Scintillation counter

A scintillation counter is an instrument for detecting and measuring ionizing radiation by using the excitation effect of incident radiation on a scintillating material, and detecting the resultant light pulses. It consists of a scintillator which generates photons in response to incident radiation, a sensitive photodetector (usually a photomultiplier tube (PMT), a charge-coupled device (CCD) camera, or a photodiode), which converts the light to an electrical signal and electronics to process this signal. Scintillation counters are widely used in radiation protection, assay of radioactive materials and physics research because they can be made inexpensively yet with good quantum efficiency, and can measure both the intensity and the energy of incident radiation. The first electronic scintillation counter was invented in 1944 by Sir Samuel Curran whilst he was working on the Manhattan Project at the University of California at Berkeley. There was a requirement to measure the radiation from small quantities of uranium, and his innovation was to use one of the newly-available highly sensitive photomultiplier tubes made by the Radio Corporation of America to accurately count the flashes of light from a scintillator subjected to radiation. This built upon the work of earlier researchers such as Antoine Henri Becquerel, who discovered radioactivity whilst working on the phosphorescence of uranium salts in 1896. Previously, scintillation events had to be laboriously detected by eye, using a spinthariscope (a simple microscope) to observe light flashes in the scintillator. The first commercial liquid scintillation counter was made by Lyle E. Packard and sold to Argonne Cancer Research Hospital at the University of Chicago in 1953. The production model was designed especially for tritium and carbon-14 which were used in metabolic studies in vivo and in vitro. When an ionizing particle passes into the scintillator material, atoms are excited along a track. For charged particles the track is the path of the particle itself.