In the last ten years silicon photomultipliers (SiPMs) have gained terrain in experiments and applications in which photomultiplier tubes have been the dominant photosensors during decades. Imaging ...Atmospheric Cherenkov Telescopes (IACTs) for very high energy (VHE, E>50 GeV) gamma-ray astronomy are experiencing the same process. Until now FACT was the only IACT using SiPMs. In the Cherenkov Telescope Array (CTA), the next-generation VHE gamma-ray observatory, at least 70 telescopes equipped with SiPMs are planned to be built. The first prototypes have already been constructed and are now being commissioned. Here we discuss some of the advantages and drawbacks of using SiPMs in VHE gamma-ray astronomy and provide a brief overview of different developments related to the use of SiPMs in IACTs.
Large-Area SiPM Pixels (LASiPs) in SPECT Wunderlich, C.; Guberman, D.; Paoletti, R. ...
Journal of instrumentation,
07/2022, Letnik:
17, Številka:
7
Journal Article
Recenzirano
Abstract
A standard camera for Single Photon Emission Computed Tomography (SPECT) contains 50–100 photomultiplier tubes (PMTs) that occupy at least 50% of its volume. It is shielded by a thick layer ...of lead which makes it heavy and bulky. Replacing PMTs by silicon photomultipliers (SiPMs) could significantly reduce the weight and size of a SPECT camera. However, the main obstacle is the limited size of SiPMs: even with the largest commercially available SiPM of 6 × 6 mm
2
a few thousand channels would be needed to fill a camera. As a solution, we propose to use Large Area SiPM Pixels (LASiPs) which are built by summing the currents of several SiPMs into a single output. We developed a LASiP prototype summing 8 SiPMs using the MUSIC ASIC. To test the feasibility of using this solution in SPECT, we built a proof-of-concept micro camera that consisted of four of our LASiP prototypes coupled to a 40 × 40 × 8 mm
3
NaI(Tl) crystal. We were able to reconstruct simple images of a
99
m
Tc capillary with an intrinsic spatial resolution of ∼2 mm and an energy resolution of ∼11.6%. We also simulated the system with Geant4, finding a good agreement with our experimental results. The simulations were extended to a larger camera, aiming to study the impact of pixel size, shape and noise.
H, C, N, O stable isotope ratios of forage, milk and the corresponding cheese were analysed to define the isotopic characteristics of two typical mountain cheeses produced in two different terroirs ...with different types of vegetation. δ13C was shown to be mainly influenced by the presence of C4 plants in animal diet and, in the case of C3 plant-based forage it was below −23‰ varying according to the site and herbage type. δ15N is more related to vegetation type and confirmed to be lower than +4‰ for alpine products. The altitude of the origin area influences δ18O and δ2H. The isotopic values of milk and cheese casein were not significantly different, except δ18O, while they were both significantly different from the values of forage, except δ2H. Using the combined stable isotope ratios a good discrimination level between the products from two different types of pasture at two mountain sites was achieved.
Nowadays, simple and non-destructive methods able to recognize pathogens in real time and in living tissues are still missing. This study has been designed to evaluate the presence of fungi (i.e. ...Gnomoniopsis spp.) in chestnuts. To this aim, a measurement setup based on terahertz radiation has been used to highlight the presence of fungal diseases in chestnut samples. A population of fifty chestnuts that was known to be partially infected by Gnomoniopsis spp., has been imaged in the low terahertz range by a compact and portable active imaging system equipped with a 100 GHz (0.1 THz) source. The relationship between the chestnut physical parameters, such as mass or volume, and the light attenuation in healthy and infected fruits has been tentatively explained by assuming a different water density and a different physical structure in healthy and unhealthy fruits, due to carbohydrates hydrolysis by the fungi. The preliminary results here described suggest that the sole analysis of the light attenuation combined with the measurement of weight or volume of a chestnut can provide an immediate indication of the presence of fungi in the fruits.
•Non-destructive imaging approaches able to recognize pathogens in real time in living tissue are still not available.•Fifty chestnuts, part of them infected by Gnomoniopsis spp., have been investigated using a THz spectroscopic approach.•Results suggest that our method can provide a fast confirmation of the presence of fungi in the chestnuts investigated.
•The feasibility of using Large-Area SiPM pixels (LASiPs) in SPECT is studied.•LASiPs allow to reduce the weight and size of a full-body SPECT camera.•SPECT cameras based on LASiPs can achieve ...similar performance to those based on PMTs.•Geant4 simulations allow to extend the results to a large camera.
Single Photon Emission Computed Tomography (SPECT) scanners based on photomultiplier tubes (PMTs) are still largely employed in the clinical environment. A standard camera for full-body SPECT employs ~50-100 PMTs of 4–8 cm diameter and is shielded by a thick layer of lead, becoming a heavy and bulky system that can weight a few hundred kilograms. The volume, weight and cost of a camera can be significantly reduced if the PMTs are replaced by silicon photomultipliers (SiPMs). The main obstacle to use SiPMs in full-body SPECT is the limited size of their sensitive area. A few thousand channels would be needed to fill a camera if using the largest commercially-available SiPMs of 6 × 6 mm2. As a solution, we propose to use Large-Area SiPM Pixels (LASiPs), built by summing individual currents of several SiPMs into a single output. We developed a LASiP prototype that has a sensitive area 8 times larger than a 6 × 6 mm2 SiPM. We built a proof-of-concept micro-camera consisting of a 40 × 40 × 8 mm3 NaI(Tl) crystal coupled to 4 LASiPs. We evaluated its performance in a central region of 15×15 mm2, where we were able to reconstruct images of a 99mTc capillary with an intrinsic spatial resolution of ~2 mm and an energy resolution of ~11.6% at 140 keV. We used these measurements to validate Geant4 simulations of the system. This can be extended to simulate a larger camera with more and larger pixels, which could be used to optimize the implementation of LASiPs in large SPECT cameras. We provide some guidelines towards this implementation.
Among the non-destructive techniques capable of obtaining information on biological systems even in vivo, terahertz-based techniques are emerging due to their specificity to the water content, which ...can represent an important indicator of the presence of microorganisms and, in general, of the health status, particularly in plants. Nevertheless, the analysis of the extracted data (especially for images) and the exploitation of the potential of the technique for the study of the complex phenomena that occur in living tissues are still almost unexplored fields. In this work, the hydration status of leaves both in vivo and ex vivo was monitored continuously and non-destructively by acquiring videos in the sub-terahertz range through a portable imaging system. A model for describing the water flow in space and time in the midvein of a leaf is obtained which is suitable for the analysis of the data extracted from the portable sub-terahertz imaging system. These results show that terahertz-based technology can be used to study biological phenomena even in vivo; moreover, they pave the way for the introduction of a general method for the analysis of terahertz data based on surface fits in space and in time as well.
•THz radiation is effective in monitoring the water distribution in living tissues.•Leaf water distribution gives information about its health status.•Analysis of THz video data monitors hydration and dehydration dynamics of leaves.•Space and time water diffusion in leaves can be analysed simultaneously.
The ecological transition of the extreme energy events experiment Abbrescia, M.; Avanzini, C.; Baldini, L. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2023, Letnik:
1055
Journal Article
Recenzirano
The need for reducing the emission of gases, potentially contributing to the greenhouse effect and climate change, has impacted many fields, including scientific research. The Extreme Energy Event ...(EEE) collaboration started, already several years ago, a series of tests aiming at finding a more eco-friendly replacement for the gases used in the Multigap Resistive Plate Chambers (MRPCs) of its network.
These tests identified a promising binary gas mixture, and data taking has begun with a subset of the telescopes of the EEE network, making EEE the first experiment in the world completely implemented with MRPCs and operating with an eco-friendly gas mixture. Here the results of the tests and a preliminary comparison of the telescope performance measured with the standard (non eco-friendly) and the new eco-friendly gas mixtures are presented and discussed.
Studies on new Eco-gas mixtures for Extreme Energy Events Project Bossini, E.; Abbrescia, M.; Avanzini, C. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
01/2023, Letnik:
1046
Journal Article
Recenzirano
The Extreme Energy Events (EEE) experiment, a joint project of the Centro Fermi and INFN Italian national research institutes, has a dual purpose: a scientific research program for measurements of ...the cosmic rays flux at ground level and an intense outreach and educational program with an active contribution of students and teachers in the construction and operation of the detectors in High Schools. The network counts 60 tracking detectors, each made by three Multigap Resistive Plate Chambers (MRPC), operated so far with a gas mixture composed by 98% C2H2F4 and 2% SF6. Given its high Global Warming Potential (GWP), the collaboration, since few years, started a R&D on alternative mixtures environmentally sustainable. Latest results on a C3H2F4 + He eco-friendly mixture are here presented.
After its successful campaign of measurements beyond the Polar Arctic Circle, the PolarquEEEst experiment measured the cosmic charged particle rate at sea level in a latitude interval between 35
∘
N ...and 82
∘
N. In this paper, these measurements are described and the corresponding results are discussed.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
In the last few years a number of efforts have been undertaken to develop new technology related to Silicon Photomultipliers (SiPMs). These photosensors consist of an array of identical Avalanche ...Photodiodes operating in Geiger mode and connected in parallel to a single output. The Italian Institute of Nuclear Physics (INFN) is involved in the R&D program Progetto Premiale Telescopi CHErenkov made in Italy (TECHE.it) to develop photosensors for a SiPM based camera that will be part of the Cherenkov Telescope Array (CTA) observatory. In this framework tests are ongoing on innovative devices suitable to detect Cherenkov light in the blue and near-UV wavelength region, the so-called Near Ultra-Violet Silicon Photomultipliers (NUV SiPMs). The tests on photosensors produced by Fondazione Bruno Kessler (FBK) are revealing promising performance: low operating voltage, capability to detect very low intensity light down to a single photon and high Photo Detection Efficiency (PDE) in the range 390–410nm. In particular the developed device is a High Density NUV-SiPM (NUV-HD SiPM) based on a micro-cell of 30μm×30μm and 6mm×6mm area. Tests on this detector in single-cell configuration and in a matrix arrangement have been done. At the same time front-end electronics based on the waveform sampling technique optimized for the new NUV-HD SIPMs is under study and development.
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