Study of large area Hamamatsu avalanche photodiode in a -ray scintillation detector

We have carried out study of a large area ( 10 × 10 mm 2 ) , reverse-type avalanche photodiode (APD) recently developed by Hamamatsu photonics. It has low dark current of 3 nA at room temperature, and the gain stability was almost the same as prototypical APDs reported in our previous paper. We studied the performance as a γ -ray detector with four scintillators, CsI(Tl), BGO, GSO(Ce), and YAP(Ce) crystals. For example we obtained the best energy resolution of 4.9 ± 0.2 % (FWHM) for 662 keV γ -rays, as measured with a 10 × 10 × 10 mm 3 CsI(Tl) crystal. The minimum detectable energy was as low as 10 keV at 20 ∘ C and 3.1 keV at - 20 ∘ C . Thanks to its large effective area, this APD can effectively read out photons from larger size scintillators. When coupling to a 300 × 48 mm 2 BGO plate of 3 mm thickness, an FWHM energy resolution of 20.9 ± 0.2 % was obtained for 662 keV γ -rays, with the minimum detectable energy of about 60 keV at - 15 ∘ C . These results suggest that our prototype APD can be a promising device for various applications replacing traditional PMTs such as use in space for Japanʹs future X-ray astronomy mission NeXT.