Performance Evaluation of the HAPD in the Belle II Aerogel RICH Counter
Résumé
The Hybrid Avalanche Photo Detector (HAPD) is used as a photon detector for Aerogel Ring Imaging Cherenkov counter (ARICH), a particle identification device at Belle II. ARICH measures Cherenkov angles of photons emitted in silica aerogel radiators, hence a high photon detection efficiency is required by the HAPD module, a combination of HAPD and front-end electronics board. We evaluate the performance of the HAPD modules by measuring the noise level, the offset value, the pulse height, temperature dependency and the variation of performance in the beam commissioning period. This article describes the results of performance evaluation of the HAPD and shows that it fulfills the requirements of ARICH.