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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 1,081 records · Page 60
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Gauge-free electromagnetic gyrokinetic theory

A new gauge-free electromagnetic gyrokinetic theory is developed, in which the gyrocenter equations of motion and the gyrocenter phase-space transformation are expressed in terms of the perturbed electromagnetic fields, instead of the usual perturbed potentials. Gyrocenter polarization and magnetization are derived explicitly from the gyrocenter Hamiltonian, up to first order in the gyrocenter perturbation expansion. In conclusion, expressions for the sources in Maxwell's equations are derived in a form that is suitable for simulation studies, as well as kinetic-gyrokinetic hybrid modeling.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2025

No evidence of a reduction in the dipole polarisability at shell closures

Photoabsorption reactions have a long and productive history as probes of the response of nuclei to electromagnetic fields. In recent years, there has been a suggestion that the dipole polarisability may be reduced at shell closures, potentially due to the reduced level density. In the current paper, more recent photoabsorption strengths are reanalysed including nuclei on closed proton shells to search for a similar reduction. The previously reported reduction is not reproduced. We conclude that the previously observed reduction may be due to incomplete evaluations of the photoabsorption due to missing cross section contributions and experimental artefacts. More experimental data are necessary to draw a firm conclusion about whether shell effects persist into high excitation energies, especially data which can obviate any systematic effects and look at relative photoabsorption strengths between nuclei.

Giant dipole response↗
DOE OSTI2023

Hot QCD phase diagram from holographic Einstein–Maxwell–Dilaton models

In this review, we provide an up-to-date account of quantitative holographic descriptions of the strongly coupled quark-gluon plasma (QGP) produced in heavy-ion collisions, based on the class of gauge-gravity Einstein-Maxwell-Dilaton (EMD) models. Holography is employed to tentatively map the QCD phase diagram at finite temperature onto a dual theory of charged, asymptotically AdS black holes in 5D. With a quantitative focus on the hot QCD phase diagram, the EMD models reviewed are adjusted to describe lattice results for the finite-temperature QCD equation of state, with 2+1 flavors and physical quark masses, at zero chemical potential and vanishing electromagnetic fields. The predictive power of EMD models is tested by quantitatively comparing their predictions for the hot QCD equation of state at nonzero baryon density and the corresponding state-of-the-art lattice QCD results. The shear and bulk viscosities predicted by these EMD models are also compared to the corresponding profiles favored by the latest phenomenological multistage models describing different heavy-ion data. We report preliminary results from a Bayesian analysis which provide systematic evidence that lattice results at finite temperature and zero baryon density strongly constrains the free parameters of EMD models. Remarkably, the set of parameters constrained by lattice results at zero chemical potential produces EMD models in quantitative agreement with lattice QCD results also at finite baryon density. We also review results for equilibrium and transport properties from magnetic EMD models, describing the QGP at finite temperatures and magnetic fields. Lastly, we provide a critical assessment of the main limitations and drawbacks of the holographic models reviewed in the present work, and point out some perspectives we believe are of fundamental importance for future developments.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

Deuterated polyethylene nanowire arrays for high-energy density physics

Abstract The interaction of intense, ultrashort laser pulses with ordered nanostructure arrays offers a path to the efficient creation of ultra-high-energy density (UHED) matter and the generation of high-energy particles with compact lasers. Irradiation of deuterated nanowires arrays results in a near-solid density environment with extremely high temperatures and large electromagnetic fields in which deuterons are accelerated to multi-megaelectronvolt energies, resulting in deuterium–deuterium (D–D) fusion. Here we focus on the method of fabrication and the characteristics of ordered arrays of deuterated polyethylene nanowires. The irradiation of these array targets with femtosecond pulses of relativistic intensity and joule-level energy creates a micro-scale fusion environment that produced $2\times {10}^6$ neutrons per joule, an increase of about 500 times with respect to flat solid CD 2 targets irradiated with the same laser pulses. Irradiation with 8 J laser pulses was measured to generate up to 1.2 × 10 7 D–D fusion neutrons per shot.

Optics↗
DOE OSTI2017

Charged particle dynamics in multiple colliding electromagnetic waves. Survey of random walk, Lévy flights, limit circles, attractors and structurally determinate patterns

The multiple colliding laser pulse concept formulated by Bulanov et al. ( Phys. Rev. Lett ., vol. 104, 2010 b , 220404) is beneficial for achieving an extremely high amplitude of coherent electromagnetic field. Since the topology of electric and magnetic fields of multiple colliding laser pulses oscillating in time is far from trivial and the radiation friction effects are significant in the high field limit, the dynamics of charged particles interacting with the multiple colliding laser pulses demonstrates remarkable features corresponding to random walk trajectories, limit circles, attractors, regular patterns and Lévy flights. Lastly, under extremely high intensity conditions the nonlinear dissipation mechanism stabilizes the particle motion resulting in the charged particle trajectory being located within narrow regions and in the occurrence of a new class of regular patterns made by the particle ensembles.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2017

Finding quantum effects in strong classical potentials

The long-standing challenge to describing charged particle dynamics in strong classical electromagnetic fields is how to incorporate classical radiation, classical radiation reaction and quantized photon emission into a consistent unified framework. The current, semiclassical methods to describe the dynamics of quantum particles in strong classical fields also provide the theoretical framework for fundamental questions in gravity and hadron–hadron collisions, including Hawking radiation, cosmological particle production and thermalization of particles created in heavy-ion collisions. However, as we show, these methods break down for highly relativistic particles propagating in strong fields. They must therefore be improved and adapted for the description of laser–plasma experiments that typically involve the acceleration of electrons. Theory developed from quantum electrodynamics, together with dedicated experimental efforts, offer the best controllable context to establish a robust, experimentally validated foundation for the fundamental theory of quantum effects in strong classical potentials.

Physics↗
DOE OSTI2020

The geometric theory of charge conservation in particle-in-cell simulations

In recent years, several gauge-symmetric particle-in-cell (PIC) methods have been developed whose simulations of particles and electromagnetic fields exactly conserve charge. While it is rightly observed that these methods’ gauge symmetry gives rise to their charge conservation, this causal relationship has generally been asserted via ad hoc derivations of the associated conservation laws. In this work, we develop a comprehensive theoretical grounding for charge conservation in gauge-symmetric Lagrangian and Hamiltonian PIC algorithms. For Lagrangian variational PIC methods, we apply Noether’s second theorem to demonstrate that gauge symmetry gives rise to a local charge conservation law as an off-shell identity. For Hamiltonian splitting methods, we show that the momentum map establishes their charge conservation laws. We define a new class of algorithms – gauge-compatible splitting methods – that exactly preserve the momentum map associated with a Hamiltonian system’s gauge symmetry – even after time discretization. This class of algorithms affords splitting schemes a decided advantage over alternative Hamiltonian integrators. We apply this general technique to design a novel, explicit, symplectic, gauge-compatible splitting PIC method, whose momentum map yields an exact local charge conservation law. Finally, our study clarifies the appropriate initial conditions for such schemes and examines their symplectic reduction.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

Koopman wavefunctions and Clebsch variables in Vlasov–Maxwell kinetic theory

Motivated by recent discussions on the possible role of quantum computation in plasma simulations, here, we present different approaches to Koopman's Hilbert-space formulation of classical mechanics in the context of Vlasov–Maxwell kinetic theory. The celebrated Koopman–von Neumann construction is provided with two different Hamiltonian structures: one is canonical and recovers the usual Clebsch representation of the Vlasov density, the other is non-canonical and appears to overcome certain issues emerging in the canonical formalism. Furthermore, the canonical structure is restored for a variant of the Koopman–von Neumann construction that carries a different phase dynamics. Going back to van Hove's prequantum theory, the corresponding Koopman–van Hove equation provides an alternative Clebsch representation which is then coupled to the electromagnetic fields. Finally, the role of gauge transformations in the new context is discussed in detail.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

py4DSTEM: A Software Package for Four-Dimensional Scanning Transmission Electron Microscopy Data Analysis

Scanning transmission electron microscopy (STEM) allows for imaging, diffraction, and spectroscopy of materials on length scales ranging from microns to atoms. By using a high-speed, direct electron detector, it is now possible to record a full two-dimensional (2D) image of the diffracted electron beam at each probe position, typically a 2D grid of probe positions. These 4D-STEM datasets are rich in information, including signatures of the local structure, orientation, deformation, electromagnetic fields, and other sample-dependent properties. However, extracting this information requires complex analysis pipelines that include data wrangling, calibration, analysis, and visualization, all while maintaining robustness against imaging distortions and artifacts. In this paper, we present py4DSTEM, an analysis toolkit for measuring material properties from 4D-STEM datasets, written in the Python language and released with an open-source license. We describe the algorithmic steps for dataset calibration and various 4D-STEM property measurements in detail and present results from several experimental datasets. We also implement a simple and universal file format appropriate for electron microscopy data in py4DSTEM, which uses the open-source HDF5 standard. We hope this tool will benefit the research community and help improve the standards for data and computational methods in electron microscopy, and we invite the community to contribute to this ongoing project.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2021

Quantum Plasmonic Sensors

The extraordinary sensitivity of plasmonic sensors is well-known in the optics and photonics community. These sensors exploit simultaneously the enhancement and the localization of electromagnetic fields close to the interface between a metal and a dielectric. This enables, for example, the design of integrated biochemical sensors at scales far below the diffraction limit. Despite their practical realization and successful commercialization, the sensitivity and associated precision of plasmonic sensors are starting to reach their fundamental classical limit given by quantum fluctuations of light—known as the shot-noise limit. To improve the sensing performance of these sensors beyond the classical limit, quantum resources are increasingly being employed. This area of research has become known as “quantum plasmonic sensing”, and it has experienced substantial activity in recent years for applications in chemical and biological sensing. This review aims to cover both plasmonic and quantum techniques for sensing, and it shows how they have been merged to enhance the performance of plasmonic sensors beyond traditional methods. We discuss the general framework developed for quantum plasmonic sensing in recent years, covering the basic theory behind the advancements made, and describe the important works that made these advancements. We also describe several key works in detail, highlighting their motivation, the working principles behind them, and their future impact. The intention of the review is to set a foundation for a burgeoning field of research that is currently being explored out of intellectual curiosity and for a wide range of practical applications in biochemistry, medicine, and pharmaceutical research.

47 OTHER INSTRUMENTATION↗
DOE OSTI2022

Microwave Heating-Induced Temperature Gradients in Liquid–Liquid Biphasic Systems

Microwaves (MWs) can enable the electrification and intensification of chemical manufacturing. They have been applied to various unit separations, such as drying, distillation, and extraction, entailing gas–liquid and solid–liquid systems. However, a limited quantitative understanding of MW-heated liquid–liquid biphasic systems related to extraction exists. This work measures the temporal and spatial temperature difference between an aqueous and an organic phase in batch and continuous microfluidic modes. We demonstrate permanent temperature differences between phases over 35 °C and spatiotemporal periodic and quasiperiodic oscillations modulated by the flow patterns. The temperature differences are primarily driven by the faster absorption rate of MW irradiation by the aqueous phase versus the slower heat transfer from the aqueous phase to the organic phase. These are amplified by low specific interfacial area and modifications of the electromagnetic field. We employ a multiphysics model to predict the temperature difference in a batch system. The model is in good agreement with the experiments. We demonstrate a strong effect of input power, dielectric properties of organic solvents, the volume of solvents, and the volume ratio between phases on the temperature difference. A simple analytical model describes the temperature difference and provides design principles. Furthermore, the combined approach offers new insights into the design and optimization of the MW-heated biphasic systems.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Ultrafast Laser Pulse Generation by Mode Locking: MATLAB-Based Demonstrations

Ultrafast laser spectroscopy is a valuable and increasingly accessible technique for studies of rapid chemical reactions. Critical to ultrafast spectroscopy is the concept of mode locking, a technique that enables a fixed phase relationship between laser modes, resulting in laser pulses with very short duration (in the fs or ps range). Despite the increasing importance of ultrafast lasers in chemistry, the introduction of key concepts behind their operation into the undergraduate and graduate chemistry coursework has been limited. To help the incorporation of these topics into chemistry courses, we report here a hands-on activity that helps students develop an intuitive understanding of the factors that impact electromagnetic wave evolution in optical cavities and the process of mode locking. We first provide the theoretical background by introducing cavity modes and contrasting them with well-known propagating electromagnetic waves. We then explore what happens when modes are added and how the relative phase between the modes affects their behavior. In the second section of this report, three teaching modules are provided, along with associated MATLAB codes and animated images, that can be used in the classroom to introduce concepts of cavity modes and mode locking. These teaching modules start by contrasting propagating electromagnetic waves with cavity modes and then illustrate what happens when multiple modes are present in the cavity and how the relative phase between the modes affects the overall electromagnetic field in the cavity.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Vibrational Probe at the Electrochemical Interface: Dependence on Plasmon Coupling and Potential of the Lineshape in Two-Dimensional Infrared Spectroscopy

Two-dimensional infrared spectroscopy of vibrational probes at an electrode surface shows promise for studying the structural dynamics at an active electrochemical interface. This interface is a complex environment where the solution structures in response to the applied potential. A strategy for achieving the necessary monolayer sensitivity is to use a plasmonically active electrode, which enhances the electromagnetic fields that produce the spectroscopic response. Here, in this study, we show how the coupling between the plasmon and the vibrations of the molecular monolayer impacts the FTIR and 2D IR spectroscopy, with an emphasis on the electrochemical potential difference spectra. We show how mixing between the vibrational and plasmonic states gives rise to the distortions that are observed in these measurements. This provides an important step toward 2D IR measurements of vibrational probes at the electrochemical interface as a tool for probing the structural dynamics in the double layer.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Multifunctional Metal–Oxide Nanocomposite Thin Film with Plasmonic Au Nanopillars Embedded in Magnetic La 0.67 Sr 0.33 MnO 3 Matrix

Searching for multifunctional materials with tunable magnetic and optical properties has been a critical task toward the implementation of future integrated optical devices. Vertically aligned nanocomposite (VAN) thin films provide a unique platform for multifunctional material designs. In this work, a new metal–oxide VAN has been designed with plasmonic Au nanopillars embedded in a ferromagnetic La 0.67 Sr 0.33 MnO 3 (LSMO) matrix. Such Au–LSMO nanocomposite presents intriguing plasmon resonance in the visible range and magnetic anisotropy property, which are functionalized by the Au and LSMO phase, respectively. Furthermore, the vertically aligned nanostructure of metal and dielectric oxide results in the hyperbolic property for near-field electromagnetic wave manipulation. Such optical and magnetic response could be further tailored by tuning the composition of Au and LSMO phases.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Huygens’ Metasurfaces Enabled by Magnetic Dipole Resonance Tuning in Split Dielectric Nanoresonators

Dielectric metasurfaces that exploit the different Mie resonances of nanoscale dielectric resonators are a powerful platform for manipulating electromagnetic fields and can provide novel optical behavior. Here in this work, we experimentally demonstrate independent tuning of the magnetic dipole resonances relative to the electric dipole resonances of split dielectric resonators (SDRs). By increasing the split dimension, we observe a blue shift of the magnetic dipole resonance toward the electric dipole resonance. Therefore, SDRs provide the ability to directly control the interaction between the two dipole resonances within the same resonator. For example, we achieve the first Kerker condition by spectrally overlapping the electric and magnetic dipole resonances and observe significantly suppressed backward scattering. Moreover, we show that a single SDR can be used as an optical nanoantenna that provides strong unidirectional emission from an electric dipole source.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Self-Assembly of Large Gold Nanoparticles for Surface-Enhanced Raman Spectroscopy

Performance of portable technologies from mobile phones to electric vehicles is currently limited by the energy density and lifetime of lithium batteries. Expanding the limits of battery technology requires in situ detection of trace components at electrode–electrolyte interphases. Surface-enhance Raman spectroscopy could satisfy this need if a robust and reproducible substrate were available. Gold nanoparticles (Au NPs) larger than 20 nm diameter are expected to greatly enhance Raman intensity if they can be assembled into ordered monolayers. A three-phase self-assembly method is presented that successfully results in ordered Au NP monolayers for particle diameters ranging from 13 to 90 nm. The monolayer structure and Raman enhancement factors (EFs) are reported for a model analyte, rhodamine, as well as the best performing polymer electrolyte salt, lithium bis(trifluoromethane)sulfonimide. Experimental EFs for the most part correlate with predictions based on monolayer geometry and with numerical simulations that identify local electromagnetic field enhancements. Lastly, the EFs for the best performing Au NP monolayer are between 10 6 and 10 8 and give quantitative signal response when analyte concentration is changed.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Electrolyte Solvation Structure at Solid/Liquid Interface Probed by Nanogap Surface-Enhanced Raman Spectroscopy

Understanding the fundamental factors that drive ion solvation structure and transport is key to design high performance, stable battery electrolytes. Reversible ion solvation and desolvation are critical to the interfacial charge transfer process across the solid-liquid interface as well as the resulting stability of the solid electrolyte interphase (SEI). Here in this paper, we report the first study of Li+ salt solvation structure in aprotic solution in the immediate vicinity (~ 20 nm) of the solid electrode-liquid interface using surface-enhanced Raman spectroscopy (SERS) from a gold nanoparticle (Au NP) monolayer. The plasmonic coupling between Au NPs produces strong electromagnetic field enhancement in the gap region, leading to 5 orders of magnitude increase in Raman intensity for electrolyte components and their mixtures namely, lithium hexafluorophosphate (LiPF6), fluoroethylene carbonate (FEC), ethylene carbonate (EC) and diethyl carbonate (DEC). Further, we estimate and compare the lithium-ion solvation number derived from SERS and Infra-Red (FTIR) spectroscopy experiments to monitor and ascertain the changes in the solvation shell diameter in the confined nanogap region where there is maximum enhancement of the electric field. Our findings provide a new multi-modal spectroscopic approach to gain fundamental insights into the molecular structure of the electrolyte at the solid-liquid interface.

25 ENERGY STORAGE↗
DOE OSTI2021

Ultrabroadband Nanocavity of Hyperbolic Phonon–Polaritons in 1D-Like α-MoO 3

The exploitation of phonon–polaritons in nanostructured materials offers a pathway to manipulate infrared (IR) light for nanophotonic applications. Notably, hyperbolic phonon–polaritons (HP 2 ) in polar bidimensional crystals have been used to demonstrate strong electromagnetic field confinement, ultraslow group velocities, and long lifetimes (up to ~12 ps). Here we present nanobelts of α-phase molybdenum trioxide (α-MoO 3 ) as a low-dimensional medium supporting HP 2 modes in the mid- and far-IR ranges. Through real-space nanoimaging techniques with synchrotron and tunable laser IR light, we observe HP 2 Fabry-Perot resonances that demonstrate distinct anisotropic propagation and frequency dependence. We remark an anisotropic propagation that critically depends on the frequency range. Our findings are supported by the convergence of experiment, theory, and numerical simulations. Our work shows that the low dimensionality of natural nanostructured crystals, like α-MoO 3 nanobelts, provides an attractive platform to study polaritonic light–matter interactions and offers appealing cavity properties that could be harnessed in future designs of compact nanophotonic devices.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗