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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 955 records · Page 53
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Room Temperature Measurements of Higher Order Modes for the SPS Prototype RF-Dipole Crabbing Cavity

LHC High Luminosity Upgrade will be developing two local crabbing systems to increase the luminosity of the colliding bunches at the ATLAS and CMS experiments. One of the crabbing systems uses the rf-dipole cavity design that will be crabbing the beam in the horizontal plane. The fully integrated crabbing cavity has two higher order mode couplers in damping those excited modes. Currently two sets of HOM couplers have been fabricated at Jefferson Lab for prototyping and testing with the LARP crabbing cavities. This paper presents the measurements of the higher order modes with the prototype HOM couplers carried out at room temperature.

de Silva, SUbashini U.↗
DOE OSTI2015

Security camera resolution measurements: Horizontal TV lines versus modulation transfer function measurements.

The horizontal television lines (HTVL) metric has been the primary quantity used by division 6000 related to camera resolution for high consequence security systems. This document shows HTVL measurements are fundamen- tally insufficient as a metric to determine camera resolution, and propose a quantitative, standards based methodology by measuring the camera system modulation transfer function (MTF), the most common and accepted metric of res- olution in the optical science community. Because HTVL calculations are easily misinterpreted or poorly defined, we present several scenarios in which HTVL is frequently reported, and discuss their problems. The MTF metric is discussed, and scenarios are presented with calculations showing the application of such a metric.

47 OTHER INSTRUMENTATION↗
DOE OSTI2019

Direct Feed Low-Activity Waste Physical Property and Analyte Measurement Reduction: Recommendations for Measurement Removal

Processing of low-activity waste feed will occur at the Hanford Tank Waste Treatment and Immobilization Plant (WTP). In support of plant operations, and per requirements from the WTP contract, feed sample analyses will occur at least 18,000 times per year generating over 7,000 liters of waste. The analytical measurements are often complicated by issues such as lack of standards, low concentrations, and difficult separations. Previous work has been completed to suggest removal of physical property and elemental analyses from required measurements and this document summarizes that work.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2017

Coincidence of the Measured Voltage Peak and the Measured Current Inflection Point in Exploding Metals

Exploding Bridgewire (EBW) Detonators and Exploding Foil Initiators (EFI's, e.g. Slappers) have unique current and voltage characteristics marked by a large voltage spike and an inflection point in the current. Mathematically, it is shown that the voltage peak and the current inflection point must align in time. Models concur with the math and show voltage peaks occurring at the same point in time as the inflection point. Circuit analysis is performed to demonstrate why the voltage peak and current inflection point will almost never align in time for an experiment. To correctly analyze exploding metal behavior, the current inflection point and voltage peak must be manually aligned in time. These conclusions apply to single detonators where current and voltage is measured on those detonators. In multi-detonator systems, the conclusions herein apply only for cases where current and voltage are obtained for each detonator individually. The conclusions will begin to break down as measurements become combined.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Consequences of CCD imperfections for cosmology determined by weak lensing surveys: from laboratory measurements to cosmological parameter bias

Weak gravitational lensing causes subtle changes in the apparent shapes of galaxies due to the bending of light by the gravity of foreground masses. By measuring the shapes of large numbers of galaxies (millions in recent surveys, up to tens of billions in future surveys) we can infer the parameters that determine cosmology. Imperfections in the detectors used to record images of the sky can introduce changes in the apparent shapes of galaxies, which in turn can bias the inferred cosmological parameters. In this paper we consider the effect of two widely discussed sensor imperfections: tree rings, due to impurity gradients that cause transverse electric fields in the charge-coupled devices (CCDs), and pixel size variation, due to periodic CCD fabrication errors. These imperfections can be observed when the detectors are subject to uniform illumination (flat-field images). We develop methods to determine the spurious shear and convergence (due to the imperfections) from the flat-field images. We calculate how the spurious shear when added to the lensing shear will bias the determination of cosmological parameters. We apply our methods to candidate sensors of the Large Synoptic Survey Telescope (LSST) as a timely and important example, analyzing flat-field images recorded with LSST prototype CCDs in the laboratory. We find that tree rings and periodic pixel size variation present in the LSST CCDs will introduce negligible bias to cosmological parameters determined from the lensing power spectrum, specifically w, Ω{sub m}, and σ{sub 8}.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

The 2.4 μm Galaxy Luminosity Function As Measured Using WISE. I. Measurement Techniques

The astronomy community has at its disposal a large back catalog of public spectroscopic galaxy redshift surveys that can be used for the measurement of luminosity functions (LFs). Utilizing the back catalog with new photometric surveys to maximum efficiency requires modeling the color selection bias imposed on the selection of target galaxies by flux limits at multiple wavelengths. The likelihood derived herein can address, in principle, all possible color selection biases through the use of a generalization of the LF, Φ(L), over the space of all spectra: the spectro-luminosity functional, Ψ[L{sub ν}]. It is, therefore, the first estimator capable of simultaneously analyzing multiple redshift surveys in a consistent way. We also propose a new way of parametrizing the evolution of the classic Schechter function parameters, L {sub ⋆} and ϕ {sub ⋆}, that improves both the physical realism and statistical performance of the model. The techniques derived in this paper are used in a companion paper by Lake et al. to measure the LF of galaxies at the rest-frame wavelength of 2.4 μm using the Widefield Infrared Survey Explorer (WISE).

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

The NANOGrav Nine-year Data Set: Measurement and Analysis of Variations in Dispersion Measures

We analyze dispersion measure (DM) variations of 37 millisecond pulsars in the nine-year North American Nanohertz Observatory for Gravitational Waves (NANOGrav) data release and constrain the sources of these variations. DM variations can result from a changing distance between Earth and the pulsar, inhomogeneities in the interstellar medium, and solar effects. Variations are significant for nearly all pulsars, with characteristic timescales comparable to or even shorter than the average spacing between observations. Five pulsars have periodic annual variations, 14 pulsars have monotonically increasing or decreasing trends, and 14 pulsars show both effects. Of the four pulsars with linear trends that have line-of-sight velocity measurements, three are consistent with a changing distance and require an overdensity of free electrons local to the pulsar. Several pulsars show correlations between DM excesses and lines of sight that pass close to the Sun. Mapping of the DM variations as a function of the pulsar trajectory can identify localized interstellar medium features and, in one case, an upper limit to the size of the dispersing region of 4 au. Four pulsars show roughly Kolmogorov structure functions (SFs), and another four show SFs less steep than Kolmogorov. One pulsar has too large an uncertainty to allow comparisons. We discuss explanations for apparent departures from a Kolmogorov-like spectrum, and we show that the presence of other trends and localized features or gradients in the interstellar medium is the most likely cause.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2018

The 2.4 μ m Galaxy Luminosity Function as Measured Using WISE . III. Measurement Results

The Widefield Infrared Survey Explorer (WISE) satellite surveyed the entire sky multiple times in four infrared wavelengths (3.4, 4.6, 12, and 22 μm). The unprecedented combination of coverage area and depth gives us the opportunity to measure the luminosity function (LF) of galaxies, one of the fundamental quantities in the study of them, at 2.4 μm to an unparalleled level of formal statistical accuracy in the near-infrared. The big advantage of measuring LFs at wavelengths in the window of ≈2–3.5 μm is that it correlates more closely to the total stellar mass in galaxies than others. In this paper we report on the parameters of the 2.4 μm LF of galaxies obtained from applying the spectro-luminosity-functional-based methods to datasets from the previous papers in this series using the mean and covariance of 2.4 μm normalized spectral energy distributions (SEDs) from our previous work. In terms of the single Schechter function parameters evaluated at the present epoch, the combined result is: ${\phi }_{\star }=5.8\,\pm [{0.3}_{\mathrm{stat}},{0.4}_{\mathrm{sys}}]\times {10}^{-3}\,{\mathrm{Mpc}}^{-3}$, ${L}_{\star }=6.4\pm [{0.1}_{\mathrm{stat}},{0.3}_{\mathrm{sys}}]\times {10}^{10}\,{L}_{2.4\mu {\rm{m}}\odot }$ (M$_{\star}$ = -21.67 ± [0.02 stat , 0.05 sys ] AB mag), and $α$ = -1.050 ± [0.004 stat , 0.04 sys ]. The high statistical accuracy comes from combining public redshift surveys with the wide coverage from WISE, and the unevenness in statistical accuracy is a result of our efforts to work around biases of uncertain origin that affect resolved and marginally resolved galaxies. With further refinements, the techniques applied in this work promise to advance the study of the SED of the universe.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

Statistical measurement of the gamma-ray source-count distribution as a function of energy

Statistical properties of photon count maps have recently been proven as a new tool to study the composition of the gamma-ray sky with high precision. We employ the 1-point probability distribution function of six years of Fermi-LAT data to measure the source-count distribution dN/dS and the diffuse components of the high-latitude gamma-ray sky as a function of energy. To that aim, we analyze the gamma-ray emission in five adjacent energy bands between 1 and 171 GeV. It is demonstrated that the source-count distribution as a function of flux is compatible with a broken power law up to energies of ∼50 GeV. The index below the break is between 1.95 and 2.0. For higher energies, a simple power-law fits the data, with an index of 2.2{sub −0.3}{sup +0.7} in the energy band between 50 and 171 GeV. Upper limits on further possible breaks as well as the angular power of unresolved sources are derived. We find that point-source populations probed by this method can explain 83{sub −13}{sup +7}% (81{sub −19}{sup +52}%) of the extragalactic gamma-ray background between 1.04 and 1.99 GeV (50 and 171 GeV). The method has excellent capabilities for constraining the gamma-ray luminosity function and the spectra of unresolved blazars.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

$\beta $ Decays of $^{92}$Rb, $^{96\mathrm {gs}}$Y, and $^{142}$Cs Measured with the Modular Total Absorption Spectrometer and the Influence of $\gamma $ Multiplicity on Total Absorption Spectrometry Measurements

Total absorption spectroscopy is a technique that helps obtain reliable β-feeding patterns of complex decays important for nuclear structure and astrophysics modeling as well as decay heat analysis in nuclear reactors. The need for improved measurements of β-feeding patterns from fission decay products has come to the forefront of experiments that use nuclear reactors as a source of antineutrinos. Furthermore we present more detailed results, in particular the β-decay measurements of 96gs Y, and demonstrate the impact of the β-delayed γ multiplicity on the overall efficiency of Modular Total Absorption Spectrometer used at Oak Ridge National Laboratory to study the decays of fission products abundant during a nuclear fuel cycle.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRS1973

Remote measurement of salinity: Repeated measurements over a single flight line near the Mississippi Sound

Experiments to remotely determine sea water salinity from measurements of the sea surface radiometric temperature over the Mississippi Sound were conducted. The line was flown six times at an altitude of 244 meters. The radiometric temperature of the sea surface was measured in two spectral intervals. The specifications of the equipment and the conditions under which the tests were conducted are described. Results of the tests are presented in the form of graphs.

Thomann, G. C.↗
NASA NTRS1974

Thermal conductivity measurements on Mullite and Silica REI for the Space Shuttle - Complementary guarded hot plate and radical outflow measurements

The materials studied are described along with the apparatus and the experimental techniques employed. The results of the measurements involving two REI Silica materials and a Mod 1 B REI Mullite are listed in a table. Measurements were conducted at unusually high temperature differences to detect 'shine-through' radiation transparency. Photographs are presented of the high-temperature guarded hot plate assembly.

Brazel, J. P.↗
NASA NTRS1976

Methods for testing high voltage connectors in vacuum, measurements of thermal stresses in encapsulated assemblies, and measurement of dielectric strength of electrodes in encapsulants versus radius of curvature

Internal embedment stress measurements were performed, using tiny ferrite core transformers, whose voltage output was calibrated versus pressure by the manufacturer. Comparative internal strain measurements were made by attaching conventional strain gages to the same type of resistors and encapsulating these in various potting compounds. Both types of determinations were carried out while temperature cycling from 77 C to -50 C.

Bever, R. S.↗
NASA NTRS1977

JPL field measurements at the Finney County, Kansas, test site, October 1976: Ground-based microwave radiometric measurements

Microwave brightness temperature measurements were made as part of the Joint Soil Moisture Experiment. These measurements are reported with a description of the JPL microwave radiometry van facility. The data will be used with ground truth data from the test site and microwave data from aircraft overflights to investigate the potential of microwave radiometry for soil moisture remote sensing under field conditions.

Njoku, E. G.↗