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Nuclear Science, IEEE Transactions on

Issue 3  Part 3 • Date June 2008

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Displaying Results 1 - 25 of 40
  • Table of contents

    Page(s): C1 - 1566
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  • IEEE Transactions on Nuclear Science publication information

    Page(s): C2
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  • Spectral Response of THM Grown CdZnTe Crystals

    Page(s): 1567 - 1572
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1254 KB) |  | HTML iconHTML  

    The spectral response of several crystals grown by the Traveling Heater Method (THM) were investigated. An energy resolution of 0.98% for a Pseudo Frisch-Grid of 4 times 4 times 9 mm3 and 2.1% FWHM for a coplanar-grid of size 11 times 11 times 5 mm3 were measured using 137Cs-662 keV. In addition a 4% FWHM at 122 keV has also been measured on 20 times 20 X 5 mm3 monolithic pixellated devices. The material shows great potential toward producing large-volume detectors with spectral performance that meets the requirement for high-resolution gamma-ray spectroscopy. View full abstract»

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  • A New Architecture for Pixellated Solid State Gamma Camera Used in Nuclear Medicine

    Page(s): 1573 - 1580
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2117 KB) |  | HTML iconHTML  

    The purpose of this paper is to introduce a novel technique for acquiring and reconstructing planar or tomographic images obtained using a gamma camera. The aim is to overcome the sensitivity-spatial resolution tradeoff for conventional Anger gamma cameras. The future generation of solid state gamma cameras will benefit from the recent advances in CdZnTe (CZT) detector performances. Previous studies have shown that pixellated CZT detectors have a high energy resolution, good detection efficiency and a high intrinsic spatial resolution. Moreover, these detectors provide important additional information: the depth of interaction (DOI). In this paper, we introduce the HiSens (High Sensitivity) architecture: an original collimator architecture associated with a CZT pixellated detector that takes advantage of such performances, particularly in terms of DOI information and an adapted method of iterative reconstruction. We explain about the ability of our CZT detector, associated with specific electronic processing, to obtain accurate DOI information on a 5 mm-thick CZT detector. We have used SINDBAD simulation tool to evaluate the performance of the HiSens architecture. We describe an adapted iterative reconstruction using the CZT DOI information in order to improve image quality. Then we show preliminary simulation results of the HiSens architecture performances. View full abstract»

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  • Single Event Upset Mechanisms for Low-Energy-Deposition Events in SiGe HBTs

    Page(s): 1581 - 1586
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (617 KB) |  | HTML iconHTML  

    Microbeam measurements and TCAD simulations are used to examine the effects of ion angle of incidence on the charge collected from events occurring in a Silicon Germanium (SiGe) Heterojunction Bipolar Transistor (HBT). The results identify the geometrically driven charge-collection mechanisms that dominate the low LET broad beam SEU response. The deep trench isolation that surrounds the transistor significantly modulates the charge transport and, therefore, the charge collected by the collector. A new way of estimating critical charge, , for upset in SiGe HBT circuits is proposed based on TCAD simulation results and measured broadbeam data. View full abstract»

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  • A Very-Front-End ADC for the Electromagnetic Calorimeter of the International Linear Collider

    Page(s): 1587 - 1592
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    A 10-bit pipeline analog-to-digital converter is introduced in this paper and the measurements carried out on prototypes produced in a 0.35 m CMOS technology are presented. This ADC is a building block of the very-front-end electronics dedicated to the electromagnetic calorimeter of the International Linear Collider (ILC). Based on a 1.5-bit per stage resolution architecture, it reaches the 10-bit accuracy at a sampling rate of 4 MSamples/s with a consumption of 35 mW. The Integral and Differential Non-Linearity obtained are respectively within LSB and LSB, and the measured noise is 0.47 LSB r.m.s. The performance obtained confirms that the pipeline architecture ADC is suitable to the requirements of the readout electronics of the electromagnetic calorimeter. View full abstract»

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  • Readout ASIC for 3D Position-Sensitive Detectors

    Page(s): 1593 - 1603
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    We describe an application specific integrated circuit (ASIC) for 3D position-sensitive detectors. It was optimized for pixelated cadmium-zinc-telluride (CZT) sensors, and it measures, corresponding to an ionizing event, the energy and timing of signals from 121 anodes and one cathode. Each channel provides low-noise charge amplification, high-order shaping, along with peak- and timing-detection. The cathode's timing can be measured in three different ways: the first is based on multiple thresholds on the charge amplifier's voltage output; the second uses the threshold crossing of a fast-shaped signal; and the third measures the peak amplitude and timing from a bipolar shaper. With its power of 2 mW per channel the ASIC measures, on a CZT sensor connected and biased, charges up to 100 fC with an electronic resolution better than 200 e- rms. Our preliminary spectral measurements applying a simple cathode/anode ratio correction demonstrated a single-pixel resolution of 4.8 keV (0.72 %) at 662 keV, with the electronics and leakage current contributing in total with 2.1 keV. View full abstract»

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  • Front-End ASIC for High Resolution X-Ray Spectrometers

    Page(s): 1604 - 1609
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (750 KB) |  | HTML iconHTML  

    We present an application specific integrated circuit (ASIC) for high-resolution X-ray spectrometers. The ASIC is designed to read out signals from a pixelated silicon drift detector (SDD). Each hexagonal pixel has an area of 15 mm2 and an anode capacitance of less than 100 fF. There is no integrated Field Effect transistor (FET) in the pixel, rather, the readout is done by wire-bonding the anodes to the inputs of the ASIC. The ASIC provides 14 channels of low-noise charge amplification, high-order shaping with baseline stabilization, and peak detection with analog memory. The readout is sparse and based on low voltage differential signaling. An interposer provides all the interconnections required to bias and operate the system. The channel dissipates 1.6 mW. The complete 14-pixel unit covers an area of 210 mm2, dissipates 12 mW cm-2, and can be tiled to cover an arbitrarily large detection area. We measured a preliminary resolution of 172 eV at -35 degC on the 6 keV peak of a 55Fe source. View full abstract»

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  • The ATLAS Event Monitoring Service—Peer-to-Peer Data Distribution in High-Energy Physics

    Page(s): 1610 - 1620
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    The ATLAS event monitoring service (Emon) is a CORBA-based peer-to-peer data distribution framework, which has been implemented for ATLAS - one of CERN's forthcoming particle physics experiments. Its purpose is to sample collision event data from various stages of the data flow chain and efficiently distribute them to the users. This paper discusses various technical details of the current peer-to-peer-based implementation. A special focus lies on dependability and the provision of scalability and predictable performance. A comparative study of message complexity and scalability as well as practical test results obtained during the HLT/DAQ large scale and performance test periods in July 2005 and November 2006 will be presented. Apart from that, a recent addition that facilitates the parallel analysis of event data on a set of machines will be presented. View full abstract»

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  • A Comparison of Data-Access Platforms for the Computing of Large Hadron Collider Experiments

    Page(s): 1621 - 1630
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    Performance, reliability and scalability in data-access are key issues in the context of the computing Grid and High Energy Physics data processing and analysis applications, in particular considering the large data size and I/O load that a Large Hadron Collider data centre has to support. In this paper we present the technical details and the results of a large scale validation and performance measurement employing different data-access platforms-namely CASTOR, dCache, GPFS and Scalla/Xrootd. The tests have been performed at the CNAF Tier-1, the central computing facility of the Italian National Institute for Nuclear Research (INFN). Our storage back-end was based on Fibre Channel disk-servers organized in a Storage Area Network, being the disk-servers connected to the computing farm via Gigabit LAN. We used 24 disk-servers, 260 TB of raw-disk space and 280 worker nodes as computing clients, able to run concurrently up to about 1100 jobs. The aim of the test was to perform sequential and random read/write accesses to the data, as well as more realistic access patterns, in order to evaluate efficiency, availability, robustness and performance of the various data-access solutions. View full abstract»

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  • Hardware-Based TCP Processor for Gigabit Ethernet

    Page(s): 1631 - 1637
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    Transmission control protocol (TCP) and Ethernet have been widely used in readout systems. These protocols are de facto standards and have been implemented on standard operating systems. However, some small devices, e.g., front-end devices and detectors, are not capable of employing these protocols because of hardware size limitations. This paper describes a TCP processor for gigabit Ethernet with a circuit size suitable for implementing on a single field programmable gate array. The only peripheral device required is a single Ethernet physical layer device. The hardware was implemented and its TCP throughput was measured. The throughputs in both directions simultaneously were at the upper limits of gigabit Ethernet. A mechanism for slow control over user datagram protocol (UDP) is also provided. The processor described here allows adoption of TCP/Ethernet in small devices that have hardware size limitations. View full abstract»

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  • Mobile-Dose: A Dose-Meter Designed for Use in Automatic Machineries for Dose Manipulation in Nuclear Medicine

    Page(s): 1638 - 1643
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1765 KB) |  | HTML iconHTML  

    Mobile-Dose has been designed for a very innovative use: the integration in a robotic machinery for automatic preparation of radioactive doses, to be injected to patients in Nuclear Medicine Departments, with real time measurement of the activity under preparation. Mobile-Dose gives a constant measurement of the dose during the filling of vials or syringes, triggering the end of the filling process based on a predefined dose limit. Several applications of Mobile-Dose have been delivered worldwide, from Italian hospitals and clinics to European and Japanese ones. The design of such an instrument and its integration in robotic machineries, was required by an Italian company specialised in radiation protection tools for nuclear applications, in the period 2001-2003. At the time of its design, apparently no commercial instruments with a suitable interfacing capability to the external world existed: we designed it in order to satisfy all the strict requirements coming from the medical aspects (precision within 10%, repeatability, stability, time response) and from the industrial conceiving principles that are mandatory to ensure a good reliability in such a complicated environment. The instrument is suitable to be used in standalone mode too, thanks to its portability and compactness and to the intelligent operator panel programmed for this purpose. View full abstract»

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  • A Fast Crystal Identification Algorithm Applied to the LabPET™ Phoswich Detectors

    Page(s): 1644 - 1651
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1132 KB) |  | HTML iconHTML  

    Detectors based on LYSO and LGSO scintillators in a phoswich arrangement coupled to an avalanche photodiode are used in the LabPETtrade, an all-digital positron emission tomography (PET) scanner for small animal imaging developed in Sherbrooke. A Wiener filter based crystal identification (CI) algorithm achieving excellent discrimination accuracy was recently proposed for crystal identification of LYSO-LGSO phoswich detectors . This algorithm was based on estimating parameters describing the scintillation decay time constant and the light yield of events sampled at 45 MSPS. The CI process was performed by applying a threshold on the scintillation decay parameter of events. The light yield was not considered in the CI process even if it should be. We propose a 2-fold faster CI approach which takes both the scintillation decay and light yield coefficients of each crystal into consideration. The new algorithm uses the previous Wiener filter based algorithm as a calibration process in order to evaluate the model of each individual crystal. The DAQ chain model as a priori knowledge is then incorporated into the model of each crystal and the output signal is estimated. The CI is performed by evaluating a single parameter representing the percentage contribution of each crystal characteristics in the event signal. The CI algorithm demonstrated a discrimination rate accuracy for LYSO-LGSO LabPET detectors and for LSO-GSO crystals in phoswich arrangement for 511 keV events. Although a calibration is required, the real-time implementation of the new CI algorithm needs 2 times less direct operations. An FPGA clocked at 400 MHz can process up to 25 M events/sec with such an algorithm. View full abstract»

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  • The Photon-Assisted Cascaded Electron Multiplier Operation in CF _{4} for Ion Backflow Suppression

    Page(s): 1652 - 1656
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    The operation of the recently introduced photon assisted cascaded electron multiplier (PACEM) in CF4 is investigated. The PACEM uses the VUV scintillation produced in the electron avalanches of the first multiplier of the cascade to transfer the signal to the subsequent ones. The VUV scintillation induces the emission of a large number of photoelectrons from a Csl photocathode placed on the top-surface of the second multiplier. The photoelectrons are further multiplied in the subsequent stages of the cascade, resulting in efficient signal amplification. A mesh, set at a fixed voltage, is placed between the first and the second multipliers to block the charge transfer between them, thus suppressing all the ion backflow (IBF) heading to the first cascade element. The PACEM electrically isolates the first multiplier of the cascade and only the ions produced in the electron avalanches of the first element may flow back into the drift region. Operating in CF4, absolute IBFs as low as ~1 ion per primary electron are achieved for drift fields of 0.1 kV/cm, while for fields of 0.5 kV/cm the absolute IBF is ~10 ions/primary electron. This corresponds to an IBF of 10-4 at gains of 104, for time projection chambers (TPC) operating conditions, and IBFs of ~10-5 at gains of 106 for gaseous photomultipliers (GPM) operating conditions. View full abstract»

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  • Development of New Hole-Type Avalanche Detectors and the First Results of Their Applications

    Page(s): 1657 - 1663
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (906 KB) |  | HTML iconHTML  

    We have developed a new detector of photons and charged particles-a hole-type structure with electrodes made of a double layered resistive material: a thin low resistive layer coated with a layer having much higher resistivity. One of the unique features of this detector is its capability to operate at high gas gains (up to ) in air or in gas mixtures with air. They can also operate in a cascaded mode or be combined with other detectors, for example with GEM. This opens new avenues in their applications. Several prototypes based on this new detector and oriented to practical applications were developed and successfully tested: a detector of soft X-rays and alpha particles, a flame sensor, a detector of dangerous gases. All of these devices could operate stably even in humid air and/or in dusty conditions. The main advantages of these devices are their simplicity, low cost, and high sensitivity. For example, due to the avalanche multiplication, the detectors of flames and dangerous gases have a sensitivity of 10-100 times higher than commercial devices. We therefore believe that new detectors will have a great future. View full abstract»

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  • A New Concept of Thermal Neutron Counting With Sub-Microsecond Timing Resolution

    Page(s): 1664 - 1669
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (685 KB) |  | HTML iconHTML  

    A conceptual design of a novel type of thermal and cold neutron counting detector with one-dimensional spatial resolution of m, and timing resolution as low as nanoseconds, is proposed. The detector uses microchannel plates (MCPs) doped with neutron absorbing B atoms. MCP-based detectors allow two-dimensional position localization of neutron events with resolution better than 30 m and s timing accuracy. The intrinsic temporal resolution of MCP detectors is in the subnanosecond range. In this paper we show how this combination of high 2-D spatial (m) and temporal (s) resolution can be converted into 1-D spatial (m) and ns timing resolution for each detected neutron. Another unique characteristic of the proposed neutron detector is its rather high neutron detection efficiency, exceeding 50%, as predicted by our extensive analytical modeling, accuracy of which was confirmed by the first experimental measurements. The active area of these detectors can be as large as 1010 cm in the 2-D configuration and 1001 mm in the 1-D case. One-dimensional detectors can be staggered to perform imaging in two dimensions with high timing resolution. View full abstract»

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  • Detection of Flow-Induced Vibration of Reactor Internals by Neutron Noise Analysis

    Page(s): 1670 - 1677
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (377 KB) |  | HTML iconHTML  

    Flow-induced vibrations of reactor core components have been a major cause of failure of reactor internals in many nuclear power plants. To address this issue international standards (viz., ASME-OM-05) require monitoring of structural integrity of reactor core in nuclear power plants. A reactor internals vibration monitoring system (IVMS) has been developed for nuclear power plant surveillance. The system detects the core barrel motion and flow-induced vibrations of reactor internals by analyzing the inherent fluctuations (reactor noise) present in the neutron flux signals from ex-core neutron detectors. Before application of the IVMS in nuclear power plants the system hardware and methodology/software has been extensively tested on the research reactor through a series of reactor noise measurements. In the noise measurements the neutron flux signals were correlated with the signals from vibration sensors mounted on reactor structure and control rods drive mechanisms. The frequency spectra of reactor power signals obtained with IVMS had shown small oscillations in the neutron flux signals at well-defined frequencies. There was a strong correlation of these fluctuations with the establishment of coolant flow through the core. With the help of elaborate experiments using the IVMS the cause of oscillations in neutron flux signals was attributed to the flow-induced vibrations of control rods, and the particular vibrating control rod was identified. The magnitude of the displacement of vibrating control rod was calculated from the measured power spectral density of neutron power signals. It has been shown that ex-core neutron noise measurements are more sensitive in determining the dynamic behavior of reactor internals than the vibration sensors mounted at remote, out-of-the core locations. View full abstract»

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  • Adaptive Critic-based Neurofuzzy Controller for the Steam Generator Water Level

    Page(s): 1678 - 1685
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (257 KB) |  | HTML iconHTML  

    In this paper, an adaptive critic-based neurofuzzy controller is presented for water level regulation of nuclear steam generators. The problem has been of great concern for many years as the steam generator is a highly nonlinear system showing inverse response dynamics especially at low operating power levels. Fuzzy critic-based learning is a reinforcement learning method based on dynamic programming. The only information available for the critic agent is the system feedback which is interpreted as the last action the controller has performed in the previous state. The signal produced by the critic agent is used alongside the backpropagation of error algorithm to tune online conclusion parts of the fuzzy inference rules. The critic agent here has a proportional-derivative structure and the fuzzy rule base has nine rules. The proposed controller shows satisfactory transient responses, disturbance rejection and robustness to model uncertainty. Its simple design procedure and structure, nominates it as one of the suitable controller designs for the steam generator water level control in nuclear power plant industry. View full abstract»

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  • Thermal and Electrical Characterization of Silicon Photomultiplier

    Page(s): 1686 - 1690
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    Detection of low levels of light is one of the key aspects in medical and space applications. Silicon photomultiplier, a novel type of avalanche photodetector which operates in Geiger mode, shows promising results and offer superior design options. The performance characteristics of the SiPM realized in FBK-irst are studied and presented in this paper. The leakage current, dark rate and internal gain are characterized as a function of temperature. The investigation has been carried out in the framework of the DASiPM Collaboration and the INFN/FBK-irst MEMS project. View full abstract»

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  • MAPMT H7546B Anode Current Response Study for an ILC SiD Muon System Prototype

    Page(s): 1691 - 1694
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (129 KB) |  | HTML iconHTML  

    The proposed silicon detector concept for the international linear collider has a barrel and end cap muon systems. The scintillator based muon system prototype has 256 scintillating strips, wavelength-shifting fibers, and clear fibers connected to multianode photo multiplier tubes (MAPMT). Six Hamamatsu H7546B tubes were used. To understand strip output, each of 384 MAPMT outputs was independently measured at a given luminous flux and the same photocathode to anode voltage of 800 V. For the test, a custom made source of light was used. The anode currents have a wide spread; for all tubes the maximum value is 5.23 times larger than the minimum value. The MAPMT cross talk was measured for one of the central inputs. The maximum cross talk value is about 4.9%. The average cross talk for the nearest four neighboring channels is 3.9%, for the farther four 1%. To assure reproducibility and repeatability of the measurements a double reference method was used. View full abstract»

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  • Charge Collection Efficiency Measurements for Segmented Silicon Detectors Irradiatedto 1\times 10^{16} {\hbox {n}} {\hbox {cm}}^{-2}

    Page(s): 1695 - 1699
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (371 KB) |  | HTML iconHTML  

    Plans are well advanced for a phased upgrade program of the Large Hadron Collider (LHC) at CERN. An improvement of nearly a factor of ten to reach a luminosity close to 1035 cm2 s-1 is the target of the upgraded machine, called the Super LHC (SLHC). The innermost tracker devices in the SLHC will be exposed to hadron radiation doses in excess of 1 times 1016 neq cm-2. The detectors to be used in the tracker system of the SLHC experiments need therefore to be qualified to these extreme fluences. Segmented n-strip silicon detectors made with thin (140 mum) and standard (300 mum) p-type substrates have been irradiated with neutrons to different fluences up to 1 times 1016 neq cm-2 and characterised in term of charge collection efficiency measurements using high speed (40 MHZ, 25 ns shaping time) analogue electronics. These measurements are the first direct comparison between the charge collection performance of thin and thick silicon microstrip devices as a function of different fluences relevant to future supercolliders. They also set a reference for the maximum collected charge by segmented sensors made in planar technologies (microstrip and pixel detectors) at these extreme doses, allowing for predictions on the functionality of silicon detectors that can operated in the inner tracking system of SLHC experiments. View full abstract»

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  • Efficient Protection Techniques Against SEUs for Adaptive Filters: An Echo Canceller Case Study

    Page(s): 1700 - 1707
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (675 KB) |  | HTML iconHTML  

    In this paper, novel protection techniques against soft errors for adaptive filters are presented. The new techniques are based on the use of system knowledge in terms of both filter structure and functionality, as well as the application tolerance to soft errors. Adaptive filters by nature recover from soft errors on their coefficients, but in existing implementations the recovery time can exceed what is acceptable for many applications. The proposed techniques dramatically reduce the recovery time after a soft error with an acceptable increment on circuit complexity, as they rely on reusing existing logic. To illustrate these techniques, a case study is presented in which their effectiveness is evaluated using a software-based fault injection platform. Also, their complexity is estimated in terms of the number of equivalent gates generated for the synthesized circuit implementation using a commercial ASIC library. View full abstract»

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  • Effects of Guard Bands and Well Contacts in Mitigating Long SETs in Advanced CMOS Processes

    Page(s): 1708 - 1713
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    Mixed mode TCAD simulations are used to show the effects of guard bands and high density well contacts in maintaining the well potential after a single event strike and thus reduce the width of long transients in a 130-nm CMOS process. Experimental verification of the effectiveness in mitigating long transients was achieved by measuring the distribution of SET pulse widths produced by heavy ions for circuits with isolated contacts and for circuits with guard bands combined with larger contacts in a 130-nm process using an autonomous characterization technique. Heavy-ion test results indicate that controlling the well potential by using guard bands, along with high density well contacts, helps eliminate of SETs longer than 1 ns. View full abstract»

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  • Proton Radiation Effects on MEMS Silicon Strain Gauges

    Page(s): 1714 - 1718
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    A microelectromechanical system (MEMS) strain gauge constructed from single-crystalline silicon has been developed for application in aircraft structural-health-monitoring. The effects of proton irradiation on the piezoresistive elements of the silicon strain gauges are examined. Degradation in the piezoresistive response at applied strains above 2000 microstrain is observed. View full abstract»

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  • Dark Current Spectroscopy of Irradiated CCD Image Sensors

    Page(s): 1719 - 1724
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (224 KB) |  | HTML iconHTML  

    Dark current spectroscopy is used to directly investigate deep-level traps induced by alpha particle irradiation in charge-coupled devices, at trap concentrations as low as ~2 times 107 cm-3. The irradiated devices have long dark current histogram tails that are quantized at long imager integration times. This quantization is due to the discrete nature of the distribution of the radiation-induced traps within the device pixels. Four distinct traps, with different dark current generation rates, are found and characterized in terms of their activation energies and capture cross-sections. Two of the traps, identified as the divacancy and the E-center (phosphorus-vacancy), have the highest concentrations and generation rates and are the main constituents of the irradiation tails. The origin of these irradiation tails is explained as a superposition of peaks formed by pixels that contain from a single deep-level trap to multiple traps of the same or different types. Divacancy annealing is shown to result in the formation of four additional traps, which are tentatively attributed to vacancy-oxygen, vacancy-hydrogen, and high-order silicon-vacancy complexes. View full abstract»

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