CUPID is a next-generation bolometric experiment aiming at searching for neutrinoless double-beta decay with -250 kg of isotopic mass of 100Mo. It will operate at -10 mK in a cryostat currently hosting a similar-scale bolometric array for the CUORE experiment at the Gran Sasso National Laboratory (Italy). CUPID will be based on large-volume scintillating bolometers consisting of 100Mo-enriched Li2MoO4 crystals, facing thin Ge-wafer-based bolometric light detectors. In the CUPID design, the detector structure is novel and needs to be validated. In particular, the CUORE cryostat presents a high level of mechanical vibrations due to the use of pulse tubes and the effect of vibrations on the detector performance must be investigated. In this paper we report the first test of the CUPID-design bolometric light detectors with NTD-Ge sensors in a dilution refrigerator equipped with a pulse tube in an above-ground lab. Light detectors are characterized in terms of sensitivity, energy resolution, pulse time constants, and noise power spectrum. Despite the challenging noisy environment due to pulse-tube-induced vibrations, we demonstrate that all the four tested light detectors comply with the CUPID goal in terms of intrinsic energy resolution of 100 eV RMS baseline noise. Indeed, we have measured 70-90 eV RMS for the four devices, which show an excellent reproducibility. We have also obtained high energy resolutions at the 356 keV line from a 133Ba source, as good as Ge semiconductor detectors in this energy range.

A single gamma-ray spectrometer installed at the end of a collimator can be used to infer the total emission from a tokamak plasma if the transport of gamma-rays from the plasma to the detector is known. In such analysis, the plasma emission profile plays a fundamental role, since it impacts the fraction of plasma volume intercepted by the detector line of sight. In this work, the DT 17 MeV fusion gamma-rays emission profile of the JET discharge #99608 from second 46 to 48 has been estimated both with the TRANSP code and reconstructed through tomographic inversion based on the neutron camera data, assuming that fusion gamma-rays have the same profile as the 14 MeV fusion neutrons. The gamma-ray transport has been evaluated both by MonteCarlo simulations and analytical calculations. By combining MonteCarlo and analytical evaluations of the gamma-ray transport in different ways with the estimated radiation emission profile, we provide four different routes to determine the total gamma-ray yield from measurements whose results agree within better than 10%.

An important instrumental development work has been done in the last two decades in the field of neutron and gamma ray spectroscopic measurements of magnetic confinement plasmas. Starting from the present state of the art instrumentation installed at JET, this paper reviews the recent development that has been carried out within the EUROFUSION programme for the forthcoming high power JET D and DT campaign. This development was dedicated to the realization of new compact neutron and gamma-ray spectrometers which combine very high energy resolution (typically better than 5%) and MHz counting rate capabilities allowing for time resolution in the 10 ms time scale. One of the advantages offered by the compact dimensions of these spectrometers is to make possible their use in multiple sight-line camera configurations, such as for future burning plasma reactors (ITER and DEMO). New compact neutron spectrometers based on single crystal diamond detectors have been developed and installed at JET for measurements of the 14 MeV neutron spectrum. Measurements on a portable DT neutron generator have shown that neutron spectroscopy of the accelerated beam ions at unprecedented energy resolution (~1% at 14 MeV) is possible, which opens up new opportunities for diagnosing DT plasmas. For what concerns gamma ray measurements, the JET gamma ray camera has been recently upgraded with new compact spectrometers based on a LaBr3 scintillator coupled to Silicon Photomultiplier with the dual aim to improve the spectroscopic and rate capabilities of the detectors. The upgrade camera system will reconstruct the spatial gamma ray emissivity from the plasma in the MeV energy range at MHz counting rates and energy resolution in the 2-4% range. This will allow physics studies of gamma rays produced by the interaction of fast ions with impurities in the plasma and bremsstrahlung emission from runaway electrons.

PurposeThe aim of the present study was to evaluate the expression of the cardiac norepinephrine transporter (NET) in the left ventricle (LV) of healthy pigs and its relationship with regional meta-[I-123]iodobenzylguanidine ([I-123]MIBG) myocardial uptake.ProceduresExperiments were performed on animals injected with [I-123]MIBG and acquired 2h later using an ultrafast CZT gamma camera to assess the regional myocardial uptake. After image acquisition, animals were euthanized; the heart was quickly excised and underwent to an ex vivo single photon emission tomography (SPECT) imaging. Four small samples of tissue were then harvested from mid-walls and apex of the left ventricle; NET densities were evaluated and further normalized for protein loading per cardiac region.ResultsThree variants of NET protein with different molecular weights were detected. The expression of NET was not homogenous in the LV, with the highest density in the inferior wall and the lowest one in the apical area. The regional in vivo [I-123]MIBG uptake revealed an analogous trend, showing a good linear relationship with NET expression. Parallel results were obtained from the ex vivo study.ConclusionThis study elucidates the expression of three different variants of NET proteins into the left ventricular myocardium of a healthy pig. NET expression into the LV was not homogeneous and paralleled by differences in regional [I-123]MIBG uptake. Moreover, the correlation and the agreement between measurements of regional expression of NET variants and [I-123]MIBG uptake represent a relevant finding for inferences about NET expression in the context of clinical imaging.

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 () 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 background, the CZT detector is able to discriminate the 10B signal from the neutron capture peaks of 113Cd.

Nowadays ionizing radiation detectors are widely employed in several application fields. These include medical imaging (CT, SPECT), environmental monitoring (control of the background radiation and contaminated areas), homeland security (cargo and luggage control) and astrophysics (study of x- and ?-ray emission from celestial bodies). In last decades the employment of semiconductor devices is getting more and more important and they have replaced classical scintillators in various application fields. Semiconductor based detectors can achieve better energy resolution thanks to the direct conversion of incident radiation into electrical signal. Among the compound semiconductors Cadmium Zinc Telluride (CdZnTe or simply CZT) meets the main radiation-detector demands. CdZnTe represents the best compromise in terms of energy efficiency, high atomic number Z, resistivity, and room temperature operation capability. For these reasons with CZT material nowadays high performance detectors with good energy resolution, high detection efficiency and room temperature operation capability can be fabricated. CZT is particularly appropriate in several application where cumbersome cooling systems are strongly discouraged or impossible to implement. Furthermore the high Z of CdZnTe allows its employment in high-energy spectroscopy (as in space application) with relatively low device thickness. Unfortunately CZT shows some issues not yet overcome by the scientific community. In my PhD thesis I have focused my effort on the study of contacts. The two main aspects that I have addressed are constituent metal and electrode geometry. The constituent metal determines the contact type, blocking or ohmic nature of contacts are primarily dependent on the deposited metal. Comprehensive study of the band structure, electrical properties and physicochemical characteristics of the metal-semiconductor interface carried out on different metals is reported in this thesis. The other important aspect, covered during my PhD, is the geometric configuration of electrodes. With appropriate geometries, we are able to recover the deterioration of spectroscopic performance due to poor hole transport properties. Moreover, for each specific application, some contact layouts can be more performing than another, depending on the properties required such as collection efficiency, energetic resolution, imaging capability, etc. This thesis includes some efforts and results, reached at IMEM-CNR and Physics Department of the University of Parma during the last three years, on devices for radiation detection applications.

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 gm and 250 gm, 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 x 10 gm 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.

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.

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.

La rilevazione di sorgenti radioattive disperse illecitamente nell'ambiente è di interesse in molte situazioni, ad esempio per l'emersione di "sorgenti orfane" in alcune tipologie di insediamenti, quali acciaierie, fonderie, depositi di rottame metallico, inceneritori dove il materiale lavorato può includere parti radiogene, ovvero discariche in cui si sia smaltito materiale/rifiuto radioattivo. In questo lavoro si presenta un sistema di teleoperazione aptico per un veicolo aereo senza equipaggio (UAV, o più comunemente drone) per la localizzazione e l'identificazione di sorgenti radioattive situate in ambienti esterni non strutturati. Il UAV è equipaggiato con un rivelatore di raggi gamma a semiconduttore al Tellurio di Cadmio Zincato (CdZnTe). Rispetto ad un volo automatico, inserire un essere umano nel circuito di controllo del UAV, permette di concentrarsi su aree maggiormente candidate ad un potenziale inquinamento. Tuttavia, il pilotaggio via radio di veicoli aerei è complesso a causa della mancanza di consapevolezza della situazione da parte dell'operatore. E' infatti fondamentale fornire all'operatore oltre al feedback visivo diretto anche fonti di informazioni aggiuntive, sfruttando segnali acquisititi da sensori di bordo. In questo lavoro il sistema a feedback di forza viene utilizzato come canale sensoristico supplementare per guidare l'esplorazione dell'ambiente. In particolare, viene presentato un algoritmo di "rendering aptico" che fornisce una delimitazione della zona di interesse attorno alla posizione della sorgente di radiazioni rilevata. L'approccio proposto per la teleoperazione aptica è nuovo rispetto ai precedenti studi in cui il feedback aptico è stato soprattutto sfruttato per evitare collisioni dell'UAV stesso.

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.

Today it is widely recognised that a measurement of the polarization status of cosmic sources high energy emission is a key observational parameter to understand the active production mechanism and its geometry. Therefore new instrumentation operating in the hard X/soft gamma rays energy range should be optimized also for this type of measurement. In this framework, we present the concept of a small high-performance spectrometer designed for polarimetry between 100 and 1000 keV suitable as a stratospheric balloon-borne payload dedicated to perform an accurate and reliable measurement of the polarization status of the Crab pulsar, i.e. the polarization level and direction. The detector with 3D spatial resolution is based on a CZT spectrometer in a highly segmented configuration designed to operate as a high performance scattering polarimeter. We discuss different configurations based on recent development results and possible improvements currently under study. Furthermore we describe a possible baseline design of the payload, which can be also seen as a pathfinder for a high performance focal plane detector in new hard X and soft gamma ray focussing telescopes and/or advanced Compton instruments. Finally we present preliminary data from Montecarlo undergoing studies to determine the best trade-off between polarimetric performance and detector design complexity.

II-VI semiconductors obtain a real interest in the scientific community for their wide applications in several fields: from optoelectronic and solar cell technology to applications as radiation detectors. The charge collection efficiency (C.C.E.) - i.e. the ratio between the photo-generated charge and the charge collected by the electrodes - is closely related both to the material transport properties and to the internal electric field. It could be exploited to study the transport parameters of these materials and the electric field profile inside the devices under irradiation. Under opportune conditions, C.C.E., as a function of applied bias, should follow Hecht or Many's equation, depending on the penetration length of incident radiation. A central requirement in both these models is a uniform internal electric field but in real devices this condition is seldom satisfied due to the presence of spatial charge, as demonstrated by Pockets measurements and bad photocurrent curve fitting. The authors, starting from the Ramo-Shockley theorem and assuming a linear shape of the electric field, present a new model to describe the C.C.E. as a function of applied bias, with the mobility life-time product mu tau and the field slope as parameters. This model, with respect to the previous ones, gives information also about the internal electric field profile and, despite its simplicity, it seems to be a good approximation in several cases, as shown by the experimental analyses reported here.

Several 2 inch CdZnTe crystals have been grown by the Vertical Bridgman technique and growth interface shape has been studied by photoluminescence mapping. The results show that it is possible to obtain a convex interface shape for the whole crystal by the combined use of a highly thermally conductive ampoule support and an element covering melt top, with higher thermal conductivity than the CdZnTe melt preventing the direct contact of melt and vapour.

CdTe/CdZnTe is a consolidated material to realize detectors for a large variety of applications, such as medical, industrial, and space research. An Italian collaboration, involving the CNR/IMEM and INAF/IASF institutes, was born some years ago with the aim to develop a national capability to produce CZT detectors starting from the material growth to the final detection device. Some important features of these detectors (pulse height, energy resolution, photopeak efficiency) are affected by the charge collection efficiency: the low mobility of the charge carriers (particularly the holes) and trapping/detrapping phenomena can degrade the CdTe/CZT detectors response, depending on the distance between the charge formation position and the collecting electrodes. Several efforts have been made to improve the detection efficiency as well as the energy resolution, using both the optimization of the electrode geometry (drift strip technique, coplanar-grid, small pixel effect) and pulse height compensation methods to overcome the hole trapping problem. We have studied a bi-parametric method that uses a twin pulse shaping active filter to analyze the same signal: one slow, which is proportional to the energy of the photon, and one fast, which depends on the position of the interaction with respect to the collecting electrode. The experimental results obtained with the application of this bi-parametric technique on planar CZT detectors of good quality grown by the Vertical Bridgman method at CNR/IMEM are presented as a function of the bias voltage, photon energy and shaping time pairs.

We evaluated a spectroscopy-grade 15 x 15 x 7 mm(3) CdZnTe (CZT) crystal with a high pi-product, > 10(-2) cm(2)/V, but impaired by microscopic extended defects, such as walls of dislocations, low-angle and sub-grain boundaries, and Te inclusions. First, we evaluated a planar detector fabricated from this crystal using a Micro-scale X-ray Detector Mapping (MXDM) technique. Then, we fabricated from the same crystal a pixel detector to study local non-uniformities of the electric field. The measured X-ray response maps confirmed the presence of non-uniformities in the charge transport, and they showed that the global- and local-distortions of the internal E-field correlated to the extended defects and space-charge buildup on the side surfaces.

Poor crystallinity remains a major problem affecting the availability and cost of CdZnTe (CZT) detectors. Point defects are responsible for small gradual charge loss and correlated with the electron clouds' drift times, which allows electronic correction of the output signals to achieve high spectral-resolution even with large-volume CZT detectors. In contrast, extended defects causes significant charge losses, which typically are uncorrelated, and, thus, result in much greater fluctuations of the output signals that cannot be corrected. Although extended defects do not affect all the interaction events, their fraction rapidly increases with the crystal's thickness and volume. In this paper, we summarize our recent results from testing CZT material and detectors that emphasize the particular roles of two types of extended defects, and their contributions to the device's overall performance.

The chemical etching and the passivation processes of CdZnTe wafers were studied. The treatment effects were tested through an X-Ray Photoelectron Spectroscopy (XPS) analysis and I-V measurement. The chemical etching in 2%Br-MeOH solution may effectively remove the damaged layer and improve the ohmic contact between CdZnTe wafer and Au electrodes making rich the surface with Te. After different etching times, the CdZnTe wafers were passivated with NH4F/H2O2.CdZnTe wafer passivated immediately after etching showed the best passivation efficiency because the enriched Te on the surface was fully oxidized to TeO2, which results in the thickest oxide layer, and the most stoichiometric surface. Also the surface leakage current was reduced in comparison with the sample passivated 24 h after etching.

Presently, a great amount of effort is being devoted to the development of CdTe and CdZnTe (CZT) detectors for a large variety of applications such as medical, industrial, and space research. We present the spectroscopic properties of some CZT crystals grown by the standard vertical Bridgman method and by the boron oxide encapsulated vertical Bridgman method, which has been recently implemented at IMEM-CNR (Parma, Italy). In this technique, the crystal is grown in an open quartz crucible fully encapsulated by a thin layer of liquid boron oxide. This method prevents contact between the crystal and the crucible, thereby allowing larger single grains with a lower dislocation density to be obtained. Several mono-electrode detectors were realized, with each having two planar gold contacts. The samples are characterized by an active area of about 7 mm x 7 mm and thicknesses ranging from 1 to 2mm. The charge transport properties of the detectors have been studied by mobility-lifetime (? x ?) product measurements, carried out at the European Synchrotron Radiation Facility (Grenoble, France) in the planar transverse field configuration, where the impinging beam direction is orthogonal to the collecting electric field. We have performed several fine scans between the electrodes with a beam spot of 10 ?m x 10 ?m at various energies from 60 to 400 keV. In this work, we present the test results in terms of the (? x ?) product of both charge carriers.

CdZnTe crystals for the preparation of X-ray imaging detectors have been grown by the boron oxide encapsulated vertical Bridgman method. The homogeneity of the crystals has been studied by photoluminescence mapping, energy dispersion X-ray analysis, and resistivity mapping. The zinc distribution follows an anomalous behavior that deviates from the normal freezing equation. The wafers cut perpendicular to the growth direction show an homogeneous resistivity distribution, suggesting the possible exploitation of these crystals for the production of large volume imaging detectors.