The ASTRI-Horn telescope has been developed under the leadership of the Italian National Institute for Astrophysics (INAF) as a prototype of a compact aplanatic dual-mirror (4 m diameter) Imaging Atmospheric Cherenkov Telescope (IACT) with a large FoV (8◦). It is the pathfinder of the small-size telescopes adopted for both the ASTRI Mini-Array (Tenerife, Canary Islands) and the SST/CTA array (Paranal, Chile) to perform 1-200 TeV gamma-ray astronomy with an unprecedented combination of high angular/energy resolution and flux sensitivity across a large Field of View. ASTRI-Horn is a complete end-to-end system; since 2014 it is installed in Italy at the INAF "M.G. Fracastoro" observing station (Mt. Etna, Sicily). The telescope already successfully demonstrated, first time ever, the optical behavior of a dual-mirror Schwarzschild-Couder telescope as a Cherenkov system, and also obtained the first gamma-ray source detection, the Crab Nebula. During 2020-2022, ASTRI-Horn - which operates in a harsh environment on an active volcano - has been subject to significant maintenance and refurbishment to restore systems and improve performance. Mirrors have been substituted, adopting high-performance new-recipe coatings, and the camera electronics has been further optimized. Now the telescope is extensively used for cosmic rays, gamma rays, and muon-radiography of the Etna volcano investigations.

ASTRI-Horn is an imaging atmospheric Cherenkov telescope developed by the Italian National Institute for Astrophysics (INAF), installed at the Serra La Nave Astronomical Station on Mount Etna (Italy). ASTRI-Horn detected the Crab proving the validity of its innovative camera and of the dual mirror configuration. Henceforth the telescope will play another important role. It will be the test bench for the upcoming cameras to be adopted for the ASTRI Mini-Array, a project led by INAF to build and operate an array of nine Cherenkov telescopes at the Observatorio del Teide (Tenerife, Spain). Moreover, the ASTRI-Horn camera will be used to test new technological solutions and explore innovative Cherenkov observation techniques. The Cherenkov camera uses Silicon-Photo Multiplier (SiPM) detectors. The fast front-end electronics implemented in the CITIROC ASIC is based on a custom peak-detector mode, which measures the electric pulses generated by the Cherenkov light flashes. The compact camera embeds all the components of a reliable thermal cooling system. This contribution gives a description of the upgrades of the ASTRI-Horn camera, which are the results of the lesson learnt during these years of sky observations. The improvements aim at correcting the drawbacks detected so far and at increasing the overall performance of the camera. The main ones are the increment of the power supplied to the photodetectors, the redesign of the Lids kinematic chain, a more efficient embedded calibration system, new control software routines and GUI.

This paper presents a systematic analytical comparison of the single‐Miller capacitor frequency compensation techniques suitable for three‐stage complementary metal–oxide–semiconductor (CMOS) operational transconductance amplifiers (OTAs). The comparison is carried out with the aid of a figure of merit that expresses a trade‐off among gain‐bandwidth product, load capacitance, and total transconductance, for equal values of the phase margin. The results found can be used before the transistor‐level design step and provide useful guidelines for the optimization of the small‐signal performance. Simulations by using a 65‐nm standard CMOS technology confirming the effectiveness of the theoretical comparison for 10 different OTA topologies are also provided.

The observation of energetic astronomical sources emitting very high-energy gamma-rays in the TeV spectral range (as e.g. supernova remnants or blazars) is mainly based on detecting the Cherenkov light induced by relativistic particles in the showers produced by the photon interaction with the Earth atmosphere. The ASTRI Mini-Array is an INAF-led project aimed observing such celestial objects in the 1 - 100 TeV energy range. It consists of an array of nine innovative imaging atmospheric Cherenkov telescopes that are an evolution of the dual-mirror aplanatic ASTRI-Horn telescope operating at the INAF "M.C. Fracastoro" observing station (Serra La Nave, Mount Etna, Italy). The ASTRI Mini-Array is currently under construction at the Observatorio del Teide (Tenerife, Spain). In this paper, we present the compact (diameter 660mm, height 520mm, weight 73kg) ASTRI-Horn prototype Cherenkov Camera based on a modular multipixel Silicon Photon Multiplier (SiPM) detector, has been acquiring data since 2016 and allowing us to obtain both scientific data and essential lessons. In this contribution, we report the main features of the camera and its evolution toward the new Cherenkov camera, which will be installed on each ASTRI Mini-Array telescope to cover an unprecedented field of view of 10.5°.

Astri-Horn is a Small-Sized Telescope (SST) for very-high energy gamma-ray astronomy installed in Italy at the INAF "M.C. Fracastoro" observing station (Mt. Etna, Sicily). The ASTRI-Horn telescope is characterized by a dual-mirror optical system and a curved focal surface covered by SiPM sensors managed by a innovative fast front-end electronics. Dedicated studies were performed to verify the feasibility of the calibration through muons on the relatively small size of the primary mirror (~4 m diameter), as in the case of larger Cherenkov telescopes. A number of tests were performed using simulations of the atmospheric showers with the CORSIKA package and of the telescope response with a dedicated simulator. In this contribution we present a preliminary analysis of muon events detected by ASTRI-Horn during the regular scientific data taking performed in December 2018 and March 2019. These muon events validate the results obtained with the simulations and definitively confirm the feasibility of calibrating the ASTRI-Horn SST telescope with muons.

We report on the first detection of very high-energy gamma-ray emission from the Crab Nebula by a Cherenkov telescope in dual-mirror Schwarzschild-Couder (SC) configuration. This result has been achieved by means of the 4 m ASTRI-Horn telescope, operated on Mt. Etna, Italy, and developed in the context of the Cherenkov Telescope Array Observatory preparatory phase. The dual-mirror SC design is aplanatic and characterized by a small plate scale, which allows us to implement large cameras with a large field of view, with small-size pixel sensors and a high level of compactness. The curved focal plane of the ASTRI camera is covered by silicon photo-multipliers, managed by an unconventional front-end electronic system that is based on a customized peak-sensing detector mode. The system includes internal and external calibration systems, hardware and software for control and acquisition, and the complete data archiving and processing chain. These observations of the Crab Nebula were carried out in December 2018 during the telescope verification phase for a total observation time (after data selection) of 24.4 h, equally divided between on- and off-axis source exposure. The camera system was still under commission and its functionality was not yet completely exploited. Furthermore, due to recent eruptions of the Etna Volcano, the mirror reflection efficiency was reduced. Nevertheless, the observations led to the detection of the source with a statistical significance of 5.4σ above an energy threshold of ∼3 TeV. This result provides an important step toward the use of dual-mirror systems in Cherenkov gamma-ray astronomy. A pathfinder mini-array based on nine ASTRI-like telescopes with a large field-of-view is in the course of implementation.

ASTRI-Horn is a prototypal telescope of an imaging atmospheric Cherenkov telescope developed by the Italian National Institute of Astrophysics (INAF), proposed for the Cherenkov Telescope Array (CTA) Observatory. The CTA Observatory represents the next generation of imaging atmospheric Cherenkov telescopes and will explore the very high-energy domain from a few tens of GeV up to few hundreds of TeV. It will be composed of large-, medium-, and small-sized telescopes; ASTRI-Horn is an end-to-end prototype proposed for the Small Sized array. The main scientific instrument of the ASTRI-Horn telescope is an innovative and compact Camera with Silicon-Photomultiplier based detectors and a specifically designed fast read-out electronics based on a custom peak-detector mode. The thermo-mechanical assembly is designed to host both the entire electronics chain, from the sensors to the raw data transmission system and the calibration system, and the complete thermoregulation system. This contribution gives a high level description of the T/M and electrical design of the Cherenkov Camera, it describes the assembling procedure of its different subsystems and their integration into the complete camera system. A discussion about possible design improvements coming from the problems/difficulties encountered during assembly is also presented. Finally, results from engineering tests conducted in-field are also presented.

The Cherenkov Telescope Array (CTA) foresees, in its southern site (Chile), the implementation of up to 70 small-sized telescopes (SSTs), which will extend the energy coverage up to hundreds of TeV. It has been proposed that one of the first set of CTA SSTs will be represented by the ASTRI mini-array, which includes (at least) nine ASTRI telescopes. The end-to-end prototype of such telescopes, named the ASTRI SST-2M, is installed in Italy and it is now completing the overall commissioning and entering the science verification phase. ASTRI telescopes are characterized by an optical system based on a dual-mirror Schwarzschild-Couder design and a camera at the focal plane composed of silicon photomultiplier sensors managed by a fast read-out electronics specifically designed. Based on a custom peak-detector mode, the ASTRI camera electronics is designed to perform Cherenkov signal detection, trigger generation, digital conversion of the signals and data transmission to the camera server. In this contribution we will describe the main features of the ASTRI camera, its performance and results obtained during the commissioning phase of the ASTRI SST-2M prototype in view of the ASTRI mini-array implementation.

The design of a power-efficient three-stage CMOS operational amplifier capable of driving extremely high capacitive loads is proposed. The compensation network entails only a single Miller capacitor, thus avoiding the use of additional transistor and current consumption. Theoretical analysis is reported and an implementation in a 0.35-μm technology is presented and simulated. A 1.46-MHz gain-bandwidth product is achieved with a 10-nF load, while consuming only 8.54 μW from 1.4-V supply. As compared to other previously reported solutions, the amplifier shows a remarkable increase in small-signal and large-signal performance.

This brief presents a low-power, area-efficient three-stage CMOS operational transconductance amplifier (OTA) suitable for very large capacitive loads, ${C} _{L}$ . A single Miller capacitor and an inverting current buffer embedded in the input stage are exploited to implement the frequency compensation network. An additional feed-forward path and a slew rate enhancer are also utilized to improve the large-signal transient response. Detailed small-signal analysis reveals that the proposed OTA does not exhibit an upper limit of drivable ${C} _{L}$ . The OTA is fabricated in a standard 0.35- ${\mu }\text{m}$ technology and occupies 0.0027 mm2 of die area. Under 1.4-V supply and 6.36- ${\mu }\text{A}$ quiescent current consumption, it provides a dc gain greater than 110 dB and is stable for any ${C} _{L}$ larger than 5 nF. Comparison with the state of the art shows remarkable improvement of both small- and large-signal performance.

This brief presents a low-power, area-efficient three-stage CMOS operational transconductance amplifier (OTA) suitable for very large capacitive loads, ${C} _{L}$ . A single Miller capacitor and an inverting current buffer embedded in the input stage are exploited to implement the frequency compensation network. An additional feed-forward path and a slew rate enhancer are also utilized to improve the large-signal transient response. Detailed small-signal analysis reveals that the proposed OTA does not exhibit an upper limit of drivable ${C} _{L}$ . The OTA is fabricated in a standard 0.35- ${\mu }\text{m}$ technology and occupies 0.0027 mm2 of die area. Under 1.4-V supply and 6.36- ${\mu }\text{A}$ quiescent current consumption, it provides a dc gain greater than 110 dB and is stable for any ${C} _{L}$ larger than 5 nF. Comparison with the state of the art shows remarkable improvement of both small- and large-signal performance.

Cosmic ray tomography is a technique which exploits the multiple Coulomb scattering of highly penetrating cosmic ray-produced muons to perform non-destructive inspection of high-Z materials without the use of artificial radiation. A muon tomography detection system can be used as a portal monitor at border crossing points for detecting illegal targeted objects. The Muon Portal Project is a joint initiative between Italian research and industrial partners, aimed at the construction of a real size detector prototype (6×3×7m3) for the inspection of cargo containers by the muon scattering technique. The detector consists of four XY tracking planes, two placed above and two below the container to be inspected. After a research and development phase, which led to the choice and test of the individual components, the construction and installation of the detection modules is almost completed. In this paper the present status of the Project is reported, focusing on the design and construction phase, as well as on the preliminary results obtained with the first detection planes.

This brief presents a low-power, area-efficient three-stage CMOS operational transconductance amplifier (OTA) suitable for very large capacitive loads, CL. A single Miller capacitor and an inverting current buffer embedded in the input stage are exploited to implement the frequency compensation network. An additional feed-forward path and a slew rate enhancer are also utilized to improve the large-signal transient response. Detailed small-signal analysis reveals that the proposed OTA does not exhibit an upper limit of drivable CL. The OTA is fabricated in a standard 0.35-mu m technology and occupies 0.0027 mm(2) of die area. Under 1.4-V supply and 6.36-mu A quiescent current consumption, it provides a dc gain greater than 110 dB and is stable for any CL larger than 5 nF. Comparison with the state of the art shows remarkable improvement of both small-and large-signal performance.

ASTRI SST-2M is one of the prototypes of the small size class of telescopes proposed for the Cherenkov Telescope Array. Its optical design is based on a dual-mirror Schwarzschild-Couder configuration, and the camera is composed by a matrix of monolithic multipixel silicon photomultipliers managed by ad-hoc tailored front-end electronics. This paper describes the procedures for the gain calibration on the ASTRI SST-2M. Since the SiPM gain depends on the operative voltage and the temperature, we adjust the operative voltages for all sensors to have equal gains at a reference temperature. We then correct gain variations caused by temperature changes by adjusting the operating voltage of each sensor. For that purpose the SiPM gain dependence on operating voltage and on temperature have been measured. In addition, we present the calibration procedures and the results of the experimental measurements to evaluate, for each pixel, the parameters necessary to make the trigger uniform over the whole focal plane.

List of contributions from the Cherenkov Telescope Array Consortium presented at the 35th International Cosmic Ray Conference, July 12-20 2017, Busan, Korea.

Silicon photomultiplier (SiPM) detectors are emerging semiconductor devices addressing the challenge of low-light detection for single-photon counting contexts. High-performance SiPM front-end electronics requires availability of reliable electrical models. Many accurate SiPM models have matured in recent years; nevertheless, circuit parameter extraction is fairly burdensome and involves extensive measurement phases to be executed. Starting from a recently developed model of a SiPM detector coupled to the read-out electronics, a new and effective analytical procedure is proposed in this paper for extracting the SiPM electrical parameters from experimental measurements. This original technique is applied to a real 3×3-mm 2 SiPM detector, and validation is confirmed by a good agreement between simulations and measurements. Furthermore, independent cross-check validation based on experimental tests is carried out, corroborating the effectiveness of the adopted extraction procedure.

The Muon Portal Project has built a prototype of a real size detector (6 m x 3 m x 7 m) for the inspection of containers by muon tomography. This technique may provide 2D and 3D images of the interior of a container, to identify the presence of high-Z. materials. In the present Project, 4800 extruded scintillator strips were arranged such as to cover four X-Y detection planes (6 m x 3 m), two placed above and two below the container to be inspected. Silicon photomultipliers were used as photosensors, to collect the light transported by Wave Length Shifter (WLS) fibres embedded in the scintillator strips. First tomographic images are here presented. (C) 2017 Elsevier B.V. All rights reserved.

In this letter, a recently published model of silicon photomultiplier (SiPM) sensors is profitably extended to include the important effects of the read-out electronics on the shape of the output pulse waveforms. An improved analytical expression has been developed, also accounting for the loading effect and bandwidth limitation of the coupled front-end, through which the SiPM dynamic response can be accurately reproduced and predicted. Experimental tests on actual detection systems corroborate the SiPM model and the analytical results.

This paper introduces a new effective single-Miller capacitor compensation topology for three-stage amplifiers with very large capacitive loads, realized through an active-feedback capacitor together with an inner half-feedforward stage. Moreover, an optimized design strategy which profitably exploits the two left half-plane zeros is presented. To improve the amplifier large signal transient response, the topology also includes an external feedforward path, that only marginally affects the frequency compensation, and a novel slew-rate enhancer section. To validate the solutions presented, a three-stage OTA driving a 10-nF load has been designed and implemented in a standard 0.35-μm CMOS technology. The amplifier occupies less than 0.003-mm2 of die area, provides 2.7-MHz gain-bandwidth product and 0.55-V/μs average slew-rate, while consuming only 25-μA quiescent current.