Search

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/cm3 (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. [ABSTRACT FROM AUTHOR]

Charge losses at the inter‐pixel gap are typical drawbacks in cadmium–zinc–telluride (CZT) pixel detectors. In this work, an original technique able to correct charge losses occurring after the application of charge‐sharing addition (CSA) is presented. The method, exploiting the strong relation between the energy after CSA and the beam position at the inter‐pixel gap, allows the recovery of charge losses and improvements in energy resolution. Sub‐millimetre CZT pixel detectors were investigated with both uncollimated radiation sources and collimated synchrotron X‐rays, at energies below and above the K‐shell absorption energy of the CZT material. The detectors are DC coupled to fast and low‐noise charge‐sensitive preamplifiers (PIXIE ASIC) and followed by a 16‐channel digital readout electronics, performing multi‐parameter analysis (event arrival time, pulse shape, pulse height). Induced‐charge pulses with negative polarity were also observed in the waveforms from the charge‐sensitive preamplifiers (CSPs) at energies >60 keV. The shape and the height of these pulses were analysed, and their role in the mitigation of charge losses in CZT pixel detectors. These activities are in the framework of an international collaboration on the development of energy‐resolved photon‐counting systems for spectroscopic X‐ray imaging (5–140 keV). [ABSTRACT FROM AUTHOR]

Cadmium--zinc--telluride (CZT) arrays with photon-counting and energyresolving capabilities are widely proposed for next-generation X-ray imaging systems. This work presents the performance of a 2 mm-thick CZT pixel detector, with pixel pitches of 500 and 250 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 (>5000 V cm-1) and good energy resolution at moderate cooling (3.5% and 5% FWHM at 59.5 keV for the 500 and 250 µm arrays, respectively) by using fast pulse shaping with a low dead-time (300 ns). Charge-sharing investigations were performed using a fine time coincidence analysis (TCA), with very short coincidence time windows up to 10 ns. For the 500 mm pitch array (250 µm pitch array), sharing percentages of 36% (52%) and 60% (82%) at 22.1 and 59.5 keV, respectively, were measured. The potential of the pulse shape analysis technique for chargesharing detection for corner/border pixels and at high rate conditions (250 kcps 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 energyresolved photon-counting systems for high-flux energy-resolved X-ray imaging (1-140 keV). [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Fish introduction is one of the main causes of amphibian decline worldwide. It affects particularly rare aquatic phenotypes such as paedomorphs, which retain gills during the adult stage. In this context, we determined whether small wetlands, such as pools surrounding fished and fishless lakes, could sustain paedomorphic and metamorphic newts. To this end, we surveyed lakes known historically to sustain Alpine newts Ichthyosaura alpestris as well as 35 nearby pools. On the basis of the published records, the only known population exhibiting paedomorphosis in the Swiss Alps was found to be extirpated by salmonid introductions. However, the metamorphs persisted in peripheral pools, paedomorphosis was discovered at a new locality, and overwintering larvae were still present in one of the lakes. These results show the importance of conserving varied aquatic habitats such as pools in mountainous environments where the main resources can become unsuitable for amphibians because of fish introductions. Pools may also function as reservoirs in maintaining newt populations until programs to remove fish from lakes can be carried out. It is not known if paedomorphs could reappear after fish removal. However, the combined resilience of amphibians after fish removal and the genetic basis for paedomorphosis highlighted in other taxa by previous studies suggest that there is the potential to maintain this intraspecific case of diversity even after its disappearance. [ABSTRACT FROM AUTHOR]

Migration is adaptive if survival benefits are larger than costs of residency. Many aspects of bat migration ecology such as migratory costs, stopover site use and fidelity are largely unknown. Since many migrating bats are endangered, such information is urgently needed to promote conservation. We selected the migrating Leisler's bat (Nyctalus leisleri) as model species and collected capture-recapture data in southern Switzerland year round during 6 years. We estimated seasonal survival and site fidelity with Cormack-Jolly-Seber models that accounted for the presence of transients fitted with Bayesian methods and assessed differences between sexes and seasons. Activity peaked in autumn and spring, whereas very few individuals were caught during summer. We hypothesize that the study site is a migratory stopover site used during fall and spring migration for most individuals, but there is also evidence for wintering. Additionally, we found strong clues for mating during fall. Summer survival that included two major migratory journeys was identical to winter survival in males and slightly higher in females, suggesting that the migratory journeys did not bear significant costs in terms of survival. Transience probability was in both seasons higher in males than in females. Our results suggest that, similarly to birds, Leisler's bat also use stopover sites during migration with high site fidelity. In contrast to most birds, the stopover site was also used for mating and migratory costs in terms of survival seemed to be low. Transients' analyses highlighted strong individual variation in site use which makes particularly challenging the study and modelling of their populations as well as their conservation. [ABSTRACT FROM AUTHOR]

A 3D IR-mapping instrument has been recently developed at IMEM for the reconstruction of the position in three dimensions of Te inclusions inside CdZnTe crystals. Thanks to this apparatus, it has been possible to identify large Te inclusions (>20\ \mum) located just a few micrometers below the sample surface. Photoluminescence mapping of the region close to the inclusions revealed the enhancement of a near mid-gap band emission (0.78 eV) in correspondence with the defected region surrounding the inclusion. This supports the idea that the material surrounding Te inclusions presents a high concentration of deep levels probably acting as traps or recombination centers for carriers. The present result evidences the detrimental effect of Te inclusions on charge collection efficiency. [ABSTRACT FROM AUTHOR]

CdZnTe crystals were grown by the vertical Bridgman method in closed quartz ampoules. The crystalline quality and the impurity content of these crystals were studied. Several X-ray detectors were cut out of these crystals. The resistivity, emission spectra, \mu \tau product, and spectroscopic characteristics of these detectors were extensively measured and compared with the characteristics of detectors obtained from CdZnTe crystals grown by the boron oxide encapsulated vertical Bridgman technique. The detectors prepared from crystals grown without boron oxide show good \mu \tau value, spectroscopic resolution, and higher reproducibility. The influence of growth method on impurity content and on detector response was discussed. [ABSTRACT FROM AUTHOR]

The article discusses observed injury rates by forearm bands in an enlarged, medium sized insectivorous bat, the Leisler's bat Nyctalus leisleri. A non negligible frequency of 11.2% of bat recaptures which showed problems associated with forearm bands is reported. Most of the recaptured bats did not show any problems with the applied forearm bands. It is assumed that problems were initiated by a sporadic event. Factors such as wing morphology affect the optimal type of forearm band. The wing perforating injury did not negatively influenced the health status of the bats.

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 ( 241 Am, 57 Co, 137 Cs and 133 Ba) 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. [ABSTRACT FROM AUTHOR]