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A cold cathode is an element used within some Nixie tubes, gas discharge lamps, gas filled tubes, and vacuum tubes. Cold cathodes do not employ a cathode heater. An ion source is an electro-magnetic device that is used to create charged particles. ... The ten digits of a Z560M Nixie tube. ... It has been suggested that this article or section be merged with Fluorescent lamp. ... Gas filled tubes are arrangements of electrodes in a gas within an insulating, temperature-resistant envelope. ... Structure of a vacuum tube diode Structure of a vacuum tube triode In electronics, a vacuum tube, electron tube, or (outside North America) thermionic valve or just valve, is a device used to amplify, switch or modify a signal by controlling the movement of electrons in an evacuated space. ... A cathode heater, often in the form of a coil or filament with low voltage DC aplied, whose purpose is to heat the cathode in an electrical valve or cathode ray tube. ...

Cold cathode fluorescent lamps (CCFLs) are usually also called cold cathodes. Neon lamps are a very common example of a cold cathode lamp. Fluorescent lamps Assorted types of fluorescent lamps. ... Lighting neon lamp, two 220/230 volt and 110 V neon lamps and a screwdriver with neon lamp inside A neon lamp is a gas discharge lamp containing primarily neon gas at low pressure. ...

Cold Cathodes remain popular for LCD backlighting and enthusiast computer case modders.

Electron emission

A cathode is any electrode that emits electrons. When used in electrical and electronic devices (most fluorescent lamps, vacuum tubes, etc.), the cathode is explicitly heated, creating a hot cathode. By taking advantage of thermionic emission, electrons can overcome the work function of the cathode without an electric field to pull the electrons out. But if sufficient voltage is present, electrons can still be stripped even out of a cathode operating at ambient temperature. Because it is not deliberately heated, such a cathode is referred to as a cold cathode, although several mechanisms may eventually cause the cathode to become quite hot once it is operating. Most cold cathode devices are filled with a gas which can be ionized. A few cold cathode devices contain a vacuum. Diagram of a copper cathode in a Daniells cell. ... For other uses, see Electrode (disambiguation). ... For other uses, see Electron (disambiguation). ... Fluorescent lamps Assorted types of fluorescent lamps. ... Structure of a vacuum tube diode Structure of a vacuum tube triode In electronics, a vacuum tube, electron tube, or (outside North America) thermionic valve or just valve, is a device used to amplify, switch or modify a signal by controlling the movement of electrons in an evacuated space. ... Hot cathode is also a name for a hot filament ionization gauge, a vacuum measuring device. ... Closeup of the filament on a low pressure mercury gas discharge lamp showing white thermionic emission mix coating on the central portion of the coil. ... The work function is the minimum energy (usually measured in electron volts) needed to remove an electron from a solid to a point immediately outside the solid surface. ... In physics, the space surrounding an electric charge or in the presence of a time-varying magnetic field has a property called an electric field. ... For other uses, see Room temperature (disambiguation). ... For other uses, see Gas (disambiguation). ... This article is about the electrically charged particle. ... Look up Vacuum in Wiktionary, the free dictionary. ...

Details

Before discussing cathode ray tubes of any kind, a few basic terms must be defined:

The cathode is the negative electrode. Any gas discharge lamp has a pair of electrodes, acting as cathode and anode (the positive electrode). Both electrodes act alternating as anode and cathode because the devices run with alternating current. City lights viewed in a motion blurred exposure. ...

A standard ATX computer case fitted with blue and green Cold Cathode tubes.

A cold cathode is distinguished from a hot cathode that is heated to induce thermionic emission of electrons. Discharge tubes with hot cathodes have an envelope filled with low pressure gas and containing a pair of cathodes. Examples are common fluorescent lamps, high pressure discharge lamps and [completely-evacuated] electron tubes and vacuum fluorescent displays. The ATX (for Advanced Technology Extended) form factor was created by Intel in 1995. ... Hot cathode is also a name for a hot filament ionization gauge, a vacuum measuring device. ... Closeup of the filament on a low pressure mercury gas discharge lamp showing white thermionic emission mix coating on the central portion of the coil. ... For other uses, see Electron (disambiguation). ... Fluorescent lamps Assorted types of fluorescent lamps. ... Electron tube can be used to describe either of two things: vacuum tube gas filled tube This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ... A full view of a typical vacuum fluorescent display used in a videocassette recorder A close-up of the VFD highlighting the multiple filaments, tensioned by the sheet metal springs at the right of the image A vacuum fluorescent display (VFD) is a type of display used commonly on consumer...

The interior surface of cold cathodes are capable of producing secondary electrons at a ratio greater than unity (amplification) upon electron and ion impact. For accelerating of the ions to a sufficient velocity for creating free electrons from the cathode material, cold cathode discharge lamps need higher voltages than hot cathode ones, causing a strong electric field near the cathodes. Secondary electrons are electrons generated as ionization products. ...

Another mechanism for generating free electrons from a cold metallic surface is field emission. It is used in some x-ray tubes and the field electron microscope. Field emission, also known as Fowler-Nordheim tunneling, is a form of quantum tunneling in which electrons pass through a barrier in the presence of a high electric field. ... An X-Ray tube is a vacuum tube designed to produce man made X-Ray photons on demand. ...

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 around the cathode is usually minimized, in favor of a so called positive column, filling the tube. 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. Rare earth ore Rare earth elements and rare earth metals are trivial names sometimes applied to a collection of 17 chemical elements in the periodic table, namely scandium, yttrium, and the lanthanides. ... Beta particles are high-energy electrons emitted by certain types of radioactive nuclei such as potassium-40. ... Ionization is the physical process of converting an atom or molecule into an ion by changing the difference between the number of protons and electrons. ... Electric glow discharge is a type of plasma formed by passing a current at 100V to several kV through a gas - usually argon or another noble gas. ... Lighting neon lamp, two 220/230 volt and 110 V neon lamps and a screwdriver with neon lamp inside A neon lamp is a gas discharge lamp containing primarily neon gas at low pressure. ... The ten digits of a Z560M Nixie tube. ... The ten digits of a Z560M Nixie tube. ...

Currently type CCFL inverter

Example of the CCFL Inverter for notebook

A common cold cathode application is in neon signage. Other examples include the thyratron, krytron, sprytron, and ignitron tubes. Large-scale 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. Nowadays, miniature CCFLs are extensively used as backlights for computer liquid crystal displays. Additionally, CCFLs are used by computer modders to light the insides of their customized computer cases. Neon signs are often used to advertise for hotels, bars and entertainment venues. ... A thyratron is a type of gas filled tube used as a high energy electrical switch. ... The Krytron is a cold-cathode gas filled tube intended for use as a very high-speed switch and was one of the earliest developments of the EG&G Corporation. ... Krytron is one of the earliest developments of the EG&G Corporation. ... An ignitron is a type of controlled rectifier dating from the 1930s. ... Fluorescent lamps Assorted types of fluorescent lamps. ... Backlights are lights that are attached to LCD displays so that they can be seen at night. ... This article is about the machine. ... LCD redirects here. ... Modded PC case with light & switch, perspex window and fan hole Case modification (commonly referred to as Case modding) is the modification of a computer chassis (often just referred to as the case), or a video game console chassis. ...

Despite their name, cold cathodes don't necessarily remain cold as they operate; they can get painfully hot. In systems using alternating current but without separate anode structures, the cathodes alternate as anodes and the impinging electrons can cause substantial localized heating, often to red heat. The cathode may or may not take advantage of this heating to facilitate the thermionic emission of electrons when it is acting as a cathode. (Instant start fluorescent lamps definitely do employ this aspect; they start as cold-cathode devices but soon localized heating of the fine tungsten wire cathodes causes them to operate as ordinary hot cathode lamps.) City lights viewed in a motion blurred exposure. ... Diagram of a zinc anode in a galvanic cell. ... For other uses, see Tungsten (disambiguation). ... Hot cathode is also a name for a hot filament ionization gauge, a vacuum measuring device. ...

Cold cathode devices typically use a complex high-voltage power supply with some mechanism for limiting current flow. Although creating the initial space charge and the first arc of current through the tube may require a very high voltage, once the tube begins to heat up, the resistance to current flow begins to drop, requiring a gradually lower voltage to maintain operation. In the case of tubes with an ionizing gas, the gas can become a very hot plasma where electrical resistance is greatly reduced. If operated from a simple power supply without current limiting, this reduction in operational resistance would lead to damage to the power supply or the tube electrodes from overheating. For other uses, see Plasma. ...

See also

• Ionization gauge
• ANITA electronic calculator

An ionization gauge, or ion gauge, is a vacuum gauge that is used to measure the residual pressure of vacuum in the high vacuum and ultra-high vacuum (UHV) ranges. ... The British ANITA calculator, first manufactured by Sumlock in 1960, was the first electronic desktop calculator. ...

References

Patents

• U.S. Patent 2,184,910  - Philo Farnsworth - Cold cathode electron discharge tube
• U.S. Patent 2,263,032  - Philo Farnsworth - Cold cathode electron discharge tube
• U.S. Patent 2,448,527  - Clarence W. Hansell - Cold cathode electron discharge device and circuits therefore

Philo Taylor Farnsworth (August 19, 1906 – March 11, 1971) was an American inventor. ... Clarence Weston Hansell was an American research engineer who pioneered investigation into the biological effects of ionized air. ...

External links

• Pulse Power Switching Devices - An Overview- by John Pasley
• Replacing the CCFL of a notebook - a step by step procedure

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