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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 1,315 records · Page 73
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Simulating the effects of warm O + ions on the growth of electromagnetic ion cyclotron (EMIC) waves

Electromagnetic ion cyclotron (EMIC) waves are believed to play a crucial role in the dynamics of the Earth’s magnetosphere. It has been widely accepted that plasma compositions can influence the growth rate of EMIC waves in the inner magnetosphere, but how warm O + ions change the wave growth rate is not well known. In this study, we investigate the impact of ring current O + concentration on the EMIC growth rate during a specific storm when the O + ion flux significantly increases. We calculate the growth rate of EMIC waves by using physics-based ion distributions output from the Ring current–Atmosphere interactions Model with Self-Consistent magnetic (B) and Electric (E) fields (RAM-SCBE) model. The percentage of warm O + is parametrically varied to examine how the maximum EMIC growth rate changes over time and how the global distribution of the maximum EMIC growth rate is affected. We found that the maximum growth rate of H-band appears in the dusk-to-midnight sector near the plasmapause, while O-band is excited at a slightly outer region. The maximum growth rate of He-band is closely related to the cold plasma density. With the increase of warm O + density, the maximum growth rate of H-band and He-band EMIC wave is reduced, while that of O-band EMIC wave is increased, and the region with this wave excitation is widened. Furthermore, such variation in the maximum EMIC growth rate implies a potential impact on the associated wave–particle interactions and change of the decay rate in the ring current.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Sustainable chemistry with plasmonic photocatalysts

There is a pressing global need to increase the use of renewable energy sources and limit greenhouse gas emissions. Towards this goal, highly efficient and molecularly selective chemical processes that operate under mild conditions are critical. Plasmonic photocatalysis uses optically resonant metallic nanoparticles and their resulting plasmonic, electronic, and phononic light-matter interactions to drive chemical reactions. The promise of simultaneous high-efficiency and product-selective reactions with plasmon photocatalysis provides a compelling opportunity to rethink how chemistry is achieved. Plasmonic nanoparticles serve as nanoscale ‘antennas’ that enable strong light–matter interactions, surpassing the light-harvesting capabilities one would expect purely from their size. Complex composite structures, combining engineered light harvesters with more chemically active components, are a focal point of current research endeavors. In this review, we provide an overview of recent advances in plasmonic catalysis. We start with a discussion of the relevant mechanisms in photochemical transformations and explain hot-carrier generation and distributions from several ubiquitous plasmonic antennae. Then we highlight three important types of catalytic processes for sustainable chemistry: ammonia synthesis, hydrogen production and CO 2 reduction. To help elucidate the reaction mechanism, both state-of-art electromagnetic calculations and quantum mechanistic calculations are discussed. This review provides insights to better understand the mechanism of plasmonic photocatalysis with a variety of metallic and composite nanostructures toward designing and controlling improved platforms for green chemistry in the future.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Fano interference at the excitation of coherent phonons: Relation between the asymmetry parameter and the initial phase of coherent oscillations

The theoretical assertion that the Fano asymmetry parameter and the asymptotic initial phase of a harmonic oscillator interacting with a continuum are interrelated is experimentally verified. By an example of coherent fully symmetric A{sub 1g} phonons in bismuth that are excited by ultrashort laser pulses at liquid helium temperature, it is demonstrated that, for negative values of the asymmetry parameter, the asymptotic phase increases as the modulus of the parameter decreases.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

LPSE : A 3-D wave-based model of cross-beam energy transfer in laser-irradiated plasmas

The new component of the “laser–plasma simulation environment” (LPSE) described here is a practical numerical model that solves the coupled vector equations for the propagation of nearly monochromatic, coherent, lectromagnetic waves in inhomogeneous unmagnetized plasmas. It operates efficiently in the numerically challenging semiclassical regime where characteristic plasma scale lengths are many times greater than the wavelength of the light and solutions are highly oscillatory. Solutions can be obtained in one, two, or three spatial dimensions and time. Additionally, the model includes the effects of nonlinear coupling of electromagnetic waves to the low-frequency plasma perturbations (i.e., ion-acoustic response) that are responsible for stimulated Brillouin scattering. Induced plasma perturbations are assumed to be imposed on a prescribed large-scale inhomogeneous background that includes spatially varying plasma density and flow. Our code is directly relevant to the problem of cross-beam energy transfer in laser-driven inertial confinement fusion. Lastly, it may also be applicable in other areas where eikonal solutions of multicomponent wave equations (or coupled wave equations) are insufficient, such as optical scattering from ultrasound, electron dynamics in quantum devices or in nanoscale light–matter interactions.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2014

Electromagnetic gyrokinetic turbulence in finite-beta helical plasmas

A saturation mechanism for microturbulence in a regime of weak zonal flow generation is investigated by means of electromagnetic gyrokinetic simulations. The study identifies a new saturation process of the kinetic ballooning mode (KBM) turbulence originating from the spatial structure of the KBM instabilities in a finite-beta Large Helical Device (LHD) plasma. Specifically, the most unstable KBM in LHD has an inclined mode structure with respect to the mid-plane of a torus, i.e., it has a finite radial wave-number in flux tube coordinates, in contrast to KBMs in tokamaks as well as ion-temperature gradient modes in tokamaks and helical systems. The simulations reveal that the growth of KBMs in LHD is saturated by nonlinear interactions of oppositely inclined convection cells through mutual shearing as well as by the zonal flow. The saturation mechanism is quantitatively investigated by analysis of the nonlinear entropy transfer that shows not only the mutual shearing but also a self-interaction with an elongated mode structure along the magnetic field line.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2022

Universal trend of charge radii of even-even Ca–Zn nuclei

Radii of nuclear charge distributions carry information about the strong and electromagnetic forces acting inside the atomic nucleus. Whereas the global behavior of nuclear charge radii is governed by the bulk properties of nuclear matter, their local trends are affected by quantum motion of proton and neutron nuclear constituents. The measured differential charge radii δ$\langle$$r^{2}_{c}$$\rangle$ between neutron numbers N = 28 and N = 40 exhibit a universal pattern as a function of n = N – 28 that is independent of the atomic number. In this work, we analyze this remarkable behavior in even-even nuclei from calcium to zinc using two state-of-the-art theories based on quantified nuclear interactions: the ab initio coupled cluster theory and nuclear density functional theory. Both theories reproduce the smooth rise of differential charge radii and their weak dependence on the atomic number. By considering a large set of isotopic chains, we show that this trend can be captured by just two parameters: the slope and curvature of δ$\langle$$r^{2}_{c}$$\rangle$(n). We demonstrate that these parameters show appreciable model dependence, and the statistical analysis indicates that they are not correlated with any single model property, i.e., they are impacted by both bulk nuclear properties as well as shell structure.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Energetic Electron Precipitation Driven by Electromagnetic Ion Cyclotron Waves from ELFIN’s Low Altitude Perspective

We review comprehensive observations of electromagnetic ion cyclotron (EMIC) wave-driven energetic electron precipitation using data collected by the energetic electron detector on the Electron Losses and Fields InvestigatioN (ELFIN) mission, two polar-orbiting low-altitude spinning CubeSats, measuring 50-5000 keV electrons with good pitch-angle and energy resolution. EMIC wave-driven precipitation exhibits a distinct signature in energy-spectrograms of the precipitating-to-trapped flux ratio: peaks at >0.5 MeV which are abrupt (bursty) (lasting ~17 s, or ΔL ~ 0.56) with significant substructure (occasionally down to sub-second timescale). We attribute the bursty nature of the precipitation to the spatial extent and structuredness of the wave field at the equator. Multiple ELFIN passes over the same MLT sector allow us to study the spatial and temporal evolution of the EMIC wave - electron interaction region. Case studies employing conjugate ground-based or equatorial observations of the EMIC waves reveal that the energy of moderate and strong precipitation at ELFIN approximately agrees with theoretical expectations for cyclotron resonant interactions in a cold plasma. Using multiple years of ELFIN data uniformly distributed in local time, we assemble a statistical database of ~50 events of strong EMIC wave-driven precipitation. Most reside at L ~ 5 – 7 at dusk, while a smaller subset exists at L ~ 8 – 12 at post-midnight. The energies of the peak-precipitation ratio and of the half-peak precipitation ratio (our proxy for the minimum resonance energy) exhibit an L-shell dependence in good agreement with theoretical estimates based on prior statistical observations of EMIC wave power spectra. The precipitation ratio’s spectral shape for the most intense events has an exponential falloff away from the peak (i.e., on either side of ~ 1.45 MeV). It too agrees well with quasi-linear diffusion theory based on prior statistics of wave spectra. It should be noted though that this diffusive treatment likely includes effects from nonlinear resonant interactions (especially at high energies) and nonresonant effects from sharp wave packet edges (at low energies). Sub-MeV electron precipitation observed concurrently with strong EMIC wave-driven >1 MeV precipitation has a spectral shape that is consistent with efficient pitch-angle scattering down to ~ 200-300 keV by much less intense higher frequency EMIC waves at dusk (where such waves are most frequent). At ~100 keV, whistler-mode chorus may be implicated in concurrent precipitation. These results confirm the critical role of EMIC waves in driving relativistic electron losses. Nonlinear effects may abound and require further investigation.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

Biomimetic Hierarchical Assembly of Helical Supraparticles from Chiral Nanoparticles

Chiroptical materials found in butterflies, beetles, stomatopod crustaceans, and other creatures are attributed to biocomposites with helical motifs and multiscale hierarchical organization. These structurally sophisticated materials self-assemble from primitive nanoscale building blocks, a process that is simpler and more energy efficient than many top-down methods currently used to produce similarly sized three-dimensional materials. In this paper, we report that molecular-scale chirality of a CdTe nanoparticle surface can be translated to nanoscale helical assemblies, leading to chiroptical activity in the visible electromagnetic range. Chiral CdTe nanoparticles coated with cysteine self-organize around Te cores to produce helical supraparticles. D-/L-Form of the amino acid determines the dominant left/right helicity of the supraparticles. Coarse-grained molecular dynamics simulations with a helical pair-potential confirm the assembly mechanism and the origin of its enantioselectivity, providing a framework for engineering three-dimensional chiral materials by self-assembly. Finally, the helical supraparticles further self-organize into lamellar crystals with liquid crystalline order, demonstrating the possibility of hierarchical organization and with multiple structural motifs and length scales determined by molecular-scale asymmetry of nanoparticle interactions.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2016

Van Allen Probes, THEMIS, GOES, and cluster observations of EMIC waves, ULF pulsations, and an electron flux dropout

We examined an electron flux dropout during the 12–14 November 2012 geomagnetic storm using observations from seven spacecraft: the two Van Allen Probes, Time History of Events and Macroscale Interactions during Substorms (THEMIS)-A (P5), Cluster 2, and Geostationary Operational Environmental Satellites (GOES) 13, 14, and 15. The electron fluxes for energies greater than 2.0 MeV observed by GOES 13, 14, and 15 at geosynchronous orbit and by the Van Allen Probes remained at or near instrumental background levels for more than 24 h from 12 to 14 November. For energies of 0.8 MeV, the GOES satellites observed two shorter intervals of reduced electron fluxes. The first interval of reduced 0.8 MeV electron fluxes on 12–13 November was associated with an interplanetary shock and a sudden impulse. Cluster, THEMIS, and GOES observed intense He + electromagnetic ion cyclotron (EMIC) waves from just inside geosynchronous orbit out to the magnetopause across the dayside to the dusk flank. The second interval of reduced 0.8 MeV electron fluxes on 13–14 November was associated with a solar sector boundary crossing and development of a geomagnetic storm with Dst <–100 nT. At the start of the recovery phase, both the 0.8 and 2.0 MeV electron fluxes finally returned to near prestorm values, possibly in response to strong ultralow frequency (ULF) waves observed by the Van Allen Probes near dawn. A combination of adiabatic effects, losses to the magnetopause, scattering by EMIC waves, and acceleration by ULF waves can explain the observed electron behavior.

58 GEOSCIENCES↗
DOE OSTI2017

Millisecond Magnetar Birth Connects FRB 121102 to Superluminous Supernovae and Long-duration Gamma-Ray Bursts

Subarcsecond localization of the repeating fast radio burst FRB 121102 revealed its coincidence with a dwarf host galaxy and a steady (“quiescent”) nonthermal radio source. We show that the properties of the host galaxy are consistent with those of long-duration gamma-ray bursts (LGRB) and hydrogen-poor superluminous supernovae (SLSNe-I). Both LGRBs and SLSNe-I were previously hypothesized to be powered by the electromagnetic spin-down of newly formed, strongly magnetized neutron stars with millisecond birth rotation periods (“millisecond magnetars”). This motivates considering a scenario whereby the repeated bursts from FRB 121102 originate from a young magnetar remnant embedded within a young hydrogen-poor supernova (SN) remnant. Requirements on the gigahertz free–free optical depth through the expanding SN ejecta (accounting for photoionization by the rotationally powered magnetar nebula), energetic constraints on the bursts, and constraints on the size of the quiescent source all point to an age of less than a few decades. The quiescent radio source can be attributed to synchrotron emission from the shock interaction between the fast outer layer of the supernova ejecta with the surrounding wind of the progenitor star, or the radio source can from deeper within the magnetar wind nebula as outlined in Metzger et al. Alternatively, the radio emission could be an orphan afterglow from an initially off-axis LGRB jet, though this might require the source to be too young. The young age of the source can be tested by searching for a time derivative of the dispersion measure and the predicted fading of the quiescent radio source. We propose future tests of the SLSNe-I/LGRB/FRB connection, such as searches for FRBs from nearby SLSNe-I/LGRBs on timescales of decades after their explosions.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

Self-assembly of colloidal bands driven by a periodic external field

We study the formation of bands of colloidal particles driven by periodic external fields. Using Brownian dynamics, we determine the dependence of the band width on the strength of the particle interactions and on the intensity and periodicity of the field. We also investigate the switching (field-on) dynamics and the relaxation times as a function of the system parameters. The observed scaling relations were analyzed using a simple dynamic density-functional theory of fluids.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Diffusion of energetic electrons in turbulent plasmas of the solar wind

A method of calculation of the diffusion coefficients D(v) of particles in velocity space, based on the statistical analysis of the motion of a great number of test electrons, is proposed. In the case of Langmuir turbulence developing in plasmas with fluctuating density inhomogeneities such as the solar wind, simulations provide coefficients D(v) which mainly depend on the Langmuir wave spectra and agree well with the analytical predictions D{sub th}(v) of the quasilinear theory of weak turbulence. Nevertheless, some noticeable differences exist with this theory: in the range of phase velocity of the short waves where the main part of the wave energy is concentrated, D(v) is noticeably smaller than D{sub th}(v), due to the scattering, the reflection, and the focusing effects encountered by the Langmuir waves when they interact with the plasma density inhomogeneities. Moreover, the probability of large velocity jumps in the particles’ trajectories essentially exceeds the probability of a Gaussian distribution. These large jumps, which are connected with the waves’ transformation processes, modify the nature of the particle diffusion, which is no more classical. These higher order effects cause the discrepancies observed with the quasilinear theory, which does not take them into account in its perturbative approach. The solar wind plasmas, which present fluctuating density inhomogeneities of noticeable average levels, are a very good laboratory to study such diffusion processes, which can eventually influence significantly on the development of essential physical phenomena, as electromagnetic radio emissions by type III solar radio bursts, for example.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2019

Global Ten-Moment Multifluid Simulations of the Solar Wind Interaction with Mercury: From the Planetary Conducting Core to the Dynamic Magnetosphere

In this work, we explore for the first time the tightly coupled interior-magnetosphere system of Mercury by employing a three-dimensional ten-moment multifluid model. This novel fluid model incorporates the nonideal effects including the Hall effect, electron inertia, and tensorial pressures that are critical for collisionless magnetic reconnection; therefore, it is particularly well suited for investigating collisionless magnetic reconnection in Mercury's magnetotail and at the planet's magnetopause. Additionally, the model is able to reproduce the observed magnetic field vectors, field-aligned currents, and cross-tail current sheet asymmetry (beyond magnetohydrodynamic approach), and the simulation results are in good agreement with spacecraft observations. We also study the magnetospheric response of Mercury to a hypothetical extreme event with an enhanced solar wind dynamic pressure, which demonstrates the significance of induction effects resulting from the electromagnetically coupled interior. More interestingly, plasmoids (or flux ropes) are formed in Mercury's magnetotail during the event, indicating the highly dynamic nature of Mercury's magnetosphere.

58 GEOSCIENCES↗
DOE OSTI2019

Protecting superconducting qubits from phonon mediated decay

For quantum computing to become fault tolerant, the underlying quantum bits must be effectively isolated from the noisy environment. It is well known that including an electromagnetic bandgap around the qubit operating frequency improves coherence for superconducting circuits. However, investigations of bandgaps to other environmental coupling mechanisms remain largely unexplored. We present a method to enhance the coherence of superconducting circuits by introducing a phononic bandgap around the device operating frequency. The phononic bandgaps block resonant decay of defect states within the gapped frequency range, removing the electromagnetic coupling to phonons at the gap frequencies. We construct a multiscale model that derives the decrease in the density of states due to the bandgap and the resulting increase in defect state T 1 times. We demonstrate that emission rates from in-plane defect states can be suppressed by up to two orders of magnitude. We combine these simulations with theory for resonators operating in the continuous-wave regime and show that improvements in quality factors are expected by up to the enhancement in defect T 1 times. Furthermore, we use full master equation simulation to demonstrate the suppression of qubit energy relaxation even when interacting with 200 defect states. We conclude with an exploration of device implementation including tradeoffs between fabrication complexity and qubit performance.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

Design, construction and commissioning of a technological prototype of a highly granular SiPM-on-tile scintillator-steel hadronic calorimeter

The CALICE collaboration is developing highly granular electromagnetic and hadronic calorimeters for detectors at future energy frontier electron-positron colliders. After successful tests of a physics prototype, a technological prototype of the Analog Hadron Calorimeter has been built, based on a design and construction techniques scalable to a collider detector. The prototype consists of a steel absorber structure and active layers of small scintillator tiles that are individually read out by directly coupled SiPMs. Each layer has an active area of 72 × 72 cm^2 and a tile size of 3 × 3 cm^2. With 38 active layers, the prototype has nearly 22,000 readout channels, and its total thickness amounts to 4.4 nuclear interaction lengths. The dedicated readout electronics provide time stamping of each hit with an expected resolution of about 1 ns. The prototype was constructed in 2017 and commissioned in beam tests at DESY. It recorded muons, hadron showers and electron showers at different energies in test beams at CERN in 2018. In this paper, the design of the prototype, its construction and commissioning are described. The methods used to calibrate the detector are detailed, and the performance achieved in terms of uniformity and stability is presented.

47 OTHER INSTRUMENTATION↗
DOE OSTI2024

Analytical model and dynamical phase-field simulation of terahertz transmission across ferroelectrics

Here, we theoretically investigate the steady-state transmission of continuous terahertz (THz) wave across a freestanding ferroelectric slab. Based on the Landau-Ginzburg-Devonshire theory of ferroelectrics and the coupled equations of motion for polarization and electromagnetic (EM) waves, we derive the analytical expressions of the frequency- and thickness-dependent dielectric susceptibility and transmission coefficient at the thin slab limit in the harmonic excitation regime. When the slab thickness is much smaller than the THz wavelength in the ferroelectric, the analytical predictions agree well with the numerical simulations from a dynamical phase-field model that incorporates the coupled dynamics of strain, polarization, and EM wave in multiphase systems. At larger thicknesses, the transmission is mainly determined by the frequency-dependent attenuation of THz waves in the ferroelectric and the formation of a standing polarization/THz wave. Our results advance the understanding of the interaction between THz wave and ferroelectrics and suggest the potential of exploiting ferroelectrics to achieve low-heat-dissipation, nonvolatile voltage modulation of THz transmission for high-data-rate wireless communication.

36 MATERIALS SCIENCE↗
DOE OSTI2018

A Novel Interfacing Technique for Distributed Hybrid Simulations Combining EMT and Transient Stability Models

With steady increase of power electronic devices and nonlinear dynamic loads in large scale AC/DC systems, the traditional hybrid simulation method, which incorporates these components into a single EMT subsystem and hence causes great difficulty for network partitioning and significant deterioration in simulation efficiency. To resolve these issues, a novel distributed hybrid simulation method is proposed in this paper. The key to realize this method is a distinct interfacing technique, which includes: i) a new approach based on the two-level Schur complement to update the interfaces by taking full consideration of the couplings between different EMT subsystems; and ii) a combined interaction protocol to further improve the efficiency while guaranteeing the simulation accuracy. The advantages of the proposed method in terms of both efficiency and accuracy have been verified by using it for the simulation study of an AC/DC hybrid system including a two-terminal VSC-HVDC and nonlinear dynamic loads.

Distributed hybrid simulation↗