Avalanche photodiodes for electromagnetic calorimeters

Hamamatsu S8148 silicon avalanche photodiode (APD) working in proportional mode has been chosen as readout device for the PbWO4 crystals in the barrel of the CMS electromagnetic calorimeter (ECAL). High hadron fluences strongly affect the main parameters of both the scintillation crystals and the silicon detectors. In this work, we offer a new zinc sulfide–silicon (ZnS–Si) isotype heterojunction APD structure that is able to operate in high-radiation levels. A Monte Carlo simulation code has been performed in order to compare the Hamamatsu S8148 and the ZnS–Si APD structures for the photons emitting from PbWO4 crystal during 10 years of CMS operation. Based on this work, the performance of these two APD structures has been investigated.