Used with a scintillation crystal to make up a scintillation counter. The flash of light produced in the phosphor of a radiation detector strikes the sensitive surface of a photocathode in the photomultiplier, causing the emission of a number of primary electrons. These electrons are drawn to an anode maintained at a higher potential, and a number of secondary electrons are emitted for each impinging electron. The secondary electrons are drawn to a second anode maintained at a higher potential than the first. whereupon additional multiplication occurs. This process is repeated in about ten stages until the initial current has been multiplied about a millionfold. The amplitude of the output of the photomultiplier is proportional to the intensity of the scintillation in the phosphor. See also scintillation counter.
