Photomultiplier

  A device to convert light into an electric signal (the name is often abbreviated to PM). Photomultipliers are of great relevance in all detectors based on scintillating material. A photomultiplier consists of a photocathode (photons are converted into electrons, making use of the photoelectric effect), a multiplier chain (strings of successive electron absorbers with enhanced secondary emission, called dynodes , the entire string using electric fields to accelerate electrons), and an anode, which collects the resulting current. Commercial PMs vary in speed and linearity of response, in the time fluctuations of the signal, in amplification factor (called gain), in the wavelength spectrum accepted, etc. A good intoductory discussion can be found in [Leo94], and in the manufacturers' catalogues.