oalib

Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99

Submit

Any time

2019 ( 187 )

2018 ( 308 )

2017 ( 276 )

2016 ( 376 )

Custom range...

Search Results: 1 - 10 of 167585 matches for " E. Hungerford "
All listed articles are free for downloading (OA Articles)
Page 1 /167585
Display every page Item
A. Fluka Study of Underground Cosmogenic Neutron Production
A Empl,E. V. Hungerford,R. Jasim,P. Mosteiro
Physics , 2014, DOI: 10.1088/1475-7516/2014/08/064
Abstract: Neutrons produced by cosmic muon interactions are important contributors to backgrounds in underground detectors when searching for rare events. Typically such neutrons can dominate the background, as they are particularly difficult to shield and detect. Since actual data is sparse and not well documented, simulation studies must be used to design shields and predict background rates. Thus validation of any simulation code is necessary to assure reliable results. This work compares in detail the predictions of the FLUKA simulation code to existing data, and uses this code to report a simulation of cosmogenic backgrounds for typical detectors embedded in a water tank with liquid scintillator shielding.
Study of Cosmogenic Neutron Backgrounds at LNGS
A. Empl,R. Jasim,E. Hungerford,P. Mosteiro
Physics , 2012,
Abstract: Cosmic muon interactions are important contributors to backgrounds in underground detectors when searching for rare events. Typically neutrons dominate this background as they are particularly difficult to shield and detect in a veto system. Since actual background data is sparse and not well documented, simulation studies must be used to design shields and predict background rates. This means that validation of any simulation code is necessary to assure reliable results. This work studies the validation of the FLUKA simulation code, and reports the results of a simulation of cosmogenic background for a liquid argon two-phase detector embedded within a water tank and liquid scintillator shielding.
The Life-History of Mesovelia Mulsanti White
H. B. Hungerford
Psyche , 1917, DOI: 10.1155/1917/57095
Abstract:
Some Notonecta From South America
H. B. Hungerford
Psyche , 1926, DOI: 10.1155/1926/90626
Abstract:
Notes on the Giant Water Bugs (Lethocerus and Benucus—Belostomutidm Hemiptera)
H. B. Hungerford
Psyche , 1925, DOI: 10.1155/1925/24273
Abstract:
The CLEAR Experiment
K. Scholberg,T. Wongjirad,E. Hungerford,A. Empl,D. Markoff,P. Mueller,Y. Efremenko,D. McKinsey,J. Nikkel
Physics , 2009,
Abstract: The Spallation Neutron Source in Oak Ridge, Tennessee, is designed to produce intense pulsed neutrons for various science and engineering applications. Copious neutrinos are a free by-product. When it reaches full power, the SNS will be the world's brightest source of neutrinos in the few tens of MeV range. The proposed CLEAR (Coherent Low Energy A (Nuclear) Recoils) experiment will measure coherent elastic neutral current neutrino-nucleus scattering at the SNS. The physics reach includes tests of the Standard Model.
A FLUKA Study of $β$-delayed Neutron Emission for the Ton-size DarkSide Dark Matter Detector
Anton Empl,Ed V. Hungerford
Physics , 2014,
Abstract: In the published cosmogenic background study for a ton-sized DarkSide dark matter search, only prompt neutron backgrounds coincident with cosmogenic muons or muon induced showers were considered, although observation of the initiating particle(s) was not required. The present paper now reports an initial investigation of the magnitude of cosmogenic background from $\beta$-delayed neutron emission produced by cosmogenic activity in DarkSide. The study finds a background rate for $\beta$-delayed neutrons in the fiducial volume of the detector on the order of < 0.1 event/year. However, detailed studies are required to obtain more precise estimates. The result should be compared to a radiogenic background event rate from the PMTs inside the DarkSide liquid scintillator veto of 0.2 events/year.
The effect of 12C + 12C rate uncertainties on s-process yields
M E Bennett,R Hirschi,M Pignatari,S Diehl,C Fryer,F Herwig,A Hungerford,G Magkotsios,G Rockefeller,F Timmes,M Wiescher,P Young
Physics , 2010, DOI: 10.1088/1742-6596/202/1/012023
Abstract: The slow neutron capture process in massive stars (the weak s-process) produces most of the s-only isotopes in the mass region 60 < A < 90. The nuclear reaction rates used in simulations of this process have a profound effect on the final s-process yields. We generated 1D stellar models of a 25 solar mass star varying the 12C + 12C rate by a factor of 10 and calculated full nucleosynthesis using the post-processing code PPN. Increasing or decreasing the rate by a factor of 10 affects the convective history and nucleosynthesis, and consequently the final yields.
The effect of 12C + 12C rate uncertainties on the weak s-process component
Michael E. Bennett,Raphael Hirschi,Marco Pignatari,Steven Diehl,Chris Fryer,Falk Herwig,William Hillary,Aimee Hungerford,Debra Richman,Gabriel Rockefeller,Frank X. Timmes,Michael Wiescher
Physics , 2010,
Abstract: The contribution by massive stars (M > 9 solar masses) to the weak s-process component of the solar system abundances is primarily due to the 22Ne neutron source, which is activated near the end of helium-core burning. The residual 22Ne left over from helium-core burning is then reignited during carbon burning, initiating further s-processing that modifies the isotopic distribution. This modification is sensitive to the stellar structure and the carbon burning reaction rate. Recent work on the 12C + 12C reaction suggests that resonances located within the Gamow peak may exist, causing a strong increase in the astrophysical S-factor and consequently the reaction rate. To investigate the effect of an increased rate, 25 solar mass stellar models with three different carbon burning rates, at solar metallicity, were generated using the Geneva Stellar Evolution Code (GENEC) with nucleosynthesis post-processing calculated using the NuGrid Multi-zone Post-Processing Network code (MPPNP). The strongest rate caused carbon burning to occur in a large convective core rather than a radiative one. The presence of this large convective core leads to an overlap with the subsequent convective carbon-shell, significantly altering the initial composition of the carbon-shell. In addition, an enhanced rate causes carbon-shell burning episodes to ignite earlier in the evolution of the star, igniting the 22Ne source at lower temperatures and reducing the neutron density.
The effect of 12C + 12C rate uncertainties on the evolution and nucleosynthesis of massive stars
M. E. Bennett,R. Hirschi,M. Pignatari,S. Diehl,C. Fryer,F. Herwig,A. Hungerford,K. Nomoto,G. Rockefeller,F. X. Timmes,M. Wiescher
Physics , 2012, DOI: 10.1111/j.1365-2966.2012.20193.x
Abstract: [Shortened] The 12C + 12C fusion reaction has been the subject of considerable experimental efforts to constrain uncertainties at temperatures relevant for stellar nucleosynthesis. In order to investigate the effect of an enhanced carbon burning rate on massive star structure and nucleosynthesis, new stellar evolution models and their yields are presented exploring the impact of three different 12C + 12C reaction rates. Non-rotating stellar models were generated using the Geneva Stellar Evolution Code and were later post-processed with the NuGrid Multi-zone Post-Processing Network tool. The enhanced rate causes core carbon burning to be ignited more promptly and at lower temperature. This reduces the neutrino losses, which increases the core carbon burning lifetime. An increased carbon burning rate also increases the upper initial mass limit for which a star exhibits a convective carbon core. Carbon shell burning is also affected, with fewer convective-shell episodes and convection zones that tend to be larger in mass. Consequently, the chance of an overlap between the ashes of carbon core burning and the following carbon shell convection zones is increased, which can cause a portion of the ashes of carbon core burning to be included in the carbon shell. Therefore, during the supernova explosion, the ejecta will be enriched by s-process nuclides synthesized from the carbon core s process. The yields were used to estimate the weak s-process component in order to compare with the solar system abundance distribution. The enhanced rate models were found to produce a significant proportion of Kr, Sr, Y, Zr, Mo, Ru, Pd and Cd in the weak component, which is primarily the signature of the carbon-core s process. Consequently, it is shown that the production of isotopes in the Kr-Sr region can be used to constrain the 12C + 12C rate using the current branching ratio for a- and p-exit channels.
Page 1 /167585
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.