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Nuclear Science, IEEE Transactions on

Issue 5 • Date Oct 1995

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Displaying Results 1 - 7 of 7
  • Designing a linear silicon drift detector

    Page(s): 1497 - 1504
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (684 KB)  

    The design and 2D simulation results of a Silicon Drift Chamber with a rectangular configuration are presented. The proposed structure is intended to allow a test of the technology used in the production of the device and serve as a basis to verify different solutions in the design of drift detectors View full abstract»

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  • Solar particle induced upsets in the TDRS-1 attitude control system RAM during the October 1989 solar particle events

    Page(s): 1489 - 1496
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (648 KB)  

    The three large solar particle events, beginning on October 19, 1989 and lasting approximately six days, were characterized by high fluences of solar protons and heavy ions at 1 AU. During these events, an abnormally large number of upsets (243) were observed in the random access memory of the attitude control system (ACS) control processing electronics (CPE) on-board the geosynchronous TDRS-1 (Telemetry and Data Relay Satellite). The RAR I unit affected was composed of eight Fairchild 93L422 memory chips. The Galileo spacecraft, launched on October 18, 1989 (one day prior to the solar particle events) observed the fluxes of heavy ions experienced by TDRS-1. Two solid-state detector telescopes on-board Galileo designed to measure heavy ion species and energy, were turned on during time periods within each of the three separate events. The heavy ion data have been modeled and the time history of the events reconstructed to estimate heavy ion fluences. These fluences were converted to effective LET spectra after transport through the estimated shielding distribution around the TDRS-1 ACS system. The number of single event upsets (SEU) expected was calculated by integrating the measured cross section for the Fairchild 93L422 memory chip with average effective LET spectrum. The expected number of heavy ion induced SEUs calculated was 176. GOES-7 proton data, observed during the solar particle events, were used to estimate the number of proton-induced SEUs by integrating the proton fluence spectrum incident on the memory chips, with the two-parameter Bendel cross section for proton SEUs View full abstract»

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  • A qualification test for relay contacts as isolation devices in nuclear power plants

    Page(s): 1467 - 1473
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    A methodology is introduced for testing the integrity of relay contacts as isolation devices in Class IE circuits. A design activity that installed a new relay established the need for a new type of qualification test. This paper describes the process of establishing the test methodology, the development of the test plan, and the results of testing. It also describes the limitations of applying the results of any specific test to actual field installations, and offers other potential uses of the methodology View full abstract»

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  • Local polarization phenomena in In-doped CdTe X-ray detector arrays

    Page(s): 1513 - 1518
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (488 KB)  

    Local polarization phenomena have been studied in detector arrays with the detector element size of 500 μm×500 μm, which are fabricated from high-resistivity In-doped CdTe crystals grown by the vertical Bridgman technique. It has been found for the first time that a polarization effect, which is characterized by a progressive decrease of the pulse counting rate with increasing photon fluence, strongly depends on the detector elements, that is, the portion of crystals used. The influence of several parameters, such as the applied electric field strength, time, and temperature, on this local polarization effect is also investigated. From the photoluminescence measurements of the inhomogeneity of In dopant, it is concluded that the local polarization effect observed here originates from an deep level associated with In dopant in CdTe crystals View full abstract»

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  • An interpretation of the mechanism of the self quenching streamer

    Page(s): 1505 - 1512
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    In this paper, the experiments on self quenching streamer (SQS) discharge in single wire and multi-wire chambers are performed, and a possible Interpretation of the SQS mechanism is proposed on the basis of analyzing the previous experimental results. According to this model, the excited atoms or molecules created in the latent track and subsequent avalanches play an important role. They form the main photo electron source. The interaction between them is also possibly a source of ionizing photons. Thus, a formula that describes the streamer transition and streamer charge is deduced. A comparison between theory and experiments is made. It is indicated that whether the streamer transition occurs or not, the absorption and radiation characteristics of the atoms or molecules of gases in the mixture is the decisive factor, and as a result of the difference in those characteristics, the different operating modes appear View full abstract»

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  • YAP multi-crystal gamma camera prototype

    Page(s): 1474 - 1482
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    The Anger camera principle has shown a practical limit of a few millimeters spatial resolution. To overcome this limit, a new gamma camera prototype has been developed, based on a position-sensitive photomultiplier tube (PSPMT) coupled with a new scintillation crystal. The Hamamatsu R2486 PSPMT is a 76-mm diameter photomultiplier tube in which the electrons produced in the conventional bi-alkali photocathode are multiplied by proximity mesh dynodes and form a charge cloud around the original coordinates of the light photon striking the photocathode. A crossed wire anode array collects the charge and detects the original position. The intrinsic spatial resolution of PSPMT is better than 0.3 mm. The scintillation crystal consists of yttrium aluminum perovskit (YAP:Ce or YAlO3:Ce). This crystal has a light efficiency of about 38% relative to NaI, no hygroscopicity and a good gamma radiation absorption. To match the characteristics of the PSPMT, a special crystal assembly was produced by the Preciosa Company, consisting of a bundle of YAP:Ce pillars where single crystals have 0.6×0.6 mm2 cross section and 3 mm to 18 mm length. Preliminary results from such gamma camera prototypes show spatial resolution values ranging between 0.7 mm and 1 mm with an intrinsic detection efficiency of 37÷65% for 140 keV gamma energy View full abstract»

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  • Approximate reconstruction of attenuation map in SPECT imaging

    Page(s): 1483 - 1488
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (508 KB)  

    The influence of linear attenuation presents certain difficulties for quantitative single-photon emission computed tomography (SPECT) in medical imaging. To apply an attenuation correction algorithm, one has first to estimate the attenuation map from some additional measurements or by the use of SPECT data. The determination of the attenuation map from SPECT-type data may also be considered as a special problem of nondestructive evaluation of materials. A new technique for obtaining the attenuation map from SPECT data is proposed. Unlike other methods, the approach suggested demands no a priori knowledge of the problem. The method has been derived on the basis of the approximate linear relation between SPECT data and the attenuation map. The approach permits local changes of the attenuation coefficient to be reconstructed rather than its actual value. In this way, such details of the attenuation map as spots, curves and edges can be localized. Limitations of application of the suggested technique to real data are considered. Results of numerical evaluation and real data processing are presented 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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