Swiss In-Kind Contributions to CTAO
LST system engineering
In 2019, the LST project underwent a Critical Design Review (CDR) to assess if the design implemented in the first prototype LST-1 had no major pitfalls and could be eligible for acceptance by CTAO. LST management approached the DPNC group to help in the process and provide some know-how in system engineering (SE). Prof D. Della Volpe serves as the lead system engineer for the LSTs and took over the CDR process to bring it to completion. Dr M. Heller and later M.sc. Eng. M. Stodulska, from the same group, acted as a deputy system engineer. The UNIGE SE team brought the CDR to success, communicates all LST technical aspects with CTAO and follows up on the operation and commissioning activities. The SE team has an active role in the definition of the system requirements for the European tender happening in 2023 for LST2-4 and will coordinate the activities for the construction of the southern LST array in 2025-28.
[MireiaNievasRosillo]
The advanced SiPM camera
The Swiss experience acquired during the development of the FACT and SST-1M telescopes is utilised at its maximum for the development of the future camera for the LST. The University of Geneva, represented by M. Heller, is coordinating this activity within the LST collaboration. This activity is very relevant for future opportunities for Switzerland to participate in the hardware implementation of the telescopes, as indicated by the declaration of interest signed in June 2021 by the UNIGE Rector, Prof. Y. Flückiger and the Director of ICCR of Tokyo University, Nobel Laureate T. Kajita and the LST spokesperson Prof. M. Teshima.
The main driver of this initiative is to use SiPMs for the LSTs, as they offer twice more sensitivity to Cherenkov light when compared to classical photomultiplier tubes. Their sensitive dimension (limited to 1 cm2 as they are noisy devices and also integrate more background light) is smaller than that of photomultipliers. This implies a potentially improved camera resolution and capability to capture smaller details in the showers. These can be fully exploited by modern analysis techniques. This imposes strict requirements on the camera design as four times more pixels are needed to cover the same field of view. Such an increased number of pixels has a dramatic impact on the camera power consumption, a challenge being tackled with innovative low-power application-specific integrated circuits (ASICs) developed in by the DPNC, the AQUA Lab/EPFL and ETHZ in a FLARE project.
The ASICs will be general purpose for SiPM signal amplification and digitisation at GHz-speed developed in cooperation with Swiss microelectronics companies. Additionally, the DPNC is collaborating with UZH on the development of new triggering techniques based on real-time artificial intelligence inference running on hardware accelerators. Prof. Serra at UZH has acquired strong know-how in developing deep-learning algorithms that can run on eld-programmable gate arrays (FPGAs) in the frame of the LHCb detector of the Large Hadron Collider at CERN. The principle is that thanks to artificial intelligence algorithms, the decision whether an image acquired by a camera is registered or not is not only based on whether the intensity in any region of the camera is higher than a given threshold but it can be also based on more complex information, such as how much the image resembles an extensive air shower.
The challenge will be to develop algorithms which are robust enough to deliver a stable outcome at different levels of background light and to do so with the minimum possible processing power. The overall aim will be to lower the detection threshold of the LSTs and target energy thresholds as low as 10 GeV. All these state-of-the-art developments involve Swiss industries as described below.