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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 811 records · Page 45
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Bias in the effective field theory of large scale structures

We study how to describe collapsed objects, such as galaxies, in the context of the Effective Field Theory of Large Scale Structures. The overdensity of galaxies at a given location and time is determined by the initial tidal tensor, velocity gradients and spatial derivatives of the regions of dark matter that, during the evolution of the universe, ended up at that given location. Similarly to what was recently done for dark matter, we show how this Lagrangian space description can be recovered by upgrading simpler Eulerian calculations. We describe the Eulerian theory. We show that it is perturbatively local in space, but non-local in time, and we explain the observational consequences of this fact. We give an argument for why to a certain degree of accuracy the theory can be considered as quasi time-local and explain what the operator structure is in this case. Furthermore, we describe renormalization of the bias coefficients so that, after this and after upgrading the Eulerian calculation to a Lagrangian one, the perturbative series for galaxies correlation functions results in a manifestly convergent expansion in powers of k/k NL and k/k M , where k is the wavenumber of interest, k NL is the wavenumber associated to the non-linear scale, and k M is the comoving wavenumber enclosing the mass of a galaxy.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

Impact of error fields and error field correction on heat fluxes in SPARC

Using a single toroidal array of coils to reduce the m,n = 2,1 resonant error field (EF) produced by the misalignment of the axisymmetric coils in SPARC can result in the enhancement of the local divertor heat fluxes. Managing high divertor heat fluxes (q ∥ $\simeq$ 10 GW m -2 ) poses a challenge for compact tokamak devices such as SPARC. The presence of non-axisymmetric magnetic field perturbations adds complexity to the problem by generating intricate 3D edge magnetic topologies that alter the heat flux distributions on the target plates. The aim of this work is to investigate the impact of the EF correction (EFC) on the heat fluxes at the divertor plates in SPARC. The MHD code M3DC1 has been used to simulate the 3D magnetic perturbations generated by the shift and tilt of several axisymmetric coils within specified tolerances, as well as from the array of EFC coils located at the midplane. Using a heuristic model that extends the concept of an axisymmetric heat flux layer to 3D plasmas, the resultant heat flux distributions is derived from magnetic footprints calculated with the MAFOT code. The results show that the EFC could either decrease or further enhance the local heat flux when used to correct the m,n = 2,1 resonant EF to enhance the core plasma performance.

3D fields↗
DOE OSTI2022

Design of the American Wake Experiment (AWAKEN) field campaign

The American WAKE experimeNt (AWAKEN) is a multi-institutional collaborative field campaign, starting in March 2022, that will gather an unprecedented data set including both atmospheric observations and wind plant operational data. This comprehensive data set will be used to characterize the wind plant performance and turbine loading in different operational and atmospheric conditions and validate the use of different wind plant control strategies and simulation frameworks. An extensive field campaign like AWAKEN requires proper coordination and long-term planning to be successful. In this paper, we review the major activities planned during AWAKEN to provide information for current and future project partners. Specifically, we provide information about the project sites, their planned instruments, and how these will relate to the scientific objectives of the overall AWAKEN project.

17 WIND ENERGY↗
DOE OSTI2023

Overview of recent observations and simulations from the American WAKE experimeNt (AWAKEN) field campaign

The American WAKE experimeNt (AWAKEN) is a large-scale field campaign focused on gathering new detailed observations of wind farm–atmosphere interactions for improved understanding of wind farm physics and overall performance. The field campaign, centered around five wind farms in northern Oklahoma, began in September 2022 and will run through at least October 2023. This paper summarizes some of the initial observations and simulations performed as part of the AWAKEN project.

17 WIND ENERGY↗
DOE OSTI2011

TIME DELAY OF CASCADE RADIATION FOR TeV BLAZARS AND THE MEASUREMENT OF THE INTERGALACTIC MAGNETIC FIELD

Recent claims that the strength B{sub IGMF} of the intergalactic magnetic field (IGMF) is {approx}> 10{sup -15} G are based on upper limits to the expected cascade flux in the GeV band produced by blazar TeV photons absorbed by the extragalactic background light. This limit depends on an assumption that the mean blazar TeV flux remains constant on timescales {approx}> 2(B{sub IGMF}/10{sup -18}G){sup 2}/(E/10 GeV){sup 2} yr for an IGMF coherence length {approx}1 Mpc, where E is the measured photon energy. Restricting TeV activity of 1ES 0229+200 to {approx}3-4 years during which the source has been observed leads to a more robust lower limit of B{sub IGMF} {approx}> 10{sup -18} G, which can be larger by an order of magnitude if the intrinsic source flux above {approx}5-10 TeV from 1ES 0229+200 is strong.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2010

Exploration of strong-field multiphoton double ionization, rescattering, and electron angular distribution of He atoms in intense long-wavelength laser fields: The coupled coherent-state approach

We extend the coupled coherent-state (CCS) approach to simulate the strong-field ionization of helium atoms at long wavelengths. This approach uses a basis of trajectories guided by frozen Gaussian coherent states, sampled from a Monte Carlo distribution, as the initial states of the quantum time-dependent Schroedinger equations. The CCS trajectories move over averaged potentials, which can remove the Columbic singularities exactly. The low-energy structure is predicted by our CCS calculation and a ''rescattering'' event is clearly identified in the higher-energy regime. In addition, the nonsequential double ionization is also explored and the rescattering event can be identified as the major mechanism. Finally, we also study the electron angular distribution of helium. It is found that the maximum angle between the electron and electric field directions becomes smaller with increase in the laser intensity and wavelength.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2011

Photoelectron imaging of autoionizing states of xenon: Effect of external electric fields

Velocity map photoelectron imaging was used to study the photoelectron angular distributions of autoionizing Stark states of atomic xenon excited just below the Xe{sup +} {sup 2} P{sub 1/2}{sup o} threshold at fields ranging from 50 to 700 V/cm. Two-color, two-photon resonant, three-photon excitation via the 6p{sup '}[1/2]{sub 0} level was used to probe the region of interest. The wavelength scans show a similar evolution of structure to that observed in single-photon excitation [Ernst et al., Phys. Rev. A 37, 4172 (1988)]. The photoelectron angular distributions following autoionization of the Stark states provide information on the decay of excited states in electron fields. In the present experiments, the large autoionization width of the ({sup 2} P{sub 1/2}{sup o})nd[3/2]{sub 1}{sup o} series dominates the decay processes, and thus controls the angular distributions. However, the angular distributions of the Stark states also indicate the presence of other decay channels contributing to the decay of these states.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2015

Electric-field-induced strain effects on the magnetization of a Pr 0.67 Sr 0.33 MnO 3 film

The electric-field control of magnetic properties of Pr 0.67 Sr 0.33 MnO 3 (PSMO) film on piezoelectric Pb(Mg 1/3 Nb 2/3 )O 3 -PbTiO 3 (PMNT) substrate was investigated. The piezoelectric response of the PMNT substrate to the electric field produced strain that was coupled to the PSMO film. The in-plane compressive (tensile) strain increased (decreased) the magnetization. The change of magnetic moment was associated with the Mn ions. First principle simulations showed that the strain-induced electronic redistribution of the two e g orbitals (3d z 2 and 3d x 2 -y 2 ) of Mn ions was responsible for the change of magnetic moment. This work demonstrates that the magnetoelectric effect in manganite/piezoelectric hetero-structures originates from the change in eg orbital occupancy of Mn ions induced by strain rather than the interfacial effect.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Effective field theory interactions for liquid argon target in DarkSide-50 experiment

We reanalize data collected with the DarkSide-50 experiment and recently used to set limits on the spin-independent interaction rate of weakly interacting massive particles (WIMPs) on argon nuclei with an effective field theory framework. The dataset corresponds to a total (16660 ± 270) kg d exposure using a target of low-radioactivity argon extracted from underground sources. We obtain upper limits on the effective couplings of the 12 leading operators in the nonrelativistic systematic expansion. For each effective coupling we set constraints on WIMP-nucleon cross sections, setting upper limits between 2.4×10-45 cm2 and 2.3×10-42 cm2 (8.9 ×10-45 cm2 and 6.0 ×10-42 cm2) for WIMPs of mass of 100 GeV/c2 (1000 GeV/c2) at 90% confidence level.

Agnes, P↗
DOE OSTI2012

A cascade of magnetic field induced spin transitions in LaCoO{<_3}.

We present magnetization and magnetostriction studies of LaCoO{sub 3} in magnetic fields approaching 100 T. In contrast with expectations from single-ion models, the data reveal two distinct first-order transitions and well-defined magnetization plateaus. The magnetization at the higher plateau is only about half the saturation value expected for spin-1 Co{sup 3+} ions. These findings strongly suggest collective behavior induced by interactions between different electronic configurations of Co{sup 3+} ions. We propose a model that predicts crystalline spin textures and a cascade of four magnetic phase transitions at high fields, of which the first two account for the experimental data.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2022

Silicon Heterojunction Field Performance

The market share of silicon heterojunction (SHJ) modules are expected to increase in the following years. The presentation discusses field performance of SHJ and compares it to other high-efficiency modules. In-depth materials characterization is used to understand the origins of degradation in these type of modules.

ENGINEERING,SOLAR ENERGY↗