A. Marszałek

Performance Verification of the FlashCam Prototype Camera for the Cherenkov Telescope Array

Abstract The Cherenkov Telescope Array (CTA) is a future gamma-ray observatory that is planned to significantly improve upon the sensitivity and precision of the current generation of Cherenkov telescopes. The observatory will consist of several dozens of telescopes with different sizes and equipped with different types of cameras. Of these, the FlashCam camera system is the first to implement a fully digital signal processing chain which allows for a traceable, configurable trigger scheme and flexible signal reconstruction. As of autumn 2016, a prototype FlashCam camera for the medium-sized telescopes of CTA nears completion. First results of the ongoing system tests demonstrate that the signal chain and the readout system surpass CTA requirements. The stability of the system is shown using long-term temperature cycling.

Development of an optical system for the SST-1M telescope of the Cherenkov Telescope Array observatory

The prototype of a Davies-Cotton small size telescope (SST-1M) has been designed and developed by a consortium of Polish and Swiss institutions and proposed for the Cherenkov Telescope Array (CTA) observatory. The main purpose of the optical system is to focus the Cherenkov light emitted by extensive air showers in the atmosphere onto the focal plane detectors. The main component of the system is a dish consisting of 18 hexagonal mirrors with a total effective collection area of 6.47 m 2 (including the shadowing and estimated mirror reflectivity). Such a solution was chosen taking into account the analysis of the Cherenkov light propagation and based on optical simulations. The proper curvature and stability of the dish is ensured by the mirror alignment system and the isostatic interface to the telescope structure. Here we present the design of the optical subsystem together with the performance measurements of its components.

The single mirror small size telescope (SST-1M) of the Cherenkov Telescope Array

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.

FlashCam: a novel Cherenkov telescope camera with continuous signal digitization

The Cherenkov Telescope Array (CTA) will be the next generation ground-based observatory for cosmic gamma rays. The FlashCam camera for its mid-size telescope introduces a new concept, with a modest sampling rate of 250 MS/s, that enables a continuous digitization as well as event buffering and trigger processing using the same front-end FPGAs. The high performance Ethernet-based readout provides a dead-time free operation for event rates up to 30 kHz corresponding to a data rate of 2.0 GByte/s sent to the camera server. We present the camera design and the current status of the project.

Performance of the small size telescope sub-array of the Cherenkov Telescope Array observatory

The southern part of the Cherenkov Telescope Array (CTA) observatory will consist of at least three types of telescopes: large size, medium size and small size telescopes. Massive Monte Carlo simulations have been performed using the European Grid Infrastructure to analyze the performance of this array. We present the results of these simulations for a sub-array of small size telescopes of the Davies-Cotton type. Such a telescope, called SST-1M, is currently being proposed for the CTA observatory by a group of Polish and Swiss institutions. SST-1M will have a mirror of 4m diameter and it will be equipped with a fully digital camera based on silicon photodetectors. We present the analysis of the sub-array sensitivity, angular resolution, and energy resolution to demonstrate the fulfillment of the requirements of the CTA Consortium. To verify the results obtained in numerical simulations a construction of a mini array of five SST-1M telescopes is planned. We also present the performance of such a mini array and discuss the prospects of its scientific program.

DigiCam: fully digital compact camera for SST-1M telescope

The single mirror Small Size Telescopes (SST-1M), being built by a sub-consortium of Polish and Swiss Institutions of the CTA Consortium, will be equipped with a fully digital camera with a compact photodetector plane based on silicon photomultipliers. The internal trigger signal transmission overhead will be kept at low level by introducing a high level of integration. It will be achieved by massively deploying state-of-the-art multi-gigabit transceivers, beginning from the ADC flash converters, through the internal data and trigger signals transmission over backplanes and cables, to the camera’s server 10Gb/s Ethernet links. Such approach will allow fitting the size and weight of the camera exactly to the SST-1M needs, still retaining the flexibility of a fully digital design. Such solution has low power consumption, high reliability and long lifetime. The concept of the camera will be described, along with some construction details and performance results.

The single mirror small sized telescope for the Cherenkov telescope array

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). About 70 SST telescopes will be part the CTA southern array which will also include Medium Sized Telescopes (MST) in its threshold configuration. Optimized for the detection of gamma rays in the energy range from 5 TeV to 300 TeV, the SST-1M uses a Davies-Cotton optics with a 4 m dish diameter with a field of view of 9 degrees. The Cherenkov light resulting from the interaction of the gamma-rays in the atmosphere is focused onto a 88 cm side-to-side hexagonal photo-detection plane. The latter is composed of 1296 hollow light guides coupled to large area hexagonal silicon photomultipliers (SiPM). The SiPM readout is fully digital readout as for the trigger system. The compact and lightweight design of the SST-1M camera offers very high performance ideal for gamma-ray observation requirement. In this contribution, the concept, design, performance and status of the first telescope prototype are presented.

Performance of the SST-1M telescope of the Cherenkov Telescope Array observatory

R. Moderskic,W. Bilnikk, J. Blockig, L. Bogacze, T. Bulikd , F. Cadouxa, A. Christova, M. Chruślinskad , M. Curylog, D. della Volpea, M. Dyrdag, Y. Favrea, A. Frankowskic, Ł. Grudnikg, M. Grudzinskad , M. Hellera, B. Idźkowskib, M. Jamrozyb, M. Janiakc, J. Kasperekk, K. Lalikk, E. Lyard f , E. Machg, D. Mandatm, A. Marszalekh,b, J. Michalowskig, T. Montarulia, A. Neronov f , J. Niemiecg, M. Ostrowskib, P. Paśkoh, M. Pechm, A. Porcelli∗a, E. Prandini f , E. Puescheln, P. Rajdak, M. Rameeza, P. Rozwadowskid , E. jr Schioppaa, P. Schovanekm, K. Sewerynh, K. Skowrong, V. Sliusari, M. Sowinskig, Ł. Stawarzb, M. Stodulskab, M. Stodulskig, S. Toscano f ,l, I. Troyano Pujadasa, R. Walter f , M. Wiȩcekk, A. Zagdanskib, K. Ziȩtarab, P. Żychowskig for the CTA Consortium† aDPNC – Universite de Geneve, Geneve, Switzerland bAstronomical Observatory, Jagiellonian University, Krakow, Poland cNicolaus Copernicus Astronomical Centre, Polish Academy of Sciences, Warsaw, Poland dAstronomical Observatory, University of Warsaw, Warsaw,Poland eDepartment of Information Technologies, Jagiellonian University, Krakow, Poland f ISDC, Observatoire de Geneve, Universite de Geneve, Versoix, Switzerland gInstytut Fizyki Jadrowej im. H. Niewodniczanskiego Polskiej Akademii Nauk, Krakow, Poland hCentrum Badan Kosmicznych Polskiej Akademii Nauk, Warsaw, Poland iAstronomical Observatory, Taras Shevchenko National University of Kyiv, Kyiv, Ukraine kAGH University of Science and Technology, Krakow, Poland lVrije Universiteit Brussels, Brussels, Belgium mInstitute of Physics of the Czech Academy of Sciences, Prague, Czech Republic nUniversity College Dublin, Ireland

Front-end and slow control electronics for large area SiPMs used for the single mirror Small Size Telescope (SST-1M) of the Cherenkov Telescope Array (CTA)

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.

An innovative SiPM-based camera for gamma-ray astronomy with the small size telescopes of the Cherenkov Telescope Array

A prototype camera for one of the Cherenkov Telescope Array (CTA) projects for the small size telescopes, the single mirror Small Size Telescope (SST-1M), has been designed and is under construction. The camera is a hexagonal matrix of 1296 large area (95 mm2) hexagonal silicon photomultipliers. The sensors are grouped into 108 modules of 12 pixels each, hosting a preamplifier board and a slow-control board. Among its various functions, this latter implements a compensation logic that adjusts the bias voltage of each sensor as a function of temperature. The fully digital readout and trigger system, DigiCam, is based on the latest generation of FPGAs, featuring a high number of high speed I/O interfaces, allowing high data transfer rates in an extremely compact design.