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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 1,693 records · Page 94
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Magnetohydrodynamic stability of magnetars in the ultrastrong field regime – II. The crust

ABSTRACT We study the stability of Hall magnetohydrodynamic with strong magnetic fields in which Landau quantization of electrons is important. We find that the strong-field Hall modes can be destabilized by the dependence of the differential magnetic susceptibility on magnetic field strength. This hydrodynamic instability, thermodynamic in origin and stabilized by magnetic domain formation, is studied using linear perturbation theory. It is found to have typical growth time of order ≲103 yr, with the growth time decreasing as a function of wavelength of the perturbation. The instability is self-limiting, turning off following a period of local field growth by a few per cent of the initial value. Finite temperature is also shown to limit the instability, with sufficiently high temperatures eliminating it altogether. Alfvén waves can show similar unstable behaviour on shorter time-scales. We find that Ohmic heating due to the large fields developed via the instability and magnetic domain formation is not large enough to account for observed magnetar surface temperatures. However, Ohmic heating is enhanced by the oscillatory differential magnetic susceptibility of Landau-quantized electrons, which could be important to magnetothermal simulations of neutron star crusts.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Diagnosis of 3D magnetic field and mode composition in MHD turbulence with Y -parameter

ABSTRACT Magnetic fields are crucial in numerous astrophysical processes within the interstellar medium (ISM). However, the detailed determination of magnetic field geometry is notoriously challenging. Based on the modern magnetohydrodynamic (MHD) turbulence theory, we introduce a novel statistical technique, the ‘Y-parameter’, to decipher the magnetic field inclination in the ISM and identify dominant turbulence modes. The Y-parameter, calculated as the ratio of anisotropies of different Stokes parameter combinations, displays contrasting trends with the mean-field inclination angle in Alfvénic and compressible turbulence modes. A Y-parameter value around 1.5 ± 0.5 provide a statistical boundary to determine the dominant MHD turbulence modes. We have discovered specific correlations between the Y-parameter value and the inclination angle that unveil the dominant turbulence mode. This methodology, when applied to future radio polarization surveys such as LOFAR and SKA, promises to significantly enhance our knowledge of 3D magnetic field in the ISM and improve our understanding of interstellar turbulence.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

Plasma instabilities dominate radioactive transients magnetic fields: the self-confinement of leptons in Type Ia and core-collapse supernovae, and kilonovae

The light curves of radioactive transients, such as supernovae and kilonovae, are powered by the decay of radioisotopes, which release high-energy leptons through $\beta ^+$ and $\beta ^-$ decays. These leptons deposit energy into the expanding ejecta. As the ejecta density decreases during expansion, the plasma becomes collisionless, with particle motion governed by electromagnetic forces. In such environments, strong or turbulent magnetic fields are thought to confine particles, though the origin of these fields and the confinement mechanism have remained unclear. Using fully kinetic particle-in-cell (PIC) simulations, we demonstrate that plasma instabilities can naturally confine high-energy leptons. These leptons generate magnetic fields through plasma streaming instabilities, even in the absence of pre-existing fields. The self-generated magnetic fields slow lepton diffusion, enabling confinement, and transferring energy to thermal electrons and ions. Our results naturally explain the positron trapping inferred from late-time observations of thermonuclear and core-collapse supernovae. Furthermore, they suggest potential implications for electron dynamics in the ejecta of kilonovae. We also estimate synchrotron radio luminosities from positrons for Type Ia supernovae and find that such emission could only be detectable with next-generation radio observatories from a Galactic or local-group supernova in an environment without any circumstellar material.

instabilities↗
DOE OSTI2021

Strong-field physics in three-dimensional topological insulators

We investigate theoretically the strong-field regime of light-matter interactions in the topological-insulator class of quantum materials. In particular, we focus on the process of nonperturbative high-order harmonic generation from the paradigmatic three-dimensional topological insulator bismuth selenide (Bi 2 Se 3 ) subjected to intense midinfrared laser fields. We analyze the contributions from the spin-orbit-coupled bulk states and the topological surface bands separately and reveal a major difference in how their harmonic yields depend on the ellipticity of the laser field. Furthermore, bulk harmonics show a monotonic decrease in their yield as the ellipticity increases, in a manner reminiscent of high harmonic generation in gaseous media. However, the surface contribution exhibits a highly nontrivial dependence, culminating with a maximum for circularly polarized fields. We attribute the observed anomalous behavior to (i) the enhanced amplitude and the circular pattern of the interband dipole and the Berry connections in the vicinity of the Dirac point and (ii) the influence of the higher-order, hexagonal warping terms in the Hamiltonian, which are responsible for the hexagonal deformation of the energy surface at higher momenta. The latter are associated directly with spin-orbit-coupling parameters. Our results thus establish the sensitivity of strong-field-driven high harmonic emission to the topology of the band structure as well as to the manifestations of spin-orbit interaction.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2022

Bosonic field digitization for quantum computers

Quantum simulation of quantum field theory is a flagship application of quantum computers that promises to deliver capabilities beyond classical computing. The realization of quantum advantage will require methods that can accurately predict error scaling as a function of the resolution and parameters of the model and that can be implemented efficiently on quantum hardware. In this paper, we address the representation of lattice bosonic fields in a discretized field amplitude basis, develop methods to predict error scaling, and present efficient qubit implementation strategies. A low-energy subspace of the bosonic Hilbert space, defined by a boson occupation number cutoff, can be represented with exponentially good accuracy by a low-energy subspace of a finite-size Hilbert space. The finite representation construction and the associated errors are directly related to the accuracy of the Nyquist-Shannon sampling and the finite Fourier transforms of the boson number states in the field and the conjugate-field bases. We analyze the relation between the boson mass, the discretization parameters used for wave function sampling, and the finite representation size. Numerical simulations of small size Φ 4 problems demonstrate that the boson mass optimizing the sampling of the ground state wave function is a good approximation to the optimal boson mass yielding the minimum low-energy subspace size. However, we find that accurate sampling of general wave functions does not necessarily result in accurate representation. Finally, we develop methods for validating and adjusting the discretization parameters to achieve more accurate simulations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Scissors modes of a Bose-Einstein condensate in a synthetic magnetic field

We study the scissors modes of a harmonically trapped Bose-Einstein condensate under the influence of a synthetic magnetic field, which induces rigid rotational components in the velocity field. Our investigation reveals that the scissors mode, excited in the plane perpendicular to the synthetic magnetic field, becomes coupled to the quadrupole modes of the condensate, giving rise to typical beating effects. Moreover, the two scissors modes excited in the vertical planes are also coupled together by the synthetic magnetic field, resulting in intriguing gyroscope dynamics. Our analytical results, derived from a spinor hydrodynamic theory, are further validated through numerical simulations of the three-dimensional Gross-Pitaevskii equation. These predictions for the condensates subject to a synthetic magnetic field are experimentally accessible with current cold-atom setups and hold promise for potential applications in quantum sensing.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2020

Experimental demonstration and analysis of random field effects in ferromagnet/antiferromagnet bilayers

More than 30 years ago, Malozemoff [Phys. Rev. B 35, 3679 (1987)] hypothesized that exchange interaction at the interface between a ferromagnet (F) and an antiferromagnet (AF) can act as an effective random field, which can profoundly affect the magnetic properties of the system. However, until now this hypothesis has not been directly experimentally tested. We utilize magnetoelectronic measurements to analyze the effective exchange fields at permalloy/CoO interface. Our results cannot be explained in terms of quasiuniform effective exchange fields but are in agreement with the random-field hypothesis of Malozemoff. Finally, the presented approach opens a new route for the quantitative analysis of effective exchange fields and anisotropies in magnetic heterostructures for memory, sensing and computing applications.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Critical fields of superconductors with magnetic impurities

The upper critical field H c2 , the field H c3 for nucleation of the surface superconductivity, and the thermodynamic field H c are evaluated within the weak-coupling theory for the isotropic s-wave case with arbitrary transport, and pair-breaking scattering. In this study, we find that, for the standard geometry of a half-space sample in a magnetic field parallel to the surface, the ratio $\mathscr{R}$=H c3 /H c2 is within the window 1.55≲$\mathscr{R}$≲2.34 , regardless of temperature or the scattering type. While the nonmagnetic impurities tend to flatten the $\mathscr{R}$($\mathrm{T}$) variation, magnetic scattering merely shifts the maximum of $\mathscr{R}$($\mathrm{T}$) to lower temperatures. Surprisingly, while reducing the transition temperature, magnetic scattering has a milder impact on $\mathscr{R}$ than nonmagnetic scattering. The surface superconductivity is quite robust; in fact, the ratio $\mathscr{R}$≈1.7 even in the gapless state. We used Eilenberger's energy functional to evaluate the condensation energy F c and the thermodynamic critical field H c for any temperature and scattering parameters. By comparing H c2 and H c , we find that, unlike transport scattering, the pair-breaking pushes materials toward type-I behavior. Furthermore, we find a peculiar behavior of F c as a function of the pair-breaking scattering parameter at the low-$\mathrm{T}$ transition from gapped to gapless phases, which has recently been associated with the topological transition in the superconducting density of states.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Perturbative stability of non-Abelian electric field solutions

We consider SU(2) gauge theory with a scalar field in the fundamental representation. The model is known to contain electric field solutions sourced by the scalar field that are distinct from embedded Maxwell electric fields. We examine the perturbative stability of the solution and identify a region of parameter space where the solution is stable. In the regime where the scalar field has a negative mass squared, the solution has two branches, and we identify an instability in one of the branches.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2022

Quadratic Zeeman effect in hydrogen at 2–3 MG magnetic fields

The Zeeman effect is used for measurement of magnetic fields in astrophysical and laboratory plasmas. Magnetic fields in atmospheres of magnetic white dwarf stars are in the range 40 kG–1 GG. The quadratic Zeeman effect results in the additional split and shift of lines for magnetic fields >2 MG. Hydrogen Balmer lines were studied in magnetic fields delivered by a 1 MA pulse power generator. The magnetic field was generated by rod loads 0.8–1 mm in diameter. A droplet of CH oil on the load center was the source of hydrogen. A low ionized oil layer was backlit by blackbody emission from the rod with a temperature of 0.5–0.6 eV. Zeeman splitting of H-alpha and H-beta absorption lines were with a grating spectrometer. A spectral shift of the central component of the triplet indicated the quadratic Zeeman effect in hydrogen lines.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2022

A wide-field micro-computed tomography detector: micron resolution at half-centimetre scale

Ideal three-dimensional imaging of complex samples made up of micron-scale structures extending over mm to cm, such as biological tissues, requires both wide field of view and high resolution. For existing optics and detectors used for micro-CT (computed tomography) imaging, sub-micron pixel resolution can only be achieved for fields of view of <2 mm. This article presents a unique detector system with a 6 mm field-of-view image circle and 0.5 µm pixel size that can be used in micro-CT units utilizing both synchrotron and commercial X-ray sources. A resolution-test pattern with linear microstructures and whole adult Daphnia magna were imaged at beamline 8.3.2 of the Berkeley Advanced Light Source. Volumes of 10000 × 10000 × 7096 isotropic 0.5 µm voxels were reconstructed over a 5.0 mm × 3.5 mm field of view. Measurements in the projection domain confirmed a 0.90 µm measured spatial resolution that is largely Nyquist-limited. This unprecedented combination of field of view and resolution dramatically reduces the need for sectional scans and computational stitching for large samples, ultimately offering the means to elucidate changes in tissue and cellular morphology in the context of larger, whole, intact model organisms and specimens. This system is also anticipated to benefit micro-CT imaging in materials science, microelectronics, agricultural science and biomedical engineering.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Spatiotemporal Modeling of Real World Backsheets Field Survey Data: Hierarchical (Multilevel) Generalized Additive Models

Assessing photovoltaic module backsheet durability is critical to increasing module lifetime. Laboratory-based accelerating testing has recently failed to predict large scale failures of widely adopted polymeric materials. Additionally, there is a growing concern on characterizing the non-uniformity of field exposure. Therefore, data from field surveys are critical to assess the performance of component lifetimes. Using a documented field survey protocol, 19 field surveys were conducted. The focus of this survey strategy is to investigate spatial continuity in degradation modes. By combining field survey data with real-time satellite weather data, stressor / response models have been trained. Generalized additive Models (GAM) model was created to predict the value of degradation based on measured predictors. Two different GAM constructions were testing using different implementations of basis splines. The model includes variables on the environmental stressors of the system and the location of each measurement in the PV mounting structure. The incorporation of hierarchical structure into the models allowed for material specific degradation rates, while maintaining the assumption of a global trend. The model performed well with an adjusted R2 of 0.975 for yellowness index prediction.

backsheet↗
DOE OSTI2019

New Approach and Test Facility for High Field Accelerator Magnets R&D

This paper presents a new approach for developing and demonstrating high field magnet technology based on a magnet and test facility developed specifically for it. The traditional approach for carrying out high field magnet R&D has been building a new magnet to demonstrate a new design, new material or new technology. However, building a high field magnet is time consuming and expensive. To overcome this limitation, Brookhaven National Laboratory (BNL) built and successfully tested a 10 T Nb 3 Sn dipole DCC017 with large enough open or clear space (31 mm wide and 338 mm high) so that a pair of racetrack coils could be inserted into this opening without disassembling the magnet. The motivation be-hind this design was to facilitate a magnet R&D program where the new coils (with a large range in width and height accommodated) would reside in a high field region in direct contact with the existing coils (just as other magnet coils) and thus become an integral part of the magnet. We summarize the approach, the magnet, the test facility, past experiences, current and future test plans and planned up-grade. Here, the magnet facility is now available to service the needs of the wider community for testing cable and insert coils in a back-ground field of up to 10 T.

43 PARTICLE ACCELERATORS↗
DOE OSTI2023

A Flexible Field Mapping System for Accelerator Magnets

Magnetic field mapping is a fundamental magnetic measurement method that typically uses Hall and NMR sensors. In magnet measurement facilities, such systems are likely used in various configurations suitable for a specific task at hand. To address this diversity, the authors developed a flexible field mapping system capable of being configured and tailored to each particular measurement case. Further, the system needs to address the variability introduced by differences in sensors and their readout systems, probe positioning systems, power supply systems, and required mapping geometry (mapping space and grid, measurement steps and sequences). Although the discussed field mapping systems range from a self-propelled multi-sensor mapper of a large detector magnet to a single 3D Hall sensor system to scan a small permanent magnet, they were all built with the same core mapping system. The variability present in field mapping systems, the measurement system architecture addressing this variability, as well as examples of several field mapping systems built in this architecture are presented.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Ni 3 Si 2 nanowires for efficient electron field emission and limitations of the Fowler–Nordheim model

This article reports on top-down nanofabricated Ni 3 Si 2 nanowires and tests of their electron field emission capabilities. Here, the results include low turn-on electric field, E ON , moderate work function, Φ, and the field enhancement factor, β, customizable through nanofabrication. The article also reports on the issues ahead in the field of nanowires-based electron mission, as there are quantitative limitations of the applicability of the Fowler–Nordheim model, which will become increasingly apparent as we continue to optimize the field emission of electrons. To this end, we suggest adding the studies of surface-to-volume ratio effects of the nanowires as another standard for comparison in order to lead to the input form of the density of states as quantum effects becoming more prominent.

42 ENGINEERING↗
DOE OSTI2026

Data for Yield from Iowa’s first commercial miscanthus fields: implications of spatial variability for productivity and sustainability beyond research plots

This dataset contains biomass yield measurements and associated vegetation index data collected from commercial Miscanthus × giganteus fields in eastern Iowa during the 2022–2023 growing seasons. The data support the analyses presented in the article: “Yield From Iowa's First Commercial Miscanthus Fields: Implications of Spatial Variability for Productivity and Sustainability Beyond Research Plots.” We collected 105 ground-truth biomass samples from four mature commercial fields (>4 years old) covering 92.81 ha. Samples were taken from 3 m² quadrats that were hand-harvested in alignment with commercial harvest timing. Stem biomass (excluding leaves) was weighed, moisture-corrected, and converted to dry-matter yield expressed in Mg DM ha⁻¹. Sampling locations were selected to capture spatial variability visible in aerial imagery and were recorded using RTK GPS. Each biomass observation was paired with vegetation indices derived from high-resolution PlanetScope satellite imagery (3 m resolution). Images were acquired throughout the growing season, and indices were calculated to evaluate their ability to predict end-of-season biomass yield. Statistical and machine learning approaches were used to identify key predictors, and a linear regression model based on end-of-July Green Normalized Difference Vegetation Index (GNDVI) was developed and evaluated. This repository includes the data used in that modeling workflow. Management practices, economic data, full imagery time series, and additional methodological details are described in the associated publication and are not included here. The dataset consists of three comma-separated value (CSV) files: 1. Combine_Groundtruth_Yield_VI_22_23.csv This file contains ground-truth biomass yield measurements and associated key vegetation index values collected during the 2022 and 2023 growing seasons. Rows: 105 observations Columns: Year — Year of observation (2022 or 2023) Field — Field location identifier Sample_number — Unique sample identifier GNDVI_End_Jul — Green Normalized Difference Vegetation Index calculated at end of July GNDVI_End_Aug — Green Normalized Difference Vegetation Index calculated at end of August NDRE_End_Aug — Normalized Difference Red Edge index calculated at end of August Biomass_Stem_Yield_MgDM/ha — Measured stem biomass yield (megagrams dry matter per hectare) 2. trainData_GNDVI.csv This file contains the subset of observations used to train the predictive relationship between July GNDVI and biomass yield. Rows: 76 observations Columns: Unnamed: 0 — Row index retained from the original data processing workflow GNDVI_End_Jul — GNDVI at end of July Stem_Yield_MgDM/ha — Observed stem biomass yield (Mg DM ha⁻¹) 3. testData_GNDVI.csv This file contains the test dataset used to evaluate model performance. Rows: 29 observations Columns: Unnamed: 0 — Row index retained from the original data processing workflow GNDVI_End_Jul — GNDVI at end of July Predicted_Yield_MgDM/ha — Model-predicted stem biomass yield (Mg DM ha⁻¹) Observed_Yield_MgDM/ha — Measured stem biomass yield (Mg DM ha⁻¹)

Potential yield, yield gap, in-field management, y↗
DOE OSTI2022

Research in Quantum Field Theory, Cosmology, and String Theory

This project covered research in theoretical high energy physics at Brandeis University by PI Albion Lawrence and Co-PIs Matthew Headrick and Howard Schnitzer. The work of Albion Lawrence covered quantum field theoretic models of cosmic inflation and of quintessence-type dark energy, consistent with constraints on quantum gravity; the dynamics of open quantum systems, with an eye towards applications to holography; and the application of quantum information theory – particularly measures of quantum entanglement – to quantum field theories and quantum gravity. The work of Matthew Headrick covered the intersection of quantum information theory and quantum gravity, with a focus on the holographic encoding of quantum information theoretic concepts such as entanglement and computational complexity in field theory. Headrick also achieved significant technical results in closed string field theory. The work of Howard Schnitzer covered the computation of quantum information theoretic quantities in quantum field theories.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Field Test Best Practices

This report can be used as a resource for advice on every stage of field research in residential buildings. It can be used as a reference document to find descriptions of specific types of common measurements and tricks of the trade, or as a primer on home field research providing a basic education on the subject. The report begins with descriptions of field experiment design and discusses advantages and disadvantages of different types of data acquisition systems. The bulk of the paper describes the common measurements needed in residential field work, the hardware options for making the measurements, and field notes on with tips, tricks, and cautions.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗