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Nuclear Science, IEEE Transactions on

Issue 4  Part 1-2 • Date Aug. 1993

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Displaying Results 1 - 25 of 166
  • Performance of the SLD barrels CRID during the 1992 physics data run

    Publication Year: 1993 , Page(s): 589 - 592
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (346 KB)  

    The SLD is an e/sup +/e/sup -/ spectrometer designed for Z/sup 0/ physics. The SLD Cherenkov Ring Imaging Detector (CRID) has been designed to provide charged particle identification that allows pi /K/p separation up to 30 GeV/c and e/ pi separation up to 6 GeV/c. The detector was fully operational in the 1992 physics data run. The electron drift velocity and magnetic field deflection of electron trajectories have been measured. Cherenkov rings have been observed from both the liquid and gas radiators. The number and the resolution of the angle of Cherenkov photons have been determined to be approximately equal to design specifications.<> View full abstract»

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  • A ring Compton scatter camera for imaging medium energy gamma rays

    Publication Year: 1993 , Page(s): 972 - 978
    Cited by:  Papers (23)  |  Patents (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (436 KB)  

    The characteristics of a new ring Compton scatter camera are described. This camera is designed to image medium energy (0.5 to 3 MeV) gamma-ray fields. It consists of two positron sensitive detector arrays, i.e. a 4×4 planar array of high purity germanium (HPGe) crystals and a ring array of up to 64 NaI(Tl) crystals. Past evaluations of Compton cameras have employed a planar second detector, which is subjected to a large flux of gamma rays that either pass directly through or undergo small angle scatter in the first detector. A ring array significantly reduces direct and small angle scattered events in the second detector. An analytical model for ring camera systems is developed to predict angular resolution and efficiency, and is benchmarked against measurements made with a prototype system consisting of the 4×4 HPGe array and an eight-element ring. Predictions are made for a system with 64 crystals in the second detector ring View full abstract»

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  • Compressed xenon gas near its critical point as an ionization medium

    Publication Year: 1993 , Page(s): 642 - 644
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (268 KB)  

    The properties of compressed xenon gas near its critical point as an ionization medium are studied. The authors' data suggest that xenon near it critical point is an important addition to the presently available high resolution radiation detector media. Both the ability to drift ionization electrons over large distances without attenuation and stability with time are demonstrated. The energy resolution of the 976/keV K-conversion electron peak of 207Bi is measured to be 20 keV full-width half-maximum (FWHM) in 1.4 g/cm3 (62 atm) of xenon, independent of the distance over which the charge drifts View full abstract»

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  • Temperature dependence of radiation damage and its annealing in silicon detectors

    Publication Year: 1993 , Page(s): 344 - 348
    Cited by:  Papers (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (304 KB)  

    The radiation damage resulting from the large particle fluences predicted at the Superconducting Super Collider induces significant leakage currents in Si detectors. In order to limit these currents, the detectors are operated at reduced temperatures (~0°C). Results are presented of a study of temperature effects on both the initial radiation damage and the long-term annealing of that damage in Si PIN detectors. Depletion voltage results are reported. The detectors are exposed to approximately 1014/cm2 650-MeV protons. Very pronounced temperature dependences are observed View full abstract»

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  • Effect of lead filters on the performance of a neuro-PET tomograph operated without septa

    Publication Year: 1993 , Page(s): 1087 - 1091
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (324 KB)  

    The value of using lead filters to improve the quality of positron emission tomography (PET) data is investigated for a brain scanner operated without septa. The filters consist of sheets of thickness 0.5 mm and 1.0 mm and axial width 18 cm which are placed around the outer surface of the patient port. The port diameter is 35 cm and the axial field of view (FOV) is 10.65 cm. The ratios of dead times (with/without filter) with 1 mCi (20 cm uniform cylinder) in the FOV are 0.92 (0.5 mm) and 0.82 (1 mm) at a lower threshold (LLD) of 380 keV; the values at 150 keV are 0.87 and 0.76. Randoms rates are reduced by 12% (0.5 mm) and 27% (1 mm) at a LLD of 380 keV, and by 20% and 40% at 150 keV. These values reflect the significant reduction of lower energy events observed in the measured energy spectrum. These reductions are accompanied by a drop in the true coincidence rate such that the noise equivalent count (NEC) is reduced for count rates up to the maximum measured trues rate at lower thresholds of 380 keV and 150 keV. It is concluded that the filters used in this study provide no advantage in the performance of the tomograph View full abstract»

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  • Imaging of radionuclide emissions with a low-noise charge-coupled device

    Publication Year: 1993 , Page(s): 979 - 982
    Cited by:  Papers (8)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (396 KB)  

    The adaptation of a cooled charged-coupled device (CCD) for some autoradiographic applications which may alleviate some of the problems encountered with film is investigated. The proposed approach uses a scientific-grade CCD which is optically coupled via a lens to a scintillator without intermediate amplification. On the basis of experience with lens coupling, the performance of the CCD is investigated with the option of a fiberoptic coupling between the scintillator and CCD. The attainable performance by operating the CCD in the charge integration mode is explored experimentally, and computations are presented in order to predict the performance of a modified imaging system operating in the counting pulse-height mode for energy discrimination View full abstract»

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  • A remote console system for balloon borne experiments

    Publication Year: 1993 , Page(s): 913 - 916
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (376 KB)  

    A remote console system is developed to improve remote control over experimental apparatus borne on the balloon. The remote console system, residing at a ground station for balloon-borne experiments, sends commands to the apparatus and receives transmissions from it. The system communicates by radio with microcomputers incorporated in the experimental apparatus borne on a balloon, where the microcomputers control the apparatus individually. The system includes plural personal computers and workstations which share the transmissions from the apparatus. The transmissions from the apparatus are formatted in a bit-oriented protocol, which dispenses with a formatter and facilitates interface with the personal computers. The implementation of the system and the communication between the ground station and the balloon-borne apparatus are described View full abstract»

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  • Mediman: an object oriented programming approach for medical image analysis

    Publication Year: 1993 , Page(s): 950 - 955
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (604 KB)  

    Mediman is a new image analysis package which has been developed to analyze quantitatively positron emission tomography (PET) data. It is object-oriented, it is written in C++, and its user interface is based on InterViews on top of which new classes have been added. Mediman accesses data using external data representation or an import/export mechanism which avoids data duplication. Multimodality studies are organized in a sample database which includes images, headers, color tables, lists and objects of interest (OOIs), and history files. Stored color table parameters allow focusing directly on the interesting position of the dynamic range. Lists allow the organization of the study according to modality, acquisition protocol, and time and spatial properties. OOIs (points, lines, and regions) are stored in absolute 3D coordinates allowing correlation with other coregistered imaging modalities. The benefits of the object-oriented approach are discussed from a development point of view View full abstract»

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  • 1992 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC'92)

    Publication Year: 1993
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (660 KB)  

    The following topics were dealt with: semiconductor detectors; scintillators; scintillation counters; triggering; analog circuits; digital circuits; integrated circuits; reactor instrumentation; well logging; power supplies; medical imaging; detectors for physics applications; environmental applications; space instrumentation View full abstract»

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  • On-board electronics for BLIMP: a balloon-borne prototype for the INTEGRAL satellite

    Publication Year: 1993 , Page(s): 909 - 912
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (300 KB)  

    The data handling electronics for BLIMP, a prototype of the Imager experiment of the INTEGRAL mission, is described. An expandable arrangement electronics architecture is used to handle the data coming from the 100-pixel CsI(Tl) detection plane. The main components of the on-board electronics are based on field programmable gate arrays (FPGAs) which provide flexibility and compactness. This system is capable of handling approximately 10000 events/s. The flexibility and modularity of the electronics are discussed in order to demonstrate how the BLIMP system can provide a baseline for the IMAGER development study View full abstract»

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  • Pulsed ionization chamber methodology applied to reactor power measurement revisited

    Publication Year: 1993 , Page(s): 826 - 831
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (420 KB)  

    During the 1970s, a system was proposed for neutron flux/reactor power measurement and control, i.e., the pulsed ionization chamber (PIC) system. The PIC system is said to provide enhanced performance under extremely severe environmental conditions of temperature and radiation field intensity. The authors examine the question of whether such a new system is needed. PIC methodology is reexamined in the light of state-of-the-art technology and techniques as they apply to reactor applications View full abstract»

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  • Results in online data processing with the data acquisition system of the ALEPH TPC

    Publication Year: 1993 , Page(s): 621 - 625
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (396 KB)  

    The ALEPH detector collects data on e+e- collisions provided by the LEP (Large Electron Positron Collider) storage ring at CERN. The ALEPH TPC (time projection chamber) data acquisition (DAQ) system is based on 768 triple width Fastbus modules, and 36 double width Fastbus modules. The performance and the implementation of the TPC DAQ system are presented. It is shown how online data processing is used to obtain a substantial reduction of the data volume View full abstract»

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  • Signal readout in a-Si:H pixel detectors

    Publication Year: 1993 , Page(s): 323 - 327
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (412 KB)  

    A switch consisting of two a-Si:H p-i-n diodes was studied to read out signals from pixels for the imaging of X-ray or gamma ray distributions. A charge storage time of 20 ms and a readout time of 0.7 μs were achieved. For the detection of single ionizing particles, polysilicon thin-film-transistor amplifiers can be integrated to amplify the small signals at the pixel level before readout. Prototype polysilicon TFT amplifiers were designed and fabricated. The measured gain-bandwidth product was ~300 MHz, and the input equivalent noise charge was ~1000 electrons for a 1-μs shaping time View full abstract»

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  • A method for the measurement of the absolute value of w for X-rays in noble gases: results at 5.9 keV in xenon

    Publication Year: 1993 , Page(s): 661 - 663
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (200 KB)  

    A method is described that allows the measurement of the absolute value of the average energy to produce an ion pair, w, in noble gases for soft X-rays and its energy dependence. It uses a specially designed gas proportional scintillation counter working under electric fields below the ionization threshold. The spectrum of the radiation absorbed, and so the number of photons detected at each energy for a period of time on the order of the minute, is measured with the scintillation counter and, at the same time, the total primary electron charge produced is collected in one of the grids and measured with an electrometer. For pure xenon at 1030 mbar, a value of w=24.2±2.5 eV is measured with 5.9-keV X-rays View full abstract»

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  • An ASIC implementation of digital front-end electronics for a high resolution PET scanner

    Publication Year: 1993 , Page(s): 1017 - 1019
    Cited by:  Papers (9)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (220 KB)  

    An application specific integrated circuit (ASIC) is designed and fabricated. It implements many of the current functions found in the digital front-end electronics for a high resolution positron emission tomography scanner. The ASIC performs crystal selection, energy qualification, time correction, and event counting functions for block technology high resolution PET scanners. Digitized x and y position, event energy, and time information are used by the ASIC to determine block crystal number, qualify the event based on energy, and correct the event time. Event counting and block dead time calculations are performed for system dead time corrections. A loadable sequencer for controlling the analog front-end electronics is implemented. The ASIC is implemented in a 37000 gate, 1.0-μm CMOS gate-array and is capable of handling four million events/second while reducing parts count, cost, and power consumption over current board-level designs View full abstract»

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  • Performance of 2 mm radius straw tube drift cells

    Publication Year: 1993 , Page(s): 578 - 582
    Cited by:  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (312 KB)  

    The performance of a 128-channel test module made with straw tubes of 2-mm radius was studied in a test beam and with cosmic rays. Different gases were used, and for each one the time-to-distance relation and the hit efficiency were measured. Comparisons are made between results obtained using two different electronics readouts. The best solution, of 135 μm, was obtained using 50% ethane, 50% argon and reading out the information with the TDCs (time-to-digital converters), at an operating voltage of 1750 V View full abstract»

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  • Digital mean timers for the Straw Tube Tracking System at SDC

    Publication Year: 1993 , Page(s): 794 - 799
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (364 KB)  

    Application specific integrated circuits (ASICs) are being developed for use with the Straw Tube Tracking System at SDC. These are called digital mean timers, and can be used to accept or reject tracks based on the transverse momentum Pt of the particle. They can also be used to determine whether a pair of hits left in two tubes or sets of tubes is caused by the same particle, by summing the drift times. These devices use chains of slowed digital buffers whose propagation delay is variable through one or two control voltages. A clock lock circuit on the chip uses an external crystal controlled oscillator to develop the correct control voltage (s) for a given delay per stage. Results from the first two chip designs are presented View full abstract»

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  • Properties of CdTe(Cl) crystal used for radiation detector

    Publication Year: 1993 , Page(s): 405 - 408
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (236 KB)  

    A new method is described for growing CdTe crystals doped with chloride by using a radiofrequency traveling heater method (THM) which can provide excellent uniformity for the Cl atoms in the crystal. The relationship between response characteristics by γ-ray detection and crystal properties studied by photoluminescence (PL) measurements is discussed. In the RF-THM crystal sample, the emission intensity ratios between the 1.5932 eV and 1.5905 eV lines due to bound excitons from chlorine are nearly constant for all parts of one ingot. From this result, it is suggested that the Cl atoms are uniformly distributed through the whole of the crystal. Using crystals grown by this method, a large number of high-quality radiation detectors which exhibit the same characteristics can be produced from one CdTe ingot View full abstract»

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  • Designing position sensitive NaI(Tl) bar-detectors with an empirical model

    Publication Year: 1993 , Page(s): 1008 - 1011
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (416 KB)  

    In 1-D position sensitive bar-detectors, multiple internal reflections and edge effects of scintillation light cause excessive light spread and lead to poor intrinsic spatial resolution along the length of the detector. An empirical model to evaluate surface treatment techniques in containing light spread is developed. In this model, a Lucite bar and a light-emitting diode (LED) are used to simulate light propagation and refraction in a NaI(Tl) bar-detector. Light sensors are placed above the exit window, with an air gap, for spatial recording of light refracted out of the bar. Among the eleven different combinations of surface treatments evaluate, three-side transverse sanding is the compromise between light spread and total light output. These results are confirmed by experiments performed on NaI(Tl) bar-detectors. This model could be a valuable tool to guide the design of position sensitive NaI(Tl) bar-detectors View full abstract»

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  • A fast, wide range charge integrator and encoder ASIC for photomultiplier tubes

    Publication Year: 1993 , Page(s): 750 - 752
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (288 KB)  

    A high-speed range pipelined integrator and encoder ASIC for fast digitization of charge from photomultiplier tubes is under development at Fermilab. The application-specific integrated circuit (ASIC) is intended to operate in conjunction with a fast analog-digital converter (ADC) to digitize signals from a charge source over a dynamic range of 18-20 b with 8-10 b of accuracy every 16 ns. Development of the device, called QIE (charge integrator and encoder), is being carried out in an IC process with CMOS and NPN devices. Many chips have been designed and tested to prove the feasibility of the device View full abstract»

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  • First level calorimeter trigger system for the Large Hadron Collider

    Publication Year: 1993 , Page(s): 685 - 687
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (272 KB)  

    As part of a research and development project to study first-level calorimeter triggers for the Large Hadron Collider (LHC) an application specific integrated circuit (ASIC) is designed. It will search for candidate electromagnetic clusters associated with a particular cell from a 4×4 area of the calorimeter. The ASIC takes in sixteen (4×4) 8-b digitized signals from the calorimeter and will provide two results: (i) a flag to indicate the presence of an EM cluster; and (ii) a sum over the 4×4 area which will be used in the subsequent logic in the trigger system to search for jets and to calculate missing transverse energy. In the LHC, the bunch-crossing period is 15 ns, and therefore the logic is implemented on the ASIC using a pipelined architecture, with pipeline steps of 15 ns. The algorithm is implemented on a 0.8-μm CMOS gate array and is packaged in a 179 pin ceramic pin grid array. The ASIC is tested above the full operating frequency of 67 MHz View full abstract»

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  • Performance of the Forward Drift Chambers for the DO detector

    Publication Year: 1993 , Page(s): 573 - 577
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (280 KB)  

    The Forward Drift Chambers (FDCs) provide tracking in the forward region for the D0L experiment at Fermilab. The chambers must perform precision track position measurement in a high multiplicity environment. These chambers were extensively tested in the Fermilab NWA test beam area, in beams of 10-150 GeV pions and electrons. Measurements included the position resolution, hit finding efficiency, two track resolution, and ionization measurement resolution. The results of these tests are presented. These tests demonstrate that the chambers are able to perform the tasks for which they were designed. The chambers have now been installed in the D0L experiment and are participating in the current Tevatron collider run View full abstract»

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  • Test of a Nb thin film superconducting detector

    Publication Year: 1993 , Page(s): 360 - 363
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (272 KB)  

    Results from tests of several Nb thin film microstrip superconducting detectors are reported. A preliminary measurement of critical radius of the hot spot generated by 5 MeV α-particles is compared with simple model predictions. An effort is made to understand and measure the propagation characteristics of the superconducting to normal transition along the strip. For this purpose, fast current pulses are injected into the strip, and the voltage drop is observed with a digital scope View full abstract»

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  • Proton therapy in combination with PET as monitor: a feasibility study

    Publication Year: 1993 , Page(s): 1041 - 1044
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (248 KB)  

    To evaluate the possibility of combining proton therapy with positron emission tomography (PET) as a therapy monitor and as a tool for in situ dosimetry during therapy, proton activation experiments are performed using a 55-MeV proton beam on two different materials. The 3-D measurements of the induced activity with PET are compared with the calculated dose distribution and with model calculations View full abstract»

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  • Bar-detector with extended field of view for a modular SPECT system

    Publication Year: 1993 , Page(s): 1130 - 1133
    Cited by:  Papers (4)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (372 KB)  

    In the conventional centroid positon estimation method, the effective field of view (FOV) of a scintillation bar-detector cannot be extended beyond the centers of the two outside photomultiplier tubes (PMTs). To extend the FOV, statistical position estimation on a bar-detector with blackened end surfaces is implemented. Maximum likelihood (ML) and minimum square error (MSE) position estimation lookup tables (LUTs) are calculated from experimentally measured histogram data. Both statistical estimators provide a 14-cm FOV on a 16-cm bar, with 4-mm to 6-mm full width half maximum (FWHM) within the FOV. In contrast, the centroid method provides a 10-cm FOV on a conventional bar-detector. In order to reduce the size of LUTs and memory requirements, the feasibility of using local, 2-D LUTs for position estimation is demonstrated. Using statistical position estimation methods and scatter-free sources, it is possible to extend the FOV beyond the conventional limit to utilize 90% of the bar-detector area View full abstract»

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