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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 487 records · Page 27
All sourcesNASA NTRSDOE OSTI
DOE OSTI2011

High resolution field effect sensing of ferroelectric charges.

Nanoscale manipulation of surface charges and their imaging are essential for understanding local electronic behaviors of polar materials and advanced electronic devices. Electrostatic force microscopy and Kelvin probe force microscopy have been extensively used to probe and image local surface charges responsible for electrodynamics and transport phenomena. However, they rely on the weak electric force modulation of cantilever that limits both spatial and temporal resolutions. Here we present a field effect transistor embedded probe that can directly image surface charges on a length scale of 25 nm and a time scale of less than 125 {micro}s. On the basis of the calculation of net surface charges in a 25 nm diameter ferroelectric domain, we could estimate the charge density resolution to be as low as 0.08 {micro}C/cm{sup 2}, which is equivalent to 1/20 electron per nanometer square at room temperature.

36 MATERIALS SCIENCE↗
DOE OSTI2010

Dynamic Phase Transitions In The Spin-2 Ising System Under An Oscillating Magnetic Field Within The Effective-Field Theory

The dynamic phase transitions are studied in the spin-2 Ising model under a time-dependent oscillating magnetic field by using the effective-field theory with correlations. The effective-field dynamic equation is derived by employing the Glauber transition rates and the phases in the system are obtained by solving this dynamic equation. The nature (first- or second-order) of the dynamic phase transition is characterized by investigating the thermal behavior of the dynamic order parameter and the dynamic phase transition temperatures are obtained. The dynamic phase diagrams are presented in (T/zJ, h/zJ) plane.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Linear Quadratic Mean Field Type Control and Mean Field Games with Common Noise, with Application to Production of an Exhaustible Resource

We study a general linear quadratic mean field type control problem and connect it to mean field games of a similar type. The solution is given both in terms of a forward/backward system of stochastic differential equations and by a pair of Riccati equations. In certain cases, the solution to the mean field type control is also the equilibrium strategy for a class of mean field games. We use this fact to study an economic model of production of exhaustible resources.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Enhanced redox conductivity and enriched Geobacteraceae of exoelectrogenic biofilms in response to static magnetic field

A possible approach to enhance the performance of microbial electrochemical system such as microbial fuel cells is to increase the conductivity of catalytic biofilms and thereby the direct extracellular electron transfer within the biofilms and from the electrode. In the present study, we evaluated the impact of static low-intensity magnetic field on the anodic biofilms in microbial fuel cells (MFCs). Here, results demonstrated that the application of a low-intensity magnetic field (105 and 150 mT) can significantly shorten the startup time and enhance the overall performance of single-chamber MFCs in terms of current density (300%) and power density (150%). In situ conductance evaluation indicated that short-term application of magnetic field can increase biofilm conductivity, although the long-term enhancements were likely results of increased conductivity of the anodic biofilms associated with enriched population of Geobacteraceae. The peak-manner response of conductivity over gate potentials and the positive response of mature biofilm conductance to low intensity of magnetic field support the redox conduction model of the conductive exoelectrogenic biofilms.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2013

Causal signal transmission by quantum fields. VI: The Lorentz condition and Maxwell’s equations for fluctuations of the electromagnetic field

The general structure of electromagnetic interactions in the so-called response representation of quantum electrodynamics (QED) is analysed. A formal solution to the general quantum problem of the electromagnetic field interacting with matter is found. Independently, a formal solution to the corresponding problem in classical stochastic electrodynamics (CSED) is constructed. CSED and QED differ only in the replacement of stochastic averages of c-number fields and currents by time-normal averages of the corresponding Heisenberg operators. All relations of QED connecting quantum field to quantum current lack Planck’s constant, and thus coincide with their counterparts in CSED. In Feynman’s terms, one encounters complete disentanglement of the potential and current operators in response picture. Based on this parallelism between QED and CSED, it is natural to expect validity of the Lorentz condition and Maxwell’s equations for the time-normal averages of the potential and current. Things however turn out to be more complicated. Maxwell’s equations under the time-normal ordering can only be demonstrated subject to cancellation of the so-called Schwinger terms by gauge-invariant regularisations. We presume this pattern to be general, formulating this as “commutativity conjecture”. Consistency of the latter with the Heisenberg uncertainty principle is discussed. -- Highlights: •The general structure of interaction in quantum electrodynamics (QED) is analysed. •A detailed parallelism between QED and classical stochastic electrodynamics is shown. •Validity of Maxwell’s equations for fluctuations of the field is discussed. •This validity turns out to be in essence a renormalisation postulate.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Phase-field simulation of irradiated metals Part 1: Void kinetics.

We present a phase-field model of void formation and evolution in irradiated metals by spatially and temporally evolving vacancy and self-interstitial concentration fields. By incorporating a coupled set of Cahn-Hilliard and Allen-Cahn equations, the model captures the processes of point defect generation and recombination, annihilation of defects at sinks, as well as void nucleation and growth in the presence of grain boundaries. Illustrative results are presented that characterize the rate of void growth or shrinkage due to supersaturated vacancy or interstitial concentrations, void nucleation and growth kinetics due to cascade-induced defect production, as well as void denuded and peak zones adjacent to grain boundaries.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

Evolution of microstructures in radiation fields using a coupled binary-collision Monte Carlo phase field approach

The simulation of radiation effects in materials broadly falls into two categories. At short time and length scales lies the modeling of primary radiation damage, such as point defect creation, energy deposition, and ballistic mixing. This is followed by the modeling at longer time scales of thermally activated microstructure evolution and defect reactions, such as recombination, clustering, and coarsening. The binary collision Monte Carlo method is an established, numerically efficient method for the computation of primary radiation damage. Conversely, the phase field method is a state of the art method for microstructure evolution on longer time and length scales. Here we present a concurrent coupling of these two methods, overcoming the difference between the discrete object Monte Carlo paradigm for primary radiation damage and the continuum field variable approach for microstructure evolution. The coupling is bidirectional, in which the microstructure evolution in the MOOSE finite element frame- work provides the spatial scattering data set for the charged particle trans- port and receives point defect, mass transport, and heat source terms from the simulated collision cascades that contribute to the field variable evolution. The concurrent coupling scheme is implemented in the code Magpie and demonstrated by investigating patterning for a model irradiated immiscible binary alloy. The results from the coupled binary collision Monte Carlo/phase field simulations reproduce the results of analytical models for phase separation, phase mixing, and patterning, supporting the approach and indicating its utility for modeling real materials systems.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Temperature-responsive smart tracers for field-measurement of inter-well thermal evolution: Heterogeneous kinetics and field demonstration

Temperature-responsive smart tracers enable advanced warning of a “premature thermal breakthrough” and may therefore improve reservoir management and reduce financial risk. A successful calculation of inter-well fluid temperatures requires that temperature-dependent kinetics are known, which typically result from homogeneous batch reactor experiments. However, recent meso-scale field experiments at the Altona Field Laboratory involving fluid flow in a discretely-fractured reservoir suggest that silica-fluid interfaces may accelerate hydrolysis kinetics. Here, the Arrhenius parameters of phenyl acetate hydrolysis are investigated under heterogeneous reaction conditions in packed-bed column experiments. The breakthrough curve of the reaction product is compared to an inert reference tracer (carbon-cored nanoparticles). Temperatures experienced during field testing ranging from 10 to 40 °C were studied using a phosphate buffer solution to maintain a near-neutral pH, as found in the reservoir. The empirically-determined pre-exponential factor and activation energy values are subsequently used in a first-order kinetic model to improve calculations of effective reservoir temperatures for these meso-scale field tests. Here, the results suggest that hydrolysis reactions can directly monitor inter-well reservoir temperatures, but only if the influence of solid-fluid interactions are carefully accounted for.

15 GEOTHERMAL ENERGY↗
DOE OSTI2023

Quantum Sensing of Electric Fields Using Spin-Correlated Radical Ion Pairs

Quantum sensing affords the possibility of using quantum entanglement to probe electromagnetic fields with exquisite sensitivity. In this work, we show that a photogenerated spin-correlated radical ion pair (SCRP) can be used to sense an electric field change created at one radical ion of the pair using molecular recognition. The SCRP is generated within a covalent donor–chromophore–acceptor system PXX–PMI–NDI, 1, where PXX = peri-xanthenoxanthene, PMI = 1,6-bis(p-t-butylphenoxy)perylene-3,4-dicarboximide, and NDI = naphthalene-1,8:4,5-bis(dicarboximide). The electron-rich PXX donor in 1 acts as a guest molecule that can be encapsulated selectively by a tetracationic cyclophane ExBox4+ host to give a supramolecular complex 1 ⊂ ExBox 4+ . Selective photoexcitation of the PMI chromophore results in ultrafast generation of the PXX •+ –PMI–NDI •– SCRP. When PXX is encapsulated by ExBox 4+ , the cyclophane generates an electric field that repels the positive charge on PXX •+ within PXX •+ –PMI–NDI •– , reducing the SCRP distance, i.e., the distance between the centers-of-charge on the donor and acceptor. Pulse-EPR measurements are used to measure the coherent oscillations created primarily by the electron–electron dipolar coupling in the SCRP, which yields the distance between the two charges (spins) of PXX •+ –PMI–NDI •– . Here, the experimental results show that the distance between PXX •+ and NDI •– decreases when ExBox 4+ encapsulates PXX •+ , which demonstrates that the SCRP can function as a quantum sensor to detect electric field changes in the vicinity of the radical ions.

Anions↗
DOE OSTI2018

Energy Conversion by Parallel Electric Fields During Guide Field Reconnection in Scaled Laboratory and Space Experiments

Here, we present direct and scaled comparisons between laboratory and in situ space observations of magnetic reconnection with a guide field, comparing results from the Magnetospheric Multiscale Mission and the Magnetic Reconnection eXperiment (MRX). While Magnetospheric Multiscale Mission observations obtain high–resolution and fully kinetic data, MRX observations fully cover the 2–D reconnection plane near the current sheet, removing uncertainties in situating the measurements compared to the reconnection region. Through scaling transformations, we show a quantitative agreement in magnetic field and current density profiles, which agree within a factor of 2 from each other. The introduction of the guide field causes the energy conversion J·E in the current sheet to be dominated by J || E || in both cases. However, parallel electric fields reported by recent spacecraft crossings are significantly (5–10 times) larger than values obtained on MRX, highlighting an important issue for understanding energy conversion by reconnection.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2022

Generation of a Strong Parallel Electric Field and Embedded Electron Jet in the Exhaust of Moderate Guide Field Reconnection

Abstract Magnetospheric Multiscale observed an extended current layer concurrent with a strong parallel electric field. The current layer is embedded in the reconnection exhaust and is consistent with an extended magnetized jet expected in roughly symmetric moderate guide field reconnection. The strong parallel electric field observed at the jet balances a strong gradient in the parallel electron pressure caused by a transition between magnetized electrons with T e ‖ > T e ⊥ on one side of the jet and demagnetized, roughly isotropic electrons across the thin current layer. Simulation results show how this transition can occur and how the associated electron pressure gradients in Ohm's law balance the parallel electric field.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Upper critical field and Kondo effects in Fe(Te 0.9 Se 0.1 ) thin films by pulsed field measurements

The transition temperatures of epitaxial films of Fe(Te 0:9 Se 0:1 ) are remarkably insensitive to applied magnetic field, leading to predictions of upper critical fields B c2 (T = 0) in excess of 100 T. Using pulsed magnetic fields, we find B c2 (0) to be on the order of 45 T, similar to values in bulk material and still in excess of the paramagnetic limit. The same films show strong magnetoresistance in fields above B c2 (T), consistent with the observed Kondo minimum seen above T c . Fits to the temperature dependence in the context of the WHH model, using the experimental value of the Maki parameter, require an effective spin-orbit relaxation parameter of order unity. Lastly, we suggest that Kondo localization plays a similar role to spin-orbit pair breaking in making WHH fits to the data.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2013

Field-dependent critical state of high-Tc superconducting strip simultaneously exposed to transport current and perpendicular magnetic field

We present an exact analytical approach for arbitrary field-dependent critical state of high-T{sub c} superconducting strip with transport current. The sheet current and flux-density profiles are derived by solving the integral equations, which agree with experiments quite well. For small transport current, the approximate explicit expressions of sheet current, flux-density and penetration depth for the Kim model are derived based on the mean value theorem for integration. We also extend the results to the field-dependent critical state of superconducting strip in the simultaneous presence of applied field and transport current. The sheet current distributions calculated by the Kim model agree with experiments better than that by the Bean model. Moreover, the lines in the I{sub a}-B{sub a} plane for the Kim model are not monotonic, which is quite different from that the Bean model. The results reveal that the maximum transport current in thin superconducting strip will decrease with increasing applied field which vanishes for the Bean model. The results of this paper are useful to calculate ac susceptibility and ac loss.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Laser ion source with solenoid field

Pulse length extension of highly charged ion beam generated from a laser ion source is experimentally demonstrated. In this study, the laser ion source (LIS) has been recognized as one of the most powerful heavy ion source. However, it was difficult to provide long pulse beams. By applying a solenoid field (90 mT, 1 m) at plasma drifting section, a pulse length of carbon ion beam reached 3.2 μs which was 4.4 times longer than the width from a conventional LIS. The particle number of carbon ions accelerated by a radio frequency quadrupole linear accelerator was 1.2 × 10 11 , which was provided by a single 1 J Nd-YAG laser shot. A laser ion source with solenoid field could be used in a next generation heavy ion accelerator.

43 PARTICLE ACCELERATORS↗
DOE OSTI2014

Fatigue of extracted lead zirconate titanate multilayer actuators under unipolar high field electric cycling

Testing of large prototype lead zirconate titanate (PZT) stacks presents substantial technical challenges to electronic testing systems, so an alternative approach that uses subunits extracted from prototypes has been pursued. Extracted 10-layer and 20-layer plate specimens were subjected to an electric cycle test under an electric field of 3.0/0.0 kV/mm, 100 Hz to 10{sup 8} cycles. The effects of measurement field level and stack size (number of PZT layers) on the fatigue responses of piezoelectric and dielectric coefficients were observed. On-line monitoring permitted examination of the fatigue response of the PZT stacks. The fatigue rate (based on on-line monitoring) and the fatigue index (based on the conductance spectrum from impedance measurement or small signal measurement) were developed to quantify the fatigue status of the PZT stacks. The controlling fatigue mechanism was analyzed against the fatigue observations. The data presented can serve as input to design optimization of PZT stacks and to operation optimization in critical applications, such as piezoelectric fuel injectors in heavy-duty diesel engines.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

Spectroscopic measurement of high-frequency electric fields in the interaction of explosive debris plasma with magnetized background plasma

The collision-less transfer of momentum and energy from explosive debris plasma to magnetized background plasma is a salient feature of various astrophysical and space environments. While much theoretical and computational work has investigated collision-less coupling mechanisms and relevant parameters, an experimental validation of the results demands the measurement of the complex, collective electric fields associated with debris-background plasma interaction. Emission spectroscopy offers a non-interfering diagnostic of electric fields via the Stark effect. A unique experiment at the University of California, Los Angeles, that combines the Large Plasma Device (LAPD) and the Phoenix laser facility has investigated the marginally super-Alfvénic, quasi-perpendicular expansion of a laser-produced carbon (C) debris plasma through a preformed, magnetized helium (He) background plasma via emission spectroscopy. Spectral profiles of the He II 468.6 nm line measured at the maximum extent of the diamagnetic cavity are observed to intensify, broaden, and develop equally spaced modulations in response to the explosive C debris, indicative of an energetic electron population and strong oscillatory electric fields. The profiles are analyzed via time-dependent Stark effect models corresponding to single-mode and multi-mode monochromatic (single frequency) electric fields, yielding temporally resolved magnitudes and frequencies. The proximity of the measured frequencies to the expected electron plasma frequency suggests the development of the electron beam-plasma instability, and a simple saturation model demonstrates that the measured magnitudes are feasible provided that a sufficiently fast electron population is generated during C debris–He background interaction. Potential sources of the fast electrons, which likely correspond to collision-less coupling mechanisms, are briefly considered.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2015

Two-photon absorption induced by electric field gradient of optical near-field and its application to photolithography

An electric field gradient is an inherent property of the optical near-field (ONF). We investigated its effect on electron excitation in a quantum dot via model calculations combining a density matrix formalism and a classical Lorentz model. The electric field gradient of the ONF was found to cause two-photon absorption by an unusual mechanism. Furthermore, the absorption exhibits a nonmonotonic dependence on the spatial arrangement of the nanosystem, completely different from that of conventional two-photon absorption induced by an intense electric field. The present two-photon absorption process was verified in a previous experimental observation by reinterpreting the results of ONF photolithography.

77 NANOSCIENCE AND NANOTECHNOLOGY↗