Subnanosecond timing with large area avalanche photodiodes and LSO scintillator

The detection properties of 10 mm and 16 mm diameter bevelled-edge avalanche photodiodes fitted with LSO crystal were measured using /spl gamma/-sources. Among the properties measured were the electron-hole pair yield, time resolution and energy resolution. These detectors provide excellent time resolution of 565 ps for /sup 60/Co /spl gamma/-rays with the energy threshold set at 1 MeV. The energy resolution of the 662 keV /spl gamma/-peak from a /sup 137/Cs source was measured to be 11% FWHM with a shaping time constant of 0.1 /spl mu/s. A comparative discussion of the observed time resolution of these large area APDs emphasizes that APD gain, its quantum efficiency, and capacitance are important in timing applications.