scintillator

thumb|right|Scintillation crystal surrounded by various scintillation detector assemblies thumb|Extruded plastic scintillator material fluorescing under a UV inspection lamp at [[Fermilab for the MINERνA project]] thumb|Various scintillation crystals. The second crystal from the left is targeted by an UV source and shines brightly in visible light. A scintillator ( ) is a material that exhibits scintillation (also termed radioluminescence), a kind of luminescence, when excited by ionizing radiation. Luminescent materials, when struck by an incoming particle, absorb its energy and scintillate (i.e. re-emit the absorbed energy in the form of light). Sometimes, the excited state is metastable, so the relaxation back down from the excited state to lower states is delayed (necessitating anywhere from a few nanoseconds to hours depending on the material). The process then corresponds to one of two phenomena: delayed fluorescence or phosphorescence. The correspondence depends on the type of transition and hence the wavelength of the emitted optical photon.

==Principle of operation== A scintillation detector or scintillation counter is obtained when a scintillator is coupled to an electronic light sensor such as a photomultiplier tube (PMT), photodiode, or silicon photomultiplier. PMTs absorb the light emitted by the scintillator and re-emit it in the form of electrons via the photoelectric effect. The subsequent multiplication of those electrons (sometimes called photo-electrons) results in an electrical pulse which can then be analyzed and yield meaningful information about the particle that originally struck the scintillator.