The imperial college system for photon event counting

A simple compact photoelectron event counter for the photometry of extended objects has been developed and tested. The primary detector consists of a high-gain microchannel plate image intensifier optically coupled to a CCD camera; the intensifier gain is sufficiently high to produce individual photoelectron scintillations on the output phosphor screen. Each event location detected by the CCD camera is converted into an encoded address and incremented into a 48K x 16-bit memory. An event centroiding procedure is used to find the center of each scintillation, and the event center only is stored in the memory. A schematic diagram of the system is presented.