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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 937 records · Page 52
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Scalar QED as a toy model for higher-order effects in classical gravitational scattering

Quantum Electrodynamics (QED) serves as a useful toy model for classical observables in gravitational two-body systems with reduced complexity due to the linearity of QED. We investigate scattering observables in scalar QED at the sixth order in the charges (two-loop order) in a classical regime analogous to the post-Minkowskian expansion in General Relativity. We employ modern scattering amplitude tools and extract classical observables by both eikonal methods and the formalism of Kosower, Maybee, and O’Connell (KMOC). In addition, we provide a simplified approach to extracting the radial action beyond the conservative sector.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2025

Measurement of light-by-light scattering and the Breit-Wheeler process, and search for axion-like particles in ultraperipheral PbPb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV

Measurements of light-by-light scattering (LbL, γγ → γγ) and the Breit-Wheeler process (BW, γγ → e + e − ) are reported in ultraperipheral PbPb collisions at a centre-of-mass energy per nucleon pair of 5.02 TeV. The data sample, corresponding to an integrated luminosity of 1.7 nb −1 , was collected by the CMS experiment at the CERN LHC in 2018. Events with an exclusively produced γγ or e + e − pair with invariant masses m γγ,ee > 5 GeV, along with other fiducial criteria, are selected. The measured BW fiducial production cross section, σ fid (γγ → e + e − ) = 263.5 ± 1.8(stat) ± 17.8(syst) μb, as well as the differential distributions for various kinematic observables, are in agreement with leading-order quantum electrodynamics predictions complemented with final-state photon radiation. The measured differential BW cross sections allow discrimination between different theoretical descriptions of the photon flux of the lead ion. In the LbL final state, 26 exclusive diphoton candidate events are observed compared with 12.0 ± 2.9 expected for the background. Combined with previous results, the observed significance of the LbL signal with respect to the background-only hypothesis is above five standard deviations. The measured fiducial LbL scattering cross section, σ fid (γγ → γγ) = 107 ± 24(stat) ± 13(syst) nb, is in agreement with next- to-leading-order predictions. Limits on the production of axion-like particles coupled to photons are set over the mass range 5–100 GeV, including the most stringent limits to date in the range of 5–10 GeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Bootstrapping conformal QED 3 and deconfined quantum critical point

We bootstrap the deconfined quantum critical point (DQCP) and 3D Quantum Electrodynamics (QED 3 ) coupled to N f flavors of two-component Dirac fermions. We show the lattice and perturbative results on the SO(5) symmetric DQCP are excluded by the bootstrap bounds with an assumption that the lowest singlet scalar is irrelevant. Remarkably, we discover a new family of kinks in the 3D SO(N) vector bootstrap bounds with N ⩾ 6. We demonstrate coincidences between SU(N f ) adjoint and $SO (N^2_f-1$) vector bootstrap bounds due to a novel algebraic relation between the crossing equations. By introducing gap assumptions breaking the $SO (N^2_f-1$) symmetry, the SU(N f ) adjoint bootstrap bounds with large N f converge to the 1/N f perturbative results of QED 3 . Our results provide strong evidence that the SO(5) DQCP is not continuous and the critical flavor number of QED 3 is slightly above 2: $N^*_f\in$ (2,4). Bootstrap results near $N^*_f$ are well consistent with the merger and annihilation mechanism for the loss of conformality in QED 3 .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Free-standing gold elliptical nanoantenna with tunable wavelength in near-infrared region for enhanced Raman spectroscopy

The purpose of this work is to present a surface-enhanced Raman scattering (SERS) amplifying antenna for the possible usage in the near-infrared region. Instead of the visible-light range amplifying antenna such as a bowtie, the finite-difference time-domain (FDTD) simulation results indicate that elliptical antenna could provide large electromagnetic field enhancement at near-infrared wavelength by combining the free-standing enhancement property with large aspect ratios of the ellipse geometry. The simulation results consist with the enhancement factors characterized by SERS measurements at the excited wavelength of 785 nm for different aspect ratios and periodicities. In addition to the redshift of the resonance wavelength as the aspect ratio of ellipse increases, the free-standing structure modifies the resonance behavior and the dielectric environment of antenna by elevating the elliptical disk from the substrate. To interpret the simulation results, the analytical solution of resonance wavelength for ellipsoid dimmer is derived based on Lorentz–Mie theory, and comparisons are made between the analytical solution and simulation results. The quasi-static analytical solution provides a way to characterize the resonance behavior of two ellipsoid particles as a function of the gap distance, aspect ratio, and dielectric environment. In conclusion, the electrodynamic analysis for the periodic structure was performed in our FDTD simulations.

47 OTHER INSTRUMENTATION↗
DOE OSTI2018

Magnetic Properties of La-Doped ZnO(0001)–Zn Polar Surface with and without Vacancies: a First-Principle Study

The effects of La doping with and without vacancies on the magnetism of a ZnO(0001)–Zn polar surface were studied using the generalized gradient approximation + U (GGA + U) method of density functional theory to determine the magnetism source of La-doped ZnO. Results revealed that La doping with O vacancy did not cause ZnO ferromagnetism, but La-doped ZnO with Zn vacancy was ferromagnetic. The net magnetic moment was primarily related to the unpaired electron amount of the O 2p state and slightly modified by orbital and anomalous magnetic moments. The anomalous magnetic moment originated from the radiating magnetism moment via quantum electrodynamics and was confirmed to exist via theoretical calculations of magnetism. Formation energy showed that La doping easily generated Zn vacancies in ZnO, but magnetic quenching occurred when the ratio of La ions to Zn vacancies was 2:1. The unpaired O 2p electrons induced by Zn vacancies were the magnetism source of La-doped ZnO. Moreover, the Curie temperature of La-doped ZnO with Zn vacancy reached room temperature. Results showed that the ZnO(0001)–Zn polar surface can be utilized as the surface of ZnO-based diluted magnetic semiconductors because of its unipolarity.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

Enhancing Surface Finish of Additively Manufactured 316L Stainless Steel with Pulse/Pulse Reverse Electropolishing

To improve the reliable integration of additively manufactured (AM) metal components, there is an urgent need for surface finishing methods capable of processing rough, “as-printed” surfaces. Here, we present a new and scalable electropolishing (EP) technique for use on AM 316L stainless steel (SS) that is capable of achieving a surface roughness equivalent to a machined finish, with arithmetic mean heights (S a ) as low as 1.0 µm. This technique utilizes the sequential application of a new, NaCl/H 2 O pulse/pulse reverse (P/PR) EP step along with a conventional DC (direct current) EP step, where P/PR expands the capability of EP by removing roughness features > 1 µm, which has been previously unattainable with DC EP alone without substantial material removal. This is achieved by independently varying pulse parameters, such as pulse width and height, allowing more control over electrodynamic processes at the part-electrolyte interface. Additionally, P/PR EP resulted in higher smoothing efficiency, where a higher degree of smoothing was achieved with less material removal when compared with conventional DC EP alone. This minimizes unwanted change in geometry from excessive metal dissolution.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Focus on Advancing High Performance Mass Spectrometry, Honoring Dr. Richard D. Smith, Recipient of the 2013 Award for a Distinguished Contribution in Mass Spectrometry

This special focus issue of the Journal of the American Society for Mass Spectrometry celebrates the accomplishments of Dr. Richard D. Smith, the recipient of the 2013ASMS Award for a Distinguished Contribution in Mass Spectrometry, and who serves as a Battelle Fellow, Chief Scientist in the Biological Sciences Division, and Director of Proteomics Research at Pacific Northwest National Laboratory (PNNL) in Richland, WA. The award is for his development of the electrodynamic ion funnel.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

A Simplified Method for Predicting Shaker Voltage in IMMATs

Impedance Matched Multi-Axis Tests (IMMATs) can replicate in-service vibration induced stress more accurately than single axis shaker table tests as they can better match a part’s operational boundary conditions and excite it in multiple degrees of freedom simultaneously. Here, the shakers used in IMMATs are less powerful than shaker tables, so shaker force limits can be exceeded during tests if they are not placed adequately for the desired environment. The ability to predict shaker voltage and force before performing a test is, therefore, helpful in selecting shaker locations so that their limits are not exceeded. In this study, electrodynamic shakers were modeled as discrete electromechanical systems, and the shaker parameters were chosen to match experimentally obtained acceleration/voltage frequency response functions (FRFs). These models were coupled to a finite element model of the device under test (DUT) via dynamic substructuring, and the substructured model was demonstrated to accurately predict shaker voltage as well as the error in reproducing the environment at multiple accelerometer locations. A simple method called the FRF Multiplication method, in which the FRF of the substructured system is approximated as the product of two separate FRFs of the shaker and DUT respectively, was proposed and applied to the same system, yielding similar voltage and error predictions to those obtained using substructuring. Simple case studies were presented to explore the applicability of the proposed method, and it was demonstrated to have similar accuracy to the substructuring method in a range of cases. Additionally, we showed that while it was not possible to derive a unique model of the shakers from acceleration/voltage FRFs alone, the models that could be obtained were sufficient to predict test error almost perfectly and shaker voltage with less than 40 percent error.

42 ENGINEERING↗
DOE OSTI2014

Relativistic CI calculations of spectroscopic data for the 2p{sup 6} and 2p{sup 5}3l configurations in Ne-like ions between Mg III and Kr XXVII

Energies, E1, M1, E2, M2 transition rates, oscillator strengths, and lifetimes from relativistic configuration interaction calculations are reported for the states of the 2p{sup 6}, 2p{sup 5}3s, 2p{sup 5}3p, and 2p{sup 5}3d, configurations in all Ne-like ions between Mg III and Kr XXVII. Core–valence and core–core correlation effects are accounted for through single and double excitations to increasing sets of active orbitals. The Breit interaction and leading quantum electrodynamic effects are included as perturbations. The results are compared with experiments and other recent benchmark calculations. In Mg III, Al IV, Si V, P VI, S VII, and Ar IX, for which experimental energies are known to high accuracy, the mean error in the calculated energies is only 0.011%.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2014

Wavelengths, transition probabilities, and oscillator strengths for M-shell transitions in Co-, Ni-, Cu-, Zn-, Ga-, Ge-, and Se-like Au ions

Wavelengths, transition probabilities, and oscillator strengths have been calculated for M-shell electric dipole transitions in Co-, Ni-, Cu-, Zn-, Ga-, Ge-, and Se-like Au ions. The fully relativistic multiconfiguration Dirac–Fock method, taking quantum electrodynamical effects and the Breit correction into account, was used in the calculations. Calculated energy levels of M-shell excited states for Cu-, Zn-, Ga-, Ge-, and Se-like Au ions from the method were compared with available theoretical and experimental results, and good agreement with them was achieved.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2017

Energy levels, oscillator strengths, line strengths, and transition probabilities in Si-like ions of La XLIII, Er LIV, Tm LV, and Yb LVI

Detailed calculations using the multi-configuration Dirac–Fock (MCDF) method are carried out for the lowest 64 fine-structure levels of the 3s{sup 2}3p{sup 2}, 3s{sup 2}3p3d, 3s3p{sup 3}, 3s3p{sup 2}3d, 3s{sup 2}3d{sup 2}, and 3p{sup 4} configurations in Si-like ions of La XLIII, Er LIV, Tm LV, and Yb LVI. Energies, oscillator strengths, wavelengths, line strengths, and radiative electric dipole transition rates are given for all ions. A parallel calculation using the many-body perturbation theory (MBPT) method is also carried out to assess the present energy levels accuracy. Comparisons are performed between these two sets of energy levels, as well as with other available results, showing that they are in good agreement with each other within 0.5%. These high accuracy results can be used to the modeling and the interpretation of astrophysical objects and fusion plasmas. - Highlights: • Energy levels and E1 transition rates of Si-like ions are presented. • Breit interaction and Quantum Electrodynamics effects are discussed. • Present results should be useful in the astrophysical application and plasma modeling.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2013

Decomposition of the total momentum in a linear dielectric into field and matter components

The long-standing resolution of the Abraham–Minkowski electromagnetic momentum controversy is predicated on a decomposition of the total momentum of a closed continuum electrodynamic system into separate field and matter components. Using a microscopic model of a simple linear dielectric, we derive Lagrangian equations of motion for the electric dipoles and show that the dielectric can be treated as a collection of stationary simple harmonic oscillators that are driven by the electric field and produce a polarization field in response. The macroscopic energy and momentum are defined in terms of the electric, magnetic, and polarization fields that travel through the dielectric together as a pulse of electromagnetic radiation. We conclude that both the macroscopic total energy and the macroscopic total momentum are entirely electromagnetic in nature for a simple linear dielectric in the absence of significant reflections. -- Highlights: •The total momentum in a dielectric is identified by conservation principles. •The total momentum in a dielectric cannot be decomposed into field and matter parts. •A component of momentum in a dielectric is due to motion of the polarization field.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

FDTD: Solving 1+1D delay PDE in parallel

We present a proof of concept for solving a 1+1D complex-valued, delay partial differential equation (PDE) that emerges in the study of waveguide quantum electrodynamics (QED) by adapting the finite-difference time-domain (FDTD) method. The delay term is spatially non-local, rendering conventional approaches such as the method of lines inapplicable. Here, we show that by properly designing the grid and by supplying the (partial) exact solution as the boundary condition, the delay PDE can be numerically solved. In addition, we demonstrate that while the delay imposes strong data dependency, multi-thread parallelization can nevertheless be applied to such a problem. Our code provides a numerically exact solution to the time-dependent multi-photon scattering problem in waveguide QED.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Two-step perfectly matched layer for arbitrary-order pseudo-spectral analytical time-domain methods

Numerical simulation of an electrodynamic system in empty space requires the implementation of open boundary conditions (BC) to terminate the solution of Maxwell’s equations on the boundaries of the computational domain. The Perfectly Matched Layer (PML) has become the method of choice for open BC with wave equations, as it is straightforward and relatively easy to implement, and offers very efficient and user-adjustable absorption rates. PMLs are most often employed with the Finite-Difference Time-Domain (FDTD) algorithm, which in its most common implementation offers second-order accuracy in space and time on Cartesian grids. Yet, simulations (including some class of electromagnetic Particle-In-Cell simulations) that require higher precision may resort to higher-order Maxwell solvers employing extended finite-difference stencils, or even to pseudo-spectral Maxwell solvers, for which a general, versatile and efficient formulation of the PML has been missing so far. Here we propose a novel “two-step” formulation of the PML that is simple, very versatile and can be used as is with any Maxwell solver. In particular, it is applicable to a large class of Maxwell solvers including the arbitrary-order Pseudo-Spectral Analytical Time-Domain (PSATD) solver, which offers arbitrarily low numerical dispersion when increasing solver order and becomes dispersion-free at infinite order. Analysis and numerical simulations demonstrate that the new formulation is as efficient as the standard PML formulation, both for the FDTD and the PSATD implementations.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2020

Dynamic load balancing with enhanced shared-memory parallelism for particle-in-cell codes

Furthering our understanding of many of today’s interesting problems in plasma physics – including plasma based acceleration and magnetic reconnection with pair production due to quantum electrodynamic effects – requires large-scale kinetic simulations using particle-in-cell (PIC) codes. However, these simulations are extremely demanding, requiring that contemporary PIC codes be designed to efficiently use a new fleet of exascale computing architectures. To this end, the key issue of parallel load balance across computational nodes must be addressed. We discuss the implementation of dynamic load balancing by dividing the simulation space into many small, self-contained regions or ‘‘tiles,’’ along with shared-memory (e.g., OpenMP) parallelism both over many tiles and within single tiles. The load balancing algorithm can be used with three different topologies, including two space-filling curves. Here, we tested this implementation in the code Osiris and show low overhead and improved scalability with OpenMP thread number on simulations with both uniform load and severe load imbalance. Compared to other load-balancing techniques, our algorithm gives order-of-magnitude improvement in parallel scalability for simulations with severe load imbalance issues.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2023

EZ: An efficient, charge conserving current deposition algorithm for electromagnetic particle-in-cell simulations

Here, we present EZ, a novel current deposition algorithm for particle-in-cell (PIC) simulations. EZ calculates the current density on the electromagnetic grid due to macro-particle motion within a time step by solving the continuity equation of electrodynamics. Being a charge conserving hybridization of Esirkepov's method and ZigZag, we refer to it as “EZ” as shorthand for “Esirkepov meets ZigZag”. Simulations of a warm, relativistic plasma with PIConGPU show that EZ achieves the same level of charge conservation as the commonly used method by Esirkepov, yet reaches higher performance for macro-particle assignment-functions up to third-order. In addition to a detailed description of the functioning of EZ, reasons for the expected and observed performance increase are given, and guidelines for its implementation aiming at highest performance on GPUs are provided.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

What Students Think About (Nuclear) Radiation – Before and After Fukushima

Preparing successful science lessons is very demanding. One important aspect a teacher has to consider is the students' previous knowledge about the specific topic. This is why research about students' preconceptions has been, and continues to be, a major field in science education research. Following a constructivistic approach [R. Duit et al., International handbook of research on conceptual change, p. 629 (2008)], helping students learn is only possible if teachers know about students' ideas beforehand. Studies about students' conceptions regarding the major topics in physics education (e.g. mechanics, electrodynamics, optics, thermodynamics), are numerous and well-documented. The topic radiation, however, has seen very little empirical research about students' ideas and misconceptions. Some research was conducted after the events of Chernobyl [P. Lijnse et al., International Journal of Science Education 12, 67 (1990); B. Verplanken, Environment and Behavior 21, 7 (1989)] and provided interesting insight into some of the students' preconceptions about radiation. In order to contribute empirical findings to this field of research, our workgroup has been investigating the conceptions students have about the topic radiation for several years [S. Neumann et al., Journal of Science Education and Technology 21, 826 (2012)]. We used children's drawings and conducted short follow-up interviews with students (9 – 12 years old) and more detailed interviews with 15-year-old students. Both studies were originally done before the events in Fukushima and replicated a year later. We not only asked students about their general associations and emotions regarding the term radiation, but also examined the students' risk perceptions of different types of radiation. Through the use of open-ended questions we were able to examine students' conceptions about different types of radiation (including nuclear) that could be a hindrance to student learning. Our results show that students' associations with the term radiation are almost exclusively related to nuclear radiation. Their emotions concerning the word radiation are predominately negative, and the idea that radiation is something to be avoided is widespread among students. Since most students were not familiar with the idea of naturally occurring nuclear radiation, it does not seem surprising that a lot of them generally described radiation as something artificial and man-made. Also, none of the students interviewed mentioned applications of nuclear radiation in medicine or technology (besides its use in nuclear power plants). All of these results have shown to be even more prevalent in the interview session that was conducted after the tragic events in Fukushima in 2011. In this article, we will also include suggestions for improving the teaching of the topic radiation in school.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

On the canonical formulation of gauge field theories and Poincaré transformations

We address the Hamiltonian formulation of classical gauge field theories while putting forward results some of which are not entirely new, though they do not appear to be well known. We refer in particular to the fact that neither the canonical energy momentum vector ( P μ ) nor the gauge invariant energy momentum vector ( P inv μ ) do generate space-time translations of the gauge field by means of the Poisson brackets: In a general gauge, one has to consider the so-called kinematical energy momentum vector and, in a specific gauge (like the radiation gauge in electrodynamics), one has to consider the Dirac brackets rather than the Poisson brackets. Similar arguments apply to rotations and to Lorentz boosts and are of direct relevance to the “nucleon spin crisis” since the spin of the proton involves a contribution which is due to the angular momentum vector of gluons and thereby requires a proper treatment of the latter. We conclude with some comments on the relationships between the different approaches to quantization (canonical quantization based on the classical Hamiltonian formulation, Gupta-Bleuler, path integrals, BRST, covariant canonical approaches).

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗