The detection of minimum ionizing particles with multi-pixel hybrid photodiodes

Recent measurements of the performance of the newly available multi-pixel hybrid photo-detector (M-HPD) have demonstrated their particular value in the detection of very low light-level signals. The single and multiple photo-electron response characteristics of these devices is unmatched by any other room-temperature device. This characteristic, coupled with their speed of response and the availability of an internally-generated trigger signal when any one of the pixels detects an event, makes them well suited for the detection of minimum ionizing particles (MIPs). These detectors may therefore be expected to find application in particle-tracking applications both in High-Energy Physics and Gamma-ray Astronomy. The result of tests made using single and double-clad plastic fibres have confirmed the usefulness of these devices. The technique used to read-out 61 channels of data is described along with a way of viewing as many as 2000 fibres with just two 61-pixel M-HPDs.