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The advanced radiographic capability (ARC) laser system, part of the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory, is a short-pulse laser capability integrated into the NIF. The ARC is designed to provide adjustable pulse lengths of ∼ 1 − 38 p s in four independent beamlets, each with energies up to 1 kJ (depending on pulse duration). A detailed model of the ARC lasers has been developed that predicts the time- and space-resolved focal spots on target for each shot. Measurements made to characterize static and dynamic wavefront characteristics of the ARC are important inputs to the code. Modeling has been validated with measurements of the time-integrated focal spot at the target chamber center (TCC) at low power, and the space-integrated pulse duration at high power, using currently available diagnostics. These simulations indicate that each of the four ARC beamlets achieves a peak intensity on target of up to a few 10 18 W / c m 2 .

The National Ignition Facility (NIF) at Lawrence Livermore National Laboratory contains a 192-beam 4.2 MJ neodymium glass laser (around 1053 nm or 1w) that is frequency converted to 351nm light or 3w. It has been designed to support the study of Inertial Confinement Fusion (ICF) and High Energy Density Physics (HEDP). The NIF Precision Diagnostic System (PDS) was reactivated and new diagnostic packages were designed and fielded that offer a more comprehensive suite of high-resolution measurements. The current NIF laser performance will be presented as well as the preliminary results obtained with the various laser experimental campaigns using the new diagnostic tool suites.

ARC is a kilojoule petawatt-class laser system which generates high energy x-ray and particle sources for radiography of experiments on the National Ignition Facility. We present recent progress on laser performance measurements and system modeling.

The necessity for durable optics for higher laser fluences and intensities grows as new technological advancements allow for increased peak powers of laser systems. This has motivated a substantial effort in the last decades to better understand laser induced damage mechanisms and their mitigation. One major damage mechanism limitation to laser systems at high peak intensities is filamentation in fused silica glass, due to Kerr self-focusing of the light [1], that has been motivating an on-going effort for the last few decades [2]. The past studies had led to a set of simplified rules that allows for the operation of laser system below the onset point for this mechanism to take place, namely what is known as the IL rule (intensity times the collapse distance before filamenting equals some empirical constant) and the Bespalov-Talanov (BT) perturbation growth theory [3-6]. The need to increase the laser beam intensities and optimize the throughput, closer to the point where the optical propagation length in the material is comparable to the predicted filamentation distance, requires revisiting and improving our understanding of the current rule set. This is especially emphasized by the shortcomings of these two highly useful yet under-justified models for the relevant situations of large aperture beams where the contrast perturbations on the beam are the seed for the filamentations (i.e., and not whole beam collapse).

We extend the split-optic approach for mitigating filamentation in a thick optical component previously proposed for small beams to conditions relevant to high-power lasers. The split-optic approach divides a thick optic into two thinner optics separated by an airgap to reduce filamentation through diffraction management. Our numerical study focuses on filamentation of a flat-top beam with intensity modulation noise sources passing through a split-optic system. The improvement in the distance to collapse in glass is shown to be potentially substantial (>30%), yet has limited increase with the airgap size, unlike the common understanding when considering a collapse of a whole beam or a sole perturbation on a beam. The improvement in the collapse distance in glass asymptotes to an upper bound value that depends mainly on the beam mean intensity and its contrast for any airgap size above some value that depends mainly on the shortest spatial periods comprising the excitation noise source. Examining the difference in the simulation results for a periodic versus a randomly generated perturbation source-term suggests that the observed effect is governed by the statistical interference dynamics of the beam while propagating through the airgap.

Characterization data for the Icarus 2 hybrid-CMOS (hCMOS) imager using near-infrared (NIR) laser pulses is presented. The Icarus 2 hCMOS imagers are four-frame burst mode cameras, with a 1024 x 512 pixel array and 25μm spatial resolution. Designed and built by Sandia National Laboratory for the Ultra-Fast X-ray Imager (UXI) program where they have been used to capture X-ray images at LLNL’s National Ignition Facility and during HED physics experiments. Temporal and spatial characterization is performed using NIR, 1053nm and 1064nm, laser pulses ranging from 43-ps to 20ns. Specific results include gate response, internal reflections, off-gate sensitivity, side-to-side timing skew, and response to a characteristic NIF-like laser pulse. Comparisons between a commercial gated, intensified CCD camera and a commercial time-integrated CMOS camera are included when relevant.

The Bespalov-Talanov gain (BT-gain) and IL-rule (i.e., the product of input intensity and self-focusing length is constant) expressions are examined and generalized for filamentation under realistic conditions associated with high power lasers: filamentation seeded by both amplitude and phase perturbations on a large, flat-top beam, and the impact of cross-phase modulation from unconverted light in UV frequency-converted lasers. The validity of these models is examined with NLSE numerical calculations, which show that there are parameters beyond the commonly-used IL rule, such as the perturbation amplitude and period content. The BT-gain model presents a fair description of the tendency of spatial periods to filament, but not of the quantitative self-focusing length. Spatial filtering of short periods is shown to suppress filamentation, due to both, the removal of the more prone to filament periods, as well as the reduction of the spatial intensity amplitude root-mean-square. At the edge of a top hat beam we find that the IL product reduces in the roll-off regions, even though the self-focusing length increases. When adding a co-propagating harmonic, we find that the cross-phase modulation (XPM) could enhance or inhibit the filamentation formation, depending on the perturbation period.

The need for optics that can sustain higher laser fluences and intensities grows as new technological advancements allow laser systems to operate at increased in peak power. This has motivated a substantial effort in recent decades to study laser-induced damage mechanisms and their mitigations. One well known laser-induced damage mechanism is filamentation in fused silica glass, due to Kerr self-focusing of the light [1]. The study of filamentation has been an ongoing effort for the last few decades [2] as it turned out to be a major limitation to laser systems at high peak intensities. Past studies have led to a set of simplified rules that allows for the operation of laser system below the onset point of filamentation to occur, namely what is known as the “IL rule” (intensity times the length before filamenting equals some empirical constant) and the Bespalov-Talanov (BT) perturbation growth theory [3-8]. The necessity to increase the laser beam intensities and optimize the throughput, closer to the point where the optical propagation length in the material is comparable to the predicted filamentation distance, requires revisiting and improving our understanding of the current rule set.

This talk will provide an overview of high power laser research at Lawrence Livermore National Laboratory (LLNL). It will discuss the status of the National Ignition Facility (NIF) laser. In addition, the talk will describe other laser development activities such as the development of high average power lasers and novel fiber lasers. The National Ignition Facility (NIF) has been in service since 2007 and operating with > 1 MJ energies since 2009. During this time the facility has transitioned to become an international user facility and increased the shot rate from ~150 target shots per year to greater than 400 shots per year. Today, the NIF plays an essential role in the US Stockpile Stewardship Program, providing data under the extreme conditions needed to validate computer models and train the next generation of stockpile stewards. Recent upgrades include the Advanced Radiographic Capability (ARC), a high energy short pulse laser used to do high resolution radiography. In addition to the NIF, this talk will include an overview of progress on the high average power laser development, recent results from fiber laser development activities and improvements to laser design and computational capabilities.

La microfinance s’est developpee dans le contexte des politiques dites de lutte contre la pauvrete par la mise au travail generalisee. Son efficacite parait tres limitee, voire vouee a l’echec, si la pauvrete n’est pas pensee comme la resultante des inegalites statutaires, des discriminations et des exclusions.Dans cette perspective, l’acces aux services financiers apparait comme un droit fondamental de la personne humaine.

Si l’argent est au cœur tant de l’intime que du collectif et est un element essentiel des attachements de l’individuel au collectif, rien d’etonnant que l’introduction de l’euro puisse etre porteuse d’inquietudes et de promesses, et de tensions contradictoires entre ce qui est espere ou redoute, chacun etant, par les contraintes de sa situation particuliere et de son vecu immediat et passe, porteur d’un degre different d’inquietudes et d’espoirs. Le moi, le rapport aux autres et le rapport au collectif sont interpelles par un changement monetaire. L’article part du macrocosme, la face politique de l’euro, pour aboutir au microcosme, les relations intimes de chacun dans sa gestion du quotidien et dans son rapport aux autres a travers ses echanges monetaires. Toutefois, a chacun des niveaux la demarche est essentiellement fondee sur une approche a micro‑echelle du changement. Il faut comprendre les representations de la totalite monetaire (ou son absence) et fixer le cadre general de la souverainete monetaire, pour interpreter gestes avec et paroles sur l’euro, devenu en quelques heures pour certains, quelques jours pour d’autres, la monnaie de paiement, si ce n’est encore de compte, de tous les jours.

Si l’argent est au cœur tant de l’intime que du collectif et est un élément essentiel des attachements de l’individuel au collectif, rien d’étonnant que l’introduction de l’euro puisse être porteuse d’inquiétudes et de promesses, et de tensions contradictoires entre ce qui est espéré ou redouté, chacun étant, par les contraintes de sa situation particulière et de son vécu immédiat et passé, porteur d’un degré différent d’inquiétudes et d’espoirs. Le moi, le rapport aux autres et le rapport au collectif sont interpellés par un changement monétaire. L’article part du macrocosme, la face politique de l’euro, pour aboutir au microcosme, les relations intimes de chacun dans sa gestion du quotidien et dans son rapport aux autres à travers ses échanges monétaires. Toutefois, à chacun des niveaux la démarche est essentiellement fondée sur une approche à micro‑échelle du changement. Il faut comprendre les représentations de la totalité monétaire (ou son absence) et fixer le cadre général de la souveraineté monétaire, pour interpréter gestes avec et paroles sur l’euro, devenu en quelques heures pour certains, quelques jours pour d’autres, la monnaie de paiement, si ce n’est encore de compte, de tous les jours. If money is as much at the heart of private as of collective life and is an essential aspect of the attachment of the individual to the collective, it is not surprising that the introduction of the euro carried with it anxieties and promises, and contradictory tensions between hoped-for and feared outcomes. Each person was the bearer to a different degree of anxieties and hopes, in the light of their specific situation and their current and past experiences. The self, the relationship to others and to the collective are interpellated by monetary change.This article starts from the macrocosm, the political aspect of the euro, to arrive at the microcosm, the intimate relations which everyone has in their management of everyday life and their relationship with others through monetary exchanges. However, at each level the approach is essentially based on a micro-scale perspective on change. It is necessary to understand representations of currency (or its absence) in their totality and determine the general framework of monetary sovereignty, in order to interpret actions with and words about the euro, which in several hours for some and several days for others became the everyday currency of payment if not of calculation.

La microfinance s’est développée dans le contexte des politiques dites de lutte contre la pauvreté par la mise au travail généralisée. Son efficacité paraît très limitée, voire vouée à l’échec, si la pauvreté n’est pas pensée comme la résultante des inégalités statutaires, des discriminations et des exclusions.Dans cette perspective, l’accès aux services financiers apparaît comme un droit fondamental de la personne humaine. Microfinance has developed in the context of so-called policies to fight poverty through putting people to work. Its effectiveness appears extremely limited, indeed doomed to failure, if poverty is not conceived as the result of statutory inequalities and forms of discrimination and exclusion. In this perspective, access to financial services appears as a fundamental human right.

To develop and test a plantar pressure control device that provides both visual and auditory feedback and is suitable for correcting plantar pressure distribution patterns in persons susceptible to neuropathic foot ulceration.Pilot test.Sports medicine laboratory in a university in France.One healthy man in his mid thirties.Not applicable. Main outcome measures A device was developed based on real-time feedback, incorporating an acoustic alarm and visual signals, adjusted to a specific pressure load. Plantar pressure measured during walking, at 6 sensor locations over 27 steps under 2 different conditions: (1) natural and (2) unloaded in response to device feedback.The subject was able to modify his gait in response to the auditory and visual signals. He did not compensate for the decrease of peak pressure under the first metarsal by increasing the duration of the load shift under this area. Gait pattern modification centered on a mediolateral load shift.The auditory signal provided a warning system alerting the user to potentially harmful plantar pressures. The visual signal warned of the degree of pressure. People who have lost nociceptive perception, as in cases of diabetic neuropathy, may be able to change their walking pattern in response to the feedback provided by this device. The visual may have diagnostic value in determining plantar pressures in such patients. This pilot test indicates that further studies are warranted.

Non-burning thermonuclear fuel implosion experiments have been fielded on the National Ignition Facility to assess progress toward ignition by indirect drive inertial confinement fusion. These experiments use cryogenic fuel ice layers, consisting of mixtures of tritium and deuterium with large amounts of hydrogen to control the neutron yield and to allow fielding of an extensive suite of optical, x-ray and nuclear diagnostics. The thermonuclear fuel layer is contained in a spherical plastic capsule that is fielded in the center of a cylindrical gold hohlraum. Heating the hohlraum with 1.3 MJ of energy delivered by 192 laser beams produces a soft x-ray drive spectrum with a radiation temperature of 300 eV. The radiation field produces an ablation pressure of 100 Mbar which compresses the capsule to a spherical dense fuel shell that contains a hot plasma core 80 µm in diameter. The implosion core is observed with x-ray imaging diagnostics that provide size, shape, the absolute x-ray emission along with bangtime and hot plasma lifetime. Nuclear measurements provide the 14.1 MeV neutron yield from fusion of deuterium and tritium nuclei along with down-scattered neutrons at energies of 10–12 MeV due to energy loss by scattering in the dense fuel that surrounds the central hot-spot plasma. Neutron time-of-flight spectra allow the inference of the ion temperature while gamma-ray measurements provide the duration of nuclear activity. The fusion yield from deuterium–tritium reactions scales with ion temperature, which is in agreement with modeling over more than one order of magnitude to a neutron yield in excess of 1014 neutrons, indicating large confinement parameters on these first experiments.