scintillation counter

scintillation counter device for detecting and measuring radiation by means of tiny visible flashes produced by the radiation when it strikes a sensitive substance known as a phosphor (see phosphorescence ). Phosphors used in scintillation counters include zinc sulfide, sodium iodide, various liquids, and organic phosphors. The individual flashes are caused by absorption and reemission of radiation by the phosphor. They may be amplified by photomultiplier devices or amplified and converted to an electrical signal by photoemissive substances (see photoelectric effect ). Scintillation counters may be used to detect the various types of radioactivity (alpha, beta, and gamma rays), cosmic rays, and various elementary particles .

scintillation counter A device for detecting high-energy X-rays and gamma rays. It makes use of the effect of scintillation, in which the incident radiation is converted into a flash of light by interaction with a sensitive material such as caesium iodide or sodium iodide (CsI or NaI). The intensity of the flash is proportional to the energy of the radiation, and it can be converted into an electronic signal by a photomultiplier tube or, in an imaging telescope, by a microchannel plate detector or charge-coupled device.

scintillation counter A type of particle or radiation counter that makes use of the flash of light (scintillation) emitted by an excited atom falling back to its ground state after having been excited by a passing photon or particle. The scintillating medium is usually either solid or liquid and is used in connection with a photomultiplier, which produces a pulse of current for each scintillation. The pulses are counted to enable the radioactivity of the source to be calculated. The distribution of a radiolabelled compound, such as a drug, in an organism can be determined in this way by testing tissue samples from different organs after drug administration.