Mirror production for the Cherenkov telescopes of the ASTRI Mini-Array and of the MST project for the Cherenkov Telescope Array

TL;DR

This paper reports on the large-scale production and quality assurance of segmented mirrors for Cherenkov telescopes in the CTA, focusing on the ASTRI Mini-Array and MST project, using cold glass slumping technology.

Contribution

It presents the successful large-scale manufacturing process and quality testing methods for segmented mirrors for CTA telescopes, demonstrating readiness for mass production.

Findings

High-quality mirror segments produced at scale

Effective testing methods for mirror quality assurance

Production process suitable for thousands of mirror tiles

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.