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At least 775 records · Page 43
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Solid Radiochemistry Nuclear Diagnostic Results from Exploding Pusher Shot (N130503-002) at the National Ignition Facility

The Solid Radiochemistry (SRC) nuclear diagnostic platform has been developed for the assessment of various performance parameters, such as areal fuel density and ablator-fuel mixing, associated with the capsule implosion of DT-fuel, hohlraum based shots at the National Ignition Facility (NIF). This diagnostic is based on the collection and characterization of debris from the capsule and surrounding materials (primarily gold from the hohlraum). SRC utilizes two diagnostic instrument manipulators (DIMs), 90-78 and 0-0, to field debris collectors (maximum of four metallic and/or graphite foils per DIM) inside the NIF chamber during shots. The debris collectors are removed after a shot and transferred to the Nuclear Counting Facility (NCF) for the measurement of gold activation (Au-196m and Au-196) and capture (Au-198) products via gamma spectroscopy. The results from SRC which show a strong dependency on an independently measured neutron down scatter ratio (DSR) are utilized as part of a 1-D capsule model to determine the areal densities (ρR(DT) and ρR(CH)) during burn. This report summarizes the SRC results from the Indirect Drive Exploding Pusher shot (N130503-002) designed to produce low ρR at burn time (~40 mg/cm 2 ) leading to a significant decrease in DSR (0.23±0.07 %). As a result, this shot is considered a calibration shot for SRC nuclear diagnostic.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2014

High-Energy-Density Turbulent Mixing Experiments

LANL has been conducting isolated shear experiments at Omega and NIF. The experiments’ mixing layer growth can be profitably simulated and analyzed using the BHR turbulence model. We are also taking orthogonal data to constrain the three-dimensional structure of the turbulence. We anticipate finding interesting results of scaling from Ω to NIF, based on the preliminary data taken this month.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2014

National Ignition Facility User Guide

This user manual is intended to provide sufficient information to allow researchers to become familiar with NIF and develop preliminary plans for NIF experiments. It also provides references to further detail that will allow detailed experiment planning.

99 GENERAL AND MISCELLANEOUS↗
DOE OSTI2015

Inertial Fusion Power Plant Concept of Operations and Maintenance

Parsons and LLNL scientists and engineers performed design and engineering work for power plant pre-conceptual designs based on the anticipated laser fusion demonstrations at the National Ignition Facility (NIF). Work included identifying concepts of operations and maintenance (O&M) and associated requirements relevant to fusion power plant systems analysis. A laser fusion power plant would incorporate a large process and power conversion facility with a laser system and fusion engine serving as the heat source, based in part on some of the systems and technologies advanced at NIF. Process operations would be similar in scope to those used in chemical, oil refinery, and nuclear waste processing facilities, while power conversion operations would be similar to those used in commercial thermal power plants. While some aspects of the tritium fuel cycle can be based on existing technologies, many aspects of a laser fusion power plant presents several important and unique O&M requirements that demand new solutions. For example, onsite recovery of tritium; unique remote material handling systems for use in areas with high radiation, radioactive materials, or high temperatures; a five-year fusion engine target chamber replacement cycle with other annual and multi-year cycles anticipated for major maintenance of other systems, structures, and components (SSC); and unique SSC for fusion target waste recycling streams. This paper describes fusion power plant O&M concepts and requirements, how O&M requirements could be met in design, and how basic organizational and planning issues can be addressed for a safe, reliable, economic, and feasible fusion power plant.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2015

Inline CBET Model Including SRS Backscatter

Cross-beam energy transfer (CBET) has been used as a tool on the National Ignition Facility (NIF) since the first energetics experiments in 2009 to control the energy deposition in ignition hohlraums and tune the implosion symmetry. As large amounts of power are transferred between laser beams at the entrance holes of NIF hohlraums, the presence of many overlapping beat waves can lead to stochastic ion heating in the regions where laser beams overlap [P. Michel et al., Phys. Rev. Lett. 109, 195004 (2012)]. Using the CBET gains derived in this paper, we show how to implement these equations in a ray-based laser source for a rad-hydro code.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2015

Generalized Lawson Criteria for Inertial Confinement Fusion

The Lawson Criterion was proposed by John D. Lawson in 1955 as a general measure of the conditions necessary for a magnetic fusion device to reach thermonuclear ignition. Over the years, similar ignition criteria have been proposed which would be suitable for Inertial Confinement Fusion (ICF) designs. This paper will compare and contrast several ICF ignition criteria based on Lawson’s original ideas. Both analytical and numerical results will be presented which will demonstrate that although the various criteria differ in some details, they are closely related and perform similarly as ignition criteria. A simple approximation will also be presented which allows the inference of each ignition parameter directly from the measured data taken on most shots fired at the National Ignition Facility (NIF) with a minimum reliance on computer simulations. Evidence will be presented which indicates that the experimentally inferred ignition parameters on the best NIF shots are very close to the ignition threshold.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2016

Initiated chemical vapor deposited nanoadhesive for bonding National Ignition Facility's targets

Currently, the target fabrication scientists in National Ignition Facility Directorate at Lawrence Livermore National Laboratory (LLNL) is studying the propagation force resulted from laser impulses impacting a target. To best study this, they would like the adhesive used to glue the target substrates to be as thin as possible. The main objective of this research project is to create adhesive glue bonds for NIF’s targets that are ≤ 1 μm thick. Polyglycidylmethacrylate (PGMA) thin films were coated on various substrates using initiated chemical vapor deposition (iCVD). Film quality studies using white light interferometry reveal that the iCVD PGMA films were smooth. The coated substrates were bonded at 150 °C under vacuum, with low inflow of Nitrogen. Success in bonding most of NIF’s mock targets at thicknesses ≤ 1 μm indicates that our process is feasible in bonding the real targets. Key parameters that are required for successful bonding were concluded from the bonding results. They include inert bonding atmosphere, sufficient contact between the PGMA films, and smooth substrates. Average bond strength of 0.60 MPa was obtained from mechanical shearing tests. The bonding failure mode of the sheared interfaces was observed to be cohesive. Future work on this project will include reattempt to bond silica aerogel to iCVD PGMA coated substrates, stabilize carbon nanotube forests with iCVD PGMA coating, and kinetics study of PGMA thermal crosslinking.

36 MATERIALS SCIENCE↗
DOE OSTI2016

LLNL ICF highlights for the period of July 14, 2016 to July 20, 2016

LLNL executed two HED Fused Silica Dome experiments as part of the complex hydrodynamics campaign on NIF. These shots assessed breakout times and velocities of shocks at five different angles separated by 45°. Each target looked at three different locations on the capsule measuring the shock breakout time and speed. The experiments used a significantly larger hohlraum and energy in the laser pulse than in previous complex hydrodynamics hohlraums. LLNL conducted a shot on NIF to continue developing a high pressure drive platform for Rayleigh-Taylor strength experiments. VISAR was the primary diagnostic and returned good quality data.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

PRP Comments for ICF Q1/Q2 FY17 Experiments 3/10/16

The PRP generally endorsed the Program plan during the short time for discussions. We agree that the strategy to develop a hohlraum that is symmetric and has low laser-plasma instabilities and to develop an alternative method for supporting the capsule is the best path forward for making progress in understanding ignition performance. The Program is oriented toward a milestone in 2020 for “determining the efficacy of NIF for ignition and credible physics-scaling to multi-megajoule yields for all ICF approaches.” We are concerned that the time and resources are not sufficient to vet all of the various approaches that are being pursued to make an informed decision by this date. For NIF to meet this goal, a process will be needed to to select the most promising paths forward. We recommend that the Program develop this process for selecting the path forward to optimize resources. We were glad to see that the direct drive program took our comments under consideration. We think that the proposed experiments have the program headed in a better direction. The PRP had only a short time to discuss the detailed experimental proposals. The following are comments on the detailed proposals. We did not have time to discuss them as a group. They represent individual opinions and provided to you as feedback to your proposals.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2016

An Overview of the Los Alamos Inertial Confinement Fusion and High-Energy-Density Physics Research Programs

The Los Alamos Inertial Confinement Fusion and Science Programs engage in a vigorous array of experiments, theory, and modeling. We use the three major High Energy Density facilities, NIF, Omega, and Z to perform experiments. These include opacity, radiation transport, hydrodynamics, ignition science, and burn experiments to aid the ICF and Science campaigns in reaching their stewardship goals. The ICF program operates two nuclear diagnostics at NIF, the neutron imaging system and the gamma reaction history instruments. Both systems are being expanded with significant capability enhancements.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2016

(U) Estimating the Photonics Budget, Resolution, and Signal Requirements for a Multi-Monochromatic X-ray Imager

This document examines the performance of a generic flat-mirror multimonochromatic imager (MMI), with special emphasis on existing instruments at NIF and Omega. We begin by deriving the standard equation for the mean number of photons detected per resolution element. The pinhole energy bandwidth is a contributing factor; this is dominated by the finite size of the source and may be considerable. The most common method for estimating the spatial resolution of such a system (quadrature addition) is, technically, mathematically invalid for this case. However, under the proper circumstances it may produce good estimates compared to a rigorous calculation based on the convolution of point-spread functions. Diffraction is an important contribution to the spatial resolution. Common approximations based on Fraunhofer (farfield) diffraction may be inappropriate and misleading, as the instrument may reside in multiple regimes depending upon its configuration or the energy of interest. It is crucial to identify the correct diffraction regime; Fraunhofer and Fresnel (near-field) diffraction profiles are substantially different, the latter being considerably wider. Finally, we combine the photonics and resolution analyses to derive an expression for the minimum signal level such that the resulting images are not dominated by photon statistics. This analysis is consistent with observed performance of the NIF MMI.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2018

2017 Joint Experimental Diagnostics Initiative (JEDI) Annual Report - April 2018

The Joint Enhanced Diagnostics Initiative (JEDI) collaboration between the National Ignition Facility (NIF) and the Atomic Weapons Establishment (AWE) has the goal of enhancing the experimental capabilities of the NIF to enable collaborative experiments of interest to both the U.S. and U.K. stockpile stewardship activities.

98 NUCLEAR DISARMAMENT, SAFEGUARDS, AND PHYSICAL P↗
DOE OSTI2018

Laser-Driven Megavolt X-Ray and Neutron Source Optimization

This 4-month feasibility study assessed the options, trade-offs and major issues in using National Ignition Facility (NIF) and Advanced Radiographic Capability (ARC)-class laser beams for multipulse MeV x-ray and neutron radiography of high explosives (HE) driven experiments. It was performed in close collaboration with a second FS evaluating future HE radiography requirements and expected laser-based source data quality with respect to existing and alternate radiography sources. The study first reviewed the existing published data on MeV x-ray and neutron sources compared to requirements on yield (10 14 /sr for X-rays, > 10 13 /sr for neutrons), spot size (< 1 mm) and duration (< 20 ns). For MeV neutron sources, the preferred options are DTfilled exploding pusher targets or stagnating DT plasmas, each source requiring 50 kJ level. few ns beam irradiation at 0.5 or 0.35 micron wavelength. The preferred X-ray MeV source option to be fully assessed by a follow-up SI is an angularly and temporally-multiplexed multi-burst version of a Bremsstrahlung source (Courtois et al. 2011) irradiated by up to 7 10 ps, kJ-class 1 micron wavelength lasers beams. This multi-burst laser mode, submitted as an ROI and patent, should increase final laser optics damage energy thresholds based on 2 pulse tests and hence allow near full extraction of the 15 kJ of 1 micron laser energy available on a NIF beamline. Hydrodynamic simulations were used to evaluate the effects of preceding pulse irradiation on target integrity, and show that this can be mitigated by using 3D structured targets.

47 OTHER INSTRUMENTATION↗
DOE OSTI2019

The Crystal Backlighter Imager JGBuscho Comprehensive Report 2019

The National Ignition Facility (NIF) is a system of 192 lasers indirectly pointed at a target roughly the size of a millimeter. This target is held at the center of a vacuum chamber 30 feet in diameter. Diagnostics to understand the laser implosion and interaction of the target are inserted into the target chamber during laser shots on Diagnostic Insertion Manipulators (DIMs). Diagnostics are attached to these DIMs as complex assemblies known as snouts. The Crystal Backlighter Imager (CBI) is a snout used to radiograph the capsule implosion. The x-ray radiography of the imploding targets has been used in the past at the NIF with pinhole imaging. A limitation of the pinhole imaging systems is the radiograph becomes overwhelmed with self-emission and key features of the implosion are not visible late in time during the implosion. CBI implements a spherically bent crystal matched to a backlighter atomic line. By doing so, the backlighter atomic line can dominate the self-emission thus allowing the crystals narrow bandwidth to image late in time radiographs. This ability allows for visualizing the capsule structure and defects.

42 ENGINEERING↗
DOE OSTI2019

Exploring Deuterium-Tritium Gas-Filled Hohlraums as a High-Yield Neutron Source

Inverted-corona targets as neutron sources for high-energy-density applications were tested experimentally using the OMEGA laser. In a corona fusion target, laser beams directly ablate a layer of fusion fuel on the inner surface of a capsule. As the ablative flows converge, the plasma particles transition to collisional stagnation, heating the ions and generating fusion reactions. Based on a recent publication these targets show promise as a neutron source, with extrapolated yields at NIF scale of up to 1e17. Additionally, these targets are robust to low-mode drive asymmetries, enabling the possibility of single-sided laser drive, making them an ideal backlighter source for neutron-radiography applications. A number of different targets were fielded in experiments on the OMEGA laser. The 1.8-mm diameter plastic (CH) capsules featured either one or two laser-entrance holes (LEH’s), and were either lined with deuterated plastic (CD), or filled with 1.5-atm deuterium gas. Contrary to predictions by the hydrodynamics code HYDRA, the experiments exhibit a strong correlation between total neutron yield and CD liner thickness, indicating substantial mix of CH wall material into the ablated CD coronal plasma. The thickest liner targets with approximately 10 kJ of incident laser energy performed consistent with previously published data, while the data at 18 kJ laser energy may also be subject to mix from wall material. The yield from the gas-filled capsules was less than from 10-μm CD lined targets at the same laser energy, which may als be explained by wall material mixing into the fusion fuel. Finally, the experiments demonstrated similar performance between a 1-LEH and a 2-LEH target irradiated with comparable laser-energies, a key finding for demonstrating the utility of the inverted-corona neutron source for radiography applications. Future work will focus on developing the platform for NIF experiments.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2019

Defining the Direction of Nuclear-Plasma Interaction Research at the National Ignition Facility

Electron-mediated nuclear-plasma interactions (NPIs) have the potential to change nuclear reaction rates in high energy density plasma (HEDP) environments, such as those found in experiments at the National Ignition Facility (NIF), in astrophysical phenomenon, or in nuclear detonations, relative to conventional laboratory measurements on room-temperature targets. Two Discovery Science shots to detect these interactions at the NIF were conducted in January and September 2017 at the conclusion of a campaign to develop the indirect-drive exploding pusher experimental platform and diagnostics. These shots were designed to measure the differential population of a high-spin isomer of 133 Xe of an inplasma versus a control sample, where a non-zero differential would indicate a measurable influence of the plasma on 134 Xe(n,2n) reactions. Preliminary observations from these shots were consistent with a small NPI effect, but improved theoretical understanding coupled with refined data analysis were needed to definitively establish the discovery or lack thereof. Achieving both of these, a statistically-credible NPI was indeed observed at a level predicted by an adapted Monte Carlo gamma-cascade model, a significant lowering by of the isomerto- ground state activity ratio in 133 Xe.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Effect of Impurity Atoms on Thermonuclear Yield

The presence of impurity atoms in an inertial confinement fusion (ICF) implosion can greatly affect the burning of the thermonuclear fuel. This is a serious concern for attaining ignition as high atomic number atoms, such as carbon, can mix into the hot spot and reach the deuterium–tritium (DT) fuel, absorb energy from the implosion, and radiate away that energy. The temperature of the DT fuel drops and reduces the reactivity of the fuel resulting in lower thermonuclear yield. Fuel impurities can also be a useful diagnostic as when higher-Z atoms, such as Ar, Kr, and Xe, are purposefully mixed into the fuel. From the spectra emitted by these atoms, the temperature and density of the fuel can be deduced. The long history of using such tracer atoms by the national ICF program shows the great advances in experimental technique, diagnostic instruments, and atomic-physics modeling over the past 50 years. A particular set of experiments, the “High-Z” campaign, is reviewed in depth as this was the most systematic study of tracer element composition and quantity ever reported. Difficulties in interpreting the results of those experiments due to the limited code capabilities at that time are discussed. A main concern for the High-Z campaign was the then current state of non-Local Thermodynamic Equilibrium (nLTE) atomic physics models. The present state of nLTE modeling and its implementation in Los Alamos’s multi-physics codes is discussed in this report. To further the understanding of the complex interaction of high-Z atoms in the gas, a survey of relevant existing experimental platforms at the National Ignition Facility (NIF) and the Omega Laser Facility are presented along with the current state of pertinent diagnostics at NIF and Omega. This review concludes with a discussion of the trade-off available between temperature and volume of the imploded ICF capsule with the goal of maximizing the total yield.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2020

Exploring applications of laser-produced relativistic pair plasma jets for high-energy-density physics and astrophysics (LDRD Final Report)

We have successfully completed the ER project on the relativistic electron-positron “pair” plasmas which have unique physics property fundamental to High Energy Density (HED) plasma physics and laboratory astrophysics. Over the three-year span, we completed three discovery science experiments on NIF ARC, established a new NIF platform for the pair plasma experiments which also benefited a range of other science and HED experiments using ARC. Additional 5 experimental campaigns on Omega and Gekko facilities have also been executed successfully. Our results on the pair physics and pair-plasma interactions have been published in journal and conferences and highlighted on the Lab’s Newsline.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗