•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.
Near UltraViolet High Density (NUV-HD) SiPMs produced by Fondazione Bruno Kessler in collaboration with INFN have been tested and characterized in INFN laboratories. The third generation of these ...devices (HD3) has proven to be suitable to equip the focal plane of the prototype Schwarzschild–Couder Medium Size Telescope (pSCT) proposed for the Cherenkov Telescope Array Observatory. Photosensors have been assembled in 4 16-pixel optical units coupled with TARGET–7 ASIC front-end electronics for amplification and digitization of the signal. At present, 9 modules have been successfully integrated on the pSCT camera and are currently taking data. In this contribution we report on the performances of the HD3 technology as single sensor and as assembled optical units, showing their performance and homogeneity in terms of gain and dark count rate.
The Schwarzschild Couder Medium Size Telescope prototype (pSCT) is going to test the Schwarzschild Couder solution proposed for Medium Size telescopes for the Cherenkov Telescope Array. The camera ...consists of 177 photodetection modules grouped into sectors of maximum 25 modules each. The sensitive elements of the modules, located in the focal plane of the telescope, are matrices of 64 6 mm × 6 mm pixels of Silicon Photomultipliers (SiPMs). The front-end electronics is designed for signal sampling technique using the TARGET-7 ASIC. The prototype under construction and test at the Fred Lawrence Whipple Observatory site will be equipped with the inner central sector fully operational. Sensors from Fondazione Bruno Kessler will be used for 9 of the 25 modules. A complete characterization of these very recent, highly sensitive Near UV sensors, the assembly procedure and metrology results on several focal plane elements has been conducted. Performances of the 16-sensors matrices and measurements with the TARGET-7 ASIC front-end coupled to FBK sensors will be shown and deeply discussed.
•A camera for the prototype Schwarzschild Couder Telescope for CTA is being tested.•A 16-FBK SiPM matrix was studied and its homogeneity was verified.•The TARGET 7 readout module was coupled and optimized to the FBK SiPMs.
Silicon Photomultipliers (SiPMs) are excellent devices to detect the faint and short Cherenkov light emitted in high energy atmospheric showers, and therefore suitable for use in imaging air ...Cherenkov Telescopes. The high density Near Ultraviolet Violet SiPMs (NUV-HD3) produced by Fondazione Bruno Kessler (FBK) in collaboration with INFN were used to equip optical modules for a possible upgrade of the Schwarzschild-Couder Telescope camera prototype, in the framework of the Cherenkov Telescope Array project. SiPMs are 6×6 mm
2
devices based on 40×40 μm
2
microcells optimized for photo-detection at the NUV wavelengths. More than 40 optical modules, each composed by a 4×4 array of SiPMs, were assembled. In this contribution we report on the development and on the assembly of the optical modules, their validation and integration in the camera.
Large-Area SiPM Pixels (LASiPs) in SPECT Wunderlich, C.; Guberman, D.; Paoletti, R. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
March 2023, 2023-03-00, Letnik:
1048
Journal Article
Recenzirano
A standard camera for Single Photon Emission Computed Tomography (SPECT) contains 50–100 photomultiplier tubes (PMTs). It is shielded by a thick layer of lead which makes it heavy and bulky. Its ...weight and size could be significantly reduced if replacing the PMTs by silicon photomultipliers (SiPMs). However, one would need a few thousands channels to fill a camera with SiPMs due to their small sensitive area. Alternatively, we propose to use Large-Area SiPM Pixels (LASiPs), built by summing individual currents of several SiPMs into a single output. We extended the simulation of a small camera employed with LASiPs that was presented in Guberman et al. (2021) to a large camera. The extension allowed us to study the feasibility of using larger LASiPs in a full-body SPECT camera. We found an intrinsic spatial resolution of ∼4 mm for a simulated pixel summing 25 SiPMs including SiPM noise at room temperature. Reducing the dark count rate (DCR) could improve the intrinsic spatial resolution to ∼3 mm.
•Simulations of large SPECT camera with SiPM pixels including noise.•Study of impact of pixel size, shape and noise on performance.•SiPM pixel of 9 cm2 provides acceptable spatial resolution.•Reducing dark counts by cooling improves significantly resolution.
Photo-Trap: A low-cost and low-noise large-area SiPM-based pixel Guberman, D.; Wunderlich, C.; Barillaro, G. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
December 2023, 2023-12-00, Letnik:
1057
Journal Article
Recenzirano
Odprti dostop
The small sensitive area of commercial silicon photomultipliers (SiPMs) is often the main limitation for their use in experiments and applications that require large detection areas. Since ...capacitance, dark count rate and cost increase with the SiPM size, they are rarely found in sizes larger than 6 × 6 mm2. Photo-Trap combines a wavelength-shifter plastic, a dichroic filter and a standard commercial SiPM to build pixels of a few cm2. With this approach it can collect light over an area that can be ∼10–100 times larger than the area of a commercial SiPM, while keeping the noise, single-photoelectron resolution, power consumption and likely the cost of a single small SiPM. We developed four different proof-of concept pixels sensitive in the near UV band, the largest one being of 40 × 40 mm2. We characterized them through laboratory measurements and Geant4 simulations. The optical gain we measured with the prototypes went from ∼5 to ∼15, while the single-photon time resolution was of ∼3–5 ns FWHM. With the achieved performance Photo-Trap could be a competitive low-cost alternative for applications that require photosensors with large collection areas and low noise, such as dark matter experiments and optical wireless communication.
ABSTRACT
We present a measurement of the extragalactic background light (EBL) based on a joint likelihood analysis of 32 gamma-ray spectra for 12 blazars in the redshift range z = 0.03–0.944, ...obtained by the MAGIC telescopes and Fermi-LAT. The EBL is the part of the diffuse extragalactic radiation spanning the ultraviolet, visible, and infrared bands. Major contributors to the EBL are the light emitted by stars through the history of the Universe, and the fraction of it that was absorbed by dust in galaxies and re-emitted at longer wavelengths.
The EBL can be studied indirectly through its effect on very high energy photons that are emitted by cosmic sources and absorbed via γγ interactions during their propagation across cosmological distances. We obtain estimates of the EBL density in good agreement with state-of-the-art models of the EBL production and evolution. The 1σ upper bounds, including systematic uncertainties, are between 13 per cent and 23 per cent above the nominal EBL density in the models. No anomaly in the expected transparency of the Universe to gamma-rays is observed in any range of optical depth. We also perform a wavelength-resolved EBL determination, which results in a hint of an excess of EBL in the 0.18–0.62 $\mu\mathrm{ m}$ range relative to the studied models, yet compatible with them within systematics.
In recent years, Silicon Photomultipliers (SiPMs) have proven to be highly suitable devices for applications where high sensitivity to low-intensity light and fast responses are required. Among their ...many advantages are their low operational voltage when compared with classical photomultiplier tubes, mechanical robustness, and increased photon detection efficiency (PDE).
Here we present a full characterization of a SiPM device technology developed in Italy by Fondazione Bruno Kessler, which is suitable for Cherenkov light detection in the Near-Ultraviolet (NUV) band. This device is a High-Density (HD) NUV SiPM, based on a microcell of 40μm×40μm and with an area of 6 × 6mm2, providing low levels of dark noise and high PDE peaking in the NUV band. This particular device has been selected to equip a part of the focal plane of the Schwarzschild–Couder Telescope (SCT) prototype proposed for the Cherenkov Telescope Array (CTA) Observatory.
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