Abstract
Abstract
ASTRI-Horn is the prototype of the nine telescopes that form
the ASTRI Mini-Array, under construction at the Teide Observatory in
Tenerife (Spain), devoted to observe the sky in the 1–200 TeV
energy band. It adopts an innovative optical design based on a
dual-mirror Schwarzschild-Couder configuration, and the camera,
composed by a matrix of monolithic multipixel silicon
photomultipliers (SiPMs) is managed by ad-hoc tailored front-end
electronics based on a peak-detector operation mode.
During the Crab Nebula campaign in 2018–2019, ASTRI-Horn was
affected by gain variations induced by high levels of night sky
background. This paper reports the work performed to detect and
quantify the effects of these gain variations in shower images. The
analysis requested the use of simultaneous observations of the night
sky background flux in the wavelength band 300–650 nm performed
with the auxiliary instrument UVscope, a calibrated multi-anode
photomultiplier working in single counting mode. As results, a
maximum gain reduction of 15% was observed, in agreement with the
value previously computed from the variance of the night sky
background level in each image. This ASTRI-Horn gain reduction was
caused by current limitation of the voltage supply.
The analysis presented in this paper provides a method to evaluate
possible variations in the nominal response of SiPMs when scientific
observations are performed in the presence of high night sky
background as in moon conditions.