| a device consisting of the cathode ray tube, which emits electrons, and a surrounding electrostatic or electromagnetic apparatus, which controls, focuses, and accelerates the stream of electrons (electron beam). |
| electron gun
The part of a cathode-ray tube that emits a narrow beam of electrons, consisting of a cathode, control grids, and usually a heater. Electrons are emitted from the cathode, which is typically heated by electric current to give the electrons escape energy. The electrons are then focused into a beam by the electric fields of the control grids. |
electron beam
stream of electrons (as from a betatron) generated by heat (thermionic emission), bombardment of charged atoms or particles (secondary electron emission), or strong electric fields (field emission). Electrons may be collimated by holes and slits, and, because they are electrically charged, they may be deflected, focused, and energized by electric and magnetic fields. Electron beams are used chiefly in research, technology, and medical therapy to produce X rays and images on television screens, oscilloscopes, and electron microscopes.
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