirely suppressed. We find that the pusher/tamper interface transitions to turbulence at late times with large Reynolds number but still the integrity of the pusher is maintained. Furthermore, numerical studies suggest that for perturbations with mode numbers (l > 600), the mix-width at the pushed tamper interface approaches a constant value. Finally, to avoid turbulence onset altogether we investigate a new pusher with an imprinted density-gradient scale length in combination with a CuO/Cu₂O foam. Preliminary 2-D simulations with mode numbers up tp l = 612 show virtually no growth in this design

[en] Solar coronal arches heated by turbulent ion-cyclotron waves may suffer significant cross-field transport by these waves. Nonlinear processes fix the wave-propagation speed at about a tenth of the ion thermal velocity, which seems sufficient to spread heat from a central core into a large cool surrounding cocoon. Waves heat cocoon ions both through classical ion-electron collisions and by turbulent stochastic ion motions. Plausible cocoon sizes set by wave damping are in roughly kilometers, although the wave-emitting core may be only 100 m wide. Detailed study of nonlinear stabilization and energy-deposition rates predicts that nearby regions can heat to values intermediate between the roughly electron volt foot-point temperatures and the about 100 eV core, which is heated by anomalous Ohmic losses. A volume of 100 times the core volume may be affected. This qualitative result may solve a persistent problem with current-driven coronal heating; that it affects only small volumes and provides no way to produce the extended warm structures perceptible to existing instruments. 17 refs

[en] Lasing between excited states and the ground state following optical-field ionization is studied. Saturation of an x-ray laser when the lower lasing level is a ground state of a H-like or Li-like ion is discussed. Efficiencies of 10^-5 to 10^-4 are calculated for the 3d_5/2--2p_3/2 transition at 98 Angstrom in Li-like Ne. The assumption that the fine-structure levels are populated according to their statistical weights is shown to be justified through comparisons with calculations using a detailed atomic model. The effect of saturation by a given fine-structure transition on the populations of the fine-structure levels is analyzed. 4 refs., 2 figs

[en] An anisotropic equation of state for disk galaxies is developed and applied to the study of galactic energy extremization. Higher moments of the Boltzmann equations are considered and an equation of state is derived for an anisotropic, cool self-gravitating system. Euler-Lagrange equations for the energy extremals are developed, and arguments are presented for the constant rotation speed solution as the preferred energy extremal. It is concluded that galactic energy is still extremalized by a flat rotation profile when both anisotropic and baroclinic effects are considered. 19 refs

[en] One of the most important challenges confronting laser-driven capsule implosion experiments will be a quantitative evaluation of the implosion dynamics. Since these experiments will encounter extreme conditions of pressure and temperature, establishing robust, sensitive diagnostics will be difficult. Radiochemical signatures provide insight into material mixing and laser drive asymmetry and complement x-ray and other nuclear diagnostics, since the relevant nuclear reactions sample core implosion conditions directly. Simulations of an ignition double shell target indicate that several experimentally accessible isomeric ratios will be suitable monitors of mix.

[en] Design studies for recombination x-ray lasers based on plasmas ionized by high intensity, short pulse optical lasers are presented. Transient lasing on n = 3 to n = 2 transitions in Lithium-like Neon allows for moderately short wavelengths (≤ 100 angstrom) without requiring ionizing intensities associated with relativistic electron quiver energies. The electron energy distribution following the ionizing pulse affects directly the predicted gains for this resonance transition. Efficiencies of 10^-6 or greater are found for plasma temperatures in the vicinity of 40 eV. Simulation studies of parametric heating phenomena relating to stimulated Raman and Compton scattering are presented. For electron densities less than about 2.5 x 10²⁰ cm^-3 and peak driver intensity of 2 x 10¹⁷ W/cm² at 0.25 μm with pulse length of 100 fsec, the amount of electron heating is found to be marginally significant. For Lithium-like Aluminum, the required relativistic ionizing intensity gives excessive electron heating and reduced efficiency, thereby rendering this scheme impractical for generating shorter wavelength lasing (≤ 50 angstrom) in the transient case. Following the transient lasing phase, a slow hydrodynamic expansion into the surrounding cool plasma is accompanied by quasi-static gain on the n = 4 to n = 3 transition in Lithium-like Neon. Parametric heating effects on gain optimization in this regime are also discussed. 18 refs., 6 figs

[en] Double-shell (DS) targets (Amendt, P. A. et al., 2002) offer a complementary approach to the cryogenic baseline design (Lindl, J. et al., 2004) for achieving ignition on the National Ignition Facility (NIF). Among the expected benefits are the ease of room temperature preparation and fielding, the potential for lower laser backscatter and the reduced need for careful shock timing. These benefits are offset, however, by demanding fabrication tolerances, e.g., shell concentricity and shell surface smoothness. In particular, the latter is of paramount importance since DS targets are susceptible to the growth of interface perturbations from impulsive and time-dependent accelerations. Previous work (Milovich, J. L. et al., 2004) has indicated that the growth of perturbations on the outer surface of the inner shell is potentially disruptive. To control this instability new designs have been proposed requiring bimetallic inner shells and material-matching mid-Z nanoporous foam. The challenges in manufacturing such exotic foams have led to a further evaluation of the densities and pore sizes needed to reduce the seeding of perturbations on the outer surface of the inner shell, thereby guiding the ongoing material science research efforts. Highly-resolved 2D simulations of porous foams have been performed to establish an upper limit on the allowable pore sizes for instability growth. Simulations indicate that foams with higher densities than previously thought are now possible. Moreover, while at the present time we are only able to simulate foams with average pore sizes larger than 1 micron (due to computational limitations), we can conclude that these pore sizes are potentially problematic. Furthermore, the effect of low-order hohlraum radiation asymmetries on the growth of intrinsic surface perturbations is also addressed. Highly-resolved 2D simulations indicate that the transverse flows that are set up by these low-order mode features (which can excite Kelvin-Helmholtz instabilities) are not large enough to offset the overall robustness of our current design