Showing papers in "IEEE Transactions on Nuclear Science in 2012"

Soft Error Susceptibilities of 22 nm Tri-Gate Devices

Abstract: We report on measured radiation-induced soft error rates (SER) of memory and logic devices built in a 22 nm high-k metal gate bulk Tri-Gate technology. Our results demonstrate excellent single event upset (SEU) scaling benefits of tri-gate devices. For cosmic radiation, SEU SER reduction levels of the order of are observed relative to 32 nm planar devices, while for alpha-particles, the measured SEU SER benefit is in excess of . Similar improvements are observed for Tri-Gate combinational logic and memory array multi-cell upset (MCU) rates. Reduced SER (RSER) device SER performances (relative to standard, non -RSER devices) are on par or better than that of tested 32 nm planar devices. Finally, a novel, efficient SER reduction design called RTS is introduced.

Reflectivity Spectra for Commonly Used Reflectors

Abstract: Monte Carlo simulations play an important role in developing and evaluating the performance of radiation detection systems. To accurately model a reflector in an optical Monte Carlo simulation, the reflector's spectral response has to be known. We have measured the reflection coefficient for many commonly used reflectors for wavelengths from 250 nm to 800 nm. The reflectors were also screened for fluorescence and angular distribution changes with wavelength. The reflectors examined in this work include several polytetrafluoroethylene (PTFE) reflectors, Spectralon, GORE diffuse reflector, titanium dioxide paint, magnesium oxide, nitrocellulose filter paper, Tyvek paper, Lumirror, Melinex, ESR films, and aluminum foil. All PTFE films exhibited decreasing reflectivity with longer wavelengths due to transmission. To achieve >;0.95 reflectivity in the 380 to 500 nm range, the PTFE films have to be at least 0.5 mm thick-nitrocellulose is a good alternative if a thin diffuse reflector is needed. Several of the reflectors have sharp declines in reflectivity below a cut-off wavelength, including TiO2 (420 nm), ESR film (395 nm), nitrocellulose (330 nm), Lumirror (325 nm), and Melinex (325 nm). PTFE-like reflectors were the only examined reflectors that had reflectivity above 0.90 for wavelengths below 300 nm. Lumirror, Melinex, and ESR film exhibited fluorescence. Lumirror and Melinex are excited by wavelengths between 320 and 420 nm and have their emission peaks located at 440 nm, while ESR film is excited by wavelengths below 400 nm and the emission peak is located at 430 nm. Lumirror and Melinex also exhibited changing angular distributions with wavelength.

A Comprehensive Model to Predict the Timing Resolution of SiPM-Based Scintillation Detectors: Theory and Experimental Validation

Abstract: Silicon photomultipliers (SiPMs) are expected to replace photomultiplier tubes (PMTs) in several applications that require scintillation detectors with excellent timing resolution, such as time-of-flight positron emission tomography (TOF-PET). However, the theory about the timing resolution of SiPM-based detectors is not yet fully understood. Here we propose a comprehensive statistical model to predict the timing resolution of SiPM-based scintillation detectors. It incorporates the relevant SiPM-related parameters (viz. the single cell electronic response, the single cell gain, the charge carrier transit time spread, and crosstalk) as well as the scintillation pulse rise and decay times, light yield, and energy resolution. It is shown that the proposed model reduces to the well-established Hyman model for timing with PMTs if the number of primary triggers (photoelectrons in case of a PMT) is Poisson distributed and crosstalk and electronic noise are negligible. The model predictions are validated by measurements of the coincidence resolving times (CRT) for 511 keV photons of two identical detectors as a function of SiPM bias voltage, for two different kinds of scintillators, namely LYSO:Ce and LaBr3:5%Ce. CRTs as low as 138 ps ± 2 ps FWHM for LYSO:Ce and 95 ps ± 3 ps FWHM for LaBr3:5%Ce were obtained, demonstrating the outstanding timing potential of SiPM-based scintillation detectors. These values were found to be in good agreement with the predicted CRTs of 140 ps FWHM and 95 ps FWHM, respectively. Utilizing the proposed model, it can be shown that the CRTs obtained in our experiments are mainly limited by photon statistics while crosstalk, electronic noise and signal bandwidth have relatively little influence.

Radiation Effects in Commercial 1200 V 24 A Silicon Carbide Power MOSFETs

Abstract: In 2011, after many years of research and development SiC power MOSFETs became available in the commercial marketplace. This paper presents the results of Co60 total ionizing dose (TID) effects for the new high power-high current 24 A SiC devices irradiated at room temperature and 125°C. These commercially available components remained operational after a radiation dose of more than 100 krad. However, gamma ray irradiation gave rise to changes in current-voltage and capacitance-voltage characteristics. Specifically, threshold voltage decreased, resulting in increased current drive. We also observed rises in interface state densities, as well as input, output and reverse transfer capacitances with increasing accumulated doses.

Pulse Shape Discrimination With Selected Elpasolite Crystals

Abstract: In recent years, a number of materials from the elpasolite crystal family have been under development for either or both gamma ray and neutron detection. The scintillators show good energy resolution and thermal neutron detection efficiency. The latter is achieved due to the fact, that the selected compositions contain Li-6 ions. In order to effectively and reliably register both types of radiation, it is necessary to separate them through particle identification schemes. This can be accomplished using either pulse height or/and pulse shape discrimination, with the latter being more reliable. In this paper, we summarize our work and provide current status of pulse shape discrimination in the selected elpasolite scintillators. These include Cs2LiYCl6 (CLYC), Cs2LiLaCl6(CLLC), Cs2LiLaBr6(CLLB), and Cs2LiYBr6(CLYB).

Crystal Growth and Scintillation Properties of Ce Doped ${\rm Gd}_{3}({\rm Ga},{\rm Al})_{5}{\rm O}_{12}$ Single Crystals

Abstract: Ce1%, 2% and 3% doped Gd3(Ga,Al)5O12 (GAGG) single crystals were grown by the Cz method. Luminescence and scintillation properties were measured. Light yield change along the growth direction and effects of Ce concentration on scintillation properties in Ce:GAGG were studied. Ce3+ 5d-4f emission within 520-530 nm was observed in the Ce:GAGG crystals. The Ce1%:GAGG sample with 3×3×1 mm size showed the highest light yield of 46000 photon/MeV. The energy resolution was 7.8%@662 keV. With increasing solidification fraction, the LY were decreased. It is proposed that the increase of Ga concentration along the growth direction is the main cause of the decrease of LY. The scintillation decay times were accelerated with increasing Ce concentration in the Ce:GAGG crystals. The scintillation decay times were 92.0 ns, 79.1 ns and 68.3 ns in the Ce1, 2 and 3% GAGG, respectively.

The Origins of Scintillator Non-Proportionality

Abstract: Recent years have seen significant advances in both theoretically understanding and mathematically modeling the underlying causes of scintillator non-proportionality. The core cause is that the interaction of radiation with matter invariably leads to a non-uniform ionization density in the scintillator, coupled with the fact that the light yield depends on the ionization density. The mechanisms that lead to the luminescence dependence on ionization density are incompletely understood, but several important features have been identified, notably Auger-like processes (where two carriers of excitation interact with each other, causing one to de-excite non-radiatively), the inability of excitation carriers to recombine (caused either by trapping or physical separation), and the carrier mobility. This paper reviews the present understanding of the fundamental origins of scintillator non-proportionality, specifically the various theories that have been used to explain non-proportionality.

Dynamic Time Over Threshold Method

Abstract: The time over threshold (TOT) method has several advantages over direct pulse height analysis based on analog to digital converters (ADCs). A key advantage is the simplicity of the conversion circuit which leads to a high level of integration and a low power consumption. The TOT technique is well suited to build multi-channel readout systems for pixelated detectors as described in our previous work that also exploits the Pulse Width Modulation (PWM) method. The main limitation of the TOT technique is that the relation between the input charge to be measured and the width of the encoded pulse is strongly non-linear. Dynamic range limitation is also an issue. To address these aspects, we propose a new time over threshold conversion circuit where the threshold of the comparator is dynamically changed instead of being constant. We call this scheme the “dynamic TOT method”. We show that it improves linearity and dynamic range. It also shortens the duration of measured pulses leading to higher counting rates. We present a short analysis that explains how the ideal linear input charge to TOT transfer function can theoretically be obtained. We describe the results obtained with a test circuit built from discrete components and present several of the spectrums obtained with crystal detectors and a radioactive source. The proposed method can be used for applications like Positron Emission Tomography (PET) that require moderate energy resolution.

Radiation Effects in Pinned Photodiode CMOS Image Sensors: Pixel Performance Degradation Due to Total Ionizing Dose

Abstract: Several Pinned Photodiode (PPD) CMOS Image Sensors (CIS) are designed, manufactured, characterized and exposed biased to ionizing radiation up to 10 kGy(SiO2 ). In addition to the usually reported dark current increase and quantum efficiency drop at short wavelengths, several original radiation effects are shown: an increase of the pinning voltage, a decrease of the buried photodiode full well capacity, a large change in charge transfer efficiency, the creation of a large number of Total Ionizing Dose (TID) induced Dark Current Random Telegraph Signal (DC-RTS) centers active in the photodiode (even when the Transfer Gate (TG) is accumulated) and the complete depletion of the Pre-Metal Dielectric (PMD) interface at the highest TID leading to a large dark current and the loss of control of the TG on the dark current. The proposed mechanisms at the origin of these degradations are discussed. It is also demonstrated that biasing (i.e., operating) the PPD CIS during irradiation does not enhance the degradations compared to sensors grounded during irradiation.

Initial Assessment of the Effects of Radiation on the Electrical Characteristics of ${\rm TaO}_{\rm x}$ Memristive Memories

Abstract: Radiation-induced effects on the electrical characteristics of TaOx memristive (or redox) memory are experimentally assessed. 10 keV x-ray irradiation is observed to cause switching of the memristors from high to low resistance states, as well as functional failure due to cumulative dose. Gamma rays and 4.5 MeV energy protons are not observed to cause significant change in resistance state or device function at levels up to 2.5 Mrad(Si) and 5 Mrad(Si) protons, respectively. 105 MeV and 480 MeV protons cause switching of the memristors from high to low resistance states in some cases, but do not exhibit a consistent degradation. 800 keV silicon ions are observed to cause resistance degradation, with an inverse dependence of resistance on oxygen vacancy density. Variation between different devices appears to be a key factor in determining the electrical response resulting from irradiation. The proposed degradation mechanism likely involves the creation of oxygen vacancies, but a better fundamental understanding of switching is needed before a definitive understanding of radiation degradation can be achieved.

Characterization of the H3D ASIC Readout System and 6.0 cm $^{3}$ 3-D Position Sensitive CdZnTe Detectors

Abstract: Two 20 mm × 20 mm × 15 mm pixelated CZT detectors made by eV-Products were characterized using the new H3D Application Specific Integrated Circuits (ASIC) readout system developed by the Instrumentation Division at Brookhaven National Laboratory. The ASIC is capable of reading out energy and timing signals from 121 anode pixels and the planar cathode electrode of one CZT detector simultaneously. The system has a measured electronic noise of ~2.2 keV FWHM with a dynamic range from 20 keV to 3.0 MeV. The two detectors achieved energy resolution of 0.48% FWHM and 0.60% FWHM, respectively, at 662 keV for single-pixel events from the entire 6.0 cm3 detection volume at room temperature with an un-collimated 137Cs source. The average (μτ)e of both detectors were measured to be >; 10-2 cm 2/V. The detection efficiency of the two detectors was evaluated at several different energies up to 1.3 MeV by comparing with simulated data. It was found that the total counts agree well between the measured data and the simulated data over the studied energy range. However, the measured photopeak counts were 10-15% lower than simulated photopeak counts at high gamma-ray energies. The analysis shows that the loss of photopeak efficiency is likely due to the charge loss from peripheral pixels to the boundary of detectors.

Recombination of Correlated Electron–Hole Pairs With Account of Hot Capture With Emission of Optical Phonons

Abstract: Electron thermalization and electron-hole recombination in scintillating crystals is simulated with and without account for Coulomb field created by a hole using both analytical estimations and Monte-Carlo approach. The Monte-Carlo simulation is performed both for crystals with one and two branches of longitudinal optical phonons to check the role of additional branches of these phonons. The results of numerical simulation show that the account for Coulomb field at all stages of the thermalization and capture significantly increases the probability of the geminate electron-hole binding in case of high values of optical phonon energies.

Trends and Patterns of Scintillator Nonproportionality

Abstract: Data on the photon nonproportional response of 33 inorganic scintillation materials are systemized and analyzed. The main trends of nonproportionality for different groups of inorganic scintillators, especially for oxides and halides, are highlighted. The dependence of the shape and degree of photon nonproportional response versus chemical composition, dopant type, index of refraction and other fundamental properties of the materials is studied. Better proportionality appears to be correlated with higher index of refraction of the compound. Another related factor is the width of the valence band in halide compounds. With larger valence band width from fluorides, to chlorides, to bromides, and to iodides, a better proportionality is observed.

Inorganic Scintillators for Thermal Neutron Detection

Abstract: The 3He shortage is forcing the neutron community to look for other detection methods. The inorganic scintillator may be an alternative. Thermal-neutron detection by means of inorganic scintillators has successfully been realized on a large scale at ISIS, UK, using 6LiF/ZnS:Ag mixed with an organic binder. This material is now introduced in the security field. For several reasons other traditional neutron scintillators, 6Li-glass:Ce and 6LiI:Eu, and relatively new materials such as 6Li6 Gd(BO3 )3 :Ce and elpasolites like Cs2 LiYCl6 :Ce and Cs2 LiLaBr6 :Ce are hardly used or did not yet find their way to application. The same applies to more recently studied materials of the LICAF group. The pros and cons of these inorganic materials for thermal neutron detection will be discussed.

SEU Recovery Mechanism for SRAM-Based FPGAs

Abstract: The application of SRAM-based field-programmable gate arrays (FPGAs) in mission-critical systems requires error-mitigation and recovery techniques to protect them from the errors caused by high-energy radiation, also known as single event upsets (SEUs). For this, modular redundancy and runtime partial reconfiguration are commonly employed techniques. However, the reported solutions feature different tradeoffs in the area overhead and the fault latency. In this paper, we propose a low area-overhead SEU recovery mechanism and describe its application in different self-recoverable architectures, which are experimentally evaluated using a specially designed fault-emulation environment. The environment enables the user to inject faults at selected locations of the configuration memory and experimentally evaluate the reliability of the developed solutions.

Radiation Induced Absorption in Rare Earth Doped Optical Fibers

Abstract: We have investigated the radiation induced absorption (RIA) of optical fibers with high active ion concentration. Comparing our results to the literature leads us to the conclusion that RIA appears to be only weakly dependent on the rare earth dopant concentration. Instead, co-dopants like Al, Ge, or P and manufacturing processes seem to play the major role for the radiation sensitivity. It is also observed that different types of irradiation cause very similar RIA at the same dose applied, with the exception at very high dose rates. It has been studied how RIA can be efficiently reduced via moderate heating. Recovery of up to 70% of the original transmission has been reached after annealing at 450 K. We conclude that radiation induced color centers have weak binding energies between 20 and 40 meV. This suggests that annealing could become a key strategy for an improved survival of rare earth doped fibers in radiative environments, opening up new possibilities for long-term missions in space.

The DLED Algorithm for Timing Measurements on Large Area SiPMs Coupled to Scintillators

Abstract: One of the main factors limiting the precision of timing measurements with silicon photomultipliers coupled to scintillators is the dark noise, especially in the case of large devices. In order to cope with it, a suitable signal processing should be employed. The method we propose is called differential leading edge discriminator (DLED) and allows an effective compensation of the baseline fluctuations due to the dark counts of the detector. In this paper we show a comparison between the measurements obtained using the traditional Leading Edge Discriminator technique and the DLED. The improvement we observe is remarkable. Combining this baseline correction algorithm with low temperatures, we were able to reach a coincidence resolving time of 180 ps FWHM, using 4 mm × 4 mm SiPMs produced at FBK coupled to 3.8 mm × 3.8 mm × 5 mm Teflon-wrapped LYSO crystals.

Frequency Dependence of Alpha-Particle Induced Soft Error Rates of Flip-Flops in 40-nm CMOS Technology

Abstract: In this paper, the alpha-particle induced soft error rate of two flip-flops are investigated as a function of operating frequency between 80 MHz and 1.2 GHz. The two flip-flops-an unhardened D flip-flop and a hardened pseudo-DICE flip-flop were designed in a TSMC 40 nm bulk CMOS technology. The error rates of both flip-flops increase with frequency. Analyses show that an internal single-event transient based upset mechanism is responsible for the frequency dependence of the error rates.

Scintillation Properties of Transparent Ceramic Pr:LuAG for Different Pr Concentration

Abstract: We manufactured transparent optical ceramic of Pr 0.2-1% doped Lu3Al5 O12 (Pr:LuAG) by the sintering method. We compare its optical and scintillation properties with the single crystal counterpart grown by the conventional Czochralski method. So far the scintillation ceramic of Pr:LuAG appeared inferior to its single crystal analog especially in terms of light yield. However, in the present case our ceramic Pr 0.25%-doped sample exhibited by 20% higher light yield compared to single crystal under γ-ray excitation. Furthermore, in the ceramic sample the slower scintillation decay components were suppressed and the defect related host emission as well. The optimized technology of optical ceramics thus appears very competitive to single crystals and opens great practical prospectives for the former materials in the field of fast scintillators.

Displacement Damage Effects in AlGaN/GaN High Electron Mobility Transistors

Abstract: We present the results of a radiation damage experiment on AlxGa1-xN/GaN high electron mobility transistors. The basic mechanism underlying the observed high radiation tolerance appears to be a strong internal piezoelectric field near the two-dimensional electron gas that causes scattered carriers to be reinjected.

Quantum Dot-Organic Polymer Composite Materials for Radiation Detection and Imaging

Abstract: Colloidal semiconductor nanocrystals exhibit physical properties that are characteristic of intermediate size scales between molecular states and solid state materials, and are often called quantum dots. Solid state semiconductor materials have been used extensively as scintillation detectors for ionizing radiation. We describe the use of semiconductor quantum dot-organic polymer composites for use as scintillation detectors and report the use of quantum dot-polymer composite thin films for X-ray imaging.

Demonstration of in-vivo Multi-Probe Tracker Based on a Si/CdTe Semiconductor Compton Camera

Abstract: By using a prototype Compton camera consisting of silicon (Si) and cadmium telluride (CdTe) semiconductor detectors, originally developed for the ASTRO-H satellite mission, an experiment involving imaging multiple radiopharmaceuticals injected into a living mouse was conducted to study its feasibility for medical imaging. The accumulation of both iodinated (131I) methylnorcholestenol and 85Sr into the mouse's organs was simultaneously imaged by the prototype. This result implies that the Compton camera is expected to become a multi-probe tracker available in nuclear medicine and small animal imaging.

CRÈME: The 2011 Revision of the Cosmic Ray Effects on Micro-Electronics Code

Abstract: We describe a tool suite, CREME, which combines existing capabilities of CREME96 and CREME86 with new radiation environment models and new Monte Carlo computational capabilities for single event effects and total ionizing dose.

Spectral- and Pulse-Shape Discrimination in Triplet-Harvesting Plastic Scintillators

Abstract: In this work, we describe a method to control the relative proportion of prompt and delayed luminosity of organic-based scintillators via direct and exponential emission from an extrinsic triplet state. This approach involves the incorporation of triplet-harvesting heavy metal complexes in plastic scintillator matrices to convert intrinsically non-luminescent host states to highly emissive guest states. Measurements on these plastic scintillators indicate improved light yields over the undoped polymers and the ability to perform neutron/gamma particle-discrimination. A similar extent of molecular-level control is not possible in traditional organic materials due to complex decay kinetics and the absence of spectral information for the delayed triplet-derived emission. The materials described here address these limitations through efficient host-guest triplet harvesting, which enables particle discrimination according to conventional pulse-shape discrimination (PSD) and a previously unreported spectral-shape discrimination (SSD) scheme.

Improved High Efficiency Stacked Microstructured Neutron Detectors Backfilled With Nanoparticle $^{6}$ LiF

Abstract: Silicon diodes with large aspect ratio trenched microstructures, backfilled with 6LiF, show a dramatic increase in thermal neutron detection efficiency beyond that of conventional thin-film coated planar devices. Described in this work are advancements in the technology using detector stacking methods to increase thermal neutron detection efficiency, along with the current process to backfill 6LiF into the silicon microstructures. The highest detection efficiency realized thus far is over 42% intrinsic thermal neutron detection efficiency by device-stacking methods. The detectors operate as conformally diffused pn junction diodes each having 1 cm2 area. Two individual devices were mounted back-to-back with counting electronics coupling the detectors together into a single dual-detector device. The solid-state silicon device was operated at 3 V and utilized simple signal amplification and counting electronic components that have been adjusted from previous work for slow charge integration time. The intrinsic detection efficiency for normal-incident 0.0253 eV neutrons was found by calibrating against a 3He proportional counter.

Radiation Studies of Spin-Transfer Torque Materials and Devices

Abstract: Spin-transfer torque film stacks and devices having in-plane magnetization were irradiated using a cobalt-60 gamma source. Samples were also exposed to 2 MeV and 220 MeV protons. Measurements of magnetization vs. field, ferromagnetic resonance, and tunnel magnetoresistance were performed on the film stacks before and after exposure to these sources and no changes were observed in the associated material properties. Spin-transfer torque devices were exposed to the same sources and show no changes in bit-state or write performance.

Similarities Between Proton and Neutron Induced Dark Current Distribution in CMOS Image Sensors

Abstract: Several CMOS image sensors were exposed to neutron or proton beams (displacement damage dose range from 4 TeV/g to 1825 TeV/g) and their radiation-induced dark current distributions are compared. It appears that for a given displacement damage dose, the hot pixel tail distributions are very similar, if normalized properly. This behavior is observed on all the tested CIS designs (4 designs, 2 technologies) and all the tested particles (protons from 50 MeV to 500 MeV and neutrons from 14 MeV to 22 MeV). Thanks to this result, all the dark current distribution presented in this paper can be fitted by a simple model with a unique set of two factors (not varying from one experimental condition to another). The proposed normalization method of the dark current histogram can be used to compare any dark current distribution to the distributions observed in this work. This paper suggests that this model could be applied to other devices and/or irradiation conditions.

Determination of Electric-Field Profile in CdTe and CdZnTe Detectors Using Transient-Current Technique

Abstract: Transient-current technique was used for measuring the profile of the electric field in CdTe and CdZnTe samples excited by an 241Am α-particle source. Current waveforms were analyzed by a general model, which involved both the effect of the space charge in the depleted region and charge trapping. The carrier mobility and the electric-field profile were also evaluated in this way. The maximum electric field was observed close to the cathode, whereas the minimum occurred near the anode. The decrease in the strength of the electric field from cathode to anode was explained in terms of a positive space charge formed in the detector's volume. Measurements under incomplete depletion, when an “inactive” region with zero electric field was observed under the anode, were reported as well. Space-charge densities of 1011-1012 cm-3 in CdTe and 1010 cm-3 in CdZnTe were evaluated. The dynamics of electron-hole plasma formed by a single α-particle absorption event was analyzed in detail and used as a complementary test of our reported model. An excellent agreement with theory was obtained.

Novel Layout Technique for N-Hit Single-Event Transient Mitigation via Source-Extension

Abstract: In this paper, a novel layout technique for N-hit single-event transient (SET) mitigation that is based on source-extension is proposed. Based on 65 nm bulk CMOS technology, both mixed-mode numerical simulations with technology computer-aided design (TCAD), as well as heavy-ion experiments show SET pulse widths are efficiently reduced with source extension. As opposed to what is found in the P-hit SET production process, where the source plays a detrimental role in SET mitigation due to the well-known bipolar effect, in the N-hit SET production process the source plays a beneficial role in reducing SET pulse widths, attributable to a parasitic reversed bipolar effect. This effect will be discussed in depth in this paper, and the proposed 'radiation hardened by design' (RHBD) layout technique will be extended to common combinational standard cells. The area penalty will also be discussed for the proposed layout technique. Meanwhile, both the P-hit and N-hit SET mitigation layout techniques will be introduced into the standard inverter layout, and the final improvement in SET pulse width will be discussed.

Characterization of a Pixelated CdTe X-Ray Detector Using the Timepix Photon-Counting Readout Chip

Abstract: A prototype 1mm thick CdTe detector bonded to a Timepix chip with 256*256 pixels at 55 μ m pitch was evaluated for use as a photon-counting imaging detector at high energy synchrotron beamlines (energy range 30-100 keV). A complete characterization of the system was performed. Powder diffraction experiments have also been conducted using a monochromatic beam at the ESRF. The expected gain in efficiency at energies above 30 keV with reference to silicon pixel detectors and current CCD systems of similar pixel size was demonstrated, together with an improved spatial resolution. Background-free powder diffraction spectra were obtained using the Timepix energy thresholding feature. The energy-resolved detection capabilities are limited by a strong charge sharing. The major limitations preventing a wider use of these devices at synchrotron X-ray sources are the lack of homogeneity of the CdTe crystal which exhibits numerous defects, and the unavailability of large fields of view.