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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 1,153 records · Page 64
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Nucleon-pair approximation for nuclei from spherical to deformed regions

Here we model low-lying states of atomic nuclei in the nucleon-pair approximation of the shell model, using three approaches to select collective nucleon pairs: the generalized seniority scheme, the conjugate gradient method, and the Hartree-Fock approach. We find the collective pairs obtained from the generalized seniority scheme provide a good description for nearly spherical nuclei, and those from the conjugate gradient method or the Hartree-Fock approach work well for transitional and deformed nuclei. Our NPA calculations using collective pairs with angular momenta 0, 2, and 4 (denoted by S D G pairs) reproduce the nuclear shape evolution in the N = 26 isotones, Ca 46 , Ti 48 , Cr 50 , and Fe 52 , and yield good agreement with full configuration-interaction calculations of low-lying states in medium-heavy transitional and deformed nuclei: Ti 44 – 48 , Cr 48 , Cr 50 , Fe 52 , Zn 60 – 64 , Ge 64 , 66 , Mo 84 , and Xe 108 – 112 . Finally, using the S D G I -pair approximation we describe low-lying states of Ba 112 , 114 , cases difficult to reach by conventional configuration-interaction methods.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2019

Toward the limit of nuclear binding on the N = Z line: Spectroscopy of Cd 96

A γ-decaying isomeric state (τ 1/2 = $197$ $^{+19}_{–17}$ ns) has been identified in 96 Cd, which is one α particle away from the last known bound N = Z nucleus, 100 Sn. Comparison of the results with shell-model calculations has allowed a tentative experimental level scheme to be deduced and the isomer to be interpreted as a medium-spin negative-parity spin trap based on the coupling of isoscalar (T = 0) and isovector (T = 1) neutron-proton pairs. The data also suggest evidence for the population of a 9 + T = 1 state, which is predicted by shell-model calculations to be yrast. Here, such a low-lying T = 1 state, which is unknown in lighter mass even-even self-conjugate nuclei, can also be interpreted in terms of the coupling of T = 0 and T = 1 neutron-proton pairs.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Harmonic Modeling, Data Generation and Analysis of Power Electronics-Interfaced Residential Loads

The share of electronics-based residential load is expected to rise as devices such as variable frequency drives (VFDs), electric vehicle chargers, and inverter-based distributed energy resources (DERs), e.g., photovoltaic (PV) systems become more common. These loads may introduce significant harmonics into power networks that need to be closely studied in order to perform accurate load modeling and forecasting. However, it can be difficult to obtain harmonic-rich voltage and current data - necessary for identifying accurate load models - for residential electrical loads. Recognizing this need, we identify and model a set of electronics-based end-use loads and DERs in an electromagnetic transients program (EMTP) tool for a residence with a single- phase split-phase supply. Further, a procedure is developed to model harmonic interactions between end-use loads connected to the same non-ideal supply voltage in a residential setting. Finally, a harmonic-rich dataset produced via the proposed procedure is utilized to identify frequency coupling matrix (FCM) based load model. Numerical results demonstrate the accuracy of the model, and explore model identifiability with limited data points.

harmonics, power quality, load modeling↗
DOE OSTI2019

Precision Measurements of Electron-Proton Elastic Scattering Cross Sections at Large Q2

The electromagnetic form factors are fundamental quantities characterizing the internal structure of the nucleon. Their measurements have provided significant insight into the spatial distribution and interaction of quarks inside the proton. The knowledge of high Q2 form factors proves essential in understanding the properties of quantum chromodynamics in the transition region from non-perturbative to perturbative behavior. It also provides important links to generalized parton distributions, which describe the three-dimensional structure of hadrons at the parton level. In view of the significant theoretical research activities in this field, high quality experimental data are crucial for providing stringent tests and benchmarks to guide and test different models. The form factors can be accessed in experiments by measuring elastic scattering of electrons off a hydrogen target. Experiment E12-07-108, which took place at the Thomas Jefferson National Accelerator Facility, conducted precise measurements of the unpolarized e-p elastic scattering cross section over a Q2 range of 0.6-16.5 GeV2 . This thesis presents the results for 7 kinematic settings with total uncertainties that are 1.5 times smaller than those of the existing data at large Q2 . The proton magnetic form factors were extracted using a parameterization of the form factor ratio obtained from recent polarized e-p scattering experiments. Comparisons to existing global and phenomenological fits are presented.

Ou, Longwu↗
DOE OSTI2017

Open-source framework for power system transmission and distribution dynamics co-simulation

The promise of the smart grid entails more interactions between the transmission and distribution networks, and there is an immediate need for tools to provide the comprehensive modelling and simulation required to integrate operations at both transmission and distribution levels. Existing electromagnetic transient simulators can perform simulations with integration of transmission and distribution systems, but the computational burden is high for large-scale system analysis. For transient stability analysis, currently there are only separate tools for simulating transient dynamics of the transmission and distribution systems. In this paper, we introduce an open source co-simulation framework “Framework for Network Co-Simulation” (FNCS), together with the decoupled simulation approach that links existing transmission and distribution dynamic simulators through FNCS. FNCS is a middleware interface and framework that manages the interaction and synchronization of the transmission and distribution simulators. Preliminary testing results show the validity and capability of the proposed open-source co-simulation framework and the decoupled co-simulation methodology.

Huang, Renke↗
DOE OSTI2016

Gauge-invariant expectation values of the energy of a molecule in an electromagnetic field

In this paper, we show that the full Hamiltonian for a molecule in an electromagnetic field can be separated into a molecular Hamiltonian and a field Hamiltonian, both with gauge-invariant expectation values. The expectation value of the molecular Hamiltonian gives physically meaningful results for the energy of a molecule in a time-dependent applied field. In contrast, the usual partitioning of the full Hamiltonian into molecular and field terms introduces an arbitrary gauge-dependent potential into the molecular Hamiltonian and leaves a gauge-dependent form of the Hamiltonian for the field. With the usual partitioning of the Hamiltonian, this same problem of gauge dependence arises even in the absence of an applied field, as we show explicitly by considering a gauge transformation from zero applied field and zero external potentials to zero applied field, but non-zero external vector and scalar potentials. We resolve this problem and also remove the gauge dependence from the Hamiltonian for a molecule in a non-zero applied field and from the field Hamiltonian, by repartitioning the full Hamiltonian. It is possible to remove the gauge dependence because the interaction of the molecular charges with the gauge potential cancels identically with a gauge-dependent term in the usual form of the field Hamiltonian. We treat the electromagnetic field classically and treat the molecule quantum mechanically, but nonrelativistically. Our derivation starts from the Lagrangian for a set of charged particles and an electromagnetic field, with the particle coordinates, the vector potential, the scalar potential, and their time derivatives treated as the variables in the Lagrangian. We construct the full Hamiltonian using a Lagrange multiplier method originally suggested by Dirac, partition this Hamiltonian into a molecular term H{sub m} and a field term H{sub f}, and show that both H{sub m} and H{sub f} have gauge-independent expectation values. Any gauge may be chosen for the calculations; but following our partitioning, the expectation values of the molecular Hamiltonian are identical to those obtained directly in the Coulomb gauge. As a corollary of this result, the power absorbed by a molecule from a time-dependent, applied electromagnetic field is equal to the time derivative of the non-adiabatic term in the molecular energy, in any gauge.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2013

Laboratory Studies of the Short-term Responses of Freshwater Fish to Electromagnetic Fields

Hydrokinetic energy technologies are being proposed as an environmentally preferred means of generating electricity from river and tidal currents. Among the potential issues that must be investigated in order to resolve environmental concerns are the effects on aquatic organisms of electromagnetic fields created by underwater generators and transmission cables. The behavioral responses of common freshwater fishes to static and variable electromagnetic fields (EMF) that may be emitted by hydrokinetic projects were evaluated in laboratory experiments. Various fish species were exposed to either static (DC) EMF fields created by a permanent bar magnet or variable (AC) EMF fields created by a switched electromagnet for 48 h, fish locations were recorded with a digital imaging system, and changes in activity level and distribution relative to the magnet position were quantified at 5-min intervals. Experiments with fathead minnows, redear sunfish, striped bass, lake sturgeon, and channel catfish produced mixed results. Except for fathead minnows there was no effect on activity level. Only redear sunfish and channel catfish exhibited a change in distribution relative to the position of the magnet with an apparent attraction to the EMF source. In separate experiments, rapid behavioral responses of paddlefish and lake sturgeon to onset of the AC field were recorded with high-speed video. Paddlefish did not react to a variable, 60-Hz magnetic field like that which would be emitted by an AC generator or cable, but lake sturgeon consistently responded to the variable, AC-generated magnetic field with a variety of altered swimming behaviors. These results will be useful for determining under what circumstances cables or generators need to be positioned to minimize interactions with sensitive species.

electromagnetic↗
DOE OSTI2019

Nucleon-to-Roper electromagnetic transition form factors at large Q 2

High-precision nucleon-resonance electroproduction data on a large kinematic domain of energy and momentum transfer have proven crucial in revealing novel features of strong interactions within the Standard Model and unfolding structural details of baryon excited states. Thus, in anticipation of new data reaching to unprecedented photon virtuality, we employ a quark-diquark approximation to the three-valence-quark bound-state problem to compute γ*p → R + and γ*n → R 0 transition form factors on Q 2 /m 2 N ϵ[0,12], where m N is the nucleon mass. Having simultaneously analyzed both charged and neutral channels, we also provide a quark-flavor separation of the transition form factors. Furthermore, the results should be useful in planning new-generation experiments.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Hybrid SERS platform by adapting both chemical mechanism and electromagnetic mechanism enhancements: SERS of 4-ATP and CV by the mixture with GQDs on hybrid PdAg NPs

Surface-enhanced Raman spectroscopy (SERS) is a versatile analytical technique widely adapted for the identification of target analytes even at an extremely low concentration. Herein, a unique hybrid SERS platform is demonstrated by utilizing the graphene quantum dots (GQDs) and hybrid PdAg NPs for the detection of 4-amino-thiophenol (4-ATP) and crystal violet (CV). GQDs offer the rich charge transfer to the LUMO and HOMO of 4-ATP and CV by the CM enhancement. A significant EM enhancement is achieved by the strong localized surface plasmon resonance (LSPR) of uniquely designed hybrid core-shell PdAg NP, possessing the narrow nano-gaps with the highly dense small Ag NPs and Pd core Ag shell configuration. As a result, orders of enhancement of originally weak 4-ATP and CV Raman signal is witnessed by the combination of electromagnetic mechanism (EM) and chemical mechanism (CM) enhancements on a single SERS substrate. The hybrid GQD/HNP SERS substrate demonstrates significantly improved hot spots and strongly localized electromagnetic fields as confirmed by the finite-difference time-domain (FDTD) simulations. There for a proper mixture ratio of GQDs and probe molecules presents largely enhanced SERS signals by a strong adsorption of probe molecules through π - π interaction and the enhancement factors vary by the mixture ratio depending on the adsorption kinetics and Raman cross-section of molecules.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Influence of Mn addition on the microstructure and mechanical properties of a directionally solidified γ-TiAl alloy

Highlights: • Mn addition can significantly improve the yield strength of TiAl alloy. • Introduction of Mn facilitates the operation of twinning-controlled deformation. • Twin-dislocation interactions cause a continuous increase in work hardening rate. - Abstract: TiAl alloys with nominal compositions of Ti-47Al-2Nb-2Cr-(0, 1, 3, 5)Mn were prepared via electromagnetic cold crucible directional solidification (ECCDS), and the influence of Mn addition on the microstructure and mechanical properties of the alloys was investigated. The experimental results showed that the Mn atoms were dissolved within the TiAl alloy, and no Mn compounds were formed. Based on the X-ray diffraction (XRD) analysis results, the peak angle of the Mn-containing sample shifted to a higher value, indicating lattice shrinkage. The Mn addition also increased the volume fraction of the B2 phase. The yield strength of the TiAl alloy monotonically increased as the content of the substitutional-solute Mn atoms increased. The ultimate strengths of the TiAl alloys containing 1 at.%, 3 at.%, and 5 at.% Mn consequently decreased because micro-cracks were preferentially formed in the B2 phase during room-temperature deformation. The introduction of substitutional-solute Mn atoms could result in a reduction of the stacking-fault energy of the γ phase, and facilitate the operation of twinning-controlled plastic-deformation during the intermediate stage of the plastic deformation process. The interaction between the deformation twins and movable dislocations led to a continuous increase in the work-hardening rate.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Plasma Anisotropies and Currents in the Near-Earth Plasma Sheet and Inner Magnetosphere

The region occupying radial distances of ~3–9 Earth radii (R E ) in the nightside includes the near-Earth plasma sheet with stretched magnetic field lines and the inner magnetosphere with strong dipolar magnetic field. In this region, the plasma flow energy, which was injected into the inner magnetosphere from the magnetotail, is converted to particle heating and electromagnetic wave generation. These important processes are controlled by plasma anisotropies, which are the focus here. Using measurements of Time History of Events and Macroscale Interactions during Substorms and Van Allen Probes in this transition region we obtain radial profiles of ion and electron temperatures and anisotropies for various geomagnetic activity levels. Ion and electron anisotropies vary with the geomagnetic activity in opposite directions. Parallel anisotropic ions are observed together with transversely anisotropic electrons, whereas the change of ion anisotropy from parallel to transverse (with increasing K p ) is accompanied by the electron anisotropy changing from transverse to parallel. Finally, based on plasma anisotropy observations, we estimate that the anisotropy-related currents (curvature currents) are about 10–20% of the diamagnetic currents.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2017

High-Energy Gamma Rays and Neutrinos from Nearby Radio Galaxies

Multi-messenger data suggest that radio galaxies (ie non-blazar active galaxies) are a well-motivated class of sources for the diffuse flux of high-energy neutrinos reported by the IceCube Collaboration. In this study, we consider the gamma-ray spectrum observed from four nearby radio galaxies (Centaurus A, PKS 0625-35, NGC 1275 and IC 310) and constrain the intensity and spectral shape of the emission injected from these sources, accounting for the effects of attenuation and contributions from electromagnetic cascades (initiated both within the radio galaxy itself and during extragalactic propagation). Assuming that this gamma-ray emission is generated primarily through the interactions of cosmic-ray protons with gas, we calculate the neutrino flux predicted from each of these sources. Although this scenario is consistent with the constraints published by the IceCube and ANTARES Collaborations, the predicted fluxes consistently fall within an order of magnitude of the current point source sensitivity. The prospects appear very encouraging for the future detection of neutrino emission from the nearest radio galaxies.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Strong-field ionization and gauge dependence of nonlocal potentials

Nonlocal potential models have been used in place of the Coulomb potential in the Schrödinger equation as an efficient means of exploring high-field laser-atom interaction in previous works. Although these models have found use in modeling phenomena including photoionization and ejected electron momentum spectra, they are known to break electromagnetic gauge invariance. This paper examines if there is a preferred gauge for the linear field response and photoionization characteristics of nonlocal atomic binding potentials in the length and velocity gauges. Overall, it is found that the length gauge is preferable for a wide range of parameters.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2023

Hybrid Simulation and Quasi-linear Theory of Bi-Kappa Proton Instabilities

The quasi-steady states of collisionless plasmas in space (e.g., in the solar wind and planetary environments) are governed by the interactions of charged particles with wave fluctuations. These interactions are responsible not only for the dissipation of plasma waves but also for their excitation. The present analysis focuses on two instabilities, mirror and electromagnetic ion cyclotron instabilities, associated with the same proton temperature anisotropy T ⊥ > T ∥ (where ⊥, ∥ are directions defined with respect to the local magnetic field vector). Theories relying on standard Maxwellian models fail to link these two instabilities (i.e., predicted thresholds) to the proton quasi-stable anisotropies measured in situ in a completely satisfactory manner. Here we revisit these instabilities by modeling protons with the generalized bi-Kappa (bi-κ power-law) distribution, and by a comparative analysis of a 2D hybrid simulation with the velocity-moment-based quasi-linear (QL) theory. It is shown that the two methods feature qualitative and, even to some extent, quantitative agreement. The reduced QL analysis based upon the assumption of a time-dependent bi-Kappa model thus becomes a valuable theoretical approach that can be incorporated into the present studies of solar wind dynamics.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2019

MEASUREMENT OF THE CHARGED-CURRENT INCLUSIVE ELECTRON NEUTRINO AND ELECTRON ANTINEUTRINO CROSS SECTION USING THE MICROBOONE DETECTOR IN THE NUMI BEAM

Detection of electron neutrino appearance is the process by which modern neutrino experiments seek to answer the open questions in neutrino physics: CP-violation in the neutrino sector, the neutrino mass ordering, and sterile neutrino oscillations. To date, only three measurements of electron neutrino cross sections have been performed. The analysis presented in this thesis describes the extraction of the first charged-current inclusive $\nu_e$ + $\bar{\nu}_e$ cross section on argon. This calculation was performed with data collected by the MicroBooNE liquid argon time projection chamber using neutrinos from the Neutrino Main Injector (NuMI) beam located at the Fermi National Accelerator Laboratory. Extraction of this cross section is enabled by the first fully-automated inclusive selection of $\nu_e$ + $\bar{\nu}_e$ charged-current interactions in a liquid argon time projection chamber, which provided the largest sample of $\nu_e$ + $\bar{\nu}_e$ charged-current interactions ever observed in liquid argon. The selection utilises the signature capabilities of liquid argon, such as distinguishing electron-like and photon-like electromagnetic showers using their charge-deposition profiles (dE/dx). The evaluation of systematic effects influencing the final cross section, including detector simulation and flux simulation uncertainties, which have been applied for the first time to a MicroBooNE analysis using neutrinos from the NuMI beam, is also presented. The total impact of all systematic and statistical effects results in a 38.44\% uncertainty on the flux integrated cross section, giving $\sigma_{\nu_{e}~+~\bar{\nu}_e} = 4.67 \pm 1.01 \textrm{(stat)} \pm 1.48 \textrm{(sys)} \times 10^{-39}$ cm$^{2}$ per nucleon as the final result, which is in agreement with theoretical predictions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Intrabeam Stripping of H- Ions in the JLEIC Ion Linac with PyORBIT

Jefferson Lab is designing an electron-ion collider (JLEIC) to meet the experimental needs of the nuclear physics community. In JLEIC, a potential mechanism for beam loss is intrabeam stripping of the H- ions in the linear accelerator (linac). As the ions interact with each other, there is a chance that electrons will be stripped from the ions. This creates neutral particles that are unaffected by the electromagnetic fields and are thus lost. This project determined whether intrabeam stripping is a relevant form of beam loss for JLEIC. The pyORBIT code was modified to simulate the beam dynamics of the JLEIC linac. Then plots were created of relativistic velocity to determine the likelihood of intrabeam stripping. From these plots, the relativistic velocity values of the ion beam were found to be similar to values from previous studies on other linacs; however, the calculated average power of JLEIC is significantly lower than the powers of other linacs. Previous predictions have shown that intrabeam stripping is negligible below a certain average power value. Our value for average power was many orders of magnitude below this average power value and thus confirmed that intrabeam stripping of the H- ions will have negligible effects on the amount of beam loss in JLEIC ion linac.

Sy, Amy↗
DOE OSTI2024

Calibration of the DUNE Far Detector Using Cosmic-ray Muon Events

The Deep Underground Neutrino Experiment (DUNE) aims to set new limits on parameters associated with neutrino oscillations, neutrino astrophysics, and beyond the Standard Model (SM) searches such as nucleon decay. DUNE will quantify the magnitude of CP violation in the lepton sector, and determine the neutrino mass ordering. These benefit highly from the large target mass and excellent imaging, tracking, and particle identification capabilities of Liquid Argon Time Projection Chambers (LArTPCs). Detector calibration is essential to make precise physics measurements. For instance, accurate energy reconstruction is necessary for measuring many of the aforementioned quantities with the precision required for discovering new physics and fully exploiting the capabilities of the detector. Cosmic muons are a freely available natural source of calorimetric data and can be used for calibrating various detector parameters. This thesis provides an analysis of simulated cosmic-ray muon events generated with the Muon Simulation Underground (MUSUN) generator in the DUNE horizontal drift (HD) far detector (FD). The study focuses on analysing the energy and angular distribution of various classes of muon events, as well as characterising the different particles produced by cosmic muon interactions. The analysis of π0 → 2γ events within the cosmic-ray muon sample is presented in this thesis with a detailed study of reconstructing electromagnetic showers. The π0 mass is reconstructed within the DUNE FD, yielding a value of (136 ± 7) MeV/c2. Additionally, the thesis introduces methods for dE/dx calibration using simulated and reconstructed muon tracks. A calibration constant Ccal = (5.469 ± 0.003) × 10−3 ADC × tick/e is obtained through a model-dependent calibration process, where 1 tick corresponds to 500 ns of sampling time of an ADC. Furthermore, a calibration technique is presented, demonstrating precise translation from dQ/dx to dE/dx. This calibration method is applied to stopping muons, charged pions, and protons in the DUNE FD, addressing the measurement of energy loss in the detector volume. These are important calibrations of the DUNE FD and will contribute to achieving the exciting physics goals of the experiment.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2015

Two-dimensional electromagnetic quantum-hydrodynamic simulations of isochoric heating of a solid target by proton beams

Isochoric heating of an aluminum target by proton beams has been studied with a two-dimensional self-consistent electromagnetic quantum-hydrodynamic model, including the nonlinear quantum effects. It is shown that most protons deposit their energy within several micrometers near the surface, and the aluminum metal target is heated up to several electron volts in tens of Mbar pressure regime within one picosecond. Comparison between electrostatic and electromagnetic cases shows that the strength of electromagnetic field is much smaller than that of the electrostatic field at initial stage but increases more rapidly and becomes larger at later time. The results show that the time evolution of electric field has a significant influence on the interaction of intense beams with a solid target, while the effect of the self-magnetic field is small for non-relativistic beams considered here.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗