Search NASA⌕ Search

SEARCH · Search NASA

Results for “facility”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Radiochemical determination of Inertial Confinement Fusion capsule compression at the National Ignition Facility

We describe a radiochemical measurement of the ratio of isotope concentrations produced in a gold hohlraum surrounding an Inertial Confinement Fusion capsule at the National Ignition Facility (NIF). We relate the ratio of the concentrations of (n,γ) and (n,2n) products in the gold hohlraum matrix to the down-scatter of neutrons in the compressed fuel and, consequently, to the fuel's areal density. The observed ratio of the concentrations of {sup 198m+g}Au and {sup 196g}Au is a performance signature of ablator areal density and the fuel assembly confinement time. We identify the measurement of nuclear cross sections of astrophysical importance as a potential application of the neutrons generated at the NIF.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2015

Three-dimensional simulations of National Ignition Facility implosions: Insight into experimental observables

We simulate in 3D both the hydrodynamics and, simultaneously, the X-ray and neutron diagnostic signatures of National Ignition Facility (NIF) implosions. We apply asymmetric radiation drive to study the impact of low mode asymmetry on diagnostic observables. We examine X-ray and neutron images as well as neutron spectra for these perturbed implosions. The X-ray images show hot spot evolution on small length scales and short time scales, reflecting the incomplete stagnation seen in the simulation. The neutron images show surprising differences from the X-ray images. The neutron spectra provide additional measures of implosion asymmetry. Flow in the hot spot alters the neutron spectral peak, namely, the peak location and width. The changes in the width lead to a variation in the apparent temperature with viewing angle that signals underlying hot spot asymmetry. We compare our new expectations based on the simulated data with NIF data. We find that some recent cryogenic layered experiments show appreciable temperature anisotropy indicating residual flow in the hot spot. We also find some trends in the data that do not reflect our simulation and theoretical understanding.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2015

Simulation study of 3–5 keV x-ray conversion efficiency from Ar K-shell vs. Ag L-shell targets on the National Ignition Facility laser

Tailored, high-flux, multi-keV x-ray sources are desirable for studying x-ray interactions with matter for various civilian, space and military applications. For this study, we focus on designing an efficient laser-driven non-local thermodynamic equilibrium 3–5 keV x-ray source from photon-energy-matched Ar K-shell and Ag L-shell targets at sub-critical densities (∼n{sub c}/10) to ensure supersonic, volumetric laser heating with minimal losses to kinetic energy, thermal x rays and laser-plasma instabilities. Using HYDRA, a multi-dimensional, arbitrary Lagrangian-Eulerian, radiation-hydrodynamics code, we performed a parameter study by varying initial target density and laser parameters for each material using conditions readily achievable on the National Ignition Facility (NIF) laser. We employ a model, benchmarked against Kr data collected on the NIF, that uses flux-limited Lee-More thermal conductivity and multi-group implicit Monte-Carlo photonics with non-local thermodynamic equilibrium, detailed super-configuration accounting opacities from CRETIN, an atomic-kinetics code. While the highest power laser configurations produced the largest x-ray yields, we report that the peak simulated laser to 3–5 keV x-ray conversion efficiencies of 17.7% and 36.4% for Ar and Ag, respectively, occurred at lower powers between ∼100–150 TW. For identical initial target densities and laser illumination, the Ag L-shell is observed to have ≳10× higher emissivity per ion per deposited laser energy than the Ar K-shell. Although such low-density Ag targets have not yet been demonstrated, simulations of targets fabricated using atomic layer deposition of Ag on silica aerogels (∼20% by atomic fraction) suggest similar performance to atomically pure metal foams and that either fabrication technique may be worth pursuing for an efficient 3–5 keV x-ray source on NIF.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2015

Hydrodynamic instability growth of three-dimensional, “native-roughness” modulations in x-ray driven, spherical implosions at the National Ignition Facility

Hydrodynamic instability growth experiments with three-dimensional (3-D) surface-roughness modulations were performed on plastic (CH) shell spherical implosions at the National Ignition Facility (NIF) [E. M. Campbell, R. Cauble, and B. A. Remington, AIP Conf. Proc. 429, 3 (1998)]. The initial capsule outer-surface roughness was similar to the standard specifications (“native roughness”) used in a majority of implosions on NIF. The experiments included instability growth measurements of the perturbations seeded by the thin membranes (or tents) used to hold the capsules inside the hohlraums. In addition, initial modulations included two divots used as spatial fiducials to determine the convergence in the experiments and to check the accuracy of 3D simulations in calculating growth of known initial perturbations. The instability growth measurements were performed using x-ray, through-foil radiography of one side of the imploding shell, based on time-resolved pinhole imaging. Averaging over 30 similar images significantly increases the signal-to-noise ratio, making possible a comparison with 3-D simulations. At a convergence ratio of ∼3, the measured tent and divot modulations were close to those predicted by 3-D simulations (within ∼15%–20%), while measured 3-D, broadband modulations were ∼3–4 times larger than those simulated based on the growth of the known imposed initial surface modulations. In addition, some of the measured 3-D features in x-ray radiographs did not resemble those characterized on the outer capsule surface before the experiments. One of the hypotheses to explain the results is based on the increased instability amplitudes due to modulations of the oxygen content in the bulk of the capsule. As the target assembly and handling procedures involve exposure to UV light, this can increase the uptake of the oxygen into the capsule, with irregularities in the oxygen seeding hydrodynamic instabilities. These new experimental results have prompted looking for ways to reduce UV light exposure during target fabrication.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2015

Note: A monoenergetic proton backlighter for the National Ignition Facility

A monoenergetic, isotropic proton source suitable for proton radiography applications has been demonstrated at the National Ignition Facility (NIF). A deuterium and helium-3 gas-filled glass capsule was imploded with 39 kJ of laser energy from 24 of NIF’s 192 beams. Spectral, spatial, and temporal measurements of the 15-MeV proton product of the {sup 3}He(d,p){sup 4}He nuclear reaction reveal a bright (10{sup 10} protons/sphere), monoenergetic (ΔE/E = 4%) spectrum with a compact size (80 μm) and isotropic emission (∼13% proton fluence variation and <0.4% mean energy variation). Simultaneous measurements of products produced by the D(d,p)T and D(d,n){sup 3}He reactions also show 2 × 10{sup 10} isotropically distributed 3-MeV protons.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2017

Capsule implosions for continuum x-ray backlighting of opacity samples at the National Ignition Facility

Direct drive implosions of plastic capsules have been performed at the National Ignition Facility to provide a broad-spectrum (500–2000 eV) X-ray continuum source for X-ray transmission spectroscopy. The source was developed for the high-temperature plasma opacity experimental platform. Initial experiments using 2.0 mm diameter polyalpha-methyl styrene capsules with ~20 μm thickness have been performed. X-ray yields of up to ~1 kJ/sr have been measured using the Dante multichannel diode array. The backlighter source size was measured to be ~100 μm FWHM, with ~350 ps pulse duration during the peak emission stage. Lastly, these results are used to simulate transmission spectra for a hypothetical iron opacity sample at 150 eV, enabling the derivation of photometrics requirements for future opacity experiments.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2013

Development of CCD Cameras for Soft X-ray Imaging at the National Ignition Facility

The Static X-Ray Imager (SXI) is a National Ignition Facility (NIF) diagnostic that uses a CCD camera to record time-integrated X-ray images of target features such as the laser entrance hole of hohlraums. SXI has two dedicated positioners on the NIF target chamber for viewing the target from above and below, and the X-ray energies of interest are 870 eV for the “soft” channel and 3 – 5 keV for the “hard” channels. The original cameras utilize a large format back-illuminated 2048 x 2048 CCD sensor with 24 micron pixels. Since the original sensor is no longer available, an effort was recently undertaken to build replacement cameras with suitable new sensors. Three of the new cameras use a commercially available front-illuminated CCD of similar size to the original, which has adequate sensitivity for the hard X-ray channels but not for the soft. For sensitivity below 1 keV, Lawrence Livermore National Laboratory (LLNL) had additional CCDs back-thinned and converted to back-illumination for use in the other two new cameras. In this paper we describe the characteristics of the new cameras and present performance data (quantum efficiency, flat field, and dynamic range) for the front- and back-illuminated cameras, with comparisons to the original cameras.

National Ignition Facility, X-ray diagnostic, X-ra↗
DOE OSTI2018

Time-resolved PIV measurements in a low-aspect ratio facility of randomly packed spheres and flow analysis using modal decomposition

This work experimentally investigated the flow characteristics in a facility with randomly packed spheres at a low-aspect ratio of 4.4. Velocity fields in the near-wall region and in the pores between spheres were obtained by employing the matched-index-of-refraction (MIR) and time-resolved particle image velocimetry (TR-PIV) techniques for Reynolds numbers of 340, 520, and 720. From the obtained TR-PIV velocity vector fields, flow characteristics including first- and second-order statistics, such as mean velocity, root-mean-square fluctuating velocity, and Reynolds stress profiles, were computed. The effects of the wall enclosure and Reynolds numbers on the flow patterns were investigated by comparing the computed flow statistics and evaluating two-point cross correlations of the velocities measured adjacent to and far from the wall. Comparisons of the mean velocities, root-mean-square fluctuating velocities, and Reynolds stress component showed an increase in flow mixing and turbulent intensity in the gaps between spheres in the packed bed. The re-circulation-region sizes, however, were found to be independent from an increase in Reynolds numbers. Finally, flow modal decompositions, such as the proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD), were applied to the vorticity fields extracted from sub-regions located near and far from the wall to reveal the most dominant POD and DMD flow structures.

42 ENGINEERING↗
DOE OSTI2017

Conceptual magnet design study for fusion nuclear science facility [Magnet design study for fusion nuclear science facility]

The Fusion Nuclear Science Facility (FNSF) is a nuclear confinement device to provide the integrated fusion environment with fusion reactor components. The FNSF is the stepping stone to bridge the technical gaps of burning plasma and nuclear science between the International Thermal Nuclear Experimental Reactor (ITER), currently under construction in the south of France, and the demonstration power plant (DEMO). For the next-step fusion reactors, resistive copper magnet cannot be a sustainable solution due to large power consumption in coils of large size needed. Both Low temperature superconductor (LTS) and high temperature superconductor (HTS) are considered for the FNSF magnet design based on the state-of-the-art fusion superconducting magnet technology. Input parameters to FNSF magnet design include magnetic field of 7.5 T at plasma center with a major radius of 4.8 m and minor radius of 1.2 m, and a peak field of over 16 T on the TF coils. The high magnetic field can be achieved by using the high performance ternary Restack Rod Process (RRP) Nb3Sn strands for toroidal field (TF) magnets and a high aspect ratio rectangular cable-in-conduit conductor (CICC) design. The conductor design concept and TF coil winding pack composition and dimension are discussed based on the horizontal maintenance scheme. Neutron radiation limits for the LTS and HTS conductors and electrical insulation materials are reviewed based on the available materials previously tested. The material radiation limits for FNSF magnets are defined as part of the conceptual design studies. In conclusion, the global structural analysis of FNSF magnets based on the radial build was performed to validate feasibility for the plant layout toward horizontal maintenance and global structural integrity of its magnet system.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2016

A facile cathode design combining Ni-rich layered oxides with Li-rich layered oxides for lithium-ion batteries

A facile synthesis method was developed to prepare xLi 2 MnO 3 ·(1-x)LiNi 0.7 Co 0.15 Mn 0.15 O 2 (x = 0, 0.03, 0.07, 0.10, 0.20, and 0.30 as molar ratio) cathode materials, combining the advantages of high specific capacity from Ni-rich layered phase and surface chemical stability from Li-rich layered phase. X-ray diffraction (XRD), high resolution transmission electron microscope (HRTEM) and electrochemical charge/discharge performance confirm the formation of a Li-rich layered phase with C2/m symmetry. Most importantly, high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM) reveals a spatial relationship that Li-rich nano-domain islands are integrated into a conventional Ni-rich layered matrix (R$\bar{3}$m). This is the first time that Li-rich phase has been directly observed inside a particle at the nano-scale, when the overall composition of layered compounds (Li 1+δ Ni x Mn y M 1-x-y-δ O 2 , M refers to transition metal elements) is Ni-rich (x > 0.5) rather than Mn-rich (y > 0.5). Remarkably, xLi 2 MnO 3 ·(1-x)LiNi 0.7 Co 0.15 Mn 0.15 O 2 cathode with optimized x value shows superior electrochemical performance at C/3, i.e., 170 mA h g -1 with 90.3 % of capacity retention after 400 cycles at 25 °C and 164 mA h g -1 with 81.3 % capacity retention after 200 cycles at 55 °C.

25 ENERGY STORAGE↗