Electron gun. (n.d.). In YourDictionary. Retrieved from https://www.yourdictionary.com/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.