A hybrid position sensitive avalanche photodiode detector for scintillation spectroscopy and imaging

We investigate a prototype hybrid position sensitive avalanche photodiode (HPSAPD) that combines conventional photomultiplier tube (PMT) and solid-state photodiode technology to form a rugged, compact, high gain (/spl sim/ 10/sup 6/ 10/sup 7/), high signal-to-noise ratio (S/N) photodetector. This detector uses a photocathode to convert incident light into photoelectrons that are accelerated to a position sensitive avalanche photodiode (PSAPD). Through impact ionization initiated by the incident accelerated photoelectrons, the PSAPD provides additional gain. The PSAPD provides an output signal used for energy and timing resolution information and 4 additional output signals for position information. Here we characterize and show the initial spectroscopic and imaging capabilities of a prototype HPSAPD that uses a GaAs photocathode and a planar PSAPD of 14 /spl times/ 14 mm/sup 2/ area.