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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.

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At least 721 records · Page 40
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Applied axial magnetic field effects on laboratory plasma jets: Density hollowing, field compression, and azimuthal rotation

We experimentally measure the effects of an applied axial magnetic field (B z ) on laboratory plasma jets and compare experimental results with numerical simulations using an extended magnetohydrodynamics code. A 1 MA peak current, 100 ns rise time pulse power machine is used to generate the plasma jet. On application of the axial field, we observe on-axis density hollowing and a conical formation of the jet using interferometry, compression of the applied B z using magnetic B-dot probes, and azimuthal rotation of the jet using Thomson scattering. Experimentally, we find densities ≤ 5×10 17 cm -3 on-axis relative to jet densities of ≥ 3×10 18 cm -3 . For aluminum jets, 6.5 ± 0.5 mm above the foil, we find on-axis compression of the applied 1.0 ± 0.1 T B z to a total 2.4 ± 0.3 T, while simulations predict a peak compression to a total 3.4 T at the same location. On the aluminum jet boundary, we find ion azimuthal rotation velocities of 15-20 km/s, while simulations predict 14 km/s at the density peak. We discuss possible sources of discrepancy between the experiments and simulations, including: surface plasma on B-dot probes, optical fiber spatial resolution, simulation density floors, and 2D vs. 3D simulation effects. Lastly, this quantitative comparison between experiments and numerical simulations helps elucidate the underlying physics that determine the plasma dynamics of magnetized plasma jets.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2018

Developing a long-duration Zn K-α source for x-ray scattering experiments

We are developing a long-duration K-α x-ray source at the Omega laser facility. Such sources are important for x-ray scattering measurements at small scattering angles where high spectral resolution is required. To date, He-α x-ray sources are the most common probes in scattering experiments, using ns-class lasers to heat foils to keV temperatures, resulting in K-shell emission from He-like charge states. The He-α spectrum can be broadened by emission from multiple charge states and lines (e.g., He-like, Li-like, Be-like). For this, we combine the long duration of He-α sources with the narrow spectral bandwidth of cold K-α emission. A Ge foil is irradiated by the Omega laser, producing principally Ge He-α emission, which pumps Zn K-α emission at 8.6 keV from a nearby Zn layer. Using this technique, we demonstrate a long-duration Zn K-α source suitable for scattering measurements. Our experimental results show a 60% reduction in spectral bandwidth compared to a standard Zn He-α source, significantly improving the measurement precision of scattering experiments with small inelastic shifts.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Photo-z outlier self-calibration in weak lensing surveys

Calibrating photometric redshift errors in weak lensing surveys with external data is extremely challenging. In this work, we show that both Gaussian and outlier photo-z parameters can be self-calibrated from the data alone. This comes at no cost for the neutrino masses, curvature and dark energy equation of state w0, but with a 65% degradation when both w0 and wa are varied. We perform a realistic forecast for the Vera Rubin Observatory (VRO) Legacy Survey of Space and Time (LSST) 3× 2 analysis, combining cosmic shear, projected galaxy clustering and galaxy - galaxy lensing. We confirm the importance of marginalizing over photo-z outliers. We examine a subset of internal cross-correlations, dubbed "null correlations", which are usually ignored in 3× 2 analyses. Despite contributing only ~ 10% of the total signal-to-noise, these null correlations improve the constraints on photo-z parameters by up to an order of magnitude. Using the same galaxy sample as sources and lenses dramatically improves the photo-z uncertainties too. Together, these methods add robustness to any claim of detected new Physics, and reduce the statistical errors on cosmology by 15% and 10% respectively. Finally, including CMB lensing from an experiment like Simons Observatory or CMB-S4 improves the cosmological and photo-z posterior constraints by about 10%, and further improves the robustness to systematics. To give intuition on the Fisher forecasts, we examine in detail several toy models that explain the origin of the photo-z self-calibration. Our Fisher code LaSSI (Large-Scale Structure Information), which includes the effect of Gaussian and outlier photo-z, shear multiplicative bias, linear galaxy bias, and extensions to LCDM, is publicly available at \href{https://github.com/EmmanuelSchaan/LaSSI}{https://github.com/EmmanuelSchaan/LaSSI}.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

SU-E-T-588: Optimization of Imaging Following 223Ra Administration in Targeted Alpha-Emitting Radionuclide Therapy of Bone Metastases

Purpose: With a growing demand of alpha-emitting radiopharmaceuticals, especially Xofigo ({sup 223}RaCl{sub 2}) which is used in the treatment of metastatic bone disease, the optimization of dosimetry becomes necessary. Indeed, in Europe, as stated on the council directive 2013/59/euratom, exposures of target volumes for radiotherapeutic purposes shall be individually planned taking into account that doses to non-target volumes and tissues shall be as low as reasonably achievable. To that aim, the possibility of imaging {sup 223}Ra was first investigated. Methods: The experiments were conducted at the Hopital Europeen Georges Pompidou with an Infinia Hawkeye 4 gamma camera, equipped with a medium-energy collimator. Imaging parameters, such as sensibility, spatial resolution and energy spectrum, were determined using several physical phantoms with a source of 6 MBq of {sup 223}Ra. Bone metastases were modeled with a NEMA Body Phantom to investigate image degradation based on the concentration of {sup 223}Ra. Results: The acquired energy spectrum allowed to visualize several photon peaks: at 85, 154 and 270 keV. Camera sensitivity measured from the phantom study was 102.3 cps/MBq for the 85 keV ± 20 %, 89.9 cps/MBq for the 154 ± 20 % window and 65.4 cps/MBq for the 270 ± 10 % window. The spatial resolution (full-width at half-maximum) was respectively 1.7, 1.9 and 1.8 cm for the three energy windows. SPECT/CT images of NEMA Body Phantom without and with attenuation have permitted to determine the best reconstruction parameters. Conclusion: This study has demonstrated that it is possible to obtain clinically relevant information from images of {sup 223}Ra. All these results will be valuable to analyze biodistribution imaging of the radiopharmaceutical in the patient body and go further in the reconstruction of patient images in order to personalize the dosimetry.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2023

NOvA Current Status and Future Prospects

NOvA is a two detector, long baseline, neutrino oscillation experiment utilizing the NuMI beamline at Fermilab to study neutrino oscillations through muon (anti)neutrino disappearance and electron (anti)neutrino appearance. NOvA's primary goals are to make determinations of the neutrino mass hierarchy and the octant of ${\theta}_{23}$, and to measure possible CP violation. Along with standard three flavor neutrino oscillations, NOvA data is used to study cross sections in the near detector, neutrino oscillations beyond the three flavor framework such as sterile neutrinos and non-standard interactions, along with other exotic neutrino interactions from astrophysical sources including supernovae. I will provide an overview of the NOvA detectors, share some current results from the experiment, and discuss the future of NOvA operations and analyses.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

The Future of High-Energy Astrophysical Neutrino Flavor Measurements

The next generation of neutrino telescopes, including Baikal-GVD, KM3NeT, P-ONE, TAMBO, and IceCube-Gen2, will be able to determine the flavor of high-energy astrophysical neutrinos with 10% uncertainties. With the aid of future neutrino oscillation experiments --- in particular JUNO, DUNE, and Hyper-Kamiokande --- the regions of flavor composition at Earth that are allowed by neutrino oscillations will shrink by a factor of ten between 2020 and 2040. We critically examine the ability of future experiments and show how these improvements will help us pin down the source of high-energy astrophysical neutrinos and a sub-dominant neutrino production mechanism with and without unitarity assumed. As an illustration of beyond-the-Standard-Model physics, we also show that the future neutrino measurements will constrain the decay rate of heavy neutrinos to be below $2\times 10^{-5}~$$m$/eV/s assuming they decay into invisible particles.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1991

Aeroacoustics of Flight Vehicles: Theory and Practice. Volume 1: Noise Sources

Methodology recommended to evaluate aeroacoustic related problems is provided, and approaches to their solutions are suggested without extensive tables, nomographs, and derivations. Orientation is toward flight vehicles and emphasis is on underlying physical concepts. Theoretical, experimental, and applied aspects are covered, including the main formulations and comparisons of theory and experiment. The topics covered include: propeller and propfan noise, rotor noise, turbomachinery noise, jet noise classical theory and experiments, noise from turbulent shear flows, jet noise generated by large-scale coherent motion, airframe noise, propulsive lift noise, combustion and core noise, and sonic booms.

Propeller noise↗
DOE OSTI2017

Neutrino Physics at Drexel

Our primary goal is to improve the understanding of the properties and interactions of neutrinos. We are pursuing this by means of the DUNE long-baseline and PROSPECT short-baseline neutrino experiments. For DUNE, a neutrino beam from Fermilab will be detected at the SURF facility in South Dakota, with the aim of determining the neutrino mass hierarchy (the mass ordering of neutrino flavors), and a measurement or limit on CP-violation via neutrinos. Our near-term experimental goal is to improve the characterization of the neutrino beam by measurements of muons produced as a byproduct of neutrino beam generation, to quantify the beam composition and flux. The short-range neutrino program has the aim of using the HFIR reactor at Oak Ridge as a neutrino source, with a detector placed nearby to find if there are short-distance oscillations to sterile neutrino flavors, and to resolve the 'reactor neutrino spectral anomaly' which has shown up as an unexplained 'bump' in the neutrino energy spectrum in recent experiments.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Gamma-ray bounds from EAS detectors and heavy decaying dark matter constraints

The very high energy Galactic γ-ray sky is partially opaque in the (0.1–10) PeV energy range. In the light of the recently detected high energy neutrino flux by IceCube, a comparable very high energy γ-ray flux is expected in any scenario with a sizable Galactic contribution to the neutrino flux. Here we elaborate on the peculiar energy and anisotropy features imposed upon these very high energy γ-rays by the absorption on the cosmic microwave background photons and Galactic interstellar light. As a notable application of our considerations, we study the prospects of probing the PeV-scale decaying DM scenario, proposed as a possible source of IceCube neutrinos, by extensive air shower (EAS) cosmic ray experiments. In particular, we show that anisotropy measurements at EAS experiments are already sensitive to τ{sub DM}∼O(10{sup 27}) s and future measurements, using better gamma/hadron separation, can improve the limit significantly.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Simulations of Dynamo and Magnetorotational Instability in Madison Plasma Experiments and Astrophysical Disks

Magnetic fields are observed to exist on all scales in many astrophysical sources such as stars, galaxies, and accretion discs. Understanding the origin of large scale magnetic fields, whereby the field emerges on spatial scales large compared to the fluctuations, has been a particularly long standing challenge. Our physics objective are: 1) what are the minimum ingredients for large-scale dynamo growth? 2) could a large-scale magnetic field grow out of turbulence and sustained despite the presence of dissipation? These questions are fundamental for understanding the large-scale dynamo in both laboratory and astrophysical plasmas. Here, we report major new findings in the area of Large-Scale Dynamo (magnetic field generation).

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS2006

The Space Physics of Life: Searching for Biosignatures on Habitable Icy Worlds Affected by Space Weathering

Accessible surfaces of the most likely astrobiological habitats (Mars, Europa, Titan) in the solar system beyond Earth are exposed to various chemical and hydrologic weathering processes directly or indirectly induced by interaction with the overlying space environment. These processes can be both beneficial, through provision of chemical compounds and energy, and destructive, through chemical dissociation or burial, to detectable presence of biosignatures. Orbital, suborbital, and surface platforms carrying astrobiological instrumentation must survive, and preferably exploit, space environment interactions to reach these habitats and search for evidence of life or its precursors. Experience from Mars suggests that any detection of biosignatures must be accompanied by characterization of the local chemical environment and energy sources including irradiation by solar ultraviolet photons and energetic particles from the space environment. Orbital and suborbital surveys of surface chemistry and astrobiological potential in the context of the space environment should precede targeted in-situ measurements to maximize probability of biosignature detection through site selection. The Space Physics of Life (SPOL) investigation has recently been proposed to the NASA Astrobiology Institute and is briefly described in this presentation. SPOL is the astrobiologically relevant study of the interactions and relationships of potentially? or previously inhabited, bodies of the solar system with the surrounding environments. This requires an interdisciplinary effort in space physics, planetary science, and radiation biology. The proposed investigation addresses the search for habitable environments, chemical resources to support life, and techniques for detection of organic and inorganic signs of life in the context of the space environment.

Cooper, John F.↗
NASA NTRS1993

Sources of Na for the Io atmosphere

The physics and geology of Io have been extensively studied, but there has been little discussion of the chemistry. Relatively little is known about Io chemistry, but there are constraints. Further, it will be a long time before improvements will result from direct observation, given the severe difficulties with the Galileo mission. Via laboratory simulation experiments, plausible thermochemical and photochemical processes which determine the nature and amounts of surface constituents of Io are explored. The well-known density of Io shows that the planet overall is rocky. Because the orbit of Io is well within the magnetosphere of Jupiter and because Io only has a thin, transient SO2 atmosphere, the surface is continually sputtered with magnetospheric ions. Complex processes ionize and accelerate the Io surface atoms to keV and MeV energies. Remarkably, only S, O, and Na ions were found by Voyager. Sputtering also produces an atomic cloud of Na and S (O not observable) with a trace of K. Both gaseous and solid SO2 are known from spectroscopic studies. A trace of H2S and possibly CO2 are present. Geologic features are interpreted in terms of elemental S, but there is no direct evidence for this constituent. We thus have a rocky planet which does not have rocks on the surface. Our general goal is to understand the cycling of Na, S, and O through the crust and atmosphere on present-day Io and to understand how Io evolved to this state. A specific objective was to determine the phases on the surface which are the source of the Na in the atmosphere of Io.

Burnett, D. S.↗
DOE OSTI2015

Visualization of expanding warm dense gold and diamond heated rapidly by laser-generated ion beams

With the development of several novel heating sources, scientists can now heat a small sample isochorically above 10,000 K. Although matter at such an extreme state, known as warm dense matter, is commonly found in astrophysics (e.g., in planetary cores) as well as in high energy density physics experiments, its properties are not well understood and are difficult to predict theoretically. This is because the approximations made to describe condensed matter or high-temperature plasmas are invalid in this intermediate regime. A sufficiently large warm dense matter sample that is uniformly heated would be ideal for these studies, but has been unavailable to date. We have used a beam of quasi-monoenergetic aluminum ions to heat gold and diamond foils uniformly and isochorically. For the first time, we visualized directly the expanding warm dense gold and diamond with an optical streak camera. Furthermore, we present a new technique to determine the initial temperature of these heated samples from the measured expansion speeds of gold and diamond into vacuum. We anticipate the uniformly heated solid density target will allow for direct quantitative measurements of equation-of-state, conductivity, opacity, and stopping power of warm dense matter, benefiting plasma physics, astrophysics, and nuclear physics.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2018

Development and Validation of a Geant4 Radiation Shielding Simulation Framework

Geant4 (`Geometry and Tracking') is a C++ Monte- Carlo simulation toolkit developed by the Geant4 Collaboration under CERN and is used to describe inter- actions between particles and matter. It has been shown, through significant benchmarking against physical experiments and other software, to be remarkably accurate at simulating interactions between particles and matter. Currently, Geant4 is being used on world-wide projects such as ATLAS, CMS, Muon g-2, and ILC, largely due to being accurate, open-source, and written in a modern language. This openness and modernity is striking when compared to other Monte-Carlo simulation toolkits such as the Fortran toolkit MCNP (Monte-Carlo N-Particle code), which is restricted in acquisition and use by the US government. Despite barriers in the use of MCNP and having been written in an antiquated language, MCNP is still considered industry-standard for many fields, including radiation shielding. This paper details the development and validation of a radiation shielding simulation framework in Geant4 aimed at flexibility and ease of simulations with the goal of replacing MCNP scripts.

43 PARTICLE ACCELERATORS↗
DOE OSTI2019

Validation of the AltRAM Physics Models for use with Compressed Natural Gas

The Alternative Fuels Risk Assessment Models (A1tRAM) toolkit combines Quantitative Risk Assessment (QRA) with simulations of unignited dispersion, ignited turbulent diffusion flames, and indoor accumulation with delayed ignition of fuels. The models of the physical phenomena need to be validated for each of the fuels in the toolkit. This report shows the validation for methane which is being used as a surrogate for natural gas. For the unignited dispersion model, seven previously published experiments from credible sources were used to validate. The validation looked at gas concentrations with respect to the distance from the release point. Four of these were underexpanded jets (i.e. release velocity equal to or greater than local speed of sound) and the other three subsonic releases. The methane plume model in AltRAM matched both varieties well, with higher accuracy for the underexpanded releases. For the jet flame model, we compared the heat flux and thermal radiation data reported from five separate turbulent jet flame experiments to the quantities calculated by A1tRAM. Four of the five datasets were for underexpanded diffusion jets flames. While the results still match well enough to give a good estimate of what is occurring, the error is higher than what was seen with the plume model. For the underexpanded flames A1tRAM provided reasonable approximations, which would lead to conservative risk assessments. Some modeling errors can be attributed to environmental effects (i.e. wind) since most large scale flame experiments are conducted outdoors. A1tRAM has been shown to be a reasonably accurate tool for calculating the concentration or flame properties of natural gas releases. Improvements could still be made for the plume of subsonic releases and radiative heat fluxes to reduce the conservative nature of these predictions. These models can provide valuable information for the risk assessment of natural gas infrastructure.

03 NATURAL GAS↗
NASA NTRS1976

Flare build-up study; Proceedings of the Workshop, Falmouth, Mass., September 8-11, 1975

The papers deal with problems which might be common to solar flares and earth's magnetosphere, problems associated with the initial phases of the flare phenomenon, the acceleration processes that seem to occur in flares and the magnetosphere, as well as the buildup and storage of flare energy in magnetic-field structures. Topics include the active role of magnetic fields in providing flare energy, current-sheet models of solar flares, the role of plasma turbulence in flare development, similarities and differences between magnetospheric substorms and solar flares, observations of magnetic merging in earth's magnetotail during magnetospheric substorms, evidence for magnetic-energy storage in coronal active regions, the possible role of transition-zone instabilities in preflare energy buildup, and flare energy storage and deposition. Other papers discuss energy release through the interaction of coronal magnetic fields, photospheric electric currents as a source of flare energy, magnetic-energy buildup in the solar atmosphere, magnetic and velocity fields in an active region, flare onset at meter wavelengths, laboratory experiments on field-line reconnection, key problems in auroral flare processes, and the solar-physics Shuttle/Spacelab program. Individual items are announced in this issue.

Svestka, Z.↗
NASA NTRS1993

Resolving the iron K line in Cygnus X-2 - An observation with BBXRT

The Astro-1 Space Shuttle payload's Broad Band X-ray telescope has been used to obtain high-quality, moderate-resolution spectroscopy of Cygnus X-2 which allow the resolving of the physical width of the 6.7 keV Fe K-alpha feature with a factor-of-4 energy resolution improvement over past experiments. Three possible sites are noted for the Fe K-alpha emission: the accretion disk, its corona, and the source itself. It is judged that reflection from the accretion disk can generate a line of the observed energy, width, and equivalent width, provided that the disk surface is highly ionized.

Smale, A. P.↗