Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “ELECTROMAGNETIC RADIATION”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Experimental realization of a terahertz all-dielectric metasurface absorber

Metamaterial absorbers consisting of metal, metal-dielectric, or dielectric materials have been realized across much of the electromagnetic spectrum and have demonstrated novel properties and applications. However, most absorbers utilize metals and thus are limited in applicability due to their low melting point, high Ohmic loss and high thermal conductivity. Other approaches rely on large dielectric structures and / or a supporting dielectric substrate as a loss mechanism, thereby realizing large absorption volumes. Here we present a terahertz (THz) all dielectric metasurface absorber based on hybrid dielectric waveguide resonances. We tune the metasurface geometry in order to overlap electric and magnetic dipole resonances at the same frequency, thus achieving an experimental absorption of 97.5%. A simulated dielectric metasurface achieves a total absorption coefficient enhancement factor of F T =140, with a small absorption volume. Our experimental results are well described by theory and simulations and not limited to the THz range, but may be extended to microwave, infrared and optical frequencies. In conclusion, the concept of an all-dielectric metasurface absorber offers a new route for control of the emission and absorption of electromagnetic radiation from surfaces with potential applications in energy harvesting, imaging, and sensing.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Prospects and applications of plasmon-exciton interactions in the near-field regime

Plasmonics is a rapidly developing field at the boundary of fundamental sciences and device engineering, which exploits the ability of metal nanostructures to concentrate electromagnetic radiation. The principal challenge lies in achieving an efficient conversion of the plasmon-concentrated field into some form of useful energy. To date, a substantial progress has been made within the scientific community in identifying the major pathways of the plasmon energy conversion. Strategies based on the hot electron injection and the near-field energy transfer have already shown promise in a number of proof-of-principle plasmonic architectures. Nevertheless, there are several fundamental questions that need to be addressed in the future to facilitate the transition of plasmonics to a variety of applications in both light amplification and optical detection. Of particular interest is a plasmon-induced resonance energy transfer (PIRET) process that couples the plasmon evanescent field to a semiconductor absorber via dipole-dipole interaction. This relatively unexplored mechanism has emerged as a promising light conversion strategy in the areas of photovoltaics and photocatalysis and represents the main focus of the present minireview. Along these lines, we highlight the key advances in this area and review some of the challenges associated with applications of the PIRET mechanism in nanostructured systems.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Fully implicit particle-in-cell algorithms for kinetic simulation of plasmas [Slides]

We have demonstrated, for the first time, a fully implicit, fully nonlinear electrostatic PIC formulation that features: (1) Exact charge conservation (via a novel particle mover strategy). (2) Exact energy conservation (no particle self-heating or self-cooling). (3) Adaptive particle orbit integrator to control errors in momentum conservation. The approach has been shown to be free of CFL and finite-grid numerical instabilities. As a result, the method is able to take time steps many times larger than explicit, and resolutions many times coarser. Central to our implementation is the concept of particle enslavement. We have generalized formulation to use spatial adaptivity via mapped coordinates. he method has much potential for efficiency gains vs. explicit in long-time-scale applications, with the CPU speedup scaling as $(kΛ_D)-^{(d+1)}/N_{FE}$. Minimize the number of nonlinear function evaluations $N_{FE}$ for given $Δt$, $Δx \Rightarrow$ preconditioning! We have formulated and implemented a very efficient moment-based preconditioner. We have ported the algorithm to GPU architectures. We have generalized the algorithm to non-radiative electromagnetic regimes (Darwin model), where, in addition to charge and energy, we also conserve canonical momenta.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2013

High Energy Density Physics and applications with a state-of-the art compact x-pinch

Recent advances in technology has made possible to create matter with extremely high energy density (energy densities and pressure exceeding 10 11 J/m 3 and 1 Mbar respectively). The field is new and complex. The basic question for high energy density physics (HEDP) is how does matter behave under extreme conditions of temperature, pressure, density and electromagnetic radiation? The conditions for studying HEDP are normally produced using high intensity short pulse laser, x-rays, particle beams and pulsed power z-pinches. Most of these installations occupy a large laboratory floor space and require a team consisting of a large number of scientists and engineers. This limits the number of experiments that can be performed to explore and understand the complex physics. A novel way of studying HEDP is with a compact x-pinch in university scale laboratory. The x-pinch is a configuration in which a pulsed current is passed through two or more wires placed between the electrodes making the shape of the letter ‘X’. Extreme conditions of magnetic field (> 200 MGauss for less than 1 ns), temperature (1 keV) and density (~ 10 22 cm -3 ) are produced at the cross-point, where two wires make contact. Further, supersonic jets are produced on either side of the cross-point. The physics of the formation of the plasma at the cross-point is complex. It is not clear what role radiation plays in the formation of high energy density plasma (>> 10 11 J/m 3 ) at the cross-point. Nor it is understood how the supersonic jets are formed. Present numerical codes do not contain complex physics that can take into account some of these aspects. Indeed, a comprehensive experimental study could answer some of the questions, which are relevant to wide-ranging fields such as inertial confinement fusion, astrophysical plasmas, high intensity laser plasma interactions and radiation physics. The main aim of the proposal was to increase the fundamental understanding of high energy density physics and particularly address the key issues associated with x-pinches, which include radiation transport, energetic particle transport, supersonic jet formation, using state-of-the-art compact pulsed power drivers. All the primary objectives of the proposed work were met. These objectives include: • Understanding of the fundamental physics of hot and dense plasma formation, implosion to less than 1 µm size due to the radiation enhanced collapse and energetic electron heating, • Study of the jet formation mechanism, which is of interest due to the astrophysical jets and deposition of energy by energetic electrons in jets, • Characterization of an x-pinch as a point x-ray source for the phase contrast radiography of beryllium cryogenic targets for the National Ignition Facility (NIF) experiments. The work carried out included a strong educational component involving both undergraduate and graduate students. Several undergraduate students from University of California San Diego participated in this project. A post-doctoral fellow, Dr. Simon Bott and two graduate students, David Haas and Erik Shipton contributed to every aspect of this project. The success of the project can be judged from the fact that fifteen peer-reviewed papers were published in high quality journals. In addition several presentations were made to a number of scientific meetings.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2015

Probing Complexity using the Linac Coherent Light Source (LCLS) and the Advanced Light Source (ALS)

The goal of our research program is to investigate fundamental interactions between photons and molecular/nano-systems to advance our quantitative understanding of electron correlations, charge transfer and many body phenomena. Our research projects focus on probing, on a femtosecond time-scale, multi-electron interactions and tracing nuclear motion in order to understand, and ultimately control energy flow and charge transfer processes from electromagnetic radiation to matter. The experiments will be carried out with state of the art instrumentation built by the P.I. team with funds from a DoE "Single Investigator and Small Group Research" (SISGR) grant. The research projects carried out the past three years consisted of first experiments using the Linac Coherent Light Source (LCLS) x-ray free electron laser (FEL) facility at the SLAC National Laboratory, as well as the study of correlated processes in select anions using the Advanced Light Source (ALS). A report for the past cycle is described in section II. These studies have paved the way for our renewal application for the next three years. Our research interests for the next three years extend our past and present research by carrying out time-resolved measurements described in section III. They will consist of: a) The study of molecular dynamics that happen on ultrafast time scales, using pump-probe schemes and the study of non-linear physics in the x-ray regime via multi-photon absorption from the LCLS. This will be achieved by measuring and examining both electronic and nuclear dynamics subsequent to the interaction of molecules and nano-systems with LCLS pulses of various wavelength, intensity and pulse duration as described in section III.A. b) The study of molecular dynamics and correlated processes via absorption of vuv-soft x-rays from the Advanced Light Source (ALS) at Lawrence Berkeley Laboratory to provide single-photon ionization baseline results for LCLS studies. In addition, we will study the photodetachment of anions using the ALS as described in section III. B. The PI has an ALS approved program (AP) thus has guaranteed beamtime. Our research underpins several aspects of the DOE mission since our investigations of the formation and evolution of energized states in molecules and nanostructures provides a fundamental basis for understanding elementary processes in solar energy conversion and radiation-induced chemistry. Most of our work is carried out in a strong partnership with theorists. Our proposed work falls in the class of research reported to be timely and necessary by the 2013 DoE Basic Energy Sciences Advisory Committee (BESAC) Subcommittee report on Future X-ray Light Sources. Specifically, our proposed experiments fall in the category labeled class II, “Spectroscopy and Dynamics with FELs”.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2017

EMR Measurements on NDA Equipment

Electromagnetic radiation (EMR) emission strength measurements were performed on a suite of passive non-destructive assay (NDA) radiation detection equipment. Data were collected from 9 kHz up to 6 GHz on each of the assembled systems.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2018

Photon statistics in attenuators

We derive expressions for the transmission photon statistics of N photons irradiating one or multiple attenuators. The composition of the attenuators themselves may be statistically varying, which is a model for a paramagnetic material in which atoms of di erent spin states absorb di erently. Note that classical electromagnetic radiation emitted by a single-mode laser is best described by Glauber coherent states, so assigning exactly N photons to this state is strictly not correct: Glauber states are superpositions of number states, so the number of incoming photons itself is a stochastic variable. We neglect all that.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Microwave remote sensing for atmospheric chemistry

Microwave remote sensing is a well-established technique for making sensitive thermal emission measurements at microwave frequencies. This thermal emission described by Planck’s law is the electromagnetic radiation at microwave wavelengths intrinsically emitted from hot objects. This is the blackbody radiation that constitutes the microwave baseline signal. The transitions between quantized rotational states of the constituent gas species gives rise to spectral features on top of this background signal. A distribution of the atmospheric constituents is retrieved from the measured emission lineshape correlated to pressure broadening as a function of altitude. Thus microwave radiometers enable the detection and continuous monitoring of trace gases present in the atmosphere. Microwave radiometers are deployed at various sites around the world measuring an assortment of species and meteorological parameters of interest. Several groups worldwide are active in this field, NRL remote sensing division and the Institute of Physics at the University of Bern among the prominent few. The technology is quite mature with the availability of room temperature RF components at W–band frequencies.

58 GEOSCIENCES↗
DOE OSTI2020

Applying Machine Learning to the Classification of DC-DC Converters. NA-22 Final Report

Tools are now available that enable measurement electromagnetic radiation (EMR) from active electronics in an item. This radiation may be intended WIFI or cellular network links, for example or unintended such as the switching noise generated by DC-to-DC converters. It would be extremely valuable to have the capability to discriminate between the low-voltage DC-to-DC converters or other digital noise prevalent in most modern electronics, versus the high-voltage DC-to-DC converters used in utility firesets. Previous work performed under a Sandia Laboratory Directed Research and Development (LDRD) project on Charge State Detection using a deep neural network has been continued in this effort. A state-of-the-art supervised machine learning algorithm has not only been extended to discriminate between low and high voltage converters but has been validated in determining a converters make and model.

42 ENGINEERING↗
DOE OSTI2019

Sandia Response to 2018 PESP Final Report [Memo]

The 2018 Predictive Engineering Science Panel (PESP) is pleased with Sandia's response to our 2018 PESP Final Report recommendations. We have read the response memorandum, applaud the overall Electromagnetic Radiation (EMR) Action Plan and Path Forward and compliment Sandia's progress to date. The panel identifies no pressing issues and proposes no course corrections. The panel does offer two high-level suggestions for the Advanced Simulation and Computing (ASC) Program Office.

42 ENGINEERING↗
DOE OSTI2022

Manipulating and Probing Ultrafast Atomic and Molecular Dynamics (Final Report)

This program has focused on the exploration and control of dynamics in atoms, small molecules, clusters, and micro- or nano-structures following ultrafast excitation and/or driven by strong oscillating fields. In our principal experiments, gas phase atoms and molecules were exposed to short pulses of electromagnetic radiation with frequencies ranging from THz into the XUV spectral regions, and with durations from picoseconds to attoseconds. The pulses coherently induce and/or probe dynamics in the electronic, vibrational, and rotational degrees of freedom of the targets. The overarching goal of the various projects has been to exploit strong-field processes and/or implement novel ultrafast techniques for manipulating and probing coherent electronic and nuclear motion. Typically, the relevant system evolution occurs over attosecond to picosecond timescales. In doing so, we have gained a more complete picture of correlated multi-particle dynamics in atoms, molecules, and other complex systems and expanded the toolbox of useful techniques for manipulating and probing those dynamics. Grant funds were primarily used to: (i) pay salaries and fringe benefits for the PI and postdocs and stipends, tuition, and health care costs for graduate students; (ii) cover travel expenses for the PI, postdocs, and students to attend and participate in professional meetings, conferences, and workshops; and (iii) purchase research materials, supplies, and equipment required for experiments. The research resulted in the publication of 24 peer reviewed articles (including 1 in Nature Physics, 2 in Nature Communications, 7 in Physical Review Letters, and 12 in Physical Review A), and 4 PhD dissertations. The specific results from different funding periods are summarized separately in the main report.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2023

Kilonova Detection

The first observation of gravitational waves (GW) from a binary neutron star collision, known as GW170817, was detected by Laser Interferometer Gravitational-Wave Observatory (LIGO) and Virgo GW observatories. This event marked a profound discovery of the kilonova, which occurs when two neutron stars collide, resulting in an energetically explosive release of gamma-ray bursts (GRBs) and emitting bright electromagnetic radiation. This project focuses on assessing how well kilonovae will be detected in the Legacy Survey of Space and Time (LSST) at the Vera C. Rubin Observatory. By using Kasen models with varying ejecta mass, ejecta velocity, and lanthanide fraction, we analyze these 329 models and create kilonova light curves to assess the number of visible kilonovae for each band, based on the minimum magnitude at various redshifts.

Khalid, Anna↗
DOE OSTI2024

Spread Spectrum Time Domain Reflectivity for String Monitoring in PV Power Plants (Final Technical Report)

This final report describes the methods and results of applying Spread Spectrum Time Domain Reflectivity (SSTDR) for String Monitoring in PV Power Plants for DE-EE0008169. The project created a new system for both detecting and locating electrical faults in photovoltaic systems. In this work, we address photovoltaic electric faults that are both common and costly. Based on interviews with photovoltaic power plant owners, operators, and maintainers, three types of faults are common and of significant interest: disconnects, ground faults, and arc faults. Disconnects can originate from many sources. They are often due to everyday events, such as lawnmowing (accidentally running over a cable), animals eating through the cables, or degradation that occurs over time due to corrosion or general degradation. Ground faults occur when the cables (for example, due to frayed insolation) connect to the ground, relaying current into the ground. These faults are particularly problematic since the ground faults are often intermittent. That is, ground faults commonly appear during rain storms due to a change in soil conductivity and then disappear when the rain ends. This makes the ground fault difficult to find because while current systems can detect the overall change in voltage and current associated with a ground fault, technicians are necessary to locate the fault. As a result, ground faults may disappear before the technician arrives at the power plant. Hence, locating and fixing ground faults often require multiple trips. We also study arc faults, which can result when nearby conductors create an arc of electrical current through the air. While less common, arc faults can be extremely dangerous. The energetic electrical arc can cause fires and destroy equipment, costing significant damage. Overall all three types of faults cost owners and operators money, either from the destruction of equipment or from technician time. Furthermore, while devices exist for detecting ground faults (ground fault circuit interrupters) and arc faults (arc fault circuit interrupter), these systems only search patterns of electrical current that correspond to each fault. This information cannot be used to locate the fault. In addition, these protection systems experience nuisance trips due to nearby electromagnetic interference, such as from a lawn mower or other motors that produce significant amounts of electromagnetic radiation. Hence, the overall goal of this project is to create an SSTDR tool that provides photovoltaic power plants with more reliable fault detection in addition to the localization of faults. SSTDR works by transmitting electrical signals into the photovoltaic string. Those signals reflect from impedance discontinuities (i.e., disconnects, ground faults, and arc faults). These faults are then detected by measuring the presence of a reflection at the SSTDR and can be located by identifying the location of that reflection in time. In addition, unlike current protection systems, these systems do not experience nuisance trips since their low amplitude, high frequency, and coded signal can by analyzed without interference from the regular operational voltage on the photovoltaic string.

14 SOLAR ENERGY↗
DOE OSTI2019

Multi-Messenger Physics With the Pierre Auger Observatory

An overview of the multi-messenger capabilities of the Pierre Auger Observatory is presented. The techniques and performance of searching for Ultra-High Energy neutrinos, photons and neutrons are described. Some of the most relevant results are reviewed, such as stringent upper bounds that were placed to a flux of diffuse cosmogenic neutrinos and photons, bounds placed on neutrinos emitted from compact binary mergers that were detected by LIGO and Virgo during their first and second observing runs, as well as searches for high energy photons and neutrons from the Galactic center that constrain the properties of the putative Galactic PeVatron, observed by the H.E.S.S.\ collaboration. The observation of directional correlations between ultra-high energy cosmic rays and either high energy astrophysical neutrinos or specific source populations, weighted by their electromagnetic radiation, are also discussed. They constitute additional multi-messenger approaches aimed at identifying the sources of high energy cosmic rays.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

Dynamical Control of Broadband Coherent Absorption in ENZ Films

Interferometric effects between two counter-propagating beams incident on an optical system can lead to a coherent modulation of the absorption of the total electromagnetic radiation with 100% efficiency even in deeply subwavelength structures. Coherent perfect absorption (CPA) rises from a resonant solution of the scattering matrix and often requires engineered optical properties. For instance, thin film CPA benefits from complex nanostructures with suitable resonance, albeit at a loss of operational bandwidth. In this work, we theoretically and experimentally demonstrate a broadband CPA based on light-with-light modulation in epsilon-near-zero (ENZ) subwavelength films. We show that unpatterned ENZ films with different thicknesses exhibit broadband CPA with a near-unity maximum value located at the ENZ wavelength. By using Kerr optical nonlinearities, we dynamically tune the visibility and peak wavelength of the total energy modulation. Our results based on homogeneous thick ENZ media open a route towards on-chip devices that require efficient light absorption and dynamical tunability.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Microwave-Assisted Preparation of Luminescent Inorganic Materials: A Fast Route to Light Conversion and Storage Phosphors

Luminescent inorganic materials are used in several technological applications such as light-emitting displays, white LEDs for illumination, bioimaging, and photodynamic therapy. Usually, inorganic phosphors (e.g., complex oxides, silicates) need high temperatures and, in some cases, specific atmospheres to be formed or to obtain a homogeneous composition. Low ionic diffusion and high melting points of the precursors lead to long processing times in these solid-state syntheses with a cost in energy consumption when conventional heating methods are applied. Microwave-assisted synthesis relies on selective, volumetric heating attributed to the electromagnetic radiation interaction with the matter. The microwave heating allows for rapid heating rates and small temperature gradients yielding homogeneous, well-formed materials swiftly. Luminescent inorganic materials can benefit significantly from the microwave-assisted synthesis for high homogeneity, diverse morphology, and rapid screening of different compositions. The rapid screening allows for fast material investigation, whereas the benefits of enhanced homogeneity include improvement in the optical properties such as quantum yields and storage capacity.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2016

TIME-DEPENDENT ELECTRON ACCELERATION IN BLAZAR TRANSIENTS: X-RAY TIME LAGS AND SPECTRAL FORMATION

Electromagnetic radiation from blazar jets often displays strong variability, extending from radio to γ -ray frequencies. In a few cases, this variability has been characterized using Fourier time lags, such as those detected in the X-rays from Mrk 421 using Beppo SAX. The lack of a theoretical framework to interpret the data has motivated us to develop a new model for the formation of the X-ray spectrum and the time lags in blazar jets based on a transport equation including terms describing stochastic Fermi acceleration, synchrotron losses, shock acceleration, adiabatic expansion, and spatial diffusion. We derive the exact solution for the Fourier transform of the electron distribution and use it to compute the Fourier transform of the synchrotron radiation spectrum and the associated X-ray time lags. The same theoretical framework is also used to compute the peak flare X-ray spectrum, assuming that a steady-state electron distribution is achieved during the peak of the flare. The model parameters are constrained by comparing the theoretical predictions with the observational data for Mrk 421. The resulting integrated model yields, for the first time, a complete first-principles physical explanation for both the formation of the observed time lags and the shape of the peak flare X-ray spectrum. It also yields direct estimates of the strength of the shock and the stochastic magnetohydrodynamical wave acceleration components in the Mrk 421 jet.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

THE EFFECT OF TRANSIENT ACCRETION ON THE SPIN-UP OF MILLISECOND PULSARS

A millisecond pulsar is a neutron star that has been substantially spun up by accretion from a binary companion. A previously unrecognized factor governing the spin evolution of such pulsars is the crucial effect of nonsteady or transient accretion. We numerically compute the evolution of accreting neutron stars through a series of outburst and quiescent phases, considering the drastic variation of the accretion rate and the standard disk–magnetosphere interaction. We find that, for the same long-term average accretion rate, X-ray transients can spin up pulsars to rates several times higher than can persistent accretors, even when the spin-down due to electromagnetic radiation during quiescence is included. We also compute an analytical expression for the equilibrium spin frequency in transients, by taking spin equilibrium to mean that no net angular momentum is transferred to the neutron star in each outburst cycle. We find that the equilibrium spin rate for transients, which depends on the peak accretion rate during outbursts, can be much higher than that for persistent sources. This explains our numerical finding. This finding implies that any meaningful study of neutron star spin and magnetic field distributions requires the inclusion of the transient accretion effect, since most accreting neutron star sources are transients. Our finding also implies the existence of a submillisecond pulsar population, which is not observed. This may point to the need for a competing spin-down mechanism for the fastest-rotating accreting pulsars, such as gravitational radiation.

79 ASTRONOMY AND ASTROPHYSICS↗