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Now showing items 1 - 16 of 35488

  • Overview of recent experimental results from the Aditya tokamak

    Tanna, R. L.   Ghosh, J.   Chattopadhyay, P. K.   Raj, Harshita   Patel, Sharvil   Dhyani, P.   Gupta, C. N.   Jadeja, K. A.   Patel, K. M.   Bhatt, S. B.   Panchal, V. K.   Patel, N. C.   Chavda, Chhaya   Praveenlal, E. V.   Shah, K. S.   Makawana, M. N.   Jha, S. K.   Gopalkrishana, M. V.   Tahiliani, K.   Sangwan, Deepak   Raju, D.   Nagora, Umesh   Pathak, S. K.   Atrey, P. K.   Purohit, S.   Raval, J.   Joisa, Y. S.   Rao, C. V. S.   Chowdhuri, M. B.   Banerjee, S.   Ramaiya, N.   Manchanda, R.   Thomas, J.   Kumar, Ajai   Ajay, Kumar   Sharma, P. K.   Kulkarni, S. V.   Sathyanarayana, K.   Shukla, B. K.   Das, Amita   Jha, R.   Saxena, Y. C.   Sen, A.   Kaw, P. K.   Bora, D.  

    Several experiments, related to controlled thermonuclear fusion research and highly relevant for large size tokamaks, including ITER, have been carried out in ADITYA, an ohmically heated circular limiter tokamak. Repeatable plasma discharges of a maximum plasma current of similar to 160 kA and discharge duration beyond similar to 250 ms with a plasma current flattop duration of similar to 140 ms have been obtained for the first time in ADITYA. The reproducibility of the discharge reproducibility has been improved considerably with lithium wall conditioning, and improved plasma discharges are obtained by precisely controlling the position of the plasma. In these discharges, chord-averaged electron density similar to 3.0-4.0 x 10(19) m(-3) using multiple hydrogen gas puffs, with a temperature of the order of similar to 500-700 eV, have been achieved. Novel experiments related to disruption control are carried out and disruptions, induced by hydrogen gas puffing, are successfully mitigated using the biased electrode and ion cyclotron resonance pulse techniques. Runaway electrons are successfully mitigated by applying a short local vertical field (LVF) pulse. A thorough disruption database has been generated by identifying the different categories of disruption. Detailed analysis of several hundred disrupted discharges showed that the current quench time is inversely proportional to the q edge. Apart from this, for volt-sec recovery during the plasma formation phase, low loop voltage start-up and current ramp-up experiments have been carried out using electron cyclotron resonance heating (ECRH). Successful recovery of volt-sec leads to the achievement of longer plasma discharge durations. In addition, the neon gas puff assisted radiative improved confinement mode has also been achieved in ADITYA. All of the above mentioned experiments will be discussed in this paper.
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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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  • 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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  • Plasma production and preliminary results from the ADITYA Upgrade tokamak

    Tanna, R. L.   Ghosh, J.   Raj, Harshita   Kumar, Rohit   Aich, Suman   Ranjan, Vaibhav   Jadeja, K. A.   Patel, K. M.   Bhatt, S. B.   Sathyanarayana, K.   Chattopadhyay, P. K.   Makwana, M. N.   Shah, K. S.   Gupta, C. N.   Panchal, V. K.   Edappala, Praveenlal   Arambhadiya, Bharat   Shah, Minsha   Raulji, Vismay   Chowdhuri, M. B.   Banerjee, S.   Manchanda, R.   Raju, D.   Atrey, P. K.   Nagora, Umesh   Raval, J.   Joisa, Y. S.   Tahiliani, K.   Jha, S. K.   Gopalkrishana, M., V  

    The Ohmically heated circular limiter tokamak ADITYA (R-0 = 75 cm, a = 25 cm) has been upgraded to a tokamak named the ADITYA Upgrade (ADITYA-U) with an open divertor configuration with divertor plates. The main goal of ADITYA-U is to carry out dedicated experiments relevant for bigger fusion machines including ITER, such as the generation and control of runaway electrons, disruption prediction, and mitigation studies, along with an improvement in confinement with shaped plasma. The ADITYA tokamak was dismantled and the assembly of ADITYA-U was completed in March 2016. Integration of subsystems like data acquisition and remote operation along with plasma production and preliminary plasma characterization of ADITYA-U plasmas are presented in this paper.
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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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  • 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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  • New cerium-based metal-organic scintillators for radiation detection

    Boatner, L. A.   Neal, J. S.   Ramey, J. O.   Chakoumakos, B. C.   Custelcean, R.   van Loef, E. V. D.   Markosyan, G.   Shah, K. S.  

    We have previously shown that a new class of scintillating materials can be developed based on the synthesis and crystal growth of rare-earth metal-organic compounds. The first scintillator of this type consisted of single crystals of CeCl3(CH3OH)(4) that were grown from a methanol solution. These crystals were shown to be applicable to both gamma-ray and fast neutron detection. Subsequently, metal-organic scintillators consisting of the compound LaBr3(CH3OH)(4) activated with varying levels of Ce3+ and of CeBr3(CH3OH)(4) were grown in single crystal form. We have now extended the development of this new class of scintillators to more complex organic components by reacting rare-earth halides such as CeCl3 or CeBr3 with different isomers of propanol and butanol-including 1-propanol, isobutanol, n-butanol, and tert-butanol. The reaction of CeCl3 or CeBr3 with these organics results in the formation of new and relatively complex molecular crystals whose structures were determined using single-crystal X-ray diffraction. These new metal-organic scintillating materials were grown in single crystal form from solution, and their scintillation characteristics have been investigated using X-ray-excited luminescence plus energy spectra obtained with gamma-ray and alpha-particle sources. If the reactions between the inorganic and organic components are not carried out under very dry and highly controlled conditions, molecular structures will be formed that incorporate waters of hydration. The present observation of scintillation in these hydrated rare-earth metal-organic compounds is apparently an original finding, since we are not aware of any previous reports of scintillation being observed in a material that incorporates waters of hydration. (C) 2012 Elsevier B.V. All rights reserved.
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  • Bridgman bulk growth and scintillation measurements of SrI2:Eu2+

    Hawrami, R.   Glodo, J.   Shah, K. S.   Cherepy, N.   Payne, S.   Burger, A.   Boatner, L.  

    Large diameter Bridgman growth of europium activated strontium iodide SrI2:Eu2+ produces crystals with light yield of up to 115,000 ph/MeV with an excellent light yield proportionality. SrI2:Eu2+ exhibits an outstanding energy resolution of better than 3% FWHM at 662 keV. Its emission is centered at 435 nm. The scintillation decays with a 1 mu s time constant for small samples and up to 5 mu s to larger crystals. This paper presents successful progress made in the vertical Bridgman crystal growth of SrI2:Eu2+ and its scintillator properties. Large diameter, crack-free and transparent SrI2:Eu(2+)single crystals with diameters of 1 in., 1.3 in., 1.5 in. and 2 in. were all successfully grown. (c) 2013 Elsevier B.V. All rights reserved.
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  • Characterization of CMOS position sensitive solid-state photomultipliers

    McClish, M.   Dokhale, P.   Christian, J.   Johnson, E.   Stapels, C.   Robertson, R.   Shah, K. S.  

    We have designed position sensitive solid-state photomultipliers (PS-SSPM) using a complementary metal-oxide-semiconductor (CMOS) process While only needing four signal output channels to readout the device provides spatial information on the micro-pixel level Four variations of the PS-SSPM were fabricated however we only show the characterization results from two These two PS-SSPMs were characterized for their energy and coincidence timing resolution spatial resolution and scintillator array imaging Each PS-SSPM is 1 5 x 1 5 mm(2) however each device has different micro-pixel geometries and a different micro-pixel electrical readout for event position sensing The FWHM energy resolution at 511 keV was measured as a function of bias using a 1 x 1 x 20 mm(3) LYSO crystal The energy resolution was similar to 13-14% for both PS-SSPM designs The LYSO scintillator coincidence timing resolution was measured with results ranging from 2 1 to 1 0 ns between the two PS-SSPMs Spatial resolution studies were conducted using a focused (similar to 15 mu m beam spot diameter) pulsed 635 nm diode laser For each PS-SSPM its X and Y FWHM spatial resolution was measured to be 70 gm Lastly we demonstrate the PS-SSPM imaging capabilities using a LYSO scintillator array having 500 x 500 mu m(2) pixels (C) 2010 Elsevier B V All rights reserved
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  • Combined Off-pump Coronary Artery Bypass Grafting and Thyroidectomy

    Mehra, A. P.   Shah, K. S.   Jain, P. C.   Bhansali, S. K.   Sunawala, J. D.   Gandhi, B. V.   Oswal, A.   Karatela, R. A.  

    A 70-year-old Indian woman presented with an acute anterior wall myocardial infarction and a large multinodular goiter causing tracheal compression and dyspnea. Coronary artery angiography revealed severe triple-vessel disease, with an 80% occlusion of the left main stem, necessitating early coronary artery bypass grafting combined with total thyroidectomy. The procedure was performed successfully. At the 1-year follow- up, the patient remains euthyroid and in New York Heart Association functional class I. This case provides further evidence that combined coronary artery bypass grafting and total thyroidectomy is both feasible and safe. (Ann Thorac Surg 2009; 88: 661-3) (C) 2009 by The Society of Thoracic Surgeons
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  • New scintillator compositions - art. no. 670704

    Higgins, W. M.   Van Loef, E.   Glodo, J.   Churilov, A.   Shah, K. S.  

    Single crystals of LaBr3:1% Pr and CeBr3:1% Pr have been grown by the vertical Bridgman technique. Crystals of these scintillators can be used in the fabrication of gamma-ray spectrometers. The LaBr3:1% Pr and CeBr3:1% Pr crystals we have grown had light outputs of similar to 73,000 and similar to 50,000 photons/MeV, respectively, and principal decay constants of 11 mu s and 26 ns, respectively. There were a number of emission peaks observed for these compounds. The emission wavelength range for the LaBr3:1% Pr and CeBr3:1% Pr scintillators were from about 400 to 800 nm. The CeBr3:1% Pr scintillator had a dominating emission peak due to CeBr3 at 390 nm. These two materials had energy resolutions of 9 and 7% FWHM, respectively, for 662 keV photons at room temperature. In this paper, we will report on our results to date for vertical Bridgman crystal growth and characterization of Pr-doped LaBr3 and Pr-doped CeBr3 crystals. We will also describe the special handling and processing procedures developed for these scintillator compositions.
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  • Recent advances of planar silicon APD technology

    McClish, M.   Farrell, R.   Myers, R.   Olschner, F.   Entine, G.   Shah, K. S.  

    Radiation Monitoring Devices previously reported to have fabricated, using a planar processed, deep diffused silicon avalanche photodiodes (APDs) and position sensitive APDs (PSAPDs) that can be used for direct or scintillation-based spectroscopic and imaging applications. We have developed high gain (similar to 1000), high quantum efficiency (40-70% in the 200-900 nm region) at unity gain, relatively low noise, and magnetically insensitive APDs up to 45 cm(2) in area and PSAPDs up to 2.8 x 2.8 cm(2) in area. These detectors have begun to be implemented in applications such as positron emission tomography (PET) and single photon emission computerized tomography (SPECT) for medical imaging, high-energy physics experiments as water Cherenkov detectors and liquefied noble gas calorimeters, and receivers for long-range optical communication at near infrared (IR) wavelengths (1064 mu). Also, our PSAPDs have been combined with photocathode structures, similar to a photomultiplier tube (PMT), to fabricate hybrid devices. Here, we present a small review and a sample of results showing various applications utilizing our planar processed APDs and PSAPDs. (c) 2006 Elsevier B.V. All rights reserved.
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  • Betabox: a beta particle imaging system based on a position sensitive avalanche photodiode

    Dooraghi, A. A.   Vu, N. T.   Silverman, R. W.   Farrell, R.   Shah, K. S.   Wang, J.   Heath, J. R.   Chatziioannou, A. F.  

    A beta camera has been developed that allows planar imaging of the spatial and temporal distribution of beta particles using a 14 x 14 mm(2) position sensitive avalanche photodiode (PSAPD). This camera system, which we call Betabox, can be directly coupled to microfluidic chips designed for cell incubation or other biological applications. Betabox allows for imaging the cellular uptake of molecular imaging probes labeled with charged particle emitters such as F-18 inside these chips. In this work, we investigate the quantitative imaging capabilities of Betabox for F-18 beta particles, in terms of background rate, efficiency, spatial resolution, and count rate. Measurements of background and spatial resolution are considered both at room temperature (21 degrees C +/- 1 degrees C) and at an elevated operating temperature (37 degrees C +/- 1 degrees C), as is often required for biological assays. The background rate measured with a 4 keV energy cutoff is below 2 cph mm(-2) at both 21 and 37 degrees C. The absolute efficiency of Betabox for the detection of F-18 positron sources in contact with a PSAPD with the surface passivated from ambient light and damage is 46% +/- 1%. The lower detection limit is estimated using the Rose Criterion to be 0.2 cps mm(-2) for 1 min acquisitions and a 62 x 62 mu m(2) pixel size. The upper detection limit is approximately 21 000 cps. The spatial resolution at both 21 and 37 degrees C ranges from 0.4 mm FWHM at the center of the field of view (FOV), and degrades to 1 mm at a distance of 5 mm away from center yielding a useful FOV of approximately 10 x 10 mm(2). We also investigate the effects on spatial resolution and sensitivity that result from the use of a polymer based microfluidic chip. For these studies we place varying layers of low-density polyethylene (LDPE) between the detector and the source and find that the spatial resolution degrades by similar to 180 mu m for every 100 mu m of LDPE film. Sensitivity is reduced by half with the inclusion of similar to 200 mu m of additional LDPE film. Lastly, we demonstrate the practical utilization of Betabox, with an imaging test of its linearity, when coupled to a polydimethylsiloxane microfluidic chip designed for cell based assays.
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  • Latest Advances in Large Diameter SrI:Eu & CLYC:Ce Scintillators for Isotope Identification

    Hawrami, R.   Hines, C.   Abselem, I.   Biteman, V.   Vaghini, J.   Glodo, J.   And, P. O'Dougherty   Shah, K. S.   Cherepy, Nerine   Payne, Stephen   Burger, Arnold   Boatner, Lynn  

    Scintillator crystal detectors form the basis for many radiation detection devices. Therefore, a search for high light yield single crystal scintillators with improved energy resolution, large volume, and the potential for low cost, is an ongoing process that has increased in recent years due to a large demand in the area of nuclear isotope identification. Alkaline earth halides, elpasolites and rare earth halides are very interesting because many compositions from these crystal families provide efficient Ce3+/Eu2+ luminescence, good proportionality and good energy resolution. They also have small band-gap leading to higher light yields. Ce3+ and Eu2+ are efficient, and the emission wavelengths in the 350-500 nm region matches well with PMTs and a new generation of Si-photodiodes. In this presentation, we will the present progress made in the crystal growth of these compositions, and scintillator properties of large diameter SrI2:Eu2+ single transparent crystals. The crystals were grown successfully using the vertical Bridgeman technique. Crystals with different diameters of 1 '', 1.3 '', and 1.5 '' will be discussed. SrI2:Eu was discovered a half century ago, and was recently found to be an outstanding material for gamma ray-spectroscopy with high light yield, very good non-proportionality, and excellent energy resolution. We will also discuss growth and properties of larger Cs2LiYCl6 (CLYC) crystals. Recently, it has been shown that crystals from the elpasolite family, including CLYC, can be successfully employed for a dual gamma ray and neutron detection, which is possible with the help of pulse shape discrimination (PSD). PSD allows for recognition of an incident particle's nature based on the shape of the corresponding scintillation pulse. CLYC has the potential to minimize the cost and complexity of dual sensing gamma ray and neutron spectrometers. We also address progress in growth of CLYC crystals with large diameters (1 '' and 2 '') that are transparent and crack free.
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  • Characterization of X-Ray Imaging Properties of PbI2 Films

    Shah, K. S.   Bennett, P.   Cirignano, L.   Dmitriyev, Y.   Klugerman, M.   Mandal, K.   Moy, L. P.   Street, R. A.  

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  • Performance of Europium-Doped Strontium Iodide, Transparent Ceramics and Bismuth-loaded Polymer Scintillators

    Cherepy, N. J.   Payne, S. A.   Sturm, B. W.   O'Neal, S. P.   Seeley, Z. M.   Drury, O. B.   Haselhorst, L. K.   Rupert, B. L.   Sanner, R. D.   Thelin, P. A.   Fisher, S. E.   Hawrami, R.   Shah, K. S.   Burger, A.   Ramey, J. O.   Boatner, L. A.  

    Recently discovered scintillators for gamma ray spectroscopy - single-crystal SrI(2)(Eu), GYGAG(Ce) transparent ceramic and Bismuth-loaded plastics - offer resolution and fabrication advantages compared to commercial scintillators, such as NaI(Tl) and standard PVT plastic. Energy resolution at 662 keV of 2.7% is obtained with SrI2(Eu), while 4.5% is obtained with GYGAG(Ce). A new transparent ceramic scintillator for radiographic imaging systems, GLO(Eu), offers high light yield of 70,000 Photons/MeV, high stopping, and low radiation damage. Implementation of single-crystal SrI2(Eu), Gd-based transparent ceramics, and Bi-loaded plastic scintillators can advance the state-of-the art in ionizing radiation detection systems.
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