Procedures for the relative calibration of the SiPM gain on ASTRI SST-2M camera

TL;DR

This paper details calibration procedures for SiPM gain in the ASTRI SST-2M telescope camera, ensuring uniform trigger performance across the focal plane by compensating for temperature and voltage variations.

Contribution

It introduces specific calibration procedures and experimental measurements for SiPM gain adjustment in the ASTRI SST-2M camera.

Findings

Gain dependence on voltage and temperature measured.

Calibration procedures for uniform trigger achieved.

Temperature compensation effectively stabilizes SiPM gain.

Abstract

ASTRI SST-2M is one of the prototypes of the small size class of telescopes proposed for the Cherenkov Telescope Array. Its optical design is based on a dual-mirror Schwarzschild-Couder configuration, and the camera is composed by a matrix of monolithic multipixel silicon photomultipliers managed by ad-hoc tailored front-end electronics. This paper describes the procedures for the gain calibration on the ASTRI SST-2M. Since the SiPM gain depends on the operative voltage and the temperature, we adjust the operative voltages for all sensors to have equal gains at a reference temperature. We then correct gain variations caused by temperature changes by adjusting the operating voltage of each sensor. For that purpose the SiPM gain dependence on operating voltage and on temperature have been measured. In addition, we present the calibration procedures and the results of the experimental measurements to evaluate, for each pixel, the parameters necessary to make the trigger uniform over the whole focal plane.