Showing papers in "IEEE Transactions on Nuclear Science in 2005"
CERN1
TL;DR: In this article, the authors studied the TID response of transistors and isolation test structures in a 130 nm commercial CMOS technology and demonstrated that the thin gate oxide of the transistors is extremely tolerant to dose, charge trapping at the edge of the transistor still leads to leakage currents and, for the narrow channel transistors, to significant threshold voltage shift.
Abstract: The study of the TID response of transistors and isolation test structures in a 130 nm commercial CMOS technology has demonstrated its increased radiation tolerance with respect to older technology nodes. While the thin gate oxide of the transistors is extremely tolerant to dose, charge trapping at the edge of the transistor still leads to leakage currents and, for the narrow channel transistors, to significant threshold voltage shift-an effect that we call Radiation Induced Narrow Channel Effect (RINCE).
398Â citations
TL;DR: This paper shows how the new floating point GPUs can be exploited to perform both analytical and iterative reconstruction from X-ray and functional imaging data, and decompose three popular three-dimensional (3D) reconstruction algorithms into a common set of base modules.
Abstract: The task of reconstructing an object from its projections via tomographic methods is a time-consuming process due to the vast complexity of the data. For this reason, manufacturers of equipment for medical computed tomography (CT) rely mostly on special application specified integrated circuits (ASICs) to obtain the fast reconstruction times required in clinical settings. Although modern CPUs have gained sufficient power in recent years to be competitive for two-dimensional (2D) reconstruction, this is not the case for three-dimensional (3D) reconstructions, especially not when iterative algorithms must be applied. The recent evolution of commodity PC computer graphics boards (GPUs) has the potential to change this picture in a very dramatic way. In this paper we will show how the new floating point GPUs can be exploited to perform both analytical and iterative reconstruction from X-ray and functional imaging data. For this purpose, we decompose three popular three-dimensional (3D) reconstruction algorithms (Feldkamp filtered backprojection, the simultaneous algebraic reconstruction technique, and expectation maximization) into a common set of base modules, which all can be executed on the GPU and their output linked internally. Visualization of the reconstructed object is easily achieved since the object already resides in the graphics hardware, allowing one to run a visualization module at any time to view the reconstruction results. Our implementation allows speedups of over an order of magnitude with respect to CPU implementations, at comparable image quality.
296Â citations
TL;DR: In this paper, the results of a series of comparisons for the evaluation of Geant4 electromagnetic processes with respect to United States National Institute of Standards and Technologies (NIST) reference data are presented.
Abstract: The Geant4 Simulation Toolkit provides an ample set of physics models describing electromagnetic interactions of particles with matter. This paper presents the results of a series of comparisons for the evaluation of Geant4 electromagnetic processes with respect to United States National Institute of Standards and Technologies (NIST) reference data. A statistical analysis was performed to estimate quantitatively the compatibility of Geant4 electromagnetic models with NIST data; the statistical analysis also highlighted the respective strengths of the different Geant4 models.
197Â citations
TL;DR: The results showed that the memory architecture is critical in affecting the single-bit EDAC effectiveness and the predominant MBU shape is strongly influenced by the vertical and horizontal distance of the active nodes of the memory cells.
Abstract: Multi-bit upset (MBU) events collected from accelerated soft error rate (SER) measurements performed with a quasi-monoenergetic neutron beam were analyzed with a threefold purpose. The first goal was to qualitatively assess the applicability and effectiveness of single-bit Error Detection And Correction algorithms and circuits (EDAC). The second goal was to investigate the relationship with the memory core P-well tapping scheme. And the third goal was to identify "preferred" MBU shapes. The results showed that the memory architecture is critical in affecting the single-bit EDAC effectiveness. Also, it was put in evidence that the tapping scheme is very effective in reducing the MBU rate. And finally it was noted that the predominant MBU shape is strongly influenced by the vertical and horizontal distance of the active nodes of the memory cells.
184Â citations
TL;DR: In this article, the authors measured basic properties of three ceramic Y/sub 3/Al/sub 5/O/sub 12/ (YAG) scintillators doped with Ce to a concentration of 0.5, 0.05, and 0.13.
Abstract: We measured basic properties of three ceramic Y/sub 3/Al/sub 5/O/sub 12/ (YAG) scintillators doped with Ce to a concentration of 0.5, 0.05, and 0.005 mol%, in comparison with a monocrystalline YAG scintillator with unknown amount of Ce doping. First, optical transparency and emission spectra were investigated. We confirmed that the transparency of the ceramics is comparable to that of the monocrystalline one (/spl sim/80%) in wavelengths longer than /spl sim/500 nm. The ceramics did not show an indication of lattice defects which is present in the monocrystalline YAG. Then the response to /spl gamma/-rays was studied using a phototube as a scintillation light detector. The 0.5 mol% sample exhibited the highest light yield (/spl sim/40% of CsI), with an energy resolution of about 7.2% at /sup 137/Cs 662 keV photoabsorption peak. The optimum Ce concentration for a /spl sim/2 mm thick ceramic YAG was determined to be /spl sim/0.1 mol%. Using the delayed coincidence method, the principal time constant of the ceramic YAGs was measured as /spl sim/80 ns. By irradiating 5.49 MeV /spl alpha/-particles, the /spl alpha/-ray to /spl gamma/-ray light yield ratio of the ceramic YAGs was found to depend negatively on the amount of Ce; namely, 0.28, 0.20, and 0.13 in the increasing order of the Ce concentration. The 200-1000 keV intrinsic background of the 0.5 mol% ceramic was /spl sim/10/sup -5/ counts/s/cm/sup 3/, indicating that it is not significantly contaminated by radioactive impurities.
173Â citations
TL;DR: In this article, a drift-diffusion collection at an NFET transistor in conjunction with parasitic bipolar conduction in nearby PFET transistors is shown to cause upsets in a commercial 0.25 /spl mu/m 10-T SEE hardened SRAM cell.
Abstract: A novel mechanism for upset is seen in a commercially available 0.25 /spl mu/m 10-T SEE hardened SRAM cell. Unlike traditional multiple node charge collection in which diffusions near a single event strike collect the deposited carriers, this new mechanism involves direct drift-diffusion collection at an NFET transistor in conjunction with parasitic bipolar conduction in nearby PFET transistors. The charge collection with the parasitic bipolar conduction compromise the SEE hardened design, thus causing upsets. The mechanism was identified using laser testing and three-dimensional TCAD simulations.
161Â citations
TL;DR: In this article, a Geant4-based Monte-Carlo transport code was used to simulate heavy ion irradiation using a SEU hardened SRAM and the results showed that materials external to the sensitive volume can affect the experimentally measured cross-section curve.
Abstract: Heavy ion irradiation was simulated using a Geant4 based Monte-Carlo transport code. Electronic and nuclear physics were used to generate statistical profiles of charge deposition in the sensitive volume of an SEU hardened SRAM. Simulation results show that materials external to the sensitive volume can affect the experimentally measured cross-section curve.
161Â citations
TL;DR: In this article, a methodology for estimating the proton and heavy ion static saturation cross-sections for multi-bit upsets in Xilinx field-programmable gate arrays is presented.
Abstract: This paper provides a methodology for estimating the proton and heavy ion static saturation cross-sections for multi-bit upsets (MBUs) in Xilinx field-programmable gate arrays and describes a methodology for determining MBUs' effects on triple-modular redundancy protected circuits. Experimental results are provided.
159Â citations
TL;DR: In this paper, a new scintillator, cerium bromide (CeBr3), has been developed for gamma-ray spectroscopy using the Bridgman process.
Abstract: In this paper, we report on a new scintillator, cerium bromide (CeBr3), for gamma-ray spectroscopy. Crystals of this scintillator have been grown using Bridgman process. In this material Ce 3+ is an intrinsic constituent as well as a luminescence center for the scintillation process. Samples of CeBr3 showed high light output (~68000 photons/MeV) and fast decay constant (~17 ns). Furthermore, they exhibited excellent energy resolution for gamma-ray detection. For example, energy resolution of <4% full width at half maximum (FWHM) has been achieved using this scintillator for 662 keV photons (137Cs source) at room temperature. High timing resolution (<200 ps-FWHM) has been recorded with CeBr3-photomultiplier (PMT) and BaF2-PMT detectors operating in coincidence using 511 keV positron annihilation gamma-ray pairs
140Â citations
TL;DR: The clinical feasibility of in-beam PET for proton therapy monitoring is strongly supported and the possible extraction of valuable clinical information as particle range in-vivo, irradiation field position, and even local deviations from the dose prescription on the basis of the comparison between measured and predicted activity distributions is indicated.
Abstract: Positron emission tomography (PET) is currently the only feasible method for in-situ and noninvasive three-dimensional monitoring of the precision of the treatment in highly conformal ion therapy. Its positive clinical impact has been proven for fractionated carbon ion therapy of head and neck (H&N) tumors at the experimental facility at the Gesellschaft fur Schwerionenforschung (GSI), Darmstadt, Germany. Following previous promising experiments, the possible extension of the method to the monitoring of proton therapy has been investigated further in extensive in-beam measurements at GSI. Millimeter accuracy for verification of the lateral field position and for the most challenging issue of range monitoring has been demonstrated in monoenergetic and spread-out Bragg-peak (SOBP) proton irradiation of polymethyl methacrylate (PMMA) targets. The irradiation of an inhomogeneous phantom with tissue equivalent inserts in combination with further dynamic analysis has supported the extension of such millimeter precision to real clinical cases, at least in regions of interest for low perfused tissues. All the experimental investigations have been reproduced by the developed modeling rather well. This indicates the possible extraction of valuable clinical information as particle range in-vivo, irradiation field position, and even local deviations from the dose prescription on the basis of the comparison between measured and predicted activity distributions. Hence, the clinical feasibility of in-beam PET for proton therapy monitoring is strongly supported.
133Â citations
TL;DR: In this paper, a new and inexpensive method of measuring the depth of interaction (DOI) in /spl gamma-ray detectors with large-sized scintillation crystals was proposed.
Abstract: We have studied a new and inexpensive method of measuring the depth of interaction (DOI) in /spl gamma/-ray detectors with large-sized scintillation crystals. This method takes advantage of the strong correlation between the width of the undisturbed light-distribution in continuous crystals and the /spl gamma/-ray's DOI. In order to quantify the dependence of the distribution's width with respect to the DOI, we first studied an analytical model of the light-distribution and tested it by means of Monte Carlo (MC) simulations of the light transport inside the crystal. Further we present an inexpensive modification of the commonly used charge division circuit that allows analog and instantaneous computation of the light-distribution's second moment without affecting the determination of the centroid. This redesigned resistor network is based on the position-sensitive proportional counter (DPC) readout and allows, together with position sensitive photo-detectors, the additional measurement of the light-distribution's standard-deviation /spl sigma/. We tested the proposed circuit using the design-tool OrCAD and found the signal sufficiently large for digitalization. Finally, we conducted MC simulations of a realistic Positron Emission Tomography (PET) detector module setup that mimic a continuous Lu/sub 2/SiO/sub 5/:Ce/sup 3+/ (LSO) crystal of dimensions 40/spl times/40/spl times/10 mm/sup 3/ together with the new large area position-sensitive photo multiplier tube (PSPMT) H8500 from Hamamatsu. The influence of Compton scattering on the DOI determination was also estimated by MC simulations. Altogether, we obtained /spl les/ 5 mm DOI resolution. PACS: 87.57.Ce, 87.58.Fg, 87.62.+n, 07.85.-m.
TL;DR: Hardening-by-design techniques to mitigate the effect of single event transients (SET) using guard-gates are developed in this article, where the authors show that the designs using guard gates are less susceptible to single event hits.
Abstract: Hardening-by-design techniques to mitigate the effect of single-event transients (SET) using guard-gates are developed. Design approaches for addressing combinational logic hits and storage cell hits are presented. Simulation results show that the designs using guard-gates are less susceptible to single-event hits. Area, power, and speed penalty for guard-gate designs for combinational logic are found to be minimal. For latches, the area penalty is higher but speed penalty is minimal.
TL;DR: In this paper, a three-dimensional (3D) technology computer-aided design (TCAD) model was used to simulate charge collection at multiple nodes and guard contacts were shown to mitigate the charge collection and to more quickly restore the well potential in PMOS devices.
Abstract: A three-dimensional (3D) technology computer-aided design (TCAD) model was used to simulate charge collection at multiple nodes. Guard contacts are shown to mitigate the charge collection and to more quickly restore the well potential, especially in PMOS devices. Mitigation of the shared charge collection in NMOS devices is accomplished through isolation of the P-wells using a triple-well option. These techniques have been partially validated through heavy-ion testing of three versions of flip-flop shift register chains.
TL;DR: In this article, the impact of properly modeling the equivalent series noise and gate capacitance of the MOSFET is presented, and it is shown that the enhanced model produces a different resolution estimate and input MOS-FET optimization result.
Abstract: The optimization of the input MOSFET for charge amplifiers in deep submicron technologies is discussed. After a review of the traditional approach, the impact of properly modeling the equivalent series noise and gate capacitance of the MOSFET is presented. It is shown that the enhanced MOSFET model, when compared to the classical, produces a different resolution estimate and input MOSFET optimization result. The minimum channel length and the maximum allocated power are not always the best choice in terms of resolution. Also, in an optimized front-end, the low frequency noise contribution to the Equivalent Noise Charge may depend on the time constant of the filter. As an example, results from the commercial TSMC 0.25 mum CMOS technology are reported
TL;DR: In this article, the authors present an analysis of the SEU effects in circuits hardened according to Triple Module Redundancy to investigate the possibilities of successfully applying TMR to designs mapped on commercial-off-the-shelf SRAM-based FPGAs, which are not radiation hardened.
Abstract: Non radiation-hardened SRAM-based Field Programmable Gate Arrays (FPGAs) are very sensitive to Single Event Upsets (SEUs) affecting their configuration memory and thus suitable hardening techniques are needed when they are intended to be deployed in critical applications. Triple Module Redundancy is a known solution for hardening digital logic against SEUs that is widely adopted for traditional techniques (like ASICs). In this paper we present an analysis of the SEU effects in circuits hardened according to the Triple Module Redundancy to investigate the possibilities of successfully applying TMR to designs mapped on commercial-off-the-shelf SRAM-based FPGAs, which are not radiation hardened. We performed different fault-injection experiments in the FPGA configuration memory implementing TMR designs and we observed that the percentage of SEUs escaping TMR could reach 13%. In this paper we report detailed evaluations of the effects of the observed failure rates, and we proposed a first step toward an improved TMR implementation.
TL;DR: In this article, the effect of proton energy on single-event latchup (SEL) in present-day SRAMs is investigated over a wide range of Proton energies and temperature.
Abstract: The effect of proton energy on single-event latchup (SEL) in present-day SRAMs is investigated over a wide range of proton energies and temperature. SRAMs from five different vendors were irradiated at proton energies from 20 to 500 MeV and at temperatures of 25/spl deg/ and 85/spl deg/C. For the SRAMs and radiation conditions examined in this work, proton energy SEL thresholds varied from as low as 20 MeV to as high as 490MeV. To gain insight into the observed effects, the heavy-ion SEL linear energy transfer (LET) thresholds of the SRAMs were measured and compared to high-energy transport calculations of proton interactions with different materials. For some SRAMs that showed proton-induced SEL, the heavy-ion SEL threshold LET was as high as 25MeV-cm/sup 2//mg. Proton interactions with Si cannot generate nuclear recoils with LETs this large. Our nuclear scattering calculations suggest that the nuclear recoils are generated by proton interactions with tungsten. Tungsten plugs are commonly used in most high-density ICs fabricated today, including SRAMs. These results demonstrate that for system applications where latchups cannot be tolerated, SEL hardness assurance testing should be performed at a proton energy at least as high as the highest proton energy present in the system environment. Moreover, the best procedure to ensure that ICs will be latchup free in proton environments may be to use a heavy-ion source with LETs /spl ges/40 MeV-cm/sup 2//mg.
TL;DR: In this paper, the dynamic single-event upset (SEU) cross section of an FPGA design is characterized in terms of its persistent and non-persistent components.
Abstract: This paper introduces a new way to characterize the dynamic single-event upset (SEU) cross section of an FPGA design in terms of its persistent and nonpersistent components. An SEU in the persistent cross section results in a permanent interruption of service until reset. An SEU in the nonpersistent cross section causes a temporary interruption of service. These cross sections have been measured for several designs using fault-injection and proton testing. Some FPGA applications may realize increased reliability at lower costs by focusing SEU mitigation on just the persistent cross section.
TL;DR: A new analytical approach is described to estimate the dependability of TMR designs implemented on SRAM-based FPGAs that is able to predict the effects of single event upsets with the same accuracy of fault injection but at a fraction of the fault-injection's execution time.
Abstract: In order to deploy successfully commercially-off-the-shelf SRAM-based FPGA devices in safety- or mission-critical applications, designers need to adopt suitable hardening techniques, as well as methods for validating the correctness of the obtained designs, as far as the system's dependability is concerned. In this paper we describe a new analytical approach to estimate the dependability of TMR designs implemented on SRAM-based FPGAs that, by exploiting a detailed knowledge of FPGAs architectures and configuration memory, is able to predict the effects of single event upsets with the same accuracy of fault injection but at a fraction of the fault-injection's execution time.
TL;DR: Geant4 Radiation Analysis for Space (GRAS) as discussed by the authors is a modular, extendable tool for space environment effects simulation, including cumulative ionizing and NIEL doses, effects to humans, charging, fluence and transient effects in three-dimensional geometry models.
Abstract: Geant4 Radiation Analysis for Space (GRAS) is a modular, extendable tool for space environment effects simulation. Analyses include cumulative ionizing and NIEL doses, effects to humans, charging, fluence and transient effects in three-dimensional geometry models.
TL;DR: In this paper, the transient response of 50-nm gate length fully and partially depleted SOI and bulk devices to pulsed laser and heavy ion microbeam irradiations was investigated.
Abstract: This paper investigates the transient response of 50-nm gate length fully and partially depleted SOI and bulk devices to pulsed laser and heavy ion microbeam irradiations. The measured transient signals on 50-nm fully depleted devices are very short, and the collected charge is small compared to older 0.25-/spl mu/m generation SOI and bulk devices. We analyze in detail the influence of the SOI architecture (fully or partially depleted) on the pulse duration and the amount of bipolar amplification. For bulk devices, the doping engineering is shown to have large effects on the duration of the transient signals and on the charge collection efficiency.
TL;DR: In this paper, the authors demonstrate the high radiation tolerance of a Raman distributed fiber optic temperature sensor, up to total gamma doses in excess of 300 kGy, using a double-ended configuration and commercially available optical fibers.
Abstract: Raman Distributed Temperature Sensors (RDTS) are attractive for the monitoring of large structures in nuclear power plants such as containment structures and coolant loop systems. We demonstrate the high radiation tolerance of a Raman distributed fiber optic temperature sensor, up to total gamma doses in excess of 300 kGy, using a double-ended configuration and commercially-available optical fibers.
TL;DR: The detection capabilities of individual sensors and the scalability of detection with sensor density are studied; near the detection limit, increasing the number of sensors can accrue subproportional network sensitivity; and the consequences of different levels of background radiation are investigated.
Abstract: Detection limits of sensor networks for moving radioactive sources are characterized, using Bayesian methods in conjunction with computer simulation. These studies involve point sources moving at constant velocity, emulating vehicular conveyance on a straight road. For networks involving ten nodes, respective Bayesian methods are implementable in real time. We probe the increased computational requirements incurred by larger numbers of nodes and source trajectory parameters. The complexity appears quadratic in the number of nodes and, also, numerous trajectory parameters may be used. We investigate the consequences of different levels of background radiation. Simulations are shown to be useful for ranking candidate node layouts. We study the detection capabilities of individual sensors and the scalability of detection with sensor density; near the detection limit, increasing the number of sensors can accrue subproportional network sensitivity.
TL;DR: A generally applicable self test circuit approach implemented in IBM's 5AM SiGe process is demonstrated, and its ability to capture complex error signatures during circuit operation at data rates exceeding 5 Gbit/s is described.
Abstract: SEE testing at multi-Gbit/s data rates has traditionally involved elaborate high speed test equipment setups for at-speed testing. We demonstrate a generally applicable self test circuit approach implemented in IBM's 5AM SiGe process, and describe its ability to capture complex error signatures during circuit operation at data rates exceeding 5 Gbit/s. Comparisons of data acquired with FPGA control of the CREST ASIC versus conventional bit error rate test equipment validate the approach. In addition, we describe SEE characteristics of the IBM 5AM process implemented in five variations of the D flip-flop based serial register. Heavy ion SEE data acquired at angles follow the traditional RPP-based analysis approach in one case, but deviate by orders on magnitude in others, even though all circuits are implemented in the same 5AM SiGe HBT process.
TL;DR: A database of realistic simulated PET data accounting for inter-subject anatomical variability is generated and has the merit to provide the community with realistic simulated 3D and 4D PET studies for commonly used radiotracers.
Abstract: We present here the features and validation results of a Monte Carlo-based PET simulation platform designed to address the increasing need of simulated studies. The simulation tool, named PET-SORTEO, includes i) the generation of the raw data in accordance with both the numerical phantom description as well as with the scanner geometry and physical characteristics, and ii) the correction and reconstruction of the raw data. Validation results show that the platform reliably reproduces the image formation processes and includes correctly the sources of noise and biases. This platform allows for parallel processing and complete dynamic PET studies, including emission and transmission data, can be generated within few hours using a cluster of machines. Using PET-SORTEO, we generated a database of realistic simulated PET data accounting for inter-subject anatomical variability. This database has the merit to provide the community with realistic simulated 3D and 4D PET studies for commonly used radiotracers. This database as well as information about PET-SORTEO can be found at the address: http://sorteo.cermep.fr.
TL;DR: The Compton camera as discussed by the authors consists of six layered double-sided Si Strip detectors and CdTe pixel detectors, which are read out with low noise analog ASICs, VA32TAs.
Abstract: We are developing a Compton camera based on Si and CdTe semiconductor imaging devices with high energy resolution. In this paper, results from the most recent prototype are reported. The Compton camera consists of six layered double-sided Si Strip detectors and CdTe pixel detectors, which are read out with low noise analog ASICs, VA32TAs. We obtained Compton reconstructed images and spectra of line gamma-rays from 122 keV to 662 keV. The energy resolution is 9.1 keV and 14 keV at 356 keV and 511 keV, respectively.
TL;DR: MADPET-II is a novel high-resolution, high-sensitivity three-dimensional lutetium oxyorthosilicate avalanche photodiode small animal PET scanner with a unique detector design and readout that creates new possibilities for data processing and analysis.
Abstract: MADPET-II is a novel high-resolution, high-sensitivity three-dimensional lutetium oxyorthosilicate avalanche photodiode small animal PET scanner with a unique detector design and readout that creates new possibilities for data processing and analysis. The scanner consists of a ring of dual-layer detector modules (O71 mm), each containing a 4/spl times/8 array of 2/spl times/2/spl times/6mm/sup 3/ (front) and 2/spl times/2/spl times/8 mm/sup 3/ (back) LSO crystals that are each optically isolated and coupled one-to-one to a monolithic 4/spl times/8 APD array. Signals from each channel are individually processed using fully-integrated 16-channel, low noise, charge sensitive preamplifiers and custom integrated electronics that include a four channel shaping amplifier, peak detector and non-delay line CFD. Analog-to-digital converters and time-to-digital converters digitise the pulse height and time-stamp each event, and data are stored exclusively in list mode format. Two 32-channel detector blocks were tested in a coincidence and in a dual-layer configuration. Coincidences were sorted post-acquisition in software, allowing for maximum flexibility in the data processing. Monte Carlo simulations have calculated the system spatial resolution to be 1.1 mm FWHM. Average energy resolution for a single detector block ranged from 20.2% FWHM to 23.9% FWHM. System pulse height linearity was measured, and all channels responded with R/sup 2/>0.9988 (Pearson correlation coefficient). Intrinsic uniformity for each detector block ranged from 2.0% to 4.8% (400 keV threshold). Overall system timing resolution was measured to be 10.2 ns FWHM, with individual LORs having time resolutions as low as 4.5 ns FWHM.
TL;DR: In this article, the results from experiments performed on Lu/sub 2/SiO/sub 5/Ce (LSO:Ce) samples were obtained from various crystal batches having significantly different properties.
Abstract: This work presents the results from experiments performed on Lu/sub 2/SiO/sub 5/:Ce (LSO:Ce). It looks for potential correlations of light yield nonproportionality and other scintillation properties such as intrinsic energy resolution with thermoluminescence properties. The analyzed samples were chosen from various crystal batches having significantly different properties. Single crystal LSO:Ce samples were coupled to an XP2020Q photomultiplier and to large area avalanche photodiodes and measured as a function of /spl gamma/-ray energy between 14.7 and 1770 keV at room temperature and also near liquid nitrogen temperature. To explain the experimental results obtained from spectrometric methods, the properties of the samples were further studied using thermoluminescence techniques within the temperature range from 250K to 600K. The relationships between data obtained from these two types of experiments are reported.
TL;DR: In this paper, the electron and hole charge transport properties of semi-insulating CdTe:Cl grown by the Travelling Heater Method (THM) were investigated, with room temperature values of 880 cm2 /Vs for electrons and 90 cm2/Vs for holes.
Abstract: We report the electron and hole charge transport properties of semi insulating CdTe:Cl grown by the Travelling Heater Method (THM). An alpha-particle Time of Flight (TOF) method was used to measure electron and hole drift mobility, with room temperature values of 880 cm2 /Vs for electrons and 90 cm2/Vs for holes. The variation in mobility was also investigated as a function of temperature, with electron and hole mobilities at 190 K of 1150 cm2 /Vs and 20 cm2/Vs respectively. Using a Hecht analysis the electron and hole mobility-lifetime products were also measured over the same temperature range, with values at room temperature of 8times10-4 cm2/V and 7times10-5 cm 2/V respectively. Time-resolved ion beam induced charge (IBIC) imaging was used to produce micrometer resolution maps of electron drift mobility and signal amplitude, which showed excellent spatial uniformity
TL;DR: In this paper, a 3D position-sensitive CdZnTe (CZT) gamma-ray spectrometers employing new VAS3.1/TAT3 ASIC readouts were developed and tested.
Abstract: Three-dimensional (3-D) position-sensitive CdZnTe (CZT) gamma-ray spectrometers employing new VAS3.1/TAT3 ASIC readouts were developed and tested. Each spectrometer is a 1.5 /spl times/ 1.5 /spl times/ 1 cm/sup 3/ CdZnTe crystal with 11 /spl times/ 11 pixellated anodes wire-bonded to the readout electronics using an intermediate ceramic substrate with plated-through-via. The signals from the anode pixels and the cathode were all read out using these ASICs. The pixel position provides the lateral coordinates of interactions, while the cathode to anode signal ratio and electron drift times are used to obtain interaction depths. Using the 3-D position information, the variation in weighting potential, electron trapping and material nonuniformity can be accounted for to the scale of the position resolution, /spl sim/1.27 /spl times/ 1.27 /spl times/ 0.2 mm. The new VAS3.1/TAT3 ASIC has less gain and baseline drift, lower cross-talk noise, more uniform thresholds, better linearity and better timing resolution than our previous VAS2/TAT2 system. For example, the 32 keV K X-ray from a /sup 137/Cs source was observed for the first time. Two 3-D position sensitive CZT spectrometers were tested and both achieved better than 1% FWHM energy resolution (at 662 keV, room temperature operation, with an uncollimated source) for single-pixel events. The experimental results for these two 3-D position sensitive CZT spectrometer systems are presented and discussed.