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  • Articles  (1,233)
  • 2010-2014  (1,233)
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  • Articles  (1,233)
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  • 1
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    The effect of interface trapped charge on threshold voltage shift estimation for Gamma irradiated MOS device (2014)
    Elsevier
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    Publication Date: 2014-12-29
    Description: Publication date: Available online 16 December 2014 Source: Radiation Measurements Author(s): H. Jafari , S.A.H. Feghhi , S. Boorboor The ionizing radiation affects the silicon-based electronic devices and leads to the build-up of trapped hole in the oxide and an increase in trap density at the Si-SiO 2 interface. These defects cause degradation of device parameters such as threshold voltage shifts, sub-threshold swing and etc. Although the effect of oxide charges on the threshold voltage shift in MOS devices is dominant, accurate estimation requires for modeling of the interface trapped charge effect. In this work, the effect of interface trapped charge on threshold voltage shift in an N-channel MOS transistor device, irradiated at different total ionization doses, was estimated considering proton transport model in gate oxide. The analytical model calculations consider the time dependent buildup of trapped holes and interface trap charges. Furthermore, we used ATLAS as a numerical semiconductor simulation code which only allows modeling oxide trapped charge to calculate the variation of threshold voltage shift with TID without considering the interface trap. Computational results were compared with experimental results at several doses and gate biases. According to the experimental results, ATLAS overestimates threshold voltage shift within 30% approximately. The results based on considering proton transport mechanism in analytical model, showed significantly better agreement with experimental results for total dose level up to 2.87 krad at several different biases. Overall results indicated that considering interface trap charges modeling, substantially improves the accuracy of the threshold voltage shift estimation.
    Print ISSN: 1350-4487
    Electronic ISSN: 1879-0925
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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  • 2
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    GM counter deadtime dependence on applied voltage, operating temperature and fatigue (2014)
    Elsevier
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    Publication Date: 2014-12-29
    Description: Publication date: February 2015 Source: Radiation Measurements, Volume 73 Author(s): T. Akyurek , M. Yousaf , X. Liu , S. Usman This paper utilized standard two-source method and the simple non-paralyzing model assumption to examine a GM counter's deadtime dependence on applied voltage, operating temperature, and fatigue. Both 60 Co and 137 Cs sources were used for deadtime measurements. The results gathered suggest the presence of three distinct regions of deadtime behavior. At low voltages, the deadtime decreases as the voltage increases (Region I) followed by a region of stable deadtime plateau (Region II) and finally a region of increasing deadtime with increasing voltage. Region II is the best region for operating with a minimum deadtime which is not sensitive to the applied voltage. Typical deadtime values for GM counters were between 100 and 300 μs; the deadtime values in Region II were within this range. The results examined in this study also indicate a strong temperature dependence of deadtime, with a correlation coefficient of 0.93. The GM counter deadtime for various fatigues (aging) were investigated for three fatigue levels with a correlation coefficient of 0.48. The experimental results confirm that deadtime increases as both temperature and fatigue increase. The fundamental nature of deadtime seems to be different for voltages lower than the stable deadtime plateau (Region II) and for voltages higher than the plateau.
    Print ISSN: 1350-4487
    Electronic ISSN: 1879-0925
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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  • 3
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    Welcome Address from ISSDO (2014)
    Elsevier
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    Publication Date: 2014-12-29
    Description: Publication date: December 2014 Source: Radiation Measurements, Volume 71
    Print ISSN: 1350-4487
    Electronic ISSN: 1879-0925
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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  • 4
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    Monte Carlo simulations of TL and OSL in nanodosimetric materials and feldspars (2014)
    Elsevier
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    Publication Date: 2014-12-29
    Description: Publication date: Available online 19 December 2014 Source: Radiation Measurements Author(s): Vasilis Pagonis , Reuven Chen The study of luminescent materials consisting of nanoclusters is an increasingly active research area. It has been shown that the physical properties of such nanodosimetric materials can be very different from those of similar conventional microcrystalline phosphors. In addition, it has been suggested that traditional energy band models may not be applicable for some of these nanodosimetric materials, because of the existence of strong spatial correlations between traps and recombination centers. The properties of such spatially correlated materials have been previously simulated by using Monte Carlo techniques and by considering the allowed transitions of charge carriers between the conduction band, electron traps and recombination centers. This previous research demonstrated successfully the effect of trap clustering on the kinetics of charge carriers in a solid, and showed that trap clustering can significantly change the observed luminescence properties. This paper presents a simplified method of carrying out Monte Carlo simulations for thermoluminescence (TL) and optically stimulated luminescence (OSL) phenomena, based on a recently published model for feldspar. This model is based on tunneling recombination processes involving localized near-neighbor transitions. The simulations show that the presence of small clusters consisting of a few traps can lead to multiple peaks in both the TL and linearly modulated OSL signals. The effects of donor charge density, initial trap filling and cluster size are simulated for such multi-peak luminescence signals, and insight is obtained into the mechanism producing these peaks.
    Print ISSN: 1350-4487
    Electronic ISSN: 1879-0925
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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  • 5
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    Diamond sensor arrays for neutron detection: Preamplifier signal dependence on sensor array configuration (2014)
    Elsevier
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    Publication Date: 2014-12-29
    Description: Publication date: February 2015 Source: Radiation Measurements, Volume 73 Author(s): Eric Lukosi , Mark Prelas Experimental verification of simulated results of series and parallel diamond detector arrays is reported. Eight commercially available electronic grade single crystal CVD diamond plates were used in series and parallel array configurations and were characterized through alpha particle and neutron exposures. It was found that a series array of diamond detectors is inherently limited due to the impedances of the diamond plates. Plutonium–beryllium neutron exposures were conducted with each of these diamond plates and on a parallel array of all eight diamond plates. It was found that the detection efficiency scaled linearly with the number of plates and that the pulse height from the preamplifier was not affected by the parallel array configuration. However, the additional capacitance introduced to the charge sensitive preamplifier indicates that there is a limitation to the total size that can be realized with a parallel diamond sensor array before significant signal degradation occurs.
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    Electronic ISSN: 1879-0925
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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  • 6
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    Energy dependency of a water-equivalent fibre-coupled beryllium oxide (BeO) dosimetry system (2014)
    Elsevier
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    Publication Date: 2014-12-08
    Description: Publication date: Available online 6 December 2014 Source: Radiation Measurements Author(s): Alexandre M. Caraça Santos , Mohammad Mohammadi , Shahraam Afshar V Here we investigate the energy dependency of the radioluminescence (RL) and optically stimulated luminescence (OSL) of near water equivalent beryllium oxide (BeO) ceramics. The BeO ceramic is coupled to an optical fibre. We investigate the water equivalence of BeO ceramics by comparing the mass attenuation coefficients and mass stopping powers of BeO ceramic to those of water. We also compare the results to other common dosimeter materials; polyvinyl toluene (PVT) based plastic scintillators, lithium fluoride (LiF) and aluminium oxide (Al 2 O 3 :C). Results show that while PVT based plastic scintillators are the most water equivalent material investigated, the mass attenuation coefficients and mass stopping power ratios of BeO and water vary the least with energy. We also investigate the x-ray energy dependence of BeO ceramic for a range of energies produced by a superficial x-ray unit (SXR), an Iridium-192 source and a high energy linear accelerator. Results indicate a significant under response of the BeO ceramic RL and OSL signals for lower x-ray energies, up to 55% for the lower SXR beams. The RL signal from BeO ceramics shows a constant response for x-ray energies above a 50kVp SXR beam.
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    Electronic ISSN: 1879-0925
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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  • 7
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    Study of “A method to enhance coincidence time resolution with applications for medical imaging systems (TOF/PET)” (2014)
    Elsevier
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    Publication Date: 2014-12-07
    Description: Publication date: Available online 5 December 2014 Source: Radiation Measurements Author(s): I. Bikit , D. Mrdja , K. Bikit , J. Slivka , S. Forkapic The physics of true coincidence production by the Cs-137 source is elaborated. When the single-photon emitting Cs-137 source is sandwiched between two detectors of a coincidence system, the scattering of 662 keV gamma-rays between the detectors (“cross-talk”) will result in true coincidence events. The results of Ermis et al. (2014) on that issue are critically analyzed. Our Geant-4 simulations did not support most of the results of this work. Thus, the possibility of coincidence time resolution improvement by the Cs-137 source is challenged.
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    Electronic ISSN: 1879-0925
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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  • 8
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    Luminescent properties of a reddish orange long afterglow phosphor SrSnO3:Sm3+ (2014)
    Elsevier
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    Publication Date: 2014-12-07
    Description: Publication date: Available online 5 December 2014 Source: Radiation Measurements Author(s): Tao Wang , Yihua Hu , Li Chen , Xiaojuan Wang , Guifang Ju SrSnO 3 :Sm 3+ persistent phosphor was successfully prepared by high temperature solid-state reaction method. The persistent phosphor was systematically studied by XRD, diffuse reflectance, photoluminescence (PL), persistent luminescence and thermoluminescence (TL) spectra. When irradiated by 254nm ultraviolet light in advance, this phosphor shows a red-orange persistent luminescence dominated at ∼596nm at room temperature. The dependence of Sm 3+ contents on the PL and persistent luminescence properties were investigated. The TL and potential afterglow mechanism of the SrSnO 3 :Sm 3+ phosphor was also discussed in this paper.
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    Electronic ISSN: 1879-0925
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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  • 9
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    Dose response and fading studies on de-proteinated tooth enamel after de-convolution using the sum of general order kinetics and a component for tunnelling recombination (2014)
    Elsevier
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    Publication Date: 2014-12-05
    Description: Publication date: Available online 4 December 2014 Source: Radiation Measurements Author(s): Niyazi Meriç , Ülkü Rabia Yüce , Eren Şahiner , Aristis Damianidis , George S. Polymeris The present study reports on the results of dose response and fading for the case of blue stimulated OSL signals from tooth enamel samples. These samples have been previously subjected to two different de-proteinization procedures, after applying hydrazine and sodium hydroxide. The OSL signal, when quantified based on the conventional way of OSL analysis, namely the use of the initial 5 seconds of the signal minus the intensity of the last 5 seconds as a background signal, yields bad signal to noise ratio as well as instability. The application of the de-convolution procedure including two components, one of general order kinetics and one of tunneling recombination results to a fast OSL component with enhanced signal to noise ratio, isolating thus the fading component and yielding a linear dose response throughout the entire dose range of the present study. Finally, the physical meaningfulness of the fitting parameters for the tunneling component, especially the dimensionless parameter representing the normalized donor–acceptor density ρ’ is also discussed.
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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  • 10
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    Undoped poly (phenyl sulfone) for radiation detection (2014)
    Elsevier
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    Publication Date: 2014-12-04
    Description: Publication date: Available online 2 December 2014 Source: Radiation Measurements Author(s): Hidehito Nakamura , Yoshiyuki Shirakawa , Nobuhiro Sato , Hisashi Kitamura , Sentaro Takahashi Undoped aromatic ring polymers are potential scintillation materials. Here, we characterise poly (phenyl sulfone) (PPSU) for radiation detection. The amber-coloured transparent resin emits bluish-white fluorescence with 390-nm maximum. It has an excitation maximum of 340 nm, and has a density of 1.29 g/cm 3 . The effective refractive index based on its emission spectrum is 1.75. The light yield is almost equal to that of poly (ethylene terephthalate), which is a transparent resin. These results demonstrate that PPSU can be used as a component substrate in polymer blends for altering optical characteristics.
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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