Development of the next generation of large SiPM camera for Large Size Telescopes

Scientists in Switzerland introduced in the gamma-ray astronomy field a relevant innovation: a new photosensor and, hence, a new concept of imaging camera, which was pioneered by FACT at ETHZ for the first time.

This silicon-based technology revolutionised the field introducing a robust sensor against light and new associated electronics.

Traditionally, photomultiplier tubes (PMTs) are employed, with the advantage of fast rising signals, low thermal noise and larger sizes.

On the other hand, silicon-photomultipliers (SiPMs) are considerably more robust against light, enabling observations with high moon without any risk to damage sensors. Relevant are also their slow ageing, single-photon counting capabilities, and the fact that they are mass producible.

The SST-1M project of the Cherenkov Telescope Array (CTA), developed at UNIGE, brought the FACT initial development further, adopting a fully digital readout, new optical elements associated with large-area sensors, and easier manufactures of components.

The long-standing operation of FACT and the achievement of all specifications imposed by the CTA Observatory (CTAO) by the SST-1M, contributed to prove the technlogy ready for the CTA SSTs.They will be implemented with a dual-mirror optical design equipped with a SiPM-based camera.In 2019 the UNIGE joined the Large Size Telescope (LST) project, a sub-project of CTAO, which is regulated by its own independent MoU.It foresees financial and task commitments for the provision to CTAO of 4 telescopes with diameter of 24 m by 2025 to be installed at the Observatory Roque de Los Muchachos, La Palma, Canarian Islands Spain.

As of today, the Département de Physique Nucléaire et Corpusculaire (DPNC) of UNIGE coordinates two working packages (WPs) of LST: the System Engineering is coordinated by Dr D. della Volpe and the R&D on SiPM cameras by Dr. M. Heller.

A team from Institutions in the LST sub-consortium, including also DPNC, ETHZ, and EPFL, is defining steps toward the advanced SiPM-based camera for LSTs.The EPFL group, led by Prof.

Charbon, adds up a strong innovation expertise on single-photon avalanche diodes (SPADs) to the expertise in the field of ETHZ and DPNC.

The common view of participants is that the development of future cameras in gamma-ray astronomy needs substantially new developments on: 1) the analog front-end electronics for large area SiPM sensors, which needs to amplify and reshape the signal with low noise and power consumption