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Search Results: 1 - 10 of 138740 matches for " K. Kazkaz "
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Fabrication and characterization of a lithium-glass-based composite neutron detector
G. C. Rich,K. Kazkaz,H. P. Martinez,T. Gushue
Physics , 2014, DOI: 10.1016/j.nima.2015.05.004
Abstract: A novel composite, scintillating material intended for neutron detection and composed of small (1.5 mm) cubes of KG2-type lithium glass embedded in a matrix of scintillating plastic has been developed in the form of a 2.2 in.-diameter, 3.1 in.-tall cylindrical prototype loaded with $\left( 5.82 \pm 0.02 \right)\%$ lithium glass by mass. The response of the material when exposed to ${}^{252}$Cf fission neutrons and various $\gamma$-ray sources has been studied; using the charge-integration method for pulse shape discrimination, good separation between neutron and $\gamma$-ray events is observed and intrinsic efficiencies of $\left( 1.15 \pm 0.16 \right)\times 10^{-2}$ and $\left( 2.28 \pm 0.21 \right)\times 10^{-4}$ for ${}^{252}$Cf fission neutrons and ${}^{60}$Co $\gamma$ rays are obtained; an upper limit for the sensitivity to ${}^{137}$Cs $\gamma$ rays is determined to be $< 3.70 \times 10^{-8}$. The neutron/$\gamma$ discrimination capabilities are improved in circumstances when a neutron capture signal in the lithium glass can be detected in coincidence with a preceding elastic scattering event in the plastic scintillator; with this coincidence requirement, the intrinsic efficiency of the prototype detector for ${}^{60}$Co $\gamma$ rays is $\left( 2.42 \pm 0.61 \right)\times 10^{-6}$ while its intrinsic efficiency for unmoderated ${}^{252}$Cf fission neutrons is $\left( 4.31 \pm 0.59 \right)\times 10^{-3}$. Through use of subregion-integration ratios in addition to the coincidence requirement, the efficiency for $\gamma$ rays from ${}^{60}$Co is reduced to $\left( 7.15 \pm 4.10 \right) \times 10^{-7}$ while the ${}^{252}$Cf fission neutron efficiency becomes $\left( 2.78 \pm 0.38 \right) \times 10^{-3}$.
Neutron Inelastic Scattering Processes as Background for Double-Beta Decay Experiments
D. -M. Mei,S. R. Elliott,A. Hime,V. Gehman,K. Kazkaz
Physics , 2007, DOI: 10.1103/PhysRevC.77.054614
Abstract: We investigate several Pb$(n,n'\gamma$) and Ge$(n,n'\gamma$) reactions. We measure $\gamma$-ray production from Pb$(n,n'\gamma$) reactions that can be a significant background for double-beta decay experiments which use lead as a massive inner shield. Particularly worrisome for Ge-based double-beta decay experiments are the 2041-keV and 3062-keV $\gamma$ rays produced via Pb$(n,n'\gamma$). The former is very close to the ^{76}Ge double-beta decay endpoint energy and the latter has a double escape peak energy near the endpoint. Excitation $\gamma$-ray lines from Ge$(n,n'\gamma$) reactions are also observed. We consider the contribution of such backgrounds and their impact on the sensitivity of next-generation searches for neutrinoless double-beta decay using enriched germanium detectors.
Pulse shape analysis in segmented detectors as a technique for background reduction in Ge double-beta decay experiments
S. R. Elliott,V. M. Gehman,K. Kazkaz,D-M. Mei,A. R. Young
Physics , 2005, DOI: 10.1016/j.nima.2005.12.024
Abstract: The need to understand and reject backgrounds in Ge-diode detector double-beta decay experiments has given rise to the development of pulse shape analysis in such detectors to discern single-site energy deposits from multiple-site deposits. Here, we extend this analysis to segmented Ge detectors to study the effectiveness of combining segmentation with pulse shape analysis to identify the multiplicity of the energy deposits.
Combining Stochastics and Analytics for a Fast Monte Carlo Decay Chain Generator
Kareem Kazkaz,Nick Walsh
Physics , 2011, DOI: 10.1016/j.nima.2011.06.069
Abstract: Various Monte Carlo programs, developed either by small groups or widely available, have been used to calculate the effects of decays of radioactive chains, from the original parent nucleus to the final stable isotopes. These chains include uranium, thorium, radon, and others, and generally have long-lived parent nuclei. Generating decays within these chains requires a certain amount of computing overhead related to simulating unnecessary decays, time-ordering the final results in post-processing, or both. We present a combination analytic/stochastic algorithm for creating a time-ordered set of decays with position and time correlations, and starting with an arbitrary source age. Thus the simulation costs are greatly reduced, while at the same time avoiding chronological post-processing. We discuss optimization methods within the approach to minimize calculation time.
NEST: A Comprehensive Model for Scintillation Yield in Liquid Xenon
M. Szydagis,N. Barry,K. Kazkaz,J. Mock,D. Stolp,M. Sweany,M. Tripathi,S. Uvarov,N. Walsh,M. Woods
Physics , 2011,
Abstract: A comprehensive model for explaining scintillation yield in liquid xenon is introduced. We unify various definitions of work function which abound in the literature and incorporate all available data on electron recoil scintillation yield. This results in a better understanding of electron recoil, and facilitates an improved description of nuclear recoil. An incident gamma energy range of O(1 keV) to O(1 MeV) and electric fields between 0 and O(10 kV/cm) are incorporated into this heuristic model. We show results from a Geant4 implementation, but because the model has a few free parameters, implementation in any simulation package should be simple. We use a quasi-empirical approach, with an objective of improving detector calibrations and performance verification. The model will aid in the design and optimization of future detectors. This model is also easy to extend to other noble elements. In this paper we lay the foundation for an exhaustive simulation code which we call NEST (Noble Element Simulation Technique).
First demonstration of a sub-keV electron recoil energy threshold in a liquid argon ionization chamber
S. Sangiorgio,T. H. Joshi,A. Bernstein,J. Coleman,M. Foxe,C. Hagmann,I. Jovanovic,K. Kazkaz,K. Mavrokoridis,V. Mozin,S. Pereverzev,P. Sorensen
Physics , 2013, DOI: 10.1016/j.nima.2013.06.061
Abstract: We describe the first demonstration of a sub-keV electron recoil energy threshold in a dual-phase liquid argon time projection chamber. This is an important step in an effort to develop a detector capable of identifying the ionization signal resulting from nuclear recoils with energies of order a few keV and below. We obtained this result by observing the peaks in the energy spectrum at 2.82 keV and 0.27 keV, following the K- and L-shell electron capture decay of Ar-37, respectively. The Ar-37 source preparation is described in detail, since it enables calibration that may also prove useful in dark matter direct detection experiments. An internally placed Fe-55 x-ray source simultaneously provided another calibration point at 5.9 keV. We discuss the ionization yield and electron recombination in liquid argon at those three calibration energies.
First measurement of the ionization yield of nuclear recoils in liquid argon
T. H. Joshi,S. Sangiorgio,A. Bernstein,M. Foxe,C. Hagmann,I. Jovanovic,K. Kazkaz,V. Mozin,E. B. Norman,S. V. Pereverzev,F. Rebassoo,P. Sorensen
Physics , 2014, DOI: 10.1103/PhysRevLett.112.171303
Abstract: This Letter details a measurement of the ionization yield ($Q_y$) of 6.7 keV $^{40}Ar$ atoms stopping in a liquid argon detector. The $Q_y$ of 3.6-6.3 detected $e^{-}/\mbox{keV}$, for applied electric fields in the range 240--2130 V/cm, is encouraging for the use of this detector medium to search for the signals from hypothetical dark matter particle interactions and from coherent elastic neutrino nucleus scattering. A significant dependence of $Q_y$ on the applied electric field is observed and explained in the context of ion recombination.
Comparison of Lithium Gadolinium Borate Crystal Shards in Scintillating and Nonscintillating Plastic Matrices
Kareem Kazkaz,Nathaniel S. Bowden,Marisa Pedretti
Physics , 2011,
Abstract: We present a method for detecting neutrons using scintillating lithium gadolinium borate crystal shards in a plastic matrix while maintaining high gamma rejection. We have procured two cylindrical detectors, 5"\times5", containing 1% crystal by mass. Crystal shards have a typical dimension of 1 mm. One detector was made with scintillating plastic, and one with nonscintillating plastic. Pulse shape analysis was used to reject gamma ray backgrounds. The scintillating detector was measured to have an intrinsic fast fission neutron efficiency of 0.4% and a gamma sensitivity of less than 2.3 \times 10-9, while the nonscintillating detector had a neutron efficiency of 0.7% and gamma sensitivity of (4.75\pm3.94)\times10-9. We determine that increasing the neutron detection efficiency by a factor of 2 will make the detector competitive with moderated 3He tubes, and we discuss several simple and straightforward methods for obtaining or surpassing such an improvement. We end with a discussion of possible applications, both for the scintillating-plastic and nonscintillating-plastic detectors.
A Model for the Secondary Scintillation Pulse Shape from a Gas Proportional Scintillation Counter
Kareem Kazkaz,Tenzing Henry Yatish Joshi
Physics , 2015,
Abstract: Proportional scintillation counters (PSCs), both single- and dual-phase, can measure the scintillation (S1) and ionization (S2) channels from particle interactions within the detector volume. The signal obtained from these detectors depends first on the physics of the medium (the initial scintillation and ionization), and second how the physics of the detector manipulates the resulting photons and liberated electrons. In this paper we develop a model of the detector physics that incorporates event topology, detector geometry, electric field configuration, purity, optical properties of components, and wavelength shifters. We present an analytic form of the model, which allows for general study of detector design and operation, and a Monte Carlo model which enables a more detailed exploration of S2 events. This model may be used to study systematic effects in currents detectors such as energy and position reconstruction, pulse shape discrimination, event topology, dead time calculations, purity, and electric field uniformity. We present a comparison of this model with experimental data collected with an argon gas proportional scintillation counter (GPSC), operated at 20 C and 1 bar, and irradiated with an internal, collimated 55Fe source. Additionally we discuss how the model may be incorporated in Monte Carlo simulations of both GPSCs and dual-phase detectors, increasing the reliability of the simulation results and allowing for tests of the experimental data analysis algorithms.
A Global Analysis of Light and Charge Yields in Liquid Xenon
Brian Lenardo,Kareem Kazkaz,Aaron Manalaysay,Matthew Szydagis,Mani Tripathi
Physics , 2014,
Abstract: We present an updated model of light and charge yields from nuclear recoils in liquid xenon with a simultaneously constrained parameter set. A global analysis is performed using measurements of electron and photon yields compiled from all available historical data, as well as measurements of the ratio of the two. These data sweep over energies from 1 - 300 keV and external applied electric fields from 0 - 4060 V/cm. The model is constrained by constructing global cost functions and using a gradient descent minimizer, a simulated annealing algorithm, and a Markov Chain Monte Carlo approach to optimize and find confidence intervals on all free parameters in the model. This analysis contrasts with previous work in that we do not unnecessarily exclude data sets nor impose artificially conservative assumptions, do not use spline functions, and reduce the number of parameters used in NEST v0.98. We report our results and the calculated best-fit charge and light yields. These quantities are crucial to understanding the response of liquid xenon detectors in the energy regime important for rare event searches such as the direct detection of dark matter particles.
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