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Boltzmann babies in the proper time measure

Description: After commenting briefly on the role of the typicality assumption in science, we advocate a phenomenological approach to the cosmological measure problem. Like any other theory, a measure should be simple, general, well defined, and consistent with observation. This allows us to proceed by elimination. As an example, we consider the proper time cutoff on a geodesic congruence. It predicts that typical observers are quantum fluctuations in the early universe, or Boltzmann babies. We sharpen this well-known youngness problem by taking into account the expansion and open spatial geometry of pocket universes. Moreover, we relate the youngness problem directly to the probability distribution for observables, such as the temperature of the cosmic background radiation. We consider a number of modifications of the proper time measure, but find none that would make it compatible with observation.
Date: December 20, 2007
Creator: Bousso, Raphael; Bousso, Raphael; Freivogel, Ben & Yang, I-Sheng
Partner: UNT Libraries Government Documents Department

Introduction to naturally occurring radioactive material

Description: Naturally occurring radioactive material (NORM) is everywhere; we are exposed to it every day. It is found in our bodies, the food we eat, the places where we live and work, and in products we use. We are also bathed in a sea of natural radiation coming from the sun and deep space. Living systems have adapted to these levels of radiation and radioactivity. But some industrial practices involving natural resources concentrate these radionuclides to a degree that they may pose risk to humans and the environment if they are not controlled. Other activities, such as flying at high altitudes, expose us to elevated levels of NORM. This session will concentrate on diffuse sources of technologically-enhanced (TE) NORM, which are generally large-volume, low-activity waste streams produced by industries such as mineral mining, ore benefication, production of phosphate Fertilizers, water treatment and purification, and oil and gas production. The majority of radionuclides in TENORM are found in the uranium and thorium decay chains. Radium and its subsequent decay products (radon) are the principal radionuclides used in characterizing the redistribution of TENORM in the environment by human activity. We will briefly review other radionuclides occurring in nature (potassium and rubidium) that contribute primarily to background doses. TENORM is found in many waste streams; for example, scrap metal, sludges, slags, fluids, and is being discovered in industries traditionally not thought of as affected by radionuclide contamination. Not only the forms and volumes, but the levels of radioactivity in TENORM vary. Current discussions about the validity of the linear no dose threshold theory are central to the TENORM issue. TENORM is not regulated by the Atomic Energy Act or other Federal regulations. Control and regulation of TENORM is not consistent from industry to industry nor from state to state. Proposed regulations are moving from ...
Date: August 1, 1997
Creator: Egidi, P.
Partner: UNT Libraries Government Documents Department

Measured Radiation and Background Levels During Transmission of Megawatt Electron Beams Through Millimeter Apertures

Description: We report measurements of photon and neutron radiation levels observed while transmitting a 0.43 MW electron beam through millimeter-sized apertures and during beam-off, but accelerating gradient RF-on, operation. These measurements were conducted at the Free-Electron Laser (FEL) facility of the Jefferson National Accelerator Laboratory (JLab) using a 100 MeV electron beam from an energy-recovery linear accelerator. The beam was directed successively through 6 mm, 4 mm, and 2 mm diameter apertures of length 127 mm in aluminum at a maximum current of 4.3 mA (430 kW beam power). This study was conducted to characterize radiation levels for experiments that need to operate in this environment, such as the proposed DarkLight Experiment. We find that sustained transmission of a 430 kW continuous-wave (CW) beam through a 2 mm aperture is feasible with manageable beam-related backgrounds. We also find that during beam-off, RF-on operation, multipactoring inside the niobium cavities of the accelerator cryomodules is the primary source of ambient radiation when the machine is tuned for 130 MeV operation.
Date: November 1, 2013
Creator: Alarcon, Ricardo; Balascuta, S.; Benson, Stephen V.; Bertozzi, William; Boyce, James R.; Cowan, Ray et al.
Partner: UNT Libraries Government Documents Department

Evaluation of radioactive background rejection in 76Ge neutrino-lessdouble-beta decay experiments using a highly segmented HPGe detector

Description: A highly segmented coaxial HPGe detector was operated in a low background counting facility for over 1 year to experimentally evaluate possible segmentation strategies for the proposed Majorana neutrino-less double-beta decay experiment. Segmentation schemes were evaluated on their ability to reject multi-segment events while retaining single-segment events. To quantify a segmentation scheme's acceptance efficiency the percentage of peak area due to single segment events was calculated for peaks located in the energy region 911-2614 keV. Single interaction site events were represented by the double-escape peak from the 2614 keV decay in {sup 208}Tl located at 1592 keV. In spite of its prototypical nature, the detector performed well under realistic operating conditions and required only minimal human interaction. Though the energy resolution for events with interactions in multiple segments was impacted by inter-segment cross-talk, the implementation of a cross-talk correlation matrix restored acceptable resolution. Additionally, simulations utilizing the MaGe simulation package were performed and found to be in good agreement with experimental observations verifying the external nature of the background radiation.
Date: February 5, 2007
Creator: Chan, Yuen-Dat; Campbell, D.B.; Vetter, K.; Henning, R.; Lesko, K.; Chan, Y.D. et al.
Partner: UNT Libraries Government Documents Department


Description: The US Environmental Protection Agency (EPA) is installing a network of sensors in the US to monitor background radiation and elevated radiation levels expected from a possible nuclear incident. The network (RadNet) of 180 fixed sensors is intended to provide a basic estimate of the radiation level throughout the US and enhanced accuracy near population centers. This report discusses one of the objective methods for locating these monitors based on criteria outlined by the EPA. The analysis employs a representative climatology of incident scenarios that includes 50 release locations, four seasons and four times of the day. This climatology was calculated from 5,600 simulations generated with NOAA-ARL's HYSPLIT Lagrangian trajectory model. The method treats the release plumes as targets and monitors are located to maximize the number of plumes detected with the network. Weighting schemes based on detection only, dose-weighted detection and population-dose weighted detection were evaluated. The result shows that most of the monitors are located around the population centers, as expected. However, there are monitors quite uniformly distributed around the less populated areas. The monitors at the populated areas will provide early warning to protect the general public, and the monitors spread across the country will provide valuable data for modelers to estimate the extent and the transport of the radioactive contamination.
Date: October 29, 2007
Creator: Chen, K; Robert Buckley, R; Robert Kurzeja, R; Lance Osteen, L & Saleem Salaymeh, 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

Limitations on the precision of 238U/235U measurements and implications for environmental monitoring

Description: The ability to determine the isotopic composition of uranium in environmental samples is an important component of the International Atomic Energy Agency`s (IAEA) safeguards program, and variations in the isotopic ratio {sup 238}U/{sup 235}U provide the most direct evidence of isotopic enrichment activities. The interpretation of observed variations in {sup 238}U/{sup 235}U depends on the ability to distinguish enrichment from instrumental biases and any variations occurring in the environment but not related to enrichment activities. Instrumental biases that have historically limited the accuracy of {sup 238}U/{sup 235}U determinations can be eliminated by the use of the {sup 233}U/{sup 236}U double-spike technique. With this technique, it is possible to determine the {sup 238}U/{sup 235}U in samples to an accuracy equal to the precision of the measurement, ca. 0.1% for a few 10`s of nanograms of uranium. Given an accurate determination of {sup 238}U/{sup 235}U, positive identification of enrichment activities depends on the observed value being outside the range of {sup 238}U/{sup 235}U`s expected as a result of natural or environmental variations. Analyses of a suite of soil samples showed no variation beyond 0.2% in {sup 238}U/{sup 235}U.
Date: August 1, 1997
Creator: Russ III, G.P.
Partner: UNT Libraries Government Documents Department

How many dark energy parameters?

Description: For exploring the physics behind the accelerating universe a crucial question is how much we can learn about the dynamics through next generation cosmological experiments. For example, in defining the dark energy behavior through an effective equation of state, how many parameters can we realistically expect to tightly constrain? Through both general and specific examples (including new parametrizations and principal component analysis) we argue that the answer is 42 - no, wait, two. Cosmological parameter analyses involving a measure of the equation of state value at some epoch (e.g., w_0) and a measure of the change in equation of state (e.g., w') are therefore realistic in projecting dark energy parameter constraints. More elaborate parametrizations could have some uses (e.g., testing for bias or comparison with model features), but do not lead to accurately measured dark energy parameters.
Date: May 16, 2005
Creator: Linder, Eric V. & Huterer, Dragan
Partner: UNT Libraries Government Documents Department

Correlation of the highest-energy cosmic rays with the positions of nearby active galactic nuclei

Description: Data collected by the Pierre Auger Observatory provide evidence for anisotropy in the arrival directions of the cosmic rays with the highest energies, which are correlated with the positions of relatively nearby active galactic nuclei (AGN) [1]. The correlation has maximum significance for cosmic rays with energy greater than {approx} 6 x 10{sup 19} eV and AGN at a distance less than {approx} 75 Mpc. We have confirmed the anisotropy at a confidence level of more than 99% through a test with parameters specified a priori, using an independent data set. The observed correlation is compatible with the hypothesis that cosmic rays with the highest energies originate from extra-galactic sources close enough so that their flux is not significantly attenuated by interaction with the cosmic background radiation (the Greisen-Zatsepin-Kuzmin effect). The angular scale of the correlation observed is a few degrees, which suggests a predominantly light composition unless the magnetic fields are very weak outside the thin disk of our galaxy. Our present data do not identify AGN as the sources of cosmic rays unambiguously, and other candidate sources which are distributed as nearby AGN are not ruled out. We discuss the prospect of unequivocal identification of individual sources of the highest-energy cosmic rays within a few years of continued operation of the Pierre Auger Observatory.
Date: December 1, 2007
Creator: Collaboration, The Pierre auger
Partner: UNT Libraries Government Documents Department

Wavelet Denoising of Mobile Radiation Data

Description: The investigation of wavelet analysis techniques as a means of filtering the gross-count signal obtained from radiation detectors has shown promise. These signals are contaminated with high frequency statistical noise and significantly varying background radiation levels. Wavelet transforms allow a signal to be split into its constituent frequency components without losing relative timing information. Initial simulations and an injection study have been performed. Additionally, acquisition and analysis software has been written which allowed the technique to be evaluated in real-time under more realistic operating conditions. The technique performed well when compared to more traditional triggering techniques with its performance primarily limited by false alarms due to prominent features in the signal. An initial investigation into the potential rejection and classification of these false alarms has also shown promise.
Date: October 29, 2007
Creator: Campbell, D & Lanier, R
Partner: UNT Libraries Government Documents Department

Low-Frequency Measurments of the Cosmic Background RadiationSpectrum

Description: The long-wavelength spectrum of the cosmic background radiation has been measured at five wavelengths (0.33, 0.9, 3.0, 6.3, and 12.0 cm). These measurements represent a continuation of the work reported by Smoot et al. (1983). The combine results have a weighted average of 2.73 {+-} 0.05 K and are consistent with past measurements. They limit the possible Compton distortion of the Cosmic Background Radiation spectrum to less than 8%.
Date: November 1, 1984
Creator: Smoot, G.F.; De Amici, G.; Friedman, S.D.; Witebsky, C.; Sironi,G.; Bonelli, G. et al.
Partner: UNT Libraries Government Documents Department

A Measurement of the Cosmic Background Radiation Temperature at3.0 cm

Description: We describe a measurement of the cosmic background radiation temperature at a wavelength of 3.0 cm. The experiment was made in conjunction with measurements at four other wavelengths in an effort to measure the long wavelength spectrum to high accuracy. The result at 3 cm, T{sub CBR} = 2.91 {+-} 0.19 K, is in good agreement with the values at neighboring wavelengths, and consistent with previous results.
Date: June 1, 1983
Creator: Friedman, S.D.; Smoot, G.F.; De Amici, G. & Witebsky, C.
Partner: UNT Libraries Government Documents Department

Measurement of the Intensity of the Cosmic Background Radiation at3.7 GHz

Description: We measured the temperature of the cosmic background radiation (CBR) at a frequency of 3.7 GHz (8.1 cm wavelength), using a total power, direct RF-gain receiver. The results give a brightness temperature, T{sub CBR}, of 2.58 {+-} 0.13 K (68% C.L.). Details of the instrument and of the experimental procedure are given. This measurement is part of a larger experiment to measure the spectrum of the Cosmic Background Radiation between 0.6 and 90 GHz (50 and 0.33 cm wavelength).
Date: April 1, 1987
Creator: De Amici, G.; Smoot, G.F.; Aymon, J.; Bersanelli, M.; Kogut, A.; Levine, S.M. et al.
Partner: UNT Libraries Government Documents Department

Measurements of the Cosmic Background Radiation Temperature at 3.3and 9.1 MM

Description: The authors report the results of measurements of the cosmic background radiation temperature at wavelengths of 9.1 and 3.3 mm. The 9.1 mm result, T{sub CBR} = 2.87 {+-} 0.21 K, is in good agreement with previous results and those obtained at longer wavelengths during the same experiment. The 3.3 mm result, T{sub CBR} = 2.4 {+-} 1.0 K, is consistent with previous measurements, but has a large error due to uncertainty in the atmospheric correction.
Date: June 1, 1983
Creator: Witebsky, C.; De Amici, G.; Smoot, G.F. & Friedman, S.D.
Partner: UNT Libraries Government Documents Department

The Spectrumof the Cosmic Background Radiation: Early and RecentMeasurements from the White Mountain Research Station

Description: The White Mountain Research Station has provided a support facility at a high, dry, radio-quiet site for measurements that have established the blackbody character of the cosmic microwave background radiation. This finding has confirmed the interpretation of the radiation as a relic of the primeval fireball and helped to establish the hot Big Bang theory as the standard cosmological model.
Date: September 1, 1985
Creator: Smoot, G. F.
Partner: UNT Libraries Government Documents Department

3 mm Anisotropy Measurement: On the Quadrupole Component in theCosmic Background Radiation

Description: We have mapped the large-scale anisotropy in the cosmic background radiation at 3 mm wavelength using a liquid-helium-cooled balloon-borne radiometer sensitive enough to detect the dipole in one gondola rotation (1 minute). Statistical errors on the dipole and quadrupole components are below 0.1 mK with less than 0.1 m K galactic contribution. We find a dipole consistent with previous measurements but disagree with recent quadrupole reports. The measurement is also useful in searching for spectral distortions.
Date: November 1, 1982
Creator: Lubin, Philip M.; Epstein, Gerald L. & Smoot, George F.
Partner: UNT Libraries Government Documents Department

Correlation of the highest energy cosmic rays with nearby extragalactic objects

Description: Using data collected at the Pierre Auger Observatory during the past 3.7 years, we demonstrate that there is a correlation between the arrival directions of cosmic rays with energy above {approx} 6 x 10{sup 19} eV and the positions of active galactic nuclei (AGN) lying within {approx} 75 Mpc. We reject the hypothesis of an isotropic distribution of these cosmic rays at over 99% confidence level from a prescribed a priori test. The correlation we observe is compatible with the hypothesis that the highest energy particles originate from nearby extragalactic sources whose flux has not been significantly reduced by interaction with the cosmic background radiation. AGN or objects having a similar spatial distribution are possible sources.
Date: November 1, 2007
Creator: Abraham, J.; Abreu, P.; Aglietta, M.; Aguirre, C.; Allard, D.; Allekotte, I. et al.
Partner: UNT Libraries Government Documents Department

New Measurements of the Cosmic Background Radiation Spectrum

Description: We have continued our program to measure the long-wavelength spectrum of the cosmic background radiation. Our previous observations were at five wavelengths--0.33, 0.9, 3.0, 6.3, and 12.0 cm--and had a weighted average value of 2.73 {+-} 0.05 K and deviated from a Planckian spectrum by less than 6%. In August 1984, we repeated our observations at 3.0, 0.9, and 0.33 cm and made new observations with a radiometer tunable from 1.7 to 15 cm. Preliminary analysis indicate that the new data are consistent with our previous results.
Date: December 1, 1984
Creator: Smoot, G.F.; De Amici, G.; Levin, S. & Witebsky, C.
Partner: UNT Libraries Government Documents Department

New Measurements of the Cosmic Background Radiation Temperature at3.3 mm Wavelength

Description: We have measured the temperature of the cosmic background radiation (CBR) at 3.3 mm wavelength in 1982, 1983, and 1984 as part of a larger project to determine the CBR temperature at five wavelengths from 12 cm to 3.3 mm (Smoot et al. 1985). The 3.3-mm measurements yield a brightness temperature of 2.57 K with a 1{sigma} uncertainty of 20.12 K. This paper describes the instrument, the measurement techniques, and the data-analysis procedures used. Our result is in good agreement with recent measurements at comparable wavelengths by Meyer and Jura (1985) and by Peterson, Richards, and Timusk (1985), but it disagrees with the temperatures reported by Woody and Richards (1981).
Date: February 1, 1986
Creator: Witebsky, C.; Smoot, G.; De Amici, G. & Friedman, S.D.
Partner: UNT Libraries Government Documents Department

The Temperature of the Cosmic Background Radiation: Results fromthe 1987 and 1988 Measurements at 3.8 GHz

Description: We have measured the temperature of the cosmic background radiation (CBR) at a frequency of 3.8 GHz (7.9 cm wavelength), during two consecutive summers, obtaining a brightness temperature, T{sub CBR}, of 2.56 {+-} 0.08 K in 1987 and 2.71 {+-} 0.07 K in 1988 (68% confidence level). The new results are in agreement with our previous measurement at 3.7 GHz obtained in 1986, and have smaller error bars. Combining measurements from all three years we obtain T{sub CBR} = 2.64 {+-} 0.07 K.
Date: November 10, 1989
Creator: De Amici, Giovanni; Bensadoun, M.; Bersanelli, M.; Kogut, A.; Levine, S.; Smoot, George F. et al.
Partner: UNT Libraries Government Documents Department

Review of Cosmic Background Radiation Spectrum Measurements:Limits on Distortions, Energy Release, and Cosmological Processes

Description: This paper reviews the three major cosmic microwave background radiation (CMBR) spectrum measurement programs conducted and published since the last (XVII) IAU General Assembly. The results are consistent with a Planckian spectrum with temperature 2.72 {+-} 0.03 K spanning a wavelength range of 0.1 to 12 cm. Limits on possible distortions and implications are outlined. Ongoing and future measurements are discussed.
Date: January 1, 1986
Creator: Smoot, G.F.
Partner: UNT Libraries Government Documents Department