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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 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Regulation of Renewable Energy Sources to Optimal Power Flow Solutions Using ADMM

This paper considers power distribution systems featuring renewable energy sources (RESs), and develops a distributed optimization method to steer the RES output powers to solutions of AC optimal power flow (OPF) problems. The design of the proposed method leverages suitable linear approximations of the AC-power flow equations, and is based on the Alternating Direction Method of Multipliers (ADMM). Convergence of the RES-inverter output powers to solutions of the OPF problem is established under suitable conditions on the stepsize as well as mismatches between the commanded setpoints and actual RES output powers. In a broad sense, the methods and results proposed here are also applicable to other distributed optimization problem setups with ADMM and inexact dual updates.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2022

An independent analysis of bias sources and variability in wind plant pre-construction energy yield estimation methods

The wind resource assessment community has long had the goal of reducing the bias between wind plant pre-construction energy yield assessment (EYA) and the observed annual energy production (AEP). This comparison is typically made between the 50% probability of exceedance (P50) value of the EYA and the long-term corrected operational AEP (hereafter OA P50), and is known as the P50 bias. The industry has critically lacked an independent analysis of bias reduction investigated across multiple consultants to identify the greatest sources of uncertainty and variance in the EYA process and the best opportunities for uncertainty reduction. The present study addresses this gap by benchmarking consultant methodologies against each other and against operational data at a scale not seen before in industry collaborations. We consider data from 10 wind plants and evaluate discrepancies between eight consultancies in the steps taken from estimates of gross to net energy. Consultants tend to overestimate the gross energy produced at the turbines and then compensate by further overestimating downstream losses, leading to a mean P50 bias near zero, still with significant variability among the individual wind plants. Within our data sample, we find that consultant estimates of all loss categories, except environmental losses, tend to reduce the project-to-project variability of the P50 bias. The disagreement between consultants, however, remains flat throughout the addition of losses. Finally, we find that differences in consultants’ estimates of project performance can lead to differences up to $10/MWh in the levelized cost of energy for a wind plant.

Todd, Austin C.↗
DOE OSTI2012

Design and operation of the wide angular-range chopper spectrometer ARCS at the Spallation Neutron Source

The wide angular-range chopper spectrometer ARCS at the Spallation Neutron Source (SNS) is optimized to provide a high neutron flux at the sample position with a large solid angle of detector coverage. The instrument incorporates modern neutron instrumentation, such as an elliptically focused neutron guide, high speed magnetic bearing choppers, and a massive array of {sup 3}He linear position sensitive detectors. Novel features of the spectrometer include the use of a large gate valve between the sample and detector vacuum chambers and the placement of the detectors within the vacuum, both of which provide a window-free final flight path to minimize background scattering while allowing rapid changing of the sample and sample environment equipment. ARCS views the SNS decoupled ambient temperature water moderator, using neutrons with incident energy typically in the range from 15 to 1500 meV. This range, coupled with the large detector coverage, allows a wide variety of studies of excitations in condensed matter, such as lattice dynamics and magnetism, in both powder and single-crystal samples. Comparisons of early results to both analytical and Monte Carlo simulation of the instrument performance demonstrate that the instrument is operating as expected and its neutronic performance is understood. ARCS is currently in the SNS user program and continues to improve its scientific productivity by incorporating new instrumentation to increase the range of science covered and improve its effectiveness in data collection.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2012

Source effects in analyzer-based X-ray phase contrast imaging with conventional sources

Several recent papers have shown the implementation of analyzer based X-ray phase contrast imaging (ABI) with conventional X-ray sources. The high flux is always a requirement to make the technique useful for bio-medical applications. Here, we present and discuss three important parameters, which need to be taken into account, when searching for the high flux ABI: anisotropic magnification, double image, and source size spread due to intrinsic dispersive diffraction by asymmetrically cut crystals. These parameters, if not well optimized, may cause important features in the acquired images which can mislead the interpretation. A few ways to minimize these effects are implemented and discussed, including some experimental results.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2013

A large-acceptance beam-deceleration module for retrofitting into ion-source beam lines

We describe a large-acceptance deceleration module capable of decelerating large-emittance full-intensity ion beams typical of ECR ion sources to very low energies with high efficiency. The deceleration module is designed to permit convenient retrofitting into an existing beam line to replace, e.g., the first Faraday cup after magnetic analysis of the beam extracted from the ion source. For starting energies of 10 keV, and incident ion currents as large as 300 {mu}A, deceleration efficiencies have been measured to be greater than 80% for final energies as low as 70 eV. The decelerated beam intensity can be monitored either by insertion of a beam catcher floating at the final deceleration voltage or from the current to the exit grid itself, with suitable correction applied for the grid transparency factor. The behavior of the deceleration optics was modeled using SIMION, incorporating the effects of intra-beam space charge repulsion. We describe a recent application of this deceleration module to study near-surface He bubble and blister formation of a W target heated to 1250 K and irradiated with a 98 eV He ion beam with a flux of {approx}10{sup 16} cm{sup -2} s{sup -1}.

43 PARTICLE ACCELERATORS↗
DOE OSTI2014

Contrasting physics in wire array z pinch sources of 1-20 keV emission on the Z facility

Imploding wire arrays on the 20 MA Z generator have recently provided some of the most powerful and energetic laboratory sources of multi-keV photons, including ∼375 kJ of Al K-shell emission (hν ∼ 1–2 keV), ∼80 kJ of stainless steel K-shell emission (hν ∼ 5–9 keV) and a kJ-level of Mo K-shell emission (hν ∼ 17 keV). While the global implosion dynamics of these different wire arrays are very similar, the physical process that dominates the emission from these x-ray sources fall into three broad categories. Al wire arrays produce a column of plasma with densities up to ∼3 × 10{sup 21} ions/cm{sup 3}, where opacity inhibits the escape of K-shell photons. Significant structure from instabilities can reduce the density and increase the surface area, therefore increase the K-shell emission. In contrast, stainless steel wire arrays operate in a regime where achieving a high pinch temperature (achieved by thermalizing a high implosion kinetic energy) is critical and, while opacity is present, it has less impact on the pinch emissivity. At higher photon energies, line emission associated with inner shell ionization due to energetic electrons becomes important.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2014

Operation of an ungated diamond field-emission array cathode in a L-band radiofrequency electron source

We report on the operation of a field-emitter-array cathode in a conventional L-band radio-frequency electron source. The cathode consisted of an array of ∼10{sup 6} diamond tips on pyramids. Maximum current on the order of 15 mA was reached and the cathode did not show appreciable signs of fatigue after weeks of operation. The measured Fowler-Nordheim characteristics, transverse beam density, and current stability are discussed.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Characterization of spatially resolved high resolution x-ray spectrometers for high energy density physics and light source experiments

A high resolution 1D imaging x-ray spectrometer concept comprising a spherically bent crystal and a 2D pixelated detector is being optimized for diagnostics of small sources such as high energy density physics (HEDP) and synchrotron radiation or x-ray free electron laser experiments. This instrument is used on tokamak experiments for Doppler measurements of ion temperature and plasma flow velocity profiles. Laboratory measurements demonstrate a resolving power, E/ΔE of order 10 000 and spatial resolution better than 10 μm. Initial tests of the high resolution instrument on HEDP plasmas are being performed.

43 PARTICLE ACCELERATORS↗
DOE OSTI2014

Vertically polarizing undulator with the dynamic compensation of magnetic forces for the next generation of light sources

A short prototype (847-mm-long) of an Insertion Device (ID) with the dynamic compensation of ID magnetic forces has been designed, built, and tested at the Advanced Photon Source (APS) of the Argonne National Laboratory. The ID magnetic forces were compensated by the set of conical springs placed along the ID strongback. Well-controlled exponential characteristics of conical springs permitted a very close fit to the ID magnetic forces. Several effects related to the imperfections of actual springs, their mounting and tuning, and how these factors affect the prototype performance has been studied. Finally, series of tests to determine the accuracy and reproducibility of the ID magnetic gap settings have been carried out. Based on the magnetic measurements of the ID B{sub eff}, it has been demonstrated that the magnetic gaps within an operating range were controlled accurately and reproducibly within ±1 μm. Successful tests of this ID prototype led to the design of a 3-m long device based on the same concept. The 3-m long prototype is currently under construction. It represents R and D efforts by the APS toward APS Upgrade Project goals as well as the future generation of IDs for the Linac Coherent Light Source (LCLS)

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2015

Reduction of beam current noise in the FNAL magnetron ion source

The new FNAL Injector Line with a circular dimple magnetron ion source has been operational since December of 2012. Since the new injector came on line there have been variations in the H- beam current flattop observed near the downstream end of the Linac. Several different cathode geometries including a hollow cathode suggested by Dudnikov [1] were tried. Previous studies also showed that different mixtures of hydrogen and nitrogen had an effect on beam current noise [2]. We expanded on those studies by trying mixtures ranging from (0.25% nitrogen, 99.75% hydrogen) to (3% nitrogen, 97% hydrogen). The results of these studies in our test stand will be presented in this paper.

43 PARTICLE ACCELERATORS↗
DOE OSTI2016

An overview of the new test stand for H{sup −} ion sources at FNAL

A new test stand at Fermi National Accelerator Laboratory (FNAL) is being constructed to carry out experiments to develop and upgrade the present magnetron-type sources of H{sup −} ions of up to 80 mA at 35 keV in the context of the Proton Improvement Plan. The aim of this plan is to provide high-power proton beams for the experiments at FNAL. The technical details of the construction and layout of this test stand are presented, along with a prospective set of diagnostics to monitor the sources.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

Liquid metal ion source assembly for external ion injection into an electron string ion source (ESIS)

An assembly for a commercial Ga{sup +} liquid metal ion source in combination with an ion transportation and focusing system, a pulse high-voltage quadrupole deflector, and a beam diagnostics system has been constructed in the framework of the iThemba LABS (Cape Town, South Africa)—JINR (Dubna, Russia) collaboration. First, results on Ga{sup +} ion beam commissioning will be presented. Outlook of further experiments for measurements of charge breeding efficiency in the electron string ion source with the use of external injection of Ga{sup +} and Au{sup +} ion beams will be reported as well.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

Review of laser produced multi-keV X-ray sources from metallic foils, cylinders with liner, and low density aerogels

Experimental results obtained within the last fifteen years on multi-keV X-ray sources irradiated with nanosecond scale pulse duration 3ω laser light at TW power levels by CEA and collaborators are discussed in this review paper. Experiments were carried out on OMEGA and GEKKO XII laser facilities where emitting materials in the 5–10 keV multi-keV energy range are intermediate Z value metals from titanium to germanium. Results focused on conversion efficiency improvement by a factor of 2 when an underdense plasma is created using a laser pre-pulse on a metallic foil, which is then heated by a second laser pulse delayed in time. Metal coated inner surface walls of plastic cylindrical tube ablated by laser beam impacts showed that plasma confinement doubles X-ray emission duration as it gives adequate plasma conditions (electron temperature and density) over a long period of time. Low-density aerogels (doped with metal atoms uniformly distributed throughout their volume or metal oxides) contained in a plastic cylinder have been developed and their results are comparable to gas targets. A hybrid target concept consisting of a thin metal foil placed at the end of a cylinder filled with low density aerogel has emerged as it could collect benefits from pre-exploded thin foils, efficient laser absorption in aerogel, and confinement by cylinder walls. All target geometry performances are relatively close together at a given photon energy and mainly depend on laser irradiation condition optimizations. Results are compared with gas target performances from recent NIF experiments allowing high electron temperatures over large dimension low density plasmas, which are the principal parameters for efficient multi-keV X-ray production.

Girard, Frédéric↗
DOE OSTI2016

Dynamics of ion beam charge neutralization by ferroelectric plasma sources

Ferroelectric Plasma Sources (FEPSs) can generate plasma that provides effective space-charge neutralization of intense high-perveance ion beams, as has been demonstrated on the Neutralized Drift Compression Experiment NDCX-I and NDCX-II. This article presents experimental results on charge neutralization of a high-perveance 38 keV Ar + beam by a plasma produced in a FEPS discharge. By comparing the measured beam radius with the envelope model for space-charge expansion, it is shown that a charge neutralization fraction of 98% is attainable with sufficiently dense FEPS plasma. The transverse electrostatic potential of the ion beam is reduced from 15V before neutralization to 0.3 V, implying that the energy of the neutralizing electrons is below 0.3 eV. Measurements of the time-evolution of beam radius show that near-complete charge neutralization is established similar to –5 μs after the driving pulse is applied to the FEPS and can last for 35 μs. It is argued that the duration of neutralization is much longer than a reasonable lifetime of the plasma produced in the sub-mu s surface discharge. Measurements of current flow in the driving circuit of the FEPS show the existence of electron emission into vacuum, which lasts for tens of mu s after the high voltage pulse is applied. Lastly, it is argued that the beam is neutralized by the plasma produced by this process and not by a surface discharge plasma that is produced at the instant the high-voltage pulse is applied.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2016

Development and implementation of a portable grating interferometer system as a standard tool for testing optics at the Advanced Photon Source beamline 1-BM

We developed a portable X-ray grating interferometer setup as a standard tool for testing optics at the Advanced Photon Source (APS) beamline 1-BM. The interferometer can be operated in phase-stepping, Moiré, or single-grating harmonic imaging mode with 1-D or 2-D gratings. All of the interferometer motions are motorized; hence, it is much easier and quicker to switch between the different modes of operation. A novel aspect of this new instrument is its designed portability. While the setup is designed to be primarily used as a standard tool for testing optics at 1-BM, it could be potentially deployed at other APS beamlines for beam coherence and wavefront characterization or imaging. Herein, the design of the interferometer system is described in detail and coherence measurements obtained at the APS 34-ID-E beamline are presented. The coherence was probed in two directions using a 2-D checkerboard, a linear, and a circular grating at X-ray energies of 8 keV, 11 keV, and 18 keV.

47 OTHER INSTRUMENTATION↗