INAF, the Italian National Institute of Astrophysics, takes another step forward for the realization of the mini-array of 9 ASTRI telescopes, assigning to the Italian section of the Hamamatsu Photonics Company the realization of over 25 thousand SiPM silicon sensors (Silicon Photo-Multiplier) in response to a competitive tender for a final amount of € 1.03 millions. The SiPM sensors will cover the wide field of view Cherenkov cameras based on innovative technology "made in INAF", which will be mounted on the focal planes of the ASTRI telescopes, designed to observe the universe in gamma rays.

The cutting-edge technologies of the ASTRI mini-array refer to those developed and already used for the first ASTRI-Horn prototype telescope, which is installed since a few years at the astronomical INAF site on the slopes of the Etna Mount in Sicily. In particular, the ASTRI telescopes adopt for the first time a wide-field, two-mirror Schwarzschild-Couder-type optical configuration, whose functionality was recently proven with the observation of the Crab nebula in gamma rays with the ASTRI-Horn telescope. INAF considers very important the development of the ASTRI mini-array, both to produce state-of-the-art data and to gain experience in view of the subsequent implementation of the international Cherenkov Telescope Array Observatory (CTAO) project which involves the use of a number of very large telescopes (118) distributed in two places in the northern and southern hemisphere of the Earth.

The Cherenkov Chamber

The Cherenkov chamber developed by INAF for the focal plane of each telescope, thanks to its two-mirror configuration, is very compact (just 60 cm in diameter) and is based on innovative electronics and electro-mechanical systems. Each chamber, whose detection plane is curved due to technical requirements, will mount approximately 2400 SiPM-type square silicon sensors, with sides of about 7 mm. A total of eleven rooms will be built for the ASTRI / Mini-array project, one for engineering and qualification activities and one for reserve. The SiPM sensors represent the latest generation of light detection systems. The high photo-detection efficiency and a large collection area make them very efficient for the detection of gamma photons emitted by celestial sources.

Following the awarding of the tender to Hamamatsu, INAF president Nichi D’Amico says: “A very important day, a remarkable scientific milestone. After the realization of the ASTRI prototype in Sicily we are now starting the construction of the mini-array of the ASTRI telescopes to the mini-array, one of the most important precursors of CTA. The devices we asked to build in Hamamatsu are technologically advanced, and this is important because we inject innovation aspects into the industrial system: they are sensors that could have applications in many fields tomorrow, and so we are also proud about that ”.

Also Koei Yamamoto, Senior Managing Director of Hamamatsu Photonics KK (Japan) wanted to comment on the news: "We are happy to participate in the ASTRI project by providing large-scale, low-noise solid-state Si-based sensors. We afford this technology challenge thanks to the  research and development efforts that began a few years ago".

Information on the ASTRI project and the Cherenkov technique

ASTRI-Horn prototype telescope, which is installed since a few years at the astronomical INAF site on the slopes of the Etna Mount in Sicily.

The ASTRI project (Astrophysics with Mirrors with Italian replicating technology) is coordinated by INAF, with the support of the Italian Ministry of Education, University and Research (MIUR) and in collaboration with various national and international partners (Universities of Padova and Perugia, INFN, Universidade de São Paulo and FAPEST - Brazil, North-West University South Africa). The goal is the design, implementation and astronomical use for the Italian and international scientific community of a group of 9 telescopes for high-energy gamma-ray observations from Earth with the Cherenkov technique, in the spectral region in gamma rays up to 300 TeV – an almost unexplored energy band even for the most modern particle accelerators. The observations of ASTRI will allow us to study phenomena of fundamental importance to understand our Universe, such as the origin and acceleration in the remains of Supernova of cosmic rays and physics in relativistic regime related to the emission of gamma photons in Galactic Nuclei active.

The ASTRI mini-array utilizes the Cherenkov technique for observing gamma rays. This approach is based on the detection of the so-called Cherenkov light that is generated in the interaction of gamma rays with the atmosphere. High energy gamma rays coming into contact with the earth's atmosphere produce cascades of subatomic particles; these very energetic particles can travel in the air even faster than the speed of light, giving rise to a faint (and very short, of the order of a billionth of a second) flash of bluish light which, once collected by telescopes, can be traced back to the primary emission in gamma rays.

For further information:

INAF PR Office: tel. +39 06.355.33390 cell. +39 335 1778428 marco.galliani@inaf.it

Giovanni Pareschi, PI of the ASTRI Project : cell 3316113735, giovanni.pareschi@inaf.it