Abstract
The Cherenkov Telescope Array (CTA) is the next ground-based $\gamma$-ray observatory in the TeV $\gamma$-ray spectral region operating with the Imaging Atmospheric Cherenkov Technique. It is based on almost 70 telescopes of different class diameters - LST, MST and SST of 23, 12, and 4 m, respectively - to be installed in two sites in the two hemispheres (at La Palma, Canary Islands, and near Paranal, Chile). Several thousands of reflecting mirror tiles larger than 1 m$^2$ will be produced for realizing the segmented primary mirrors of a so large number of telescopes. Almost in parallel, the ASTRI Mini-Array (MA) is being implemented in Tenerife (Canary Islands), composed of nine 4 m diameter dual-mirror Cherenkov telescopes (very similar to the SSTs). We completed the mirror production for all nine telescopes of the ASTRI MA and two MST telescopes (400 segments in total) using the cold glass slumping replication technology. The results related to the quality achieved with a so large-scale production are presented, also discussing the adopted testing methods and approaches. They will be very useful for the adoption and optimization of the quality assurance process for the huge production (almost 3000 m$^2$ of reflecting surface) of the MST and SST CTA telescopes.
Highlights
Imaging Atmospheric Cherenkov Telescopes (IACTs) are ground-based telescopes designed to observe γ-ray celestial sources at very-high energies (VHE) in the TeV energy range.[1]
While there is no systematic difference between the results obtained at Osservatorio Astronomico di Brera (OAB) and DESY, for most segments the radius of curvature (RoC) measured by Media Lario (ML) is larger than that obtained with the other facilities
The measurements performed at OAB and DESY use a LED as light source and a CCD camera as image detector: in this way, a photometric image is obtained, which is characterized by high homogeneity and uniformity
Summary
Imaging Atmospheric Cherenkov Telescopes (IACTs) are ground-based telescopes designed to observe γ-ray celestial sources at very-high energies (VHE) in the TeV energy range.[1]. It should be noted that the performance of CTAO would be improved, after the implementation of this alpha configuration, with the installation of additional telescopes, in particular for the southern site, where there is a large area that could be populated with additional telescopes In this respect, it should be noted that another kind of medium size telescopes, based on the dual-mirror Schwarzschild-Couder aplanatic telescopes (9-m in diameter) and named prototype Schwarzschild-Couder Telescope (pSCT), would be possibly implemented, similar to the prototype already developed and operated in Arizona (USA).[20,21]. The results of the present work will be very useful for the adoption and optimization of the quality assurance process for the huge production of the MST north and SST CTA telescopes, for which thousands of reflecting segments have to be manufactured and qualified
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