N. Zambelli
University of Parma
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Featured researches published by N. Zambelli.
IEEE Transactions on Nuclear Science | 2011
Andrea Zappettini; Laura Marchini; M. Zha; Giacomo Benassi; N. Zambelli; Davide Calestani; Lucio Zanotti; Enos Gombia; Roberto Mosca; Massimiliano Zanichelli; Maura Pavesi; N. Auricchio; E. Caroli
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, μτ 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 μτ value, spectroscopic resolution, and higher reproducibility. The influence of growth method on impurity content and on detector response was discussed.
Proceedings of SPIE | 2014
Irfan Kuvvetli; Carl Budtz-Jørgensen; Andrea Zappettini; N. Zambelli; Giacomo Benassi; Emrah Kalemci; E. Caroli; J. B. Stephen; N. Auricchio
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.
Journal of Instrumentation | 2012
N. Zambelli; L Marchini; G. Benassi; D. Calestani; E. Caroli; A. Zappettini
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.
IEEE Transactions on Nuclear Science | 2012
Laura Marchini; Andrea Zappettini; M. Zha; N. Zambelli; A. E. Bolotnikov; G. S. Camarda; R. B. James
Cadmium Zinc Telluride (CZT) is among the most promising materials for room-temperature X- and gamma-ray detectors. However, crystal defects such as Te inclusions and subgrain boundaries significantly hamper their performances. In this work, we evaluated CZT crystals grown by the modified low-pressure Bridgman technique at the IMEM Institute, Parma. We characterized the crystals by IR microscopy to identify the sizes and concentrations of the Te inclusions, along with high spatial resolution X-ray response mapping to measure the uniformity of their charge-transport properties. In addition, we employed white X-ray beam diffraction topography to analyze their crystalline structure.
Applied Physics Letters | 2014
A. Zappettini; N. Zambelli; G. Benassi; Davide Calestani; Maura Pavesi
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.
CrystEngComm | 2013
Andrea Zappettini; Laura Marchini; M. Zha; Giovanni Piacentini; N. Zambelli; Giacomo Benassi; Davide Calestani
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.
nuclear science symposium and medical imaging conference | 2010
Laura Marchini; Andrea Zappettini; M. Zha; N. Zambelli; A. E. Bolotnikov; G. S. Camarda; R. B. James
Cadmium Zinc Telluride (CZT) is one of the most exploited materials for x-ray and gamma ray radiation detection. Nevertheless CZT ingots are still affected by many defects, the most common features are Te inclusions, dislocations and grain boundaries. In this work the results of many investigation techniques are put together and compared in order to have a better understanding of the role of each defect in the degradation of the detector performances. A CZT ingot grown by low pressure Bridgman technique in IMEM Institute, Parma, was analyzed. The material was studied by means of the IR microscopy, for the identification of Te inclusions and then studied with the use of the synchrotron light source (NSLS National Synchrotron Light Source) for the analysis of the crystalline structure and uniformity of the x-ray response.
Sensors | 2017
Jacopo Aleotti; Giorgio Micconi; Stefano Caselli; Giacomo Benassi; N. Zambelli; Manuele Bettelli; Andrea Zappettini
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.
Journal of Synchrotron Radiation | 2017
L. Abbene; G. Gerardi; G. Raso; F. Principato; N. Zambelli; Giacomo Benassi; Manuele Bettelli; Andrea Zappettini
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.
2015 Workshop on Research, Education and Development of Unmanned Aerial Systems (RED-UAS) | 2015
Giorgio Micconi; Jacopo Aleotti; Stefano Caselli; Giacomo Benassi; N. Zambelli; Andrea Zappettini
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.