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Nuclear Science, IEEE Transactions on

Issue 3 • Date June 2014

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Displaying Results 1 - 25 of 45
  • Table of Contents

    Page(s): C1 - 1207
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    Freely Available from IEEE
  • IEEE Transactions on Nuclear Science publication information

    Page(s): C2
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  • In Memoriam [Glenn Frederick Knoll]

    Page(s): 1208
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  • Real-Time Processing System for the JET Hard X-Ray and Gamma-Ray Profile Monitor Enhancement

    Page(s): 1209 - 1215
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1005 KB) |  | HTML iconHTML  

    The Joint European Torus (JET) is currently undertaking an enhancement program which includes tests of relevant diagnostics with real-time processing capabilities for the International Thermonuclear Experimental Reactor (ITER). Accordingly, a new real-time processing system was developed and installed at JET for the gamma-ray and hard X-ray profile monitor diagnostic. The new system is connected to 19 CsI(Tl) photodiodes in order to obtain the line-integrated profiles of the gamma-ray and hard X-ray emissions. Moreover, it was designed to overcome the former data acquisition (DAQ) limitations while exploiting the required real-time features. The new DAQ hardware, based on the Advanced Telecommunication Computer Architecture (ATCA) standard, includes reconfigurable digitizer modules with embedded field-programmable gate array (FPGA) devices capable of acquiring and simultaneously processing data in real-time from the 19 detectors. A suitable algorithm was developed and implemented in the FPGAs, which are able to deliver the corresponding energy of the acquired pulses. The processed data is sent periodically, during the discharge, through the JET real-time network and stored in the JET scientific databases at the end of the pulse. The interface between the ATCA digitizers, the JET control and data acquisition system (CODAS), and the JET real-time network is provided by the Multithreaded Application Real-Time executor (MARTe). The work developed allowed attaining two of the major milestones required by next fusion devices: the ability to process and simultaneously supply high volume data rates in real-time. View full abstract»

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  • The New Feedback Control System of RFX-mod Based on the MARTe Real-Time Framework

    Page(s): 1216 - 1221
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    A real-time system has been successfully used since 2004 in the RFX-mod nuclear fusion experiment to control the position of the plasma and its Magneto Hydrodynamic (MHD) modes. However, its latency and the limited computation power of the used processors prevented the usage of more aggressive control algorithms. Therefore a new hardware and software architecture has been designed to overcome such limitations and to provide a shorter latency and a much increased computation power. The new system is based on a Linux multi-core server and uses MARTe, a framework for real-time control which is gaining interest in the fusion community. View full abstract»

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  • Parallel Task Management Library for MARTe

    Page(s): 1222 - 1227
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (712 KB) |  | HTML iconHTML  

    The Multithreaded Application Real-Time executor (MARTe) is a real-time framework with increasing popularity and support in the thermonuclear fusion community. It allows modular code to run in a multi-threaded environment leveraging on the current multi-core processor (CPU) technology. One application that relies on the MARTe framework is the Joint European Torus (JET) tokamak WAll Load Limiter System (WALLS). It calculates and monitors the temperature on metal tiles and plasma facing components (PFCs) that can melt or flake if their temperature gets too high when exposed to power loads. One of the main time consuming tasks in WALLS is the calculation of thermal diffusion models in real-time. These models tend to be described by very large state-space models thus making them perfect candidates for parallelisation. MARTe's traditional approach for task parallelisation is to split the problem into several Real-Time Threads, each responsible for a self-contained sequential execution of an input-to-output chain. This is usually possible, but it might not always be practical for algorithmic or technical reasons. Also, it might not be easily scalable with an increase in the number of available CPU cores. The WorkLibrary introduces a “GPU-like approach” of splitting work among the available cores of modern CPUs that is (i) straightforward to use in an application, (ii) scalable with the availability of cores and all of this (iii) without rewriting or recompiling the source code. The first part of this article explains the motivation behind the library, its architecture and implementation. The second part presents a real application for WALLS, a parallel version of a large state-space model describing the 2D thermal diffusion on a JET tile. View full abstract»

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  • A Real-Time Architecture for the Identification of Faulty Magnetic Sensors in the JET Tokamak

    Page(s): 1228 - 1235
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    In a tokamak, the accurate estimation of the plasma boundary is essential to maximise the fusion performance and is also the first line of defence for the physical integrity of the device. In particular, the first wall components might get severely damaged if over-exposed to a high plasma thermal load. The most common approach to calculate the plasma geometry and related parameters is based in a large set of different types of magnetic sensors. Using this information, real-time plasma equilibrium codes infer a flux map and calculate the shape and geometry of the plasma boundary and its distance to a known reference (e.g. first wall). These are inputs to one or more controllers capable of acting on the shape and trajectory based in pre-defined requests. Depending on the device, the error of the estimated boundary distance must usually be less than 1 centimetre, which translates into very small errors on the magnetic measurement itself. Moreover, asymmetries in the plasma generated and surrounding magnetic fields can produce local shape deformations potentially leading to an unstable control of the plasma geometry. The JET tokamak was recently upgraded to a new and less thermally robust all-metal wall, also known as the ITER-like wall. Currently the shape controller system uses the output of a single reconstruction algorithm to drive the plasma geometry and the protection systems have no input from the plasma boundary reconstruction. These choices are historical and were due to architectural, hardware and processing power limitations. Taking advantage of new multi-core systems and of the already proved robustness of the JET real-time network, this paper proposes a distributed architecture for the real-time identification of faults in the magnetic measurements of the JET tokamak. Besides detecting simple faults, such as short-circuits and open-loops, the system compares the expected measurement at the coil location and the real measurement, producing a confidence valu- . Several magnetic reconstructions, using sensors from multiple toroidally distributed locations, can run in parallel, allowing for a voting or averaging scheme selection. Finally, any fault warnings can be directly fed to the real-time protection sequencer system, whose main function is to coordinate the protection of the JET's first wall. View full abstract»

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  • Radiation Hardening of an SiGe BiCMOS Wilkinson ADC for Distributed Motor Controller Application

    Page(s): 1236 - 1242
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    The radiation robustness of a newly designed Wilkinson analog-to-digital converter (ADC) is being investigated. The ADC is a front-end design block within a cold capable, analog sense, application-specific integrated circuit (ASIC) manufactured using the IBM 0.5 μm silicon germanium (SiGe) BiCMOS 5HP process. The ASIC is part of a next-generation, cold capable, distributed motor controller architecture, which is a candidate for the next generation of Mars rovers. Its main function is to interface with various sensor types to monitor motor health (i.e., temperature, mechanical stress, pressure). While relatively well-hardened against total ionizing dose and destructive single-event latchup, the ADC showed some SEU (SET) sensitivity that is heavily dependent on its input channel configuration. For this study, we used a combination of experiments (pulsed-laser) and Cadence mixed-mode SEE simulations to explain the heavy ion irradiation results. We concluded that ADC input impedance configuration should be carefully controlled in the design of radiation-hardened systems for space. View full abstract»

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  • Fisher Information Analysis of Depth-of-Interaction Estimation in Double-Sided Strip Detectors

    Page(s): 1243 - 1251
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    In very-high-spatial-resolution gamma-ray imaging applications, such as preclinical PET and SPECT, estimation of 3D interaction location inside the detector crystal can be used to minimize parallax error in the imaging system. In this work, we investigate the effect of bias voltage setting on depth-of-interaction (DOI) estimates for a semiconductor detector with a double-sided strip geometry. We first examine the statistical properties of the signals and develop expressions for likelihoods for given gamma-ray interaction positions. We use Fisher Information to quantify how well (in terms of variance) the measured signals can be used for DOI estimation with different bias-voltage settings. We performed measurements of detector response versus 3D position as a function of applied bias voltage by scanning with highly collimated synchrotron radiation at the Advanced Photon Source at Argonne National Laboratory. Experimental and theoretical results show that the optimum bias setting depends on whether or not the estimated event position will include the depth of interaction. We also found that for this detector geometry, the z-resolution changes with depth. View full abstract»

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  • Energy Calibration of the NewSUBARU Storage Ring for Laser Compton-Scattering Gamma Rays and Applications

    Page(s): 1252 - 1258
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    Using γ-ray beams produced in the inverse Compton scattering between CO2 laser photons and relativistic electrons, we have calibrated electron beam energies in the nominal energy range 550-974 MeV at the synchrotron radiation facility New-SUBARU. The laser Compton-scattering (LCS) γ-ray beams were produced at energies from 561 to 1728 keV and detected with a high-purity germanium detector. The electron beam energies were determined by reproducing the full energy peaks of the γ-ray beams by Monte Carlo simulations. The accuracy of the calibration is (5.5 - 9.4) ×10 - 5. The reproducibility of the electron beam energy is excellent in an independent injection and deceleration. The present energy calibration of the electron beams offers a standard for the energy calibration of high-energy LCS γ-ray beams produced with a Nd:YVO4 laser. As applications of the energy calibration, we investigated the energy linearity of a 3.5'' × 4.0'' LaBr3(Ce) detector in the response to γ-rays at energies up to 10 MeV and the energy profile of the high-energy LCS γ-ray beams. View full abstract»

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  • GeFRO: A New Charge Sensitive Amplifier Design for Wide Bandwidth and Closed-Loop Stability Over Long Distances

    Page(s): 1259 - 1268
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1504 KB) |  | HTML iconHTML  

    A new approach was developed for the design of front-end circuits for semiconductor radiation detectors. The readout scheme is a charge sensitive amplifier, split between a very front-end stage (input transistor, feedback resistor and capacitor) located close to the detector and a remote second stage located far from the detector. The element of novelty, with respect to similar configurations, is the fact that the connecting links between the very front-end and the second stage are made with transmission lines. As a result, wide bandwidth and closed-loop stability are maintained even if the distance between the very front-end and the second stage is much larger than usual, up to tens of meters. The circuit was named GeFRO for Germanium front-end, and was tested with a BEGe detector from Canberra. Timing resolutions of 20 ns (open loop) and 185 ns (closed loop with 60 ° phase margin) were obtained with 10 m long cables between the very front-end and the second stage. The noise of the circuit after a 10 μs Gaussian shaping was close to 160 e- RMS with an input capacitance of 26 pF. View full abstract»

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  • A Self-Triggered Column-Level ADC for CMOS Pixel Sensors in High Energy Physics

    Page(s): 1269 - 1277
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1141 KB) |  | HTML iconHTML  

    CMOS pixel sensors (CPS) for the future linear collider vertex detector (VXD) have strict requirements on their analog readout electronics, particularly on the analog-to-digital converter (ADC). This paper presents a low-power and small-area 4-bit column-level ADC for the CMOS pixel sensor, foreseen to equip the outer layers of the VXD. The ADC employs a self-triggered timing and completes the conversion by performing a multi-bit/step approximation. Accounting the fact that in the outer layers, the hit density is in the order of a few per thousand, this ADC is designed to operate in two modes: active mode and inactive mode. The average energy and total capacitance are significantly reduced by a power-gating control and a switching network, respectively. The ADC is fabricated in a 0.35 μm CMOS process with a pixel pitch of 35 μm. It is implemented with 48 columns in a sensor prototype. Each column ADC occupies an area of 35×545 μm2. The measured temporal noise and fixed pattern noise (FPN) are 0.94 and 0.30 mV, respectively. The power consumption, at a 3-V supply and 6.25-MS/s sampling rate, equals to 486 μW in its inactive mode, which is by far the most frequent. This value rises to 714 μW in case of the active mode. These computations indicate an average power consumption of each column in the order of 487 μW, assuming a typical occupancy of ~ 0.5% in the whole sensor. Its DNL and INL are 0.49/-0.28 and 0.29/-0.20 least significant bit, respectively. View full abstract»

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  • Development of a Fast Timing Counter with a Monolithic MPPC Array

    Page(s): 1278 - 1283
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (744 KB) |  | HTML iconHTML  

    We developed a timing counter with a monolithic array of multi-pixel photon counters (MPPCs) coupled to a 10 ×12.6 ×24 mm3 plastic scintillator. A signal of the MPPC was processed and its fast components were amplified by a developed readout circuit to improve the timing. The performances of the counter were evaluated by electrons with energies of 855 MeV. A set of the MPPC based scintillation counter and a PMT based reference counter achieved the TOF resolution less than 80 ps ( σ). The gain was almost constant up to the count rate of 170 kHz. View full abstract»

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  • Spatially-Aware Temporal Anomaly Mapping of Gamma Spectra

    Page(s): 1284 - 1289
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (883 KB) |  | HTML iconHTML  

    For security, environmental, and regulatory purposes it is useful to continuously monitor wide areas for unexpected changes in radioactivity. We report on a temporal anomaly detection algorithm which uses mobile detectors to build a spatial map of background spectra, allowing sensitive detection of any anomalies through many days or months of monitoring. We adapt previously-developed anomaly detection methods, which compare spectral shape rather than count rate, to function with limited background data, allowing sensitive detection of small changes in spectral shape from day to day. To demonstrate this technique we collected daily observations over the period of six weeks on a 0.33 square mile research campus and performed source injection simulations. View full abstract»

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  • Optimal Viewing Angle Determination for Multiple Vessel Segments in Coronary Angiographic Image

    Page(s): 1290 - 1303
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2417 KB) |  | HTML iconHTML  

    Angiographic image is the perspective projection of the whole body from a 3D space to a 2D imaging plane, in which X-ray is used. As such, topological vasculature information has been lost. In 2D angiograms, foreshortening and overlapping are commonly observed in tubular-like structures. Hence, an optimum viewing angle should be determined to observe an interesting vessel segment (IVS) or an interesting vessel bifurcation (IVB) with minimized foreshortening and overlapping from a limited number of angiographic images. In this study, a novel integrated optimization method is proposed to calculate the optimum viewing angle. In the proposed method, the irregular shape and inter-branch distance of vasculatures are considered. Furthermore, three optimized conditions, including projection foreshortening rate, projection stenosis rate, and projection overlapping rate, are designed and integrated to determine the optimum viewing angle in a single vessel segment. The three conditions, including projection foreshortening, projection stenosis, and projection adjacent spacing rates, are also designed to optimize the viewing angle of bifurcations. To evaluate the performance of the proposed method, we simulated an angiographic image based on X-ray propagating principle by integrating 3D coronary artery tree models and the respective CT volume data. Experimental results demonstrate that the proposed method is very effective and robust; hence, this method can be used to determine the optimum viewing angle of IVS or IVB with irregular stenosis. The proposed method can also help physicians observe the branching structure or stenosis clearly in clinical practice. View full abstract»

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  • A Cognitive Filter to Automatically Determine Scintillation Detector Materials and to Control Their Spectroscopic Resolution During Temperature Changes

    Page(s): 1304 - 1310
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    The shape of the nuclear signal from scintillators contains information about the detection material from which it originated and its current temperature. A digital filter for this type of signals is presented that automatically extracts both of these pieces of information from the shape of the signals and controls the temperature dependency of the resolution by continuous adaption to this shape. Hereby, nuclear signals are a-priori modelled by an all-pole filter. The concept combines a deconvolution approach based on this model with a least-mean-squares iteration. Beneath the iteration, there is a continuous assessment of the signal shape where the mean-squared distance between the assumed shape and measured shape acts as control parameter for the resolution. From the information stored inside the dynamic filter parameters, the material characteristics are retrieved to identify the detector material. An implementation into a multi-channel-analyser is shown and the technique is verified under real-world environmental conditions. View full abstract»

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  • Bilateral PIN Diode for Fast Neutron Dose Measurement

    Page(s): 1311 - 1315
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (871 KB) |  | HTML iconHTML  

    A silicon-based bilateral diode for fast neutron dose measurement is presented to take advantage of vertical and lateral current distributions and to achieve high uniform current distribution. The structure is designed to place rectangle p+ and n+ contacts on each side of the n-Si wafer. Diodes with different structure parameters are fabricated and the sensitivity to neutron dose is measured. It is found that, in this research, the increase in the lateral space between the two contacts can effectively increase sensitivity. Furthermore, the decrease of the contact length and the increase of current density can also increase sensitivity. The measured sensitivity data are verified with the model. View full abstract»

    Open Access
  • The Model for Calculating the Type A Measurement Uncertainty of GM Counters from the Aspect of Device Miniaturization

    Page(s): 1316 - 1325
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    In accordance with the general trend of the miniaturization of electronic components and devices, this paper shows the model for calculating the type A measurement uncertainty of the Geiger-Mueller (GM) counter. As a consequences of device miniaturization, reduction of the GM counting tube size results in a change in the reliability of the GM counter for radiation detection. Based on the enlargement law applied to distributions of extreme values (such as the Weibull distribution) the paper shows the derived theoretical expression which describes the trend of the type A measurement uncertainty followed by the GM counting tube reduction. In an experimental procedure, carried out under well controlled laboratory conditions, the area and volume effects caused by the change in the counting tube size were observed separately. Experiments were carried out on commercial counting tubes as well as on in-house counting tube models, both made in cylindrical geometry. The experimental results obtained, which are in compliance with the theoretically derived model, indicated that the random variable pulse rate, which belongs to the normal distribution due to its nature, with regard to modelling according to area and volume enlargement probability law, should be treated by the three-parameter Weibull distribution. All the obtained results in the paper have been explained based on elementary processes of electrical discharge in gases and are significant for engineering practice since they define the trend of GM counter measurement uncertainty of type A, and thus its functionality as a radiation instrument, during the course of device miniaturization. View full abstract»

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  • Pulse-Shape Discrimination of Alpha Particles of Different Specific Energy-Loss With Parallel-Plate Avalanche Counters

    Page(s): 1326 - 1332
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    Parallel-plate avalanche counters have long been recognized as timing detectors for heavily ionizing particles. However, these detectors suffer from a poor pulse-height resolution which limits their capability to discriminate between different ionizing particles. In this paper, a new approach for discriminating between charged particles of different specific energy-loss with avalanche counters is demonstrated. We show that the effect of the self-induced space-charge in parallel-plate avalanche counters leads to a strong correlation between the shape of output current pulses and the amount of primary ionization created by the incident charged particles. The correlation is then exploited for the discrimination of charged particles with different energy-losses in the detector. The experimental results obtained with α-particles from an 241Am α-source demonstrate a discrimination capability far beyond that achievable with the standard pulse-height discrimination method. View full abstract»

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  • Externally-Modulated Electro-Optically Coupled Detector Architecture for Nuclear Physics Instrumentation

    Page(s): 1333 - 1339
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (772 KB) |  | HTML iconHTML  

    A new laser-based externally-modulated electro-optically coupled detector (EOCD) architecture is being developed to enable high-density readout for radiation detectors with accurate analog radiation pulse shape and timing preservation. Unlike digital conversion before electro-optical modulation, the EOCD implements complete analog optical signal modulation and multiplexing in its detector front-end. The result is a compact, high performance detector readout that can be both radiation tolerant and immune to magnetic fields. In this work, the feasibility of EOCD was explored by constructing a two-wavelength laser-based externally-modulated EOCD, and testing analog pulse shape preservation and wavelength-division multiplexing (WDM) crosstalk. Comparisons were first made between the corresponding initial pulses and the electro-optically coupled analog pulses. This confirmed an excellent analog pulse preservation over ~ 29% of the modulator's switching voltage range. Optical spectrum analysis revealed less than -14 dB crosstalk with 1.2 nm WDM wavelength bandgap, and provided insight on experimental conditions that could lead to increased inter-wavelength crosstalk. Further discussions and previous research on the radiation tolerance and magnetic field immunity of the candidate materials were also given, and quantitative device testing is proposed in the future. View full abstract»

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  • Real-Time, Fast Neutron Coincidence Assay of Plutonium With a 4-Channel Multiplexed Analyzer and Organic Scintillators

    Page(s): 1340 - 1348
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    The design, principle of operation and the results of measurements made with a four-channel organic scintillator system are described. The system comprises four detectors and a multiplexed analyzer for the real-time parallel processing of fast neutron events. The function of the real-time, digital multiple-channel pulse-shape discrimination analyzer is described together with the results of laboratory-based measurements with 252Cf, 241Am-Li and plutonium. The analyzer is based on a single-board solution with integrated high-voltage supplies and graphical user interface. It has been developed to meet the requirements of nuclear materials assay of relevance to safeguards and security. Data are presented for the real-time coincidence assay of plutonium in terms of doubles count rate versus mass. This includes an assessment of the limiting mass uncertainty for coincidence assay based on a 100 s measurement period and samples in the range 0-50 g. Measurements of count rate versus order of multiplicity for 252Cf and 241Am-Li and combinations of both are also presented. View full abstract»

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  • Power-Level Control for MHTGRs with Time-Delay in Helium Temperature Measurement

    Page(s): 1349 - 1359
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2308 KB) |  | HTML iconHTML  

    The modular high temperature gas-cooled reactor (MHTGR), which has the inherent safety feature, high thermal efficiency and satisfactory economic feasibility, can be applied for electricity and process heat production. Power-level control is an important technique for providing both the stable operation and load-following performance. Since the coolant temperature sensors of an MHTGR are usually installed near the primary side of the corresponding steam generator, there must be time-delay effect in the feedback loop of the coolant temperatures. Moreover, the measurement signal transducing may also induce time-delay effect. Therefore, it is meaningful to give the power-level control design method by considering this time-delay effect. In this paper, a simple output-feedback power-level control is proposed for the MHTGRs by using the delayed measurement signal of average reactor coolant temperature. In the aspect of theoretical analysis, a sufficient condition, under which it is well guaranteed that this newly-built power-level control is a globally asymptotic stabilizer, is firstly given. In the aspect of verification, numerical simulation results not only verify the feasibility of the theoretical results but also show the relationship between the performance and values of parameters of this novel power-level controller. The meaning of this work lies in two aspects. The first one is deeply revealing the relationship between the closed-loop stability and values of the controller parameters. The second one is giving the approach of designing a simple and effective power-level control strategy to suppress the negative influence induced by the time-delay in the feedback loop of the coolant temperatures. View full abstract»

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  • Kalman Filter-Based Dynamic Compensator for Vanadium Self Powered Neutron Detectors

    Page(s): 1360 - 1368
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1237 KB) |  | HTML iconHTML  

    Large nuclear reactors employ a wide variety of in-core detectors to determine the neutron flux distribution within the core. Among them Vanadium SPNDs are extensively used for flux mapping applications due to their accuracy. However, the slow response characteristics of Vanadium detectors precludes their direct use for reactor protection and regulation applications. Neverthless, by overcoming their inherent time delay, it is possible to use them in such applications. Moreover, benefits offered by Vanadium SPNDs like better life span, simple response characteristics, easiness in handling the replaced SPNDs etc., make them desirable candidates for such applications. Therefore, a method to improve the response time of Vanadium SPNDs would enable them to be utilized for reactor control applications as well as to fulfill core monitoring and surveillance requirements. In this paper, a Kalman filter-based compensator is proposed for online dynamic compensation of Vanadium SPND. Moreover, compensated flux obtained by Kalman filter is compared with the compensated flux obtained from existing dynamic compensators i.e. Direct Inversion and Tustin, and robustness of proposed algorithm is studied. The compensator is validated using the plant data collected from the 540 MWe PHWR units in India. It is established that the compensated Vanadium SPND signals are in very good agreement with the prompt Cobalt SPND signals. This puts the possibility of using Vanadium SPNDs in lieu of Cobalt SPNDs for reactor protection and regulation applications. View full abstract»

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  • Pixelated Geiger-Mode Avalanche Photo-Diode Characterization Through Dark Current Measurement

    Page(s): 1369 - 1375
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (921 KB) |  | HTML iconHTML  

    PIXELATED Geiger-mode avalanche photodiodes (PPDs), often called silicon photomultipliers (SiPMs) are emerging as an excellent replacement for traditional photomultiplier tubes (PMTs) in a variety of detectors, especially those for subatomic physics experiments, which requires extensive test and operation procedures in order to achieve uniform responses from all the devices. In this paper, we show for two PPD brands, Hamamatsu MPPC and SensL SPM, that at room temperature, the dark noise rate, breakdown voltage and rate of correlated avalanches can be inferred from the sole measure of dark current as a function of operating voltage, hence greatly simplifying the characterization procedure. We introduce a custom electronics system that allows measurement for many devices concurrently, hence allowing rapid testing and monitoring of many devices at low cost. Finally, we show that the dark current of Hamamastu Multi-Pixel Photon Counter (MPPC) is rather independent of temperature at constant operating voltage, hence the current measure cannot be used to probe temperature variations. On the other hand, the MPPC current can be used to monitor light source conditions in DC mode without requiring strong temperature stability, as long as the integrated source brightness is comparable to the dark noise rate. View full abstract»

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  • Dose Rate and Bias Effects on COTS Array CCDs Induce Dark Signals Increase

    Page(s): 1376 - 1380
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (636 KB) |  | HTML iconHTML  

    The experiments of dose rate and bias effects on commercial-off-the-shelf array charge-coupled devices (CCDs) are presented. The dark signal ( VD) is calculated with the output signal voltages measured at different integration times when no light is incident on the CCDs. The dark signal voltages ( VD) versus the total dose at the dose rates of 0.01, 0.1, 1.0, 10.0, and 50 rad(Si)/s are compared. Annealing tests are performed to eliminate the time-dependent effects. Degradation levels were found to depend on the dose rates. The CCDs are divided into two groups-with one group biased and the other unbiased during 60Coγ irradiation. The biased CCDs are shown to degrade more severely than the unbiased CCDs. View full abstract»

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