Developments of a new mirror technology for the Cherenkov Telescope Array

TL;DR

This paper introduces a novel, open-structure mirror technology for the Cherenkov Telescope Array, emphasizing improved durability, ventilation, and ease of manufacturing for high-energy gamma-ray telescopes.

Contribution

The paper presents a new mirror production method using cold-slumping and laminated glass panels, enhancing durability and ventilation for CTA telescopes.

Findings

Prototype mirrors meet optical and durability standards.

Open-structure design prevents water trapping and improves ventilation.

Comparison shows advantages over previous rigid support technology.

Abstract

The Cherenkov Telescope Array (CTA) observatory for very high-energy gamma rays will consist of about a hundred of imaging atmospheric Cherenkov telescopes (IACTs) of different size with a total reflective area of about 10,000 m$^2$. Here we present a novel technology for the production of IACT mirrors that has been developed in the Institute of Nuclear Physics PAS in Krakow, Poland. The mirrors are made by cold-slumping of the front reflecting aluminium-coated panel and the rear panel interspaced with aluminium spacers. Each panel is built of two glass panels laminated with a layer of a fibreglass tissue in between for reinforcement of the structure against mechanical damage. The mirror structure is open and does not require a perfect sealing needed in closed-type designs. It prohibits water to be trapped inside and enables a proper ventilation of the mirror. Full-size hexagonal prototype mirrors produced for the medium-sized CTA telescopes will be presented together with the results of recent comprehensive optical and durability tests. Their design will be compared to the earlier technology developed at INP PAS that used a rigid flat open support structure with a reflective layer made by cold-slumping of the coated glass panel to the cast-in-mould spherical epoxy resin layer.