In inertial confinement fusion (ICF), deuterium-tritium (DT) fuel is brought to densities and temperatures where fusion ignition occurs. Mix of ablator material into the fuel may prevent ignition by diluting and cooling the fuel. MARBLE experiments at the National Ignition Facility (NIF) provide new insight into how mix affects thermonuclear burn. These experiments use laser-driven capsules containing deuterated plastic foam and tritium gas. Embedded within the foam are voids of known sizes and locations, which control the degree of heterogeneity of the fuel. Initially, the reactants are separated, with tritium concentrated in the voids and deuterium in the foam. During the implosion, mix occurs, leading to DT fusion reactions in the mixed region. Here we show that by measuring ratios of DT and deuterium-deuterium (DD) neutron yields for different macropore sizes and gas compositions, effects of mix heterogeneity on thermonuclear burn may be quantified and understood for the first time.

The Marble campaign on the National Ignition Facility investigates the effect of heterogeneous mix on thermonuclear burn for comparison to a probability distribution function (PDF) burn model. Marble utilizes plastic capsules filled with deuterated plastic foam and a fill gas containing tritium. As the capsules implode, the deuterium in the foam mixes with the tritium gas, and DT neutrons are produced as the shocks compress and heat the mixture. The yield of DT neutrons is dependent on the uniformity of the mix, with more heterogeneous mix producing fewer neutrons. In Marble, the heterogeneity of the mix is controlled by varying the diameter of voids introduced into the foam. The first NIF Marble campaign has been executed in which the Marble capsules were indirectly driven with a single strong shock using NIF hohlraums. The experiments produce a low-convergence, high-ion-temperature implosion. The ratio of DT to DD neutron yield is largely consistent with uniform atomic mix for fine-pore foam, and increases slightly with void diameter, contrary to 1D simulations using the PDF burn model. Recent 3D high-resolution simulations of similar experiments performed on the Omega Laser Facility suggest an explanation.

The Failure of America’s Transferal Policy from the Cold War to the War on Terror Jason Cooley Introduction When a nation is attempting to become a potent force in the world, its leaders have a propensity to focus on the positives that will surface once this goal is achieved. What they fail to take into consideration is the manner in which several problems also emerge after a considerable amount of power is acquired. Some of these issues can be resolved rather quickly, but others take a lot of time to rectify because they are extremely complicated. One of the problems that take up much of the time of policymakers from a world power is instability within nations where military interventions are taking place. If instances from the past are examined, it becomes quite apparent that one of the ways that a major power deals with disorder is by using transferal, a policy that consists of handing security responsibilities from the intervening soldiers to indigenous parties. While the Cold War was in progress, American officials exhibited an affinity for the transferal policy. It can be said that this fondness did not dissipate following the downfall of the Soviet Union because Washington has continued to make transfers in the campaign against Islamic extremist organizations. Within this article, the reader will have an opportunity to see how it would be advantageous for the United States to move away from this approach since poor transfers in Vietnam and Afghanistan will be subjected to analysis. We will begin with the case from the Cold War. Full Text: PDF DOI: 10.15640/jirfp.v7n1a1

The impact of collisionality and the range of the interparticle interaction on the bump-on-tail instability is examined both computationally and theoretically. Using three-dimensional, nonequilibrium molecular dynamics with a force law that varies continuously from long range (pure 1/r Coulomb limit) to short range and across coupling regimes from weakly to strongly collisional, we examine properties of the instability; unlike other computational methods, molecular dynamics includes large-angle scattering, including the extreme limit of caging, and dynamical nonlinear screening across length scales as small as the interparticle spacing. A simpler theoretical model is also developed for comparison to the molecular dynamics results; we find that the two methods agree well in the appropriate limit, revealing that molecular dynamics is an accurate tool for the exploration of plasma instabilities. Our results reveal that the bump-on-tail instability exists only for long-range interactions.

We present a multiscale study examining the impact of a regional exchange of nuclear weapons on global climate. Our models investigate multiple phases of the effects of nuclear weapons usage, including growth and rise of the nuclear fireball, ignition and spread of the induced firestorm, and comprehensive Earth system modeling of the oceans, land, ice, and atmosphere. This study follows from the scenario originally envisioned by Robock, Oman, Stenchikov, et al. (2007, https://doi.org/10.5194/acp-7-2003-2007), based on the analysis of Toon et al. (2007, https://doi.org/10.5194/acp-7-1973-2007), which assumes a regional exchange between India and Pakistan of fifty 15 kt weapons detonated by each side. We expand this scenario by modeling the processes that lead to production of black carbon, in order to refine the black carbon forcing estimates of these previous studies. When the Earth system model is initiated with 5 × 109 kg of black carbon in the upper troposphere (approximately from 9 to 13 km), the impact on climate variables such as global temperature and precipitation in our simulations is similar to that predicted by previously published work. However, while our thorough simulations of the firestorm produce about 3.7 × 109 kg of black carbon, we find that the vast majority of the black carbon never reaches an altitude above weather systems (approximately 12 km). Therefore, our Earth system model simulations conducted with model‐informed atmospheric distributions of black carbon produce significantly lower global climatic impacts than assessed in prior studies, as the carbon at lower altitudes is more quickly removed from the atmosphere. In addition, our model ensembles indicate that statistically significant effects on global surface temperatures are limited to the first 5 years and are much smaller in magnitude than those shown in earlier works. None of the simulations produced a nuclear winter effect. We find that the effects on global surface temperatures are not uniform and are concentrated primarily around the highest arctic latitudes, dramatically reducing the global impact on human health and agriculture compared with that reported by earlier studies. Our analysis demonstrates that the probability of significant global cooling from a limited exchange scenario as envisioned in previous studies is highly unlikely, a conclusion supported by examination of natural analogs, such as large forest fires and volcanic eruptions.

careful literature research, LANL identified an alternative methodology to achieve our technical objectives and fully support critical model parameterization. Very-low-altitude unmanned aerial systems (UAS) photogrammetry appeared to satisfy our objectives in lieu of GB LIDAR. The SPE Phase 2 baseline collection was used as a test of this UAS photogrammetric methodology.

We have carried out several experiments on the Los Alamos proton radiography (pRad) facility to explore the growth of perturbations subjected to shockless acceleration. These experiments have involved both Tantalum and depleted Uranium plates with various initial amplitudes. The experimental platform is based on the one first developed by Barnes et al. [1] and further advanced by Raevsky [2]. This paper presents both the data for these experiments and an initial attempt to model the experiments using the simulation code FLAG [3].

Explosively driven arrested beryllium experiments were performed with post mortem characterization to evaluate the failure behaviors. The test samples were encapsulated in an aluminum assembly that was large relative to the sample, and the assembly features both axial and radial momentum traps. The sample carrier was inserted from the explosively-loaded end and has features to lock the carrier to the surrounding cylinder using the induced plastic flow. Calculations with Lagrangian codes showed that the tensile stresses experienced by the Be sample were below the spall stress. Metallographic characterization of the arrested Be showed radial cracks present in the samples may have been caused by bending moments. Fractography showed the fractures propagated from the side of the sample closest to the explosives, the side with the highest tensile stress. There was evidence that the fractures may have propagated from the circumferential crack outward and downward radially.

RATIONALEThe aim of this study was to investigate the mass spectral fragmentation of a small set of stimulants in a high‐resolution time‐of‐flight mass spectrometer equipped with a soft ionization source using vacuum ultraviolet (VUV) photons emitted from different plasma gases. It was postulated that the use of a plasma gas such as Xe, which emits photons at a lower energy than Kr or Ar, would lead to softer ionization of the test compounds, and thus to less fragmentation.METHODSA set of nine stimulants: cocaine, codeine, nicotine, methadone, phenmetrazine, pentylenetetrazole, niketamide, fencamfamine, and caffeine, was analyzed by gas chromatography/time‐of‐flight mass spectrometry (GC/TOFMS) in positive ion mode with this soft ionization source, using either Xe, Kr, or Ar as plasma gases. Working solutions of the test compounds at 0.1 to 100 ng/μL were used to establish instrument sensitivity and linearity.RESULTSAll test compounds, except methadone and pentylenetetrazole, exhibited strong molecular ions and no fragmentation with Xe‐microplasma photoionization (MPPI). Methadone exhibited significant fragmentation not only with Xe, but also with Kr and Ar, and pentylenetetrazole could not be ionized with Xe, probably because its ionization energy is above 8.44 eV. The Kr‐ and Ar‐MPPI mass spectra of the test compounds showed that the relative intensity of the molecular ion decreased as the photon energy increased.CONCLUSIONSWhen coupled to a TOF mass spectrometer this soft ionization source has demonstrated signal‐to‐noise (S/N) ratios from 7 to 730 at 100 pg per injection (depending on the compound), and a dynamic range of three orders of magnitude (100 pg to 100 ng) for some of the test compounds. Copyright © 2012 John Wiley & Sons, Ltd.

Submitted for the DPP05 Meeting of The American Physical Society Study of manufacturing induced defects in beryllium capsules for the National Ignition Facility (NIF) JAMES COOLEY, STEPHANE LAFFITE, DOUG WILSON, Los Alamos National Laboratory, Los Alamos, NM 87545 — Copper doped beryllium (BeCu) has several advantages over plastic (CH) for capsule ablator material. Unfortunately, the manufacturing process for the capsules may introduce defects that may reduce or impede capsule ignition. In this paper, we present current results from an ongoing study at the Los Alamos National Laboratory to address some of these manufacturing related issues. In particular we present results of numerical simulations that examines the effect of a thin, <1 μm, aluminum (Al) or CH joint that would be present between two machined hemispheres of BeCu. In particular, we examine the jet resulting from the heavily mixed layer3 after the shock front emerges from the BeCu into the DT ice and DT gas and we speculate on the effect of this jet on ignition. Then, we examine the effect of a fill-hole or fill-tube on jet formation for the BeCu capsule. First, we compare the results of simulations with recent experiments carried out on Omega and discuss implications for future studies. Then, we discuss simulations results for fill-holes and fill-tube and speculate on the effect of these defects on perturbations of the final ignition hotspot. 1 to whom correspondence should be addressed jhcooley@lanl.gov 2 CEA/DIF, BP12, 91680 Bruyères le Châtel, France 3 S. A. Bel’kov et al., Physics of Plasmas 6, 4728 (1999) James Cooley Los Alamos National Laboratory Date submitted: 22 Jul 2005 Electronic form version 1.4

AbstractOptimization of laser wakefield acceleration involves understanding and control of the laser evolution in tenuous plasmas, the response of the plasma medium, and its effect on the accelerating particles. We explore these phenomena in the weakly nonlinear regime, in which the laser power is similar to the critical power for self-focusing. Using Particle-In-Cell simulations with the code QuickPIC, we demonstrate that a laser pulse can remain focused in a plasma channel for hundreds of Rayleigh lengths and efficiently accelerate a high-quality electron beam to 100GeV (25GeV) in a single stage with average gradient 3.6GV/m (7.2GV/m).

D3He fuels are often used in ICF implosion experiments, either as a surrogate for DT to restrict the output neutron yield, or to produce protons for use in diagnosis of core conditions. Recent experiments have suggested that capsules filled with D3He do not behave as expected, but that both proton and neutron yields are anomalously degraded relative to the pure D2 case. We have performed direct drive implosion experiments using the Omega laser to examine the effect of 3He on DT-filled glass capsules. The use of DT fuel allows reaction history measurements to be obtained using the Gas Cherenkov diagnostic (GCD). It was hoped that the detailed information provided by GCD measurements would complement existing measurements to constrain modelling. We present recent modelling and analysis of the experiments using radiation-hydrocode simulations, and explore some of the hypotheses proposed to explain the results.

Inertial confinement fusion (ICF) capsule performance can be negatively impacted by the presence of hydrodynamic instabilities. To perform a gas fill on an ICF capsule, current plans involve drilling a small hole and inserting a fill tube to inject the gas mixture into the capsule. This introduces a perturbation on the capsule, which can seed hydrodynamic instabilities. The small hole can cause jetting of the shell material into the gas, which might adversely affect the capsule performance. We have performed simulations and experiments to study the hydrodynamic evolution of jets from high-aspect ratio holes, such as the fill tube hole. Although simulations using cold materials overpredict the amount of mass in the jet, when a plausible amount of preheat (<1 eV) is introduced, the simulations are in better agreement with the experiment.