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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 649 records · Page 36
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Note: A non-invasive electronic measurement technique to measure the embedded four resistive elements in a Wheatstone bridge sensor

The work shows a measurement technique to obtain the correct value of the four elements in a resistive Wheatstone bridge without the need to separate the physical connections existing between them. Two electronic solutions are presented, based on a source-and-measure unit and using discrete electronic components. The proposed technique brings the possibility to know the mismatching or the tolerance between the bridge resistive elements and then to pass or reject it in terms of its related common-mode rejection. Experimental results were taken in various Wheatstone resistive bridges (discrete and magnetoresistive integrated bridges) validating the proposed measurement technique specially when the bridge is micro-fabricated and there is no physical way to separate one resistive element from the others.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2015

Raman spectroscopy measurement of bilayer graphene's twist angle to boron nitride

When graphene is placed on hexagonal boron nitride with a twist angle, new properties develop due to the resulting moiré superlattice. Here, we report a method using Raman spectroscopy to make rapid, non-destructive measurements of the twist angle between bilayer graphene and hexagonal boron nitride. The lattice orientation is determined by using flakes with both bilayer and monolayer regions, and using the known Raman signature for the monolayer to measure the twist angle of the entire flake. The widths of the second order Raman peaks are found to vary linearly in the superlattice period and are used to determine the twist angle. The results are confirmed by using transport measurements to infer the superlattice period by the charge density required to reach the secondary resistance peaks. Small twist angles are also found to produce a significant modification of the first order Raman G band peak.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Variable location channels to improve efficiency and precision for direct ∇ T e measurements and high spatial resolution T e -profile measurements using electron cyclotron emission

Electron cyclotron emission (ECE) diagnostics that use variable location channels based on yttrium iron garnet (YIG) bandpass filters improve the precision and the efficiency of measurements of electron temperature (T e ) profiles and fluctuations (δT e ). These variable frequency filters were substituted for fixed frequency filters in the intermediate frequency section to achieve the required higher resolution over a target radial range, just before the experiment. In this paper, we present the proof-of-principle for high temporal resolution measurement of the electron temperature gradient, via real-time slewing of a YIG filter for relocation of an ECE channel during a long pulse. The key component is the application of YIG tunable filters with their narrow bandwidth and capability for a high slew rate of their center frequency. This application permits fast relocation of the ECE channels for direct measurement of the gradient and close spacing of channels to investigate the magnetic island’s dynamic behavior.

47 OTHER INSTRUMENTATION↗
DOE OSTI2018

Measurements of the effective electron density in an electron beam ion trap using extreme ultraviolet spectra and optical imaging

In an electron beam ion trap (EBIT), the ions are not confined to the electron beam, but rather oscillate in and out of the beam. As a result, the ions do not continuously experience the full density of the electron beam. To determine the effective electron density, n e,eff , experienced by the ions, the electron beam size, the nominal electron density n e , and the ion distribution around the beam, i.e., the so-called ion cloud, must be measured. We use imaging techniques in the extreme ultraviolet (EUV) and optical to determine these. The electron beam width is measured using 3 d → 3 p emission from Fe xii and xiii between 185 and 205 Å. These transitions are fast and the EUV emission occurs only within the electron beam. The measured spatial emission profile and variable electron current yield a nominal electron density range of n e ~ 10 11 –10 13 cm –3 . We determine the size of the ion cloud using optical emission from metastable levels of ions with radiative lifetimes longer than the ion orbital periods. Here, the resulting emission maps out the spatial distribution of the ion cloud. We find a typical electron beam radius of ~60 μm and an ion cloud radius of ~300 μ m. These yield a spatially averaged effective electron density, ne,eff, experienced by the ions in EBIT spanning ~ 5 × 10 9 –5 × 10 11 cm –3 .

47 OTHER INSTRUMENTATION↗
DOE OSTI2020

A broadband wavelet implementation for rapid ultrasound pulse-echo time-of-flight measurements

A broadband wavelet approach to ultrasonic pulse-echo time-of-flight measurements is described. The broadband approach significantly reduces the time required for frequency-dependent pulse-echo measurements, enabling studies of dynamic systems ranging from biological systems to solid-state phase transitions. The described broadband approach is demonstrated in parallel with the more traditional frequency stepping approach to perform ultrasound time-of-flight measurements inside a large volume Paris-Edinburgh press in-situ at a synchrotron source. The broadband wavelet data acquisition process was found to be 1-2 orders of magnitude faster than the steppedfrequency approach, with no compromise in data quality or determined results.

47 OTHER INSTRUMENTATION↗
DOE OSTI2014

Measurement of the cross-section of high transverse momentum vector bosons reconstructed as single jets and studies of jet substructure in pp collisions at √s = 7 TeV with the ATLAS detector

This article presents a measurement of the cross-section for high transverse momentum W and Z bosons produced in pp collisions and decaying to all-hadronic final states. The data used in the analysis were recorded by the ATLAS detector at the CERN Large Hadron Collider at a centre-of-mass energy of $\sqrt{s}=7\;{\rm Te}{\rm V}$ and correspond to an integrated luminosity of $4.6\;{\rm f}{{{\rm b}}^{-1}}$. The measurement is performed by reconstructing the boosted W or Z bosons in single jets. The reconstructed jet mass is used to identify the W and Z bosons, and a jet substructure method based on energy cluster information in the jet centre-of-mass frame is used to suppress the large multi-jet background. The cross-section for events with a hadronically decaying W or Z boson, with transverse momentum ${{p}_{{\rm T}}}\gt 320\;{\rm Ge}{\rm V}$ and pseudorapidity $|\eta |\lt 1.9$, is measured to be ${{\sigma }_{W+Z}}=8.5\pm 1.7$ pb and is compared to next-to-leading-order calculations. The selected events are further used to study jet grooming techniques.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Cosmic-muon characterization and annual modulation measurement with Double Chooz detectors

A study on cosmic muons has been performed for the two identical near and far neutrino detectors of the Double Chooz experiment, placed at ∼120 and ∼300 m.w.e. underground respectively, including the corresponding simulations using the MUSIC simulation package. This characterization has allowed us to measure the muon flux reaching both detectors to be (3.64 ± 0.04) × 10{sup −4} cm{sup −2}s{sup −1} for the near detector and (7.00 ± 0.05) × 10{sup −5} cm{sup −2}s{sup −1} for the far one. The seasonal modulation of the signal has also been studied observing a positive correlation with the atmospheric temperature, leading to an effective temperature coefficient of α {sub T} = 0.212 ± 0.024 and 0.355 ± 0.019 for the near and far detectors respectively. These measurements, in good agreement with expectations based on theoretical models, represent one of the first measurements of this coefficient in shallow depth installations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

A new measure of tension between experiments

Tensions between cosmological measurements by different surveys or probes have always been important —and are presently much discussed —as they may lead to evidence of new physics. Several tests have been devised to probe the consistency of datasets given a cosmological model, but they often have undesired features such as dependence on the prior volume, or burdensome requirements such as that of near-Gaussian posterior distributions. We propose a new quantity, defined in a similar way as the Bayesian evidence ratio, in which these undesired properties are absent. We test the quantity on simple models with Gaussian and non-Gaussian likelihoods. Here, we then apply it to data from the Planck satellite: we investigate the consistency of ΛCDM model parameters obtained from TT and EE angular power spectrum measurements, as well as the mutual consistency of cosmological parameters obtained from large scale (multipoles, ℓ<1000) and small scale (ℓ ≥ 1000) portions of each measurement and find no significant discrepancy in the six-dimensional ΛCDM parameter space.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2019

Electron and photon performance measurements with the ATLAS detector using the 2015–2017 LHC proton-proton collision data

This paper describes the reconstruction of electrons and photons with the ATLAS detector, as employed for measurements and searches exploiting the complete LHC Run 2 dataset. An improved energy clustering algorithm is introduced, and its implications for the measurement and identification of electrons and photons are discussed in detail. Corrections and calibrations that affect performance, including energy calibration, identification and isolation efficiencies, and the measurement of the charge of reconstructed electron candidates are determined using up to 81 fb -1 of proton-proton collision data collected at $\sqrt{s}=$ 13 TeV between 2015 and 2017.

47 OTHER INSTRUMENTATION↗
DOE OSTI2011

Absolute high-resolution Se{sup +} photoionization cross-section measurements with Rydberg-series analysis

Absolute single photoionization cross-section measurements for Se{sup +} ions were performed at the Advanced Light Source (ALS) at Lawrence Berkeley National Laboratory using the photo-ion merged-beams technique. Measurements were made at a photon energy resolution of 5.5 meV from 17.75 to 21.85 eV spanning the 4s{sup 2}4p{sup 3} {sup 4}S{sub 3/2}{sup o} ground-state ionization threshold and the {sup 2}P{sub 3/2}{sup o},{sup 2}P{sub 1/2}{sup o},{sup 2}D{sub 5/2}{sup o}, and{sup 2}D{sub 3/2}{sup o} metastable state thresholds. Extensive analysis of the complex resonant structure in this region identified numerous Rydberg series of resonances and obtained the Se{sup 2+} 4s{sup 2}4p{sup 23}P{sub 2} and 4s{sup 2}4p{sup 21}S{sub 0} state energies. In addition, particular attention was given to removing significant effects in the measurements due to a small percentage of higher-order undulator radiation.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2011

Effect of fluctuation measures on the uncertainty relations between two observables: Different measures lead to opposite conclusions

We show within a very simple framework that different measures of fluctuations lead to uncertainty relations resulting in contradictory conclusions. More specifically we focus on Tsallis and Renyi entropic uncertainty relations and we get that the minimum joint uncertainty states for some fluctuation measures are the maximum joint uncertainty states of other fluctuation measures, and vice versa.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Direct measurement of the static and transient magneto-optical permittivity of cobalt across the entire M -edge in reflection geometry by use of polarization scanning

The microscopic state of a magnetic material is characterized by its resonant magneto-optical response through the off-diagonal dielectric tensor component ε xy . However, the measurement of the full complex ε xy in the extreme ultraviolet spectral region covering the M absorption edges of 3d ferromagnets is challenging due to the need for either a careful polarization analysis, which is complicated by a lack of efficient polarization analyzers, or scanning the angle of incidence in fine steps. Here, we propose and demonstrate a technique to extract the complex resonant permittivity ε xy simply by scanning the polarization angle of linearly polarized high harmonics to measure the magneto-optical asymmetry in reflection geometry. Because this technique is more practical and faster to experimentally implement than previous approaches, we can directly measure the full time evolution of ε xy (t) during laser-induced demagnetization across the entire M 2,3 absorption edge of cobalt with femtosecond time resolution. We find that for polycrystalline Co films on an insulating substrate, the changes in ε xy are uniform throughout the spectrum, to within our experimental precision. This result suggests that, in the regime of strong demagnetization, the ultrafast demagnetization response is primarily dominated by magnon generation. Here, we estimate the contribution of exchange-splitting reduction to the ultrafast demagnetization process to be no more than 25%.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Measurement of event-plane correlations in s NN = 2.76 TeV lead-lead collisions with the ATLAS detector

A measurement of event-plane correlations involving two or three event planes of different order is presented as a function of centrality for 7 μb -1 Pb+Pb collision data at s NN = 2.76 TeV, recorded by the ATLAS experiment at the Large Hadron Collider. Fourteen correlators are measured using a standard event-plane method and a scalar-product method, and the latter method is found to give a systematically larger correlation signal. Several different trends in the centrality dependence of these correlators are observed. These trends are not reproduced by predictions based on the Glauber model, which includes only the correlations from the collision geometry in the initial state. Calculations that include the final-state collective dynamics are able to describe qualitatively, and in some cases also quantitatively, the centrality dependence of the measured correlators. These observations suggest that both the fluctuations in the initial geometry and the nonlinear mixing between different harmonics in the final state are important for creating these correlations in momentum space.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Measurement of the 169 Tm(n,3n) 167 Tm cross section and the associated branching ratios in the decay of 167 Tm [Measurement of the 169 Tm(n,3n) 167 Tm cross section and the branching ratios in the decay of 167 Tm]

The cross section for the 169 Tm(n,3n) 167 Tm reaction was measured from 17 to 22 MeV using quasimonoenergetic neutrons produced by the 2 H(d,n) 3 He reaction. This energy range was studied to resolve the discrepancy between previous (n,3n) cross-section measurements. In addition, the absolute γ-ray branching ratios following the electron-capture decay of 167 Tm were measured. Furthermore, these results provide more reliable nuclear data for an important diagnostic that is used at the National Ignition Facility to estimate the yield of reaction-in-flight neutrons produced via the inertial-confinement-fusion plasma in deuterium-tritium capsules.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗