A novel, distortion-free position sensitive APD for nuclear imaging

We have investigated a new position sensitive avalanche photodiode (PSAPD) for indirect and direct radiation imaging. This PSAPD exhibits minimal image distortion and still has all the attractive characteristics of our normal high gain APDs. The arc-PSAPD incorporates a resistive arc between the corner contacts which eliminates the ´pincushion´ or ´barrel´ effect commonly seen with four corner contact devices. Simulations have been performed to model the position distortion of such a device. Position and energy resolution have also been measured with these devices. Gamma ray imaging with various scintillator arrays and direct charged particle and low energy X energy resolution-ray images have been acquired.