Optical Characterization of Aerogel and Anti-Reflection Coating of Silicon Photomultipliers for Ring Imaging Cherenkov Detector

In the context of the ALICE upgrade system for Run 5, a Ring Imaging Cherenkov (RICH) detector has been proposed to perform charged Particle Identification (PID) in the momentum range 0.5-15 GeV/c. It consists of an Aerogel radiator and a Silicon Photomultipliers (SiPM) array with sensitivity to single photons in the visible range. The performance of particle identification strongly depends on the amount of Cherenkov photons detected by the RICH Detector and is affected by the optical properties of both Aerogel and SiPM. In this paper, the optical characterization of 15 aerogel tiles of 10x10 cm2 has been performed in the wide spectrum from 250 to 800 nm using an Integrated Sphere (IS) setup. In addition, the reflectivity of Silicon has also been studied, various samples have been prepared using different films in combination with a so-called textured etching, and the reflection properties have been measured using the same setup to identify the optical properties in Anti-Reflection Coating (ARC) of SiPM.