Editing Cold cathode (section)

==Applications==
{{multiple image
| total_width       = 350
| image1            = CCFL bulb.jpg
| caption1          = A photo of an illuminated compact fluorescent lamp (CFL) of the cold-cathode variety
| image2            = Cold-Cathode-CFL-illuminated.jpg
| caption2          = An illuminated cold-cathode [[Compact fluorescent lamp|CFL]]
}}
Cold cathodes are used in [[cold-cathode rectifier]]s, such as the [[crossatron]] and [[mercury-arc valve]]s, and [[cold-cathode amplifier]]s, such as in [[automatic message accounting]] and other [[pseudospark switch]]ing applications. Other examples include the [[thyratron]], [[krytron]], [[sprytron]], and [[ignitron]] tubes.

A common cold-cathode application is in [[neon sign]]s and other locations where the ambient temperature is likely to drop well below freezing, The [[Clock Tower, Palace of Westminster]] (Big Ben) uses cold-cathode lighting behind the clock faces where continual striking and failure to strike in cold weather would be undesirable. Large cold-cathode fluorescent lamps (CCFLs) have been produced in the past and are still used today when shaped, long-life linear light sources are required. {{As of|2011}}, miniature CCFLs were extensively used as [[backlight]]s for [[computer]] and television [[liquid-crystal display]]s. CCFL lifespans vary in LCD televisions depending on transient voltage surges and temperature levels in usage environments.

Due to its efficiency, CCFL technology has expanded into room lighting. Costs are similar to those of traditional [[fluorescent lighting]],{{Clarify|date=August 2011|reason=is this cost of lamps, running cost, total cost?}} but with several advantages: it has a long life, the light emitted is {{clarify span|easier on the eyes|what?|date=October 2017}}, bulbs turn on instantly to full output and are also dimmable.<ref name="Solé Lighting">[http://solelighting.com/ Solé Lighting] (commercial site advocating CCFLs).</ref>

===Effects of internal heating===
In systems using [[alternating current]] but without separate [[anode]] structures, the electrodes alternate as anodes and cathodes, and the impinging electrons can cause substantial localized heating, often to [[red heat]]. The electrode may take advantage of this heating to facilitate the thermionic emission of electrons when it is acting as a cathode. (''Instant-start'' fluorescent lamps employ this aspect; they start as cold-cathode devices, but soon localized heating of the fine [[tungsten]]-wire cathodes causes them to operate in the same mode as [[hot-cathode]] lamps.)

This aspect is problematic in the case of backlights used for [[liquid-crystal display|LCD]] TV displays. New energy-efficiency regulations being proposed in many countries will require variable backlighting; variable backlighting also improves the perceived contrast range, which is desirable for LCD TV sets. However, CCFLs are strictly limited in the degree to which they can be dimmed, both because a lower plasma current will lower the temperature of the cathode, causing erratic operation, and because running the cathode at too low a temperature drastically shortens the life of the lamps.{{citation needed|date=November 2015}} Much research is being directed to this problem, but high-end manufacturers are now turning to high-efficiency white [[LED]]s as a better solution.{{citation needed|date=December 2021}}