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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 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

MeV Scale Physics in MicroBooNE

This thesis presents the reconstruction and measurement of low-energy electromagnetic activity with beam neutrino interactions within the MicroBooNE Liquid Argon Time Projection Chamber (LArTPC). LArTPCs have proven to be excellent detectors to measure neutrino interaction cross sections and are being used to perform precision measurements of neutrino oscillation parameters. The work presented in this thesis has demonstrated unprecedentedly low, sub-MeV energy thresholds that have increased sensitivity of LArTPCs to detect neutrino interactions from core collapse supernovae and Muon Decay at Rest (µDAR). In addition, such low thresholds have also increased measurement sensitivity for interactions from Beyond the Standard Model (BSM) candidates such as millicharged particles and nuclear and electron recoils from dark matter candidate particles. On the reconstruction side, this work has established an energy resolution of 6.3% for electromagnetic activity i the 0-5 MeV energy range within the MicroBooNE LArTPC. Additionally this work presents the quantitative analysis of the low-energy activity emanating from G-10 support ribs in MicroBooNE and discusses how such activity could be a problematic source of background for low-energy physics analyses in future neutrino detectors such as the Deep Underground Neutrino Experiment (DUNE).

Bhat, Avinay↗
DOE OSTI2015

Collisionless shock experiments with lasers and observation of Weibel instabilities

Astrophysical collisionless shocks are common in the universe, occurring in supernova remnants, gamma ray bursts, and protostellar jets. They appear in colliding plasma flows when the mean free path for ion-ion collisions is much larger than the system size. It is believed that such shocks could be mediated via the electromagnetic Weibel instability in astrophysical environments without pre-existing magnetic fields. Here, we present laboratory experiments using high-power lasers and investigate the dynamics of high-Mach-number collisionless shock formation in two interpenetrating plasma streams. Our recent proton-probe experiments on Omega show the characteristic filamentary structures of the Weibel instability that are electromagnetic in nature with an inferred magnetization level as high as ∼1% [C. M. Huntington et al., “Observation of magnetic field generation via the weibel instability in interpenetrating plasma flows,” Nat. Phys. 11, 173–176 (2015)]. These results imply that electromagnetic instabilities are significant in the interaction of astrophysical conditions.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2019

Current drive by high intensity, pulsed, electron cyclotron wave packets

The nonlinear interaction of electrons with a high intensity, spatially localized, Gaussian, electromagnetic wave packet, or beam, in the electron cyclotron range of frequencies is described by the relativistic Lorentz equation. There are two distinct sets of electrons that result from wave-particle interactions. One set of electrons is reflected by the ponderomotive force due to the spatial variation of the wave packet. The second set of electrons are energetic enough to traverse across the wave packet. Both sets of electrons can exchange energy and momentum with the wave packet. The trapping of electrons in plane waves, which are constituents of the Gaussian beam, leads to dynamics that is distinctly different from quasilinear modeling of wave-particle interactions. This paper illustrates the changes that occur in the electron motion as a result of the nonlinear interaction. The dynamical differences between electrons interacting with a wave packet composed of ordinary electromagnetic waves and electrons interacting with a wave packet composed of extraordinary waves are exemplified.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2019

Phase Diagrams and Electromagnetic Propertiesof s–wave Superconductivity of the Extended Hubbard Model with the Attractive Pair–Hopping Interaction

The characteristics of the extended Hubbard model with the pair–hopping interaction J, i.e. the Penson–Kolb–Hubbard model, are analysed for the case of attractive J (J > 0). The effects of on–site U interaction on the properties of the s–wave superconducting state and mutual stability of the superconducting s–wave and magnetic orderings are examined. The electromagnetic and thermodynamic characteristics of the s–wave superconducting phase for arbitrary particle concentration n and interactions are analysed. The system is evaluated for the case of nearest–neighbours hopping on d–dimensional hypercubic d = 2 (SQ) and d = 3 (SC) nonfrustrated lattices. For SQ lattice the effects of phase fluctuations on the properties of the superconducting state are discussed within the Kosterlitz–Thouless (KT) scenario. The KT critical temperatures T{sub KT} are calculated and compared to the T{sub c} obtained within the BCS–HFA. The Uemura type plots, T{sub KT} vs. λ{sup 2}(0), are obtained and evaluated as a function of pairing strength and concentration. The results are compared with the case of repulsive J (J < 0) pair–hopping interaction.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

Interfacial engineering of plasmonic nanoparticle metasurfaces

This paper reports how the interfacial engineering of plasmonic nanoparticle (NP) lattices with desired surface characteristics can control plasmon-molecule interactions for tunable nanolasing thresholds. Compared to bare Cu NP lattices, graphene-coated Cu NPs surrounded by aromatic dye molecules gain support lasing with lower thresholds and at lower dye concentrations. This lasing enhancement is attributed to favorable molecular arrangements in electromagnetic hotspots through π–π interactions between graphene and IR-140 (5,5'-dichloro-11-diphenylamine-3,3'-diethyl-10,12-ethylene-thiatricarbocyanine-perchlorate) and 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (DCM) dyes. Besides the chemical interactions mediated by few-layer graphene, nanoscale dielectric layers such as fluoropolymer and alumina can also tailor the thresholds by modifying the spatial overlap of the dye near the NP surface. Our work lays the foundation for interfacial engineering of the surface of resonator units in plasmonic metasurfaces for exquisite control of light-matter interactions.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Nucleon properties from basis light front quantization

We investigate the electromagnetic properties of the nucleon using the framework of basis light front quantization. We consider the light front wave functions obtained by diagonalizing an effective Hamiltonian consisting of the holographic quantum chromodynamics confinement potential, a longitudinal confinement and a one-gluon exchange interaction with fixed coupling. The electromagnetic radii of the nucleon are also evaluated.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

A Study on Particle Trajectory Error in Finite-Element Particle-in-Cell Algorithms

Particle-in-cell (PIC) algorithms are widely used for the simulation of kinetic plasmas. PIC algorithms account for the interaction between charged particles in a plasma and the electromagnetic field in ambient space, including self-field interactions. The objective of this article is to study the error in charged particle trajectories present in finite-element (FE)-based PIC algorithms on unstructured meshes. We study how the trajectory error behaves according to the FE mesh resolution and the matrix solver employed in the FE algorithm. The study is performed by considering a trajectory established by a parabolic electric potential and an axial magnetic force acting on the charged particle. Under a proper choice combination of electric and magnetic field parameters, the 2-D particle trajectories comprise closed orbits. Numerical errors cause small perturbations on the trajectories, with cumulative effects. As a result, the resulting orbital trajectories exhibit distortions including spurious apsidal precession. These distortions provide a clear imprint of the numerical error. Here, we also study the numerical error in a quantitative fashion by computing the distance norm between the trajectories obtained by the exact fields and numerical fields.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2018

Hybrid Lithographic and DNA-Directed Assembly of a Configurable Plasmonic Metamaterial That Exhibits Electromagnetically Induced Transparency

Metamaterials are architectures that interact with light in novel ways by virtue of symmetry manipulation, and have opened a window into studying unprecedented light-matter interactions. However, they are commonly fabricated via lithographic methods, are usually static structures, and are limited in how they can react to external stimuli. Here we show that by combining lithographic techniques with DNA-based self-assembly methods, we can construct responsive plasmonic metamaterials that exhibit the plasmonic analog of an effect known as electromagnetically induced transparency (EIT), which can dramatically change their spectra upon motion of their constituent parts. Correlative scanning electron microscopy measurements, scattering dark-field microscopy, and computational simulations are performed on single assemblies to determine the relationship between their structures and spectral responses to a variety of external stimuli. The strength of the EIT-like effect in these assemblies can be tuned by precisely controlling the positioning of the plasmonic nanoparticles in these structures. For example, changing the ionic environment or dehydrating the sample will change the conformation of the DNA linkers and therefore the distance between the nanoparticles. Dark-field spectra of individual assemblies show peak shifts of up to many tens of nanometers upon DNA perturbations. This dynamic metamaterial represents a stepping stone toward state-of-the-art plasmonic sensing platforms and next-generation dynamic metamaterials.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Weak turbulence cascading effects in the acceleration and heating of ions in the solar wind

We study the wave-particle interaction and the evolution of electromagnetic waves propagating through a solar-wind-like plasma composed of cold electrons, isotropic protons, and a small portion of drifting anisotropic He{sup +2} (T {sub α} = 6 T {sub ∥α}) and O{sup +6} (T {sub O} = 11 T {sub ∥O}) ions as suggested in Gomberoff and Valdivia and Gomberoff et al., using two approaches. First, we use quasilinear kinetic theory to study the energy transfer between waves and particles, with the subsequent acceleration and heating of ions. Second, 1.5 D (one spatial dimension and three dimensions in velocity space) hybrid numerical simulations are performed to investigate the fully nonlinear evolution of this wave-particle interaction. Numerical results of both approaches show that the temperatures of all species evolve anisotropically, consistent with the time-dependent wave-spectrum energy. In a cascade effect, we observe the emergence of modes at frequencies higher than those initially considered, peaking at values close to the resonance frequencies of O{sup +6} ions (ω ∼ Ω {sub cO}) and He{sup +2} ions (ω ∼ Ω {sub cα}), being the peak due to O{sup +6} ions about three times bigger than the peak associated with He{sup +2} ions. Both the heating of the plasma and the energy cascade were more efficient in the nonlinear analysis than in the quasilinear one. These results suggest that this energy cascade mechanism may participate in the acceleration and heating of the solar wind plasma close to the Sun during fast streams associated with coronal holes.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

On numerical errors to the fields surrounding a relativistically moving particle in PIC codes

The particle-in-cell (PIC) method is widely used to model the self-consistent interaction between discrete particles and electromagnetic fields. It has been successfully applied to problems across plasma physics including plasma based acceleration, inertial confinement fusion, magnetically confined fusion, space physics, astrophysics, high energy density plasmas. In many cases the physics involves how relativistic particles (those with high relativistic γ factors) are generated and interact with plasmas. However, when relativistic particles stream across the grid, both in “vacuum” and in plasma, many numerical issues may arise which can lead to unphysical results. We present a detailed analysis of how discretized Maxwell solvers used in PIC codes can lead to numerical errors to the fields that surround particles that move at relativistic speeds across the grid. Expressions for the axial electric field as integrals in k space are presented that reveal two types of errors. The first arises from errors to the numerator of the integrand and leads to unphysical fields that are antisymmetric about the particle. Furthermore, the second arises from errors to the denominator of the integrand and lead to Cherenkov like radiation in “vacuum”. These fields are not anti-symmetric, extend behind the particle, and cause the particle to accelerate or decelerate depending on the solver and parameters. The unphysical fields are studied in detail for two representative solvers - the Yee solver and the FFT based solver. Although the Cherenkov fields are absent, the space charge fields are still present in the fundamental Brillouin zone for the FFT based solvers. In addition, the Cherenkov fields are present in higher order zones for the FFT based solvers. Comparison between the analytical solutions and PIC simulation results are presented. A solution for eliminating these unphysical fields by modifying the k operator in the axial direction is also presented. Using a customized finite difference solver, this solution was successfully implemented into OSIRIS [1]. Results from the customized solver are also presented. Additionally, this solution will be useful for a beam of particles that all move in one direction with a small angular divergence.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Superradiance in the Generalized (Non-Wiener) Dicke Model

It is shown that when nonresonant interactions between atoms and a vacuum electromagnetic field are included in analysis of emission of a localized ensemble of identical atoms, a delay must appear in the cooperative radiation pulse emitted by the atomic ensemble that is initially in a half-excited state. At the same time, the emission of cooperative radiation from a completely excited ensemble for certain parameters must begin without any delay. This contradicts the familiar facts of the conventional Dicke superradiance, in the theory of which nonresonant interactions are disregarded. The model taking into account nonresonant interactions along with other factors of the Dicke model is called the generalized Dicke model.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2023

Exploring Dark Sector Physics in MicroBooNE with e+e- Final States

Neutrinos are the second most abundant massive particle in the universe, but because of their small mass and weak interactions with matter, they are still not well understood. Due to their pervasive nature and unique properties, neutrinos make great probes to explore fundamental questions about the universe such as what is the composition of dark matter? The MiniBooNE experiment, designed to study neutrino oscillations, detected what has become a longstanding anomaly – an excess of low energy electromagnetic events from accelerator neutrino interactions. A possible explanation of the anomaly comes from neutrino interactions with nuclei that create heavier, sterile neutrinos that will decay quickly into electron-positron pairs. Complementing this is the MicroBooNE experiment, a liquid argon time projection chamber, that can reconstruct events well in both two and three dimensions and can distinguish electrons from photons. This reconstruction ability enables us to select dark sector neutrino interactions from other possible interactions using machine learning techniques such as graph neural networks (GNNs) which is the primary focus of this project.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

New particle pusher with hadronic interactions for modeling multimessenger emission from compact objects

We propose novel numerical schemes based on the Boris method in curved spacetime, incorporating both hadronic and radiative interactions for the first time. Once the proton has lost significant energy due to radiative and hadronic losses, and its gyroradius has decreased below typical scales on which the electromagnetic field varies, we apply a guiding center approximation (GCA). We fundamentally simulate collision processes either with a Monte-Carlo method or, where applicable, as a continuous energy loss, contingent on the local optical depth. To test our algorithm for the first time combining the effects of electromagnetic, gravitational, and radiation fields including hadronic interactions, we simulate highly relativistic protons traveling through various electromagnetic fields and proton backgrounds. We provide unit tests in various spatially dependent electromagnetic and gravitational fields and background photon and proton distributions, comparing the trajectory against analytic results. We propose that our method can be used to analyze hadronic interactions in black hole accretion disks, jets, and coronae to study the neutrino abundance from active galactic nuclei.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Self-Similar Character of Generation of Superradiance Pulses in an Electron–Wave Backward Wave Oscillator

The phenomenon of superradiance of electron bunches provides a promising method for generating high-power ultrashort electromagnetic pulses. In the present paper, it is shown that the equations describing the interaction between an electron beam and an electromagnetic wave in a BWO-type oscillator admit a self-similar solution that describes an amplifying and compressing pulse. It is demonstrated by numerical simulation that the generation of short superradiance pulses is of self-similar character at the initial stage of the transient process. The specific features of the main characteristics of such pulses (the amplitude and width of a pulse and the coordinates of its maximum) are investigated as a function of time and control parameters. It is shown that, after a transient process, the solution reaches the self-similar stage, where the pulse amplitude and the inverse of its squared width grow linearly with time.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2023

Resolving the mystery of electron perpendicular temperature spike in the plasma sheath

A large family of plasmas has collisional mean-free-path much longer than the non-neutral sheath width, which scales with the plasma Debye length. The plasmas, particularly the electrons, assume strong temperature anisotropy in the sheath. The temperature in the sheath flow direction (Te∥) is lower and drops toward the wall as a result of the decompressional cooling by the accelerating sheath flow. The electron temperature in the transverse direction of the flow field (Te⊥) not only is higher but also spikes up in the sheath. This abnormal behavior of Te⊥ spike is found to be the result of a negative gradient of the parallel heat flux of transverse degrees of freedom (qes) in the sheath. The non-zero heat flux qes is induced by pitch-angle scattering of electrons via either their interaction with self-excited electromagnetic waves in a nearly collisionless plasma or Coulomb collision in a collisional plasma, or both in the intermediate regime of plasma collisionality.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2018

Time Relativity in the Dynamics of Open Quantum Systems

When describing the dynamics of quantum systems interacting with a coherent external electromagnetic field, the instant at which the exciting (measuring) field begins to act is traditionally taken as zero time in the laboratory frame. Using the concept of coherence sudden death in an observed quantum system, we introduce the definition of local, completely incoherent subensembles of the quantum system in which it is found with a certain probability at each instant of time in the process of a continuous observation (measurement). For such subensembles an arbitrary instant of time in the laboratory frame is the initial time of the interaction with the external (measuring) field. As a result, the dynamics of an open quantum system is represented by a superposition of the dynamics of local subsystems with a continuous distribution of the times at which the interaction with the external field begins. We have derived an expression for the dynamical “multitime” contribution to the stationary solution of the Bloch equations, which clearly demonstrates the meaning of time relativity in the dynamics of two-level quantum systems in the semiclassical approximation. This dynamical multitime contribution is shown to explain the emergence of quantum beats at zero frequency (the Hanle effect, the level crossing) in EPR.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2022

Interacting quantum and classical waves: Resonant and non-resonant energy transfer to electrons immersed in an intense electromagnetic wave

Dynamics of electrons subjected to a constant amplitude classical electromagnetic (EM) wave is investigated as a fundamental, representative problem in the physics of interacting quantum and classical waves. In the nonrelativistic regime (electrons as Schrödinger waves), the electron energy acquires a constant and a time dependent part. Driven by EM waves, both parts scale strongly with the amplitude, but we expect no resonant enhancement since the parallel electron “speed” of nonrelativistic electrons could never match the wave phase velocity. In the relativistic regime (electron as a Klein–Gordon wave), however, a class of electron waves (with parallel speed matching the EM phase speed) are resonantly excited to extremely high energies. Such a direct resonant energy transfer from intense electromagnetic waves constitutes a mechanism that could, in principle, power the most energetic of cosmic rays (this mechanism will work on protons just as well). Some predictions of the theory will, hopefully, be tested in laboratory laser experiments. In conclusion, the nonrelativistic calculations will also be examined in the context of recent experiments using photon-induced near-field electron microscopy in detail.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗