The detectors described so far all register the ionisation produced by radiation in a gas. The scintillation detector works on quite a different principle; it measures radiation by detecting tiny flashes of light which radiation produces in certain materials. These light flashes, called scintillation, are converted to electrical pulses and, when fed into suitable electronics, can discriminate between different types of radiation and even between different energies of the same radiation.
There are several types of scintillation counters, but their detector systems always consist of two components which are optically coupled. The first is a scintillator . This is a solid or liquid which emits light pulses when radiation deposits energy in it. This is called the scintillation `phosphor' . The second component is a photomultiplier which converts this light pulse into a pulse of electric current.