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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Efficient regime of electromagnetic emission in a plasma with counterstreaming electron beams

Efficiency of electromagnetic emission produced in a magnetized plasma with counterstreaming electron beams was investigated using both the linear kinetic theory and particle-in-cell simulations. We calculated the growth rate of the beam-plasma instability taking into account both kinetic and relativistic effects and showed that there exists a regime in which transversely propagating electromagnetic waves can be generated by the coupling of the most unstable oblique beam-driven modes. It was confirmed by numerical simulations that such a tune-up of system parameters for a specific nonlinear process can lead to a substantial increase in electromagnetic emission efficiency. It was found that electromagnetic radiation emerging from the plasma in such a regime is generated near the harmonics of the pump frequency that is determined by the typical eigenfrequency of the beam-driven modes. It was also shown that the peak emission power can reach 5% of the maximal power lost by beam electrons.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
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 OSTI2016

Electromagnetic fluctuations generated in the boundary layer of laboratory-created ionospheric depletions

Ionospheric depletions, produced by release of attachment chemicals into the ionosphere, were widely investigated and taken as a potential technique for the artificial modification of space weather. In this work, we reported the experimental evidence of spontaneously generated electromagnetic fluctuations in the boundary layer of laboratory-created ionospheric depletions. These depletions were produced by releasing attachment chemicals into the ambient plasmas. Electron density gradients and sheared flows arose in the boundary layer between the ambient and the negative ions plasmas. These generated electromagnetic fluctuations with fundamental frequency f{sub 0} = 70 kHz lie in the lower hybrid frequency range, and the mode propagates with angles smaller than 90° (0.3π–0.4π) relative to the magnetic field. Our results revealed that these observed structures were most likely due to electromagnetic components of the electron-ion hybrid instability. This research demonstrates that electromagnetic fluctuations also can be excited during active release experiments, which should be considered as an essential ingredient in the boundary layer processes of ionospheric depletions.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2016

THz electromagnetic radiation driven by intense relativistic electron beam based on ion focus regime

The simulation study finds that the relativistic electron beam propagating through the plasma background can produce electromagnetic (EM) radiation. With the propagation of the electron beam, the oscillations of the beam electrons in transverse and longitudinal directions have been observed simultaneously, which provides the basis for the electromagnetic radiation. The simulation results clearly show that the electromagnetic radiation frequency can reach up to terahertz (THz) wave band which may result from the filter-like property of plasma background, and the electromagnetic radiation frequency closely depends on the plasma density. To understand the above simulation results physically, the dispersion relation of the beam-plasma system has been derived using the field-matching method, and the dispersion curves show that the slow wave modes can couple with the electron beam effectively in THz wave band, which is an important theoretical evidence of the EM radiation.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2016

Propagation of electromagnetic wave in dusty plasma and the influence of dust size distribution

The effect of charged dust particle and their size distribution on the propagation of electromagnetic wave in a dusty plasma is investigated. It is shown that the additional collision mechanism provided by charged dust particles can significantly alter the electromagnetic properties of a plasma, leading to the appearance of attenuation of electromagnetic wave through dusty plasma. The attenuation coefficient mainly depends on the dust density, radius, and the charge numbers on the dust surface. The results described here will be used to enhance understanding of electromagnetic wave propagation processed in space and laboratory dusty plasma.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2016

Study of a condition for the mode conversion from purely perpendicular electrostatic waves to electromagnetic waves

One of the mechanisms for generating electromagnetic plasma waves (Z-mode and LO-mode) is mode conversion from electrostatic waves into electromagnetic waves in inhomogeneous plasma. Herein, we study a condition required for mode conversion of electrostatic waves propagating purely perpendicular to the ambient magnetic field, by numerically solving the full dispersion relation. An approximate model is derived describing the coupling between electrostatic waves (hot plasma Bernstein mode) and Z-mode waves at the upper hybrid frequency. The model is used to study conditions required for mode conversion from electrostatic waves (electrostatic electron cyclotron harmonic waves, including Bernstein mode) into electromagnetic plasma waves (LO-mode). It is shown that for mode conversion to occur in inhomogeneous plasma, the angle between the boundary surface and the magnetic field vector should be within a specific range. The range of the angle depends on the norm of the k vector of waves at the site of mode conversion in the inhomogeneous region. The present study reveals that inhomogeneity alone is not a sufficient condition for mode conversion from electrostatic waves to electromagnetic plasma waves and that the angle between the magnetic field and the density gradient plays an important role in the conversion process.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2019

Characteristics of quasi-unipolar electromagnetic pulses formed in the interaction of high-power laser pulses with nanoscale targets

A new method is suggested for generating quasi-unipolar electromagnetic IR and terahertz pulses. The method is based on synchronous acceleration of electrons combined to a dense bunch with a charge of up to several tens nanocoulombs, which are forced out from a nanoscale target under an action of a high-power, sharp-leading edge laser pulse. The electromagnetic bunch moving in a field of laser radiation can generate high-power electromagnetic pulses with various spectral composition including terahertz and IR ranges. A physical mechanism underlying the formation of generated quasi-unipolar pulses of electromagnetic radiation is determined and numerically studied. The pulse characteristics are found by numerical simulation, such as amplitude and duration dependences on the angle between the pulse propagation direction and laser beam axis. It is established that in modern laser installations, the amplitudes of quasi-unipolar pulses may reach relativistic values. Reflection of a unipolar pulse from an ideally reflecting surface is numerically analysed. It is shown that the pulse retains its unipolar profile in this case. (paper)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2023

Comparison of Electromagnetic Transient and Phasor Dynamic Simulations: Implications for Inverter Dominated Systems

The simulation of very high shares of inverter-based resources in power systems has begun to draw into question the validity of phasor domain tools in capturing relevant dynamics. Electromagnetic transient simulators can capture the dynamics of power electronics with substantially smaller time steps, but are computationally expensive. This work contrasts the results of phasor domain and electromagnetic transient tools for simulations on a validated model of the Maui power system operating at very high inverter-based resource shares with near zero voltage forming devices. The results show that the phasor domain tool predicts optimistic stability with fewer voltage forming elements on the network, and loses computational stability before the electromagnetic transient tool. As the electromagnet transient model is of the entire system, and system-wide discrepancies are observed, this case study of a physical power system highlights the potential need for system-wide detailed modeling during periods of very high shares of inverter-based resources and few voltage forming devices.

electromagnetic transient-domain↗
DOE OSTI2019

Frequency Dependence of an Electromagnetic Absorption Coefficient in Magnetic Fluid

The samples of water-based magnetic fluid, which contain Fe{sub 3}O{sub 4}–SiO{sub 2} particles with a spherical shape and sizes less than 100 nm, have been obtained. The method based on using a transmission line has been applied to measure the electromagnetic absorption coefficient in the frequency range from 0.1 to 18.0 GHz using a measuring setup based on horn antennas and the cell based on a coplanar transmission line. It has been found that magnetic fluids can be used to produce electromagnetic shields and electromagnetic wave absorbers as well as means to carry out local hyperthermia at electromagnetic radiation frequencies higher than 7 GHz.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Validation Studies using ELK and the Open-Source MOOSE Framework Application Zapdos for Electromagnetic Coupled Plasma Simulation

An open source simulation platform that captures electromagnetics, plasma chemistry, and fluid treatment of the plasma domain would be a powerful tool for studying low temperature plasma (LTP) phenomena. Within the Multiphysics Object-Oriented Simulation Environment (MOOSE) open source framework, ELK, CRANE, and Zapdos are combined to provide open source simulation capability for the LTP community. This talk presents continued validation of the general electromagnetic (EM) simulation tool ELK (Electromagnetic Library for Kinetics & fluids). Previous validation efforts focused on simulating standard waveguide and antenna benchmarks in vacuum and linear dielectrics, but ELK has since been coupled with the MOOSE-based plasma fluid application Zapdos [Lindsay et al 2016 J. Phys. D: Appl. Phys. 49 235204] to perform radio-frequency (rf) capacitively coupled plasma (CCP) system simulation. Plasma validation efforts initially focused on electrostatic benchmarks to demonstrate ELK-Zapdos code coupling and then moved to electromagnetic benchmarks based on interesting geometries and conditions (VHF effects in a CCP reactor, microwave heating, etc.). Results and progress in these efforts will be summarized and discussed.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Continued Validation Studies using the MOOSE Framework for Plasma Simulation with Electromagnetics

Resources and tools for the modeling and simulation of low-temperature plasma (LTP) discharges are increasingly vital to progress in the field in order to properly characterize and study complex source designs and plasma chemistries beyond the scope of traditional diagnostics. Open-source software provides powerful platforms for this work and can enable community-driven LTP R&D. Within the Multiphysics Object-Oriented Simulation Environment (MOOSE) open-source framework [1], capabilities have been demonstrated in the areas of plasma fluids (Zapdos [2]), plasma chemistry (CRANE [3]), and general electromagnetic wave theory (Electromagnetic Library for Kinetics & fluids [ELK] [4]). ELK has since been coupled to Zapdos/CRANE to enable fully coupled electromagnetic plasma simulations. This talk will detail the continued validation efforts and discuss Zapdos-ELK-CRANE code coupling with various-low temperature plasma sources. The impact of fully coupled electromagnetics on process parameters (e.g., temperature and electron/ion energy) versus an electrostatic description will also be discussed. [1] Permann et al., SoftwareX, 11 (2020) 100430. [2] Lindsay et al., J. Phys. D: Appl. Phys. 49 (2016) 235204. [3] Keniley et al., Talk, GEC Session DT3.00002 (2019). [4] Icenhour et al., Talk, GEC Session RR1.00006 (2019). Acknowledgements: INL Graduate Fellowship Program, NSF SI2 Grant 1740300, U.S. Dept. of Energy Office of Science Graduate Student Research Program

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2024

Electromagnetic entrapment in gravity

Abstract We derive specific properties of electromagnetism when gravitational effects are not negligible and analyze their impact on new physics at the horizons of black holes. We show that a neutral configuration of charges in a region of high redshift, characterized by a largeg tt , produces a highly localized electromagnetic field that vanishes just beyond that region. This phenomenon implies the existence of extensive families of spacetime structures generated by electromagnetic degrees of freedom that are as compact as black holes. We construct neutral bound states of extremal black holes in four dimensions and in five dimensions, where one direction is compact. These geometries are indistinguishable from a neutral black hole, referred to asdistorted Schwarzschild, except in an infinitesimal region near its horizon where the entrapped electromagnetic structures start to manifest. The five-dimensional solutions satisfy various criteria for describing black hole microstructure: they increase in size with the Newton constant, are as compact as the Schwarzschild black hole, and have an entropy that scales likeM 2 .

Physics↗
DOE OSTI2017

Electromagnetic shielding effectiveness of 3D printed polymer composites

We report on preliminary results regarding the electromagnetic shielding effectiveness of various 3D printed polymeric composite structures. All studied samples were fabricated using 3D printing technology, following the fused deposition modeling approach, using commercially available filaments as starting materials. The electromagnetic shielding performance of the fabricated 3D samples was investigated in the so called C-band of the electromagnetic spectrum (3.5–7.0 GHz), which is typically used for long-distance radio telecommunications. We provide evidence that 3D printing technology can be effectively utilized to prepare operational shields, making them promising candidates for electromagnetic shielding applications for electronic devices.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Electromagnetic wave absorption of multifunctional cementitious composites incorporating polyvinyl alcohol (PVA) fibers and fly ash: Effects of microstructure and hydration

Highlights: • The cementitious composite shows excellent wide-band electromagnetic wave absorption in a frequency range of 2–18 GHz. • The PVA fibers and the fly ash change the dielectric properties of the cementitious composite by Debye polarization. • The iron oxide of the cementitious binders contributes to the magnetic properties of the composites. • The impacts of the microstructure and the hydration of the cementitious composite on its microwave absorption are analyzed. This paper devises a novel method for the adjustment of the pore structure and the hydration of cement to improve the electromagnetic wave absorption of the cementitious composites incorporating polyvinyl alcohol (PVA) fibers and fly ash in a frequency range of 2–18 GHz. The underlying mechanism of the absorption is investigated to explore the possibility of the structural and functional integration of these composites. The electromagnetic parameters of the prepared cementitious composites and those of the raw materials are analyzed in a frequency range of 0.5–18 GHz. Moreover, the pore structure and the chemical environment of the cementitious composites are examined by mercury intrusion porosimetry (MIP), back-scattered electron detector (BSE), and X-ray photoelectron spectroscopy (XPS). The results indicate that the PVA fibers and the high-volume fly ash have a positive effect on electromagnetic wave absorption of the cementitious composites through the adjustment of their pore structure and hydration.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Synthesis and electromagnetic properties of BaFe{sub 11.92}(LaNd){sub 0.04}O{sub 19}/titanium dioxide composites

Graphical abstract: Due to combining different functions and characteristics of individual materials, hybrid nanocomposite materials can strengthen their applications. Magnetic-conductive nanocomposites are the promising materials with electromagnetic loss, which have synergetic behavior between magnetic and conductive materials. It is the first time to report the synthesis of BaFe{sub 11.92}(LaNd){sub 0.04}O{sub 19}/titanium dioxide (BF/TD) composites by the gel-precursor self-propagating combustion process. The influence of mass ratio of BF and TD on the electromagnetic properties of BaFe{sub 11.92}(LaNd){sub 0.04}O{sub 19}/titanium dioxide composites was studied. The tgδ{sub μ} and tgδ{sub ε} of BF–TD composites. - Highlights: • It is the first time to report BaFe{sub 11.92}(LaNd){sub 0.04}O{sub 19}/titanium dioxide composites. • The composites are prepared by the gel-precursor self-propagating combustion. • The electromagnetic properties could be adjusted by the mass ratio of BF and TD. • The introduction of TD enhances the dielectric loss and widens the frequency bands. • BF/TD composites will be microwave absorption materials with wide frequency band. - Abstract: Doped BaFe{sub 11.92}(LaNd){sub 0.04}O{sub 19}/titanium dioxide composites have been prepared by the gel-precursor self-propagating combustion process. The characterization of the composites are performed by Fourier transform infrared (FT-IR), X-ray diffraction (XRD), Differential thermal analysis-thermo gravimetry (DTA–TG), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM) and network analyzer. Both XRD and FT-IR indicate that the doped BaFe{sub 11.92}(LaNd){sub 0.04}O{sub 19}/titanium dioxide composites are successfully synthesized and there are some interactions between BaFe{sub 11.92}(LaNd){sub 0.04}O{sub 19} and titanium dioxide. DTA–TG analysis of BaFe{sub 11.92}(LaNd){sub 0.04}O{sub 19}/titanium dioxide composites shows that the composite gel decomposition process mainly includes two stages: the first stage is the crystallized water and the residual moisture evaporation; the second stage is the nitrate and citric acid decomposition reaction. SEM demonstrates that the doped BaFe{sub 11.92}(LaNd){sub 0.04}O{sub 19}/titanium dioxide solid solution has formed. The magnetic parameters indicate that the electromagnetic properties of the composites could be well adjusted by the mass ratio of BaFe{sub 11.92}(LaNd){sub 0.04}O{sub 19} and titanium dioxide. When the mass ratio of BaFe{sub 11.92}(LaNd){sub 0.04}O{sub 19} and titanium dioxide is 4:5, the composites have the best magnetic loss. The composites with the mass ratio 6:5 of BaFe{sub 11.92}(LaNd){sub 0.04}O{sub 19} and titanium dioxide. BaFe{sub 11.92}(LaNd){sub 0.04}O{sub 19} and titanium dioxide possess good dielectric loss. The introduction of titanium dioxide enhances the dielectric loss and widens the frequency bands. The composites will be promising microwave absorption materials with wide frequency band.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Effect of Thomas Rotation on the Lorentz Transformation of Electromagnetic fields

A relativistic particle undergoing successive boosts which are non collinear will experience a rotation of its coordinate axes with respect to the boosted frame. This rotation of coordinate axes is caused by a relativistic phenomenon called Thomas Rotation. We assess the importance of Thomas rotation in the calculation of physical quantities like electromagnetic fields in the relativistic regime. We calculate the electromagnetic field tensor for general three dimensional successive boosts in the particle’s rest frame as well as the laboratory frame. We then compare the electromagnetic field tensors obtained by a direct boost β δβ → + → and successive boosts β → and Δβ → and check their consistency with Thomas rotation. This framework might be important to situations such as the calculation of frequency shifts for relativistic spin1/2 particles undergoing Larmor precession in electromagnetic fields with small field non-uniformities.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Electromagnetic physics vectorization in the GeantV transport framework

The development of the GeantV Electromagnetic (EM) physics package has evolved following two necessary paths towards code modernization. A first phase required the revision of the main electromagnetic physics models and their implementation. The main objectives were to improve their accuracy, extend them to the new high-energy frontier posed by the Future Circular Collider (FCC) programme and allow a better adaptation to a multi-particle flow. Most of the EM physics models in GeantV have been reviewed from theoretical perspective and rewritten with vector-friendly implementations, being now available in scalar mode in the alpha release. The second phase consists of a thorough investigation on the possibility to vectorise the most CPU-intensive physics code parts, such as final state sampling. We have shown the feasibility of implementing electromagnetic physics models that take advantage of SIMD/SIMT architectures, thus obtaining gains in performance. After this phase, the time has come for the GeantV project to take a step forward towards the final proof of concept. This takes shape through the testing of the full simulation chain (transport + physics + geometry) running in vectorized mode. In this paper we will present the first benchmark results obtained after vectorizing a full set of electromagnetic physics models.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

Electromagnetic effects on geodesic acoustic modes

By using the full electromagnetic drift kinetic equations for electrons and ions, the general dispersion relation for geodesic acoustic modes (GAMs) is derived incorporating the electromagnetic effects. It is shown that m = 1 harmonic of the GAM mode has a finite electromagnetic component. The electromagnetic corrections appear for finite values of the radial wave numbers and modify the GAM frequency. The effects of plasma pressure β{sub e}, the safety factor q, and the temperature ratio τ on GAM dispersion are analyzed.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗