The commissioning phase of the first Large-Sized Telescope (LST-1), the first out of four in construction for the northern site of the Cherenkov Telescope Array Observatory (CTAO), is almost completed. The LST-1 is a prime focus ground-based gamma-ray telescope with a 24 m diameter and 28 m focal length parabolic dish, inaugurated in October 2018 at Observatorio del Roque de los Muchachos (ORM), La Palma (Spain). The LST-1 is equipped with a camera Calibration System (CaliBox), placed at the center of the mirror dish, that uniformly illuminates the Camera at the telescope focal plane 28 m away. The intensity of the light beam and its time characteristics permits to calibrate the Camera response to shower events. Here we describe the CaliBox mechanical structure, the optical performance, the new internal-calibration hardware and software system including the definitive OPC-UA Server protocol logic used to manage the CaliBox and the internal sub-systems.
GAGG:Ce (Cerium-doped Gadolinium Aluminium Gallium Garnet) is a promising new scintillator crystal. A wide array of interesting features, such as high light output, fast decay times, almost non-existent intrinsic background and robustness, make GAGG:Ce an interesting candidate as a component of new space-based gamma-ray detectors. As a consequence of its novelty, literature on GAGG:Ce is still lacking on points crucial to its applicability in space missions. In particular, GAGG:Ce is characterized by unusually high and long-lasting delayed luminescence. This afterglow emission can be stimulated by the interactions between the scintillator and the particles of the near-Earth radiation environment. By contributing to the noise, it will impact the detector performance to some degree. In this manuscript we summarize the results of an irradiation campaign of GAGG:Ce crystals with protons, conducted in the framework of the HERMES-TP/SP (High Energy Rapid Modular Ensemble of Satellites - Technological and Scientific Pathfinder) mission. A GAGG:Ce sample was irradiated with 70 MeV protons, at doses equivalent to those expected in equatorial and sun-synchronous LowEarth orbits over orbital periods spanning 6 months to 10 years, time lapses representative of satellite lifetimes. We introduce a new model of GAGG:Ce afterglow emission able to fully capture our observations. Results are applied to the HERMES-TP/SP scenario, aiming at an upper-bound estimate of the detector performance degradation due to the afterglow emission expected from the interaction between the scintillator and the nearEarth radiation environment.
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