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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 757 records · Page 42
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

High efficiency rare-earth emitter for thermophotovoltaic applications

In this work, we propose a rare-earth-based ceramic thermal emitter design that can boost thermophotovoltaic (TPV) efficiencies significantly without cold-side filters at a temperature of 1573 K (1300 °C). The proposed emitter enhances a naturally occurring rare earth transition using quality-factor matching, with a quarter-wave stack as a highly reflective back mirror, while suppressing parasitic losses via exponential chirping of a multilayer reflector transmitting only at short wavelengths. This allows the emissivity to approach the blackbody limit for wavelengths overlapping with the absorption peak of the rare-earth material, while effectively reducing the losses associated with undesirable long-wavelength emission. We obtain TPV efficiencies of 34% using this layered design, which only requires modest index contrast, making it particularly amenable to fabrication via a wide variety of techniques, including sputtering, spin-coating, and plasma-enhanced chemical vapor deposition.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

Equilibrium reconstruction of DIII-D plasmas using predictive modeling of the pressure profile

New workflows have been developed for predictive modeling of magnetohydrodynamic (MHD) equilibrium in tokamak plasmas. The goal of this work is to predict the MHD equilibrium in tokamak discharges without having measurements of the kinetic profiles. The workflows include a cold start tool, which constructs all the profiles and power flows needed by transport codes; a Grad–Shafranov equilibrium solver; and various codes for the sources and sinks. For validation purposes, a database of DIII-D tokamak discharges has been constructed that is comprised of scans in the plasma current, toroidal magnetic field, and triangularity. Initial efforts focused on developing a workflow utilizing an empirically derived pressure model tuned to DIII-D discharges with monotonic safety factor profiles. This workflow shows good agreement with experimental kinetic equilibrium calculations, but is limited in that it is a single fluid (equal ion and electron temperatures) model and lacks H-mode pedestal predictions. The best agreement with the H-mode database is obtained using a theory-based workflow utilizing pressure profile predictions from a coupled TGLF turbulent transport and EPED pedestal models together with external magnetics and Motional Stark Effect (MSE) data to construct the equilibrium. Here, we obtain an average root mean square error of 5.1% in the safety factor profile when comparing the predicted and experimental kinetic equilibrium. We also find good agreement with the plasma stored energy, internal inductance, and pressure profiles. Including MSE data in the theory-based workflow results in noticeably improved agreement with the q-profiles in high triangularity discharges in comparison with the results obtained with magnetic data only. The predictive equilibrium workflow is expected to have wide applications in experimental planning, between-shot analysis, and reactor studies.

Kinsey, J. E. (ORCID:0000000193347473)↗
DOE OSTI2022

Neutron backscatter edges as a diagnostic of burn propagation

High gain in hotspot-ignition inertial confinement fusion (ICF) implosions requires the propagation of thermonuclear burn from a central hotspot to the surrounding cold dense fuel. As ICF experiments enter the burning plasma regime, diagnostic signatures of burn propagation must be identified. In previous work [A. J. Crilly et al., Phys. Plasmas 27(1), 012701 (2020)], it has been shown that the spectral shape of the neutron backscatter edges is sensitive to the dense fuel hydrodynamic conditions. The backscatter edges are prominent features in the ICF neutron spectrum produced by the 180° scattering of primary deuterium–tritium fusion neutrons from ions. In this work, synthetic neutron spectra from radiation-hydrodynamics simulations of burning ICF implosions are used to assess the backscatter edge analysis in a propagating burn regime. Significant changes to the edge's spectral shape are observed as the degree of burn increases, and a simplified analysis is developed to infer scatter-averaged fluid velocity and temperature. The backscatter analysis offers direct measurement of the increased dense fuel temperatures that result from burn propagation.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2026

Helicon edge heating in Proto-MPEX: Azimuthally resolved RF modeling

The Material Plasma Exposure eXperiment (MPEX) is a linear device under construction at ORNL. MPEX employs a variety of heating systems, including a helicon antenna, which is the subject of this work. Lacking a resonant absorption mechanism, as tokamaks have, modeling the RF power absorption in such antennas requires detailed consideration of cold collisional physics. Previous modeling of the heating in this antenna was done exclusively in 2D, assuming axisymmetry and a single azimuthal mode number m = 1⁠. In this study, we introduce a fully 3D model. By including the full 3D physics, with its self-consistent geometry-imposed azimuthal spectrum, we are able to reproduce the experimentally observed transition from edge heating to core heating.

Tierens, Wouter [Oak Ridge National Laboratory (OR↗
DOE OSTI2016

The Faber–Jackson relation and Fundamental Plane from halo abundance matching

The Fundamental Plane (FP) describes the relation between the stellar mass, size, and velocity dispersion of elliptical galaxies; the Faber–Jackson relation (FJR) is its projection on to {mass, velocity} space. In this work, we re-deploy and expand the framework of Desmond & Wechsler to ask whether abundance matching-based Λ-cold dark matter models which have shown success in matching the spatial distribution of galaxies are also capable of explaining key properties of the FJR and FP, including their scatter. Within our framework, agreement with the normalization of the FJR requires haloes to expand in response to disc formation. We find that the tilt of the FP may be explained by a combination of the observed non-homology in galaxy structure and the variation in mass-to-light ratio produced by abundance matching with a universal initial mass function, provided that the anisotropy of stellar motions is taken into account. However, the predicted scatter around the FP is considerably increased by situating galaxies in cosmologically motivated haloes due to the variations in halo properties at fixed stellar mass and appears to exceed that of the data. Finally, this implies that additional correlations between galaxy and halo variables may be required to fully reconcile these models with elliptical galaxy scaling relations.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

Cosmic dipoles from large-scale structure surveys

Large-scale structure surveys can be used to measure the dipole in the cosmic microwave background (CMB), in the luminosity distances inferred from type-Ia supernova observations, and in the spatial distribution of galaxies and quasars. The measurements of these cosmic dipoles appear to be mutually inconsistent, even though they are expected to indicate the common observer velocity. This observational tension may represent a significant challenge to the standard model of cosmology. Here, in this work, we study in detail what contributes to the cosmic dipoles from CMB, supernova, and galaxy survey in the standard Λ cold dark matter (Λ⁢ CDM) model, though our theoretical model can be applied beyond the standard model. While measurements of the cosmic dipoles yield the relative velocities between the source samples and the observer velocity, the motion of the observer is the dominant contribution in the conformal Newtonian gauge, and the intrinsic velocities of the samples fall steeply with increasing redshift of the sources. Hence the cosmic dipoles of CMB, type-Ia supernovae, and galaxies should be aligned but can have different amplitudes. We also clarify several misconceptions that are commonly found in the literature.

cosmic microwave background↗
DOE OSTI2020

Microscopic study of the coupled-wire construction and plausible realization in spin-dependent optical lattices

Coupled-wire constructions offer particularly simple and powerful models to capture the essence of strongly correlated topological phases of matter. They often rely on effective theories valid in the low-energy and strong-coupling limits, which impose severe constraints on the physical systems where they could be realized. In this work, we investigate the microscopic relevance of a class of coupled-wire models and their possible experimental realization in cold-atom experiments. We connect with earlier results and prove the emergence of fractional quantum Hall states in the limit of strong interwire tunneling. Contrary to previous studies relying on renormalization group arguments, our microscopic approach exposes the connection between coupled-wire constructions and model wave functions in continuum Landau levels. Then, we use exact-diagonalization methods to investigate the appearance of these fractional quantum Hall states in more realistic settings. We examine the parameter regimes where these strongly correlated phases arise, and provide a way to detect their appearance in cold-atom experiments through standard time-of-flight measurements. Motivated by this experimental probe, we finally propose a realization of our model with cold atoms in spin-dependent optical lattices. Our estimates show that the previous fractional quantum Hall phases lie within experimentally accessible parameter regimes, giving a viable route toward their experimental study.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Multiphase tin equation of state using density functional theory

In this work, we perform density functional theory (DFT) calculations of five solid phases and the liquid phase of tin. The calculations include cold curves of the five solid phases, phonon calculations in the quasiharmonic approximation over a range of volumes for each solid phase, and DFT-based molecular dynamics (DFT-MD) simulations of the liquid phase, including those of the melt curve using the Z method. Using the DFT results, we construct a tabular multiphase sesame equation of state for tin, referred to as sesame 2162. Comparisons to experimental data are made and show a high level of agreement in isobaric data, isothermal data, shock data, and phase boundary measurements, including measurements of the melt curve. The 2162 EOS will be useful for hydrodynamics simulations and has been designed with an eye toward hydrodynamics simulations that incorporate materials strength models and allow for modeling of the kinetics of phase transitions.

3-dimensional systems↗
DOE OSTI2017

Mapping Vinyl Cyanide and Other Nitriles in Titan’s Atmosphere Using ALMA

Vinyl cyanide (C{sub 2}H{sub 3}CN) is theorized to form in Titan’s atmosphere via high-altitude photochemistry and is of interest regarding the astrobiology of cold planetary surfaces due to its predicted ability to form cell membrane-like structures (azotosomes) in liquid methane. In this work, we follow up on the initial spectroscopic detection of C{sub 2}H{sub 3}CN on Titan by Palmer et al. with the detection of three new C{sub 2}H{sub 3}CN rotational emission lines at submillimeter frequencies. These new, high-resolution detections have allowed for the first spatial distribution mapping of C{sub 2}H{sub 3}CN on Titan. We present simultaneous observations of C{sub 2}H{sub 5}CN, HC{sub 3}N, and CH{sub 3}CN emission, and obtain the first (tentative) detection of C{sub 3}H{sub 8} (propane) at radio wavelengths. We present disk-averaged vertical abundance profiles, two-dimensional spatial maps, and latitudinal flux profiles for the observed nitriles. Similarly to HC{sub 3}N and C{sub 2}H{sub 5}CN, which are theorized to be short-lived in Titan’s atmosphere, C{sub 2}H{sub 3}CN is most abundant over the southern (winter) pole, whereas the longer-lived CH{sub 3}CN is more concentrated in the north. This abundance pattern is consistent with the combined effects of high-altitude photochemical production, poleward advection, and the subsequent reversal of Titan’s atmospheric circulation system following the recent transition from northern to southern winter. We confirm that C{sub 2}H{sub 3}CN and C{sub 2}H{sub 5}CN are most abundant at altitudes above 200 km. Using a 300 km step model, the average abundance of C{sub 2}H{sub 3}CN is found to be 3.03 ± 0.29 ppb, with a C{sub 2}H{sub 5}CN/C{sub 2}H{sub 3}CN abundance ratio of 2.43 ± 0.26. Our HC{sub 3}N and CH{sub 3}CN spectra can be accurately modeled using abundance gradients above the tropopause, with fractional scale-heights of 2.05 ± 0.16 and 1.63 ± 0.02, respectively.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Effects of the σ{sup ∗} and ϕ Mesons on the Properties of Massive Protoneutron Stars

The properties of massive neutron stars and protoneutron stars are studied in this work in the framework of relativistic mean-field theory. For certain choices of coupling parameters, a two-solar mass cold neutron star is obtained in the presence of hyperons, taking into account the influence of σ{sup ∗} and ϕ mesons. The model for the coupling parameters is then extrapolated to study the effects of σ{sup ∗} and ϕ mesons on the properties of massive protoneutron stars in different evolutionary stages. The coupling constants are determined by two different methods, and their corresponding influence on the equation of state, mass, radius, and temperature is studied. The effect of the strange mesons is different at different evolution stages of the neutron star. The properties of a protoneutron star corresponding to the mass of PSR J0348+0432 are also presented.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1995

Demonstration of solar echoes using the Air Force OTH-B radar

From the late 50s to early 70s, attempts were made by at least two different groups to obtain information on physical conditions in the corona by means of active radar soundings. While echoes from the Sun were unquestionably detected. difficulties in their interpretation led to inconclusive results. A major hindrance to these efforts was the limited understanding of the day-to-day structure of the corona then available (e.g., pioneering work in solar wind studies were just underway. and coronal holes had not yet been discovered). With the end of the Cold War, the very large over-the-horizon (OTH) radars operated by the Air Force have been opened up to basic science research through the end of the fiscal year. In light of advances made in coronal physics and in signal processing technology since these early experiments were undertaken. access to the state-of-the art OTH-B radar offers a rare opportunity to gauge anew the scientific potential for radar sounding of the Sun. In principle, it should be possible to obtain useful data on plasma densities and motions over a range of heights in the corona near 0.5R(solar mass) above the solar surface We report here the preliminary findings from a sequence of observations taken over the course of a solar rotation.

Pizzo, V. J.↗
NASA NTRS2011

Statistical Analysis of Thermal Analysis Margin

NASA Goddard Space Flight Center requires that each project demonstrate a minimum of 5 C margin between temperature predictions and hot and cold flight operational limits. The bounding temperature predictions include worst-case environment and thermal optical properties. The purpose of this work is to: assess how current missions are performing against their pre-launch bounding temperature predictions and suggest any possible changes to the thermal analysis margin rules

Garrison, Matthew B.↗
NASA NTRS2017

Mapping Vinyl Cyanide and Other Nitriles in Titan's Atmosphere Using ALMA

Vinyl cyanide (C2H3CN) is theorized to form in Titan's atmosphere via high-altitude photochemistry and is of interest regarding the astrobiology of cold planetary surfaces due to its predicted ability to form cell membrane-like structures (azotosomes) in liquid methane. In this work, we follow up on the initial spectroscopic detection of C2H3CN on Titan by Palmer et al. with the detection of three new C2H3CN rotational emission lines at submillimeter frequencies. These new, high-resolution detections have allowed for the first spatial distribution mapping of C2H3CN on Titan. We present simultaneous observations of C2H5CN, HC3N, and CH3CN emission, and obtain the first (tentative) detection of C3H8 (propane) at radio wavelengths. We present disk-averaged vertical abundance profiles, two-dimensional spatial maps, and latitudinal flux profiles for the observed nitriles. Similarly to HC3N and C2H5CN, which are theorized to be short-lived in Titan's atmosphere, C2H3CN is most abundant over the southern (winter) pole, whereas the longer-lived CH3CN is more concentrated in the north. This abundance pattern is consistent with the combined effects of high-altitude photochemical production, poleward advection, and the subsequent reversal of Titan's atmospheric circulation system following the recent transition from northern to southern winter. We confirm that C2H3CN and C2H5CN are most abundant at altitudes above 200 km. Using a 300 km step model, the average abundance of C2H3CN is found to be 3.03 +/- 0.29ppb, with a C2H5CN/C2H3CN abundance ratio of 2.43 +/- 0.26. Our HC3N and CH3CN spectra can be accurately modeled using abundance gradients above the tropopause, with fractional scale-heights of 2.05 +/- 0.16 and 1.63 +/- 0.02, respectively.

Lai, J. C.-Y.↗
NASA NTRS2021

Hydrocarbon Cold-Flow Simulation of LOX/LH2 Rocket Aerodynamics

In FY19, this project developed a test method which employed heated ethane in the physical simulation of rocket plume aerodynamics. Based on this work, EUS partnered with significant leveraged funding. A portable, self-contained test bed was also fabricated to support validation of the new method. In FY20, this project focused on the formal validation of ethane’s performance as an aerodynamic simulant as well as the development of the analytical and hardware infrastructure required to carry out that task. The test bed was activated, a series of heated-ethane tests on one or more rocket/diffuser configurations were conducted, and characterizations of the performance of the ethane simulation compared to hot-fire were performed. A series of 127 tests were conducted on 13 aerodynamic configurations to evaluate ethane’s performance as a simulant. It was found that the new methodology can reproduce rocket plume flow fields with +/- 0.5% pressure error at ~3% physical scale. The result is a cost-per-test reduction of ~99% compared to the hot-fire subscale testing typically used to obtain equivalent data. Some initial efforts have taken place, and future efforts are being planned with LaRC supersonic retro propulsion and MSFC SLS aerodynamics teams, which are interested in using the ethane system to wind-tunnel test human-rated Mars lander retrorockets and SLS Booster. Details of the prototypical experiments were published as NASA TM 2020-5009122,and have been presented in JANNAF Virtual Conference paper, "New Developments in Retro propulsion Testing for Mars Entry, Descent and Landing".

Daniel Jones↗
DOE OSTI2011

Nonlinear oscillations and waves in an arbitrary mass ratio cold plasma

It is well known that nonlinear standing oscillations in an arbitrary mass ratio cold plasma always phase mix away. However, there exist nonlinear electron-ion traveling wave solutions, which do not exhibit phase mixing because they have zero ponderomotive force. The existence of these waves has been demonstrated using a perturbation method. Moreover, it is shown that cold plasma BGK waves [Albritton et al., Nucl. Fusion 15, 1199 (1975)] phase mix away if ions are allowed to move and the scaling of phase mixing is found to be different from earlier work [Sengupta et al., Phys. Rev. Lett. 82, 1867 (1999)]. Phase mixing of these waves has been further verified in 1-D particle in cell simulation.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2018

Characterization of Bypass Fluid Flow in an Active Magnetic Regenerative Liqueer

Active magnetic regenerators (AMR) with second order magnetocaloric materials operating below the Curie temperature have a unique property where the magnetized specific heat is lower than the demagnetized specific heat. The associated thermal mass unbalance allows a fraction of heat transfer fluid in the cold heat exchanger to bypass the magnetized regenerator. This cold bypassed fluid can precool a process stream as it returns to the hot side, thereby increasing the efficiency of liquefaction and reducing the cost of liquid cryogens. While researchers have been aware of this phenomenon for decades, experimental performance improvements from bypass fluid flow have yet to be reported in open literature. In the present work, the net cooling power of an active magnetic regenerative liquefier is investigated as a function of the bypass ow fraction. Experiments are performed at a fixed temperature span that yield a 25% improvement in net cooling power, affirming the potential of bypass cooling power.

active magnetic regenerator, hydrogen, liquefacati↗
DOE OSTI2017

Simulating the SuperCDMS Dark Matter Detector Response and Readout

Dark matter is one of the remaining great mysteries of modern physics. Cosmological and astrophysical evidence hints strongly at a new particle, or set of particles, unknown to the Standard Model, comprising some 80% of all of the matter in the universe. SuperCDMS is one of the world-leading direct-detection experiments attempting to directly measure interactions between dark and regular matter. SuperCDMS uses solid state crystalline detectors in a nearly-zero background environment to attempt to measure the particle properties of dark matter. The detectors themselves, however, are quite complex; and a very detailed understanding of the microscopic physics is helpful in analyzing the very rare events that occur within them. Furthermore, better understanding and modeling of the detectors can aid in the design and optimization of future iterations of the experiment. The SuperCDMS detectors are well-understood in ideal cases. However, an accurate understanding of the detector response to outlier events or under non-ideal conditions is important for a low-statistics experiment. This work describes the design and implementation of a low temperature condensed matter physics simulation library built on top of the popular Geant4 particle tracking framework. The library, named \Geant4 Condensed Matter Physics" or G4CMP, introduces several solid state concepts to the Geant4 framework such as crystal lattices, phonon quasiparticles, non-scalar elective masses, and implements several physics processes relevant to cryogenic temperature crystals. In addition to the physics library, which is intended for general use, this work also describes a full Monte Carlo simulation package for the SuperCDMS iZIP detectors which utilizes G4CMP at its core and also fully simulates the detector readout sensors. The document will begin with the canonical motivations for the cold dark matter hypothesis, followed by a description of the SuperCDMS experiment. It will then describe the microscopic physics inside of the SuperCDMS detectors, as well as details on their implementation in G4CMP. The full detector simulation with corresponding sensor readout will follow, along with plans for future work; including both scientific studies and improvements, as well as computational improvements and added efficiencies.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Radiative cooling of solar absorbers using a visibly transparent photonic crystal thermal blackbody

Significance The coldness of the universe is an enormous but strikingly underexploited thermodynamic resource. Its direct utilization on Earth therefore represents an important frontier for renewable energy research. In many applications, including solar cells and outdoor structures, the absorption of sunlight is intrinsic either from operational or aesthetic considerations, but the resulting heating by sunlight is undesirable. Here we experimentally demonstrate a thermal photonic scheme that can cool these structures by thermal radiation to outer space, while preserving the structures’ solar absorption. Our work shows, for the first time to our knowledge, that radiative cooling can be used in combination with the utilization of sunlight, and opens new possibilities for using the coldness of the universe to improve the performance of terrestrial energy systems.

42 ENGINEERING↗