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Polyethylene as a Radiation Shielding Standard in Simulated Cosmic-Ray Environments

Description: Radiation risk management for human space missions dependson accurate modeling of high-energy heavy ion transport in matter. Theprocess of nuclear fragmentation can play a key role in reducing both thephysical dose and the biological effectiveness of the radiationencountered in deep space. Hydrogenous materials and light elements areexpected to be more effective shields against the deleterious effects ofGalactic Cosmic Rays (GCR) than aluminum, which is used in currentspacecraft hulls. NASA has chosen polyethylene, CH2, as the referencematerial for accelerator-based radiation testing of multi-functioncomposites that are currently being developed. A detailed discussion ofthe shielding properties of polyethylene under a variety of relevantexperimental conditions is presented, along with Monte Carlo simulationsof the experiments and other Monte Carlo calculations in which the entireGCR flux is simulated. The Monte Carlo results are compared to theaccelerator data and we assess the usefulness of 1 GeV/amu 56Fe as aproxy for GCR heavy ions. We conclude that additional accelerator-basedmeasurements with higher beam energies would be useful.
Date: August 19, 2006
Creator: Guetersloh, Stephen B.; Zeitlin, Cary; Heilbronn, Lawrence H.; Miller, Jack; Komiyama, Tatsudo; Fukumura, A. et al.
Partner: UNT Libraries Government Documents Department

Muon-induced backgrounds in the CUORICINO experiment

Description: To better understand the contribution of cosmic ray muons to the CUORICINO background, ten plastic scintillator detectors were installed at the CUORICINO siteand operated during the final 3 months of the experiment. From these measurements, an upper limit of 0.0021 counts/(keV.kg.yr) (95percent c.l.) was obtained on the cosmicray induced background in the neutrinoless double beta decay region of interest. The measurements were also compared to Geant4 simulations.
Date: April 15, 2010
Creator: Andreotti, E.; Arnaboldi, C.; Avignone III, F. T.; Balata, M.; Bandac, I.; Barucci, M. et al.
Partner: UNT Libraries Government Documents Department

Fragmentation Cross Sections of 290 and 400 MeV/nucleon 12C Beamson Elemental Targets

Description: Charge-changing and fragment production cross sections at 0circ have been obtained for interactions of 290 MeV/nucleon and 400MeV/nucleon carbon beams with C, CH2, Al, Cu, Sn, and Pb targets. Thesebeams are relevant to cancer therapy, space radiation, and the productionof radioactive beams. We compare to previously published results using Cand CH2 targets at similar beam energies. Due to ambiguities arising fromthe presence of multiple fragments on many events, previous publicationshave reported only cross sections for B and Be fragments. In this work wehave extracted cross sections for all fragment species, using dataobtained at three distinct values of angular acceptance, supplemented bydata taken with the detector stack placed off the beam axis. A simulationof the experiment with the PHITS Monte Carlo code shows fair agreementwith the data obtained with the large acceptance detectors, but agreementis poor at small acceptance. The measured cross sections are alsocompared to the predictions of the one-dimensional cross section modelsEPAX2 and NUCFRG2; the latter is presently used in NASA's space radiationtransport calculations. Though PHITS and NUCFRG2 reproduce thecharge-changing cross sections with reasonable accuracy, none of themodels is able to accurately predict the fragment cross sections for allfragment species and target materials.
Date: March 17, 2007
Creator: Zeitlin, C.; Guetersloh, S.; Heilbronn, L.; Miller, J.; Fukumura,A.; Iwata, Y. et al.
Partner: UNT Libraries Government Documents Department

Monte Carlo Simulations of Cosmic Rays Hadronic Interactions

Description: This document describes the construction and results of the MaCoR software tool, developed to model the hadronic interactions of cosmic rays with different geometries of materials. The ubiquity of cosmic radiation in the environment results in the activation of stable isotopes, referred to as cosmogenic activities. The objective is to use this application in conjunction with a model of the MAJORANA DEMONSTRATOR components, from extraction to deployment, to evaluate cosmogenic activation of such components before and after deployment. The cosmic ray showers include several types of particles with a wide range of energy (MeV to GeV). It is infeasible to compute an exact result with a deterministic algorithm for this problem; Monte Carlo simulations are a more suitable approach to model cosmic ray hadronic interactions. In order to validate the results generated by the application, a test comparing experimental muon flux measurements and those predicted by the application is presented. The experimental and simulated results have a deviation of 3%.
Date: April 1, 2011
Creator: Aguayo Navarrete, Estanislao; Orrell, John L. & Kouzes, Richard T.
Partner: UNT Libraries Government Documents Department

Assessment of Cosmic Background Attenuation at Building 3425 (Underground Laboratory)

Description: Specifications for the Underground Facility (building 3425) in the Radiation Detection and Nuclear Sciences complex presently under construction at Pacific Northwest National Laboratory mandate a 30 meters water equivalent shielding for cosmic background attenuation at the 30-foot underground depth of the laboratory. A set thickness of a specified fill material was determined; however a smaller thickness of a higher density material was used for the earthen bunker. Questions arose as to whether this altered configuration met the required shielding specifications. A series of measurements were made to address this concern using a 4”x4”x16” NaI(Tl) detector (Scionix Holland, 3.5N-E2-X). Cosmic ray data were taken at the surface, and at several locations within the underground facility in order to obtain an experimental value for the attenuation of the cosmic radiation. This experimental result was compared with the contracted attenuation.
Date: October 1, 2009
Creator: Kouzes, Richard T.; Borgardt, James D.; Lintereur, Azaree T. & Panisko, Mark E.
Partner: UNT Libraries Government Documents Department

Measurements of Materials Shielding Properties with 1 GeV/nuc56Fe

Description: The design of future spacecraft such as the Crew ExplorationVehicle must take into account the radiation shielding properties of boththe structural components as well as dedicated shielding materials. Sincemodest depths of shielding stop the vast majority of Solar EnergeticParticles (SEP), the greater challenge is posed by the need to shieldcrew from the Galactic Cosmic Rays (GCR), which include highly-chargedand highly-energetic particles. Here, we report on results from testsperformed with beams of 1 GeV/nuc 56Fe at the Brookhaven NationalLaboratory. A wide variety of targets, both elemental and composite, wereplaced in the particle beams, and the spectra of particles emerging fromthe targets were measured using a stack of silicon detectors. Results arepresented primarily in terms of dose reduction per g cm-2 of targetmaterial, and support the conclusions of an earlier calculation by Wilsonet al. showing that performance improves as the shield's mass numberdecreases, with hydrogen being by far the most effective. The data alsoshow that, as depth increases, the incremental benefit of addingshielding decreases, particularlyfor aluminum and other elements withhigher atomic mass numbers.
Date: May 15, 2006
Creator: Zeitlin, Cary; Guetersloh, Stephen B.; Heilbronn, Lawrence H. & Miller, Jack
Partner: UNT Libraries Government Documents Department

Calibration and Characterization of the IceCube Photomultiplier Tube

Description: Over 5,000 PMTs are being deployed at the South Pole to compose the IceCube neutrino observatory. Many are placed deep in the ice to detect Cherenkov light emitted by the products of high-energy neutrino interactions, and others are frozen into tanks on the surface to detect particles from atmospheric cosmic ray showers. IceCube is using the 10-inch diameter R7081-02 made by Hamamatsu Photonics. This paper describes the laboratory characterization and calibration of these PMTs before deployment. PMTs were illuminated with pulses ranging from single photons to saturation level. Parameterizations are given for the single photoelectron charge spectrum and the saturation behavior. Time resolution, late pulses and afterpulses are characterized. Because the PMTs are relatively large, the cathode sensitivity uniformity was measured. The absolute photon detection efficiency was calibrated using Rayleigh-scattered photons from a nitrogen laser. Measured characteristics are discussed in the context of their relevance to IceCube event reconstruction and simulation efforts.
Date: February 11, 2010
Creator: Collaboration, IceCube; Abbasi, R. & al., et
Partner: UNT Libraries Government Documents Department

Muon Fluence Measurements for Homeland Security Applications

Description: This report focuses on work conducted at Pacific Northwest National Laboratory to better characterize aspects of backgrounds in RPMs deployed for homeland security purposes. Two polyvinyl toluene scintillators were utilized with supporting NIM electronics to measure the muon coincidence rate. Muon spallation is one mechanism by which background neutrons are produced. The measurements performed concentrated on a broad investigation of the dependence of the muon flux on a) variations in solid angle subtended by the detector; b) the detector inclination with the horizontal; c) depth underground; and d) diurnal effects. These tests were conducted inside at Building 318/133, outdoors at Building 331G, and underground at Building 3425 at Pacific Northwest National Laboratory.
Date: August 10, 2010
Creator: Ankney, Austin S.; Berguson, Timothy J.; Borgardt, James D. & Kouzes, Richard T.
Partner: UNT Libraries Government Documents Department

Skyshine Contribution to Gamma Ray Background Between 0 and 4 MeV

Description: Natural gamma-ray background is composed of four components; which include cosmic rays, cosmic ray produced atmospheric activity, terrestrial sources, and skyshine from terrestrial sources. Skyshine is radiation scattered from the air above a source that can produce a signal in radiation detection instrumentation. Skyshine has been studied for many years but its contribution to the natural background observed in a detector has not been studied. A large NaI(Tl) detector was used to investigate each of the four components of the natural background using a series of 48-hour measurements and appropriate lead shielding configured to discriminate contributions from each component. It was found that while the contribution from skyshine decreases rapidly with energy, it represents a significant portion of the background spectrum below ~500keV. A similar campaign of measurements using a HPGe detector is underway.
Date: August 14, 2009
Creator: Mitchell, Allison L.; Borgardt, James D. & Kouzes, Richard T.
Partner: UNT Libraries Government Documents Department

Study of the Production of Radioactive Isotopes through Cosmic Muon Spallation in KamLAND

Description: Radioactive isotopes produced through cosmic muon spallation are a background for rare event detection in {nu} detectors, double-beta-decay experiments, and dark-matter searches. Understanding the nature of cosmogenic backgrounds is particularly important for future experiments aiming to determine the pep and CNO solar neutrino fluxes, for which the background is dominated by the spallation production of {sup 11}C. Data from the Kamioka Liquid scintillator Anti-Neutrino Detector (KamLAND) provides valuable information for better understanding these backgrounds, especially in liquid scintillator, and for checking estimates from current simulations based upon MUSIC, FLUKA, and Geant4. Using the time correlation between detected muons and neutron captures, the neutron production yield in the KamLAND liquid scintillator is measured to be (2.8 {+-} 0.3) x 10{sup -4} n/({mu} {center_dot} (g/cm{sup 2})). For other isotopes, the production yield is determined from the observed time correlation related to known isotope lifetimes. We find some yields are inconsistent with extrapolations based on an accelerator muon beam experiment.
Date: June 30, 2009
Creator: Collaboration, KamLAND; Abe, S.; Enomoto, S.; Furuno, K.; Gando, Y.; Ikeda, H. et al.
Partner: UNT Libraries Government Documents Department

Simulation of radio emission from air showers in atmospheric electric fields

Description: We study the effect of atmospheric electric fields on the radio pulse emitted by cos- mic ray air showers. Under fair weather conditions the dominant part of the radio emission is driven by the geomagnetic field. When the shower charges are accelerated and deflected in an electric field additional radiation is emitted. We simulate this effect with the Monte Carlo code REAS2, using CORSIKA-simulated showers as input. In both codes a routine has been implemented that treats the effect of the electric field on the shower particles. We find that the radio pulse is significantly altered in background fields of the order of ~100 V/cm and higher. Practically, this means that air showers passing through thunderstorms emit radio pulses that are not a reliable measure for the shower energy. Under other weather circumstances significant electric field effects are expected to occur rarely, but nimbostratus clouds can harbor fields that are large enough. In general, the contribution of the electric field to the radio pulse has polarization properties that are different from the geomagnetic pulse. In order to filter out radio pulses that have been affected by electric field effects, radio air shower experiments should keep weatherinformation and perform full polarization measurements of the radio signal.
Date: February 25, 2010
Creator: Buitink, S.; Huege, T.; Falcke, H & Kuijpers, J.
Partner: UNT Libraries Government Documents Department

Radiation events in astronomical CCD images

Description: The remarkable sensitivity of depleted silicon to ionizing radiation is a nuisance to astronomers. ''Cosmic rays'' degrade images because of struck pixels, leading to modified observing strategies and the development of algorithms to remove the unwanted artifacts. In the new-generation CCD's with thick sensitive regions, cosmic-ray muons make recognizable straight tracks and there is enhanced sensitivity to ambient gamma radiation via Compton-scattered electrons (''worms''). Beta emitters inside the dewar, for example high-potassium glasses such as BK7, also produce worm-like tracks. The cosmic-ray muon rate is irreducible and increases with altitude. The gamma rays are mostly by-products of the U and Th decay chains; these elements always appear as traces in concrete and other materials. The Compton recoil event rate can be reduced significantly by the choice of materials in the environment and dewar and by careful shielding. Telescope domes appear to be significantly cleaner than basement laboratories and Coude spectrograph rooms. Radiation sources inside the dewar can be eliminated by judicious choice of materials. Cosmogenic activation during high-altitude flights does not appear to be a problem. Our conclusions are supported by tests at the Lawrence Berkeley National Laboratory low-level counting facilities in Berkeley and at Oroville, California (180 m underground).
Date: December 18, 2001
Creator: Smith, A.R.; McDonald, R.J.; Hurley, D.L.; Holland, S.E.; Groom, D.E.; Brown, W.E. et al.
Partner: UNT Libraries Government Documents Department

Human Round Trip to Mars: Six Months and Radiation Safe

Description: Paper describing a proposal to send a crew on a round trip to Mars that will be relatively fast and safe from radiation dosage from cosmic rays and other sources. It includes background information, descriptions with figures, and discussion regarding a single trip or continuous trips to Mars.
Date: 1991
Creator: Lazareth, Otto W.; Schmidt, Eldon; Ludewig, Hans & Powell, James R.
Partner: UNT Libraries Government Documents Department