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Summary Technical Report for the Period July 1, 1956 to September 1, 1956

Description: The activities of the Technical Division, including the HNO/sub 3/ recovery process, a study of UO/sub 3/ factors as related to the production of metal-grade UF/sub 4/, a thermobalance investigation of starch as a reducing agent for UO/sub 3/, reduction of UF/sub 4/ to uranium by a thermite type reaction, melting and casting of Nb-U alloy, uranium recovery from scrap materials, preparation of uranium shot, cal cium reduction of ThO/sub 2/ production of thorium ingots, "wet chemical" and spectrochemical development, ammonia precipitation and filtration studies from uranyl nitrate solutions and preparation of active UO/sub 2/ from UF/sub 6/ are reviewed. (W.L.H.)
Date: October 15, 1956
Creator: Simmons, J. W.
Partner: UNT Libraries Government Documents Department

A Generalized {ital K} Correction for Type Ia Supernovae: Comparing {ital R}-band Photometry Beyond {ital z=9.2} with B,V, and {ital R}-band Nearby Photometry

Description: Photometric measurements show that, as a group, nearby Type Ia supernovae follow similar light curves and reach similar peak magnitudes (Branch & Tammann 1992). Thus, these supernovae may serve as standard candles or calibrated candles at cosmological distances. Magnitudes of local and distant supernovae, both in the same filter band, are compared using a K correction to account for the different spectral regions incident on that filter. A generalized approach compares magnitudes in different bands for the nearby and distant supernovae, bands that are selected to give sensitivity in corresponding regions of the unredshifted and redshifted spectra. Thus, R magnitudes for supernovae at z {approx} 0.5 are compared with B magnitudes of local supernovae. We compute these generalized K corrections over a range of redshifts and bandpass pairs and discuss their advantages over the traditional single-band K correction. In particular, errors near maximum light can be kept below 0.05 mag out to at least z = 0.6, whereas the traditional K correction is less accurate and can be difficult to determine beyond z > 0.2.
Date: November 1, 1995
Creator: Kim, Alex; Goodbar, Ariel & Perlmutter, Saul
Partner: UNT Libraries Government Documents Department

X-ray Photometric Determination of Uranium in Metal Oxides

Description: The following report describes the procedures developed for the x-ray photometric determination of uraniuim in metal oxides and sludge and compares results, precision, and length of time of analyses by the General Electric X-Ray Photometer with analyses by the present titration method.
Date: November 6, 1950
Creator: Lambert, M. C.
Partner: UNT Libraries Government Documents Department

The Analysis of TBP Process Streams for Calcium with the Flame Photometer

Description: Summary: A method was found for determining calcium concentrations in TBP process streams in spite of serious interferences bysodium, ferrous, uranyl, sulfate, phosphate, and sulfamate ions as well as by TBP. The precision attainable varied from sample to sample, depending upon its composition. In general, errors of 20% or greater occurred. The smallest determinable amount of calcium was about 10 mg/1.
Date: February 20, 1953
Creator: Brite, D. W.
Partner: UNT Libraries Government Documents Department

Calibration of the MACHO photometry database

Description: The MACHO Project is a microlensing survey that monitors the brightnesses of -60 million stars in the Large Magellanic Cloud (LMC), Small Magellanic Cloud, and Galactic bulge. The database presently contains more photometric measurements than previously recorded in the history of astronomy. We describe the calibration of the MACHO two-color photometry and transformation to the standard Kron-Cousins V and R system. This allows for proper comparison with all other observations on the Kron-Cousins standard system. The highest precision calibrations are for -9 million stars in the LMC bar. For these stars, independent photometric measurements in field-overlap regions indicate standard deviations {sigma}{sub V} = {sigma}{sub R} = 0.020 mag. Calibrated MACHO photometry data are compared with published photometric sequences and with new Hubble Space Telescope observations. We additionally describe the first application of these calibrated data: the construction of the ´┐Żefficiency´┐Ż color-magnitude diagram which will be used to calculate our experimental sensitivity for detecting microlensing in the LMC.
Date: October 23, 1998
Creator: Alcock, A.
Partner: UNT Libraries Government Documents Department

Compact light source performance in recessed type luminaires

Description: Photometric comparisons were made with an indoor, recessed, type luminaire using incandescent, high intensity discharge and compact fluorescent lamps. The test results show substantial performance advantages, as expected, for the discharge light sources where the efficacy gains can be in the order for 400% even when including the ballast losses associated with the discharge lamps. The candlepower distribution patterns emerging from these luminaries are also different from those associated with the baseline incandescent lamps, and which are in some ways, even more desirable from a uniformity of illuminance perspective. A section on fluorescent lamp starting is also included which describes a system having excellent starting characteristics in terms of electrode starting temperature (RH/RC technique), proper operating frequency to minimize unwanted IR interactions, and satisfactory current crest factor values to help insure life performance.
Date: November 1, 1998
Creator: Hammer, E.E.
Partner: UNT Libraries Government Documents Department


Description: An investigation was conducted to compare the flame emission spectrum of Fe as recorded by the Beckman DU and the ORNL flame spectrophotometers. It was found that the ORNL instrument is best suited to the application. Optimum operating conditions are described as well as results of investigations to determine interferences. (J.R.D.)
Date: May 1, 1959
Creator: Menis, O
Partner: UNT Libraries Government Documents Department

Results of Pulse-Scaling Experiments on Rapid-Growth DKDP Triplers Using the Optical Sciences Laser at 351 nm

Description: Results are reported from recently performed bulk-damage, pulse-scaling experiments on DKDP tripler samples taken from NIF-size, rapid-growth boule BD7. The tests were performed on LLNL's Optical Sciences Laser. A matrix of samples was exposed to single shots at 351 mn (3 {omega}) with average fluences from 4 to 8 J/cm{sup 2} for pulse durations of 1, 3 and 10 ns. The damage sites were scatter-mapped after testing to determine the damage evolution as a function of local beam fluence. The average bulk damage microcavity (pinpoint) density varied nearly linearly with fluence with peak values of approximately 16,000 pp/mm{sup 3} at 1 ns, 10,000 pp/mm{sup 3} at 3 ns and 400 pp/mm{sup 3} at 10 ns for fluences in the 8-10 J/cm{sup 2} range. The average size of a pinpoint was 10(+14,-9) {micro}m at 1 ns, 37 {+-} 20 {micro}m at 3 ns and {approx} 110 {micro}m at 10 ns, although all pulse durations produced pinpoints with a wide distribution of sizes. Analysis of the pinpoint density data yielded pulse-scaling behavior of t{sup 0.35}. Significant planar cracking around the pinpoint as was observed for the 10 ns case but not for the 1 and 3 ns pulses. Crack formation around pinpoints has also been observed frequently for Zeus ADT tests at {approx}8 ns. The high pinpoint densities also lead to significant eruption of near-surface bulk damage. Measurements of the damage site area for surface and bulk gave ratios (A{sub surf}/A{sub bulk}) of 2:1 at 1 ns, 7:1 at 3 ns and 110:1 at 10 ns. Maximum aperture averaged transmission losses on the order 15 percent have been measured by photometry for the worst damage at 1 and 3 ns for beam fluences in the 8-10 J/cm{sup 2} range. Analysis of this data yielded a pulse-scaling behavior of t{sup 0.25} for the ...
Date: December 11, 2000
Creator: Runkel, M; Burnham, A K; Milam, D; Sell, W; Feit, M & Rubenchik, A
Partner: UNT Libraries Government Documents Department

Dithering Strategies and Point-Source Photometry

Description: The accuracy in the photometry of a point source depends on the point-spread function (PSF), detector pixelization, and observing strategy. The PSF and pixel response describe the spatial blurring of the source, the pixel scale describes the spatial sampling of a single exposure, and the observing strategy determines the set of dithered exposures with pointing offsets from which the source flux is inferred. In a wide-field imaging survey, sources of interest are randomly distributed within the field of view and hence are centered randomly within a pixel. A given hardware configuration and observing strategy therefore have a distribution of photometric uncertainty for sources of fixed flux that fall in the field. In this article we explore the ensemble behavior of photometric and position accuracies for different PSFs, pixel scales, and dithering patterns. We find that the average uncertainty in the flux determination depends slightly on dither strategy, whereas the position determination can be strongly dependent on the dithering. For cases with pixels much larger than the PSF, the uncertainty distributions can be non-Gaussian, with rms values that are particularly sensitive to the dither strategy. We also find that for these configurations with large pixels, pointings dithered by a fractional pixel amount do not always give minimal average uncertainties; this is in contrast to image reconstruction for which fractional dithers are optimal. When fractional pixel dithering is favored, a pointing accuracy of better than {approx}0.15 {approx}0.15 pixel width is required to maintain half the advantage over random dithers.
Date: February 22, 2011
Creator: Samsing, Johan & Kim, Alex G
Partner: UNT Libraries Government Documents Department

Feasibility of Measuring the Cosmological Constant [LAMBDA]and Mass Density [Omega]using Type Ia Supernovae

Description: We explore the feasibility of resurrecting the apparent magnitude-redshift relation for a 'standard candle' to measure the cosmological constant and mass density. We show that type Ia supernovae, if measured with 0.15 mag uncertainty out to a redshift of z = 1, may provide a good standard candle or calibrated candle for this purpose. The recent discovery of probable type Ia supernovae in the redshift range z = 0.3 to 0.5 (Perlmutter et al. 1994a, and 1994b) indicates that the flux of optical photons from these events can be measured this accurately. The 7 distant supernovae discovered to date do not by themselves distinguish between different cosmological models, however the further discovery of about 50 type Ia supernovae at redshifts in the range 0.5 < z {approx} 1.0 could strongly constrain the allowed range of these parameters. We estimate that the follow-up photometry necessary for this measurement would be on the order of 20 - 70 hours of time on a lO-meter class telescope at a site with good seeing.
Date: April 1, 1995
Creator: Goobar, A. & Perlmutter, S.
Partner: UNT Libraries Government Documents Department

The All-Wavelength Extended Groth Strip International Survey(AEGIS) Data Sets

Description: In this the first of a series of Letters, we present a description of the panchromatic data sets that have been acquired in the Extended Groth Strip region of the sky. Our survey, the All-wavelength Extended Groth Strip International Survey (AEGIS), is intended to study the physical properties and evolutionary processes of galaxies at z{approx}1. It includes the following deep, wide-field imaging data sets: Chandra/ACIS X-ray (0.5-10 keV), GALEX ultraviolet (1200-2500 Angstroms), CFHT/MegaCam Legacy Survey optical (3600-9000 Angstroms), CFHT/CFH12K optical (4500-9000 Angstroms), Hubble Space Telescope/ACS optical (4400-8500 Angstroms), Palomar/WIRC near-infrared (1.2-2.2 {micro}m), Spitzer/IRAC mid-infrared (3.6-8.0 {micro}m), Spitzer/MIPS far-infrared (24-70 {micro}m), and VLA radio continuum (6-20 cm). In addition, this region of the sky has been targeted for extensive spectroscopy using the DEIMOS spectrograph on the Keck II 10 m telescope. Our survey is compared to other large multiwavelength surveys in terms of depth and sky coverage.
Date: October 13, 2006
Creator: Davis, M.; Guhathakurta, P.; Konidaris, N.P.; Newman, J.A.; Ashby, M.L.N.; Biggs, A.D. et al.
Partner: UNT Libraries Government Documents Department

Near infrared detectors for SNAP

Description: Large format (1k x 1k and 2k x 2k) near infrared detectors manufactured by Rockwell Scientific Center and Raytheon Vision Systems are characterized as part of the near infrared R&D effort for SNAP (the Super-Nova/Acceleration Probe). These are hybridized HgCdTe focal plane arrays with a sharp high wavelength cut-off at 1.7 um. This cut-off provides a sufficiently deep reach in redshift while it allows at the same time low dark current operation of the passively cooled detectors at 140 K. Here the baseline SNAP near infrared system is briefly described and the science driven requirements for the near infrared detectors are summarized. A few results obtained during the testing of engineering grade near infrared devices procured for the SNAP project are highlighted. In particular some recent measurements that target correlated noise between adjacent detector pixels due to capacitive coupling and the response uniformity within individual detector pixels are discussed.
Date: May 23, 2006
Creator: Schubnell, M.; Barron, N.; Bebek, C.; Brown, M.G.; Borysow, M.; Cole, D. et al.
Partner: UNT Libraries Government Documents Department

New resources to explore the old galaxy: Mining the SDSS

Description: The Sloan Digital Sky Survey (SDSS) is collecting photometry and intermediate resolution spectra for {approx} 10{sup 5} stars in the thick-disk and stellar halo of the Milky Way. This massive dataset can be used to infer the properties of the stars that make up these structures, and considerably deepen our vision of the old components of the Galaxy. We devise tools for automatic analysis of the SDSS photometric and spectroscopic data based on plane-parallel line-blanketed LTE model atmospheres and fast optimization algorithms. A preliminary study of about 5000 stars in the Early Data Release gives a hint of the vast amount of information that the SDSS stellar sample contains.
Date: July 1, 2003
Creator: al., C. Allende Prieto et
Partner: UNT Libraries Government Documents Department

The MACHO Project Sample of Galactic Bulge High-Amplitude Scuti Stars: Pulsation Behavior and Stellar Properties

Description: We have detected 90 objects with periods and lightcurve structure similar to those of field {delta} Scuti stars, using the Massive Compact Halo Object (MACHO) Project database of Galactic bulge photometry. If we assume similar extinction values for all candidates and absolute magnitudes similar to those of other field high-amplitude {delta} Scuti stars (HADS), the majority of these objects lie in or near the Galactic bulge. At least two of these objects are likely foreground {delta} Scuti stars, one of which may be an evolved nonradial pulsator, similar to other evolved, disk-population {delta} Scuti stars. We have analyzed the light curves of these objects and find that they are similar to the light curves of field {delta} Scuti stars and the {delta} Scuti stars found by the Optical Gravitational Lens Experiment (OGLE). However, the amplitude distribution of these sources lies between those of low- and high-amplitude {delta} Scuti stars, which suggests that they may be an intermediate population. We have found nine double-mode HADS with frequency ratios ranging from 0.75 to 0.79, four probable double- and multiple-mode objects, and another four objects with marginal detections of secondary modes. The low frequencies (5-14 cycles d{sup -1}) and the observed period ratios of {approx}0.77 suggest that the majority of these objects are evolved stars pulsating in fundamental or first overtone radial modes.
Date: November 16, 1999
Creator: Bennett, D.P.; Cook, K.H.; Freeman, K.C.; Geha, M.; Griest, K.; Lehner, M.J. et al.
Partner: UNT Libraries Government Documents Department

The discovery of high-redshift supernovae and their cosmological implications

Description: In this thesis the author discusses the methodology for doing photometry: from procedure of extracting supernova counts from images that contain combined supernova plus galaxy flux, to standard star calibration, to additional instrumental corrections that arise due to the multiple telescopes used for observations. He discusses the different sources of photometric error and their correlations, and the construction of the covariance matrix for all the points in the light curve. He then describes the K corrections which account for the redshifting of spectra that are necessary to compare the photometry of the high-redshift data with those from nearby (z < 0.1) supernovae. Finally, he uses the first seven of the supernovae to test the hypothesis that they live in an under-dense bubble where the locally measured Hubble constant differs significantly from the true Hubble constant. He also uses the data to place limits on the value of the Hubble constant. Discussions of several other important aspects of the data analysis are or will be included in other papers. These topics include a description of how the covariance matrix is used to generate light-curve fits, a discussion of non-photometric systematic errors that also effect the measurements, and a discussion of the application of the supernovae to address other scientific/cosmological problems.
Date: September 1, 1997
Creator: Kim, A.G.
Partner: UNT Libraries Government Documents Department