Radiation damage effect on time resolution of 6 series-connected SiPMs for MEG Ⅱ positron timing counter

摘要

We studied the impact of radiation damage on scintillation counters read out by six SiPMs connected in series focusing on their time resolution. Six SiPMs from AdvanSiD were irradiated step by step with a 37 MBq Sr-90 source. At the integrated dose expected at the end of the MEG II experiment, the time resolution at 30 degrees C was measured to be worse by similar to 29%. However, the deterioration is found to be reduced to similar to 6% at 10 degrees C since thermal dark noise is suppressed. We also tested the effect of connecting in series differently damaged SiPMs. We observed a position dependence of the time center in a counter, which worsened the time resolution.