Evaluation of the avalanche photo diode (APD) as scintillation sensor

Four APD samples with different sensitive areas were tested to examine the possibility of reading large-area CsI(TI) scintillators. A comparison of the energy resolution or the S/N was made for the APDs at the room temperature. It was found that the APD gain increases significantly with decreasing temperature especially below 0°C. Within the temperature range concerned, a plot of 1/gain fitted well to a linear function of the temperature. A possible mechanism of the observed temperature dependence is proposed in terms of a phonon—electron interaction.