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[foh-tuh-muhl-tuh-plahy-er] /ˌfoʊ təˈmʌl təˌplaɪ ər/

an extremely sensitive detector of light and of other radiation, consisting of a tube in which the electrons released by radiation striking a photocathode are accelerated, greatly amplifying the signal obtainable from small quantities of radiation.
a device sensitive to electromagnetic radiation, consisting of a photocathode, from which electrons are released by incident photons, and an electron multiplier, which amplifies and produces a detectable pulse of current
An electrical device designed for the detection of weak electromagnetic radiation, usually light, by amplifying the energy of the photons that strike it into stronger electrical signals. Photomultipliers are used in night-vision technology and in telescopes to detect light not strong enough to be visible by the unaided eye. ◇ The most common photomultiplier is the tube photomultiplier; it exploits secondary emission of electrons in a vacuum tube in the manner of an electron multiplier. When radiation strikes the cathode of a tube photomultiplier, electrons called photoelectrons are emitted and attracted to positively charged electrodes called dynodes. When they collide with the dynode, more electrons are released; these are in turn attracted to another dynode at a higher voltage to release yet more electrons, and so on. At the end of this process, there is a current flow at the anode that is strong enough to be easily detected.


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