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Nuclear Science, IEEE Transactions on

Issue 4 • Date Aug. 2010

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Displaying Results 1 - 25 of 44
  • Table of contents

    Page(s): C1 - 2146
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  • IEEE Transactions on Nuclear Science publication information

    Page(s): C2
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    Freely Available from IEEE
  • ATCA Advanced Control and Data Acquisition Systems for Fusion Experiments

    Page(s): 2147 - 2154
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (359 KB) |  | HTML iconHTML  

    The next generation of large-scale physics experiments will be highly complex, raise new challenges in the field of control and automation systems and demand well integrated, interoperable set of tools with a high degree of automation. Fusion experiments will face similar needs and challenges. In nuclear fusion activities, e.g., JET and other devices, the demand has been to develop front-end electronics with large output bandwidth and data processing Multiple-Input-Multiple-Output (MIMO) controllers with efficient resource sharing between control tasks on the same unit and massive parallel computing capabilities. Future systems, such as ITER, are envisioned to be more than an order of magnitude larger than those of today. Fast control plant systems based on embedded technology with higher sampling rates and more stringent real-time requirements (feedback loops with sampling rates > 1 kHz) will be demanded. Furthermore, in ITER, it is essential to ensure that control loss is a very unlikely event and more challenging will be providing robust, fault tolerant, reliable, maintainable, secure and operable control systems. ATCA (Advanced Telecommunications Computing Architecture) is the most promising architecture to substantially enhance the performance and capability of existing standard systems delivering high throughput as well as high availability. Leveraging on ongoing activities at European fusion facilities, e.g., JET and COMPASS, this contribution will detail the control and data acquisition needs and challenges of the fusion community, justify the option for ATCA and, in the process, build the case for establishing ATCA as an instrumentation standard. View full abstract»

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  • X-Ray Filter Design and Its Evaluation in Dual-Energy X-Ray Absorptiometry (DXA)

    Page(s): 2155 - 2158
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (577 KB) |  | HTML iconHTML  

    This paper reports a new X-ray beam geometry to acquire two separated polychromatic X-rays as well as two separated fan beams using parallel different filters built in a single collimator. This newly designed X-ray spectrum was generated by a single X-ray shot but had the effect of double X-ray exposure. The two separated filters were used side by side. The first filter for the low energy spectra was 0.5 mm thick erbium and the second filter for the high energy spectra was composed of two layers of a 0.8 mm of copper and 0.4 mm of rhodium. This combination of filters showed excellent performance of X-ray beam hardening regardless of the bone thickness in the soft tissue under DXA conditions. View full abstract»

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  • Design Studies for a High Resolution Cold Cavity Beam Position Monitor

    Page(s): 2159 - 2166
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (848 KB) |  | HTML iconHTML  

    In order to preserve a low emittance beam along the ~11 km long main linacs of the International Linear Collider (ILC), precise monitoring and control of the beam orbit is mandatory. A resolution <; 1 μm is required for the beam position monitors (BPM), which are located inside the cryomodules, i.e. operated at cryogenic temperatures. By using the electromagnetic field simulation programs (CST Studio Suite), we have designed a high resolution cold cavity BPM, operating in the L-Band at a 1.3 GHz dipole-mode frequency. This enables the measurement of the beam position with a Project-X like beam structure, as well as with ILC beam parameters at the superconducting RF test accelerator in the Fermilab New Muon Lab (NML) building. The results of the design studies predicts a resolution potential of a few hundred nanometers with a signal decay time of 50 ns. View full abstract»

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  • Latchup Topology for Pixel Readout Using Commercial Transistors

    Page(s): 2167 - 2172
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    The stimulated ignition of latchup effects caused by external radiation has till now proved to be a hidden hazard. However this paper presents the effect in a new light-as a new approach for detecting particles by means of a solid-state device susceptible to latchup effects. This device can also be used as a circuit for reading a sensor's signal by leaving off-circuit sensing capabilities. Given that MOS transistors are widely used in microelectronics devices and sensors, the latchup-based cell is proposed as a new structure for future applications in particle detection, in the amplification of sensor signals and also in radiation monitoring. View full abstract»

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  • High Performance Analog Front-End for Digital Spectroscopy

    Page(s): 2173 - 2177
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    In any digital spectroscopy system the signal has to be properly conditioned before sampling by means of analog circuitry. The paper presents an analog fully-differential front-end, with digitally adjustable gain and offset, wide dynamic amplitude of input signals, low noise and linearity error less than 100 ppm. The analog section has been designed bearing in mind also multichannel applications and, consequently, taking into particular account power dissipation, physical size of hosting PCB, and allowing the system to operate in presence of electromagnetic noise, while at the same time minimizing its own radiated emissions. The proposed analog stage is designed bearing in mind a general-purpose architecture, both for X and γ -ray applications. View full abstract»

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  • Vertically Integrated Circuits at Fermilab

    Page(s): 2178 - 2186
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    The exploration of vertically integrated circuits, also commonly known as 3D-IC technology, for applications in radiation detection started at Fermilab in 2006. This paper examines the opportunities that vertical integration offers by looking at various 3D designs that have been completed by Fermilab. The emphasis is on opportunities that are presented by through silicon vias (TSV), wafer and circuit thinning, and finally fusion bonding techniques to replace conventional bump bonding. Early work by Fermilab has led to an international consortium for the development of 3D-IC circuits for High Energy Physics. For the first time, Fermilab has organized a 3D MPW run, to which more than 25 different designs have been submitted by the consortium. View full abstract»

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  • Geant4 Simulation of the New ALC  {\mu }{\rm SR} Spectrometer

    Page(s): 2187 - 2195
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    Monte Carlo simulation programs based on the Geant4 package have become indispensable tools in modern particle physics. Following the advances in muon-spin rotation (μSR) instrumentation we have written a simulation code, MUSRSIM, currently in use in the development and optimisation of contemporary μSR spectrometers. MUSRSIM was employed for optimising the design of a new type of avoided level crossing (ALC) instrument, which is characterised by the exclusive use of Geiger-mode avalanche photodiodes instead of the standard photomultiplier tubes. The simulation code allowed us to study in detail the influence of the detector geometry, of the initial muon beam properties, and (to a limited extent) of the electronic signal processing on the predicted spectra. The good agreement between the simulation results and the measured data, validates MUSRSIM as a reliable software tool also for future instrument development work. View full abstract»

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  • Track-Induced Clustering in Position Sensitive Detector Characterization

    Page(s): 2196 - 2199
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    The formation of clusters in the data analysis of position-sensitive detectors is traditionally based on signal-to-noise ratio thresholds. For detectors with a very low signal-to-noise ratio, e.g., as a result of radiation damage, the total collected charge obtained from the clusters is biased to the greater signal values resulting from the thresholds. In this paper an unbiased method to measure the charge collection of a silicon strip detector in a test beam environment is presented. The method is based on constructing the clusters on test detectors around the impact point of the reference track. View full abstract»

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  • CCD Base Line Subtraction Algorithms

    Page(s): 2200 - 2204
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (515 KB) |  | HTML iconHTML  

    High statistics astronomical surveys require photometric accuracy on a few percent level. The accuracy of sensor calibration procedures should match this goal. The first step in calibration procedures is the base line subtraction. The accuracy and robustness of different base line subtraction techniques used for Charge Coupled Device (CCD) sensors are discussed. View full abstract»

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  • A New Technique for Gaseous Radiation Detectors: The Multigrid High-Pressure Xenon Gas Proportional Scintillation Counter

    Page(s): 2205 - 2209
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (338 KB) |  | HTML iconHTML  

    A new technique is presented for high-pressure gaseous radiation detectors leading to pulse amplitudes at least one order of magnitude larger than in ionization-chamber-based gamma-ray detectors. The technique uses room-temperature pure Xe or Xe-based gaseous mixtures at pressures of about 5-20 bar (or higher) to detect ionizing radiation in a multigrid high-pressure gas proportional scintillation counter (MGHP-GPSC) with a CsI deposit as the photocathode in direct contact with the gas, with no optical windows. The detector relies on secondary scintillation as the amplification stage followed by photoelectron production in a CsI photocathode layer. Experimental results are presented for a small prototype filled with pure Xe up to 5 bar, showing that the principle of operation of the detector works. The maximum detector gain obtained so far is about 10. View full abstract»

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  • Measurements of Induced Charge Profile in RPC With Submilli-Strips

    Page(s): 2210 - 2214
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    It is necessary to understand the spread and spatial distribution of charge induced on readout strips or pad in RPC to utilize it for a tracking/imaging device. We have measured the profile of induced charge on submilli-size strips for cosmic ray events. The spatial spread of the charge was measured to be about 10 mm in the configuration of our study. The result was verified measuring the lateral size of the streamer using the associated optical images. View full abstract»

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  • Neutron Detection With Gamma-Ray Spectrometers for Border Security Applications

    Page(s): 2215 - 2219
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (353 KB) |  | HTML iconHTML  

    Development of technologies for neutron detection that do not require 3He is important because the supply of 3He is very limited, and the cost of the gas is becoming prohibitive for many applications. This study evaluates the ability to detect neutron sources with gamma-ray spectrometers that are already present in many radiation measurement systems. Detection is based on count rates for gamma rays in the 3 to 8 MeV range, which are produced by the emission of fission gamma rays and neutron capture reactions in vehicles and their cargo. For materials in the normal stream of commerce, gamma rays above 3 MeV are produced only by sources that also emit neutrons. Therefore, unless the gamma-ray count rate is high enough to produce excessive random pileup, the detection of high-energy gamma rays provides an unambiguous indication of the presence of a neutron source. As part of this investigation, several shields that are suitable for use in radiation portals were constructed and characterized for their abilities to produce additional high-energy, neutron-capture gamma rays. A shield (composed of alternating layers of polyethylene and steel) enhances the ability to detect neutrons without producing detrimental effects for gamma-ray measurements. Calculations show that when shielded by neutron-detection-enhancing materials, NaI detectors can be as sensitive to the presence of a concealed neutron source as moderated 3He detectors. View full abstract»

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  • Distribution of Absorbed Dose in Cone-Beam Breast Computed Tomography: A Phantom Study With Radiochromic Films

    Page(s): 2220 - 2229
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1237 KB) |  | HTML iconHTML  

    Cone-Beam Breast Computed Tomography (CBBCT) of the pendant breast with dedicated scanners is an experimental 3D X-ray imaging technique for breast cancer diagnosis under evaluation in comparison to conventional two-view 2-D mammography of the compressed breast. In CBBCT it is generally assumed that a more uniform distribution of the radiation dose to the breast volume can be obtained, with respect to mammography, at equal Mean Glandular Dose (MGD) levels. In fact, in CBBCT the X-ray beam rotates for 360 deg around the breast, while in each mammography view the breast is irradiated from one side only. Using a CBBCT laboratory scanner developed by our group, we have measured the distribution of the radiation dose in a hemi-ellipsoidal PMMA breast phantom of 14 cm diameter simulating the average uncompressed breast, using radiochromic films type XR-SP inserted at mid-plane in the phantom. The technique factors were 80 kVp (5.6 mm Al Half Value Layer), tube load in the range 23-100 mAs, for an air kerma at isocenter in the range 4.7-20 mGy, for a calculated MGD in the range 3.5-15 mGy for a 14 cm diameter breast of 50% glandularity. Results indicate that the dose decreases from the periphery to the center of the phantom, and that along a transverse profile, the relative dose variation Δ = ((edge-center)/center) is up to (25 ±4)% at a distance of 80 mm from the nipple. As for the relative dose variation along the phantom longitudinal axis, the maximum value at middle of the phantom measured is δ = ((nipple-chest wall)/chest wall) = -(15 ±4)%, indicating that the dose decreases from the chest wall toward the nipple. The values of the parameters Δ and δ depend also on the height of the X-ray tube focal spot with respect to the phantom vertex (nipple). Results are in rough agreement with similar previous determinations using thermoluminescence dosimeters. View full abstract»

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  • Time-Spectral Analysis Methods for Spent Fuel Assay Using Lead Slowing-Down Spectroscopy

    Page(s): 2230 - 2238
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (789 KB) |  | HTML iconHTML  

    Nondestructive techniques for measuring the mass of fissile isotopes in spent nuclear fuel is a considerable challenge in the safeguarding of nuclear fuel cycles. A nondestructive assay technology that could provide direct measurement of fissile mass, particularly for the plutonium (Pu) isotopes, and improve upon the uncertainty of today's confirmatory methods is needed. Lead slowing-down spectroscopy (LSDS) has been studied for the spent fuel application previously, but the nonlinear effects of assembly self shielding (of the interrogating neutron population) have led to discouraging assay accuracy for realistic pressurized water reactor fuels. In this paper, we describe the development of time-spectral analysis algorithms for LSDS intended to overcome these self-shielding effects. The algorithm incorporates the tabulated energy-dependent cross sections from key fissile and absorbing isotopes, but leaves their mass as free variables. Multi-parameter regression analysis is then used to directly calculate not only the mass of fissile isotopes in the fuel assembly (e.g., Pu-239, U-235, and Pu-241), but also the mass of key absorbing isotopes such as Pu-240 and U-238. Modeling-based assay results using this self-shielding relationship indicate that LSDS has the potential to directly measure fissile isotopes with less than 5% average relative error for pressurized water reactor assemblies with burnup as high as 60 GWd/MTU. Shortcomings in the initial self-shielding model and potential improvements to the formulation are described. View full abstract»

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  • Measurement of Neutron Yields From {\rm UF}_{4}

    Page(s): 2239 - 2246
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    We have performed measurements of neutron production from UF4 samples using liquid scintillator as the detector material. Neutrons and gamma rays were separated by a multichannel digital pulse shape discriminator, and the neutron pulse-height spectra were unfolded using sequential least-squares optimization with an active set strategy. The unfolded spectra were compared to estimates calculated with the SOURCES 4C code. View full abstract»

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  • Signatures and Methods for the Automated Nondestructive Assay of {\rm UF}_{6} Cylinders at Uranium Enrichment Plants

    Page(s): 2247 - 2253
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1523 KB) |  | HTML iconHTML  

    International Atomic Energy Agency (IAEA) inspectors currently perform periodic inspections at uranium enrichment plants to verify UF6 cylinder enrichment declarations. Measurements are typically performed with handheld high-resolution sensors on a sampling of cylinders taken to be representative of the facility's entire cylinder inventory. These measurements are time-consuming, expensive, and assay only a small fraction of the total cylinder volume. An automated nondestructive assay system capable of providing enrichment measurements over the full volume of the cylinder could improve upon current verification practices in terms of manpower and assay accuracy. The 185-keV emission from U-235 is utilized in today's cylinder measurements, but augmenting this “traditional” signature with more-penetrating “non-traditional” signatures could help to achieve full-volume assay in an automated system. This paper describes the study of non-traditional signatures that include neutrons produced by F-19 (α, n) reactions (spawned primarily from U-234 alpha emission) and the high-energy gamma rays (extending up to 8 MeV) induced by those neutrons when they interact in the cylinder wall and nearby materials. The potential of these non-traditional signatures and assay methods for automated cylinder verification is explored using field measurements on a small population of cylinders ranging from 2.0% to 5% in U-235 enrichment. The standard deviation of the non-traditional high-energy gamma-ray assay approach was 4.7% relative to the declared cylinder enrichments; the standard deviation of the traditional enrichment meter approach using a well-collimated high-resolution spectrometer was 4.3%. The prospect of using the non-traditional high-energy gamma-ray signature in concert with the traditional 185-keV signature to reduce the uncertainty of automated cylinder assay is discussed. View full abstract»

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  • A Comprehensive Model of the Response of Silicon Photomultipliers

    Page(s): 2254 - 2266
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (652 KB) |  | HTML iconHTML  

    The response of a silicon photomultiplier (SiPM) to optical signals is inherently nonproportional due to saturation, afterpulsing, and crosstalk. Existing models of the SiPM response do not account for all of these effects, and therefore, these models are not sufficiently accurate for many applications. In this work, a comprehensive model of the SiPM response is developed that is generally applicable to exponentially decaying light pulses and that can be simplified in the case of very short (e.g., laser) light pulses. The model accounts for the total number and the temporal distribution of the incident photons as well as for the relevant SiPM parameters, viz. the recovery time, afterpulsing, crosstalk, and their cross correlations. The model is shown to correspond well with measurements on a SiPM-based scintillation detector. Furthermore, it is shown to be in agreement with several cases for which the SiPM response is known a priori. Having thus validated the model, its use is demonstrated by predicting the response of the Hamamatsu multipixel photon counter (MPPC) S10362-33-050C SiPM to several different scintillators. View full abstract»

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  • Crosstalk Study of the Single-Photon Response of a Flat-Panel PMT for the RICH Upgrade at LHCb

    Page(s): 2267 - 2272
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    The ring imaging Cherenkov (RICH) detector at LHCb is now read out by hybrid photon detectors. In view of its upgrade, a possible option is the adoption of the flat-panel photon multiplier tube (PMT). An important issue for good reconstruction of the Cherenkov rings is a negligible level of crosstalk. We have experimentally studied the crosstalk from the 16 × 16-pixels Hamamatsu H9500 PMT. Results have shown that, for the single-photon response, the statistics tied to the small number of electrons generated at the first dynode of the PMT chain (a few units) leads to a number of crosstalk signals that are a small fraction of the fired pixel. With the H9500, in a Cherenkov ring, only one or two pixels are expected to generate crosstalk. As a consequence, crosstalk cannot be considered a limit in the use of the H9500 for the upgrade of the RICH at LHCb. View full abstract»

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  • Timing Performances of Large Area Silicon Photomultipliers Fabricated at STMicroelectronics

    Page(s): 2273 - 2279
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (766 KB) |  | HTML iconHTML  

    In this paper the results of charge and timing resolution characterization realized at Fermi National Accelerator Laboratory (Fermilab) on 3.5 × 3.5 mm2 Silicon PhotoMultipliers fabricated at STMicroelectronics Catania R&D clean room facilities are presented. The device consists of 4900 microcells and has a geometrical fill factor of 36%. Timing measurements were realized at different wavelengths by varying the overvoltage and the temperature applied to the photodetector. The results shown in this manuscript demonstrate that the device, in spite of its large area, exhibits relevant features in terms of low dark current density, fast timing and very good single photoelectron resolution. All these characteristics can be considered very appealing in view of the utilization of this technology in applications requiring detectors with high timing and energy resolution performances. View full abstract»

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  • Performance Measurements of CMOS Position Sensitive Solid-State Photomultipliers

    Page(s): 2280 - 2286
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1373 KB) |  | HTML iconHTML  

    We have designed position sensitive solid-state photomultipliers (PS-SSPM) using a complementary metal-oxide-semiconductor (CMOS) process. Four variations of the PS-SSPM design were fabricated, however, one of the variations did not function properly. The remaining three functional variations were characterized for their energy and coincidence timing resolution, spatial resolution, and scintillator array imaging. Each PS-SSPM is 1.5 × 1.5 mm2, however, each device has different micro-pixel geometries and different micro-pixel electrical readout for event position sensing. When coupled to 1 × 1 × 20 mm3 LYSO, the energy resolution at 511 keV was measured as a function of bias. The same LYSO scintillator was used to measure the coincidence timing resolution. Results between the PS-SSPMs varied from 2.0 ns to 0.9 ns (FWHM) at 511 keV. Spatial resolution studies were conducted using a focused (15 μm beam spot diameter) pulsed 635 nm diode laser. For each PS-SSPM, the X and Y spatial resolution was measured between 70 and 75 μm (FWHM). Lastly, scintillator array images were generated using a CsI:Tl and LYSO array having 300 × 300 μm2 and 500 × 500 μm2 pixels respectively. View full abstract»

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  • A Radiation Hard Digital Monolithic Pixel Sensor for the EUDET-JRA1 Project

    Page(s): 2287 - 2293
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (726 KB) |  | HTML iconHTML  

    In the framework of the EUDET-JRA1 project (European Detector R&D towards the International Linear Collider), which consists of design, realization and implantation of a high resolution beam digital telescope, based on Monolithic Active Pixel Sensors (MAPS), an intermediate digital chip sensor, MIMOSA22, has already been delivered with good detection performances. Although this intermediate chip has fulfilled all the initial requirements of the project, it was admitted that radiation tolerance behavior of the sensor could be improved, especially if the high precision telescope is used later in a hadron testbeam infrastructure. For this purpose, a new version of the sensor, MIMOSA22-BIS, has been designed, with several improved pixel architectures, and using the same AMS 0.35 μm opto process of the sensor MIMOSA22. This paper will be focused on tests performed in laboratory conditions using a 55Fe source, and tests performed in CERN-SPS, using a 120 GeV pion beam, in order to characterize detection performances of the chip with MIPs, before and after ionizing irradiation. View full abstract»

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  • Investigation of Irradiated Silicon Detectors by Edge-TCT

    Page(s): 2294 - 2302
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (553 KB) |  | HTML iconHTML  

    A Transient Current Technique (TCT) utilizing an IR laser with 100 ps pulse width and beam diameter of FWHM = 8 μm was used to evaluate non-irradiated and irradiated p-type silicon micro-strip detectors. The beam was parallel with the surface and perpendicular to the strips (Edge-TCT) so that the electron hole pairs were created at known depth in the detector. Induced current pulses were measured in one of the strips. The pulse shapes were analyzed in a new way, which does not require the knowledge of effective trapping times, to determine drift velocity, charge collection and electric field profiles in heavily irradiated silicon detectors. The profiles were studied at different laser beam positions (depth of carrier generation), voltages and fluences up to 5·1015 neutrons cm-2. A strong evidence for charge multiplication at high voltages was found with the detector irradiated to the highest fluence. View full abstract»

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  • Trapping of Holes and Excitons in Scintillators: CsI and {\rm LaX}_{3} ( {\rm X}={\rm Cl} , Br)

    Page(s): 2303 - 2308
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (360 KB) |  | HTML iconHTML  

    We present computational results for trapping of polarons and excitons in undoped CsI, LaCl3 and LaBr3 , using plane-wave-pseudopotential density functional theory with Hartree-Fock exact exchange. The optimized VK center and STE in CsI is a distortion of two iodine atoms from the lattice to form an interstitial bound I2- molecule, consistent with previous theoretical and experimental results. In both LaCl3 and LaBr3, the relaxed STE configuration involves only one displaced halide ion, and does not form an X2-. The calculated luminescence energy for the STE in LaCl3 and LaBr3 is 4.1 and 3.7 eV, respectively. View full abstract»

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