A Simple Amorphous-Silicon Photodetector for Two-Dimensional Position Sensing

A simple two-dimensional position-sensitive detector is proposed and initial tests are reported. The device, aimed to be high-energy-radiation resistant and reliable under magnetic fields, is based on a set of small p-i-n amorphous silicon photodiodes acting as pixels sandwiched between two perpendicular strip electrode structures. No thin-film transistors are used. A simplified prototype has been made and tested. The results show that the position of a laser spot on its surface can be deduced from the signals it generates. Further work proposed, includes tests on possible cross talk and behavior under radiation and magnetic fields, as well as the development of methods for accurate position calculation and for appropriate response calibration.