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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 973 records · Page 54
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Cosmic Background Rejection of the ICARUS experiment at Fermilab

The Short Baseline Neutrino program at Fermilab aims to explore significant regions of parameter space, applicable to sterile neutrinos at the eV mass scale, as suggested by existing experimental anomalies. To this purpose it exploits Liquid Argon Time Projection Chamber detectors located along the Booster Neutrino Beamline to measure both νe appearance and νµ disappearance: the Short Baseline Neutrino Detector and the ICARUS-T600 detector at 110 and 600 m from the neutrino source, respectively. The ICARUS T-600 Far Detector, located at shallow depth, is surrounded by a Cosmic Ray Tagger system to mitigate the cosmic ray background. On average ~ 11 muon tracks are expected to cross the detector during the ~ 1 ms drift time. The cosmic ray tagger is composed of plastic scintillator bars, ensuring near 4π coverage of the detector aiming at tagging cosmic muons and thus reject 𝛾s produced by muon interactions in the surrounding materials that can generate an electromagnetic showers mimicking a νe signal. The system allows one to disentangle cosmic rays from particles originated in a neutrino interaction inside the detector by measuring their position and crossing time. A synchronization of the cosmic ray tagger with the ICARUS photon detection system with a nanosecond accuracy allows one to reject cosmic particles recorded during the beam spill and thus select an enriched sample of neutrino triggered events ahead of the event reconstruction. An overview of the cosmic ray tagger system as well as its role in the neutrino events identification and cosmic background rejection will be presented.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Optimization of relativistic backward wave oscillator with non-uniform slow wave structure and a resonant reflector

This letter optimizes synchronously 18 parameters of a relativistic backward wave oscillator with non-uniform slow wave structure (SWS) and a resonant reflector by using the parallel genetic algorithms and particle-in-cell simulation. The optimization results show that the generation efficiency of microwave from the electron beam has increased 32% compared to that of the original device. After optimization, the electromagnetic mode propagating in the resonant changes from the original TM{sub 020} mode of reflector to higher-order TM{sub 021} mode, which has a high reflection coefficient in a broader frequency range than that of the former. The modulation of current inside the optimized device is much deeper than that in the original one. The product of the electric field and current is defined. Observing this product, it is found that the interaction of the electron beam with the electromagnetic wave in the optimized device is much stronger than that in the original device, and at the rear part of SWS of the optimized device, the electron beam dominantly gives out the energy to the electromagnetic wave, leading to the higher generation efficiency of microwave than that of the original device.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2017

Comparison of ATLOG and Xyce for Bell Labs Electromagnetic Pulse Excitation of Finite-Long Dissipative Conductors over a Ground Plane.

This report details the modeling results for the response of a finite-length dissipative conductor interacting with a conducting ground to the Bell Labs electromagnetic pulse excitation. We use both a frequency-domain and a time-domain method based on transmission line theory through a code we call ATLOG - Analytic Transmission Line Over Ground. Results are compared to the circuit simulator Xyce for selected cases. Intentionally Left Blank

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Analysis of non-equilibrium phenomena in inductively coupled plasma generators

This article addresses the modeling of non-equilibrium phenomena in inductively coupled plasma discharges. In the proposed computational model, the electromagnetic induction equation is solved together with the set of Navier-Stokes equations in order to compute the electromagnetic and flow fields, accounting for their mutual interaction. Semi-classical statistical thermodynamics is used to determine the plasma thermodynamic properties, while transport properties are obtained from kinetic principles, with the method of Chapman and Enskog. Particle ambipolar diffusive fluxes are found by solving the Stefan-Maxwell equations with a simple iterative method. Two physico-mathematical formulations are used to model the chemical reaction processes: (1) A Local Thermodynamics Equilibrium (LTE) formulation and (2) a thermo-chemical non-equilibrium (TCNEQ) formulation. In the TCNEQ model, thermal non-equilibrium between the translational energy mode of the gas and the vibrational energy mode of individual molecules is accounted for. The electronic states of the chemical species are assumed in equilibrium with the vibrational temperature, whereas the rotational energy mode is assumed to be equilibrated with translation. Three different physical models are used to account for the coupling of chemistry and energy transfer processes. Numerical simulations obtained with the LTE and TCNEQ formulations are used to characterize the extent of non-equilibrium of the flow inside the Plasmatron facility at the von Karman Institute. Each model was tested using different kinetic mechanisms to assess the sensitivity of the results to variations in the reaction parameters. A comparison of temperatures and composition profiles at the outlet of the torch demonstrates that the flow is in non-equilibrium for operating conditions characterized by pressures below 30 000 Pa, frequency 0.37 MHz, input power 80 kW, and mass flow 8 g/s.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS2000

Investigation of Fully Three-Dimensional Helical RF Field Effects on TWT Beam/Circuit Interaction

A fully three-dimensional (3D), time-dependent, helical traveling wave-tube (TWT) interaction model has been developed using the electromagnetic particle-in-cell (PIC) code MAFIA. The model includes a short section of helical slow-wave circuit with excitation fed by RF input/output couplers, and electron beam contained by periodic permanent magnet (PPM) focusing. All components of the model are simulated in three dimensions allowing the effects of the fully 3D helical fields on RF circuit/beam interaction to be investigated for the first time. The development of the interaction model is presented, and predicted TWT performance using 2.5D and 3D models is compared to investigate the effect of conventional approximations used in TWT analyses.

Kory, Carol L.↗
NASA NTRS2017

Electromagnetic Scattering and Emission by a Fixed Multi-Particle Object in Local Thermal Equilibrium: General Formalism

The majority of previous studies of the interaction of individual particles and multi-particle groups with electromagnetic field have focused on either elastic scattering in the presence of an external field or self-emission of electromagnetic radiation. In this paper we apply semi-classical fluctuational electrodynamics to address the ubiquitous scenario wherein a fixed particle or a fixed multi-particle group is exposed to an external quasi-polychromatic electromagnetic field as well as thermally emits its own electromagnetic radiation. We summarize the main relevant axioms of fluctuational electrodynamics, formulate in maximally rigorous mathematical terms the general scattering emission problem for a fixed object, and derive such fundamental corollaries as the scattering emission volume integral equation, the Lippmann Schwinger equation for the dyadic transition operator, the multi-particle scattering emission equations, and the far-field limit. We show that in the framework of fluctuational electrodynamics, the computation of the self-emitted component of the total field is completely separated from that of the elastically scattered field. The same is true of the computation of the emitted and elastically scattered components of quadratic linear forms in the total electromagnetic field. These results pave the way to the practical computation of relevant optical observables.

Electromagnetic scattering; Thermal emission; Fluc↗
NASA NTRSDate not supplied

Deflection of Solar Energetic Protons by an Ion Thruster

While Galactic Cosmic Rays (GCR) represent a long-term cancer risk to deep space human missions, Solar Energetic Particles (SEP) represent a significant acute radiation hazard to human spaceflight. This work investigates wave-particle interactions caused by the incidence of a beam of energetic protons, representing a notional SEP event, onto a cloud of ions representing a notional ion thruster plume. The resulting electromagnetic ion/ion instability is developed to investigate the degree to which energetic protons can be scattered out of the initial beam. This work includes investigations of deflection rate dependences on incident SEP energy and flux, ion thruster power and orientation relative to SEP incidence, plume ion species, and background plasma. Also investigated are the spectrum and angular distribution of electromagnetic radiation resulting from the wave-particle interactions. The primary objective of this investigation is to develop a technique for active mitigation of SEP radiation threats to spacecraft and crew, by exploring the wave-particle interaction of a SEP event with the plasma plume expelled from an ion thruster. Since the cost in expended fuel restricts this technique to intermittent use during interplanetary flights, effective prediction of when a SEP event might impact the mission is still important, and the observation of conditions that might lead to SEP events, human-in-the-loop space weather analyses, and development of SEP prediction models remain essential to crew safety, spacecraft function, and mission success.

Interplanetary Space Flight↗
DOE OSTI2015

A conceptual design of an electron spectrometer for ELI-NP

We present the geometry and field parameters of an Electron Spectrometer (ES) with two dipole magnets, considered for electron energy measurements at the High Fields QED experimental area at ELI-NP. The first magnet is a 2 meter long permanent magnet, placed inside the Interaction Chamber (IC). The second magnet is a 1.5 meters long electromagnet, placed outside IC. The pulsed electron beam will be produced by the 10 PW pulsed Laser, ‘pump-beam’, focused into one meter long capillary low density plasma cell. A second 10 PW pulsed Laser, ‘probe-beam’, will interact with the relativistic electron bunch providing the strong electromagnetic field. The ES will measure the subtle changes in the electron energy spectrum as a result of the electron beam interaction with the probe-beam field.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2019

Nonlinear Interaction of Microwave Radiation with a Plasma Flow under Hybrid Resonance Conditions

We propose a simple model of quasi-one-dimensional steady-state nonequilibrium plasma flow propagating along the axis of an open magnetic trap and sustained by an rf electromagnetic field. The model makes it possible to analyze qualitatively possible regimes of the plasma flow in the presence of induced intrinsic rf field amplified due to geometrical resonance with the plasma flow and to determine the main features and key characteristics of nonlinear absorption of the external field energy.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2012

Calibration of the neutron detectors for the cluster fusion experiment on the Texas Petawatt Laser

Three types of neutron detectors (plastic scintillation detectors, indium activation detectors, and CR-39 track detectors) were calibrated for the measurement of 2.45 MeV DD fusion neutron yields from the deuterium cluster fusion experiment on the Texas Petawatt Laser. A Cf-252 neutron source and 2.45 MeV fusion neutrons generated from laser-cluster interaction were used as neutron sources. The scintillation detectors were calibrated such that they can detect up to 10{sup 8} DD fusion neutrons per shot in current mode under high electromagnetic pulse environments. Indium activation detectors successfully measured neutron yields as low as 10{sup 4} per shot and up to 10{sup 11} neutrons. The use of a Cf-252 neutron source allowed cross calibration of CR-39 and indium activation detectors at high neutron yields ({approx}10{sup 11}). The CR-39 detectors provided consistent measurements of the total neutron yield of Cf-252 when a modified detection efficiency of 4.6 Multiplication-Sign 10{sup -4} was used. The combined use of all three detectors allowed for a detection range of 10{sup 4} to 10{sup 11} neutrons per shot.

43 PARTICLE ACCELERATORS↗
NASA NTRS2012

The Impact of Electromagnetic Cascades of Very-high Energy Gamma Rays on the Extragalactic Gamma-ray Background

As very high energy (VHE) photons propagate through the extragalactic background light (EBL), they interact with the soft photons of the EBL and initiate electromagnetic cascades of photons and electrons. The collective intensity of a cosmological population emitting at VHEs (such as blazars) will be attenuated at the highest energies through interactions with the EBL and enhanced at lower energies by the resulting cascade. As such, depending on the space density and spectra of the sources and the model of the EBL, cascade radiation can provide a significant contribution to the extragalactic gamma-ray background (EGB). Through deflections of the charged particles of the cascade, an intergalactic magnetic field (IGMF) may leave an imprint on the anisotropy properties of the EGB. The impact of a strong IGMF is to isotropize lower energy cascade photons, inducing a modulation in the anisotropy energy spectrum of the EGB. We discuss the implications of cascade radiation for the origins of the EGB and the nature of the IGMF, as well as insight that will be provided by data from the Fermi Large Area Telescope in the upcoming years.

Venters, Tonia↗
DOE OSTI2016

Is {sup 276}U a doubly magic nucleus?

We investigate a possible new doubly magic heavy nucleus by using a relativistic mean-field (RMF) model with the addition of a cross interaction term of omega-rho mesons and an electromagnetic exchange term. We propose that {sup 276}U is a doubly magic nucleus. The evidence for {sup 276}U being a doubly magic nucleus is shown through the two-nucleon gaps, the single-particle energies, and the neutron skin thickness of the nucleus. We have also found that the prediction of {sup 276}U as a doubly magic nucleus by the RMF model is not affected by the inclusion of isoscalar-isovector and electromagnetic exchange couplings.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2019

Quantum Rolling Friction

An atom moving in a vacuum at constant velocity and parallel to a surface experiences a frictional force induced by the dissipative interaction with the quantum fluctuations of the electromagnetic field. We show that the combination of nonequilibrium dynamics, the anomalous Doppler effect, and spin-momentum locking of light mediates an intriguing interplay between the atom’s translational and rotational motion. In turn, this deeply affects the drag force in a way that is reminiscent of classical rolling friction. Our fully non-Markovian and nonequilibrium description reveals counterintuitive features characterizing the atom’s velocity-dependent rotational dynamics. Finally, these results prompt interesting directions for tuning the interaction and for investigating nonequilibrium dynamics as well as the properties of confined light.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2013

Deflection of a monochromatic THz beam by acousto-optic methods

The possibility of controlled deflection of an electromagnetic THz beam of a free-electron laser by acousto-optic (AO) methods has been demonstrated for the first time. The material of the AO deflector was chosen to be single-crystal germanium, which has a fairly large refractive index (n = 4.0) and a relatively low absorption coefficient for electromagnetic waves. The absorption coefficient α in germanium is 0.75 ± 0.02 cm{sup -1} at a wavelength λ = 140 μm. The diffracted beam intensity is shown to be maximum at an effective AO interaction length l = 1/α. A diffraction efficiency of 0.05% at a travelling acoustic wave power of 1.0 W is experimentally obtained. It is established that a change in the ultrasonic frequency from 25 to 39 MHz leads to variation in the external Bragg angle in the range from 19.5° to 27.5°. At a fixed Bragg angle θ{sub B} = 22.4° the frequency band of diffraction is 4.2 ± 0.1 MHz and the angular range of laser beam scanning reaches 2.5° ± 0.5°. The results obtained indicate that AO interaction can be used for controlled deflection of electromagnetic THz beams. (terahertz radiation)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2026

Intrinsic nonlocality of spin- and polarization-resolved probabilities in strong-field quantum electrodynamics

Spin and polarization are central to precision tests of fundamental physics and for interpreting radiation from astrophysical sources and ultraintense laser-matter experiments. Here, focusing on the fundamental process of nonlinear Compton scattering, we demonstrate that a key assumption underlying current strong-field quantum electrodynamics models, i.e., that emission can be treated as an instantaneous random event sampled from a local differential rate, is inconsistent once emission angles, electron spin, and/or photon polarization are resolved. Namely, even in strictly constant and uniform fields , the resulting fully differential distribution is sign indefinite, yielding negative inferred probabilities. The physical reason is that the photon emission probability builds up over a finite length of the electron trajectory, the formation region, during which the electron direction changes by roughly the same small angle that defines the radiation cone. Therefore, we put forward a new method where we integrate over this formation region analytically to obtain a physically consistent electron spin and photon polarization model. We show that the implementation of our model is compatible with existing Monte Carlo and particle-in-cell workflows. Simulations of a GeV-class electron-laser collision accessible at current petawatt facilities and of emission in a pulsarlike magnetic field are shown to reveal spin and polarization patterns that differ even qualitatively from state-of-the-art local models. In particular, our new model predicts substantial angle-dependent circular photon polarization where the well-known collinear-emission approach yields none, and a pronounced helicity bias in the recoiling electrons absent from current predictions. These findings have direct implications for upcoming strong-field QED experiments and for interpreting polarized radiation from extreme astrophysical environments.

astrophysical electromagnetic fields↗
NASA NTRS1998

Investigation of EM Emissions by the Electrodynamic Tether, Inclusive of an Observational Program (EMET)

Our TSS-1/R investigation, which we shall refer to as EMET in this report, was an integral part of the effort by the TSS-1/R Investigators' Working Group (IWG) to come to an understanding of the complex interaction between the tethered satellite system and the ionosphere. All of the space-borne experiments were designed to collect data relevant to the local interaction. Only the ground- based experiments, EMET and its Italian counterpart Observations on the Earth's Surface of Electromagnetic Emissions (OESEE), held out any hope of characterizing the long range effects of the interaction. This was to be done by detecting electromagnetic waves generated by the system in the ionosphere, assuming the signal reached the Earth's surface with sufficient amplitude. As the type of plasma waves excited to carry charge away from the charge-exchange regions of the system at each end of the tether is one of the theoretical points about which there is greatest disagreement, a definitive identification of tether-generated waves could mark significant progress in the so-called current closure problem of electrodynamic tethers. Dr. Mario Grossi of the Smithsonian Astrophysical Observatory (SAO) initiated the investigation, and his experience in the field of ULF-ELF waves and their detection was invaluable throughout its course. Rice University had the responsibility of setting up the EMET ULF-VLF ground stations under a subcontract from SAO. Principal Investigator (PI) for the Rice effort was Prof. William E. Gordon, who was primary observer at the Arecibo Observatory during TSS-LR. Dr. Steve Noble handled major day-to-day operations, training, and planning for the ground-based measurements. Dr. James McCoy of NASA JSC, a member of the Mona/Arecibo team, was pilot for the numerous flights ferrying personnel and equipment between Puerto Rico and Mona Island. Final responsibility for the measurements rested with SAO, and the activities of field personnel and SAO investigators were closely co-ordinated during the mission. Dr. Enrico Lorenzini of SAO served as the eyes, ears, and brain of EMET in the Science Operations Area and PI table during the mission, whenever the PI was absent during the round-the-clock mission operations. The Rice University final report to SAO, which is included as an Appendix, contains details of the remote sites, means of communication, sensors, etc., as well as the affiliations of personnel involved in the data-gathering effort.

Estes, Robert D.↗
DOE OSTI2017

Depletion of Intense Fields

The interaction of charged particles and photons with intense electromagnetic fields gives rise to multiphoton Compton and Breit-Wheeler processes. These are usually described in the framework of the external field approximation, where the electromagnetic field is assumed to have infinite energy. However, the multiphoton nature of these processes implies the absorption of a significant number of photons, which scales as the external field amplitude cubed. As a result, the interaction of a highly charged electron bunch with an intense laser pulse can lead to significant depletion of the laser pulse energy, thus rendering the external field approximation invalid. We provide relevant estimates for this depletion and find it to become important in the interaction between fields of amplitude a 0 ~ 103 and electron bunches with charges of the order of 10 nC.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Theoretical Modeling of Electromagnetic Field from Electron Bunches in Periodic Wire Medium

The interaction of relativistic electrons with periodic conducting structures results in radiation via a number of mechanisms. In case of crystals one obtains parametric X-ray radiation, its frequency is determined by the distance between crystallographic planes and the direction of electron beam. If instead of a crystal one considers a periodic structure of metallic wires with the spacing of the order of mm, it is plausible to expect the emission of radiation of a similar nature (“diffraction response”) at THz frequencies. Additionally, a “long-wave” radiation will occur in this case with wavelengths much larger then structure periods. In this contribution, we present different theoretical approaches for describing the electromagnetic radiation field from prolonged electron bunch propagated in the lattice of metallic wires. The validity of these analytical descriptions is checked by numerical simulations. We discuss the possible applications of aforementioned structure as sources of coherent THz radiation.

43 PARTICLE ACCELERATORS↗