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The scientific challenges still open in hard X-rays and γ-rays astronomy require the development of new instrumentation able to overcome the sensitivity limits of the present one. Among the technologies currently under study to cover the energy range between several tens of keV and one MeV, the development of telescopes equipped with broadband Laue lenses associated with focal planes with high spectroscopic and imaging performance represents an extremely promising solution. With this perspective, we report on the development and the first spectroscopic characterisation results of an X/γ rays detection system (10-1000 keV) based on CZT spectrometers with spatial resolution in three dimensions (3D) and a digital acquisition electronic chain suitable to build high-performance focal planes. The final prototype will be made by packing four sensors. Each sensor is realised using a single spectroscopic grade CZT crystal with dimensions of ∼20×20×6 mm3, on which the anode strips are realised orthogonally to the cathode ones. The anode structure consists of 12 collecting anodes with a pitch of 1.6 mm and three drift strips between each pair of anodes, while the cathode side is segmented into ten strips with a pitch of 2 mm, orthogonal to anode side strips. The detector front-end electronics is based on custom-designed low noise charge sensitive preamplifiers (CSP). The CZT sensor induces the charge pulses on the electrodes, then they are read by a multichannel Digital Pulse Processing system based on FPGA through its readout front-end. The results obtained with both standard spectroscopic chains and the analysis of digitised pre-amplified signals confirm the expected performances in terms of spectroscopy (

The effectiveness of Boron Neutron Capture Therapy (BNCT) treatment depends on the amount of radiation dose deposited locally by the reaction 10B ( n , α ) 7 Li in the tumour; however, the local and real time measurement of this quantity during the neutron irradiation is a big challenge. To evaluate the dose it is necessary to know the spatial distribution of the 10 B concentration and thermal neutron flux in the tissue during the irradiation. One technique to solve this problem relies on the on-line detection of the 478 keV 7 Li de-excitation photons that can be used to map the spatial distribution of the reaction rate of the 10B ( n , α ) 7 Li. The present work has been developed within a project aiming to develop a Single Photon Emission Computed Tomography (SPECT) system based on CdZnTe (CZT) semiconductor detector. This work studied the performances of a 5 × 5 × 20 mm 3 CZT prototype detector focusing on the energy resolution and detection efficiency inside the energy range 200–1400 keV. The energy resolution at 478 keV is ∼ 3% and the detection efficiency is around 6%. These preliminary results confirms the feasibility of a CZT detector as a sensitive unit for a BNCT-SPECT imaging system.

Charge losses are typical drawbacks in cadmium–zinc–telluride (CZT) pixel detectors. The effects of these phenomena are strongly related to the interaction point of the photons and are more severe for photon interactions at the inter-pixel gap and near the pixelated anode. In this work, we present some original techniques able to correct charge losses in pixelated CZT detectors at both low and high fluxes. The height, the shape and the arrival time of collected- and induced-charge pulses with both positive and negative polarities are analysed to recover charge losses after the application of charge sharing addition (CSA). Sub-millimetre CZT pixel detectors, fabricated by different manufacturers (Redlen Technologies, Canada and IMEM-CNR, Italy), are investigated with both uncollimated radiation sources and collimated synchrotron X rays (Diamond Light Source, U. K.), at energies below and above the K-shell absorption energy of the CZT material. The processing of the detector pulses is performed through a digital approach. A 16-channel digital readout electronics was recently developed at University of Palermo (Italy), able to perform on-line multi-parameter analysis (event arrival time, pulse shape, pulse height) and fine coincidence analysis (coincidence time windows < 20 ns). These activities are in the framework of an international collaboration on the development of energy-resolved photon counting (ERPC) systems for high-flux spectroscopic X-ray imaging (5-150 keV).

Density is a very important property of materials because of its influence on their mechanical properties. For this reason, the possibility of measuring material density is of strategic importance for several industrial applications such as wood boards sawing, wood panels production, or ceramic tiles manufacturing. In order to answer to this need, X-ray densitometry techniques and computed tomography (CT) scanners are used nowadays. However, these traditional X-ray inspection techniques usually measure only relative density, or, in other terms, they need a calibration procedure before operation. To overcome this issue, Due2lab s.r.l. in collaboration with the Istituto dei Materiali per l'Elettronica ed il Magnetismo (IMEM)-Consiglio Nazionale delle Ricerche (CNR) Institute developed a CdZnTe (CZT)-based X-ray spectrometer capable of determining the absolute density value of a sample material in terms of g/cm 3 (and additionally extracting information about its elemental composition). The system has been specifically designed for in-line real-time nondestructive inspection of industrial production; thus, it is potentially capable to return density information within a very short acquisition time. In this article, we will describe the CZT spectrometer and the hyperspectral X-ray analysis set-up in detail and we will show how to perform absolute density measurement on three different materials: 1) a plastic polyethylene sample, 2) ceramic tiles, and 3) pine and fir wood samples.

The analysis of γ-ray spectra can be an arduous task, especially in the case of room temperature semiconductor detectors, where several distortions and instrumental artifacts conceal the true spectral shape. We developed a genetic algorithm to perform the unfolding of γ-spectra in order to restore the true energy distribution of the incoming radiation. We successfully validated our approach on experimental spectra of four radionuclides (241Am, 57Co, 137Cs and 133Ba) acquired with two CdZnTe-based detectors with different contact geometries (single pixel and drift strip). The unfolded spectra consist of δ-like peaks in correspondence with the radiation emissions of each radioisotope.

We report on the development and of a complete X/γ rays detection system (10-1000 keV) based on CZT spectrometers with spatial resolution in three dimensions (3D) and a digital electronics acquisition chain. The prototype is made by packing four linear modules, each composed of one 3D CZT sensors. Each sensors is realized using a single spectroscopic graded CZT crystal of about 20×20×5 mm3. An electrode structure consisting of 12 collecting anodes with a pitch of 1.6 mm and 3 drift strips between each pair of anodes for 48 strips (0.15 mm wide) on the anodic side was adopted. The cathode is made of 10 strips with a pitch of 2 mm and orthogonal to anode side strips. Since the reading of the drift strips will carried out by putting in parallel all the strips that occupy the same place with respect to a collecting anode, the channels number for each sensors is only 25. The detector readout front-is based on custom designed low noise charge sensitive pre-amplifiers (CSP) implemented in hybrid 16 channels board. The CZT module and its CSP front-end provide the signals to a multichannel Digital Pulse Processing FPGA based system able to digitize and process continuously the signals. The digital system implement an innovative firmware that allow performing fine time-tagging, online pulse shape and height analysis with good energy resolution.

Nowadays, CdZnTe (CZT) is one of the key materials for the development of room temperature X-ray and gamma ray detectors and great efforts have been made on both the device and the crystal growth technologies. In this work, we present the results of spectroscopic investigations on new boron oxide encapsulated vertical Bridgman (B-VB) grown CZT detectors, recently developed at IMEM-CNR Parma, Italy. Several detectors, with the same electrode layout (gold electroless contacts) and different thicknesses (1 and 2.5 mm), were realized: the cathode is a planar electrode covering the detector surface (4.1×4.1 mm2), while the anode is a central electrode (2×2 mm2) surrounded by a guard-ring electrode. The detectors are characterized by electron mobility-lifetime product (µeτe) values ranging between 0.6 and 1·10−3 cm2/V and by low leakage currents at room temperature and at high bias voltages (38 nA/cm2 at 10000 V/cm). The spectroscopic response of the detectors to monochromatic X-ray and gamma ray sources (109Cd, 241Am and 57Co), at different temperatures and fluxes (up to 1 Mcps), was measured taking into account the mitigation of the effects of incomplete charge collection, pile-up and high flux radiation induced polarization phenomena. A custom-designed digital readout electronics, developed at DiFC of University of Palermo (Italy), able to perform a fine pulse shape and height analysis even at high fluxes, was used. At low rates (200 cps) and at room temperature (T=25 °C), the detectors exhibit an energy resolution FWHM around 4% at 59.5 keV, for comparison an energy resolution of 3% was measured with Al/CdTe/Pt detectors by using the same electronics (A250F/NF charge sensitive preamplifier, Amptek, USA; nominal ENC of 100 electrons RMS). At high rates (750 kcps), energy resolution values of 7% and 9% were measured, with throughputs of 2% and 60% respectively. No radiation polarization phenomena were observed at room temperature up to 1 Mcps (241Am source, 60 keV), while a detector collapse characterizes the samples at T Comparison with two traveling heater method (THM) grown CZT detectors (REDLEN, Canada), fabricated with the same electrode layout, is also presented. These activities are in the framework of an Italian research project on the development of energy-resolved photon counting (ERPC) systems for high flux energy-resolved X-ray imaging.

In this work we report on the results of electrical characterization of new CdZnTe detectors grown by the Boron oxide encapsulated Vertical Bridgman technique (B-VB), currently produced at IMEM-CNR (Parma, Italy). The detectors, with gold electroless contacts, have different thicknesses (1 and 2.5 mm) and the same electrode layout, characterized by a central anode surrounded by a guard-ring electrode. Investigations on the charge transport mechanisms and the electrical contact properties, through the modeling of the measured current–voltage ( I – V ) curves, were performed. Generally, the detectors are characterized by low leakage currents at high bias voltages even at room temperature: 34 nA/cm 2 ( T =25 °C) at 10,000 V/cm, making them very attractive for high flux X-ray measurements, where high bias voltage operation is required. The Au/CdZnTe barrier heights of the devices were estimated by using the interfacial layer-thermionic-diffusion (ITD) model in the reverse bias voltage range. Comparisons with CdZnTe detectors, grown by Traveling Heater Method (THM) and characterized by the same electrode layout, deposition technique and resistivity, were also performed.

Large scale factories such as steel, wood, construction, recycling plants and landfills involve the procurement of raw material which may include radiating parts, that must be monitored, because potentially dangerous for workers. Manufacturing operations are carried out in unstructured environments, where fully autonomous unmanned aerial vehicle (UAV) inspection is hardly applicable. In this work we report on the development of a haptic teleoperated UAV for localization of radiation sources in industrial plants. Radiation sources can be localized and identified thanks to a novel CZT-based custom gamma-ray detector integrated on the UAV, providing light, compact, spectroscopic, and low power operation. UAV operation with a human in the loop allows an expert operator to focus on selected candidate areas, thereby optimizing short flight mission in face of the constrained acquisition times required by nuclear inspection. To cope with the reduced situational awareness of the remote operator, force feedback is exploited as an additional sensory channel. The developed prototype has been demonstrated both in relevant and operational environments.

Boron Neutron Capture Therapy (BNCT) is a binary radiotherapy based on the reaction 10B(n,α)7Li induced by thermal neutrons. 10B selectively loads cancer cells through a boronated drug injected into patient few hours before neutron irradiation. The secondary charged particles have short ranges in tissues (less than the mean cell diameter of few tens of µm), thus they deposit their whole kinetic energy (up to 2.79 MeV) inside the cell where the capture reaction took place. In this way it is possible to selectively damage the malignant cells sparing the surrounding healthy ones.To take full advantage of BNCT selectivity a precise knowledge of 10B spatial distribution is required. This quantity can be measured by Single Photon Emission Computed Tomography (SPECT) thanks to the emission of a 478 keV γ ray in the 94% of 10B capture reactions. Notably, the counting rate of this photon is meaningful of the dose rate due to the neutron captures in the patient thus allowing an in vivo, real time dose monitoring.In the present study we evaluated the capabilities of a small prototype of CdZnTe (CZT) photon detector to reconstruct the tomographic image of tissue equivalent phantoms loaded with point like γ sources (such as 22Na, 137Cs and 57Co), activated detectors (Cu and Au wires) and 18F water solutions.

CdZnTe is nowadays a reference semiconductor for detection of X and γ-radiation. The electrical properties of CdZnTe-based (CZT) detectors are strongly affected by the surface and subsurface defects, which can cause an excessive surface leakage current (SLC). This issue strongly degrades the sensor performance and becomes critical for multi-stripes detectors, where the stripes are kept at different voltage potentials in order to shape the electric field inside the semiconductor material.In this work, we propose a passivation method based on the deposition of a thin Al 2 O 3 film on the non-metallized CZT surface. To demonstrate the effectiveness of the method, we fabricated several 19.4x19.4x5 mm3 CZT multi-stripes detectors with 48 parallel Au stripes on the anode face (12 collecting anodes and 36 drift stripes) and subsequently deposited a Al 2 O 3 polycrystalline thin film on the CZT surface between the stripes. Al 2 O 3 deposition was achieved by sputtering technique. Electrical characterization of surface leakage current before and after Al 2 O 3 is presented.Al 2 O 3 coating treatment allowed us to obtain exceptionally low surface leakage current values, 10 to 100 times lower than those measured after our best wet passivation method for CZT surface chemical oxidation. Since Al 2 O 3 passivation significantly reduces surface leakage current and thus improves the signal-to-noise ratio, our finding is very promising for a substantial advancement of multi-stripe detectors performance.

We have developed a system for in-line density measurements based on a CdZnTe (CZT) detector to be used for quality control purposes related to production inspection, failure analysis, and lot inspection for wood-based panel industry. Real-time absolute density measurement systems are fundamental to minimize production wastage, especially for continuous production as wood and ceramics.CZT detectors with dimensions 4.1 x 4.1 x 2.5 mm3 were realized starting from standard Redlen Technologies CZT material by due2lab s.r.l. in collaboration with IMEM-CNR and integrated in a stand-alone detection module fully engineered and realized by due2lab. Low dark current density (10÷100 pA/mm2 @100 V/mm) even at high bias voltages (up to 1000 V) at room temperature (T = 25 °C) has been reproducibly achieved in several samples. These low dark current values are crucial in non-destructive X-ray industrial applications where X-ray photons in the low energy range play an important role in material discrimination. Digitalization of the CZT sensor signal was obtained with a novel digital electronic board designed by due2lab. The spectra obtained by irradiating the detectors with a 241Am source show excellent resolution down to 12 keV. The detectors were integrated in an innovative in-line non-destructive X-ray density measurements system for wood panel production quality control developed by IMAL PAL s.r.l. (Modena, Italy).

The National Institute of Nuclear Physics (INFN) is supporting the 3CaTS project with the aim of developing a new Single Photon Emission Computed Tomography (SPECT) system for real time 10 B therapeutic dose monitoring in the binary experimental hadron therapy called Boron Neutron Capture Therapy (BNCT). BNCT is a highly selective tumour treatment based on the neutron capture reaction 10 B(n,α) 7 Li. The secondary particles have a high LET with ranges in tissues of the order of 10 μm (thus less than the mean cell diameter of few tens μm). Targeting the 10 B delivery towards cancer, the released energy lethally damages only the malignant cells sparing the normal tissues, thus enabling a cell-level selective treatment. To properly exploit this selectivity it is mandatory to know the 10 B spatial distribution inside patients body during neutron irradiation. This can be achieved by detecting the 478 keV γ ray emitted in the 94% of 10 B capture reactions by a SPECT system. A 3D CZT drift strip detector with a sensitive volume of 20x20x5 mm 3 was developed, able to perform high-resolution X-ray and γ ray spectroscopic imaging (10-1000 keV). The detector signals are analysed by a custom digital multi-channel electronics, based on two pipelined fast and slow analysis, able to perform multi-parameter analysis and fine temporal coincidences (

In this work, we present the results of a microscale X-ray mapping of a 2 mm thick CZT pixel detector, with pixel pitches of 500 μm and 250 μm, using collimated synchrotron X-ray sources at the Diamond Light source (U. K.). The detector is dc coupled to a fast and low noise ASIC (PIXIE ASIC), characterized only by the preamplifier stage. A custom 16-channel digital readout electronics was used, able to perform online fast pulse shape and height analysis (PSHA), with low dead time and reasonable energy resolution at both low and high fluxes. The detector allows high bias voltage operation (> 5000 V/cm) and good energy resolution at room temperature (5.3 %, 2.3 % and 2.1 % FWHM at 22.1, 59.5 and 122.1 keV, respectively) by using fast pulse shaping with low dead time (300 ns). Charge sharing investigations were performed by using uncollimated and collimated X-ray sources with energies above and below the K-shell absorption energy of the CZT material. Collimated 10 × 10 μm synchrotron X-ray beams were used to study the spatial dependence of the amplitude, the shape and the multiplicity of the detector pulses. Charge losses, after charge sharing addition (CSA), were observed for interactions occurring in the volume of the inter-pixel gap and an original method was proposed to recover these losses and improve the energy resolution.High rate measurements at 550 kcps/pixel were also performed, pointing out the key role of the pulse shape analysis in the detection of both charge sharing and pile-up events.

A BNCT-dedicated SPECT system to monitor in real time the 10B dose is under development focusing on CdZnTe (CZT) solid state detectors as photon sensors. Since BNCT facilities are characterised by a ( n + γ ) radiation field and considering the high value of cadmium neutron absorption cross section , we evaluated the response of a CZT detector using the irradiation thermal neutron facility of the Pavia University research nuclear reactor. The reported measurements showed that, despite the thermal neutron and γ background, the CZT detector is able to discriminate the 10B signal from the neutron capture peaks of 113Cd.

Fully-encapsulated CZT crystals were grown by vertical Bridgman technique using boron oxide as encapsulant for preventing material decomposition. To detect possible effects of boron on the crystal microstructure, we performed current-voltage measurements and Photo-Induced Current Transient Spectroscopy measurements on samples grown by boron oxide encapsulated vertical Bridgman (set EVB) and standard vertical Bridgman (set VB). In both sets, the well-known A-center and a midgap trap dominate the PICTS spectra. However, significant differences are evident, related to the different defect contents. Our findings indicate that most of the boron atoms are electrically inactive and do not affect the transport properties of the material, confirming that boron oxide vertical Bridgman technique can be adopted for the growth of detector grade CZT crystals.

Exploitation of CdZnTe crystals for X-ray imaging detectors is limited by the incorporation of tellurium inclusions during growth. Over the years, several post-growth thermal treatments have been proposed for the removal of tellurium inclusions, often compromising the high electrical resistivity of the material. Moreover, main attention is usually paid to large inclusions, whose direct connection with the deterioration of detector properties has been demonstrated, while the effect of thermal annealing on small inclusions is usually neglected. In this article, the effect of different thermal annealing process on the concentration of inclusions down to 1 μm size is studied. A two-step process in tellurium vapors has been shown to be effective to anneal large tellurium inclusions and to preserve the high resistivity of the samples as well.

Photon counting arrays with energy resolving capabilities are recently desired for the next-generation X-ray imaging systems. In this work, we present the performance of a 2 mm thick CZT pixel detector, with pixel pitches of 500 mu m and 250 mu m, coupled to a fast and low noise ASIC (PIXIE ASIC), characterized by only the preamplifier stage. A 16-channel digital readout electronics was used to continuously digitize and process each output channel from the PIXIE ASIC, performing multi-parameter analysis (event arrival time, pulse shape, pulse height) at low and high input counting rates (ICRs). The spectroscopic response of the system to monochromatic X-ray and gamma ray sources, at both low and high ICRs, is presented with particular attention to the mitigation of some typical spectral distortions (pile-up and charge sharing). The detector allows good energy resolution at moderate cooling (3% FWHM 59.5 keV, -1200 V, T = 5 C) by using fast shaped pulses (i.e. pulses with time widths of 300 ns). Charge sharing investigations were performed by using a fine time coincidence analysis (TCA) and a pulse shape analysis (PSA). The potentialities of the PSA for charge sharing detection even at high photon counting rates were also shown.

Cadmium-zinc-telluride (CZT) arrays with photon-counting and energy-resolving capabilities are widely proposed for next-generation X-ray imaging systems. This work presents the performance of a 2â...mm-thick CZT pixel detector, with pixel pitches of 500 and 250â...μm, dc coupled to a fast and low-noise ASIC (PIXIE ASIC), characterized only by the preamplifier stage. A custom 16-channel digital readout electronics was used, able to digitize and process continuously the signals from each output ASIC channel. The digital system performs on-line fast pulse shape and height analysis, with a low dead-time and reasonable energy resolution at both low and high fluxes. The spectroscopic response of the system to photon energies below (109Cd source) and above (241Am source) the K-shell absorption energy of the CZT material was investigated, with particular attention to the mitigation of charge sharing and pile-up. The detector allows high bias voltage operation (>5000â...Vâ...cm-1) and good energy resolution at moderate cooling (3.5% and 5% FWHM at 59.5â...keV for the 500 and 250â...μm arrays, respectively) by using fast pulse shaping with a low dead-time (300â...ns). Charge-sharing investigations were performed using a fine time coincidence analysis (TCA), with very short coincidence time windows up to 10â...ns. For the 500â...μm pitch array (250â...μm pitch array), sharing percentages of 36% (52%) and 60% (82%) at 22.1 and 59.5â...keV, respectively, were measured. The potential of the pulse shape analysis technique for charge-sharing detection for corner/border pixels and at high rate conditions (250â...kcpsâ...pixel-1), where the TCA fails, is also shown. Measurements demonstrated that significant amounts of charge are lost for interactions occurring in the volume of the inter-pixel gap. This charge loss must be accounted for in the correction of shared events. These activities are within the framework of an international collaboration on the development of energy-resolved photon-counting systems for high-flux energy-resolved X-ray imaging (1-140â...keV).This work presents the performance of a 2â...mm-thick CZT pixel detector, with pixel pitches of 500 and 250â...μm coupled to a custom 16-channel digital readout electronics, performing on-line fast pulse shape and height analysis. Charge-sharing investigations were performed, at both low and high fluxes, using fine time coincidence analysis and pulse shape analysis.

Recently some of the authors have proposed a new technique to deposit contacts on CdZnTe detectors that combines the standard electroless procedure and the scanning pipette technique. In this work it is shown that by using a 15 micron inner diameter alumina pipette it is possible to deposit gold dots, pixels and micro-stripes without using the standard photolithographic process. Moreover, it is shown that the performances in terms of charge collection efficiency and energy resolution of detectors prepared with the scanning pipette technique are similar to the ones of detectors prepared with the standard electroless procedure.

This paper describes the process of hydrogen diffusion in API 5L X65 and ASTM A182 F22 steels with three different metallurgical microstructures (quenched and tempered, quenched and annealed) by an electrochemical technique which is a modified Devanathan and Stachurski's cell. The analysis of experimental results compares different measurement methods for hydrogen diffusion coefficients: 1) charge method; 2) partial charge and partial discharge method; 3) discharge method. For the steel, cathodically polarized in acidic medium (pH ≈ 4.2), the less dispersed and more meaningful results are obtained by partial charge and partial discharge method after about one hundred hours of polarization, i.e., when a stationary regime was reached. The discharge method, carried out after one hundred hours of polarization, provides analogous results by extrapolation of the experimental results obtained during the initial phase of hydrogen desorption. The hydrogen diffusion coefficients measured would appear dependent only on the hydrogen migration processes in the crystal lattice regular sites and corresponding values DL increase as follows: quenched

Several materials are under investigations for flat panel x-ray detector applications. Among them, PbO shows interesting properties, i.e. high sensitivity, large stopping power and high resistivity at room temperature. However, the exploitation of PbO is limited by the difficulty to obtain good quality films constituted by a single phase. In this paper, we describe a new approach for the vapour phase growth of orthorhombic PbO films. The grown layers show a single phase, good crystallinity, and preferential orientation along the c axis. Optical characterization evidenced the presence of a broad defect band. Gold contacted films showed very high electrical resistivity and appreciable response to X-ray radiation.

A visuo-haptic augmented reality (VHAR) interface is presented enabling an operator to teleoperate an unmanned aerial vehicle (UAV) equipped with a custom CdZnTe-based spectroscopic gamma-ray detector in outdoor environments. The task is to localize nuclear radiation sources, whose location is unknown to the user, without the close exposure of the operator. The developed detector also enables identification of the localized nuclear sources. The aim of the VHAR interface is to increase the situation awareness of the operator. The user teleoperates the UAV using a 3DOF haptic device that provides an attractive force feedback around the location of the most intense detected radiation source. Moreover, a fixed camera on the ground observes the environment where the UAV is flying. A 3D augmented reality scene is displayed on a computer screen accessible to the operator. Multiple types of graphical overlays are shown, including sensor data acquired by the nuclear radiation detector, a virtual cursor that tracks the UAV and geographical information, such as buildings. Experiments performed in a real environment are reported using an intense nuclear source.

CdTe/CdZnTe is an attractive and consolidated material with which to realize detectors with good efficiency and energy resolution, operating at room temperature for a large variety of applications such as astrophysics, medical imaging and security. However, this type of material suffers from the low mobility of the charge carriers (particularly the holes), which are trapped and so degrade the detector response in terms of charge collection efficiency, energy resolution and photopeak efficiency. The response of a planar CdTe/CdZnTe detector, which depends on the distance between the charge formation position and the collecting electrodes, can be improved by using two kinds of techniques, based on the optimization of the electrode geometry and/or signal compensation methods. We are studying the feasibility and the reliability of a biparametric method that uses a twin pulse shaping active filter to analyze each signal from the detector twice: one “Slow”, which is proportional to the energy of the incident photon, and one “Fast”, which depends on the position of the interaction with respect to the collecting electrode. In this paper we describe the bi-parametric technique applied to planar CdZnTe detectors grown by CNR/IMEM and to Spectrometer Grade detectors. We report the experimental results in terms of energy resolution, peak-to valley ratio and photopeak efficiency, as well as the compensated spectra obtained as a function of the bias voltage, photon energy and shaping time pairs. We also report the results obtained by using a CdZnTe drift strip detector. Furthermore, this technique could be implemented in an array of detectors, whose front-end electronics is composed of ASICs, where the shaping time can be selected for each channel, like the RENA-3 IC (NOVA R&D).

Recently, CdZnTe (CZT) detectors have been widely proposed and developed for room-temperature X-ray spectroscopy even at high fluxes, and great efforts have been made on both the device and the crystal growth technologies. In this work, the performance of new travelling-heater-method (THM)-grown CZT detectors, recently developed at IMEM-CNR Parma, Italy, is presented. Thick planar detectors (3 mm thick) with gold electroless contacts were realised, with a planar cathode covering the detector surface (4.1 mm × 4.1 mm) and a central anode (2 mm × 2 mm) surrounded by a guard-ring electrode. The detectors, characterized by low leakage currents at room temperature (4.7 nA cm−2 at 1000 V cm−1), allow good room-temperature operation even at high bias voltages (>7000 V cm−1). At low rates (200 counts s−1), the detectors exhibit an energy resolution around 4% FWHM at 59.5 keV (241Am source) up to 2200 V, by using commercial front-end electronics (A250F/NF charge-sensitive preamplifier, Amptek, USA; nominal equivalent noise charge of 100 electrons RMS). At high rates (1 Mcounts s−1), the detectors, coupled to a custom-designed digital pulse processing electronics developed at DiFC of University of Palermo (Italy), show low spectroscopic degradations: energy resolution values of 8% and 9.7% FWHM at 59.5 keV (241Am source) were measured, with throughputs of 0.4% and 60% at 1 Mcounts s−1, respectively. An energy resolution of 7.7% FWHM at 122.1 keV (57Co source) with a throughput of 50% was obtained at 550 kcounts s−1 (energy resolution of 3.2% at low rate). These activities are in the framework of an Italian research project on the development of energy-resolved photon-counting systems for high-flux energy-resolved X-ray imaging.

CdZnTe crystals are nowadays employed as X-ray detectors for a number of applications, such as medical imaging, security, and environmental monitoring. One of the main difficulties connected with CdZnTe-based detector processing is the poor contact adhesion that affect bonding procedures and device long term stability. We have shown that it is possible to obtain mechanically stable contacts by common electroless deposition using alcoholic solutions instead of water solutions. The contacts show blocking current-voltage characteristic that is required for obtaining spectroscopic detectors. Nanoscale-resolved chemical analysis indicated that the improved mechanical adhesion is due to a better control of the stoichiometry of the CdZnTe layer below the contact.

The exploitation of CdZnTe crystals for the preparation of X- and gamma-ray detectors is still limited by the low yield in the production of high quality material. Twins and grain boundaries are still present in the state of the art melt-grown crystals, due to the difficulty to implement seeding procedures. In this paper, the zinc content of several CdZnTe crystals is analyzed in detail with the purpose of studying the phenomena occurring in the first part of growth. It is found that both the obtained experimental data as well as the ones reported by several other authors cannot be explained in terms of the usually reported model, based only on the effects of supercooling. Alternative explanations that take into account the possibility of nucleation from different sites and the possible effects of zinc thermodiffusion are suggested. These observations are very important in view of implementation of new growth configurations for obtaining larger single crystal yield.

In this work, we report on the results of electrical characterization of CdZnTe (CZT) detectors, with gold electroless contacts, grown by the boron oxide encapsulated vertical Bridgman technique (B-VB), currently produced at IMEM-CNR (Parma, Italy). The detectors, with different thicknesses (1 and 2.5 mm), have the same electrode layout: the anode is a central electrode (2 x 2 mm(2)) surrounded by a guard ring electrode. The cathode is a planar electrode covering the detector surface (4.1 x 4.1 mm(2)). Current-voltage (I-V) characteristics were measured at different temperatures in order to study the charge transport and the electrical properties. These detectors were compared with the traveling heater method (THM) CdZnTe grown detectors (Redlen, Canada), fabricated with the same electrode layout and deposition. The results highlight the low leakage currents of the B-VB CdZnTe detectors even at high bias voltages: 38 nA/cm(2) (T = 25 degrees C) at 10000 V/cm. This feature allows high bias voltage operation, very important for high flux applications. These activities are in the framework of an Italian research project on the development of energy resolved photon counting (ERPC) systems for high flux energy resolved X-ray imaging.

In this work, we present the results of spectroscopic investigations on CdZnTe (CZT) detectors grown by the boron oxide encapsulated vertical Bridgman technique (1MEM-CNR, Parma, Italy). The detectors, with different thicknesses (1 and 2.5 mm), are characterized by the same electrode layout (gold electroless contacts): the anode is a central electrode (2 x 2 mm(2)) surrounded by a guard-ring electrode, while the cathode is a planar electrode covering the detector surface (4.1 x 4.1 mm(2)). The results of electrical investigations point out the low leakage currents of these detectors even at high bias voltages: 38 nA/cm(2) (T = 25 degrees C) at 10000 V/cm. The time stability and the spectroscopic response of the detectors, at different temperatures and fluxes, were investigated. Am-241 spectra were measured up to 1 Mcps. The detectors were compared with the traveling heater method (THM) CZT grown detectors (Redlen), fabricated with the same electrode layout. These activities are in the framework of an Italian research project on the development of energy resolved photon counting (ERPC) systems for high flux energy resolved X-ray imaging.

CdZnTe detectors are commonly exploited for the detection of gamma rays. However, obtaining mechanical stable, low noise contacts on CdZnTe is still an issue. In particular, ohmic contacts would be preferable for high flux applications. In this work, we show that it is possible to obtain mechanical stable gold contacts by electroless deposition in methanol solution. Moreover, we show that electroless deposited nickel contacts are also mechanical stable and are good candidates for the realization of ohmic contacts on high resistivity CdZnTe crystals.

In an archipelago of marshland fragments in Central Tyrrhenian Italy, we calculated the frequency of occurrence (i.e., the probability that an individual of a sensitive species occurs in a fragment of determined size area) of a set of water-related breeding bird species. Only one species (Cettia cetti) occurred in marshland fragments within the 0–1 size area class while all species were present in larger size classes. Acrocephalus scirpaceus is the only species that showed a significant increase in frequency of occurrence moving from 0–1 to 1–10 ha size area classes. However, our study supports the hypothesis that the frequency of occurrence of several other area-sensitive species (e.g., Tachybaptus ruficollis, Ixobrychus minutus, Gallinula chloropus, Fulica atra) increases toward larger size area classes, although these trends here are not significant. Therefore, the frequency of occurrence of these species should be a focus of further research in a wider range of marshland fragments. These results will be useful in terms of wetland management implications (e.g., selection of suitable fragments for sensitive species).

Introduction - we developed a disability scale to monitor myasthenia gravis (MG) patients, based on degree of function impairment and daily frequency of each symptom. Material & methods - the scale was based on standardized questions and clinical examination. The scale was administered to 12 patients, one or more times, for a total of 22 interviews. Each observation was recorded on videotape and reviewed by five independent observers. The ability of our scale to discriminate clinical changes was also compared with the Osserman classification. Results - our scale showed from substantial to almost perfect inter and intraobserver agreement. Our findings showed that clinically relevant changes not detected by Osserman staging were disclosed by our scale. Conclusion - our scale is simple and easy to use in clinical practice. It offers an accurate means of evaluating disability in MG patients and may detect clinically relevant changes in disability. It would therefore be useful to monitor the effects of therapy.

The prevalence of mental retardation related to chromosomal abnormalities, including fragile X syndrome, was studied among 2735 males aged between five and 20 years living in the Republic of San Marino. Five cases of chromosomal abnormalities were found, including one case with fragile X syndrome, with partial epilepsy and a CT scan showing a large arachnoid cyst in the posterior fossa. The prevalence of mental retardation due to chromosomal abnormality was 1.83 per 1000, and that due to fragile X syndrome was 0.37 per 1000. Although these findings relate to only a small population, they are the first from a Mediterranean area.

In this work, we present the performance of new travelling heater method (THM) grown CZT detectors, recently developed at IMEM-CNR Parma, Italy. Thick planar detectors (3 mm thick) with gold electroless contacts on CZT crystals grown by Redlen Technologies (Victoria BC, Canada) were realized, with a planar cathode covering the detector surface (4.1 x 4.1 mm(2)) and a central anode (2 x 2 mm(2)) surrounded by a guard ring electrode. The detectors, characterized by low leakage currents at room temperature (4.7 nA/cm(2) at 1000 V/cm), allow good room temperature operation even at high bias voltages (> 7000 V/cm). At low rates, the detectors exhibit an energy resolution around 4 % FWIEM at 59.5 keV (Am-241 source) up to 2200 V, by using a commercial front-end electronics (A250F/NF charge sensitive preamplifier, Amptek, USA; nominal equivalent noise charge ENC of 100 electrons RMS). At high rates (1 Mcps), the detectors, coupled to a custom-designed digital pulse processing electronics developed at DiFC of University of Palermo (Italy), show low spectroscopic degradations: energy resolution values of 8 % and 9.7 % FWFIM at 59.5 keV (241 Am source) were measured, with throughputs of 0.4 % and 60 % respectively. These activities are in the framework of an Italian research project on the development of energy-resolved photon counting (ERPC) systems for high flux energy-resolved X-ray imaging.

Wetlands are naturally patchy habitat types that in fragmented landscapes are usually immersed inside a sea of anthropogenic habitat matrix. Decrease in patch size area and increase of patch isolation are two important components of wetland fragmentation. We investigated the effects of fragment area on bird species richness at four-level assemblages in a highly fragmented Mediterranean wetland system of Central Italy. Our results indicate that fragment area influenced differently the species richness for distinct assemblages in wetland fragments. Area was significantly correlated to total species richness, vagrant, breeding and Phragmites -related breeding species (PBS). A comparison of the various regression equations showed that the log-log relationship was the best-fitted model and the amount of variation ( R 2 of log-log regression line) was much higher for PBS and breeders than for vagrants. This pattern confirmed that when including vagrants in studies based on the equilibrium theory of island bioge...

The acrofacial dysostosis (AFD) syndromes are an heterogeneous group of disorders with undefined classification and inheritance. We report the sonographic and clinical features of an AFD fetus with predominantly pre-axial forms. We made a prenatal diagnosis of Nager syndrome but postnatal examination showed post-axial defects previously undetectable by ultrasound.

This work proposes a haptic teleoperation system of an unmanned aerial vehicle (UAV) aimed at localizing radiation sources in outdoor environments. Radiation sources are localized and identified by equipping the UAV with a CdZnTe-based custom X-ray detector providing light, compact, and low power operation. The UAV is guided in direct sight by the operator. The system allows exploration of potentially dangerous areas without a close exposure of the human operator. The operator is able to provide motion commands to the UAV while receiving force feedback from a 3DOF haptic interface. Force feedback provides an attractive basin around the location of the most intense detected radiation. Preliminary experiments have been conducted to test the elements of the system.

Localization and identification of nuclear and radiological material are main issues in case of nuclear accident or terrorist attack. In these cases, the use of a unmanned aerial vehicle would be highly recommended in order to preserve the safety of the human operators. For this purpose, we have integrated a compact, light, low power operating, CZT-based gamma ray detector on a commercially available UAV. The system allows exploration of potentially dangerous areas without a close exposure of the human operator. The operator is able to provide motion commands to the UAV while receiving force feedback from a 3DOF haptic interface. Force feedback provides an attractive basin around the location of the most intense detected radiation. A field experiment has been carried out and a 192Ir nuclear source has been localized and identified exploiting the novel teleoperation system.

CdZnTe crystals are used for the realization of X-ray detectors. In particular, pixel detectors can be exploited for many application fields such as medical diagnostics, security, and industrial inspection. In the last years, CdZnTe crystals have routinely been grown by the boron oxide encapsulated vertical Bridgman technique. In this work, it is shown that linear array detectors have been prepared based on this material. The detectors show low leakage current and have been coupled to a specifically designed research-grade low noise ASIC. The detectors show good spectroscopic characteristics and no polarization effects, meeting the requirements for the realization of high throughput, multi-energy scanners.

At DTU Space we have developed a high resolution three dimensional (3D) position sensitive CZT detector for high energy astronomy. The design of the 3D CZT detector is based on the CZT Drift Strip detector principle. The position determination perpendicular to the anode strips is performed using a novel interpolating technique based on the drift strip signals. The position determination in the detector depth direction, is made using the DOI technique based the detector cathode and anode signals. The position determination along the anode strips is made with the help of 10 cathode strips orthogonal to the anode strips. The position resolutions are at low energies dominated by the electronic noise and improve therefore with increased signal to noise ratio as the energy increases. The achievable position resolution at higher energies will however be dominated by the extended spatial distribution of the photon produced ionization charge. The main sources of noise contribution of the drift signals are the leakage current between the strips and the strip capacitance. For the leakage current, we used a metallization process that reduces the leakage current by means of a high resistive thin layer between the drift strip electrodes and CZT detector material. This method was applied to all the proto type detectors and was a very effective method to reduce the surface leakage current between the strips. The proto type detector was recently investigated at the European Synchrotron Radiation Facility, Grenoble which provided a fine 50 × 50 μm2 collimated X-ray beam covering an energy band up to 600 keV. The Beam positions are resolved very well with a ~ 0.2 mm position resolution (FWHM ) at 400 keV in all directions.

The presence of Te inclusions is one of the main factors limiting performances of CdZnTe crystals as X-ray detectors. We show that by means of infrared laser radiation it is possible to move and anneal tellurium inclusions exploiting a thermo-diffusion mechanism. The process is studied live during irradiation by means of an optical microscope equipment. Experimental conditions, and, in particular, energy laser fluence, for annealing inclusions of different dimensions are determined. (C) 2014 AIP Publishing LLC.

Crystallographically textured, orthorhombic β-PbO films are deposited on silica substrates by reactive vapor deposition of Pb in an O2 atmosphere of a two-zone oven (1000:1 Ar/O2 ratio at a flow rate of 100 mL/min, 1050800 °C, 25 min).

The development of focusing optics based on wide band Laue lenses operating from ∼60 keV up to several hundreds of keV is particularly challenging. This type of hard X-ray or gamma ray optics requires a high performance focal plane detector in order to exploit to the best its intrinsic capabilities. We describe a three dimensional (3D) position sensitive detector prototype suitable for use as the basic module for a high efficiency Laue lens focal plane detector. This detector configuration is currently under study for use in a balloon payload dedicated to performing a high significance measurement of the polarization status of the Crab nebula/pulsar between 100 and 500 keV. The prototype is made by packing 8 linear modules, each composed of one basic sensitive unit bonded onto a thin supporting ceramic layer. Each unit is a drift strip detector based on a CZT crystal, irradiated transversally to the electric field direction. The anode is segmented into 8 detection cells, each comprising one collecting strip and 8 surrounding drift strips. The drift strips are biased by a voltage divider. The cathode is divided into 4 horizontal strips for the reconstruction of the Z interaction position. The detector readout electronics is based on three RENA-3 ASICs and the data handling system uses custom electronics based on an FPGA to provide the ASIC setting, the event handling logic and the data acquisition. We will describe the components and the status of the ongoing activities for the assembling of the proposed 3D CZT prototype and the result of the first performance tests on the CZT linear modules.

CdZnTe crystals are largely employed as substrates for IR devices, X-ray detectors, and electro-optic modulators. One of the main problems affecting device quality is the presence of tellurium inclusions. These form during crystal cooling due to the retrograde shape of the liquidus curve or are incorporated during growth. In fact, the maximum melting point is actually on the Te side of the phase diagram. Moreover, high resistivity is obtained by doping with In or Cl and by growing crystals from a Te deviated charge. Different approaches have been suggested for the elimination of tellurium inclusions by means of post growth treatments. One of them relies on the observation that when CdZnTe crystals are annealed in a temperature gradient, Te inclusions drift towards the higher temperature region, due to the fact that CdZnTe solubility in tellurium increases with temperature. However, it was reported by many authors that after thermal treatment high resistivity can't be reproducibly recovered. It was also shown that Te inclusions can experience thermomigration under the influence of a CO2 micron laser irradiation at 10.6 micron [1]. The effect of the laser irradiation was evaluated comparing samples before and after irradiation. Recently, our group has developed a new system for the 3D reconstruction of the position of tellurium inclusions in CdZnTe crystals that is based on IR microscopy [2]. In this work, we have studied the tellurium inclusion thermomigration induced by a pulsed Nd:YAG laser irradiation (1.064 micron). The inclusion movement was live-monitored in situ using our new IR microscopy system. First of all, with respect to the use of the CO2 laser, it should be noted that a much larger thermomigration speed was in general observed, without the need to heat the sample. Secondly, thanks to the in situ observation, it was possible to conclude that inclusions migrate at different speed according to their dimension. Moreover, inclusions separates into smaller parts and finally solve in the CdZnTe matrix. In conclusion, it was shown that laser irradiation at 1.064 micron is a powerful method to eliminate tellurium inclusions by CdZnTe crystals without heating the sample and that thanks to in situ monitoring it is possible to study the thermomigration dynamics and, thus, to tailor the process at best

The development of new focusing optics based on wide band Laue lenses operating from ~60 keV up to several hundred keV is particularly challenging. This type of hard X-ray or gamma ray optics requires a high performance focal plane detector in order to exploit to the best their intrinsic capabilities. We describe a three dimensional (3D) position sensitive detector prototype suitable as the basic module for a high efficiency Laue lens focal plane detector. This detector configuration is currently under study for use in a balloon payload dedicated to performing a high significance measurement of the polarization status of the Crab between 100 and 500 keV. The prototype is made by packing 8 linear modules, each composed of one basic sensitive unit bonded onto a thin supporting ceramic layer. Each unit is a drift strip detector based on a CZT crystal, irradiated transversally to the electric field direction. The anode is segmented into 8 detection cells, each comprising one collecting strip and 8 surrounding drift strips. The drift strips are biased by a voltage divider. The cathode is divided into 4 horizontal strips for the reconstruction of the Z interaction position. The detector readout electronics is based on RENA-3 ASIC and the data handling system uses a custom electronics based on FPGA to provide the ASIC setting, the event handling logic, and the data acquisition. This paper mainly describes the components and the status of the undergoing activities for the construction of the proposed 3D CZT prototype and shows the results of the electronics tests.

Gold electroless contacts are commonly used for the preparation of CdZnTe-based detectors. In this work it is shown that it is possible to deposit electroless patterned contacts on CdZnTe detectors without the use of photolithography by means of the scanning pipette technique. The technique is based on the delivery of gold chloride solution by means of a pipette moved by micro-controlled motors. The obtained detectors show optimal current-voltage characteristics and good spectroscopic response.

CdZnTe is one of the most exploited materials for the realization of room temperature X- and gamma- ray detectors. However the final cost of the devices remains a limiting factor for large-scale applications. A strong effort was done in the last years for decreasing the cost of both crystals and device fabrication processes. Because of the important role played by the metal-CZT interface on the functioning of the final device, a special attention should be payed to the technology employed in the realization of metal contacts. A novel, reproducible and low-cost method for metal deposition on CZT surface has been developed combining two different technologies: ink-jet printing and electroless deposition. With this technique it is possible to avoid the photolithography process and still obtain complex contact patterns with a good spatial resolution and high reproducibility. The current-voltage characteristics of the obtained contacts are also reported, demonstrating good electrical properties.