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Semi-Empirical Method of Calculating the Energy-Absorption Build-up Factor with an Application to a Uniformly Contaminated Space Having Spherical Boundaries

Description: From Abstract: "The results are compared with those obtained by other methods, and an application to the problem of uniformly and continuously distributed point-source is discussed."
Date: October 14, 1957
Creator: O'Brien, Keran; Lowder, Wayne M. & Solon, Leonard R.
Partner: UNT Libraries Government Documents Department

Impact of Discharges from Point and Nonpoint Sources on Water Quality of the Upper Reedy River Near Greenville, South Carolina

Description: From objective and scope: The objective of the study was to determine if discharges from nonpont sources in the urban Greenville area result in concentrations of dissolved oxgen less than 5 mg/L in the Reedy River downstream from Greenville.
Date: 1983
Creator: Cahal, Donald I. & Speiran, Gary K.
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

FIRST NEUTRINO POINT-SOURCE RESULTS FROM THE 22-STRING ICECUBE DETECTOR

Description: We present new results of searches for neutrino point sources in the northern sky, using data recorded in 2007-08 with 22 strings of the IceCube detector (approximately one-fourth of the planned total) and 275.7 days of livetime. The final sample of 5114 neutrino candidate events agrees well with the expected background of atmospheric muon neutrinos and a small component of atmospheric muons. No evidence of a point source is found, with the most significant excess of events in the sky at 2.2 {sigma} after accounting for all trials. The average upper limit over the northern sky for point sources of muon-neutrinos with E{sup -2} spectrum is E{sup 2} {Phi}{sub {nu}{sub {mu}}} < 1.4 x 10{sup -1} TeV cm{sup -2}s{sup -1}, in the energy range from 3 TeV to 3 PeV, improving the previous best average upper limit by the AMANDA-II detector by a factor of two.
Date: May 14, 2009
Creator: Collaboration, IceCube & Klein, Spencer
Partner: UNT Libraries Government Documents Department

Search for Point Sources of High Energy Neutrinos with Final Data from AMANDA-II

Description: We present a search for point sources of high energy neutrinos using 3.8 years of data recorded by AMANDA-II during 2000-2006. After reconstructing muon tracks and applying selection criteria designed to optimally retain neutrino-induced events originating in the Northern Sky, we arrive at a sample of 6595 candidate events, predominantly from atmospheric neutrinos with primary energy 100 GeV to 8 TeV. Our search of this sample reveals no indications of a neutrino point source. We place the most stringent limits to date on E{sup -2} neutrino fluxes from points in the Northern Sky, with an average upper limit of E{sup 2}{Phi}{sub {nu}{sub {mu}}+{nu}{sub {tau}}} {le} 5.2 x 10{sup -11} TeV cm{sup -2} s{sup -1} on the sum of {nu}{sub {mu}} and {nu}{sub {tau}} fluxes, assumed equal, over the energy range from 1.9 TeV to 2.5 PeV.
Date: March 6, 2009
Creator: Collaboration, IceCube & Klein, Spencer
Partner: UNT Libraries Government Documents Department

Extending the search for neutrino point sources with IceCube above the horizon

Description: Point source searches with the IceCube neutrino telescope have been restricted to one hemisphere, due to the exclusive selection of upward going events as a way of rejecting the atmospheric muon background. We show that the region above the horizon can be included by suppressing the background through energy-sensitive cuts. This approach improves the sensitivity above PeV energies, previously not accessible for declinations of more than a few degrees below the horizon due to the absorption of neutrinos in Earth. We present results based on data collected with 22 strings of IceCube, extending its field of view and energy reach for point source searches. No significant excess above the atmospheric background is observed in a sky scan and in tests of source candidates. Upper limits are reported, which for the first time cover point sources in the southern sky up to EeV energies.
Date: November 20, 2009
Creator: Collaboration, IceCube
Partner: UNT Libraries Government Documents Department

An Analytical Model for Solute Transport in Unsaturated Flowthrough a Single Fracture and Porous Rock Matrix

Description: Exact analytical solutions are presented for solute transport in an unsaturated fracture and porous rock matrix. The problem includes advective transport in the fracture and rock matrix as well as advective and diffusive fracture-matrix exchange. Linear sorption in the fracture and matrix and radioactive decay are also treated. The solution is for steady, uniform transport velocities within the fracture and matrix, but allows for independent specification of each of the velocities. The problem is first solved in terms of the solute concentrations that result from an instantaneous point source. Superposition integrals are then used to derive the solute mass flux at a fixed downstream position from an instantaneous point source and for the solute concentrations that result from a continuous point source. Solutions are derived for cases with the solute source in the fracture and the solute source in the matrix. The analytical solutions are closed-form and are expressed in terms of algebraic functions, exponentials, and error functions. Comparisons between the analytical solutions and numerical simulations, as well as sensitivity studies, are presented. Increased sensitivity to cross-flow and solute source location is found for increasing Peclet number. The numerical solutions are found to compare well with the analytical solutions at lower Peclet numbers ,but show greater deviation at higher Peclet numbers.
Date: September 16, 2004
Creator: Houseworth, J.E.
Partner: UNT Libraries Government Documents Department

The Search for Muon Neutrinos from Northern HemisphereGamma-Ray Bursts with AMANDA

Description: We present the results of the analysis of neutrino observations by the Antarctic Muon and Neutrino Detector Array (AMANDA) correlated with photon observations of more than 400 gamma-ray bursts (GRBs) in the Northern Hemisphere from 1997 to 2003. During this time period, AMANDA's effective collection area for muon neutrinos was larger than that of any other existing detector. Based on our observations of zero neutrinos during and immediately prior to the GRBs in the dataset, we set the most stringent upper limit on muon neutrino emission correlated with gamma-ray bursts. Assuming a Waxman-Bahcall spectrum and incorporating all systematic uncertainties, our flux upper limit has a normalization at 1 PeV of E{sup 2}{Phi}{sub {nu}} {le} 6.0 x 10{sup -9} GeV cm{sup -2}s{sup -1}sr{sup -1}, with 90% of the events expected within the energy range of {approx}10 TeV to {approx}3 PeV. The impact of this limit on several theoretical models of GRBs is discussed, as well as the future potential for detection of GRBs by next generation neutrino telescopes. Finally, we briefly describe several modifications to this analysis in order to apply it to other types of transient point sources.
Date: May 8, 2007
Creator: Collaboration, IceCube; Klein, Spencer & Achterberg, A.
Partner: UNT Libraries Government Documents Department

LONG-TERM CHANGES IN MERCURY CONCENTRATIONS IN FISH FROM THE MIDDLE SAVANNAH RIVER

Description: Total mercury levels were measured in largemouth bass (Micropterus salmoides), ''sunfishes'' (Lepomis spp)., and ''catfish'' (primarily Ameiurus spp.) from 1971 to 2004 in the middle reaches of the Savannah River, which drains the coastal plain of the southeastern U.S. Mercury levels were highest in 1971 but declined over the next ten years due to the mitigation of point sources of industrial pollution. Mercury levels began to increase in the 1980s as a possible consequence of mercury inputs from tributaries and associated wetlands where mercury concentrations were significantly elevated in water and fish. Mercury levels in Savannah River fish decreased sharply in 2001-2003 coincident with a severe drought in the Savannah River basin, but returned to previous levels in 2004 with the resumption of normal precipitation. Regression models showed that mercury levels in Savannah River fish changed significantly over time and were affected by river discharge. Despite temporal changes, there was little overall difference in Savannah River fish tissue mercury levels between 1971 and 2004.
Date: January 2, 2007
Creator: Paller, M & Bill Littrell, B
Partner: UNT Libraries Government Documents Department

RESISTIVITY MODELING FOR ARBITRARILY SHAPED THREE-DIMENSIONAL STRUCTURES

Description: A numerical technique has been developed to solve the three-dimensional potential distribution about a point source of current located in or on the surface of a half-space containing an arbitrary three-dimensional conductivity distribution. Self-adjoint difference equations are obtained for Poisson's equation using finite-difference approximations in conjunction with an elemental volume discretization of the lower half-space. Potential distribution at all points in the set defining the subsurface are simultaneously solved for multiple point sources of current. Accurate and stable solutions are obtained using full, banded, Cholesky decomposition of the capacitance matrix as well as the recently developed Incomplete Cholesky-Conjugate Gradient Iterative method. A comparison of the two- and three-dimensional simple block-shaped models, for the collinear dipole-dipole array, indicates substantially lower anomaly indices for inhomogeneities of finite strike-extent. In general, the strike-extents of inhomogeneities have to be approximately 10 times the dipole lengths before the response becomes two-dimensional. The saturation effect with increasing conductivity contrasts appears sooner for the three-dimensional conductive inhomogeneities than for corresponding models with infinite strike lengths. A downhole-to-surface configuration of electrodes produces diagnostic total field apparent resistivity maps for three-dimensional buried inhomogeneities. Experiments with various lateral and depth locations of the current pole indicate that mise a la masse surveys give the largest anomaly if a current pole is located asymmetrically and preferably near the top-surface of the buried conductor.
Date: October 1, 1977
Creator: Dey, Abhijit & Morrison, H. Frank
Partner: UNT Libraries Government Documents Department

Color and Variability Characteristics of Point Sources in the Faint Sky Variability Survey

Description: The authors present an analysis of the color and variability characteristics for point sources in the Faint Sky Variability Survey (FSVS). The FSVS cataloged {approx} 23 square degrees in BVI filters from {approx} 16-24 mag to investigate variability in faint sources at moderate to high Galactic latitudes. Point source completeness is found to be >83% for a selected representative sample (V - 17.5-22.0 mag, B-V = 0.0-1.5) containing both photometric B, V detections and 80% of the time-sampled V data available compared to a basic internal source completeness of 99%. Multi-epoch (10-30) observations in V spanning minutes to years modeled by light curve simulations reveal amplitude sensitivities to {approx} 0.015-0.075 mag over a representative V = 18-22 mag range. Periodicity determinations appear viable to time-scales of an order 1 day or less using the most sampled fields ({approx} 30 epochs). The fraction of point sources is found to be generally variable at 5-8% over V = 17.5-22.0 mag. For V brighter than 19 mag, the variable population is dominated by low amplitude (< 0.05 mag) and blue (B-V < 0.35) sources, possibly representing a population of {gamma} Doradus stars. Overall, the dominant population of variable sources are bluer than B-V = 0.65 and have Main Sequence colors, likely reflecting larger populations of RR Lyrae, SX Phe, {gamma} Doradus, and W UMa variables.
Date: March 7, 2005
Creator: Huber, M E; Everett, M E & Howell, S B
Partner: UNT Libraries Government Documents Department

The Gemini Deep Planet Survey - GDPS

Description: We present the results of the Gemini Deep Planet Survey, a near-infrared adaptive optics search for giant planets and brown dwarfs around nearby young stars. The observations were obtained with the Altair adaptive optics system at the Gemini North telescope and angular differential imaging was used to suppress the speckle noise of the central star. Detection limits for the 85 stars observed are presented, along with a list of all faint point sources detected around them. Typically, the observations are sensitive to angular separations beyond 0.5-inch with 5{sigma} contrast sensitivities in magnitude difference at 1.6 {micro}m of 9.6 at 0.5-inch, 12.9 at 1-inch, 15 at 2-inch, and 16.6 at 5-inch. For the typical target of the survey, a 100 Myr old K0 star located 22 pc from the Sun, the observations are sensitive enough to detect planets more massive than 2 M{sub Jup} with a projected separation in the range 40-200 AU. Depending on the age, spectral type, and distance of the target stars, the minimum mass that could be detected with our observations can be {approx}1 M{sub Jup}. Second epoch observations of 48 stars with candidates (out of 54) have confirmed that all candidates are unrelated background stars. A detailed statistical analysis of the survey results, which provide upper limits on the fractions of stars with giant planet or low mass brown dwarf companions, is presented. Assuming a planet mass distribution dn/dm {proportional_to} m{sup -1.2} and a semi-major axis distribution dn/da {proportional_to} a{sup -1}, the upper limits on the fraction of stars with at least one planet of mass 0.5-13 M{sub Jup} are 0.29 for the range 10-25 AU, 0.13 for 25-50 AU, and 0.09 for 50-250 AU, with a 95% confidence level; this result is weakly dependent on the semi-major axis distribution power-law index. Without making any assumption ...
Date: June 1, 2007
Creator: Lafreniere, D; Doyon, R; Marois, C; Nadeau, D; Oppenheimer, B R; Roche, P F et al.
Partner: UNT Libraries Government Documents Department

Simulated Performance of a Second-Generation Compact Compton Imaging Detector

Description: Simulations are performed using GEANT4 of a second-generation compact Compton imaging detector called CCI2 which uses silicon and germanium detector crystals. Realistic simulated detector geometry and realistic detector parameters are used. Results are obtained for the CCI2 detector for the intrinsic photopeak efficiency, imaging efficiency, and angular resolution, and simulated images are created for point sources with various energies and source angles.
Date: January 16, 2007
Creator: Manini, H A
Partner: UNT Libraries Government Documents Department

Report on the performance of a large-area, gamma-ray imager for search

Description: We are currently constructing a prototype, large-area, gamma-ray detector for conducting vehicle-mounted, mobile-search operations. The system is unique in that it relies on imaging to discriminate point sources of interest from the natural background variations. In a non-imaging instrument the background fluctuations mimic the signature seen from real sources at a distance and one is limited in sensitivity to detecting only those sources that overwhelm the local background variations --not just the counting statistics associated with a given measurement. The net result is that a larger detector is generally not more sensitive to detecting sources in the world at large. [1, 2] In a previous publication [3] we reported on the detection of a 1-mCi source at more than 80 meters from the detector using a proof-of-principle instrument (see Fig. 1) constructed to demonstrate how imaging removes the size limit on search instruments. In this report we document a systematic effort using the same detector to demonstrate that imaging detectors can reliably detect weak radiation sources at many 10's of meters. Specifically, we collected data on a 1-mCi {sup 137}Cs source 65 m from the path of the search instrument.
Date: October 7, 2005
Creator: Fabris, L & Ziock, K
Partner: UNT Libraries Government Documents Department

Devloping High Energy Radiography for HED Experiments on NIF and Omega-EP

Description: High energy radiography capabilities are essential for many future DNT/HED experiments on NIF. We have been developing bright, high-energy (15-100 keV), high resolution (< 20 {micro}m), 1-D and 2-D radiography solutions for DNT experiments on NIF. In this LDRD, we have made significant progress utilizing high-energy, high-intensity, short-pulse lasers to generate hard K-{alpha} photons. High energy K-{alpha} sources are created by hot electrons interacting in the target fluor material after irradiation by lasers with intensity I{sub L} > 10{sup 17} W/cm{sup 2}. High resolution point projection 1-D and 2-D radiography have been achieved using {mu}-foil and {mu}-wire targets attached to low-Z substrate materials. The {mu}-wire size was 10 x 10 x 300 {micro}m on a 300 x 300 x 5 {micro}m CH substrate creating the point source size equivalent to these micro targets. This unique technique will utilize the NIF short pulse laser (ARC) as a backlighter suitable for the full range of DNT science experiments on NIF.
Date: February 14, 2008
Creator: Maddox, B; Tommasini, R; Remington, B; Key, M & Town, R
Partner: UNT Libraries Government Documents Department

VLT AND ACS OBSERVATIONS OF RDCS J1252.9-2927: DYNAMICAL STRUCTURE AND GALAXY POPULATIONS IN A MASSIVE CLUSTER AT Z=1.237*

Description: We present results from an extensive spectroscopic survey, carried out with FORS on the ESO Very Large Telescope, and from an extensive multi-wavelength imaging data set from the Advanced Camera for Surveys and ground based facilities of the cluster of galaxies RDCS J1252.9-2927. We have spectroscopically confirmed 38 cluster members in the redshift range 1.22 < z < 1.25. The distribution in velocity of these spectroscopic members yields a cluster median redshift of z = 1.237 and a rest-frame velocity dispersion of 747{sub -84}{sup +74} km s{sup -1}. Star-forming members are observed to mainly populate the outskirts of the cluster while passive galaxies dominate the central cluster region. Using the 38 confirmed redshifts, we were able to resolve, for the first time at z > 1, kinematic structure. The velocity distribution, which is not Gaussian at the 95% confidence level, is consistent with two groups that are also responsible for the projected elongation of the cluster in the East-West direction. The groups are composed of 26 and 12 galaxies and have velocity dispersions of 486{sub -85}{sup +47} km s{sup -1} and 426{sub -105}{sup +57} km s{sup -1}, respectively. The elongation is also seen in the intracluster gas (from X-ray observations) and the dark matter distribution (from a weak lensing analysis). This leads us to conclude that RDCS J1252.9-2927 has not yet reached a final virial state. We extend the analysis of the color-magnitude diagram of spectroscopic members to more than 1 Mpc from the cluster center. The scatter and slope of non-[OII]-emitting cluster members in the near-IR red sequence is similar to that seen in clusters at lower redshift. Furthermore, none of the galaxies with luminosities greater than {approx} K*{sub s} + 1.5 show any [OII] emission feature, indicating that these more luminous, redder galaxies have stopped forming stars earlier ...
Date: March 23, 2007
Creator: Demarco, R; Rosati, P; Lidman, C; Girardi, M; Nonino, M; Rettura, A et al.
Partner: UNT Libraries Government Documents Department

A THEOREM AND ITS APPLICATION TO FINITE TAMPERS

Description: A theorem is derived which is useful in the analysis of neutron problems in which all neutrons have the same velocity. It is applied to determine extrapolated end-points, the asymptotic amplitude from a point source, and the neutron density at the surface of a medium. Formulas for the effect of finite tampers are derived by its aid, and their accuracy is discussed.
Date: August 15, 1946
Creator: Feynman, R.P.
Partner: UNT Libraries Government Documents Department

Field evidence for strong chemical separation of contaminants in the Hanford Vadose Zone

Description: Water and chemical transport from a point source withinvadose zone sediments at Hanford were examined with a leak testconsisting of five 3800-liter aliquots of water released at 4.5 m depthevery week over a 4-week period. The third aliquot contained bromide, D2Oand 87Sr. Movement of the tracers was monitored for 9 months by measuringpore water compositions of samples from boreholes drilled 2-8 m from theinjection point. Graded sedimentary layers acting as natural capillarybarriers caused significant lateral spreading of the leak water. D2Oconcentrations>50 percent of the concentration in the tracer aliquotwere detected at 9-11 m depth. However, increased water contents, lowerd18O values, and geophysical monitoring of moisture changes at otherdepths signified high concentrations of leak fluids were added where D2Oconcentrations were<3 percent above background, suggesting limitedmixing between different aliquots of the leak fluids. Initially highbromide concentrations decreased more rapidly over time than D2O,suggesting enhanced transport of bromide due to anion exclusion. Nosignificant increase in 87Sr was detected in the sampled pore water,indicating strong retardation of Sr by the sediments. These resultshighlight some of the processes strongly affecting chemical transport inthe vadose zone and demonstrate the significant separation of contaminantplumes that can occur.
Date: April 10, 2007
Creator: Conrad, Mark E.; DePaolo, Donald J.; Maher, Katharine; Gee,Glendon W. & Ward, Anderson L.
Partner: UNT Libraries Government Documents Department

A practical comparison of phase diversity to interferometry in measuring the aberrations in an adaptive optics system

Description: Any adaptive optics system must be calibrated with respect to internal aberrations in order for it to properly correct the starlight before it enters the science camera. Typical internal calibration consists of using a point source stimulus at the input to the AO system and recording the wavefront at the output. Two methods for such calibration have been implemented on the adaptive optics system at Lick Observatory. The first technique, Phase Diversity, consists of taking out of focus images with the science camera and using an iterative algorithm to estimate the system wavefront. A second technique uses a newly installed instrument, the Phase-Shifting Diffraction Interferometer, which has the promise of providing very high accuracy wavefront measurements. During observing campaigns in 1998, both of these methods were used for initial calibrations. In this paper we present results and compare the two methods in regard to accuracy and their practical aspects.
Date: July 1, 1999
Creator: Bauman, B; Campbell, G; Carrano, C; Gavel, D T & Olivier, S
Partner: UNT Libraries Government Documents Department

Improved Background Corrections for Uranium Holdup Measurements

Description: In the original Generalized Geometry Holdup (GGH) model, all holdup deposits were modeled as points, lines, and areas[1, 5]. Two improvements[4] were recently made to the GGH model and are currently in use at the Y-12 National Security Complex. These two improvements are the finite-source correction CF{sub g} and the self-attenuation correction. The finite-source correction corrects the average detector response for the width of point and line geometries which in effect, converts points and lines into areas. The result of a holdup measurement of an area deposit is a density-thickness which is converted to mass by multiplying it by the area of the deposit. From the measured density-thickness, the true density-thickness can be calculated by correcting for the material self-attenuation. Therefore the self-attenuation correction is applied to finite point and line deposits as well as areas. This report demonstrates that the finite-source and self-attenuation corrections also provide a means to better separate the gamma rays emitted by the material from the gamma rays emitted by background sources for an improved background correction. Currently, the measured background radiation is attenuated for equipment walls in the case of area deposits but not for line and point sources. The measured background radiation is not corrected for attenuation by the uranium material. For all of these cases, the background is overestimated which causes a negative bias in the measurement. The finite-source correction and the self-attenuation correction will allow the correction of the measured background radiation for both the equipment attenuation and material attenuation for area sources as well as point and line sources.
Date: June 21, 2004
Creator: Oberer, R. B.; Gunn, C. A. & Chiang, L. G.
Partner: UNT Libraries Government Documents Department

WEST COAST REGIONAL CARBON SEQUESTRATION PARTNERSHIP

Description: The West Coast Regional Carbon Sequestration Partnership is one of seven partnerships which have been established by the US Department of Energy (DOE) to evaluate carbon dioxide capture, transport and sequestration (CT&amp;S) technologies best suited for different regions of the country. The West Coast Region comprises Arizona, California, Nevada, Oregon, Washington, and the North Slope of Alaska. Led by the California Energy Commission, the West Coast Partnership is a consortium of over thirty five organizations, including state natural resource and environmental protection agencies; national labs and universities; private companies working on CO{sub 2} capture, transportation, and storage technologies; utilities; oil and gas companies; nonprofit organizations; and policy/governance coordinating organizations. In an eighteen month Phase I project, the Partnership will evaluate both terrestrial and geologic sequestration options. Work will focus on five major objectives: (1) Collect data to characterize major CO{sub 2} point sources, the transportation options, and the terrestrial and geologic sinks in the region, and compile and organize this data via a geographic information system (GIS) database; (2) Address key issues affecting deployment of CT&amp;S technologies, including storage site permitting and monitoring, injection regulations, and health and environmental risks (3) Conduct public outreach and maintain an open dialogue with stakeholders in CT&amp;S technologies through public meetings, joint research, and education work (4) Integrate and analyze data and information from the above tasks in order to develop supply curves and cost effective, environmentally acceptable sequestration options, both near- and long-term (5) Identify appropriate terrestrial and geologic demonstration projects consistent with the options defined above, and create action plans for their safe and effective implementation A kickoff meeting for the West Coast Partnership was held on Sept 30-Oct.1. Contracts were then put into place with twelve organizations which will carry out the technical work required to meet Partnership objectives.
Date: January 1, 2004
Creator: Myer, Larry; Surles, Terry & Birkinshaw, Kelly
Partner: UNT Libraries Government Documents Department

The IceCube Collaboration:contributions to the 30 th International Cosmic Ray Conference (ICRC 2007),

Description: This paper bundles 40 contributions by the IceCube collaboration that were submitted to the 30th International Cosmic Ray Conference ICRC 2007. The articles cover studies on cosmic rays and atmospheric neutrinos, searches for non-localized, extraterrestrial {nu}{sub e}, {nu}{sub {mu}} and {nu}{sub {tau}} signals, scans for steady and intermittent neutrino point sources, searches for dark matter candidates, magnetic monopoles and other exotic particles, improvements in analysis techniques, as well as future detector extensions. The IceCube observatory will be finalized in 2011 to form a cubic-kilometer ice-Cherenkov detector at the location of the geographic South Pole. At the present state of construction, IceCube consists of 52 paired IceTop surface tanks and 22 IceCube strings with a total of 1426 Digital Optical Modules deployed at depths up to 2350 m. The observatory also integrates the 19 string AMANDA subdetector, that was completed in 2000 and extends IceCube's reach to lower energies. Before the deployment of IceTop, cosmic air showers were registered with the 30 station SPASE-2 surface array. IceCube's low noise Digital Optical Modules are very reliable, show a uniform response and record waveforms of arriving photons that are resolvable with nanosecond precision over a large dynamic range. Data acquisition, reconstruction and simulation software are running in production mode and the analyses, profiting from the improved data quality and increased overall sensitivity, are well under way.
Date: November 2, 2007
Creator: Collaboration, IceCube & Ackermann, M.
Partner: UNT Libraries Government Documents Department

High Energy K(alpha) Radiography Using High-intensity, Short-pulse Lasers

Description: We have performed experiments using Callisto, the Vulcan 100 TW and the Vulcan Petawatt high intensity lasers to understand the characteristics of high energy, K{alpha} x-ray sources and to implement workable radiography solutions at 20-100 keV. Our measurements show that the K{alpha} size from a simple foil target is larger than 60 {micro}m, far larger than the experiment resolution requirement. The total K{alpha} yield is independent of target thicknesses verifying that refluxing plays a major role in photon generation. Smaller radiating volumes emit brighter K{alpha} radiation. 1-D radiography experiments using small-edge-on foils resolved 10 {micro}m features with high contrast. We tested a variety of small volume 2-D point sources such as cones, wires, and embedded wires, measuring photon yields and comparing our measurements with predictions from hybrid-PIC LSP simulations. In addition to high-energy, high-resolution backlighters, future experiments will also need imaging detectors and diagnostic tools that are workable in the 20-100 keV energy range. An initial look at some of these detector issues is also presented.
Date: November 16, 2005
Creator: Park, H; Izumi, N; Key, M H; King, J A; Koch, J A; Landen, O L et al.
Partner: UNT Libraries Government Documents Department