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Now showing items 1 - 13 of 13

  • Mercuric Iodide Crystal Growth and Frisch Collar Detector Fabrication

    Ariesanti, E.   Kargar, A.   McGregor, D. S.  

    Being a high-Z material, mercuric iodide (HgI(2)) has a relatively high gamma-ray absorption coefficient. Its low charge carrier mobilities, however, have somewhat hampered the interest in using this material as a room-temperature gamma-ray spectrometer. By using the Frisch collar technology, the influence of the low charge carrier can be significantly reduced. The growth of HgI(2) by the Faile method in a horizontal furnace fortuitously produces tetragonal prismatic crystals. These crystals with appropriate dimensions can be fabricated into Frisch collar spectrometers. With the Frisch collar technology, 1.8% energy resolution for 662-keV gamma rays has been achieved.
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  • Fabrication and spectroscopy results of mercuric iodide Frisch collar detectors

    Ariesanti, E.   Kargar, A.   McGregor, D. S.  

    A tetragonal prismatic HgI2 crystal grown with low molecular weight ((M) over bar (w)) polyethylene addition in a horizontal furnace has been fabricated into a 2 1 x 2 1 x 4 1 mm(3) Frisch collar spectrometer With no electronic correction nor LN2 cooling an energy resolution of 1 8% FWHM at 662 key (Cs-137) is achieved Spectra from Am-241 (47% FWHM at 59 5 keV) Co-57 (40% FWHM at 122 keV) Ba-133 (44% FWHM at 80 keV and 2 5% FWHM at 356 keV) Au-198 (2 6% FWHM at 411 keV) and Co-60 (1 2% FWHM at 1173 keV) are also reported (C) 2010 Elsevier B V All rights reserved
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  • Latest Progress on Advanced Bridgman Method-Grown K2PtCl6 Cubic Structure Scintillator Crystals

    Hawrami, R.   Ariesanti, E.   Buliga, V.   Motakef, S.   Burger, A.  

    We are reporting on the latest growth and scintillating properties of a recently discovered intrinsic scintillating compound with the K2PtCl6 simple cubic crystal structure: the Cs-based Cs2HfCl6 (CHC) and Cs2HfCl4Br2 (CHCB), both with the density of 3.9 g/cm(3), as well as the Tl-based Tl2HfCl6 (THC) and Tl2ZrCl6 (TZC). This article presents a successfully developed process of growing crack-free, single crystals of 16 mm diameter to 1-in-diameter CHC by the Bridgman method. The energy resolution of 2.8% [full-width at half-maximum (FWHM)] at 662 keV has been obtained for small diameters and typical 3.5% (FWHM) at 662 keV has been obtained for 1 in x 1 in CHC. The light yield of 30 000 ph/ MeV and the 3.8 mu s primary decay time have been measured for CHC. CHC's excellent linear response to gamma rays compared to those of NaI:Tl and BGO is also reported. The mixed-halides CHC-based compound CHCB performs with a shorter primary decay time of 1.8 mu s. Introducing Tl, a heavier element than Cs, increases both Zeff and density of THC and TZC, and improves gamma-ray detection efficiency. Primary decay times are also reduced to about 1 mu s for THC and 2 mu s for TZC.
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  • Tl2HfCl6 and Tl2ZrCl6: Intrinsic Tl-, Hf-, and Zr-based scintillators

    Hawrami, R.   Ariesanti, E.   Buliga, V.   Burger, A.   Lam, S.   Motakef, S.  

    The re-discovery of Cs2HfCl6 (CHC) as a scintillator has lately generated much interest in this material and its family, which belongs to the K2PtCl6 cubic crystal structure [1]. CHC is an intrinsic scintillator that is non-hygroscopic, has no self-radioactivity, provides good energy resolution, and has good non-proportionality. In this paper we are reporting growth and scintillation properties of two new and Tl-, Hf- and Zr-based compounds of Tl2HfCl6 and Tl2ZrCl6, with physical densities of 5.1 g/cm(3) and 4.5 g/cm(3), respectively and effective atomic numbers (Z(eff)) of 71 and 69, respectively. Samples from successfully grown 16 mm diameter boules were cut, processed, and characterized for their scintillation and radiometric properties. Energy resolutions of 3.7% (FWHM) for THC and 3.4% for TZC (FWHM) at 662 keV are measured. Primary luminescence decay times of 1.1 mu s and 2.3 mu s, for Tl(2)HfC(l)6 and Tl2ZrCl6, respectively, as well as good proportionality for both materials have been observed.
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  • Cs2LiLa(Br, Cl)(6) Crystals for Nuclear Security Applications

    Hawrami, R.   Pandian, L. Soundara   Ariesanti, E.   Glodo, J.   Finkelstein, J.   Tower, J.   Shah, K.  

    Properties of dual-mode scintillation detectors based on CLLBC crystals are reported. Energy resolution and light yield are measured at 2.9% (FWHM) at 662 keV and 45 000 photons/MeV, respectively, for a 1-in-diameter and 1-in-long crystal. With less than 2% variation in light yield as a function of energy, CLLBC has better proportionality than LaBr3 and NaI:Tl. Neutron peak resulting from reactions with neutrons emitted by Cf-252 (moderated) is measured at a gamma energy equivalent of 3.1 MeVee (electron energy equivalent), making pulse height discrimination between gamma-rays and neutrons easy. The material is also of effective pulse shape discrimination. The figure-of-merit for discrimination of gamma rays and thermal neutrons in CLLBC can be as high as 3.2, which is comparable to that of CLYC.
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  • Thallium strontium iodide:A high efficiency scintillator for gamma-ray detection

    Hawrami, R.   Ariesanti, E.   Buliga, V.   Burger, A.  

    Europium-doped TlSr2I5 (TSI), a new high light yield scintillator for gamma-ray detection, has been grown by the vertical Bridgman method. A 12 mm and 16 mm diameter boules of TSI is grown in a two-zone vertical furnaces. Samples extracted from the grown boule have been characterized for their scintillation properties. Energy resolution of <3% (FWHM) at 662 keV and a gamma-ray light yield of approximately 54,000 Ph/MeV have been obtained. Decay times of 395 ns (89%) and 2.0 mu s (11%) have been measured.
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  • Advanced high-performance large diameter Cs2HfCl6 (CHC) and mixed halides scintillator

    Hawrami, R.   Ariesanti, E.   Buliga, V   Matei, L.   Motakef, S.   Burger, A.  

    This paper reports on successful growth and performance evaluation of two large diameter Cs2HfCl6 (CHC) and Cs2HfCl4Br2 (CHCB), both recently developed scintillator crystals. The discovery of Cs2HfCl6 (CHC) as a scintillator has lately generated much interest in this material and its family, which belongs to the K2PtCl6 cubic crystal structure. CHC is an intrinsic scintillator that is non-hygroscopic (slightly deliquescent, i.e., slightly moisture sensitive but does not deteriorate much when left in air), has no self-radioactivity, provides excellent energy resolution, and has excellent non-proportionality. CHC has a moderate density of 3.9 g/cm(3) and an effective atomic number of 58. Reported in this paper are transparent crack-free single crystal CHC and CHCB boules of one inch in diameter, both grown using the vertical Bridgman method. Samples retrieved from the boules, sized empty set23 mm x 30 mm and empty set23 mm x 26 mm, respectively, are characterized for their optical and scintillation properties. Energy resolutions of 3.5% and 3.7% (FWHM) at 662 keV, respectively, are reported. Light yields of 23,000 ph/MeV and 20,000 ph/MeV have been calculated for the large diameter CHC and CHCB crystals, respectively. Results comparable to previously reported results for smaller crystals have been obtained. Studies on decay time, non-proportionality, as well as detector characterization are also reported.
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  • [IEEE 2016 IEEE Nuclear Science Symposium, Medical Imaging Conference and Room-Temperature Semiconductor Detector Workshop (NSS/MIC/RTSD) - Strasbourg, France (2016.10.29-2016.11.6)] 2016 IEEE Nuclear Science Symposium, Medical Imaging Conference and Room-Temperature Semiconductor Detector Workshop (NSS/MIC/RTSD) - Effects of cerium concentration in Tl2LiYCl6 scintillation detectors

    Ariesanti, E.   Hawrami, R.   Finkelstein, J.   Wei, H.   Soundara-Pandian, L.   Glodo, J.   Shah, K.  

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  • Charge collection efficiency characterization of a HgI(2) Frisch collar spectrometer with collimated high energy gamma rays

    Kargar, A.   Ariesanti, E.   James, S.   McGregor, D. S.  

    In this study, a 2.1 x 2.1 x 4.1 mm(3) HgI(2) Frisch collar device was characterized through probing the device with a highly collimated 662 keV gamma rays ((137)Cs check source) along the length and width of the device. In a systematic series of experiments, the detector was probed along its central line under different operating voltages of 1600, 1300, 1000, 800, 600 and 500 V. The experimental results were confirmed through a simulation of the charge collection for a device with the same size and operating conditions. It is shown that the HgI(2) Frisch collar device has a uniform response to gamma rays over two-thirds of the detector volume. The HgI(2) crystals and the Frisch collar detectors were grown and fabricated within the S.M.A.R.T Laboratory at Kansas State University. (C) 2010 Elsevier B.V. All rights reserved.
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  • TI2LiYCI6: Large Diameter, High Performing Dual Mode Scintillator

    Hawrami, R.   Ariesanti, E.   Wei, H.   Finkelstein, J.   Glodo, J.   Shah, K.  

    Tl2LiYCl6:Ce (TLYC) is a recently discovered dual mode gamma-ray and neutron scintillator. So far small crystals of this composition have been studied, but for, practical applications with affordable price, large-scale crystals are required. In this work, we present successful efforts to grow crack-free single crystals with sizes up to emptyset1" X 5.5". A variety of experimental techniques were employed to investigate the scintillation properties. A emptyset1" X 1.2" TLYC cylinder has a light yield of 25,000 ph/MeV, and its energy resolution is better than 4% at 662 keV. The gamma equivalent energy (GEE) produced by thermal neutron is 1.89 MeVee, along with a neutron induced light yield of 47,000 ph/n. Pulse shape discrimination (PSD) between gamma-rays and neutrons has been successfully shown with a current Figure-of-Merit (FOM) of 2.4. This article explores the crystal growth, scintillation properties, and potential applications of TLYC.
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  • Tl2LaCl5: Ce, high performance scintillator for gamma-ray detectors

    Hawrami, R.   Ariesanti, E.   Wei, H.   Finkelstein, J.   Glodo, J.   Shah, K. S.  

    This paper reports on a new Ce-doped Tl-based scintillator, Tl2LaCl5 (TLC), for gamma-ray detection. 10 mm diameter crystals have been successfully grown using the vertical Bridgman method. The emission peak of TLC is detected at 383 nm under X-ray excitation. The light yield of TLC is 76,000 ph/MeV. The samples show excellent energy resolution of 3.4% (FWHM) at 662 keV. The non-proportionality is less than 1%, from 32 keV to 1275 keV. The major scintillation decay time is 36 ns. (C) 2017 Elsevier B. V. All rights reserved.
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  • Tl2LiYCl6:Ce: A New Elpasolite Scintillator

    Hawrami, R.   Ariesanti, E.   Soundara-Pandian, L.   Glodo, J.   Shah, K. S.  

    Tl2LiYCl6:Ce (TLYC), a new cerium doped-thallium based, dual mode gamma and neutron elpasolite scintillation crystal, has been grown and evaluated at RMD. Energy resolution of 4.2% at 662 keV (FWHM) is measured for samples of this material. From comparison with a Cs-137 spectrum collected with NaI:Tl, a gamma-ray induced light yield of 26,000 ph/MeV is estimated for TLYC. The material also shows better proportionality of response than both LaBr3:Ce and NaI: Tl in the energy range between 32 keV to 1275 keV. Single thermal neutron interactions produce a peak measured at a gamma equivalent energy of 1.9 MeVee, corresponding to a (neutron induced) light yield of approximately 47,000 ph/n. Decay times obtained from gamma-ray interactions in TLYC are measured at about 57 ns, 431 ns, and 1055 ns, with slightly shorter values measured for neutron interactions. These differences allow for gamma-neutron pulse shape discrimination (PSD) and a PSD Figure-of-Merit (FOM) of 2 is measured with TLYC.
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  • Intrinsic scintillators: TlMgCl3 and TlCaI3

    Hawrami, R.   Ariesanti, E.   Wei, H.   Finkelstein, J.   Glodo, J.   Shah, K. S.  

    Two intrinsic scintillators TlMgCl3 and TlCaI3 with excellent energy resolution and fast scintillation decay are presented. Crack-free transparent crystals were successfully grown by the Bridgman method. The scintillation light yields of TlMgCl3 and TlCaI3 are approximately 30,600 ph/MeV and 42,200 ph/MeV, respectively. Their energy resolutions at 662 keV are 3.7% for TlMgCl3 and 6.2% for TlCaI3. The scintillation decay times of TlMgCl3 are 46 ns, 166 ns, and 449 ns. The scintillation decay times of TlCaI3 are 62 ns, 200 ns, and 1.44 mu s. Under X-ray irradiation, the emission of TlMgCl3 is between 300 nm and 540 nm with the peak at 409 nm. TlCaI3 has a broad emission band between 300 nm and 750 nm. Due to their excellent scintillation properties, these two scintillators can be developed for gamma-ray detection. Additionally, TlMgCl3 is non-hygroscopic. (C) 2017 Elsevier B.V. All rights reserved.
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