In vacuum tubes, a hot cathode is a cathode electrode which emits electrons due to thermionic emission. In the accelerator physics (particle accelerator) community, these are referred to as thermionic cathodes. The heating element is usually an electrical filament. Hot cathodes typically achieve much higher power density than cold cathodes, emitting significantly more electrons from the same surface area. Cold cathodes rely on field electron emission or secondary electron emission from positive ion bombardment and do not require heating.
Hot cathodes are the main source of electrons in electron guns in cathode ray tubes, electron microscopes, vacuum tubes, and fluorescent lamps.
Read more about Hot Cathode: Principles, Cathode Heater, Failure Modes, Transmitting Tube Hot Cathode Characteristics
Famous quotes containing the word hot:
“When shot, the deer seldom drops immediately, but runs sometimes for hours, the hunter in hot pursuit. This phase, known as ‘deer running,’ develops fleet runners, particularly in deer- jacking expeditions when the law is pursuing the hunters as swiftly as the hunters are pursuing the deer.”
—For the State of Maine, U.S. public relief program (1935-1943)