The Cherenkov Telescope Array Observatory (CTAO) will include telescopes of three different sizes, the smallest of which are the Small-Sized Telescopes (SSTs). In particular, the SSTs will be installed at the southern site of CTAO, on the Chilean Andes, and will cover the highest energy range of CTAO (up to ~300 TeV). The SSTs are developed by an international consortium of institutes that will provide them as an in-kind contribution to CTAO. The optical design of the SSTs is based on a Schwarzschild-Couder-like dual-mirror polynomial configuration, with a primary aperture of 4.3m diameter. They are equipped with a focal plane camera based on SiPM detectors covering a field of view of ~9°. The preliminary design of the SST telescopes was evaluated and approved during the Product Review (PR) organised with CTAO in February 2023. The SST project is now going through a consolidation phase leading to the finalisation and submission of the final design to the Critical Design Review (CDR), expected to occur late 2024, after which the production and construction of the telescopes will begin leading to a delivery of the telescopes to CTAO southern site starting at the end of 2025-early 2026 onward. In this contribution we will present the progress of the SST programme, including the results of the PDR, the consolidation phase of the project and the plan up to the on-site integration of the telescopes.
KEYWORDS: Software development, Telescopes, Data modeling, Computer architecture, Control systems, Atmospheric Cherenkov telescopes, Data acquisition, Data archive systems, Design, Cameras
The Astrophysics with Italian Replicating Technology Mirrors (ASTRI) Mini-Array is an international collaboration led by the Italian National Institute for Astrophysics (INAF) and devoted to imaging atmospheric Cherenkov light for very-high γ-ray astrophysics, detection of cosmic-rays, and stellar Hambury-Brown intensity interferometry. The project is deploying an array of nine dual-mirror aplanatic imaging atmospheric Cherenkov telescopes of 4-m class at the Teide Observatory on Tenerife in the Canary Islands. Based on SiPM sensors, the focal plane camera covers an unprecedented field of view of 10.5 deg in diameter. The array is most sensitive to γ-ray radiation above 1 up to 200 TeV, with an angular resolution of 3 arcmin, better than the current particle arrays, such as LHAASO and HAWC. We describe the overall software architecture of the ASTRI Mini-Array and the software engineering approach for its development. The software covers the entire life cycle of the Mini-Array, from scheduling to remote operations, data acquisition, and processing until data dissemination. The on-site control software allows remote array operations from different locations, including automated reactions to critical conditions. All data are collected every night, and the array trigger is managed post facto. The high-speed networking connection between the observatory site and the Data Center in Rome allows for ready data availability for stereoscopic event reconstruction, data processing, and almost real-time science products generation.
The Cherenkov Telescope Array Observatory (CTAO) consists of three types of telescopes: large-sized (LST), mediumsized (MST), and small-sized (SST), distributed in two observing sites (North and South). For the CTA South “Alpha Configuration” the construction and installation of 37 (+5) SST telescopes (a number that could increase up to 70 in future upgrades) are planned. The SSTs are developed by an international consortium of institutes that will provide them as an in-kind contribution to CTAO. The SSTs rely on a Schwarzschild-Couder-like dual-mirror polynomial optical design, with a primary mirror of 4 m diameter, and are equipped with a focal plane camera based on SiPM detectors covering a field of view of ~9°. The current SST concept was validated by developing the prototype dual-mirror ASTRI-Horn Cherenkov telescope and the CHEC-S SiPM focal plane camera. In this contribution, we will present an overview of the SST key technologies, the current status of the SST project, and the planned schedule.
Domenico della Volpe, Imen Al Samarai, Cyril Alispach, Tomasz Bulik, Jerzy Borkowski, Franck Cadoux, Victor Coco, Yannick Favre, Mira Grudzińska, Matthieu Heller, Marek Jamrozy, Jerzy Kasperek, Etienne Lyard, Emil Mach, Dusan Mandat, Jerzy Michałowski, Rafal Moderski, Teresa Montaruli, Andrii Neronov, Jacek Niemiec, T. R. Njoh Ekoume, Michal Ostrowski, Paweł Paśko, Miroslav Pech, Pawel Rajda, Jakub Rafalski, Petr Schovanek, Karol Seweryn, Krzysztof Skowron, Vitalii Sliusar, Łukasz Stawarz, Magdalena Stodulska, Marek Stodulski, Petr Travnicek, Isaac Troyano Pujadas, Roland Walter, Adam Zagdański, Krzysztof Zietara
KEYWORDS: Atmospheric Cherenkov telescopes, Telescopes, Cameras, Electronics, Mirrors, Atmospheric optics, Solar concentrators, Digital electronics, Signal processing, Field programmable gate arrays
The Cherenkov Telescope Array (CTA) will explore with unprecedented precision the Universe in the gammaray domain covering an energy range from 50 GeV to more the 300 TeV. To cover such a broad range with a sensitivity which will be ten time better than actual instruments, different types of telescopes are needed: the Large Size Telescopes (LSTs), with a ∼24 m diameter mirror, a Medium Size Telescopes (MSTs), with a ∼12 m mirror and the small size telescopes (SSTs), with a ∼4 m diameter mirror. The single mirror small size telescope (SST-1M), one of the proposed solutions to become part of the small-size telescopes of CTA, will be equipped with an innovative camera. The SST-1M has a Davies-Cotton optical design with a mirror dish of 4 m diameter and focal ratio 1.4 focussing the Cherenkov light produced in atmospheric showers onto a 90 cm wide hexagonal camera providing a FoV of 9 degrees. The camera is an innovative design based on silicon photomultipliers (SiPM ) and adopting a fully digital trigger and readout architecture. The camera features 1296 custom designed large area hexagonal SiPM coupled to hollow optical concentrators to achieve a pixel size of almost 2.4 cm. The SiPM is a custom design developed with Hamamatsu and with its active area of almost 1 cm2 is one of the largest monolithic SiPM existing. Also the optical concentrators are innovative being light funnels made of a polycarbonate substrate coated with a custom designed UV-enhancing coating. The analog signals coming from the SiPM are fed into the fully digital readout electronics, where digital data are processed by high-speed FPGAs both for trigger and readout. The trigger logic, implemented into an Virtex 7 FPGA, uses the digital data to elaborate a trigger decision by matching data against predefined patterns. This approach is extremely flexible and allows improvements and continued evolutions of the system. The prototype camera is being tested in laboratory prior to its installation expected in fall 2017 on the telescope prototype in Krakow (Poland). In this contribution, we will describe the design of the camera and show the performance measured in laboratory.
J. Aguilar, W. Bilnik, J. Borkowski, F. Cadoux, A. Christov, D. della Volpe, Y. Favre, M. Heller, J. Kasperek, E. Lyard, A. Marszalek, R. Moderski, T. Montaruli, A. Porcelli, E. Prandini, P. Rajda, M. Rameez, E. jr. Schioppa, I. Troyano Pujadas, K. Ziętara, J. Blocki, L. Bogacz, T. Bulik, M. Curyło, M. Dyrda, A. Frankowski, Ł. Grudniki, M. Grudzinska, B. Idźkowski, M. Jamrozy, M. Janiak, K. Lalik, E. Mach, D. Mandat, J. Michalowski, A. Neronov, J. Niemiec, M. Ostrowski, P. Paśko, M. Pech, P. Schovanek, K. Seweryn, K. Skowron, V. Sliusar, M. Sowinski, Ł. Stawarz, M. Stodulska, M. Stodulski, S. Toscano, R. Walter, M. Więcek, A. Zagdański, P. Żychowski
The single mirror Small Size Telescope (SST-1M) project proposes a design among others for the smallest type of telescopes (SST), that will compose the south observatory of the Cherenkov Telescope Array (CTA). The SST camera collecting the Cherenkov light resulting from very high energy gamma-ray interactions in the atmosphere proposes to use Silicon PhotoMultipliers (SiPM). The SST-1M design has led to the use of unique pixel shape and size that required a dedicated development by the University of Geneva and Hamamatsu. An active surface of ~94 mm2 and a resulting total capacitance of ~3.4 nF combined with the stringent requirements of the CTA project on timing and charge resolution have led the University of Geneva to develop a custom preamplifier stage and slow-control system. The design and performance of the tailor made preamplifier stage and of the slow control electronics will be briefly described. The bias circuit of the sensor contains a resistor meant to prevent the sensor from drawing high current. However this resistor also introduces a voltage drop at the sensor input impacting the stability of its operation. A model has been developed in order to derive the parameters needed to account for it at the data analysis level. A solution based on the SST-1M front-end and digital readout is proposed to compensate for the voltage drop at the sensor cathode.
J. Aguilar, W. Bilnik, J. Borkowski, F. Cadoux, A. Christov, D. della Volpe, Y. Favre, M. Heller, J. Kasperek, E. Lyard, A. Marszałek, R. Moderski, T. Montaruli, A. Porcelli, E. Prandini, P. Rajda, M. Rameez, E.jr Schioppa, I. Troyano Pujadas, K. Ziętara, J. Blocki, L. Bogacz, T. Bulik, A. Frankowski, M. Grudzinska, B. Idźkowski, M. Jamrozy, M. Janiak, K. Lalik, E. Mach, D. Mandat, J. Michałowski, A. Neronov, J. Niemiec, M. Ostrowski, P. Paśko, M. Pech, P. Schovanek, K. Seweryn, K. Skowron, V. Sliusar, L. Stawarz, M. Stodulska, M. Stodulski, S. Toscano, R. Walter, M. Wiȩcek, A. Zagdański
The Small Size Telescope with Single Mirror (SST-1M) is one of the proposed types of Small Size Telescopes (SST) for the Cherenkov Telescope Array (CTA). The CTA south array will be composed of about 100 telescopes, out of which about 70 are of SST class, which are optimized for the detection of gamma rays in the energy range from 5 TeV to 300 TeV. The SST-1M implements a Davies-Cotton optics with a 4 m dish diameter with a field of view of 9°. The Cherenkov light produced in atmospheric showers is focused onto a 88 cm wide hexagonal photo-detection plane, composed of 1296 custom designed large area hexagonal silicon photomultipliers (SiPM) and a fully digital readout and trigger system. The SST-1M camera has been designed to provide high performance in a robust as well as compact and lightweight design. In this contribution, we review the different steps that led to the realization of the telescope prototype and its innovative camera.
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