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Nuclear Science, IEEE Transactions on

Issue 6  Part 2 • Date Dec 1990

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Displaying Results 1 - 16 of 16
  • A workplace air monitor for uranium particulate detection

    Page(s): 2165 - 2170
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (388 KB)  

    An air monitor has been developed at the Oak Ridge Y-12 Plant to sample the air in enriched uranium processing areas and to detect elevated particulate concentrations due to an upset condition. The monitor measures the alpha particle activity from material collected on 47-mm filter paper. Three energy windows are used to allow quantification of background activity from radon and thoron daughters and correction of their spillage into the uranium window. There is sufficient monitor memory to hold a history file of six days' activity from three sampling heads at 20-min status intervals. Alarm signals are activated if the absolute level of activity on a filter exceeds a predefined level, or if an excessively fast rate of buildup is occurring, which would cause the absolute level to be exceeded. This monitor is combined with an absolute particle counter, and data are collected at a processing station where uranium dust is known to be present. The occurrence of high particle count activity in the 3.0-10.0- mu m range is followed by increased alpha activity on the filter paper. View full abstract»

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  • Differential displacement kerma cross sections for neutron interactions in Si and GaAs

    Page(s): 2219 - 2228
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (892 KB)  

    The cross-section processing code NJOY has been modified to calculate flux-averaged partially integrated differential displacement kerma cross sections or displacement kerma matrix elements for neutron interactions. These, along with total displacement kerma cross sections, have been calculated using ENDF/B-V and ENDL-84 data files for Si, Ga, and As. These displacement kerma matrices for Si and GaAs allow calculations of the distribution of displacement energy between displacement cascades. The tabulation of kerma cross sections for Si constitutes a complete revision of the data used in current standard practices. Another contribution is the tabulated kerma cross sections for GaAs. View full abstract»

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  • A four-channel ADC on a VME board

    Page(s): 2185 - 2187
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (204 KB)  

    A four-channel analog-to-digital converter (ADC) for data acquisition in nuclear physics experiments has been developed on a VME board. The circuit architecture is a multistretcher configuration based on a fast conversion module. The board can operate either in sampling or in autotrigger mode with an input range of 4.096 or 8.192 V; the risetime protection can vary from 1 to 32 mu s. Many functions are software selectable; the most significant are: the linear gate trigger mode, the risetime protection, and the ability to set of the low and high thresholds independently for each channel. The conversion module is based on a two-step concept: an overall resolution of 12 b, with a conversion time lower than 1 mu s, is obtained by means of two 8-b flash ADCs and a sliding-scale compensation technique is used to improve the differential linearity. The differential linearity error is less than 1%, while the integral linearity error is 0.023% over the 98% of the dynamic range. View full abstract»

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  • Statistical uncertainties of elemental concentrations extracted from neutron-induced gamma-ray measurements

    Page(s): 2175 - 2178
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (364 KB)  

    The uncertainties in elemental concentrations obtained from borehole thermal neutron capture measurements have been determined, when the normalization to absolute concentrations is by an associated element closure model that accounts for unmeasured elements in the rock. Typical uncertainties under normal logging conditions are between 2 and 3 wt.% for Ca and Si, an little over 1 wt.% for S, a few tenths of a weight percent for Fe and Ti, and about 0.2 p.p.m. for Gd. Adverse geophysical effects, large effective tool standoff, and large borehole thermal neutron absorption cross section increase the elemental concentration uncertainties because of an increase in the number of borehole gamma rays detected. Acceptable uncertainties can be obtained by slower logging speed or multiple passes. Regardless of geophysical parameter values, correct elemental concentrations are obtained within the measurement statistics. View full abstract»

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  • First-level trigger processor for the ZEUS calorimeter

    Page(s): 2198 - 2202
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (448 KB)  

    The design of the first-level trigger processor for the ZEUS calorimeter is discussed. This processor accepts data from the 13000 photomultipliers of the calorimeter, which is topologically divided into 16 regions, and after regional preprocessing performs logical and numerical operations that cross regional boundaries. Because the crossing period at a HERA collider is 96 ns, it is necessary that first-level trigger decisions be made in pipelined hardware. One microsecond is allowed for the processor to perform the required logical and numerical operations, during which time the data from ten crossings would be resident in the processor while being clocked through the pipelined hardware. The circuitry is implemented in 100 K emitter-coupled logic (ECL), advanced CMOS discrete devices and programmable gate arrays, and it operates in a VME environment. All tables and registers are written/read from VME, and all diagnostic codes are executed from VME. Preprocessed data flow into the processor at a rate of 5.2 GB/s, and processed data flow from the processor to the global first-level trigger at a rate of 700 MB/s. The system allows for subsets of the logic to be configured by software and for various important variables to be histogrammed as they flow through the processor. View full abstract»

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  • Data acquisition for the Zeus central tracking detector

    Page(s): 2161 - 2164
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (356 KB)  

    The transputer-based data acquisition system for the Zeus central tracking detector is described. The Zeus experiment is being installed on the Hera electron-proton collider being built at the Desy laboratory in Hamburg. The high-beam crossover rate of the Hera machine will provide experience in data acquisition and triggering relevant to the environment of future accelerators. The front-end data acquisition system, the crate readout system, and the system readout are described. The readout controller is discussed. The current status and future developments are outlined for this architecture. View full abstract»

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  • Enhanced core flow measurement in the advanced boiling water reactor

    Page(s): 2208 - 2213
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (524 KB)  

    A method for the accurate measurement of core flow required to support several critical control and safeguard functions for the advanced boiling water reactor (ABWR) is described. The ABWR incorporates reactor internal pumps for reactor coolant recirculation. An adaptive measurement method has been adopted. It combines core support plate differential pressure and neutron flux measurements to derive core flow. A steady-state heat balance calculation is combined with other process measurements to obtain an accurate calibration reference for the adaptive cores flow measurement method. The uncertainty of the core flow estimate calculated from core plate differential pressure measurements can be substantially reduced by incorporating the core power adjustment and the improved calibration method described. Use of these enhancements can result in a core flow measurement system that satisfies the accuracy requirements of all the critical ABWR control and safeguard functions. View full abstract»

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  • Development of a personal-computer-based system for control rod worth determination in a nuclear reactor

    Page(s): 2149 - 2155
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (476 KB)  

    A new and compact system based on a personal computer is developed for online determination of control rod worth in the upgraded 10-MW core of the Pakistan Research Reactor (PARR-1). The system utilizes a locally designed pulse acquisition card interfaced with the PC that features multiple inputs, high signal resolution, and fast data acquisition in a single slot card. The system acquires the pulse signals from the start-up channels and computes the system negative reactivity along with the associated errors using the inverse kinetic rod drop algorithm. The effect on reactivity measurements of relative detector position on the core is discussed. The results of rod worth measurements under different core conditions on the PARR-1 and PARR-2 cores are described. The application of the system for reactivity determination in the case of a highly subcritical core and large gamma background is discussed. View full abstract»

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  • Detection of gamma rays using a coupled array of high-purity germanium detectors

    Page(s): 2203 - 2207
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (684 KB)  

    The characteristics of a seven-element hexagonal close-packed array of high-purity germanium detectors were measured. The energy resolution or full width at half maximum (FWHM) and full width at 10% maximum (FW.1M) were measured in both the uncoupled mode and the sum-coincidence mode between 333 keV and 2.612 MeV. The fractional peak efficiency improvement obtained in sum-coincidence mode compared with the uncoupled mode increased from 0% at 80 keV to 19.7% at 2.612 MeV. A Monte Carlo code developed to compare these results with theoretical models shows substantial agreement with experiments from 80 keV to 1.332 MeV. A description of the detector, signal processing electronics, data acquisition system, and software is given. A technique based on real-time compensation of gain and offset drift is developed to minimize the peak broadening in real-time sum-coincidence spectra. This technique allows data acquisition to commence shortly after turn-on while the system approaches temperature stabilization. View full abstract»

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  • A review of the data acquisition electronics for the ISIS spallation neutron source

    Page(s): 2156 - 2160
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (424 KB)  

    The existing data acquisition system and its design concepts are reviewed for the ISIS facility at Rutherford Appleton Laboratory. The focus is on data acquisition electronics for the ISIS facility. Current developments, including the transputer memory module and the data acquisition snapshot histogrammer (DASH) system, are discussed. Areas where there is a need for further development of the data acquisition electronics are identified. The conceptual design for the current data acquisition electronics started in 1980. The major future project will be a completely new design to accommodate developments of the ISIS facility over the next decade. These future developments are outlined. View full abstract»

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  • Magnetic Septa For The Saskatchewan Accelerator Laboratory (SAL)

    Page(s): 2171 - 2174
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (360 KB)  

    An unusual design was investigated for two magnets now in permanent use at the Saskatchewan Accelerator Laboratory (SAL). The compact septa incorporated a novel cooling technique for the thin aluminum sheets forming the coils. These magnets have operated successfully for several years. Concepts for improviing the duty factor and peak field of the septa by using power modulators were considered. View full abstract»

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  • An EXELFS multiscaler DMA interface for the IBM-PC-AT using programmable gate arrays

    Page(s): 2191 - 2197
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (527 KB)  

    An IBM PC-AT interface for data acquisition from diode arrays is described. It was developed for use in an extended energy loss fine structure (EXELFS) spectrometer, where sometimes two diode arrays (containing EXELFS and low-loss spectra) need simultaneous scanning. The system operates as a multiscaler, allowing two processes to be recorded at the same time. The interfaice was designed using a programmable gate array (an 1800 gate-equivalent logic cell array from XILINX) to implement most of the digital circuitry and a 12-bit ADC to sample the analog inputs. A 12-bit DAC was used for analog outputs and for diagnostic testing purposes. The interfaice hardware was given a general design so that it may be used in other e,imilar applications. View full abstract»

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  • Advances in the development of encapsulant for mercuric iodide x-ray detectors

    Page(s): 2214 - 2218
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (575 KB)  

    Advances in the development of protective impermeable encapsulants with high transparency to ultra-low-energy X-rays for use on HgI, X-ray detectors are reported. Various X-ray fluorescence spectra from coated detectors are presented. The X-ray absorption in the encapsulants has been analyzed using characteristic radiation from various elements. Results suggest that low-energy cutoffs for the detectors are not determined solely by the encapsulating coatings presently employed but are also influenced by the front electrode and surface effects, which can affect the local electric field or the surface recombination velocity. An energy resolution of 182 eV (FWHM) has been achieved for Ni L lines at 850 eV. Improved detector sensitivity to X-ray energies under 700 eV is demonstrated. View full abstract»

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  • 1990 Index IEEE Transactions on Nuclear Science Vol. 37

    Page(s): 1 - 31
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    Freely Available from IEEE
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