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Now showing items 1 - 15 of 15

  • Fast neutron measurements using Cs2LiYCl6:Ce (CLYC) scintillator

    Smith, M. B.   Achtzehn, T.   Andrews, H. R.   Clifford, E. T. H.   Forget, P.   Glodo, J.   Hawrami, R.   Ing, H.   O'Dougherty, P.   Shah, K. S.   Shirwadkar, U.   Soundarar-Pandian, L.   Tower, J.  

    Samples of Cs2LiYCl6:Ce (CLYC) scintillator have been characterized using monoenergetic neutron beams in the energy range 4.1-5.5 MeV. Four crystals with dimensions (thickness x diameter) of 1" x 1", 1" x 2", and 2" x 2" were evaluated, including one crystal with natural concentrations of Li isotopes and three that were enriched in Li. The intrinsic efficiency of CLYC for fast-neutron detection has been determined for the natural-Li crystal. These measurements were translated into reaction cross-sections, and show good agreement with available cross-section data for neutron interactions with the Cl-35 component of CLYC. Furthermore, it is shown that the charged-particle energy released in the fast-neutron reactions on Cl-35 varies linearly with the energy of the incoming neutron. These results verify the efficacy of CLYC for fast-neutron spectroscopy in a range of applications. (C) 2014 Elsevier B.V. All rights reserved.
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  • Promising Alkaline Earth Halide Scintillators for Gamma-Ray Spectroscopy

    Shirwadkar, U.   Hawrami, R.   Glodo, J.   van Loef, E. V. D.   Shah, K. S.  

    Up to 1-in-diameter, Eu-doped CsBa2I5 and BaBrI crystals have been grown using the vertical Bridgman method. Scintillation properties of the crystals up to similar to 1 x 1 x cm(3) have been studied under gamma-ray irradiation. Systematic concentration studies have been performed for both these alkaline earth halides with Eu2+ doping levels ranging from 0% to 10% to optimize growth of large crystals. We have achieved excellent energy resolution of similar to 2.6% at 662 keV for a 2 x 2 x 1-mm(3) sample of CsBa2I5:2% Eu. However, in this paper, the emphasis is on the larger crystals that can be used practically in nuclear nonproliferation applications. Our measurements of a 1.0 x 1.0 x 1.0-cm(3) sample of CsBa2I5:3% Eu, processed from a 1-in-diameter crystal, shows very good energy resolution of 3.9% at 662 keV, high light output of similar to 80 000 photons/MeV, and a principal decay time of similar to 900 ns. The second investigated composition, BaBrI:5% Eu, 1.0-cm-diameter x 1.0-cm-thick sample shows high light output of 71 000 photons/MeV and energy resolution of 4.3% at 662 keV. A decay time of 480 ns was measured for this sample, which is shorter than most Eu2+ doped materials of this size. The emission in these materials is due to d -> f transitions of Eu2+ and occurs over a single band between 400-500 nm. It peaks at similar to 430 nm for CsBa2I5:Eu and at similar to 413 nm for BaBrI: Eu. Since both compositions show high proportionality over a wide range of energies, we expect to see improvements in the energy resolution of large crystals, as better quality of 1-in-diameter crystals are grown.
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  • Optimizing Cs2LiYCl6 for fast neutron spectroscopy

    D'Olympia, N.   Chowdhury, P.   Guess, C. J.   Harrington, T.   Jackson, E. G.   Lakshmi, S.   Lister, C. J.   Glodo, J.   Hawrami, R.   Shah, K.   Shirwadkar, U.  

    Cs2UYCl6 (CLYC) has generated recent interest as a thermal neutron detector due to its excellent n/gamma-ray pulse-shape discrimination and energy resolution. Here, the capabilities of CLYC as a fast neutron detector and spectrometer are reported. A 1 in. x 1 in. CLYC detector was used to measure the response of mono-energetic neutrons over a range of 0.8-2.0 MeV produced via the Li-7(p,n) reaction at the University of Massachusetts Lowell 5.5 MV Van de Graaff accelerator. A broad continuum from the Li-6(n, alpha) reaction was observed, as well as additional peaks below the thermal capture peak. Based on possible reactions in CLYC, the additional peaks are determined to be due to the Cl-35(n,p)S-35 reaction, with a Q-value of +615 keV, and corroborated in simulations using MCNPX. The average resolution of 9% for these peaks makes CLYC a promising candidate for a fast neutron spectrometer. Published by Elsevier B.V.
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  • Growth and characterization of polycrystalline lanthanide halide scintillators

    Nagarkar, V. V.   Miller, S. R.   Gelfandbein, V.   Shirwadkar, U.   Gaysinskiy, V.  

    We are exploring a novel time- and cost-efficient approach to produce robust, large-volume polycrystalline lanthanide halide scintillators using a hot wall evaporation (HWE) technique. To date, we have fabricated LaBr(3):Ce and LaCI(3):Ce films (slabs) measuring up to 7 cm in diameter and 7+ mm in thickness (20-25 cm(3) in volume) on quartz substrates. These polycrystalline scintillators exhibit very bright emissions approaching those exhibited by their melt-grown crystal counterparts. Scanning electron micrographs (SEMs) and X-ray diffraction analysis confirm polycrystalline growth with columnar structures, both of which help in light piping, thereby contributing to the observed high light yields. The new scintillators also exhibit good energy resolution for gamma-rays over the tested range of 60 key ((241)Am) to 662 key ((137)Cs), although they have not yet reached that of the corresponding crystals. The measured response linearity over the same energy range is comparable for both our HWE synthesized films and melt-grown commercially-available reference crystals. Similar consistency in response is also observed in terms of their decay time and afterglow behaviors. The data collected so far demonstrate that our HWE technique permits the rapid creation of scintillators with desired structural and compositional characteristics, without the introduction of appreciable defects, and yields material performance equivalent to or approaching that of crystals. Consequently, the deposition parameters may be manipulated to tailor the physical and scintillation performance of the resulting structures, while achieving a cost per unit volume that is substantially lower than that of crystals. In turn, this promises to allow the use of these novel scintillation materials in such applications as SPECT, PET, room-temperature radioisotope identification and homeland security, where large volumes of materials in a wide variety of shapes and sizes are needed. This paper describes our growth and testing of polycrystalline LaBr3:Ce scintillators and provides comparative characterizations of their performance with crystals. (C) 2010 Elsevier B.V. All rights reserved.
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  • Pulse-shape analysis of CLYC for thermal neutrons, fast neutrons, and gamma-rays

    D'Olympia, N.   Chowdhury, P.   Lister, C. J.   Glodo, J.   Hawrami, R.   Shah, K.   Shirwadkar, U.  

    Cs2LiYCl6:Ce (CLYC) has been demonstrated to be sensitive to thermal neutrons via the Li-6(n, alpha)t reaction, and recently to fast neutrons via the Cl-35(n,p) reaction. The scintillation properties of CLYC have been investigated in more detail to further understand its capabilities. Pulses from thermal neutron, fast neutron, and gamma-ray induced excitations were captured, digitized over a 16 mu s time range, and analyzed to identify the scintillation mechanisms responsible for the observed shapes. Additionally, the timing resolutions of CLYC crystals of different sizes were measured in coincidence with a fast CeBr3 scintillator. The effect of high count rates on fast neutron energy resolution and pulse-shape discrimination was investigated up to 45 kHz. Published by Elsevier B.V.
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  • Triplet harvesting plastic scintillators with neutron-gamma pulse shape discrimination

    van Loef, E.V.   Feng, P.   Markosyan, G.   Shirwadkar, U.   Doty, P.   Shah, K.  

    In this paper we report on plastic scintillators that contain organometallic iridium compounds as triplet harvesting complexes for neutron-gamma pulse shape discrimination (PSD). Our results show that these plastic scintillators have a relatively high light output (higher than BGO) and exhibit very good neutron-gamma PSD with a Figure-of-Merit of ges 2.0 at 2.5 MeVee cut-off energy. Under X-ray excitation, the radioluminescence spectrum exhibits a broad band between 400 and 650 nm peaking at 470 nm which is well-matched to bialkali photomultiplier tubes and UV-enhanced photodiodes. The scintillation decay due to Ir 3+ luminescence is of the order of 1 us.
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  • [IEEE 2011 IEEE Nuclear Science Symposium and Medical Imaging Conference (2011 NSS/MIC) - Valencia, Spain (2011.10.23-2011.10.29)] 2011 IEEE Nuclear Science Symposium Conference Record - New promising scintillators for gamma-ray spectroscopy: Cs(Ba,Sr)(Br,I)3

    Shirwadkar, U.   van Loef, E.V.D.   Hawrami, R.   Mukhopadhyay, S.   Glodo, J.   Shah, K. S.  

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  • [IEEE 2015 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC) - San Diego, CA, USA (2015.10.31-2015.11.7)] 2015 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC) - Metal-loaded plastic scintillators for nuclear non-proliferation

    Shirwadkar, U.   Van Loef, E. V. D.   Markosyan, G.   McClish, Mickel   Glodo, J.   Shah, K.S.  

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  • [IEEE 2014 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC) - Seattle, WA, USA (2014.11.8-2014.11.15)] 2014 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC) - Scintillation properties of lanthanum yttrium oxide ceramic for gamma-ray detection

    Shirwadkar, U.   Rhodes, W. H.   Brecher, C.   Baldoni, G.   Wang, Y.   McClish, M.   Gupta, T.   Glodo, J.   Shah, K.  

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  • [IEEE 2006 IFIP International Conference on Wireless and Optical Communications Networks - Bangalore, India (11-13 April 2006)] 2006 IFIP International Conference on Wireless and Optical Communications Networks - A New End-to-End QoS mechanism for video delivery over Heterogeneous Networks

    Shirwadkar, U.   Chilamkurti, N.   Chih-Heng Ke,    Shieh, C.K.  

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  • [IEEE 2012 IEEE Nuclear Science Symposium and Medical Imaging Conference (2012 NSS/MIC) - Anaheim, CA, USA (2012.10.27-2012.11.3)] 2012 IEEE Nuclear Science Symposium and Medical Imaging Conference Record (NSS/MIC) - Novel scintillation material Cs2LiLaBr6?xClx:Ce for gamma-ray and neutron spectroscopy

    Shirwadkar, U.   Hawrami, R.   Glodo, J.   Van Loef, E.V.D.   Shah, K.S.  

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  • Spectroscopy of selected alkaline earth halides

    Glodo, J.   van Loef, E.   Hawrami, R.   Shirwadkar, U.   Mukhopadhyay, S.   Shah, K.S.  

    Recently a number of alkaline earth halide scintillators doped with Eu 2+ have been reported on. They are characterized by very good proportionality, high up to 100,000 photons/MeV light yield, and very good energy resolution, as low as 2.8% at 662 keV. Yet, one of the issues facing these materials is radiation trapping. Radiation trapping results from a small Stokes shift that creates considerable overlap between emission and absorption bands. As a result the scintillation light is absorbed and emitted multiple times, leading to a prolongation of the scintillation decay, potential light losses and degradation of energy resolution. Spectroscopic properties of various Eu 2+ doped alkaline earth halides are presented. Materials studied include: SrI 2, BaI 2, BaBrI and other compounds. It appears that some compositions are less affected by radiation trapping.
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  • A New End-to-End QoS mechanism for video delivery over Heterogeneous Networks

    Shirwadkar, U.   Chilamkurti, N.   Chih-Heng Ke   Shieh, C.K.  

    The need for QoS for multimedia traffic arouse from the fact that the current network is a best effort network where all packets are treated equally irrespective of their importance. Moreover when a video packet changes its mode of transport from wired to wireless there arises a need to identify these packets and provide them with prioritized service to achieve end-to-end QoS. In this paper we used a DiffServ network model for the wired network where the INGRESS executed Enhanced Token Bucket Three Marker System (ETBMS). The framework also describes a Video differentiator present in the Access Point which identifies the video packets and maps it to corresponding IEEE 802.11e prioritized video service queue. We demonstrated via simulation the proposed concept and examined the QoS parameters like end-to-end delay and Video Quality. The results illustrate that the proposed scheme exhibits better video delivery and QoS in heterogeneous networks.
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  • Investigating scintillation properties of Ce doped Cs 2LiYBr 6

    Shirwadkar, U.   Glodo, J.   Van Loef, E.   Hawrami, R.   Mukhopadhyay, S.   Shah, K.S.  

    A promising composition, Ce doped Cs 2LiYBr 6 (CLYB) originally introduced by van Loef et al. has been investigated recently as a gamma-ray and neutron detector. It belongs to the elpasolite family and has a cubic structure. A single crystal of this material has been grown using the vertical Bridgman method. Scintillation properties such as energy resolution, emission, light yield, non-proportionality, and decay times are discussed in this paper. It can be used effectively to discriminate between the gamma and neutron events using pulse-shape discrimination (PSD) technique.
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  • Novel organic scintillators for neutron detection

    van Loef, E.V.   Glodo, J.   Shirwadkar, U.   Zaitseva, N.   Shah, K.S.  

    In this paper we report on novel organic scintillators in the form of single crystals for neutron detection. In particular, we focus on 9,10-Diphenylanthracene, Tetraphenylbutadiene, and Lithium-Salicylate, grown from solution.
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