Evaluation of LAAPD arrays for high-resolution scintillator matrices readout

In this paper, we evaluate the performance of recently released avalanche photodiode arrays from Advanced Photonix, Inc., for scintillator matrices readout. The large-area avalanche photodiode (LAAPD) quadrant device is a monolithic 2 /spl times/ 2 pixel structure with an active area of 5.3 mm/sup 2/ per pixel. The device allows stable operation with high gains up to 200 and detection efficiency of 73/spl sim//spl plusmn/ 10% for 420-nm photons. It is furthermore characterized by a pixel linear fill factor of 90% and low noise equal to 16 electrons equivalent noise charge measured at room temperature. We have measured pixel-to-pixel gain nonuniformity smaller than 1.5% and interpixel crosstalk of 1.7% in pulse-mode operation with a device gain of 50. An energy resolution of 12.3 /spl plusmn/ 0.5% was achieved for the 511-keV photopeak from a /sup 22/Na source placed on top of a 2 /spl times/ 2 /spl times/ 10 mm/sup 3/ LSO crystal coupled to one pixel of a quadrant LAAPD. An array of LSO crystals was later coupled to the device allowing individual crystal identification. A coincidence timing resolution of 1.9 /spl plusmn/ 0.1 ns full-width at half-maximum has been obtained for quadrant pixel with LSO scintillator for the 511-keV peak from a /sup 22/Na source. Finally, we compared the characteristics and readout performance of the LAAPD array with published results of some commercially available avalanche photodiode arrays.