cold cathode

A cold cathode gas filled tube or vacuum tube is one in which there is no cathode heater. It contrasts with a cathode that is heated to induce thermionic emission of electrons. Cold cathodes sometimes have rare earth coating on them for enhancing electron emission. Some types contain a source of beta radiation to start ionization of the gas that fills the tube. In such a tube, glow discharge is usually minimized, in favor of arc discharge. The best example is the humble neon lamp. Another good example is Nixie tubes. Nixie tubes too are cold-cathode, neon displays that also happen to be in-line, but not in-plane display devices. A common cold cathode application is in neon signage. Other examples include the thyratron, krytron, sprytron, and ignitron tubes. Cold cathode fluorescent lamps have been produced in the past, but these are now obsolete.

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