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Nuclear Science, IEEE Transactions on

Issue 5 • Date Oct 1988

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Displaying Results 1 - 8 of 8
  • Characteristics of GaAs MESFET inverters exposed to high energy neutrons

    Page(s): 1074 - 1079
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    GaAs MESFET circuits were exposed to high-energy neutrons with fluences ranging from 1×1014 n/cm2 to 2×1015 n/cm2. The reflections of discrete transistors, inverters, and ring oscillators were characterized at each fluence. While the MESFETs exhibit significant threshold voltage shifts and transconductance and saturation current degradation over this range of neutron fluences, an improvement in the DC characteristics of Schottky diode FET logic (SDFL) inverters was observed. This unusual result has been successfully simulated using device parameters extracted from FETs damaged by exposure to high-energy neutrons. Although the decrease in device transconductance results in an increase in inverter gate delay as reflected in ring oscillator frequency measurements, it is concluded that GaAs ICs fabricated from this logic family will remain functional after exposure to extreme neutron fluences. This is a consequence of the observed improvement in inverter noise margin evident in both measured and simulated circuit performance View full abstract»

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  • On the application of singular perturbation techniques to nuclear engineering control problems

    Page(s): 1080 - 1085
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    Using a linear state regulator problem for the control of xenon-induced spatial flux oscillations in a nuclear reactor it is shown that model simplifications may cause the system equations to behave like singularly perturbed ones. An example illustrates that an attempt to transform the system equations to standard singular perturbation form also transforms the performance index and raises the possibility of cheap control, which is physically not possible with mechanical control systems in a nuclear reactor. Another example demonstrates that the stiffness of the system equations is improved dramatically by making the model less approximate. It is concluded that care must, therefore, be exercised while applying singular perturbation techniques to problems which are ill-conditioned as a result of model simplification View full abstract»

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  • Target and X-ray detector considerations in low-duty and intense pulse electro-channeling experiments

    Page(s): 1086 - 1087
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    The use of the Stanford Mark III electron accelerator presents special difficulties for channeling experiments due to its low-duty factor pulses. To compensate for the low-duty cycle of the channeled electron beam, the author utilized the high average current generated by the accelerator and analyzed the X-ray output using a turnable X-ray monochromator and a semiconductor detector operating in the current mode, rather than in the normal pulse mode. Cooling of the specimen was achieved by using a copper cooling rod to remove the dissipation of 10 W into a liquid nitrogen heat sink. The nonlinear efficiency of the monochromator over its full range of 5-30 keV was compensated by controlling the scanning rotation speed using a minicomputer-controlled stepping motor View full abstract»

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  • Nonlinear ADC with digitally selectable quantizing characteristic

    Page(s): 1088 - 1091
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    A method is presented for generating linear or nonlinear functions digitally. The nonlinear analog-to-digital conversation (NLADC) is accomplished using the pulsewidth modulation of the analog input voltage. The conversion is done accordingly to a special quantizing characteristic function (QCF), which depends on the specific application. This special QCF, sampled, quantized, and coded, has been stored in an EPROM (erasable programmable read-only memory). The quantizing characteristic can be any monotonically increasing function of any type, resulting in a very flexible linear or nonlinear analog-to-digital converter. Such an NLADC could be used for the expansion or compression of the dynamic range in nuclear science measurements or in robotics for code modulation planning View full abstract»

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  • The manipulation of time-varying dynamic variables using the rule modification method and performance-index in NPP accident diagnostic expert systems

    Page(s): 1121 - 1125
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    When an expert system is being developed for nuclear power plant (NPP) accident diagnosis, the most difficult problem is the manipulation of the time-varying dynamic variables. To meet this need, the authors propose modification of the rules for accident diagnosis when plant parameters and conditions are varying. In addition to the rule-modification method, a pattern-matching method using the performance index is suggested. This system also uses the results of transient analysis and accident analysis codes as a database. To simulate this expert system, PROLOG was used to construct the knowledge base. The inherent backtracking inference strategy was used for the inference engine. Feedwater line piping failure was selected for system verification View full abstract»

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  • Resonant power supplies for a rapid-cycling accelerator

    Page(s): 1092 - 1098
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    A resonant power supply has been proposed as an efficient power supply for a future 60-GeV, Kaon-producing accelerator. The engineering design of the electric system of the main-ring power supplies is described. It is shown that the resonant power supply can be built with standard commercially available components. The most critical component is the bypass switch, which requires gate-turn off thyristors, connected in parallel. Standard metal-clad switchgear can be used for the AC system. The resonant power supplies can be fed directly from the 115-kV utility network, but the resonance power supplies draw pulse loads from the utility network. This pulse may produce disturbances. AC filter and reactive power compensation is needed for economical operation View full abstract»

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  • Time-resolved thermal annealing of interface traps in aluminium gate-silicon oxide-silicon devices

    Page(s): 1113 - 1120
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    The anneal kinetics of interface traps in aluminium gate-silicon oxide-silicon structures has been studied using capacitance-voltage measurements. The capacitors were annealed in forming gaps at temperatures ranging from 250°C to 620°C. AN exponential decay of the trap density with annealing time has been observed. The curve of the equilibrium value of trap density obtained after long annealing times versus temperature shows a U-shaped form with a minimum located near 450°C. A model based on the bimolecular reaction theory is proposed to explain the results obtained View full abstract»

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  • High-temperature silicon-on-insulator electronics for space nuclear power systems: requirements and feasibility

    Page(s): 1099 - 1112
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    The authors performed a study to determine whether silicon very large-scale integrated circuits (VLSICs) can survive the high temperature (up to 300° C) and total-dose radiation environments (up to 10 Mrad over a 7-10-y system life) projected for a very-high power space nuclear reactor platform. It is shown that circuits built on bulk epitaxial silicon cannot meet the temperature requirement because of excessive junction leakage currents. However, circuits built on silicon-on-insulator (SOI) material can meet both the radiation and temperature requirements. It is also found that the temperature dependence of the threshold voltage of the SOI transistors is less than that of bulk transistors. Survivability of high-temperature SOI VLSICs in space, including immunity to transient and single-event upset, is also addressed 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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