Characteristics study on the APD-based front-end readout for CsI(Tl) detector

Abstract Background: The avalanche photodiode (APD) has the advantages of small size, high detection efficiency, internal gain and insensitivity to magnet fields. But the internal gain and the signal-noise ratio (SNR) of the output signal of pulse are affected by bias voltage and temperature. Purpose: This study aims to test the effect of bias voltage and temperature on the APD-based front-end readout of scintillation detector. Methods: The avalanche photodiode is employed as the photodetector for CsI(Tl) scintillation, and equiped a charge sensitive preamplifier of low noise to form a probe. The energy resolution of scintillation detector with this probe was tested on a ¹³⁷Cs radiation source under different bias voltage and temperature. Results: The experimental results show that the energy resolution of the detection system is affected by both the bias voltage and the temperature. When the bias voltage at both ends of the APD is 370 V, the energy resolution is 4.98% for the gamma ray with the energy of 662 keV at the room temperature. Conclusion: The energy resolution will increase with the decrease of temperature within the range of -20℃ to 40℃. (authors)