Signal fluctuation in neutron-irradiated silicon Avalanche Photodiodes

Light from PbWO4 crystals in the barrel part of the CMS electromagnetic calorimeter will be detected by Avalanche Photodiodes (APDs). The crystal-APD system has to operate reliably in a high radiation environment. In the present paper, APD signal variation with wavelength and gain fluctuations for PbWO4 scintillation light was investigated as a function of the neutron fluence. Calculations were made with a single-particle Monte Carlo simulation technique. The results show that the neutron fluence has an influence on the APD signal during 10 years CMS operation.