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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 829 records · Page 46
All sourcesNASA NTRSDOE OSTI
DOE OSTI2011

A Vlasov-Fokker-Planck code for high energy density physics

OSHUN is a parallel relativistic 2D3P Vlasov-Fokker-Planck code, developed primarily to study electron transport and instabilities pertaining to laser-produced-including laser-fusion-plasmas. It incorporates a spherical harmonic expansion of the electron distribution function, where the number of terms is an input parameter that determines the angular resolution in momentum-space. The algorithm employs the full 3D electromagnetic fields and a rigorous linearized Fokker-Planck collision operator. The numerical scheme conserves energy and number density. This enables simulations for plasmas with temperatures from MeV down to a few eV and densities from less than critical to more than solid. Kinetic phenomena as well as electron transport physics can be recovered accurately and efficiently.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Human Exposure Analysis to EMFs from Ground Assembly of a WPT System during the Vehicle's Non-Attendance: Preprint

This paper presents assessment analysis for the human exposure to electromagnetic fields from the ground assembly (GA) of the wireless power transfer (WPT) before alignment, while the vehicle does not exist over the pad. A 25 kW WPT system from Momentum Dynamics is analyzed using finite-element software during the low power alignment operation. The same system is installed at the National Renewable Energy Laboratory (NREL) and tested at the same conditions. Good agreement is observed between the results. In addition, both results comply with standard exposure limits.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2017

Response theory of the ergodic many-body delocalized phase: Keldysh Finkel’stein sigma models and the 10-fold way

We derive the finite temperature Keldysh response theory for interacting fermions in the presence of quenched short-ranged disorder, as applicable to any of the 10 Altland–Zirnbauer classes in an Anderson delocalized phase with at least a U(1) continuous symmetry. In this formulation of the interacting Finkel’stein nonlinear sigma model, the statistics of one-body wave functions are encoded by the constrained matrix field, while physical correlations follow from the hydrodynamic density or spin response field, which decouples the interactions. Integrating out the matrix field first, we obtain weak (anti) localization and Altshuler–Aronov quantum conductance corrections from the hydrodynamic response function. This procedure automatically incorporates the correct infrared cutoff physics, and in particular gives the Altshuler–Aronov–Khmelnitsky (AAK) equations for dephasing of weak (anti)localization due to electron–electron collisions. We explicate the method by deriving known quantumcorrections in two dimensions for the symplectic metal class AII, as well as the spin-SU(2) invariant superconductor classes C and CI. We show that quantum conductance corrections due to the special modes at zero energy in nonstandard classes are automatically cut off by temperature, as previously expected, while the Wigner–Dyson class Cooperon modes that persist to all energies are cut by dephasing. We also show that for short-ranged interactions, the standard self-consistent solution for the dephasing rate is equivalent to a particular summation of diagrams via the self-consistent Born approximation. This should be compared to the corresponding AAK solution for long-ranged Coulomb interactions, which exploits the Markovian noise correlations induced by thermal fluctuations of the electromagnetic field. We discuss prospects for exploring the many-body localization transition as a dephasing catastrophe in short-range interacting models, as encountered by approaching from the ergodic side. - Highlights: • The Keldysh response theory for disordered, interacting fermions is derived. • The theory applies to any Altland–Zirnbauer class with at least a U(1) symmetry. • The correct infrared physics at finite temperature is automatically incorporated. • The Altshuler–Aronov–Khmelnitsky equations for dephasing are systematically derived. • A strategy to explore the MBL transition as a dephasing catastrophe is proposed.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

Covariant formulation of spatially non-symmetric kinetic equilibria in magnetized astrophysical plasmas

Astrophysical plasmas in the surrounding of compact objects and subject to intense gravitational and electromagnetic fields are believed to give rise to relativistic regimes. Theoretical and observational evidences suggest that magnetized plasmas of this type are collisionless and can persist for long times (e.g., with respect to a distant observer, coordinate, time), while exhibiting geometrical structures characterized by the absence of well-defined spatial symmetries. In this paper, the problem is posed whether such configurations can correspond to some kind of kinetic equilibrium. The issue is addressed from a theoretical perspective in the framework of a covariant Vlasov statistical description, which relies on the method of invariants. For this purpose, a systematic covariant variational formulation of gyrokinetic theory is developed, which holds without requiring any symmetry condition on the background fields. As a result, an asymptotic representation of the relativistic particle magnetic moment is obtained from its formal exact solution, in terms of a suitably defined invariant series expansion parameter (perturbative representation). On such a basis, it is shown that spatially non-symmetric kinetic equilibria can actually be determined, an example being provided by Gaussian-like distributions. As an application, the physical mechanisms related to the occurrence of a non-vanishing equilibrium fluid 4-flow are investigated.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2016

A Review of the Environmental Impacts for Marine and Hydrokinetic Projects to Inform Regulatory Permitting: Summary Findings from the 2015 Workshop on Marine and Hydrokinetic Technologies, Washington, D.C.

In 2014 and 2015, the U.S. Department of Energy initiated efforts to develop and implement technology- and application-focused marine and hydrokinetic (MHK) workshops to share the global experience and knowledge base on evolving MHK technologies, observed and not-observed impacts, monitoring and measurement methods, and regulatory needs. The resulting MHK Regulator Workshops engaged resource managers and other decision makers at key regulatory organizations, scientists, researchers, facilitators, and technical experts and provided an opportunity to examine the risks of single-device and small-scale deployments, explore what can be learned and observed from single devices and small-scale arrays, and consider requirements for projects at varying scales of deployment. Experts and stakeholders identified key remaining information gaps. Initial discussions focused on differentiating between monitoring required for single or small-scale deployments and MHK impact research that, although important, goes beyond what is feasible or should be needed to meet specific project regulatory requirements but is appropriate for broader research and development. Four areas of identified potential environmental impacts provided the focus for the workshop: acoustic output impacts, electromagnetic field (EMF) emissions, physical interactions, and environmental effects of MHK energy development on the physical environment. Discussions also focused on the regulatory process and experience, adaptive management, industry drivers, and lessons that can be learned from the wind energy industry. The discussion was set in the context of the types of MHK technologies that are currently proposed or planned in the United States. All presentations and the following discussions are summarized in this document.

16 TIDAL AND WAVE POWER↗
DOE OSTI2016

Intramode wave packet in a thin left-handed film with the spectrum near the frequency of the zero group velocity

We consider the frequency dependence of propagation constants (phase dispersion) and of the spatial distribution of the electromagnetic field (shape dispersion) of guided optical TE modes in a thin left-handed film. It is shown that the spatiotemporal transformation of narrow-band intramode wave packets with the spectrum adjacent to the frequency of the zero group velocity is caused by the dispersion of both types. The propagation velocity of the power carried by such wave packets is significantly lower than the group velocity of light in a bulk left-handed metamaterial. (metamaterials)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Comparison of natural and forced amplification regimes in plasma-based soft-x-ray lasers seeded by high-order harmonics

The amplification of high-order harmonics (HOH) in a plasma-based amplifier is a multiscale, temporal phenomenon that couples plasma hydrodynamics, atomic processes, and HOH electromagnetic fields. We use a one-dimensional, time-dependent Maxwell-Bloch code to compare the natural amplification regime and another regime where plasma polarization is constantly forced by the HOH. In this regime, a 10-MW (i.e., 100 times higher than current seeded soft x-ray laser power), 1.5-{mu}J, 140-fs pulse free from the parasitic temporal structures appearing on the natural amplification regime can be obtained.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2011

Dissipatively driven entanglement of two macroscopic atomic ensembles

Up to now, the lifetime of experimentally demonstrated entangled states has been limited due to their fragility under decoherence and dissipation. Therefore, they are created under strict isolation conditions. In contrast, new approaches harness the coupling of the system to the environment, which drives the system into the desired state. Following these ideas, we present a robust method for generating steady-state entanglement between two distant atomic ensembles. The proposed scheme relies on the interaction of the two atomic systems with the common vacuum modes of an electromagnetic field which act as an engineered environment. We develop the theoretical framework for two-level systems, including dipole-dipole interactions, and complement it by considering its implementation in multilevel ground states. Based on these results, the realization of entanglement generation by engineered dissipation has been experimentally demonstrated [H. Krauter, C. A. Muschik, K. Jensen, W. Wasilewski, J. M. Petersen, J. I. Cirac, and E. S. Polzik, e-print arXiv:1006.4344].

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2013

Risk assessment and management of radiofrequency radiation exposure

Radiofrequency radiation (RFR) industry managers, occupational physicians, security department, and other practitioners must be advised on the basic of biophysics and the health effects of RF electromagnetic fields so as to guide the management of exposure. Information on biophysics of RFR and biological/heath effects is derived from standard texts, literature and clinical experiences. Emergency treatment and ongoing care is outlined, with clinical approach integrating the circumstances of exposure and the patient's symptoms. Experimental risk assessment model in RFR chronic exposure is proposed. Planning for assessment and monitoring exposure, ongoing care, safety measures and work protection are outlining the proper management.

63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTAN↗
DOE OSTI2015

Highly directive Fabry-Perot leaky-wave nanoantennas based on optical partially reflective surfaces

Nanoantennas enhance the conversion between highly localized electromagnetic fields and far-field radiation. Here, we investigate the response of a nano-patch partially reflective surface backed with a silver mirror to an optical source embedded at the centre of the structure. Using full wave simulations, we demonstrate a two orders of magnitude increased directivity compared to the isotropic radiator, 50% power confinement to a 13.8° width beam and a ±16 nm bandwidth. Our antenna does not rely on plasmonic phenomena thus reducing non-radiative losses and conserving source coherence.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Cauchy-Schwarz characterization of tripartite quantum correlations in an optical parametric oscillator

We analyze the three-mode correlation properties of the electromagnetic field in a optical parametric oscillator below-threshold. We employ a perturbative expansion of the Ito equations derived from the positive-P representation of the density matrix. Using the generalized Cauchy-Schwarz inequality, we investigate the genuine quantum nature of the triple correlations between the interacting fields, since in this case continuous-variable entanglement is not detected by the van Loock-Furusawa criterion [Phys. Rev. A 67, 052315 (2003)]. Although not being a necessary condition, these triple correlations are sufficient evidence of tripartite entanglement. Of course, our characterization of the quantum correlations is applicable to non-Gaussian states, which we show to be the case of the optical parametric oscillator below-threshold, provided nonlinear quantum fluctuations are properly taken into account.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Erasing the traces of classical mechanics in ionization of H{sub 2} by quantum interferences

The single ionization of hydrogen molecules by fast electron impact is studied theoretically for transitions from the ground (gerade) state to final ground (gerade) and first-excited (ungerade) states of H{sub 2}{sup +}. It is shown that under definite conditions and for particular orientations of the molecule, the main physical features of the ionization reaction, which are the binary and recoil peaks usually associated with classical mechanisms, are completely erased by quantum interference effects that resemble the ones predicted previously for photoionization reactions. However, these new effects cannot be derived from photoionization results, as the electromagnetic field cannot transfer momentum. In addition, it is found that the emission spectra of transitions leading to the final gerade and ungerade states of the H{sub 2}{sup +} residual target are analogous in certain cases to the patterns of two sources emitting waves in phase or antiphase, respectively. Finally, we show how an average of the emission from randomly oriented molecules produces a binary peak at the classical expected position, in agreement with experiments.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Radiative Double Electron Capture Observed During O{sup 8+}+C Collisions At 38 Mev

Radiative double electron capture (RDEC) is a one-step process during which two free (or quasifree) target electrons are captured into bound states of the projectile, e.g., into an empty K-shell, and the energy excess is released as a single photon. This process can be considered as a time inverse of double photoionization. As photon interacts with one electron only, RDEC is due to electron-electron interaction. Moreover, RDEC is investigated during bare ion-atom collisions and, unlike double photoionization, it does not have background from spectator electrons. Thus, RDEC may be the simplest, clean tool for exploration of the electron-electron interaction in the presence of electromagnetic fields generated during ion-atom collisions. Recently, an experiment dedicated to the RDEC process with 38 MeV O{sup 8+} ions colliding with a carbon foil was conducted at Western Michigan University using the tandem Van de Graaff accelerator. This experiment confirmed that the observation of such process is possible and allowed for estimation of the RDEC cross section of 3.2(1.9) b, which is significantly greater than the theoretically predicted value of 0.15 b.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2011

Comment on ''Temperature dependence of the Casimir force for lossy bulk media''

Recently Yampol'skii et al.[Phys. Rev. A 82, 032511 (2010)] advocated that Lifshitz theory is not applicable when the characteristic wavelength of the fluctuating electromagnetic field, responsible for the thermal correction to the Casimir force, is larger than the size of the metal test bodies. It was claimed that this is the case in experiments which exclude Lifshitz theory combined with the Drude model. We calculate the wavelengths of the evanescent waves making the dominant contribution to the thermal correction and we find that they are much smaller than the sizes of the test bodies. The opposite conclusion obtained by the authors arose from confusion between propagating and evanescent waves.

36 MATERIALS SCIENCE↗
DOE OSTI2011

Analysis of spatial modes in half-disk lasers based on AlGaAsSb/InGaAsSb quantum well nanoheterostructures

Spectral and spatial distributions of the emission of whispering-gallery-mode (WGM) lasers with a half-disk cavity have been studied. Up to 13 broad lobes with different intensities, subdivided into order-of-magnitude narrower lobes, are distinguished in the spatial distribution. The emission spectrum is nearly single-mode. A mathematical model of the electromagnetic field distribution in a WGM laser is suggested, and the radiation pattern of the laser is calculated. It is shown that each lobe corresponds to its own stable radial spatial mode. The highest emission intensity is provided not by the peripheral mode itself, but by the next-closest mode, which presumably exhibits the lowest optical loss. The predominance of a single spatial mode results in a nearly single-mode emission spectrum being observed.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Kinetic Alfven wave in the presence of kappa distribution function in plasma sheet boundary layer

The particle aspect approach is adopted to investigate the trajectories of charged particles in the electromagnetic field of kinetic Alfven wave. Expressions are found for the dispersion relation, damping/growth rate and associated currents in the presence of kappa distribution function. Kinetic effect of electrons and ions are included to study kinetic Alfven wave because both are important in the transition region. It is found that the ratio β of electron thermal energy density to magnetic field energy density and the ratio of ion to electron thermal temperature (T{sub i}/T{sub e}), and kappa distribution function affect the dispersion relation, damping/growth rate and associated currents in both cases(warm and cold electron limit).The treatment of kinetic Alfven wave instability is based on assumption that the plasma consist of resonant and non resonant particles. The resonant particles participate in an energy exchange process, whereas the non resonant particles support the oscillatory motion of the wave.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2018

Variational formulation of classical and quantum models for intense laser pulse propagation

Highlights: •We consider the theoretical description of intense laser pulses propagating through gases. •We derived reduced models using Lagrangian and Hamiltonian formulations. •We obtain models where the atomic electrons are treated classically or quantum-mechanically. •We derive a number of conserved quantities of the reduced models. -- Abstract: We consider the theoretical description of intense laser pulses propagating through gases. Starting from a first-principles description of both the electromagnetic field and the electron motion within the gas atoms, we derive a hierarchy of reduced models. We obtain a parallel set of models, where the atomic electrons are treated classically on the one hand, and quantum-mechanically on the other. By working consistently in either a Lagrangian formulation or a Hamiltonian formulation, we ensure that our reduced models preserve the variational structure of the parent models. Taking advantage of the Hamiltonian formulation, we deduce a number of conserved quantities of the reduced models.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

Linear Light Amplifier and Amplification of N-Photon States

We consider a linear quantum amplifier consisting of NA two-level atoms and study the problem of amplification of N-photon states. The N-photon states are associated with N-quantum states of the harmonic oscillator. We show that the process of interaction of the electromagnetic field with atoms can be associated with some transformation of the phase space and functions defined on this phase space. We consider the Husimi functions QN(q, p) of N-quantum states of the harmonic oscillator, which are defined on the phase space, investigate transformation of these functions, and find an explicit form of the density matrix of the amplified N-photon state. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.

60 APPLIED LIFE SCIENCES↗