Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Electron gun - Wikipedia, the free encyclopedia 8/22/11 3:49 PM Electron gun From Wikipedia, the free encyclopedia An electron gun (also called electron emitter) is an electrical component that produces an electron beam that has a precise kinetic energy and is most often used in television sets and computer displays which use cathode ray tube (CRT) technology, as well as in other instruments, such as electron microscopes and particle accelerators. Electron guns may be classified in several ways: Electron gun from a cathode ray tube by the type of electric field generation (DC or RF), by emission mechanism (thermionic, photocathode, cold emission, plasma source), by focusing (pure electrostatic or with magnetic fields), or by the number of electrodes. Contents 1 Characteristics 2 Applications 3 See also 4 References 5 External links Electron gun from an oscilloscope CRT Characteristics A direct current, electrostatic thermionic electron gun is formed from several parts: a hot cathode, which is heated to create a stream of electrons via thermionic emission, electrodes generating an electric field which focus the beam (such as a Wehnelt cylinder), and one or more anode electrodes which accelerate and further focus the electrons. A large voltage between the cathode and anode accelerates the electrons. A repulsive ring placed between them focuses the electrons onto a small spot on the anode at the expense of a lower extraction field strength on the cathode surface. Often at this spot is a hole so that the electrons that pass through the anode form a collimated beam and finally reach a second anode called a collector. This arrangement is similar to an Einzel lens. An ion gun consists of a cylinder where gas enters from one end face, undergoes electron bombardment from the side walls, and is subjected to an extraction voltage from the other end face. The entire cage has the role of the cathode; the extractor acts as the anode, and an unnamed ring takes the role of the Wehnelt cylinder. Most color cathode ray tubes — such as those used in color televisions — incorporate three electron guns, each one producing a different stream of electrons. Each stream travels through a shadow mask where the electrons will impinge upon either a red, green or blue phosphor to light up a color pixel on the screen. The resultant http://en.wikipedia.org/wiki/Electron_gun Page 1 of 2 Electron gun - Wikipedia, the free encyclopedia 8/22/11 3:49 PM color that is seen by the viewer will be a combination of these three primary colors. Applications The most common use of electron guns is in cathode ray tubes, which were widely used in computer and television monitors. An electron gun can also be used to ionize particles by adding or removing electrons from an atom. This technology is sometimes used in mass spectrometry in a process called electron ionization to ionize vaporized or gaseous particles. See also Cathode ray tube Electron microscope Optics Particle accelerators References External links Howstuffworks.com: electron gun (http://electronics.howstuffworks.com/question694.htm) Retrieved from "http://en.wikipedia.org/wiki/Electron_gun" Categories: Electron beam | Particle accelerators | Vacuum tubes This page was last modified on 20 August 2011 at 00:29. Text is available under the Creative Commons Attribution-ShareAlike License; additional terms may apply. See Terms of use for details. Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc., a non-profit organization. http://en.wikipedia.org/wiki/Electron_gun Page 2 of 2