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Nuclear Science, IEEE Transactions on

Issue 5 • Date Oct 1991

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Displaying Results 1 - 11 of 11
  • New scintillation materials for fiber tracking and calorimetry

    Page(s): 994 - 998
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    Radiation damage studies were performed on new polystyrene-based plastic scintillators. Several samples of different multicomponent systems containing new fluorescent compounds were irradiated with a 60Co source to a 10 Mrad dose. After irradiation, the samples were annealed for ten days in oxygen and three days in air. Scintillation light output, fluorescence, and transmittance spectra were recorded at three different stages; before irradiation, immediately after irradiation, and after the annealing process. After irradiation and the annealing period, the light output of the best scintillators had decreased by 10% of their original values View full abstract»

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  • Theoretical prediction of the impact of Auger recombination on charge collection from an ion track

    Page(s): 999 - 1004
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    The theoretical analysis presented indicates that Auger recombination can reduce charge collection from very dense ion tracks in silicon devices. It is of marginal importance for tracks produced by 270-MeV krypton, and therefore it is of major importance for ions exhibiting a significantly larger loss. The analysis shows that recombination loss is profoundly affected by track diffusion. As the track diffuses, the density and recombination rate decrease so fast that the linear density (number of electron-hole pairs per unit length) approaches a nonzero limiting value as t→∞. Furthermore, the linear density very nearly equal to this limiting value is a few picoseconds or less. When Auger recombination accompanies charge transport processes that have much longer time scales, it can be simulated by assigning a reduced linear energy transfer to the ion View full abstract»

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  • Calibration measurements for the efficiency and response function of the NE213 scintillator by a 252Cf spontaneous fission source-application of a two-dimensional pulse height analysis system

    Page(s): 1040 - 1043
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    The authors describe calibration measurements for the efficiency and response function of the NE213 scintillator as an application of a two-dimensional pulse height analysis system. In this method, a 252 Cf spontaneous fission source with a continuous spectrum is employed by taking each fission event as a pulsed neutron source, and the efficiency and response function of the NE213 scintillator can be estimated by two-dimensional measurements of the time-of-flight spectrum (neutron energy spectrum) and pulse height spectrum View full abstract»

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  • Study of a photoelectron gun of high current with medium accelerating field

    Page(s): 1018 - 1025
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    A 352-MHz one-cell photocathode electron gun is studied. The simulations with PARMELA are done with two values of peak accelerating fields: 21 and 10 MV/m. Three cavity profiles are compared. The results are also discussed in view of the previous analytic theory. The space-charge effect with peak current greater than 300 A covers the RF effect. The beam qualities are not sensitive to cavity design View full abstract»

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  • Regulation of nuclear reactors by duplexed control rods: linearized analysis

    Page(s): 1044 - 1051
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    The dynamic behavior of a duplex control rod for a nuclear reactor is analyzed by linearized modeling. A simulation-aided design for this duplex, which has performance and safety characteristics that are better than those of conventional single control rods with the same stability margins, is reported View full abstract»

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  • Tuning magnet current-conditioning system for RF cavity in a high-intensity proton accelerator

    Page(s): 1005 - 1012
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    The development of a current-conditioning system for the tuning magnet of an RF cavity in a high-intensity proton accelerator is described. The conceived system has a bridge configuration consisting of a power amplifier, transistor switch, and power diodes. It works as a power amplifier during the acceleration period and recovers into the capacitor bank the inductive energy stored in the tuning magnet during the reset period. The system operation concept was verified by computer simulation, and the system design was based on the test results of a 1/100th scale model, which was built to evaluate the feasibility of hardware realization. The hardware system was built with commercially available components and tested in connection with a prototype RF cavity at the Los Alamos National Laboratory. This system can provide an accurate current waveform (low ripple), recover the inductive energy in the tuning magnet, and easily control the DC bias level View full abstract»

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  • Radiation and temperature survivability of multimode step-index fluorine-doped silica fibers

    Page(s): 985 - 993
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    In a search for optical fibers appropriate for long-term use in nuclear reactor instrumentation, effects of gamma radiation and high temperature on attenuation losses were investigated in three types of fiber. All of the fibers had silica cores with fluorine-doped silica cladding. Fibers with polyimide and aluminium coatings and uncoated fibers were tested. Samples were exposed to gamma radiation at dose rates ranging from 8.2 krad/h to 920 krad/h, with total doses up to 60 Mrad. The effects of heating the fibers, either concurrently with the radiation exposure or separately, were investigated. Heating irradiated fibers to 200°C generally reduced attenuation by annealing of radiation-induced defects. Higher temperatures caused rapid deterioration of fibers. A similar effect was observed when fibers were heated to above 200°C in the absence of radiation. Raising the temperature appears to suppress color centre formation, but beyond a threshold limit, higher temperatures result in jacket or cladding damage with net degradation View full abstract»

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  • Instrument failure detection and reconstruction methodology in space-time nuclear reactor dynamic systems with fixed in-core detectors

    Page(s): 1026 - 1034
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    The detection and isolation of instrument failures in nuclear reactors equipped with fixed in-core detectors were studied in order to improve reliability and safety. This was done by representing the reactor as a linear stochastic distributed parameter system. A bank of detection observers based on the Kalman filter concept was constructed in order to isolate component failures via robust observation. Each observer was sensitive to only one specified component failure. This was done to minimize the covariance matrix error. However, because observed deviations may be attributed to changes in system behavior, failure decisions are confirmed by a multiple consecutive miscomparison (MCM) counter. Following failure detection, the failed sensor's output is replaced with an estimate from the failure-free filter. Various simulations were performed to verify this failure detection method as applied to reactor instrument failures. It was demonstrated that the method can detect both single- and common-mode failures. Also, without hardware redundancy, it can describe the system dynamics in the event of failures View full abstract»

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  • System complexity measure in the aspect of operational difficulty

    Page(s): 1035 - 1039
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    The complexity of a system arises not only due to the number of components and the characteristics of each component, but also to the types of interconnections between the components. A method of measuring this structural complexity is suggested as reflected in system operational difficulty using an information theoretic approach. This method, the functional entropy measure, can denote the structural complexity induced from the interconnections between components. An equation for calculating the diagnostic entropy without introducing any approximation is derived. The role of monitoring instruments is also studied, and the results show that the monitoring of a system not only can reduce, but also can increase the entropy of the system. To know the true condition of a monitored system with far greater confidence than if it remains unmonitored, the monitoring instrument must be much more reliable than the monitored component View full abstract»

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  • Effects of neutron irradiation on current gain and noise in silicon avalanche photodiodes

    Page(s): 1013 - 1017
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    The authors report on an experimental study of the effects of fission neutron irradiation on a silicon avalanche photodiode, which is a photodetector that is often used as the front end of a receiver in a fiber-optic link. Measurements indicate that there is a degradation in the current gain and a decrease in the multiplication noise after irradiation. Some recovery is found to occur after three days. The device, however, continues to behave linearly after irradiation View full abstract»

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  • Comparison of the timing properties of the new Philips components (Amperex) XP2020/UR photomultiplier and the XP2020 photomultiplier

    Page(s): 1052 - 1056
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    Timing characteristics are measured for the Philips Components (Amperex) XP2020/UR photomultiplier. The transit time jitter is significantly better than that of previously available XP2020 tubes. In a study of the transit time jitter, a single photoelectron resolution of 286±3 ps was obtained for the XP2020 and 190±2 ps for the XP2020/UR View full abstract»

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Aims & Scope

IEEE Transactions on Nuclear Science focuses on all aspects of the theory and applications of nuclear science and engineering, including instrumentation for the detection and measurement of ionizing radiation; particle accelerators and their controls; nuclear medicine and its application; effects of radiation on materials, components, and systems; reactor instrumentation and controls; and measurement of radiation in space.

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