Cold cathode - definition of
Cold cathode - definition of
Cold cathode is electrode emitting electrons without the need for heating, as opposed to glow cathodes, which require high temperatures to achieve thermionic emission. Emission in the case of a cold cathode is by field emission, secondary emission or emission by interaction with an ionised gas. It is most commonly encountered under conditions of electrical discharge in a gas, where a strong electric field accelerates the electrons and causes them to be released from the electrode surface.
Cold cathodes are used in many vacuum and gas devices, such as fluorescent lamps, discharge lamps, nixie indicators, ionisation manometers or X-ray sources. In modern technology they are also used in cold cathode fluorescent lamps (CCFL - Cold Cathode Fluorescent Lamp) Cold Cathode Fluorescent Lamp) and in some microscale constructions, based on carbon nanotubes and emitters of semiconductor materials.
Cold cathode design can be based on metals with low electron exit work, micro-scale blade materials, or on special coatings with electron emission properties. The key performance parameter is the value of the electric field required to initiate emission, as well as the durability of the material under ion bombardment conditions.
Cold cathodes have the advantage of immediate availability and low power consumption for emission purposes, which makes them advantageous in applications requiring quick turn-on and operation under vacuum conditions. On the other hand, their disadvantages can be their limited lifetime compared to hot cathode designs and greater sensitivity to changes in operating conditions, such as gas pressure, temperature and degree of electrode contamination. In vacuum technology and microelectronics advanced cold cathode solutions are being developed, that integrate material properties with precise emitter geometry.
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