Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “electron beams”

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 973 records · Page 54
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

JSPEC – An Open Source Program for IBS and Electron Cooling Simulation

The intrabeam scattering can affect the accumulation, the lifetime, and the property of a high-intensity beam. Electron cooling is a method to mitigate the intrabeam scattering effect. JSPEC (JLab Simulation Package on Electron Cooling) is an open-source program developed at Jefferson Lab, which includes various numerical models and friction force formulas for intrabeam scattering and electron cooling simulations. JSPEC has been benchmarked with BETACOOL and experimental data. In this report, we will introduce what features JSPEC provides to the users and how it carries out the computations. Numerical examples are presented to demonstrate the performance and the validity of JSPEC.

Zhang, He↗
DOE OSTI2023

Ramp Generator for Electron Scanner in SNS Beam Profile Measurements System

A new fast high voltage Ramp Generator to deflect an electron beam in the Electron Scanner is required at the Spallation Neutron Source (SNS) in the Oak Ridge National Laboratory. The Electron Scanner is used for non-destructively measuring the transverse profiles of the proton beam in the accumulator ring of the SNS [1]. The existing deflector is obsolete and needs to be replaced. A new Ramp Generator is proposed based on fast high voltage MOSFET power switches. Two configurations have been considered. One is bipolar, with two opposite polarity power supplies and one switch module or two single switches, and the other is unipolar, with one power supply and two switch modules. Schematics and performance of both options are described, and results of the prototype testing are presented in the paper.

Peplov, Vladimir↗
DOE OSTI2024

High Energy Cooling

The paper considers methods of particle cooling applicable to beam cooling in high energy hadron colliders at the collision energy. Presently, there are two major methods of the cooling the electron cooling and stochastic cooling. The later, in application to colliders, requires exceptionally large frequency band of cooling system. Presently two methods are considered. They are the optical stochastic cooling (OSC) and the coherent electron cooling (CEC). OSC and CEC are essentially extensions of microwave stochastic cooling, operating in 1-10 GHz frequency range, to the optical frequencies enabling bands up to 30-300 THz. The OSC uses undulators as a pickup and a kicker, and an optical amplifier for signal amplification, while the CEC uses an electron beam for all these functions. We discuss major limitations, advantages and disadvantages of electron and stochastic cooling systems.

43 PARTICLE ACCELERATORS↗
DOE OSTI2023

Flexible and Extensive Platinum Ion Gel Condensers for Programmable Catalysis

Catalytic condensers composed of ion gels separating a metal electrode from a platinum-on-carbon active layer were fabricated and characterized to achieve more powerful, high surface area dynamic heterogeneous catalyst surfaces. Ion gels comprised of poly(vinylidene difluoride)/1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide were spin coated as a 3.8 μm film on a Au surface, after which carbon sputtering of a 1.8 nm carbon film and electron-beam evaporation of 2 nm Pt clusters created an active surface exposed to reactant gases. Electronic characterization indicated that most charge condensed within the Pt nanoclusters upon application of a potential bias, with the condenser device achieving a capacitance of ∼20 μF/cm 2 at applied frequencies of up to 120 Hz. The maximum charge of ∼10 14 |e – | cm –2 was condensed under stable device conditions at 200 °C on catalytic films with ∼10 15 sites cm –2 . Grazing incidence infrared spectroscopy measured carbon monoxide adsorption isobars, indicating a change in the CO* binding energy of ∼19 kJ mol –1 over an applied potential bias of only 1.25 V. Condensers were also fabricated on flexible, large area Kapton substrates allowing stacked or tubular form factors that facilitate high volumetric active site densities, ultimately enabling a fast and powerful catalytic condenser that can be fabricated for programmable catalysis applications.

Catalysis↗
DOE OSTI2025

High polarization InAlGaAs/AlGaAs photocathodes grown using MBE

Strained superlattices of GaAs/GaAsP grown using molecular beam epitaxy (MBE) have been used for more than 20 years to generate high polarization electron beams for nuclear physics. GaAs/GaAsP superlattices have several manufacturing challenges, including the thick graded layer required for the virtual GaAsP substrate, the significant difference in optimal growth temperatures for GaAs and GaAsP, and the scarcity of MBE systems using phosphorus. InAlGaAs/AlGaAs strained superlattice photocathode are an alternative structure that eliminates many of hurdles to growing GaAs/GaAsP in MBE systems. Measurements of quantum efficiency and polarization from InAlGaAs/AlGaAs will be presented. These include studies on a variety of growth parameters to optimize performance, including digital alloys, growth temperature variations, and variation in structure.

Stutzman, Marcy L↗
DOE OSTI2023

Disruption Mitigation Solutions for Long Pulse Tokamaks (Final Technical Report)

The project "Disruption Mitigation Solutions for Long Pulse Tokamaks" was a collaborative effort between ORNL, GA, and UCSD. The main goal of the project was to study the injection of shattered cryogenic pellets (SPI) as a method of reducing wall damage from global tokamak plasma instabilities called disruptions. This work was primarily carried out in the JET tokamak in the UK. The team already had extensive experience studying PSI in the medium sized DIII-D tokamak in the US, but adding data from the larger JET tokamak enabled more confident extrapolation to the even larger planned ITER tokamak in France. Each of the collaborating institutions focused on different aspects of SPI disruption mitigation. The UCSD collaboration focused on the volume recombination of post-disruption runaway electron (RE) beams by massive hydrogen injection. Disruptions can sometimes result in the formation of toroidal (ring shaped) beams of highly energetic (relativistic) electron beams, which can cause serious local wall damage, even in present-day tokamaks. A promising method to reduce wall damage from the RE beams is to inject massive amounts of H 2 or D 2 into the beams using SPI. although the precise method by which the injected H 2 reducses RE wall damage is still being investigated, it seems clear that a necessary and required step for the reduction to occur is for the H 2 injection to cause volume recombination (free electron density reduction) of the background cold plasma surrounding the fast electron beam. The UCSD collaboration focused on answering the question of if this recombination could be achievable in the future reactor-size tokamak ITER using realistic levels of H 2 injection. A model capturing the most essential physics was developed and was constrained using both DIII-D and JET data. This model was then used to extrapolate to ITER. It was predicted that RE beam recombination should be achievable in ITER, although in the worst-case scenari (a 10 MA Re beam in ITER), recombination is barely achieved within the maximum allowed levels of H 2 injection.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2025

A structural analysis of ordered Cs3Sb films grown on single crystal graphene and silicon carbide substrates

Alkali antimonides are well established as high efficiency, low intrinsic emittance photocathodes for accelerators and photon detectors. However, conventionally grown alkali antimonide films are polycrystalline with surface disorder and roughness that can limit achievable beam brightness. Ordering the crystalline structure of alkali antimonides has the potential to deliver higher brightness electron beams by reducing surface disorder and enabling the engineering of material properties at the level of atomic layers. In this report, we demonstrate the growth of ordered Cs3Sb films on single crystal substrates 3C-SiC and graphene-coated 4H-SiC using pulsed laser deposition and conventional thermal evaporation growth techniques. The crystalline structures of the Cs3Sb films were examined using reflection high energy electron diffraction and x-ray diffraction diagnostics, while film thickness and roughness estimates were made using x-ray reflectivity. With these tools, we observed ordered domains in less than 10 nm thick films with quantum efficiencies greater than 1% at 530 nm. Moreover, we identify structural features such as Laue oscillations indicative of highly ordered films. We found that Cs3Sb films grew with flat, fiber-textured surfaces on 3C-SiC and with multiple ordered domains and sub-nanometer surface roughness on graphene-coated 4H-SiC under our growth conditions. We identify the crystallographic orientations of Cs3Sb grown on graphene-coated 4H-SiC substrates and discuss the significance of examining the crystal structure of these films for growing epitaxial heterostructures in future experiments.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Phase Measurements of a 140-GHz Confocal Gyro-Amplifier

The phase stability of a 140-GHz, 1-kW pulsed gyro-amplifier system and the phase dependence on the cathode voltage were experimentally measured. To optimize the measurement precision, the amplifier was operated at 47 kV and 1 A, where the output power was ~ 30 W. The phase was determined to be stable both pulse-to-pulse and during each pulse, so far as the cathode voltage and electron beam current are constant. The phase variation with voltage was measured and found to be 130 ± 30° /kV, in excellent agreement with simulations. The electron gun used in this device is non-adiabatic, resulting in a steep slope of the beam pitch factor with respect to cathode voltage. This was discovered to be the dominant factor in the phase dependence on voltage. The use of an adiabatic electron gun is predicted to yield a significantly smaller phase sensitivity to voltage, and thus a more phase-stable performance. To our knowledge, these are the first phase measurements reported for a gyro-amplifier operating at a frequency above W-band.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

Phase Measurements of a 140-GHz Confocal Gyro-Amplifier

The phase stability of a 140-GHz, 1-kW pulsed gyro-amplifier system and the phase dependence on the cathode voltage were experimentally measured. To optimize the measurement precision, the amplifier was operated at 47 kV and 1 A, where the output power was ~30 W. The phase was determined to be stable both pulse-to-pulse and during each pulse, so far as the cathode voltage and electron beam current are constant. The phase variation with voltage was measured and found to be 130 ± 30 deg/kV, in excellent agreement with simulations. The electron gun used in this device is non-adiabatic, resulting in a steep slope of the beam pitch factor with respect to cathode voltage. This was discovered to be the dominant factor in the phase dependence on voltage. The use of an adiabatic electron gun is predicted to yield a significantly smaller phase sensitivity to voltage, and thus a more phase-stable performance. To our knowledge, these are the first phase measurements reported for a gyro-amplifier operating at a frequency above W-band.

Rosenzweig, Guy↗
DOE OSTI2022

Atomic-scale e-beam sculptor

A system and method (referred to as the system) fabricates controllable atomic assemblies in two and three dimensions. The systems identify by a non-invasive imager, a local atomic structure, distribution of vacancies, and dopant atoms and modify, by a microscopic modifier, the local atomic structure, via electron beam irradiation. The systems store, by a knowledge base, cause-and-effect relationships based on a non-invasive imaging and electron scans. The systems detect, by detectors, changes in the local atomic structure induced by the electron irradiation; and fabricate, a modified atomic structure by a beam control software and feedback.

Kalinin, Sergei V.↗
DOE OSTI2021

Detector Solenoid Compensation for the Electron-Ion Collider

The central detector in the present EIC design includes a 4 m long solenoid with an integrated strength of up to 12 Tm. The electron beam passes on-axis through the solenoid, but the hadron beam has an angle of 25 mrad. Thus the solenoid couples horizontal and vertical betatron motion in both electron and hadron storage rings, and causes a vertical closed orbit excursion in the hadron ring. The solenoid also couples the transverse and longitudinal motions of both beams, when crab cavities are also considered. In this paper, we present schemes for closed orbit correction and coupling compensation at the IP, including crabbing.

43 PARTICLE ACCELERATORS↗
DOE OSTI2025

Ultimate brightness of a medium-energy synchrotron light source at operational beam intensity

Synchrotron light sources are key instruments of modern science, providing unique opportunities for groundbreaking studies in diverse scientific disciplines and driving innovation in numerous scientific and technological fields. Fourth-generation light sources provide unprecedented capabilities in imaging, spectroscopy and diffraction techniques. Ultimate brightness is the key to advancing to a smaller scale, faster response, and higher data measurement and processing rate. The brightness is primarily determined by the electron beam emittance and energy spread at operational intensity. A common feature of fourth-generation synchrotrons is the short length of the electron bunches combined with a very small transverse beam size. Consequently, the high particle density leads to strong collective effects that significantly increase the emittance and limit the achievable brightness at operational beam intensity. In this article, we summarize our studies of the emittance and brightness scaled with the beam energy and intensity, taking into account the effects of intrabeam scattering, beam-impedance interaction and bunch lengthening provided by higher-harmonic RF systems to identify optimal combinations of machine and beam parameters.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Mapping valence electron distributions with multipole density formalism using 4D-STEM

Recent advancement in aberration correction and detector technology opened a door to various applications using 4D-STEM, which yields a diffraction pattern for each scanning position within a crystal unit-cell in scanning transmission electron microscopy (STEM) and generates incredible amounts of data in momentum space. Currently 4D-STEM analysis relies on the center-of-mass of the diffraction patterns in electric field and charge density mapping. It only derives the total projected charge density and is limited to phase objects, e.g. extremely thin samples. Here, we propose a new analytical method to accurately map aspherical valence electron distributions with atom-centered multipolar functions formalism using the whole 4D-STEM dataset. We demonstrate that, with the full dynamical calculations for various sample thicknesses, the method is sensitive not only to the miniscule charge transfer, but also to the atomic site symmetry and aspherical electron orbitals. The process of the refinement is much more robust and reliable than quantitative convergent beam electron diffraction.

4D-STEM↗
DOE OSTI2026

Atomic-Scale Imaging of Lithium Vacancies in a Battery Cathode by Multislice Electron Ptychography

Atomic-resolution imaging of battery materials is critical for identification of local defects and structural variations, which are tied to battery performance. However, since battery materials are, by design, optimized to allow ion motion in response to an applied electric field, they are also very sensitive to radiation damage by an electron beam. Image resolution is therefore severely constrained by the dose applied. Here, we show that multislice electron ptychography (MEP) can provide sub-ångström lateral resolution images of both light and heavy elements of a Li-ion battery cathode, along with nanometer-scale depth information and greater dose efficiency than conventional electron microscopy methods. Using the depth-sectioning capability of MEP, we have been able to obtain direct visualizations of Li vacancy clusters, atom column by atom column, in Li x Ni 0.33 Mn 0.33 Co 0.33 O 2 (NMC111) cathodes. This capability to track Li distributions will be valuable in understanding, informing, and optimizing electrode material design for ion storage and transfer.

batteries↗
DOE OSTI2020

Electron Mixing and Isotropization in the Exhaust of Asymmetric Magnetic Reconnection With a Guide Field

In this work, we investigate an exhaust crossing of asymmetric guide field reconnection observed by Magnetospheric Multiscale (MMS) mission at Earth's dayside magnetopause. One MMS spacecraft (MMS 4) observes multicomponent electron distributions, including two counterstreaming electron beams, while the other three MMS spacecraft, with a separation of ~30 km, record nearly isotropic electron distributions. As counterstreaming electrons are unstable for the electron two-stream instability, our observations suggest that the electrostatic waves generated by the fast-growing electron two-stream instability can contribute to the rapid isotropization of electron distributions in the reconnection exhaust, indicating that wave-particle interactions play an important role in electron dynamics.

58 GEOSCIENCES↗
DOE OSTI2025

Imaging nanoscale carrier, thermal, and structural dynamics with time-resolved and ultrafast electron energy-loss spectroscopy

Time-resolved and ultrafast electron energy-loss spectroscopy (EELS) is an emerging technique for measuring photoexcited carriers, lattice dynamics, and near-fields across femtosecond to microsecond timescales. When performed in either a specialized scanning transmission electron microscope or ultrafast electron microscope (UEM), time-resolved and ultrafast EELS can directly image charge carriers, lattice vibrations, and heat dissipation following photoexcitation or applied bias. Yet, recent advances in theoretical calculations and electron optics are often required to realize the full potential of ultrafast EEL spectrum imaging. Here, in this review, we present a comprehensive overview of the recent progress in the theory and instrumentation of time-resolved and ultrafast EELS. We begin with an introduction to the technique, followed by a physical description of the loss function. We outline approaches for calculating and interpreting ground-state and transient EEL spectra spanning low-loss plasmons to core-level excitations analogous to x-ray absorption. We then survey the current state of time-resolved and ultrafast EELS techniques beyond photon-induced near-field electron microscopy, highlighting abilities to image carrier and thermal dynamics. Finally, we examine future directions enabled by emerging technologies, including electron beam monochromation, in situ and operando cells, laser-free UEM, and high-speed direct electron detectors. These advances position time-resolved and ultrafast EELS as a critical tool for uncovering nanoscale dynamic processes in quantum materials and solar energy conversion devices.

Computational methods↗
DOE OSTI2021

Pinhole Formation in Poly-Si/SiOx Passivating Contacts on Si(111)-Oriented Textures

Poly-Si/SiOx passivating contacts were grown on inverted pyramid and random pyramid textured wafers to investigate the hypothesis that pinhole formation is most susceptible at the valleys and edges of a textured surface. Tetramethylammonium hydroxide (TMAH) etching and electron beam induced current (EBIC) were used to assess pinhole formation and charge-carrier transport. Scanning electron microscopy revealed that TMAH etching can expose pinhole locations on textured surfaces. We show that pinholes may preferentially form at the vertices of inverted pyramids. Our TMAH and EBIC analyses on random pyramids show no preferential oxide breakup at the pyramid valleys.

41 EE - Solar Energy Technologies Office (EE-4S)↗
DOE OSTI2025

Potential for tensor polarized deuterons in Hall D at Jefferson lab

Hall D at Jefferson lab is an ideal place to install a polarized deuteron target which can be “tensor polarized”, allowing the separation of the spin states m = 0, ±1 or the measurement of tensor asymmetries. The bremsstrahlung photon beam with 3 - 12 GeV endpoint provides very little heating or radiation damage compared to an electron beam, allowing the target to be run in frozen spin mode. Adiabatic fast passage spin manipulations can then be used to greatly enhance the population of the m = 0 spin state of the deuteron. Coherent photoproduction of ρ mesons from deuterium is sensitive to double-scattering at high momentum transfer and in the m = 0 spin state an additional sensitivity at intermediate momentum transfer opens up. In conclusion, we propose a frozen spin target for Hall D and the measurement of ρ photoproduced coherently from the deuteron as a flagship measurement.

43 PARTICLE ACCELERATORS↗