photomultiplier tube

Fig 1. Schematic diagram of the main elements of a photomultiplier tube.

A photomultiplier is an electronic device that converts a light signal or light beam into an equivalent amplified electrical signal. Electrons are emitted from an illuminated cathode by the photoelectric effect, and then strike a series of focusing electrodes. These amplify the electrons by secondary emission at each electrode and accelerate the particles to the next stage. The final, amplified signal is extracted from the anode at the end of the tube.