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Results for “charge patterning”

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 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Universality of scanning tunneling microscopy in cuprate superconductors

We consider the problem of local tunneling into cuprate superconductors, combining model-based calculations for the superconducting order parameter with wave function information obtained from first-principles electronic structure. For some time it has been proposed that scanning tunneling microscopy (STM) spectra do not reflect the properties of the superconducting layer in the CuO 2 plane directly beneath the STM tip, but rather a weighted sum of spatially proximate states determined by the details of the tunneling process. These ``filter'' ideas have been countered with the argument that similar conductance patterns have been seen around impurities and charge ordered states in systems with atomically quite different barrier layers. Here we use a recently developed Wannier function-based method to calculate topographies, spectra, conductance maps, and normalized conductance maps close to impurities. We find that it is the local planar Cu d x 2 –y 2 Wannier function, qualitatively similar for many systems, that controls the form of the tunneling spectrum and the spatial patterns near perturbations. Furthermore we explain how, despite the fact that STM observables depend on the materials-specific details of the tunneling process and setup parameters, there is an overall universality in the qualitative features of conductance spectra. In particular, we discuss why STM results on Bi 2 Sr 2 CaCu 2 O 8 (BSCCO) and Ca 2–x Na x CuO 2 Cl 2 (NaCCOC) are essentially identical.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Integration of Electric Vehicle Charging Loads in Residential Building Stock Energy Modeling

The rapid adoption of electric vehicles (EVs) has resulted in significant new household electric loads that have the potential to change how energy costs are incurred by homeowners and the landscape of utility operations and energy infrastructure. Whereas adoption patterns and magnitudes of residential building and EV charging loads are influenced by distinct factors, the loads themselves are tightly coupled with the behavior of the individual occupants and EV owners.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2013

Templated Self Assemble of Nano-Structures

This project will identify and model mechanisms that template the self-assembly of nanostructures. We focus on a class of systems involving a two-phase monolayer of molecules adsorbed on a solid surface. At a suitably elevated temperature, the molecules diffuse on the surface to reduce the combined free energy of mixing, phase boundary, elastic field, and electrostatic field. With no template, the phases may form a pattern of stripes or disks. The feature size is on the order of 1-100 nm, selected to compromise the phase boundary energy and the long-range elastic or electrostatic interaction. Both experimental observations and our theoretical simulations have shown that the pattern resembles a periodic lattice, but has abundant imperfections. To form a perfect periodic pattern, or a designed aperiodic pattern, one must introduce a template to guide the assembly. For example, a coarse-scale pattern, lithographically defined on the substrate, will guide the assembly of the nanoscale pattern. As another example, if the molecules on the substrate surface carry strong electric dipoles, a charged object, placed in the space above the monolayer, will guide the assembly of the molecular dipoles. In particular, the charged object can be a mask with a designed nanoscale topographic pattern. A serial process (e.g., e-beam lithography) is necessary to make the mask, but the pattern transfer to the molecules on the substrate is a parallel process. The technique is potentially a high throughput, low cost process to pattern a monolayer. The monolayer pattern itself may serve as a template to fabricate a functional structure. This project will model fundamental aspects of these processes, including thermodynamics and kinetics of self-assembly, templated self-assembly, and self-assembly on unconventional substrates. It is envisioned that the theory will not only explain the available experimental observations, but also motivate new experiments.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
NASA NTRS1987

Delay line anodes for microchannel-plate spectrometers

A photon-counting readout system for microchannel-plate spectrometers is described that uses a delay line and timing circuit for the wavelength coordinate and a wedge-wedge charge division system for the orthogonal spatial coordinate. A novel zigzag layout allows these two anode patterns to coexist on a common planar substrate and share the charge from each photoevent, thereby simultaneously localizing the photon in each of its two dimensions. Unlike wedge-and-strip or resistive anode encoders, the delay line offers a spatial resolution that is relatively independent of the format length. Unlike discrete anode systems, the delay line readout system's complexity is also independent of the field of view size. These facts make the delay line readout system advantageous in large format detectors. A testbed detector having a delay line propagation speed of 2.2 mm/ns and a time resolution of 33 ps FWHM has been assembled. Ultraviolet testing shows a Gaussian event distribution having a 70-micron FWHM width; the readout system blur contribution is less than 50-micron FWHM.

Lampton, M.↗
DOE OSTI2020

Charge density modulation and defect ordering in the $Na_xMnBi_y$ magnetic semimetal

The I-Mn-V antiferromagnet, NaMnBi, develops a very large positive magnetoresistance (MR) up to 10 000% at 2 K and 9 T in crystals showing a semiconductor-to-metal transition (SMT). In the absence of an SMT, a modest (20%) MR is achieved. Here, we show that upon cooling below the magnetic transition, a spatial modulation appears giving rise to new Bragg peaks due to charge and defect ordering in a checkerboard pattern, with two kinds of modulation vectors, $q_1 = \left( \frac{2}{3}, 0, 1 \right)$ and $q_2 = \left( \frac{2}{3}, \frac{1}{3}, \frac {1}{2} \right)$. This constitutes a superlattice transition ($T_s$) that lowers the symmetry from the high-temperature centrosymmetric $P4/nmm$ to the noncentrosymmetric $P\overline{4}m2$. In crystals with a large MR, a close to room temperature $T_s$ is observed with $q_1$ appearing first, followed by $q_2$. In crystals with low MR, however, $T_s$ is much lower and only $q_1$ is observed. Finally, the charge modulation and spin fluctuations may both contribute to the enhancement of MR.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

Nanoscale measurement of Nernst effect in two-dimensional charge density wave material 1T-TaS 2

Advances in nanoscale material characterization on two-dimensional van der Waals layered materials primarily involve their optical and electronic properties. The thermal properties of these materials are harder to access due to the difficulty of thermal measurements at the nanoscale. In this work, we create a nanoscale magnetothermal device platform to access the basic out-of-plane magnetothermal transport properties of ultrathin van der Waals materials. Specifically, the Nernst effect in the charge density wave transition metal dichalcogenide 1T-TaS 2 is examined on nano-thin flakes in a patterned device structure. It is revealed that near the commensurate charge density wave (CCDW) to nearly commensurate charge density wave (NCCDW) phase transition, the polarity of the Nernst effect changes. Since the Nernst effect is especially sensitive to changes in the Fermi surface, this suggests that large changes are occurring in the out-of-plane electronic structure of 1T-TaS 2 , which are otherwise unresolved in just in-plane electronic transport measurements. This may signal a coherent evolution of out-of-plane stacking in the CCDW! NCCDW transition.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Transition radiation from relativistic electrons crossing a perfectly conducting conical surface: Calculation and experiment

The angular distributions of the transition radiation intensity when a charged particle passes through the vertex of a perfectly conducting conical surface have been calculated. The radiation generated both when the particle exits the conductor and when it falls on the conductor has been considered. The angular distributions of the intensity of the transition radiation generated by a bunch of relativistic electrons have been measured in the millimeter wavelength range. A microtron with a particle energy of 7.4 MeV was the source of electrons. The influence of the particle injection direction and the conical-surface opening angle on the angular distribution of the radiation intensity has been studied. The measurements have shown that the distribution of the radiation generated by a charge when it enters the horn differs significantly in pattern from the distribution when it exits the horn.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Effect of material composition of diamond field emission array cathodes on quality of transversely shaped beams

Diamond field emitter array field emission cathodes (DFEA FECs) are attractive for the next generation of injectors due to their ability to produce transversely shaped beams without the need for complex masking or laser schemes. However, reliability of this cathode technology remains a challenging issue as principal mechanisms guiding and allowing for output beam shaping remained poorly understood. Here, this paper reports the results of testing two DFEA FECs with the same pattern and emitter tip geometry. Although both cathodes were able to sustain gradients of 44 MV/m and produce maximum output integral charge of 0.5 nC per radio frequency pulse, their emission patterns were different. One cathode did not produce a shaped beam, while the other one did. This difference was explained by the extent of the local variations of the diamond material across the arrays as discovered by spatially resolved Raman spectroscopy. The main practical takeaways were (i) tip sharpness was not a prerequisite for producing a shaped beam and instead (ii) material characteristics resulting in different cathode ballast resistance affected emission spatial uniformity across the array and hence the beam shaping.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Charge‐Programmable Photopolymers for 3D Electronics via Additive Manufacturing

Charge‐programmed 3D printing enables the fabrication of 3D electronics with lightweight and high precision via selective patterning of metals. This selective metal deposition is catalyzed by Pd nanoparticles that are specifically immobilized onto the charged surface and promises to fabricate a myriad of complex electronic devices with self‐sensing, actuation, and structural elements assembled in a designed 3D layout. However, the achievable property space and the material‐performance correlation of the charge‐programmed printing remain unexplored. Herein, a series of photo‐curable resins are designed for unveiling how the charge and crosslink densities synergistically impact the nanocatalyst‐guided selective deposition in catalytic efficiency and properties of the 3D printed charge‐programmed architectures, leading to high‐quality 3D patterning of solid and liquid metals. The findings offer a wide tunability of the structural properties of the printed electronics, ranging from stiff to extreme flexibility. Capitalizing on these results, the printing and successful application of an ultralight‐weight and deployable 3D multi‐layer antenna system operating at an ultrahigh‐frequency of 19 GHz are demonstrated.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Neutrino event selection in the MicroBooNE liquid argon time projection chamber using Wire-Cell 3D imaging, clustering, and charge-light matching

An accurate and efficient event reconstruction is required to realize the full scientific capability of liquid argon time projection chambers (LArTPCs). The current and future neutrino experiments that rely on massive LArTPCs create a need for new ideas and reconstruction approaches. Wire-Cell, proposed in recent years, is a novel tomographic event reconstruction method for LArTPCs. The Wire-Cell 3D imaging approach capitalizes on charge, sparsity, time, and geometry information to reconstruct a topology-agnostic 3D image of the ionization electrons prior to pattern recognition. A second novel method, the many-to-many charge-light matching, then pairs the TPC charge activity to the detected scintillation light signal, thus enabling a powerful rejection of cosmic-ray muons in the MicroBooNE detector. A robust processing of the scintillation light signal and an appropriate clustering of the reconstructed 3D image are fundamental to this technique. In this paper, we describe the principles and algorithms of these techniques and their successful application in the MicroBooNE experiment. A quantitative evaluation of the performance of these techniques is presented. Using these techniques, a 95% efficient pre-selection of neutrino charged-current events is achieved with a 30-fold reduction of non-beam-coincident cosmic-ray muons, and about 80% of the selected neutrino charged-current events are reconstructed with at least 70% completeness and 80% purity.

3D imaging↗
DOE OSTI2025

Chirality in the Kagome Metal CsV 3 ⁢Sb 5

Using x-ray photoelectron diffraction (XPD) and angle-resolved photoemission spectroscopy, we study photoemission intensity changes related to changes in the geometric and electronic structure in the kagome metal CsV 3 ⁢Sb 5 upon transition to an unconventional charge density wave (CDW) state. The XPD patterns reveal the presence of a chiral atomic structure in the CDW phase. Furthermore, using circularly polarized x-rays, we have found a pronounced nontrivial circular dichroism in the angular distribution of the valence band photoemission in the CDW phase, indicating a chirality of the electronic structure. This observation is consistent with the proposed orbital loop current order. In view of a negligible spontaneous Kerr signal in recent magneto-optical studies, the results suggest an antiferromagnetic coupling of the orbital magnetic moments along the 𝑐 axis. Here, while the inherent structural chirality may also induce circular dichroism, the observed asymmetry values seem to be too large in the case of the weak structural distortions caused by the CDW.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Quantifying the Effect of Fast Charger Deployments on Electric Vehicle Utility and Travel Patterns via Advanced Simulation: Preprint

The disparate characteristics between conventional (CVs) and battery electric vehicles (BEVs) in terms of driving range, refill/recharge time, and availability of refuel/recharge infrastructure inherently limit the relative utility of BEVs when benchmarked against traditional driver travel patterns. However, given a high penetration of high-power public charging combined with driver tolerance for rerouting travel to facilitate charging on long-distance trips, the difference in utility between CVs and BEVs could be marginalized. We quantify the relationships between BEV utility, the deployment of fast chargers, and driver tolerance for rerouting travel and extending travel durations by simulating BEVs operated over real-world travel patterns using the National Renewable Energy Laboratory's Battery Lifetime Analysis and Simulation Tool for Vehicles (BLAST-V). With support from the U.S. Department of Energy's Vehicle Technologies Office, BLAST-V has been developed to include algorithms for estimating the available range of BEVs prior to the start of trips, for rerouting baseline travel to utilize public charging infrastructure when necessary, and for making driver travel decisions for those trips in the presence of available public charging infrastructure, all while conducting advanced vehicle simulations that account for battery electrical, thermal, and degradation response. Results from BLAST-V simulations on vehicle utility, frequency of inserted stops, duration of charging events, and additional time and distance necessary for rerouting travel are presented to illustrate how BEV utility and travel patterns can be affected by various fast charge deployments.

25 ENERGY STORAGE↗
NASA NTRS1977

Surface micro-discharges on spacecraft dielectrics

Extensive measurements on Teflon and Kapton in a scanning electron microscope indicate the existence of a well-defined family of surface micro-discharges characteristic of the dielectric material. For a given small region exposed to the 16-20 kV electron beam, the strongest discharge pulses are similar in shape and amplitude. For Teflon, typical pulse durations are 2-3 ns, rise and fall times are sometimes as low as 0.2 ns, current amplitudes are approximately 100 mA flowing down to the pedestal and the pulses are unidirectional with no ringing. The use of a rapid-scan electron microscope with a secondary-electron imaging system reveals complex charge distributions resembling Lichtenberg figures on a supposedly flat homogeneous dielectric surface. These patterns undergo extensive alteration at each micro-discharge pulse and indicate that both the charging and discharging processes are highly nonuniform over the dielectric surface. The use of floodbeam causes the occurrence of a large-scale macro-discharges, in which a typical peak current is 40 A with a duration of 120 ns.

Balmain, K. G.↗
DOE OSTI2018

Optimization Methods for Evaluating PEV Charging Considering Customer Behavior

Plug-in electric vehicles (PEVs) can be connected to grid through electrical vehicle supply equipment (EVSE) to provide various grid services in addition to battery charging. This paper evaluates loading condition of a distribution system with a medium penetration of PEVs considering different charging strategies and public EVSE availability. A mobility and charging flexibility model is proposed to capture PEVs’ temporal availability and varying charging capability at different parking locations. Detailed trip information extracted from the National Household Travel Survey is used to represent travel and parking patterns. An optimization method is then proposed to coordinate PEV charging to effectively shift load from peak to off-peak hours. One of the prototypical feeders developed by the Pacific Northwest National Laboratory is studied in different scenarios.

Wu, Di↗
DOE OSTI2013

Scrape-off layer flows with pressure gradient scale length ~ ρ p

A heuristic model for the plasma scrape-off width balances magnetic drifts against parallel loss at c s /2, resulting in a SOL width ~ ρ p . T sep is calculated from Spitzer–Härm parallel thermal conduction. This results in a prediction for the power scrape-off width in quantitative agreement both in magnitude and scaling with recent experimental data. To achieve the ~ c s /2 flow assumed in this model and measured experimentally sets requirements on the ratio of upstream to total SOL particle sources, relative to the square-root of the ratio of target to upstream temperature. The Pfisch-Schlüter model for equilibrium flows has been modified to allow near-sonic flows, appropriate for gradient scale lengths of order ρ p , resulting in a new quadrupole radial flow pattern. The strong parallel flows and plasma charging implied by this model suggest a mechanism for H-mode transition, consistent with many observations

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2014

Final Report, DOE grant DE-FG02-99ER45780, "Indirect Excitons in Coupled Quantum Wells"

The is the final technical report for this project, which was funded by the DOE from 1999 to 2012. The project focused on experimental studies of spatially indirect excitons in coupled quantum wells, with the aim of understanding the quantum physics of these particles, including such effects as pattern formation due to electron-hole charge separation, the Mott plasma-insulator transition, luminescence up-conversion through field-assisted tunneling, luminescence line shifts due to many-body renormalization and magnetic field effects on tunneling, and proposed effects such as Bose-Einstein condensation of indirect excitons and phase separation of bright and dark indirect excitons. Significant results are summarized here and the relation to other work is discussed.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Four Beam Generation for Simultaneous Four-Hall Operation at CEBAF

As part of the CEBAF 12 GeV upgrade at Jefferson Lab, a new experimental hall was added to the existing three halls. To deliver beam to all four halls simultaneous-ly, a new timing pattern for electron bunches is needed at the injector. This pattern change has consequences for the frequency of the lasers at the photogun, beam behavior in the chopping system, beam optics due to space charge, and setup procedures. We have successfully demonstrated this new pattern using the three existing drive lasers. The implementation of the full system will occur when the fourth laser is added and upgrades to the Low Level RF (LLRF) are complete. In this paper we explain the new bunch pattern, the challenges for setting and measuring the pattern such as 180° RF phase ambiguity, addition of the fourth laser to the laser table and LLRF upgrade.

Kazimi, Reza↗