Expected performance of the ASTRI-SST-2M telescope prototype

ASTRI (Astrofisica con Specchi a Tecnologia Replicante Italiana) is an Italian flagship project pursued by INAF (Istituto Nazionale di Astrofisica) strictly linked to the development of the Cherenkov Telescope Array, CTA. Primary goal of the ASTRI program is the design and production of an end-to-end prototype of a Small Size Telescope for the CTA sub-array devoted to the highest gamma-ray energy region. The prototype, named ASTRI SST-2M, will be tested on field in Italy during 2014. This telescope will be the first Cherenkov telescope adopting the double reflection layout in a Schwarzschild-Couder configuration with a tessellated primary mirror and a monolithic secondary mirror. The collected light will be focused on a compact and light-weight camera based on silicon photo-multipliers covering a 9.6 deg full field of view. Detailed Monte Carlo simulations have been performed to estimate the performance of the planned telescope. The results regarding its energy threshold, sensitivity and angular resolution are shown and discussed.Comment: In Proceedings of the 33rd International Cosmic Ray Conference (ICRC2013), Rio de Janeiro (Brazil). All CTA contributions at arXiv:1307.223

Characterization and performance of the ASIC (CITIROC) front-end of the ASTRI camera

The Cherenkov Imaging Telescope Integrated Read Out Chip, CITIROC, is a chip adopted as the front-end of the camera at the focal plane of the imaging Cherenkov ASTRI dual-mirror small size telescope (ASTRI SST-2M) prototype. This paper presents the results of the measurements performed to characterize CITIROC tailored for the ASTRI SST-2M focal plane requirements. In particular, we investigated the trigger linearity and efficiency, as a function of the pulse amplitude. Moreover, we tested its response by performing a set of measurements using a silicon photomultiplier (SiPM) in dark conditions and under light pulse illumination. The CITIROC output signal is found to vary linearly as a function of the input pulse amplitude. Our results show that it is suitable for the ASTRI SST-2M camera. <P /

Design concepts for the Cherenkov Telescope Array CTA: an advanced facility for ground-based high-energy gamma-ray astronomy

Ground-based gamma-ray astronomy has had a major breakthrough with the impressive results obtained using systems of imaging atmospheric Cherenkov telescopes. Ground-based gamma-ray astronomy has a huge potential in astrophysics, particle physics and cosmology. CTA is an international initiative to build the next generation instrument, with a factor of 5-10 improvement in sensitivity in the 100 GeV-10 TeV range and the extension to energies well below 100 GeV and above 100 TeV. CTA will consist of two arrays (one in the north, one in the south) for full sky coverage and will be operated as open observatory. The design of CTA is based on currently available technology. This document reports on the status and presents the major design concepts of CTA

AFS dynamic evolution during the emergence of an active region

Using data acquired during an observational campaign carried out at the THEMIS telescope in IPM mode, coordinated with other ground- and space-based instruments (IOACT, TRACE, EIT/SOHO, MDI/SOHO), we have analyzed the first evolutionary phases of a recurrent active region (NOAA 10050), in order to study the morphology and dynamics of its magnetic structures during their emergence and early development. The main result obtained from this analysis concerns the dynamic evolution of the arch filament system (AFS) crossing the polarity inversion line: the line of sight velocities determined from Doppler measurements confirm that the loops forming the AFS show an upward motion at their tops and a downward motion at their extremities, but also indicate that the upward motion decreases while the active region develops. Moreover, it has been found that, within the limits of the temporal cadence and spatial resolution of the instruments used, the first evidence of the active region formation is initially observed in the transition region and lower corona, and later on (i.e. after about 6 h) in the inner layers (chromosphere and photosphere). Another interesting result concerns the analysis of the magnetograms, indicating that the initial increase in the magnetic flux seems to be synchronous with the appearance od the active region appearance in the transition region and lower corona, and that the rate of increase of the magnetic flux during the formation of the active region is not constant, but is steeper at the beginning (i.e. during the first 150 h) than in the following period. All these results may indicate the presence of some mechanism that decelerates the magnetic flux emergence as more and more flux tubes rise towards higher atmospheric layers. Finally, we would like to stress the observed asymmetries between the preceding and the following sides of NOAA 10050: the p-side is more extented than the f-side, the p-side moves forward from the initial outbreak position much faster than the f-side recedes; the AFS f-side exhibits higher downflows than the p-side

Very fast photon counting photometers for astronomical applications: from QuantEYE to AquEYE

In the great majority of the cases, present astronomical observations are realized analyzing only first order spatial or temporal coherence properties of the collected photon stream. However, a lot of information is \u201chidden\u201d in the second and higher order coherence terms, as details about a possible stimulated emission mechanism or about photon scattering along the travel from the emitter to the telescope. The Extremely Large Telescopes of the future could provide the high photon flux needed to extract this information. To this aim we have recently studied a possible focal plane instrument, named QuantEYE, for the 100 m OverWhelmingly Large Telescope of the European Southern Observatory. This instrument is the fastest photon counting photometer ever conceived, with an array of 100 parallel channels operating simultaneously, to push the time tagging capabilities toward the pico-second region. To acquire some experience with this novel type of instrumentation, we are now in the process of realizing a small instrument prototype (AquEYE) for the Asiago 182 cm telescope, for then building a larger instrument for one of the existing 8-10 m class telescopes. We hope that the results we will obtain by these instruments will open a new frontier in the astronomical observations