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18 novembre 2011 5 18 /11 /novembre /2011 02:39

Neon is the chemical element that has the symbol Ne and an atomic number of 10. Although a very common element in the universe, it is rare on Earth. A colorless, inert noble gas under standard conditions, neon gives a distinctreddish-orange glow when used in either low-voltage neon glow lamps or in high-voltage discharge tubes or neon advertising signs.Sony VAIO VGN-AW91JS Battery

It is commercially extracted from air, in which it is found in trace amounts.

Neon (Greek ???? (neon) meaning "new one") was discovered in 1898 by the British chemists Sir William Ramsay (1852–1916) and Morris W. Travers (1872–1961) in London.Sony VAIO VGN-AW91YS Battery

Neon was discovered when Ramsay chilled a sample of the atmosphere until it became a liquid, then warmed the liquid and captured the gases as they boiled off. The gases that boiled off, in addition to nitrogen, oxygen, and argon, were krypton, xenon, and neon.Sony VAIO VGN-AW92CDS Battery

The characteristic, brilliant red color that is emitted by gaseous neon when excited electrically was noted immediately; Travers later wrote, "the blaze of crimson light from the tube told its own story and was a sight to dwell upon and never forget."Sony VAIO VGN-AW92CJS Battery

Neon's scarcity precluded its prompt application for lighting along the lines of Moore tubes, which used nitrogen and which were commercialized in the early 1900s. After 1902,Georges Claude's company, Air Liquide, was producing industrial quantities of neon as a byproduct of his air liquefaction business, Sony VAIO VGN-AW92CYS Battery

and in December 1910 Claude demonstrated modern neon lighting based on a sealed tube of neon. In 1912, Claude's associate began selling neon discharge tubes asadvertising signs. They were introduced to U.S. in 1923, when two large neon signs were bought by a Los Angeles Packard car dealership.Sony VAIO VGN-AW92DS Battery

The glow and arresting red color made neon advertising completely different from the competition.

Neon played a role in the basic understanding of the nature of atoms in 1913, when J. J. Thomson, as part of his exploration into the composition of canal rays, channeled streams of neon ions through a magnetic and an electric field and measured their deflection by placing a photographic plate in their path.Sony VAIO VGN-AW92JS Battery

Thomson observed two separate patches of light on the photographic plate (see image), which suggested two different parabolas of deflection. Thomson eventually concluded that some of the atoms in the neon gas were of higher mass than the rest. Though not understood at the time by Thomson, this was the first discovery of isotopes of stable atoms. Sony VAIO VGN-AW92YS Battery

It was made by using a crude version of an instrument we now term as a mass spectrometer.

Creation

Stable forms of neon are produced in stars. It is created in fusing helium and oxygen in the alpha process, which requires temperatures above 100 megakelvin and masses greater than 3 solar masses.Sony VAIO VGN-AW93FS Battery

Isotopes

Neon is the second lightest inert gas. Neon has three stable isotopes: 20Ne (90.48%), 21Ne (0.27%) and 22Ne (9.25%). 21Ne and 22Ne are partly primordial and partly nucleogenic (i.e., made by nuclear reactions of other nuclides with neutrons or other particles in the environment) and their variations in natural abundance are well understood.Sony VAIO VGN-AW93GS Battery

In contrast, 20Ne (the chief primordial isotope made in stellar nucleosynthesis) is not known to be nucleogenic or radiogenic (save forcluster decay production, which is thought to produce only a small amount). The causes of the variation of 20Ne in the Earth have thus been hotly debated.Sony VAIO VGN-AW93HS Battery

The principal nuclear reactions which generate nucleogenic neon isotopes start from 24Mg and 25Mg, which produce 21Ne and 22Ne, respectively, after neutron capture and immediate emission of analpha particle. The neutrons that produce the reactions are mostly produced by secondary spallation reactions from alpha particles, in turn derived from uranium-series decay chains. Sony VAIO VGN-AW93ZFS Battery

The net result yields a trend towards lower 20Ne/22Ne and higher 21Ne/22Ne ratios observed in uranium-rich rocks such as granites. Neon-21 may also be produced in a nucleogenic reaction, when 20Ne absorbs a neutron from various natural terrestrial neutron sources.Sony VAIO VGN-AW93ZGS Battery

In addition, isotopic analysis of exposed terrestrial rocks has demonstrated the cosmogenic(cosmic ray) production of 21Ne. This isotope is generated by spallation reactions on magnesium,sodium, silicon, and aluminium. By analyzing all three isotopes, the cosmogenic component can be resolved from magmatic neon and nucleogenic neon. Sony VAIO VGN-AW93ZHS Battery

This suggests that neon will be a useful tool in determining cosmic exposure ages of surface rocks and meteorites.

Similar to xenon, neon content observed in samples of volcanic gases is enriched in 20Ne, as well as nucleogenic 21Ne, relative to 22Ne content. Sony VAIO VGN-BZ11EN Battery

The neon isotopic content of these mantle-derived samples represents a non-atmospheric source of neon. The 20Ne-enriched components are attributed to exotic primordial rare gas components in the Earth, possibly representing solar neon. Elevated 20Ne abundances are found in diamonds, further suggesting a solar neon reservoir in the Earth.Sony VAIO VGN-BZ11MN Battery

Characteristics

Neon is the second-lightest noble gas, after helium. It glows reddish-orange in a vacuum discharge tube. Also, neon has the narrowest liquid range of any element: from 24.55 K to 27.05 K (?248.45 °C to ?245.95 °C, or ?415.21 °F to ?410.71 °F).Sony VAIO VGN-BZ11XN Battery

It has over 40 times the refrigerating capacity of liquid helium and three times that of liquid hydrogen (on a per unit volume basis). In most applications it is a less expensive refrigerant than helium.

Neon plasma has the most intense light discharge at normal voltages and currents of all the noble gases. Sony VAIO VGN-BZ12VN Battery

The average color of this light to the human eye is red-orange due to many lines in this range; it also contains a strong green line which is hidden, unless the visual components are dispersed by a spectroscope.

Two quite different kinds of neon lighting are in common use. Neon glow lamps are generally tiny, with most operating at about 100–250 volts.Sony VAIO VGN-BZ12XN Battery

They have been widely used as power-on indicators and in circuit-testing equipment, but light-emitting diodes (LEDs) now dominate in such applications. These simple neon devices were the forerunners ofplasma displays and plasma television screens. Neon signs typically operate at much higher voltages (2–15 kilovolts), and the luminous tubes are commonly meters long.Sony VAIO VGN-BZ31VT Battery

The glass tubing is often formed into shapes and letters for signage as well as architectural and artistic applications.

Occurrence

Neon is actually abundant on a universal scale; it is the fifth most abundant chemical element in the universe by mass, after hydrogen, helium, oxygen, and carbon (see chemical element).Sony VAIO VGN-BZ31XT Battery

Its relative rarity on Earth, like that of helium, is due to its relative lightness, high vapor pressure at very low temperatures, and chemical inertness, all properties which tend to keep it from being trapped in the condensing gas and dust clouds which resulted in the formation of smaller and warmer solid planets like Earth.Sony VAIO VGN-BZ560 Battery

Neon is monatomic, making it lighter than the molecules of diatomic nitrogen and oxygen which form the bulk of Earth's atmosphere; a balloon filled with neon will rise in air, albeit more slowly than a helium balloon.

Mass abundance in the universe is about 1 part in 750 and in the Sun and presumably in the proto-solar system nebula, about 1 part in 600.Sony VAIO VGN-BZ560N24 Battery

The Galileo spacecraftatmospheric entry probe found that even in the upper atmosphere of Jupiter, the abundance of neon is reduced (depleted) by about a factor of 10, to a level of 1 part in 6,000 by mass. This may indicate that even the ice-planetesimals which brought neon into Jupiter from the outer solar system, Sony VAIO VGN-BZ560N30 Battery

formed in a region which was too warm for them to have kept their neon (abundances of heavier inert gases on Jupiter are several times that found in the Sun).

Neon is rare on Earth, found in the Earth's atmosphere at 1 part in 65,000 (by volume) or 1 part in 83,000 by mass. It is industrially produced by cryogenicfractional distillation of liquefied air.Sony VAIO VGN-BZ560P Battery

Applications

Neon is often used in signs and produces an unmistakable bright reddish-orange light. Although still referred to as "neon", all other colors are generated with the other noble gases or by many colors of fluorescent lighting.Sony VAIO VGN-BZ560P20 Battery

Neon is used in vacuum tubes, high-voltage indicators, lightning arrestors, wave meter tubes, television tubes, and helium-neon lasers. Liquefied neon is commercially used as a cryogenic refrigerant in applications not requiring the lower temperature range attainable with more extreme liquid helium refrigeration.Sony VAIO VGN-BZ560P22 Battery

Both neon gas and liquid neon are relatively expensive – for small quantities, the price of liquid neon can be more than 55 times that of liquid helium. The driver for neon's expense is the rarity of neon, which unlike helium, can only be obtained from air.

The triple point temperature of neon (24.5561 K) is a defining fixed point in the International Temperature Scale of 1990.Sony VAIO VGN-BZ560P28 Battery

Compounds

Neon is the first p-block noble gas. Neon is generally considered to be inert. No true neutral compounds of neon are known. However, the ions Ne+, (NeAr)+, (NeH)+, and (HeNe+) have been observed from optical and mass spectrometric studies, and there are some unverified reports of an unstable hydrate.Sony VAIO VGN-BZ560P30 Battery

Neon signs are made using electrified, luminous tube lights that contain rarefied neon or other gases. They are the most common use for neon lighting, which was first demonstrated in a modern form in December, 1910 by Georges Claude at the Paris Motor Show.Sony VAIO VGN-BZ560P34 Battery

While they are used worldwide, neon signs were extremely popular in the United States from about 1920–1960. The installations in Times Square were famed, and there were nearly 2000 small shops producing neon signs by 1940. In addition to signage, neon lighting is now used frequently by artists and architects,and (in a modified form) in plasma display panels and televisions.Sony VAIO VGN-BZ561 Battery

The signage industry has declined in the past several decades, and cities are now concerned with preserving and restoring their antique neon signs (see Further reading below).

The neon sign is an evolution of the earlier Geissler tube, which is an electrified glass tube containing a "rarefied" gas (the gas pressure in the tube is well below atmospheric pressure). Sony VAIO VGN-BZ561N20 Battery

When a voltage is applied to electrodes inserted through the glass, an electrical glow discharge results. Geissler tubes were quite popular in the late 1800s, and the different colors they emitted were characteristics of the gases within. They were, however, unsuitable for general lighting; the pressure of the gas inside typically declined in use. Sony VAIO VGN-BZ561P20 Battery

The direct predecessor of neon tube lighting was the Moore tube, which used nitrogen or carbon dioxide as the luminous gas and a patented mechanism for maintaining pressure; Moore tubes were sold for commercial lighting for a number of years in the early 1900s.Sony VAIO VGN-BZ562P Battery

The discovery of neon in 1898 included the observation of a brilliant red glow in Geissler tubes. Immediately following neon's discovery, neon tubes were used as scientific instruments and novelties. A sign created by Perley G. Nutting and displaying the word "neon" may have been shown at the Louisiana Purchase Exposition of 1904, although this claim has been disputed;Sony VAIO VGN-BZ563P Battery

in any event, the scarcity of neon would have precluded the development of a lighting product. However, after 1902, Georges Claude's company in France, Air Liquide, began producing industrial quantities of neon, essentially as a byproduct of their air liquefaction business.Sony VAIO VGN-BZAAFS Battery

From December 3–18, 1910, Claude demonstrated two 12-metre (39 ft) long bright red neon tubes at theParis Motor Show.This demonstration lit a peristyle of the Grand Palais (a large exhibition hall). Claude's associate, Jacques Fonseque, realized the possibilities for a business based on signage and advertising.Sony VAIO VGN-BZAAHS Battery

By 1913 a large sign for the vermouth Cinzano illuminated the night sky in Paris, and by 1919 the entrance to the Paris Opera was adorned with neon tube lighting. Over the next several years, patents were granted to Claude for two innovations still used today:Sony VAIO VGN-BZAANS Battery

a "bombardment" technique to remove impurities from the working gas of a sealed sign, and a design for the internal electrodes of the sign that prevented their degradation by sputtering.

In 1923, Georges Claude and his French company Claude Neon introduced neon gas signs to the United States by selling two to a Packard car dealership in Los Angeles.Sony VAIO VGN-BZAAPS Battery

Earle C. Anthony purchased the two signs reading "Packard" for $1,250 apiece. Neon lighting quickly became a popular fixture in outdoor advertising. Visible even in daylight, people would stop and stare at the first neon signs for hours, dubbed "liquid fire."Sony VAIO VGN-CR11H/B Battery

The next major technological innovation in neon lighting and signs was the development of fluorescent tube coatings. Jacques Risler received a French patent in 1926 for these. Neon signs that use an argon/mercury gas mixture emit a good deal of ultraviolet light.Sony VAIO VGN-CR11S/L Battery

When this light is absorbed by a fluorescent coating, preferably inside the tube, the coating (called a "phosphor") glows with its own color. While only a few colors were initially available to sign designers, after theSecond World War (1939–1945) phosphor materials were researched intensively for use in color televisions. Sony VAIO VGN-CR11S/P Battery

About two dozen colors were available to neon sign designers in the 1960s, and today there are nearly 100 available colors.

Fabrication

Neon tube signs are produced by the craft of bending glass tubing into shapes. A worker skilled in this craft is known as a glass bender, neon bender or tube bender. Sony VAIO VGN-CR11S/W Battery

The neon tube is made out of 4-5' straight sticks of hollow glass sold by sign suppliers to neon shops worldwide, where they are manually assembled into individual custom designed and fabricated lamps. There are many dozens of colors available, determined by the type of glass tubing and the composition of the gas filling.Sony VAIO VGN-CR11Z/R Battery

Neon sign manufacturing is a cottage industry and an eclectic art, and in most cases, is organized as a small family business. Even today, almost all neon tubes are hand made and labor intensive. The shop equipment used to fabricate signs is itself typically custom assembled from scratch from discrete parts by the craftsmen who will use the equipment.Sony VAIO VGN-CR120E/L Battery

Tubing in external diameters ranging from about 8–15 mm with a 1 mm wall thickness is most commonly used, although 6mm tubing is now commercially available in colored glass tubes. The tube is heated in sections using several types of burners that are selected according to the amount of glass to be heated for each bend. Sony VAIO VGN-CR120E/P Battery

These burners include ribbon, cannon, or crossfires, as well as a variety of gas torches. Ribbon burners are strips of fire that make the gradual bends while crossfires, when used, make the sharp bends.

The interior of the tubes may be coated with a thin phosphorescent powder coating, affixed to the interior wall of the tube by a binding material. Sony VAIO VGN-CR120E/R Battery

The tube is filled with a purified gas mixture, and the gas ionized by a high voltage applied between the ends of the sealed tube through cold cathodes welded onto the ends. The color of the light emitted by the tube may be just that coming from the gas, or the light from the phosphor layer. Sony VAIO VGN-CR120E/W Battery

Different phosphor-coated tubing sections may be butt welded together using glass working torches to form a single tube of varying colors, for effects such as a sign where each letter displays a different color letter within a single word, such as shown in the sign in the photo above right.Sony VAIO VGN-CR125E/B Battery

"Neon" is used to denote the general type of lamp, but neon gas is only one of the types of tube gases principally used in commercial application. Pure neon gas is used to produce only about a third of the colors. The greatest number of colors is produced by filling with another inert gas, argon, and a drop of mercury (Hg) which is added to the tube immediately after purification. Sony VAIO VGN-CR13/B Battery

When the tube is ionized by electrification, the mercury evaporates into mercury vapor, which fills the tube and produces strong ultraviolet light. The ultraviolet light thus produced excites the various phosphor coatings designed to produce different colors. Even though this class of neon tubes use no neon at all, they are still denoted as "neon."Sony VAIO VGN-CR13/L Battery

Mercury-bearing lamps are a type of cold-cathode fluorescent lamps.

Each type of neon tubing produces two completely different possible colors, one with neon gas and the other with argon/mercury. Some "neon" tubes are made without phosphor coatings for some of the colors.Sony VAIO VGN-CR13/P Battery

Clear tubing filled with neon gas produces the ubiquitous yellowish orange color with the interior plasma column clearly visible, and is the cheapest and simplest tube to make. Traditional neon glasses in America over 20 years old are lead glass that are easy to soften in gas fires, Sony VAIO VGN-CR13/R Battery

but recent environmental and health concerns of the workers has prompted manufacturers to seek more environmentally safe special soft glass formulas. One of the vexing problems avoided this way is lead glass' tendency to burn into a black spot emitting lead fumes in a bending flame too rich in the fuel/oxygen mixture. Sony VAIO VGN-CR13/W Battery

Another traditional line of glasses was colored soda lime glasses coming in a myriad of glass color choices, which produce the highest quality, most hypnotically vibrant and saturated hues. Still more color choices are afforded in either coating, or not coating, these colored glasses with the various available exotic phosphors.Sony VAIO VGN-CR131E/L Battery

Long lifetime

It is the wide range of colors and the ability to make a tube that can last for years if not decades without replacement, that makes this an art. Since these tubes require so much custom labor, they would have very little economic viability if they did not have such a long lifetime when well processed.Sony VAIO VGN-CR13G Battery

The intensity of neon light produced increases slowly as the tube diameter grows smaller, that is, the intensity varies inversely with the square root of the interior diameter of the tubing, and the resistance of the tube increases as the tubing diameter decreases accordingly, because tube ionization is greatest at the center of the tube, Sony VAIO VGN-CR13G/B Battery

and the ions migrate to and are recaptured and neutralized at the tube walls. The greatest cause of neon tube failure is the gradual absorption of neon gas by high voltage ion implantation into the interior glass walls of the tubes which depletes the gas, and eventually causes the tube resistance to rise to a level that it can no longer light at the rated voltage, but this may take 7–10 years.Sony VAIO VGN-CR13G/L Battery

The actual cause of 80% of neon sign failures is the burnout of the high voltage electrical wires connecting the tubes inside of metal conduits. A very common type of neon sign is made from a formed metal box having a colored translucent face, called "channel lettering". Newer channel letter signs are being replaced by high brightness LEDs.Sony VAIO VGN-CR13G/P Battery

This long lifetime has created a practical market for neon use for interior architectural cove lighting in a wide variety of uses including homes, where the tube can be bent to any shape, fitted in a small space, and can do so without requiring tube replacement for a decade or more.Sony VAIO VGN-CR13G/R Battery

Tube bending

A section of the glass is heated until it is malleable; then it is bent into shape and aligned to a pattern containing the graphics or lettering that the final product will ultimately conform to. This is where the real art of neon comes in that takes some artisans from a year up to several years of practice to master. Sony VAIO VGN-CR13G/W Battery

A tube bender corks off the hollow tube before heating and holds a latex rubber blow hose at the other end, through which he gently presses a small amount of air in order to keep the tube diameter constant as it is bending. The trick of bending is to bend one small section or bend at a time, Sony VAIO VGN-CR13T/L Battery

'heating one part of the tubing so that it is soft, without heating some other part of the tube as well, which would make the bend uncontrollable. A bend, once the glass is heated, must be brought to the pattern and fitted rapidly before the glass hardens again because it is difficult to reheat once completely cooled without risking breakage. Sony VAIO VGN-CR13T/P Battery

It is frequently necessary to skip one or more bends and come back to it later, by measuring carefully along the length of the tube. One tube letter may contain 7-10 small bends, and mistakes are not easily corrected without going back and starting all over again.Sony VAIO VGN-CR13T/R Battery

If more tubing is required, another piece is welded onto it, or the parts can be all welded onto each other at the final step. The finished tube must be absolutely vacuum tight in order to operate, and it must be vacuum clean inside. Once the tube is filled with mercury, if any mistake is made after that, Sony VAIO VGN-CR13T/W Battery

the entire tube had, or should, be started over again, because breathing heated mercury impregnated glass and phosphor causes long term heavy metal poisoning in neon workers. Sticks of tubing are joined until the tube reaches an impractical size, and several tubes are joined in series with the high voltage neon transformer. Sony VAIO VGN-CR15/B Battery

Extreme ends of the electrical circuit must be isolated from each other to prevent tube puncture and buzzing from corona effect.

Bombardment

A cold cathode electrode is melted (or welded) to each end of the tube as it is finished. Sony VAIO VGN-CR150E/B Battery

The electrodes are also traditionally lead glass and contain a small metal shell with two wires protruding through the glass to which the sign wiring will later be attached. All welds and seals must be perfectly leak-proof to high vacuum before proceeding further.Sony VAIO VGN-CR190 Battery

The tube is attached to a manifold which is itself attached to a high-quality vacuum pump. The tube is then evacuated of air until it reaches near-vacuum. During evacuation, a high current is forced through the tube via the wires protruding from each electrode (in a process known as "bombarding").Sony VAIO VGN-CR190E/L Battery

This current and voltage is far above the level that occurs in final operation of the tube. The current depends on the specific electrodes used and the diameter of the tube, but is typically in the 450 mA to 800 mA range, at an applied voltage usually between 22,000-26,000 V.Sony VAIO VGN-CR190E/P Battery

The bombarding transformer acts as an adjustable constant current source, and the voltage produced depends on the length and pressure of the tube. Typically the operator will maintain the pressure as high as the bombarder will allow to ensure maximum power dissipation and heating.Sony VAIO VGN-CR190E/R Battery

This very high power dissipation in the tube heats the glass walls to a temperature of several hundred degrees Celsius, and any dirt and impurities within are drawn off in the gasified form by the vacuum pump. The greatest impurities that are driven off this way are the gases that coat the inside wall of the tubing byadsorption, mainly oxygen, carbon dioxide, and especially water vapor. Sony VAIO VGN-CR190E/W Battery

The current also heats the electrode metal to over 600oC, producing a bright orange incandescent color. The cathodes are prefabricated hollow metal shells with a small opening (sometimes a ceramic donut aperture) which contains in the interior surface of the shell a light dusting of a cold cathode low work function powder Sony VAIO VGN-CR19VN/B Battery

(usually a powder ceramic molar eutectic point mixture including BaCO2, combined with other alkaline earth oxides, which reduces to BaO2 when heated to about 500 degrees F, and reduces the work function of the electrode for cathodic emission. Sony VAIO VGN-CR19XN/B Battery

Barium Oxide has a work function of roughly 2 whereas tungsten at room temperature has a work function exponentially 100 times more, or 4.0. This represents the cathode drop or electron energy required to remove electrons from the surface of the cathode. This avoids the necessity of using a hot wire thermoelectric cathode such as is used in conventional fluorescent lamps.Sony VAIO VGN-CR20 Battery

And for that reason, neon tubes are extremely long lived when properly processed, in contrast to fluorescent tubing, because there is no wire filament as there is in a fluorsecent tube to burn out like a common light bulb. The principal purpose of doing this is to purify the interior of the tube before the tube is sealed off so that when it is operated, Sony VAIO VGN-CR21/B Battery

these gases and impurities are not driven off and released by the plasma and the heat generated into the sealed tube, which would quickly burn the metal cathodes and mercury droplets (if pumped with argon/mercury) and oxidize the interior gases and cause immediate tube failure. Sony VAIO VGN-CR21E/L Battery

The more thorough the purification of the tube is, the longer lasting and stable the tube will be in actual operation. Once these gases and impurities are liberated under pre-filling bombardment into the tube interior they are quickly evacuated by the pump.Sony VAIO VGN-CR21E/P Battery

While still attached to the manifold, the tube is allowed to cool while pumping down to the lowest pressure the system can achieve. It is then filled to a low pressure of a few torrs (millimeters of mercury) with one of the noble gases, or a mixture of them, and sometimes a small amount of mercury. Sony VAIO VGN-CR21E/W Battery

This gas fill pressure represents roughly 1/100th of the pressure of the atmosphere. The required pressure depends on the gas used and the diameter of the tube, with optimal values ranging from 6 Torr (0.8 kPa) (for a long 20 mm tube filled with argon/mercury) to 27 Torr (3.6 kPa) (for a short 8 mm diameter tube filled with pure neon). Sony VAIO VGN-CR21S/L Battery

Neon or argonare the most common gases used; krypton, xenon, and helium are used by artists for special purposes but are not used alone in normal signs. A premixed combination of argon and helium is often used in lieu of pure argon when a tube is to be installed in a cold climate, since the helium increases voltage drop (and thus power dissipation), Sony VAIO VGN-CR21S/P Battery

warming the tube to operating temperature faster. Neon glows bright red or reddish orange when lit. When argon or argon/helium is used, a tiny droplet of mercury is added. Argon by itself is very dim pale lavender when lit, but the droplet of mercury fills the tube with mercury vapor when sealed, which then emitsultraviolet light upon electrification. Sony VAIO VGN-CR21S/W Battery

This ultraviolet emission allows finished argon/mercury tubes to glow with a variety of bright colors when the tube has been coated on the interior with ultraviolet-sensitive phosphors after being bent into shape.

Heat processed neon tubes

An alternate way of processing finished neon tubes has also been used. Sony VAIO VGN-CR21Z/N Battery

Because the only purpose of bombardment by electrical means is to purify the interior of tubes, it is also possible to produce a tube by heating the tube externally either with a torch or with an oven, while heating the electrode with a Radio Frequency Induction Heating coil (RFIH).Sony VAIO VGN-CR21Z/R Battery

While this is less productive, it creates a cleaner custom tube with significantly less cathode damage, longer life and brilliance, and can produce tubes of very small sizes and diameters, down to 6mm OD. The tube is heated thoroughly under high vacuum without external electrical application,Sony VAIO VGN-CR220E/R Battery

until the outgassed gases can be seen to have been totally depleted and the pressure drops to a high vacuum again. Then the tube is filled, sealed and the mercury dropped and shaken.

Electrical wiring

The finished glass pieces are illuminated by either a neon sign transformer or a switching power supply running at voltages ranging between 3-15 kV and currents between 20 and 120 mA.Sony VAIO VGN-CR23/B Battery

These power supplies operate as constant-current sources (a high voltage supply with a very high internal impedance), since the tube has a negative characteristic electrical impedance. Standard tube tables established in the early days of neon are still used that specify the gas fill pressures, in either Ne or Hg/Ar, as a function of tube length in feet, tube diameter and transformer voltage.Sony VAIO VGN-CR23/L Battery

The standard traditional neon transformer, a magnetic shunt transformer, is a special non-linear type designed to keep the voltage across the tube raised to whatever level is necessary to produce the fixed current needed, up to the maximum limit of the neon footage possible.Sony VAIO VGN-CR23/N Battery

Newer, compact high frequency inverter-converter transformers developed in the early '90s are used as well, especially when low Radio Frequency Interference (RFI) is needed, such as in locations near high-fidelity sound equipment. Sony VAIO VGN-CR23/P Battery

The reason for this is that at 20 kHz, the typical frequency of these solid state transformers, the plasma electron-ion recombination time is too short to extinguish and reignite the plasma in the tube at every 1/120th second as in 50/60 Hz transformers and so the plasma does not broadcast high frequency switching noise. Sony VAIO VGN-CR23/R Battery

The plasma simply remains lit at all times, becoming radio noise free.

The most common current rating is 30 mA for general use, with 60 mA used for high-brightness applications like channel letters or architectural lighting. 120 mA sources are occasionally seen in illuminating applications, Sony VAIO VGN-CR23/W Battery

but are uncommon since special electrodes are required to withstand the current, and an accidental shock from a 120 mA transformer is much more likely to be fatal than from the lower current supplies.

The efficiency of neon lighting ranges between that of ordinary incandescent lights and that of fluorescent lamps, depending on color.Sony VAIO VGN-CR240E/B Battery

On a per-watt basis, incandescents produce 10 to 20 lumens, while fluorescents produce 50 to 100 lumens. Neon light efficiency ranges from 10 lumens per watt for red, up to 60 lumens for green and blue when these colors result from internal phosphor coatings.Sony VAIO VGN-CR240N/B Battery

Blocking out and coating

A trick of the eye is used to produce visually distinct neon display segments by blocking out parts of the tube with an opaque coating. One complete assembly may be composed of contiguous tube elements joined by glass welding to one another so that the same current passes through, for example, several letters joined end to end from cathode to cathode. Sony VAIO VGN-CR25G/N Battery

To the untrained eye, this looks like separate tubes, but the electrical splice is the plasma inside the crossover glass itself. The entire tube lights up, but the segments that the viewer is not supposed to see are covered with highly opaque special black or gray glass paint. This heat-resistant coating is either painted on or dipped. Sony VAIO VGN-CR290EAL Battery

Without blockout paint, the unintended visual connections would make the display appear confusing.

In most mass produced low-priced signs today, clear glass tubing is coated with translucent paint to produce colored light. In this way, several different colors can be produced inexpensively from a single glowing tube. Sony VAIO VGN-CR290EAN Battery

Over time, elevated temperatures, thermal cycling, or exposure to weather may cause the colored coating to flake off the glass or change its hue. A more expensive alternative is to use high-quality colored glass tubing, which retains a more stable appearance as it ages.Sony VAIO VGN-CR290EAP Battery

Applications

The light-emitting tubes form colored lines with which a text can be written or a picture drawn, including various decorations, especially in advertising andcommercial signage. By programming sequences of switching parts on and off, there are many possibilities for dynamic light patterns that form animated images.Sony VAIO VGN-CR290EAR Battery

Neon signs are increasingly replaced with LED signs due to the lower cost and longer operating life of LEDs. This trend seems likely to increase given the steady advance in LED luminosity and decreasing cost of high-intensity LEDs.

A neon lamp (also neon glow lamp) is a miniature gas discharge lamp that typically contains neon gas at a low pressure in a glass capsule. Sony VAIO VGN-CR290EAW Battery

Only a thin region adjacent to the electrodes glows in these lamps, which distinguishes them from the much longer and brighter neon tubes used for signage. The ter

m "neon lamp" is generally extended to lamps with similar design that operate with different gases.Sony VAIO VGN-CR29XN/B Battery

Neon glow lamps were very common in the displays of electronic instruments through the 1970s; the basic design of neon lamps is now incorporated in contemporary plasma displays.

Neon was discovered in 1898 by William Ramsey and Morris W. Travers. Sony VAIO VGN-CR305E/RC Battery

The characteristic, brilliant red color that is emitted by gaseous neon when excited electrically was noted immediately; Travers later wrote, "the blaze of crimson light from the tube told its own story and was a sight to dwell upon and never forget."

Neon's scarcity precluded its prompt application for electrical lighting along the lines of Moore tubes, which used electric discharges in nitrogen and which were commercialized in the early 1900s. Sony VAIO VGN-CR31S/D Battery

After 1902, Georges Claude's company, Air Liquide, was producing industrial quantities of neon as a byproduct of his air liquefaction business, and in December 1910 Claude demonstrated modern neon lighting based on a sealed tube of neon. In 1915 a U.S. patent was issued to Claude covering the design of the electrodes for neon tube lights;Sony VAIO VGN-CR323/W Battery

this patent became the basis for the monopoly held in the U.S. by his company, Claude Neon Lights, through the early 1930s.

Around 1917, Daniel McFarlan Moore, then working at the General Electric Company, developed the neon lamp, which has a very different design than the much larger neon tubes used for neon lighting. Sony VAIO VGN-CR33 Battery

The difference in design was sufficient that a U.S. patent was issued for the lamp in 1919. A Smithsonian Institution website notes, "These small, low power devices use a physical principle called coronal discharge. Moore mounted two electrodes close together in a bulb and added neon or argon gas.Sony VAIO VGN-CR382 Battery

The electrodes would glow brightly in red or blue, depending on the gas, and the lamps lasted for years. Since the electrodes could take almost any shape imaginable, a popular application has been fanciful decorative lamps. Glow lamps found practical use as indicators in instrument panels and in many home appliances until the widespread commercialisation of Light-Emitting Diodes (LEDs) in the 1970s." Sony VAIO VGN-CR490EBL Battery

Description

A small electric current, which may be AC or DC, is allowed through the tube, causing it to glow orange-red. The formulation of the gas is typically the classic Penning mixture, 99.5% neon and 0.5% argon, which has lower striking voltage than pure neon. Sony VAIO VGN-CR490EBN Battery

The applied voltage must initially reach the striking voltage before the lamp is visible. At the striking voltage, the lamp enters a breakdown mode and exhibits a glow discharge. Once lit, the voltage required to sustain the discharge is significantly (~30%) lower than the striking voltage. This is due to the organization of positive ions near the cathode.Sony VAIO VGN-CR490EBP Battery

When driven from a DC source, only the negatively charged electrode (cathode) will glow. When driven from an AC source, both electrodes will glow (each during alternate half cycles). These attributes make neon bulbs (with series resistors) a convenient low-cost voltage testers; Sony VAIO VGN-CR490EBR Battery

they determine whether a given voltage source is AC or DC, and if DC, the polarity of the points being tested. Neon lamps operate using a low current glow discharge. Higher power devices, such as mercury-vapor lamps or metal halide lamps use a higher current arc discharge.Sony VAIO VGN-CR490EBT Battery

Once the neon lamp has reached breakdown, it can support a large current flow. Because of this characteristic, electrical circuitry external to the neon lamp must limit the current through the circuit or else the current will rapidly increase until the lamp is destroyed. For indicator-sized lamps, a resistor typically limits the current.Sony VAIO VGN-CR490EBW Battery

Larger neon sign sized lamps often use a specially constructed high voltage transformer with high leakage inductance or other electrical ballast to limit the available current.

When the current through the lamp is lower than the current for the highest-current discharge path, the glow discharge may become unstable and not cover the entire surface of the electrodes.Sony VAIO VGN-CR50B/W Battery

This may be a sign of aging of the indicator bulb, and is exploited in the decorative "flicker flame" neon lamps. However, while too low a current causes flickering, too high a current increases the wear of the electrodes by stimulating sputtering, which coats the internal surface of the lamp with metal and causes it to darken.Sony VAIO VGN-CR51B/W Battery

The potential needed to strike the discharge is higher than what is needed to sustain the discharge. When there is not enough current, the glow forms around only part of the electrode surface. Convective currents make the glowing areas flow upwards, not unlike the discharge in a Jacob's ladder.Sony VAIO VGN-CR520E/J Battery

A photoionization effect can also be observed here, as the electrode area covered by the glow discharge can be increased by shining light at the lamp.

In comparison with incandescent light bulbs, neon lamps have much higher luminous efficacy.Sony VAIO VGN-CR52B/W Battery

Incandescence is heat-driven light emission, so a large portion of the electric energy put into an incandescent bulb is converted into heat. Non-incandescent light sources such as neon light bulbs,fluorescent light bulbs, and light emitting diodes are therefore much more energy efficient than normal incandescent light bulbs. Sony VAIO VGN-CR590EBL Battery

Green neon bulbs can produce up to 65 lumens per watt of power input, while white neon bulbs have an efficacy of around 50 lumens per watt. In contrast, a standard incandescent light bulb only produces around 13.5 lumens per watt.

Applications

Most small neon (indicator-sized) lamps, such as the common NE-2, break down at between 90 and 110 volts.Sony VAIO VGN-CR590EBN Battery

This feature enables their use as very simple voltage regulators or overvoltage protection devices. In the 1960s General Electric (GE), Signalite, and other firms made special extra-stable neon lamps for electronic uses. They even devised digital logic circuits, binary memories, andfrequency dividers using neon lamps.Sony VAIO VGN-CR590EBP Battery

Such circuits appeared in electronic organs of the 1950s, as well as some instrumentation. At least some of these lamps had a glow concentrated into a small spot on the cathode, which made them unsuited to use as indicators. These were sometimes called "circuit-component" lamps, the other variety being indicators. Sony VAIO VGN-CR590EBR Battery

A variant of the NE-2 type lamp, the NE-77, had three parallel wires (in a plane) instead of the usual two. It was also intended primarily to be a circuit component.

Small neon lamps are used as indicators in electronic equipment. Called "tuneons" in 1930s radio sets, they were fitted as tuning indicators, and would give a brighter glow as the station was tuned in correctly.Sony VAIO VGN-CR590EBT Battery

Larger lamps are used in neon signage. Neon lamps, due to their low current consumption, are used as nightlights. Because of their comparatively fast response time, in the early development of television neon lamps were used as the light source in many mechanical-scan TV displays. Sony VAIO VGN-CR590EBW Battery

They were also used for a variety of other purposes; since a neon lamp can act as a relaxation oscillator with an added resistor and capacitor, it can be used as a simple flashing lamp or audio oscillator. (See Pearson-Anson effect.)

Neon lamps with several shaped electrodes were used as alphanumerical displays known as Nixie tubes. Sony VAIO VGN-CR60B/L Battery

These have since been replaced by other display devices such aslight emitting diodes, vacuum fluorescent displays, and liquid crystal displays. Novelty glow lamps with shaped electrodes (such as flowers and leaves), often coated with phosphors, have been made for artistic purposes. Sony VAIO VGN-CR60B/P Battery

In some of these, the glow that surrounds an electrode is part of the design.

In AC-excited lamps, both electrodes produce light, but in a DC-excited lamp, only the negative electrode glows. Thus a neon lamp can be used to distinguish between AC and DC sources and to ascertain the polarity of DC sources.Sony VAIO VGN-CR60B/R Battery

Colour

Neon indicator lamps are normally orange, and are frequently used with a coloured filter over them to improve contrast and change their colour to red or a redder orange, or less often green.

They can also be filled with argon, krypton, or xenon rather than neon, or mixed with it. Sony VAIO VGN-CR61B/L Battery

While the electrical operating characteristics remain similar, the lamps light with a bluish glow (including some ultraviolet) rather than neon's characteristic reddish-orange glow. Ultraviolet radiation then can be used to excite a phosphor coating inside of the bulb and provide a wide range of various colors, including white.Sony VAIO VGN-CR61B/N Battery

A mixture of neon and krypton can be used for green glow, but nevertheless "green neon" lamps are more commonly phosphor-based.

Neon lighting is created by brightly glowing, electrified glass tubes or bulbs that contain rarefied neon or other gases.Sony VAIO VGN-CR61B/P Battery

Georges Claude, a French engineer and inventor, presented neon tube lighting in essentially its modern form at the Paris Motor Show from December 3–18, 1910.Claude, sometimes called "the Edison of France",had a near monopoly on the new technology, which became very popular for signage and displays in the period 1920-1940. Sony VAIO VGN-CR61B/R Battery

Neon lighting was an important cultural phenomenon in the United States in that era; by 1940, the downtowns of nearly every city in the US were bright with neon signage, and Times Square in New York City was known worldwide for its neon extravagances. There were 2000 shops nationwide designing and fabricating neon signs.Sony VAIO VGN-CR62B/L Battery

The popularity, intricacy, and scale of neon signage for advertising declined in the U.S. following the Second World War (1939–1945), but development continued vigorously in Japan, Iran, and some other countries. In recent decades architects and artists, in addition to sign designers, have again adopted neon tube lighting as a component in their works.Sony VAIO VGN-CR62B/N Battery

A second technology for neon lighting, the miniature neon glow lamp, was developed in 1917, about seven years after neon tube lighting. While neon tube lights are typically meters long, the lamps can be less than one centimeter in length and glow much more dimly than the tube lights. Sony VAIO VGN-CR62B/P Battery

Through the 1970s, neon glow lamps were widely used for displays in electronics, for small decorative lamps, and as electronic devices in of themselves. While these lamps are now antiques, the technology of the neon glow lamp developed into contemporary plasma displays and televisions.Sony VAIO VGN-CR62B/R Battery

Neon lighting is closely related to fluorescent lighting, which developed about 25 years after neon tube lighting. In fluorescent lights, the light emitted by rarefied gases within a tube is used exclusively to excite fluorescent materials that coat the tube, which then shine with their own colors that become the tube's visible, usually white, glow.Sony VAIO VGN-CR70B/W Battery

Fluorescent coatings and glasses are also an option for neon tube lighting, but are usually selected to obtain bright colors.

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