Wiktionary
n. (context physics English) Any device that produces a stream of electrons, especially a narrow stream that is focused onto a phosphor screen.
WordNet
n. the electrode that is the source of electrons in a cathode-ray tube or electron microscope; consists of a cathode that emits a stream of electrons and the electrostatic or electromagnetic apparatus that focuses it
Wikipedia
An electron gun (also called electron emitter) is an electrical component in some vacuum tubes that produces a narrow, collimated electron beam that has a precise kinetic energy. The largest use is in cathode ray tubes (CRTs), used in nearly all television sets, computer displays and oscilloscopes that are not flat-panel displays. They are also used in field emission displays (FEDs), which are essentially flat-panel displays made out of rows extremely small cathode ray tubes. They are also used in microwave linear beam vacuum tubes such as klystrons, inductive output tubes, travelling wave tubes, and gyrotrons, as well as in scientific instruments such as electron microscopes and particle accelerators. Electron guns may be classified by the type of electric field generation (DC or RF), by emission mechanism ( thermionic, photocathode, cold emission, plasmas source), by focusing (pure electrostatic or with magnetic fields), or by the number of electrodes.
Usage examples of "electron gun".
Theoretically, this hole is of uniform width, from muzzle of the electron gun to target-that, after all, is the rationale of the weapon: an intense concentration of electrons along a single axis.
It has not been released yet, but that deadly new electron gun worked perfectly and there are hundreds of them there.
With its instrument panels, power units, electron gun and optical column, X-ray analyzer, and vacuum chamber attached to a cylinder of nitrogen, the SEM looked like a console for the space shuttle.
Three workers squatted before the chamber that housed the electron gun.
You've also got a charge on your ship, so you need an electron gun to get rid of that.