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At least 739 records · Page 41
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Concept of operations for channel characterization and simulation of coaxial transmission channels at the National Ignition Facility (NIF)

The National Ignition Facility (NIF) at Lawrence Livermore National Laboratory (LLNL) executes experiments for inertial con nement fusion (ICF), world-class high energy density physics (HEDP), and critical national security missions. While the laser systems, target positioners, alignment systems, control systems, etc. enable the execution of such experiments, NIF’s utility would be greatly reduced without its suite of diagnostics. It would be e ectively “blind” to the incredible physics unleashed in its target chamber. Since NIF diagnostics are such an important part of its mission, the quality and reliability of the diagnostics, and of the data recorded from them, is crucial.

42 ENGINEERING↗
DOE OSTI2015

Lawrence Livermore National Laboratories Perspective on Code Development and High Performance Computing Resources in Support of the National HED/ICF Effort

Through its Advanced Scientific Computing (ASC) and Inertial Confinement Fusion (ICF) code development efforts, Lawrence Livermore National Laboratory (LLNL) provides a world leading numerical simulation capability for the National HED/ICF program in support of the Stockpile Stewardship Program (SSP). In addition the ASC effort provides high performance computing platform capabilities upon which these codes are run. LLNL remains committed to, and will work with, the national HED/ICF program community to help insure numerical simulation needs are met and to make those capabilities available, consistent with programmatic priorities and available resources.

42 ENGINEERING↗
DOE OSTI2016

Pulsed Power Science and Technology: A Strategic Outlook for the National Nuclear Security Administration (Summary)

Major advances in pulsed power technology and applications over the last twenty years have expanded the mission areas for pulsed power and created compelling new opportunities for the Stockpile Stewardship Program (SSP). This summary document is a forward look at the development of pulsed power science and technology (PPS&T) capabilities in support of the next 20 years of the SSP. This outlook was developed during a three-month-long tri-lab study on the future of PPS&T research and capabilities in support of applications to: (1) Dynamic Materials, (2) Thermonuclear Burn Physics and Inertial Confinement Fusion (ICF), and (3) Radiation Effects and Nuclear Survivability. It also considers necessary associated developments in next-generation codes and pulsed power technology as well as opportunities for academic, industry, and international engagement. The document identifies both imperatives and opportunities to address future SSP mission needs. This study was commissioned by the National Nuclear Security Administration (NNSA). A copy of the memo request is contained in the Appendix. NNSA guidance received during this study explicitly directed that it not be constrained by resource limitations and not attempt to prioritize its findings against plans and priorities in other areas of the national weapons program. That prioritization, including the relative balance amongst the three focus areas themselves, must of course occur before any action is taken on the observations presented herein. This unclassified summary document presents the principal imperatives and opportunities identified in each mission and supporting area during this study. Preceding this area-specific outlook, we discuss a cross-cutting opportunity to increase the shot capacity on the Z pulsed power facility as a near-term, cost-effective way to broadly impact PPS&T for SSP as well as advancing the science and technology to inform future SSMP milestones over the next 5-10 years. The final page of the summary presents two timelines that couch the opportunities discussed here in terms of the broader strategic timelines encapsulated in the fiscal year 2017 Stockpile Stewardship Management Plan (SSMP).

42 ENGINEERING↗
DOE OSTI2016

ARES Modeling of High-foot Implosions (NNSA Milestone #5466)

ARES “capsule only” simulations demonstrated results of applying an ASC code to a suite of high-foot ICF implosion experiments. While a capability to apply an asymmetric FDS drive to the capsule-only model using add-on Python routines exists, it was not exercised here. The ARES simulation results resemble the results from HYDRA simulations documented in A. Kritcher, et al., Phys. Plasmas, 23, 052709 (2016); namely, 1D simulation and data are in reasonable agreement for the lowest velocity experiments, but diverge from each other at higher velocities.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2016

Pulsed Power and SF 6

The Z Machine began operation in 1985 as the Particle Beam Fusion Accelerator 2 (PBFA-II). It was built as a high voltage driver to generate light ion beams in support of the Inertial Confinement Fusion (ICF) Program. In 1996 PBFA-II was converted to a high current mode to investigate recent advances in imploding wire-array X-ray generation that Sandia scientists had made at the Saturn facility. Sandia planned to split the machine’s time between the high voltage ion beam mode and the high current X-ray generation mode, but the initial tests were so successful the machine was kept in the high current configuration. The machine was renamed the ‘Z Machine’ and scientists developed a number of experimental uses for the extremely high current outputs of Z, including dynamic material studies and the Isentropic Compression Experiments (ICE). In 2007 the Z Machine was refurbished to update machine components, many of which were original to the 1985 PBFA-II configuration. During the refurbishment project new technological improvements were incorporated nearly doubling the output power of the machine without increasing its overall size.

43 PARTICLE ACCELERATORS↗
DOE OSTI2017

Carbon Capture Multidisciplinary Simulation Center Trilab Support Team (TST) Fall Meeting 2016 Report

The theme of this year’s meeting was “Predictivity: Now and in the Future”. After welcoming remarks, Erik Draeger gave a talk on the NNSA Labs’ history of predictive simulation and the new challenges faced by upcoming architecture changes. He described an example where the volume of analysis data produced by a set of inertial confinement fusion (ICF) simulations on the Trinity machine was too large to store or transfer, and the steps needed to reduce it to a manageable size. He also described the software re-engineering plan for LLNL’s suite of multiphysics codes and physics packages with a new push toward common components, making collaboration with teams like the CCMSC who already have experience trying to architect complex multiphysics code infrastructure on next-generation architectures all the more important. Phil Smith then gave an overview outlining the goals of the project, namely to accelerate development of new technology in the form of high efficiency carbon capture pulverized coal power generation as well as further optimize existing state of the art designs. He then presented a summary of the Center’s top-down uncertainty quantification approach, in which ultimate target predictivity informs uncertainty targets for lower-level components, and gave data on how close all the different components currently are to their targets. Most components still need an approximately two-fold reduction in uncertainty to hit the ultimate predictivity target, but the current accuracy is already rather impressive.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2017

Electroplating Gold-Silver Alloys for Spherical Capsules for NIF Double-Shell Targets

For Inertial Confinement Fusion (ICF) implosions, a design based on gradients of high and mid Z materials could potentially be more robust than single element capsule systems. To that end, gold and silver alloys were electroplated on 2.0 mm diameter surrogate brass spheres using a new flow–based pulsed plating method specifically designed to minimize surface roughness without reducing plating rates. The coatings were analyzed by scanning electron microscope (SEM) and white light interferometry for surface topography, and by energy dispersive x-ray spectroscopy (EDX) to determine near-surface gold and silver compositions. The alloy range attainable was 15 to 85 weight percent gold using 1:1 and 1:3 silver to gold ratio plating baths at applied potentials of -0.7 volts to -1.8 volts. This range was bounded by the open circuit potential of the system and hydrogen evolution, and in theory could be extended by using ionic liquids or aprotic solutions. Preliminary gradient trials proved constant composition alloy data could be translated to smooth gradient plating, albeit at higher gold compositions.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Development on the National Ignition Facility of a High Energy Density Opacity Platform

X-ray opacity is a crucial factor in all radiation-hydrodynamics calculations, yet it is one of the least validated of the material properties in simulation codes for high-energy-density plasmas. Recent opacity experiments at the Sandia Z-machine have shown up to factors of two discrepancies between theory and experiment for various mid-Z elements (Fe, Cr, Ni). These discrepancies raise doubts regarding the accuracy of the opacity models which are used in ICF and stewardship as well as in astrophysics. Therefore, a new experimental opacity platform has been developed on the National Ignition Facility (NIF), not only to verify the Z-machine experimental results, but also to extend the experiments to other temperatures and densities. Within the context of the national opacity strategy, the first NIF experiments were directed towards measuring the opacity of iron at a temperature of ~160 eV and an electron density of ~7xl021 cm-3(Anchor 1). The Z data agree with theory at these conditions, providing a reference point for validation of the NIF platform. Development shots on NIF have demonstrated the ability to create a sufficiently bright point backlighter using an imploding plastic capsule, and also a combined hohlraum, sample and laser drive able to produce iron plasmas at the desired conditions. Spectrometer qualification has been completed, albeit with additional improvements planned, and the first iron absorption spectra have now been obtained.

36 MATERIALS SCIENCE↗
DOE OSTI2017

LDRD Final Report: Advanced Hohlraum Concepts

Indirect drive inertial confinement fusion (ICF) experiments to date have mostly used cylindrical, laser-heated, gas-filled hohlraums to produce the radiation drive needed to symmetrically implode DT-filled fusion capsules. These hohlraums have generally been unable to produce a symmetric radiation drive through the end of the desired drive pulse, and are plagued with complications due to laser-plasma interactions (LPI) that have made it difficult to predict their performance. In this project we developed several alternate hohlraum concepts. These new hohlraums utilize different hohlraum geometries, radiation shields, and foam materials in an attempt to improve performance relative to cylindrical hohlraums. Each alternate design was optimized using radiation hydrodynamic (RH) design codes to implode a reference DT capsule with a high-density carbon (HDC) ablator. The laser power and energy required to produce the desired time-dependent radiation drive, and the resulting time-dependent radiation symmetry for each new concept were compared to the results for a reference cylindrical hohlraum. Since several of the new designs needed extra laser entrance holes (LEHs), techniques to keep small LEHs open longer, including high-Z foam liners and low-Z wires at the LEH axis, were investigated numerically. Supporting experiments and target fabrication efforts were also done as part of this project. On the Janus laser facility plastic tubes open at one end (halfraums) and filled with SiO 2 or Ta 2 O 5 foam were heated with a single 2w laser. Laser propagation and backscatter were measured. Generally the measured propagation was slower than calculated, and the measured laser backscatter was less than calculated. A comparable, scaled up experiment was designed for the NIF facility and four targets were built. Since low density gold foam was identified as a desirable material for lining the LEH and the hohlraum wall, a technique was developed to produce 550 mg/cc gold foam, and a sample of this material was successfully manufactured.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2017

Comparison of the Three NIF Ablators

Indirect drive implosion experiments on NIF have now been performed using three different ablator materials: glow discharge polymer (GDP) or CH, high density carbon (HDC, which we also refer to as diamond), and sputtered beryllium (Be). It has been appreciated for some time that each of these materials has specific advantages and disadvantages as an ICF ablator.[1-4] In light of experiments conducted on NIF in the last few years, how do these ablators compare? Given current understanding, is any ablator more or less likely to reach ignition on NIF? Has the understanding of their respective strengths and weaknesses changed since NIF experiments began? How are those strengths and weaknesses highlighted by implosion designs currently being tested or planned for testing soon? This document aims to address these questions by combining modern simulation results with a survey of the current experimental data base. More particularly, this document is meant to fulfill an L2 Milestone for FY17 to “Document our understanding of the relative advantages and disadvantages of CH, HDC, and Be designs.” Note that this document does not aim to recommend a down-selection of the current three ablator choices. It is intended only to gather and document the current understanding of the differences between these ablators and thereby inform the choices made in planning future implosion experiments. This document has two themes: (i) We report on a reanalysis project in which post-shot simulations were done on a common basis for layered shots using each ablator. This included data from keyholes, 2D ConA, and so forth, from each campaign, leading up to the layered shots. (“Keyholes” are shots dedicated to measuring the shock timing in a NIF target, as described in Ref. 5. “2DConAs” are backlit implosions in which the symmetry of the implosion is measured between about half and full convergence, as described in Ref. 6.) This set of common-basis postshot simulations is compared to the respective shots. Each was then scaled to a “full NIF” experiment that could be done using the respective ablators at full NIF power and/or energy, and these scaled-up designs were simulated in detail. (ii) The report also contains a general survey of experimental and simulated results as pertinent to comparing and evaluating the three ablators.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2017

FY17 LLNL Omega Experimental Programs

The Capseed campaign goal is to measure shock front velocity non-uniformities in Inertial Confinement Fusion (ICF) ablator materials and quantify the level of non-uniformity caused by intrinsic effects. This is done using the Omega High Resolution Velocimeter (OHRV) to obtain velocity maps of the optically reflecting shock front following release of the ablator material into either PMMA for the warm experiments or cryogenic deuterium for the cryo experiments. For the three half-days in FY17 the focus was twofold: complete measurements on the impact of oxygen heterogeneity and oxygen mitigation layers for glow discharge polymer (GDP), and begin measuring velocity non-uniformities on deep release from Be, GDP, and highdensity carbon (HDC) into D2 with improved velocity sensitivity.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2017

Hanford Site Composite Analysis Technical Approach Description: Groundwater

The groundwater facet of the revised CA is responsible for generating predicted contaminant concentration values over the entire analysis spatial and temporal domain. These estimates will be used as part of the groundwater pathway dose calculation facet to estimate dose for exposure scenarios. Based on the analysis of existing models and available information, the P2R Model was selected as the numerical simulator to provide these estimates over the 10,000-year temporal domain of the CA. The P2R Model will use inputs from initial plume distributions, updated for a start date of 1/1/2017, and inputs from the vadose zone facet, created by a tool under development as part of the ICF, to produce estimates of hydraulic head, transmissivity, and contaminant concentration over time. A recommendation of acquiring 12 computer processors and 2 TB of hard drive space is made to ensure that the work can be completed within the anticipated schedule of the revised CA.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2018

MagLIFEP and MagLIFSNL

The MagLIF campaign operated by Sandia conducted a total of four shot days in FY17 (one on OMEGA and three on OMEGA-EP) aimed at characterizing the laser heating of underdense plasmas (D2, Ar) at parameters that are relevant to the Magnetized Liner Inertial Fusion (MagLIF) ICF scheme being pursued at Sandia National Laboratories [1] [2]. MagLIF combines fuel preheat, magnetization and pulsed power implosion to significantly relax the implosion velocity and pR required for self-heating. Effective fuel preheat requires coupling several kJ of laser energy into the 10 mm long, underdense (typically ne/nc<0.1) fusion fuel without introducing significant mix. Barriers to achieving this include the presence laser plasma instabilities (LPI) as laser energy is coupled to the initially cold fuel, and the presence of a thin, polyimide laser entrance hole (LEH) foil that the laser must pass through and that can be a significant perturbation.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2018

Summaries of FY 2018 LANL experimental campaigns at the OMEGA and OMEGA-EP Laser Facilities

In FY 2018, Los Alamos National Laboratory carried out 21 shot days on the OMEGA and OMEGA-EP laser facilities in the areas of High Energy Density (HED) Science and Inertial Confinement Fusion (ICF). Our focus areas were on radiation flow, hydrodynamic turbulent mix and burn, and coupled Kelvin-Helmholtz (KH)/Richtmyer-Meshkov (RM) instability growth including in convergent geometry. We also had several focused shot days on transport properties in the kinetic regime. We continue to develop advanced diagnostics such as Neutron Imaging , and performed tests of a new imaging concept to be installed on NIF. We executed experiments in support of our double-shell campaign, and we began initial experiments using the new Revolver platform. Below is a summary of our campaigns, their motivation, and main results from this year.

47 OTHER INSTRUMENTATION↗
DOE OSTI2015

Direct observation of electrothermal instability structures in the skin layer of an intensely Ohmically heated conductor

Magnetically driven implosions (MDIs) on the Z Facility assemble high-energy-density plasmas for radiation effects and ICF experiments. MDIs are hampered by the Magneto-Rayleigh-Taylor (MRT) instability, which can grow to large amplitude from a small seed perturbation, limiting achievable stagnation pressures and temperatures. The metallic liners used in Magnetized Liner Inertial Fusion (MagLIF) experiments include astonishingly small (-10 nm RMS) initial surface roughness perturbations; nevertheless, unexpectedly large MRT amplitudes are observed in experiments. An electrothermal instability (ETI) may provide a perturbation which exceeds the initial surface roughness. For a condensed metal resistivity increases with temperature. Locations of higher resistivity undergo increased Ohmic heating, resulting in locally higher temperature, and thus still higher resistivity. Such unstable temperature (and pressure) growth produces density perturbations when the locally overheated metal changes phase, providing the seed perturbation for MRT growth. ETI seeding of MRT on thick conductors carrying current in a skin layer has thus far only been inferred by evaluating MRT amplitude late in the experiment. A direct observation of ETI is vital to ensure our simulation tools are accurately representing the seed of the deleterious MRT instability. In this LDRD project, ETI growth was directly observed on the surface of 1.0-mm-diameter solid Al rods which were pulsed with 1 MA of current in 100 ns. Fine structures resulting from ETI-driven temperature variations were observed directly through high resolution gated optical imaging. Data from two Aluminum alloys (6061 and 5N) and a variety fabrication techniques (conventional machining, single-point diamond turned, electropolished) enable evaluation of which imperfections provide a seed for ETI growth and subsequent plasma initiation. Data is relevant to the early stages of MagLIF liner implosions, when the ETI seed of MRT may be initiated, and provides a fundamentally new dataset with which to test our state-of-the-art simulation tools.

42 ENGINEERING↗
DOE OSTI2019

Implicit, manifold-preserving numerical representations and solvers for multiscale kinetic simulations of plasmas

Presentation Conclusions: We have derived manifold-preserving algorithms for kinetic plasma simulation; Collisionless (PIC): we have solved the 40-year-old algorithmic challenge of developing accurate implicit PIC algorithms; Collisional (VFP): we have demonstrated a truly multiscale algorithm that has enabled routine simulation of ICF spherical capsule implosions with a few hundred cores for a couple of days.; In both cases: Strict conservation properties have been shown to be critical for long-term accuracy.; Significant algorithmic acceleration has been achieved by using nested asymptotic models.; We have seen similar benefits in other applications

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2019

NIF Monthly Highlights for July 2019

July was a productive month for scientists at the National Ignition Facility, with a significant number of target shots performed, including many developing new platforms and taking first-of-their-kind data. The HED program, the ICF program, the National Security Applications Program and the Discovery Science users each achieved significant results. The facility itself also made tremendous progress towards commissioning several new capabilities for laser diagnostics, and target-physics diagnostic systems that measure x-ray and neutron data.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗