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The Schwarzschild-Couder Telescope (SCT) is a medium-sized telescope technology proposed for the Cherenkov Telescope Array. It uses a novel dual-mirror optical design that removes comatic aberrations across its entire field of view. The SCT camera employs high-resolution silicon photomultiplier (SiPM) sensors with a pixel size of 4 arcminutes. A prototype SCT (pSCT) has been constructed at the Fred Lawrence Whipple Observatory in Arizona, USA. An observing campaign in 2020, with a partial camera of 1600 pixels (2.7 degrees by 2.7 degrees field of view) resulted in detection of the Crab Nebula at 8.6 sigma statistical significance. Work on the pSCT camera and optical system is ongoing to improve performance and prepare for an upcoming camera upgrade. The pSCT camera upgrade will replace the current camera modules with improved SiPMs and readout electronics and will expand the camera to its full design field of view of 8 degrees in diameter (11,328 pixels). The fully upgraded pSCT will enable next-generation very-high-energy gamma-ray astrophysics through excellent background rejection and angular resolution. In this presentation we describe first results from the successful operation of the pSCT and future plans., 9 pages, 3 figures, 2 tables, contribution to ICRC 2021, similar to 10.1016/j.astropartphys.2021.102562 (arXiv:2012.08448)

The Schwarzschild-Couder Telescope (SCT) is a telescope concept proposed for the Cherenkov Telescope Array. It employs a dual-mirror optical design to remove comatic aberrations over an $8^{\circ}$ field of view, and a high-density silicon photomultiplier camera (with a pixel resolution of 4 arcmin) to record Cherenkov emission from cosmic ray and gamma-ray initiated particle cascades in the atmosphere. The prototype SCT (pSCT), comprising a 9.7 m diameter primary mirror and a partially instrumented camera with 1536 pixels, has been constructed at the Fred Lawrence Whipple Observatory. The telescope was inaugurated in January 2019, with commissioning continuing throughout 2019. We describe the first campaign of observations with the pSCT, conducted in January and February of 2020, and demonstrate the detection of gamma-ray emission from the Crab Nebula with a statistical significance of $8.6\sigma$., Comment: 13 pages, 12 figures, 3 tables, submitted to Astroparticle Physics

A prototype Schwarzschild-Couder Telescope (pSCT) has been constructed at the Fred Lawrence Whipple Observatory as a candidate for the medium-sized telescopes of the Cherenkov Telescope Array Observatory (CTAO). CTAO is currently entering early construction phase of the project and once completed it will vastly improve very high energy gamma-ray detection component in multi-wavelength and multi-messenger observations due to significantly improved sensitivity, angular resolution and field of view comparing to the current generation of the ground-based gamma-ray observatories H.E.S.S., MAGIC and VERITAS. The pSCT uses a dual aspheric mirror design with a $9.7$ m primary mirror and $5.4$ m secondary mirror, both of which are segmented. The Schwarzschild-Couder (SC) optical system (OS) selected for the prototype telescope achieves wide field of view of $8$ degrees and simultaneously reduces the focal plane plate scale allowing an unprecedented compact ($0.78$m diameter) implementation of the high-resolution camera ($6$mm/ $0.067$deg per imaging pixel with $11,328$ pixels) based on the silicon photo-multipliers (SiPMs). The OS of the telescope is designed to eliminate spherical and comatic aberrations and minimize astigmatism to radically improve off-axis imaging and consequently angular resolution across all the field of view with respect to the conventional single-mirror telescopes. Fast and high imaging resolution OS of the pSCT comes with the challenging submillimeter-precision custom alignment system, which was successfully demonstrated with an on-axis point spread function (PSF) of $2.9$ arcmin prior to the first-light detection of the Crab Nebula in 2020. Ongoing and future commissioning activities are reported.

For the first time in the history of ground-based $\gamma$-ray astronomy, the on-axis performance of the dual mirror, aspheric, aplanatic Schwarzschild-Couder optical system has been demonstrated in a $9.7$-m aperture imaging atmospheric Cherenkov telescope. The novel design of the prototype Schwarzschild-Couder Telescope (pSCT) is motivated by the need of the next-generation Cherenkov Telescope Array (CTA) observatory to have the ability to perform wide ($\geq 8^{\circ}$) field-of-view observations simultaneously with superior imaging of atmospheric cascades (resolution of $0.067^{\circ}$ per pixel or better). The pSCT design, if implemented in the CTA installation, has the potential to improve significantly both the $\gamma$-ray angular resolution and the off-axis sensitivity of the observatory, reaching nearly the theoretical limit of the technique and thereby making a major impact on the CTA observatory sky survey programs, follow-up observations of multi-messenger transients with poorly known initial localization, as well as on the spatially resolved spectroscopic studies of extended $\gamma$-ray sources. This contribution reports on the initial alignment procedures and point-spread-function results for the challenging segmented aspheric primary and secondary mirrors of the pSCT., Comment: 19 pages, 11 figures, proceedings for SPIE Optical Engineering + Applications, 2020, Online Only

The Italian Institute of Nuclear Physics (INFN) is involved in the development of a prototype for a SiPM-based camera for the Cherenkov Telescope Array (CTA), a new generation of telescopes for ground - based gamma ray astronomy. In this framework, an R&D program for the development of SiPMs suitable for Cherenkov light detection (Near-Ultraviolet SiPMs) has been carried out. The developed device is a High Density NUV-SiPM based on a micro cell of 30 μ m × 30 μ m and 6 mm × 6 mm area produced by Fondazione Bruno Kessler (FBK). A full characterisation of the single SiPM will be presented and compared with the old technology (NUV-SiPM) and with other SiPMs commercially available. The NUV-HD SiPM will be tested in the pSCT (Schwarzschild-Couder Telescope prototype) for CTA which is leading to a camera concept based on 8 × 8 NUV-HD SiPM module as detection unit. An update on recent tests on the detectors arranged in this matrix configuration and on the front-end electronics will be given.

The first prototype of the Schwarzschild Couder Medium Size Telescope (pSCT) proposed for the CTA observatory has been installed in 2018 at the Fred Lawrence Whipple Observatory. The pSCT camera is composed of 25 modules with 64 channels each, covering only a small portion of the full focal plane of the telescope. The Italian Institute of Nuclear Physics (INFN) has developed and characterized in collaboration with Fondazione Bruno Kessler (FBK) a new generation of Silicon Photomultipliers (SiPMs) sensitive to the Near Ultraviolet wavelengths, based on the High Density technology (NUV-HD devices). The latest generation of 6×6 mm2 SiPMs (called NUV-HD3) have been used to equip a subsection of 9 out of 25 modules of the pSCT camera. An upgrade of this camera is foreseen between 2019 and 2020 using the same sensors, aiming to equip the full focal plane with 177 modules, for a total of more than 11000 pixels. We will present a full characterization of the performance of these devices, highlighting why they are suitable for Cherenkov light detection. An overview on the overall behavior of the installed sensors will be also given, providing information on the uniformity of the sensors and of the performance of the camera.

The third generation of Near Ultraviolet High Density (NUV-HD3) Silicon Photomultipliers (SiPMs) produced by Fondazione Bruno Kessler in collaboration with Istituto Nazionale di Fisica Nucleare (INFN) have been tested and characterized in INFN laboratories. Arrays of 16 pixels have been assembled to equip the focal plane of the prototype Schwarzschild-Couder Medium Size Telescope (pSCT) proposed for the Cherenkov Telescope Array Observatory. Each camera module is composed by 4 matrices of 16-pixel optical units coupled with TARGET-7 ASIC front-end electronics for signal amplification and digitization. A total of 9 modules have been successfully integrated on the pSCT camera and are currently taking data. In this contribution we provide a summary of the performances of the HD3 technology as measured in the INFN laboratories. We also report on the laboratory tests performed on the assembled optical units, showing their performances and homogeneity in terms of gain, signal-to-noise ratio and dark count rate.

Recent developments on Silicon Photomultipliers (SiPMs) have shown that they are particularly adequate to detect fast signal due to low-intensity light. Fondazione Bruno Kessler (FBK) has optimized these sensors for the Near-Ultraviolet Cherenkov light emitted by high energy gamma-ray showers in the atmosphere. The FBK high density SiPMs (NUV-HD) have been extensively characterized in the laboratories of the Italian Institute of Nuclear Physics (INFN) in view of equipping the focal plane camera of the Schwarzschild–Couder Telescope prototype (pSCT) in the framework of the Cherenkov Telescope Array (CTA). Here we report the performances of the 6 × 6 mm 2 SiPMs based on 40 × 40 μm 2 cells, in terms of gain and signal-to-noise ratio. We compare the results obtained on devices from the latest generation and grown on different substrates in order to choose the most suitable sensor for the pSCT camera.

The Italian Institute of Nuclear Physics (INFN) is currently involved in the R&D for the integration of Fondazione Bruno Kessler (FBK) Silicon Photomultipliers (SiPM) in the focal plane camera for the prototype of the Schwarzschild–Couder Telescope (pSCT) proposed to integrate the Cherenkov Telescope Array (CTA) observatory . High density FBK SiPMs optimized for the detection of Near Ultraviolet Cherenkov light (NUV-HD) will be used to equip the camera, coupled to the TARGET-7 readout electronics. A first production of 9 INFN modules is being tested and will be installed on the focal plane of the pSCT camera. Each module consists of 64 6 mm × 6 mm pixels, based on 40 μ m × 40 μ m microcells, arranged in 16-pixel matrices. The front-end electronics is based on the TARGET-7 ASIC, a 16-channel chip for sampling and digitization of the signal. Here we report measurements of the performances of the complete readout chain, including results regarding homogeneity in terms of gain and signal-to-noise ratio .

Silicon Photomultipliers are particularly suitable as optical units of Imaging Air Cherenkov Telescopes to detect the fast and low-intensity Cherenkov signal emitted by high energy atmospheric showers. The third generation of high density NUV SiPMs (NUV-HD3) produced by Fondazione Bruno Kessler (FBK) in collaboration with INFN have been used to equip optical modules intended to be integrated on a possible upgrade of the focal plane camera of the Schwarzschild-Couder Telescope prototype (pSCT) in the framework of the Cherenkov Telescope Array (CTA) project. NUV-HD3 SiPMs are 6 × 6 mm2 devices based on 40 × 40 μm2 microcells with excellent photo detection efficiency for the NUV wavelengths. Optical modules, each composed of a matrix of 4 × 4 SiPMs, have been assembled and tested in the laboratories of INFN to be integrated on the pSCT camera. In this contribution we report on the development and on the assembly of the optical modules, on their validation and on their integration on the pSCT camera.

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.

The purpose of the MU-RAY project is to develop an innovative approach to the study of volcanoes and their monitoring based on a particle physics approach.The test site is Vesuvio: one of the higher risk volcanoes in the world. In this context, muon radiography is an innovative method of enormous impact. This is an imaging technique which relies on the measurement, by means of a cosmic ray telescope, of the absorption in the volcano of muons with near-horizontal trajectories, produced by the interactions of cosmic rays with the atmosphere. Since 2003 this technique has been successfully used on volcanoes in Japan, providing pictures of their vertices with resolutions much better than those obtained with the traditional techniques based on gravimeters. Researchers from Naples and Florence are currently involved in the construction and testing of a prototype telescope based on the use of bars of plastic scintillator with a triangular section whose scintillation light is collected by special fibres (wavelength shifters) and transported to SiPM (Silicon photomultipliers). A complete prototype telescope, consisting of three xy scintillation planes and 1 m2 active area has been assembled and is now under test. © 2012 Elsevier B.V. All rights reserved.

Recen% developed near W-photosensors are currently adopted in those applications where high sensitivity and good imaging capabilities are required, especially in fields such as astroparticle physics and medical imaging. An example of such applications is the camera of the Schwarzschild Couder Medium Size Telescope prototype (pSCT) which is in construction within the Cherenkov Telescope Array experiment. The camera consists of 177 photo-detection modules grouped into sectors of 25 modules, each based on matrixes of 64 6mm × 6mm pixels of SiUcon PhotomultipUers (SiPMs). Sensors produced by the Fondazione Bruno Kessler (FBK) in Italy are currently under investigation. Here we present a complete characterization of these highly sensitive near UV sensors, the assembly procedure and metrology results on several focal plane elements.

The MURAVES detector is a 4 m2 muon tracker equipped with a low power consumption electronic and designed to work in volcanic areas. Due to the great amount of channels (~1500) the detector is equipped with a multilayer electronic for data acquisition. It consists of 12 slave boards and 1 master board per square meter of detector and a single Rasp- berry Pi board that rules the whole set of one-square-meter detectors. Be- cause of this modularity, we can enlarge in principle the detector surface by adding more one-square-meter elements. In the present work, we re- sume the main features of the MURAVES detector designed for the muog- raphy of volcanoes and, more generally, for the imaging of the underground. We focus on the capability to fine tune every single channel of the detector and the precise measure of the time of flight of the muons. The latter uses a time expansion technique and it should allow us to make a background rejection never obtained until now.

Silicon Photomultipliers (SiPM) are standard sensors widely employed for applications in which high sensitivities and fast responses in the detection of low fluxes of visible and UV photons are required. The Italian Institute of Nuclear Physics (INFN), in collaboration with Fondazione Bruno Kessler (FBK), is involved in a R&D project for SiPM sensors sensitive to near UV wavelengths. The performances of the latest technology of NUV-High-Density SiPM have confirmed that the quality of the current production technology opens the possibility to employ these devices for many applications. In this contribution, we review the performances of the latest technology of NUV-High-Density SiPM and the prospects for their use in one of the designs of the camera focal planes of Schwarschild-Couder Telescope prototype, including the development of packaging procedures of single sensors into high-density multi-SiPM modules and the development of a custom front-end ASIC for a high rate waveform sampling of the SiPM signals.

The MURAVES project aims to study the inner structure of the upper part of the Mt. Vesuvius volcano by muon radiography (muography) technique. Very high energy muons, produced by cosmic rays in the at- mosphere, can penetrate large thickness of rocks. By measuring the at- tenuation of the muons flux trough the volcano cone is possible to obtain a 2D image of the density structure. Internal discontinuities, with a spa- tial resolution of about 10 m, can be, in principle, resolved. An absolute average density measurement can be provided too. The project, funded by the Italian Ministry of University, Research and Education (MIUR), is led by INGV and INFN. In this article the mechanical structure of the de- tectors and background suppression techniques are reported.

The development of a new camera based on the use of Silicon Photomultipliers (SiPM) proposed for the Cherenkov Telescope Array (CTA), which represents a new generation of ground based very high energy gamma ray observatory, is one of the main items of the Italian Institute of Nuclear Physics (INFN). In the R&D framework a single channel electronic charge preamplifier has been developed to improve the performance of photon cameras equipped with High Density NUV – HD SiPM produced by Fondazione Bruno Kessler (FBK) with a micro cell of 30 μm x 30 μm and 6 mm x 6 mm total area. The single channel preamplifier will be used as basic component for a 16-channel electronic board prototype to test the 8 x 8 NUV – HD SiPM modules proposed to equip a pSCT (Schwarzschild-Couder Telescope prototype) camera. In this work the results of tests on the single channel preamplifier prototype to optimize the SiPM performances will be presented.

The Cherenkov Telescope Array (CTA) will be the next generation of ground-based observatory of very high energy gamma ray sources. The Italian Institute of Nuclear Physics (INFN) is involved in the R&D effort for the development of a possible solution for one of the Cherenkov photon camera designs, working on replacing the Hamamatsu MPPC S12642-0404PA-50 with more UV sensitive ones from Fondazione Bruno Kessler (FBK). INFN is currently developing the preamplifiers and the carrier boards for the SiPM chips that interface with the mechanics of the camera. To test the feasibility and the performance of SiPM cameras, a focal plane camera prototype module, upgraded with High Density NUV - SiPMs, produced by FBK, with a micro cell of 30 μm x 30 μm and 6 mm x 6 mm area, is being assembled. In this work, we describe the SiPM carrier boards, the assembly process and the qualification tests performed, before and after assembly, on the focal plane modules to qualify the procedures.

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 mm2 devices based on 40×40 μm2 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.

The Schwarzschild-Couder Telescope (SCT) is a candidate technology for a medium-sized telescope within the Cherenkov Telescope Array, the next generation ground based observatory for very high energy gamma ray astronomy. The SCT uses a novel two-mirror design and is expected to yield improvements in field of view and image resolution compared to traditional Cherenkov telescopes based on single-mirror-dish optics. To match the improved optical resolution, challenging requirements of high channel count and density at low power consumption must be overcome by the camera. The prototype camera, currently commissioned and tested on the prototype SCT, has been developed based on millimeter scale SiPM pixels and a custom high density digitizer ASIC, TARGET, to provide 1600 pixels spanning a 2.7 degree field of view while being able to sample nanosecond photon pulses. It is mechanically designed to allow for an upgrade to 11,328 pixels covering a field of view of 8 degrees and demonstrating the full potential of the technology. The camera was installed on the telescope in 2018. We will present its design and performance including first light data., Comment: ICRC 2019 Proceeding

The Cherenkov Telescope Array (CTA), with more than 100 telescopes, will be the largest ever ground-based gamma-ray observatory and is expected to greatly improve on both gamma-ray detection sensitivity and energy coverage compared to current-generation detectors. The 9.7-m Schwarzschild-Couder telescope (SCT) is one of the two candidates for the medium size telescope (MST) design for CTA. The novel aplanatic dual-mirror SCT design offers a wide field-of-view with a compact plate scale, allowing for a large number of camera pixels that improves the angular resolution and reduce the night sky background noise per pixel compared to the traditional single-mirror Davies-Cotton (DC) design of ground-based gamma-ray telescopes. The production, installation, and the alignment of the segmented aspherical mirrors are the main challenges for the realization of the SCT optical system. In this contribution, we report on the commissioning status, the alignment procedures, and initial alignment results during the initial commissioning phase of the optical system of the prototype SCT., 8 pages, PoS proceedings 36th ICRC 2019 Madison