Performance of large-area avalanche photodiode for low-energy X-rays and y-rays scintillation detection

摘要

We report on the performance of large-area (5 x 5 mm~2) avalanche photodiodes (APD) produced by Hamamatsu Photonics, as a low-energy X-rays and γ-rays scintillation detector. Hamamatsu APD has a reverse structure and works at relatively low bias voltage of 300-350 V. The leakage current is 1.2 nA at room temperature (25℃) and decreases to 10 pA at -20℃ for an avalanche gain of 50. The best FWHM energy resolutions of 9.4 +- 0.3% and 7.4 +- 0.3% were obtained for 59.5 keV y-rays from ~(241)Am and 122 keV γ-rays from ~(57)Co sources, respectively, as measured with a 5 x 5 x 5 mm~3 cubic CsI(Tl) crystal. We show that the minimum detectable energy for the scintillation light is remarkably low; 4.6 keV at room temperature (20℃) and 1.1 keV at -20℃. 5.9 keV X-rays from ~(55)Fe were clearly resolved at -20℃ with an FWHM resolution of 32.9 +- 0.3%. These results suggest that Hamamatsu APD can be a promising device for future applications in low-energy scintillation detection.