Editing Cathode (section)

====Cold cathode====
{{Main|Cold cathode}}
This is a cathode that is not heated by a filament. They may emit electrons by [[field electron emission]], and in gas-filled tubes by [[secondary emission]]. Some examples are electrodes in [[neon light]]s, [[cold-cathode fluorescent lamp]]s (CCFLs) used as backlights in laptops, [[thyratron]] tubes, and [[Crookes tube]]s. They do not necessarily operate at room temperature; in some devices the cathode is heated by the electron current flowing through it to a temperature at which [[thermionic emission]] occurs. For example, in some fluorescent tubes a momentary high voltage is applied to the electrodes to start the current through the tube; after starting the electrodes are heated enough by the current to keep emitting electrons to sustain the discharge.{{Citation needed|date=February 2024}}

Cold cathodes may also emit electrons by [[photoelectric emission]]. These are often called ''photocathodes'' and are used in [[phototube]]s used in scientific instruments and [[image intensifier]] tubes used in night vision goggles.{{Citation needed|date=February 2024}}