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RULLI/a Photon Counting Imager

Description: The Remote Low Light Imaging (RULLI) system responds to individual photons using a modification to conventional image intensifier technology and fast timing electronics. Each photon received at the detector is resolved in three dimensions (X, Y, and time). The accumulation of photons over time allows the system to image with very low light levels, such as starlight illumination. Using a low power pulsed laser and very fine time discrimination, three dimensional imaging has been accomplished with a vertical resolution of five cm.
Date: October 19, 1998
Creator: Albright, K.L.; Smith, R.C.; Ho, C.; Wilson, S.K.; Bradley, J.; Bird, A. et al.
Partner: UNT Libraries Government Documents Department

ChaMP Serendipitous Galaxy Cluster Survey

Description: We present a survey of serendipitous extended X-ray sources and optical cluster candidates from the Chandra Multi-wavelength Project (ChaMP). Our main goal is to make an unbiased comparison of X-ray and optical cluster detection methods. In 130 archival Chandra pointings covering 13 square degrees, we use a wavelet decomposition technique to detect 55 extended sources, of which 6 are nearby single galaxies. Our X-ray cluster catalog reaches a typical flux limit of about {approx} 10{sup -14} erg s{sup -1} cm{sup -2}, with a median cluster core radius of 21''. For 56 of the 130 X-ray fields, we use the ChaMP's deep NOAO/4m MOSAIC g', r', and i' imaging to independently detect cluster candidates using a Voronoi tessellation and percolation (VTP) method. Red-sequence filtering decreases the galaxy fore/background contamination and provides photometric redshifts to z {approx} 0.7. From the overlapping 6.1 square degree X-ray/optical imaging, we find 115 optical clusters (of which 11% are in the X-ray catalog) and 28 X-ray clusters (of which 46% are in the optical VTP catalog). The median redshift of the 13 X-ray/optical clusters is 0.41, and their median X-ray luminosity (0.5-2 keV) is L{sub X} = (2.65 {+-} 0.19) x 10{sup 43} ergs s{sup -1}. The clusters in our sample that are only detected in our optical data are poorer on average ({approx} 4{sigma}) than the X-ray/optically matched clusters, which may partially explain the difference in the detection fractions.
Date: April 3, 2006
Creator: Barkhouse, Wayne A.; Green, P.J.; Vikhlinin, A.; Kim, D.-W.; Perley, D.; Cameron, R. et al.
Partner: UNT Libraries Government Documents Department

PWR shutdown decay-heat removal analyses in support of TAP A-45. [Feed and bleed]

Description: The US NRC currently considers the adequacy of shutdown decay heat removal to be an unresolved safety issue (USI A-45). The purpose of Task Action Plan (TAP) A-45 is to evaluate the adequacy of current licensing design requirements, to ensure that nuclear power plants do not pose an unacceptable risk because of failure to remove shutdown decay heat. A major part of TAP A-45 is concerned with the transition from reactor trip to hot shutdown. Also of interest is the transition from hot shutdown to cold shutdown and maintaining cold shutdown conditions. Although a limited number of alternative means for removal of shutdown decay heat from PWRs are being examined by the NRC, this paper focuses on the application of the feed and bleed concept as a diverse alternative method of removing decay heat that does not rely on the use of the steam generators.
Date: January 1, 1983
Creator: Boyack, B.E.; Henninger, R.J. & Smith, R.C.
Partner: UNT Libraries Government Documents Department

Reduction and Stabilization of Plutonium Nitrate in Cation Exchange Feed and Product Solutions

Description: In the conceutration and purification of Pu by cation exchange, the feed solution must be in the plus three valence state, but the nitrate solution from a solvent extraction process contains a high% of Pu/sup 4+/ and a small amount of Pu/sup 6+/. It was desired to find a reducing agent satisfactory for the reduction of Pu/sup 4+/ and Pu/sup 6+/ in Purex product streams and to make these streams suitable as cation exchange feed. The bisulfates met the requirements for speed and completeness of reduction in the feed material. (J.E.D.)
Date: September 24, 1957
Creator: Brunstad, A. & Smith, R. C.
Partner: UNT Libraries Government Documents Department

SSC high speed communication channel and interconnects

Description: This paper investigates potential metallic and optical technology applications in SSC high speed interconnects and/or communication channels. Primary focus will be placed on evaluating several metallic and optical interconnect structures. 7 refs., 3 figs.
Date: January 1, 1990
Creator: Cooke, B.J.; Smith, R.C. & Wagner, R.
Partner: UNT Libraries Government Documents Department

Lightcurves of Type Ia Supernovae from Near the Time of Explosion

Description: We present a set of 11 type Ia supernova (SN Ia) lightcurves with dense, pre-maximum sampling. These supernovae (SNe), in galaxies behind the Large Magellanic Cloud (LMC), were discovered by the SuperMACHO survey. The SNe span a redshift range of z = 0.11-0.35. Our lightcurves contain some of the earliest pre-maximum observations of SNe Ia to date. We also give a functional model that describes the SN Ia lightcurve shape (in our V R-band). Our function uses the ''expanding fireball'' model of Goldhaber et al. (1998) to describe the rising lightcurve immediately after explosion but constrains it to smoothly join the remainder of the lightcurve. We fit this model to a composite observed V R-band lightcurve of three SNe between redshifts of 0.135 to 0.165. These SNe have not been K-corrected or adjusted to account for reddening. In this redshift range, the observed V R-band most closely matches the rest frame V-band. Using the best fit to our functional description of the lightcurve, we find the time between explosion and observed V R-band maximum to be 19.2 {+-} 1.3-1.6 {+-} 0.07(red.) rest-frame days for a SN Ia with a V R-band {Delta}m{sub -10} of 0.52. For the redshifts sampled, the observed V R-band time-of-maximum brightness should be the same as the rest-frame V -band maximum to within 1.1 rest-frame days.
Date: August 30, 2006
Creator: Garg, A; Stubbs, C W; Challis, P; Wood-Vasey, M; Blondin, S; Huber, M E et al.
Partner: UNT Libraries Government Documents Department

Sub-100 ps bulk-recombination-limited InP:Fe photoconductive detector

Description: Both surface and bulk excited semi-insulating InP optoelectronic switches were studied. It was found that transient recombination in these devices is the same for both types of excitation. It is concluded that the recombination is a bulk controlled process.
Date: January 1, 1981
Creator: Hammond, R.B.; Paulter, N.G.; Iverson, A.E. & Smith, R.C.
Partner: UNT Libraries Government Documents Department

MELCOR 1.8.2 assessment: Surry PWR TMLB` (with a DCH study)

Description: MELCOR is a fully integrated, engineering-level computer code, being developed at Sandia National Laboratories for the USNRC. This code models the entire spectrum of severe accident phenomena in a unified framework for both BWRs and PWRs. As part of an ongoing assessment program, the MELCOR computer code has been used to analyze a station blackout transient in Surry, a three-loop Westinghouse PWR. Basecase results obtained with MELCOR 1.8.2 are presented, and compared to earlier results for the same transient calculated using MELCOR 1.8.1. The effects of new models added in MELCOR 1.8.2 (in particular, hydrodynamic interfacial momentum exchange, core debris radial relocation and core material eutectics, CORSOR-Booth fission product release, high-pressure melt ejection and direct containment heating) are investigated individually in sensitivity studies. The progress in reducing numeric effects in MELCOR 1.8.2, compared to MELCOR 1.8.1, is evaluated in both machine-dependency and time-step studies; some remaining sources of numeric dependencies (valve cycling, material relocation and hydrogen burn) are identified.
Date: February 1, 1994
Creator: Kmetyk, L.N.; Cole, R.K. Jr.; Smith, R.C.; Summers, R.M. & Thompson, S.L.
Partner: UNT Libraries Government Documents Department

TRAC-PF1 analyses of potential pressurized-thermal-shock transients at a Combustion-Engineering PWR. [Overcooling]

Description: Los Alamos is participating in a program to assess the risk of pressurized thermal shock (PTS) to a reactor vessel. Our role is to provide best-estimate thermal-hydraulic analyses of 12 postulated overcooling transients using TRAC-PF1. These transients are hypothetical and include multiple operator/equipment failures. Calvert Cliffs/Unit-1, a Combustion-Engineering plant, is the pressurized water reactor modeled for this study. The utility and the vendor supplied information for the comprehensive TRAC-PF1 model. Secondary and primary breaks from both hot-zero-power and full-power conditions were simulated for 7200 s (2 h). Low bulk temperatures and loop-flow stagnation while the system was at a high pressure were of particular interest for PTS analysis. Three transients produced primary temperatures below 405 K (270/sup 0/F - the NRC screening criterion) with system repressurization. Six transients indicated flow stagnation would occur in one loop but not both. One transient showed flow stagnation might occur in both loops. Oak Ridge National Laboratory will do fracture-mechanics analysis using these TRAC-PF1 results and make the final determination of the risk of PTS.
Date: January 1, 1984
Creator: Koenig, J.E.; Spriggs, G.D. & Smith, R.C.
Partner: UNT Libraries Government Documents Department

The ESSENCE Supernova Survey: Survey Optimization, Observations, and Supernova Photometry

Description: We describe the implementation and optimization of the ESSENCE supernova survey, which we have undertaken to measure the equation of state parameter of the dark energy. We present a method for optimizing the survey exposure times and cadence to maximize our sensitivity to the dark energy equation of state parameter w = P/{rho}c{sup 2} for a given fixed amount of telescope time. For our survey on the CTIO 4m telescope, measuring the luminosity distances and redshifts for supernovae at modest redshifts (z {approx} 0.5 {+-} 0.2) is optimal for determining w. We describe the data analysis pipeline based on using reliable and robust image subtraction to find supernovae automatically and in near real-time. Since making cosmological inferences with supernovae relies crucially on accurate measurement of their brightnesses, we describe our efforts to establish a thorough calibration of the CTIO 4m natural photometric system. In its first four years, ESSENCE has discovered and spectroscopically confirmed 102 type Ia SNe, at redshifts from 0.10 to 0.78, identified through an impartial, effective methodology for spectroscopic classification and redshift determination. We present the resulting light curves for the all type Ia supernovae found by ESSENCE and used in our measurement of w, presented in Wood-Vasey et al. (2007).
Date: January 8, 2007
Creator: Miknaitis, Gajus; Pignata, G.; Rest, A.; Wood-Vasey, W. M.; Blondin, S.; Challis, P. et al.
Partner: UNT Libraries Government Documents Department

100 MHz fiber optic single transient gamma ray detection system

Description: A fiber optic system has been developed to measure single transient gamma rays. The gamma ray signature is converted to light by the Cerenkov process in a 20 cm length of radiation resistant optical fiber. The signal is transmitted over 1 km of optical fiber and detected by state-of-the-art, 175 MHz analog receivers. The receivers are based on silicon PIN detectors with transimpedance hybrid amplifiers and two stages of power amplification. The dc coupled receivers have less than 2% distortion up to 5 volts with less than 10 mV rms noise and a responsivity of 37,500 V/watt at 800 nm. A calibration system measures relative fiber to fiber transit time delays and ''system'' sensitivity. System bandwidth measurements utilized an electron linear accelerator (Linac) with a 50 ps electron pulse as the Cerenkov light source. The system will be described with supporting calibrationa and characterization data of parts of the system and the whole system.
Date: January 1, 1984
Creator: Ogle, J.W.; Smith, R.C.; Ward, M.; Ramsey, R. & Hollabaugh, J.
Partner: UNT Libraries Government Documents Department


Description: We report the successful identification of the type of the supernova responsible for the supernova remnant SNR 0509-675 in the Large Magellanic Cloud (LMC) using Gemini spectra of surrounding light echoes. The ability to classify outbursts associated with centuries-old remnants provides a new window into several aspects of supernova research and is likely to be successful in providing new constraints on additional LMC supernovae as well as their historical counterparts in the Milky Way Galaxy (MWG). The combined spectrum of echo light from SNR 0509-675 shows broad emission and absorption lines consistent with a supernova (SN) spectrum. We create a spectral library consisting of 26 SNe Ia and 6 SN Ib/c that are time-integrated, dust-scattered by LMC dust, and reddened by the LMC and MWG. We fit these SN templates to the observed light echo spectrum using {chi}{sup 2} minimization as well as correlation techniques, and we find that overluminous 91T-like SNe Ia with {Delta}m{sub 15} < 0.9 match the observed spectrum best.
Date: February 7, 2008
Creator: Rest, A.; Matheson, T.; Blondin, S.; Bergmann, M.; Welch, D. L.; Suntzeff, N. B. et al.
Partner: UNT Libraries Government Documents Department

Echoes from Ancient supernovae in the Large Magellanic Cloud

Description: In principle, historical supernovae could still be visible as scattered-light echoes even centuries later [1, 2]. Searches for surface brightness variations using photographic plates have not recovered any echoes in the regions of historical Galactic supernovae [3]. Using differenced images, our SuperMACHO collaboration has discovered three faint new variable surface brightness complexes with high apparent proper motion pointing back to well-defined positions in the Large Magellanic Cloud (LMC). These correspond to three of the six smallest (and likely youngest) supernova remnants believed to be due to thermonuclear (Type Ia) supernovae [4]. A lower limit to the age of these remnants and echoes is 200 years given the lack of any reported LMC supernovae until 1987. The discovery of historical supernova echoes in the LMC suggests that similar echoes for Galactic supernovae such as Tycho, Kepler, Cas A, or SN1006 could be visible using standard image differencing techniques.
Date: June 15, 2005
Creator: Rest, A; Suntzeff, N B; Olsen, K; Prieto, J L; Smith, R C; Welch, D L et al.
Partner: UNT Libraries Government Documents Department

Tissue equivalent proportional counter real time neutron monitor

Description: The Tissue Equivalent Proportional Counter (TEPC) was developed to monitor low level neutron exposure rates at working stations in a nuclear fuel fabrication facility. It has proven capable of accurately measuring neutron dose rates at levels from 0.1 to 0.2 mrem/hr. It also calculates the Quality Factor which is of importance in locations where the neutron to gamma ratio may vary significantly and irregularily. The system described is computerized to monitor 100 work locations simulationeously and can be expanded to monitor 384 locations. Neutron dose is accumulated on a real time basis and after the proton drop point is established, dose rate can be read out at any time for the dose accumulated over a specified period of time. The current development program which provides reduced system maintenance, lower detection limits, and improved accuracy is discussed along with examples of measurement data and work experience with the current system.
Date: January 1, 1978
Creator: Smith, R. C.; Strode, J. N.; Brackenbush, L. W. & Faust, L. G.
Partner: UNT Libraries Government Documents Department

Optimal design of high speed analog APD receivers

Description: In order to provide optical to electrical conversion of high speed analog signals, avalanche photodiode receivers must be optimized for several parameters. Among these parameters are receiver amplifier noise, APD noise, and bandwidth. Optimization of these parameters requires a theoretical understanding of each of the parameters and their interactions. In the first part of this paper the theoretical design of an avalanche photodiode optical receiver will be discussed with attention to the parameters mentioned. Later, a comparison between calculated and measured values for a receiver design will be presented. 6 refs., 3 figs.
Date: January 1, 1988
Creator: Smith, R.C.
Partner: UNT Libraries Government Documents Department

Tissue equivalent proportional counter neutron monitor

Description: The Tissue Equivalent Proportional Counter (TEPC) is a sensitive area monitoring instrument that can be used either in place at fixed locations or as a portable neutron exposure measuring device. The system monitors low levels of neutron radiation exposure and has the capability of accurately measuring neutron exposure rates as low as 0.1 mrem/hr. The computerized analysis system calculates the quality factor which is important for situations where the neutron to gamma ratio may vary significantly and irregularly such as in fuel fabrication or handling facilities.
Date: June 1, 1980
Creator: Smith, R.C. & Strode, J.N.
Partner: UNT Libraries Government Documents Department

Multigigahertz beam diagnostics for laser fusion

Description: A system to make ultra wideband measurements of fast laser pulses and their induced target interactions at a distance of approximately 38 m from the target location is discussed. The system has demonstrated an overall bandwidth of 3 GHz with projected unfolding to 4 GHz. This system allows high resolution temporal history diagnostics in a remote location providing high EMI and radiation immunity.
Date: January 1, 1981
Creator: Smith, R.C.; Hodson, E.K. & Carlson, R.L.
Partner: UNT Libraries Government Documents Department

MELCOR computer code manuals: Primer and user`s guides, Version 1.8.3 September 1994. Volume 1

Description: MELCOR is a fully integrated, engineering-level computer code that models the progression of severe accidents in light water reactor nuclear power plants. MELCOR is being developed at Sandia National Laboratories for the US Nuclear Regulatory Commission as a second-generation plant risk assessment tool and the successor to the Source Term Code Package. A broad spectrum of severe accident phenomena in both boiling and pressurized water reactors is treated in MELCOR in a unified framework. These include: thermal-hydraulic response in the reactor coolant system, reactor cavity, containment, and confinement buildings; core heatup, degradation, and relocation; core-concrete attack; hydrogen production, transport, and combustion; fission product release and transport; and the impact of engineered safety features on thermal-hydraulic and radionuclide behavior. Current uses of MELCOR include estimation of severe accident source terms and their sensitivities and uncertainties in a variety of applications. This publication of the MELCOR computer code manuals corresponds to MELCOR 1.8.3, released to users in August, 1994. Volume 1 contains a primer that describes MELCOR`s phenomenological scope, organization (by package), and documentation. The remainder of Volume 1 contains the MELCOR Users` Guides, which provide the input instructions and guidelines for each package. Volume 2 contains the MELCOR Reference Manuals, which describe the phenomenological models that have been implemented in each package.
Date: March 1, 1995
Creator: Summers, R. M.; Cole, R. K., Jr.; Smith, R. C.; Stuart, D. S.; Thompson, S. L.; Hodge, S. A. et al.
Partner: UNT Libraries Government Documents Department