Neon An overview Contents

1 Overview 1 1.1 Neon ...... 1 1.1.1 History ...... 1 1.1.2 Isotopes ...... 2 1.1.3 Characteristics ...... 2 1.1.4 Occurrence ...... 3 1.1.5 Applications ...... 3 1.1.6 Compounds ...... 4 1.1.7 See also ...... 4 1.1.8 References ...... 4 1.1.9 External links ...... 5

2 Isotopes 6 2.1 Isotopes of neon ...... 6 2.1.1 Table ...... 6 2.1.2 References ...... 6

3 Miscellany 8 3.1 Neon sign ...... 8 3.1.1 History ...... 8 3.1.2 Fabrication ...... 9 3.1.3 Applications ...... 12 3.1.4 Images of neon signs ...... 13 3.1.5 See also ...... 13 3.1.6 References ...... 13 3.1.7 Further reading ...... 14 3.1.8 External links ...... 14 3.2 Neon lamp ...... 14 3.2.1 History ...... 14 3.2.2 Description ...... 15 3.2.3 Applications ...... 15 3.2.4 See also ...... 17 3.2.5 References ...... 17

i ii CONTENTS

4 Text and image sources, contributors, and licenses 19 4.1 Text ...... 19 4.2 Images ...... 20 4.3 Content license ...... 22 Chapter 1

Overview

1.1 Neon 1.1.1 History

This article is about the noble gas. For other uses, see Neon (disambiguation).

Neon is a chemical element with symbol Ne and atomic number 10. It is in group 18 (noble gases) of the periodic table.[7] Neon is a colorless, odorless, inert monatomic gas under standard conditions, with about two-thirds the density of air. It was discovered (along with krypton and xenon) in 1898 as one of the three residual rare inert ele- ments remaining in dry air, after nitrogen, oxygen, argon and carbon dioxide are removed. Neon was the second of these three rare gases to be discovered, and was imme- diately recognized as a new element from its bright red emission spectrum. The name neon is derived from the Greek word, νέον, neuter singular form of νέος [neos], meaning new. Neon is chemically inert and forms no un- charged chemical compounds. During cosmic nucleogenesis of the elements, large Neon gas-discharge lamps forming the symbol for neon “Ne” amounts of neon are built up from the alpha-capture fu- sion process in stars. Although neon is a very common Neon (Greek νέον (néon), neuter singular form of νέος element in the universe and solar system (it is fifth in meaning “new”), was discovered in 1898 by the British cosmic abundance after hydrogen, helium, oxygen and chemists Sir William Ramsay (1852–1916) and Morris carbon), it is very rare on Earth. It composes about 18.2 W. Travers (1872–1961) in London, England.[10] Neon ppm of air by volume (this is about the same as the molec- was discovered when Ramsay chilled a sample of air un- ular or mole fraction), and a smaller fraction in Earth’s til it became a liquid, then warmed the liquid and cap- crust. The reason for neon’s relative scarcity on Earth tured the gases as they boiled off. The gases nitrogen, and the inner (terrestrial) planets, is that neon forms no oxygen, and argon had been identified, but the remain- compounds to fix it to solids, and is highly volatile, there- ing gases were isolated in roughly their order of abun- fore escaping from the planetesimals under the warmth dance, in a six-week period beginning at the end of May of the newly ignited Sun in the early Solar System. Even 1898. First to be identified was krypton. The next, after the atmosphere of Jupiter is somewhat depleted of neon, krypton had been removed, was a gas which gave a bril- presumably for this reason. liant red light under spectroscopic discharge. This gas, identified in June, was named neon, the Greek analogue Neon gives a distinct reddish-orange glow when used in [11] either low-voltage neon glow lamps or in high-voltage of “novum”, (new), the name Ramsay’s son suggested. discharge tubes or neon advertising signs.[8][9] The red The characteristic brilliant red-orange color that is emit- emission line from neon is also responsible for the well ted by gaseous neon when excited electrically was noted known red light of helium–neon lasers. Neon is used in a immediately; Travers later wrote, “the blaze of crimson light from the tube told its own story and was a sight to few plasma tube and refrigerant applications but has few [12] other commercial uses. It is commercially extracted by dwell upon and never forget.” Finally, the same team the fractional distillation of liquid air. It is considerably discovered xenon by the same process, in June. more expensive than helium, since air is its only source. Neon’s scarcity precluded its prompt application for light-

1 2 CHAPTER 1. OVERVIEW

ing along the lines of Moore tubes, which used nitrogen and which were commercialized in the early 1900s. Af- ter 1902, Georges Claude's company, Air Liquide, was producing industrial quantities of neon as a byproduct of his air liquefaction business. In December 1910 Claude demonstrated modern neon lighting based on a sealed tube of neon. Claude tried briefly to get neon tubes to be used for indoor lighting, due to their intensity, but failed, as homeowners rejected neon light sources due to their color. Finally in 1912, Claude’s associate began selling neon discharge tubes as advertising signs, where they were instantly more successful as eye catchers. They were in- troduced to the U.S. in 1923, when two large neon signs were bought by a Los Angeles Packard car dealership. The glow and arresting red color made neon advertising completely different from the competition.[13] Neon played a role in the basic understanding of the na- ture of atoms in 1913, when J. J. Thomson, as part of his exploration into the composition of canal rays, chan- neled streams of neon ions through a magnetic and an electric field and measured their deflection by placing a photographic plate in their path. Thomson observed two separate patches of light on the photographic plate (see image), which suggested two different parabolas of de- flection. 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 evidence for isotopes of a stable element was provided in the first discovery of isotopes of stable atoms. It was 1913 by experiments on neon plasma. In the bottom right corner of J. J. Thomson's photographic plate are the separate impact made by using a crude version of an instrument we now marks for the two isotopes neon-20 and neon-22. term as a mass spectrometer.

1.1.2 Isotopes ous natural terrestrial neutron sources. In addition, isotopic analysis of exposed terrestrial rocks Main article: Isotopes of neon has demonstrated the cosmogenic (cosmic ray) produc- Neon is the second lightest inert gas. Neon has three tion of 21Ne. This isotope is generated by spallation reac- stable isotopes: 20Ne (90.48%), 21Ne (0.27%) and 22Ne tions on magnesium, sodium, silicon, and aluminium. By (9.25%). 21Ne and 22Ne are partly primordial and partly analyzing all three isotopes, the cosmogenic component nucleogenic (i.e., made by nuclear reactions of other nu- can be resolved from magmatic neon and nucleogenic clides with neutrons or other particles in the environment) neon. This suggests that neon will be a useful tool in and their variations in natural abundance are well under- determining cosmic exposure ages of surface rocks and stood. In contrast, 20Ne (the chief primordial isotope meteorites.[16] made in stellar nucleosynthesis) is not known to be nu- Similar to xenon, neon content observed in samples of cleogenic or radiogenic (save for cluster decay produc- volcanic gases is enriched in 20Ne, as well as nucleogenic tion, which is thought to produce only a small amount). 21Ne, relative to 22Ne content. The neon isotopic con- 20 The causes of the variation of Ne in the Earth have thus tent of these mantle-derived samples represents a non- [14] been hotly debated. atmospheric source of neon. The 20Ne-enriched compo- The principal nuclear reactions which generate nucle- nents are attributed to exotic primordial rare gas compo- ogenic neon isotopes start from 24Mg and 25Mg, which nents in the Earth, possibly representing solar neon. El- produce 21Ne and 22Ne, respectively, after neutron cap- evated 20Ne abundances are found in diamonds, further ture and immediate emission of an alpha particle. The suggesting a solar neon reservoir in the Earth.[17] neutrons that produce the reactions are mostly produced by secondary spallation reactions from alpha particles, in turn derived from uranium-series decay chains. The net 1.1.3 Characteristics result yields a trend towards lower 20Ne/22Ne and higher 21Ne/22Ne ratios observed in uranium-rich rocks such as Neon is the second-lightest noble gas, after helium. It granites.[15] Neon-21 may also be produced in a nucle- glows reddish-orange in a vacuum discharge tube. Also, ogenic reaction, when 20Ne absorbs a neutron from vari- neon has the narrowest liquid range of any element: from 1.1. NEON 3

ter hydrogen, helium, oxygen, and carbon (see chemical element). 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 condens- ing gas and dust clouds which resulted in the formation of smaller and warmer solid planets like Earth. 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.[25] Neon’s abundance in the universe is about 1 part in 750 Neon discharge tube and in the Sun and presumably in the proto-solar system nebula, about 1 part in 600. The Galileo spacecraft at- 24.55 K to 27.05 K (−248.45 °C to −245.95 °C, or mospheric entry probe found that even in the upper at- −415.21 °F to −410.71 °F). It has over 40 times the re- mosphere of Jupiter, the abundance of neon is reduced frigerating capacity of liquid helium and three times that (depleted) by about a factor of 10, to a level of 1 part of liquid hydrogen (on a per unit volume basis).[1] In in 6,000 by mass. This may indicate that even the ice- most applications it is a less expensive refrigerant than planetesimals which brought neon into Jupiter from the helium.[18][19] outer solar system, 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).[26] Neon is rare on Earth, found in the Earth’s atmosphere at 1 part in 55,000, or 18.2 ppm by volume (this is about the same as the molecule or mole fraction), or 1 part Spectrum of neon with ultraviolet (at left) and infrared (at right) in 79,000 of air by mass. It comprises a smaller frac- lines shown in white tion in the crust. It is industrially produced by cryogenic fractional distillation of liquefied air.[1] Neon plasma has the most intense light discharge at nor- mal voltages and currents of all the noble gases. The av- erage color of this light to the human eye is red-orange 1.1.5 Applications 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.[20] Two quite different kinds of neon lighting are in common use. Neon glow lamps are generally tiny, with most oper- ating at about 100–250 volts.[21] They have been widely used as power-on indicators and in circuit-testing equip- ment, but light-emitting diodes (LEDs) now dominate in such applications. These simple neon devices were the forerunners of plasma displays and plasma televi- sion screens.[22][23] Neon signs typically operate at much higher voltages (2–15 kilovolts), and the luminous tubes are commonly meters long.[24] The glass tubing is often formed into shapes and letters for signage as well as ar- chitectural and artistic applications.

Neon signs may use neon along with other noble gases 1.1.4 Occurrence Neon is often used in signs and produces an unmistakable Stable isotopes of neon are produced in stars. 20Ne is bright reddish-orange light. Although still referred to as created in fusing helium and oxygen in the alpha process, “neon”, other colors are generated with different noble which requires temperatures above 100 megakelvins and gases or by varied colors of fluorescent lighting. masses greater than 3 solar masses. Neon is used in vacuum tubes, high-voltage indicators, Neon is abundant on a universal scale; it is the fifth most lightning arrestors, wave meter tubes, television tubes, abundant chemical element in the universe by mass, af- and helium–neon lasers. Liquefied neon is commercially 4 CHAPTER 1. OVERVIEW used as a cryogenic refrigerant in applications not requir- [8] Coyle, Harold P. (2001). Project STAR: The Universe in ing the lower temperature range attainable with more ex- Your Hands. Kendall Hunt. p. 464. ISBN 978-0-7872- treme liquid helium refrigeration. 6763-6.

Both neon gas and liquid neon are relatively expensive – [9] Kohmoto, Kohtaro (1999). “Phosphors for lamps”. In for small quantities, the price of liquid neon can be more Shionoya, Shigeo; Yen, William M. Phosphor Handbook. than 55 times that of liquid helium. The driver for neon’s CRC Press. p. 940. ISBN 978-0-8493-7560-6. expense is the rarity of neon, which unlike helium, can only be obtained from air. [10] Ramsay, William, Travers, Morris W. (1898). “On the Companions of Argon”. Proceedings of the Royal Society The triple point temperature of neon (24.5561 K) is of London 63 (1): 437–440. doi:10.1098/rspl.1898.0057. a defining fixed point in the International Temperature Scale of 1990.[2] [11] “Neon: History”. Softciências. Retrieved 2007-02-27.

[12] Weeks, Mary Elvira (2003). Discovery of the Elements: 1.1.6 Compounds Third Edition (reprint). Kessinger Publishing. p. 287. ISBN 978-0-7661-3872-8.

Neon is the first p-block noble gas. Neon is generally con- [13] Mangum, Aja (December 8, 2007). “Neon: A Brief His- sidered to be inert. No true neutral compounds of neon tory”. New York Magazine. Retrieved 2008-05-20. are known. However, the ions Ne+, (NeAr)+, (NeH)+, and (HeNe+) have been observed from optical and mass [14] Dickin, Alan P (2005). “Neon”. Radiogenic isotope geol- spectrometric studies, and there are some unverified re- ogy. p. 303. ISBN 978-0-521-82316-6. ports of an unstable hydrate.[1] [15] Resources on Isotopes. Periodic Table—Neon. expla- nation of the nucleogenic sources of Ne-21 and Ne-22. 1.1.7 See also USGS.gov [16] “Neon: Isotopes”. Softciências. Retrieved 2007-02-27. • Expansion ratio [17] Anderson, Don L. “Helium, Neon & Argon”. Mantle- • Neon sign plumes.org. Retrieved 2006-07-02.

• Neon lamp [18] “NASSMC: News Bulletin”. December 30, 2005. Re- trieved 2007-03-05. 1.1.8 References [19] Mukhopadhyay, Mamata (2012). Fundamentals of Cryo- genic Engineering. p. 195. ISBN 9788120330573. [1] Hammond, C.R. (2000). The Elements, in Handbook of Chemistry and Physics 81st edition. CRC press. p. 19. [20] “Plasma”. Retrieved 2007-03-05. ISBN 0849304814. [21] Baumann, Edward (1966). Applications of Neon Lamps [2] Preston-Thomas, H. (1990). “The International Tem- and Gas Discharge Tubes. Carlton Press. perature Scale of 1990 (ITS-90)". Metrologia 27: 3– [22] Myers, Robert L. (2002). Display interfaces: fundamen- 10. Bibcode:1990Metro..27....3P. doi:10.1088/0026- tals and standards. John Wiley and Sons. pp. 69–71. 1394/27/1/002. ISBN 978-0-471-49946-6. Plasma displays are closely re- [3] Haynes, William M., ed. (2011). CRC Handbook of lated to the simple neon lamp. Chemistry and Physics (92nd ed.). Boca Raton, FL: CRC Press. p. 4.122. ISBN 1439855110. [23] Weber, Larry F. (April 2006). “History of the plasma display panel”. IEEE Transactions on Plasma Sci- [4] Magnetic susceptibility of the elements and inorganic ence 34 (2): 268–278. Bibcode:2006ITPS...34..268W. compounds, in Lide, D. R., ed. (2005). CRC Handbook doi:10.1109/TPS.2006.872440. Paid access. of Chemistry and Physics (86th ed.). Boca Raton (FL): CRC Press. ISBN 0-8493-0486-5. [24] “ANSI Luminous Tube Footage Chart”. American Na- tional Standards Institute (ANSI). Retrieved 2010-12-10. [5] Ramsay, William, Travers, Morris W. (1898). “On the Reproduction of a chart in the catalog of a lighting com- Companions of Argon”. Proceedings of the Royal Society pany in Toronto; the original ANSI specification is not of London 63 (1): 437–440. doi:10.1098/rspl.1898.0057. given.

[6] “Neon: History”. Softciências. Retrieved 2007-02-27. [25] Gallagher, R.; Ingram, P. (2001-07-19). Chemistry for Higher Tier. University Press. p. 282. ISBN 978-0-19- [7] Group 18 refers to the modern numbering of the periodic 914817-2. table. Older numberings described the rare gases as Group 0 or Group VIIIA (sometimes shortened to 8). See also [26] Morse, David (January 26, 1996). “Galileo Probe Science Group (periodic table). Result”. Galileo Project. Retrieved 2007-02-27. 1.1. NEON 5

1.1.9 External links

• Neon at The Periodic Table of Videos (University of Nottingham)

• WebElements.com – Neon. • It’s Elemental – Neon

• USGS Periodic Table – Neon • Atomic Spectrum of Neon

• Neon Museum, Las Vegas Chapter 2

Isotopes

2.1 Isotopes of neon • Commercially available materials may have been subjected to an undisclosed or inadvertent isotopic Neon (Ne) possesses three stable isotopes, 20Ne, 21Ne, fractionation. Substantial deviations from the given and 22Ne. In addition, 16 radioactive isotopes have been mass and composition can occur. discovered ranging from 16Ne to 34Ne, all short-lived. • Values marked # are not purely derived from ex- The longest-lived is 24Ne with a half-life of 3.38 min- perimental data, but at least partly from systematic utes. All others are under a minute, most under a second. trends. Spins with weak assignment arguments are The least stable is 16Ne with a half-life of 9×10−21 s. See enclosed in parentheses. isotopes of carbon for notes about the measurement. Standard atomic mass: 20.1797(6) u • Uncertainties are given in concise form in parenthe- ses after the corresponding last digits. Uncertainty values denote one standard deviation, except iso- topic composition and standard atomic mass from IUPAC which use expanded uncertainties.

2.1.2 References

• Isotope masses from:

• G. Audi, A. H. Wapstra, C. Thibault, J. Blachot and O. Bersillon (2003). “The NUBASE evaluation of nuclear and de- A chart showing the abundances of the naturally-occurring iso- cay properties”. Nuclear Physics A 729: topes of neon. 3–128. Bibcode:2003NuPhA.729....3A. doi:10.1016/j.nuclphysa.2003.11.001. • 2.1.1 Table Isotopic compositions and standard atomic masses from: [1] Bold for stable isotopes • J. R. de Laeter, J. K. Böhlke, P. De Bièvre, [2] Has 2 halo protons H. Hidaka, H. S. Peiser, K. J. R. Rosman and P. D. P. Taylor (2003). “Atomic weights of Notes the elements. Review 2000 (IUPAC Technical Report)". Pure and Applied Chemistry 75 (6): • The isotopic composition refers to that in air. 683–800. doi:10.1351/pac200375060683. • • The precision of the isotope abundances and atomic M. E. Wieser (2006). “Atomic weights of the mass is limited through variations. The given ranges elements 2005 (IUPAC Technical Report)". should be applicable to any normal terrestrial mate- Pure and Applied Chemistry 78 (11): 2051– rial. 2066. doi:10.1351/pac200678112051. Lay summary. • Geologically exceptional samples are known in which the isotopic composition lies outside the re- • Half-life, spin, and isomer data selected from the ported range. The uncertainty in the atomic mass following sources. See editing notes on this article’s may exceed the stated value for such specimens. talk page.

6 2.1. ISOTOPES OF NEON 7

• G. Audi, A. H. Wapstra, C. Thibault, J. Blachot and O. Bersillon (2003). “The NUBASE evaluation of nuclear and de- cay properties”. Nuclear Physics A 729: 3–128. Bibcode:2003NuPhA.729....3A. doi:10.1016/j.nuclphysa.2003.11.001. • National Nuclear Data Center. “NuDat 2.1 database”. Brookhaven National Laboratory. Retrieved September 2005. • N. E. Holden (2004). “Table of the Isotopes”. In D. R. Lide. CRC Handbook of Chemistry and Physics (85th ed.). CRC Press. Section 11. ISBN 978-0-8493-0485-9.

[1] http://www.nucleonica.net/unc.aspx

[2] http://physicsworld.com/cws/article/news/2762 Chapter 3

Miscellany

3.1 Neon sign signage, neon lighting is now used frequently by artists and architects,[2][4][5] and (in a modified form) in plasma [6][7] See also: Neon lighting display panels and televisions. The signage industry In the signage industry, neon signs are electric signs has declined in the past several decades, and cities are now concerned with preserving and restoring their an- tique neon signs.

3.1.1 History

Neon sign

1937 neon marquee sign for a theater in Auburn, California, as rebuilt in 2006. The large letters on the tower are illuminated in a timed sequence that repeats, “S”, “ST”, ..., “STATE”, off. 1930s neon sign dealer, Anson Brown Building, Ann Arbor, Michigan lighted by long luminous gas-discharge tubes that con- tain rarefied neon or other gases. They are the most com- The neon sign is an evolution of the earlier Geissler tube, mon use for neon lighting, which was first demonstrated which is an electrified glass tube containing a “rarefied” in a modern form in December 1910 by Georges Claude gas (the gas pressure in the tube is well below atmospheric at the Paris Motor Show.[1] While they are used world- pressure). When a voltage is applied to electrodes in- wide, neon signs were extremely popular in the United serted through the glass, an electrical glow discharge re- States from about 1920–1960. The installations in Times sults. Geissler tubes were quite popular in the late 1800s, Square were famed, and there were nearly 2000 small and the different colors they emitted were characteris- shops producing neon signs by 1940.[2][3] In addition to tics of the gases within. They were, however, unsuitable

8 3.1. NEON SIGN 9

for general lighting; the pressure of the gas inside typ- 3.1.2 Fabrication ically declined in use. The direct predecessor of neon tube lighting was the Moore tube, which used nitrogen or carbon dioxide as the luminous gas and a patented mech- anism for maintaining pressure; Moore tubes were sold for commercial lighting for a number of years in the early 1900s.[8][9] The discovery of neon in 1898 included the observation of a brilliant red glow in Geissler tubes.[10] Immediately following neon’s discovery, neon tubes were used as sci- entific instruments and novelties.[11] 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;[12] in any event, the scarcity of neon would have precluded the de- velopment of a lighting product. However, after 1902, Georges Claude's company in France, Air Liquide, be- gan producing industrial quantities of neon, essentially as a byproduct of their air liquefaction business.[9] From December 3–18, 1910, Claude demonstrated two 12- metre (39 ft) long bright red neon tubes at the Paris Mo- tor Show.[1][13] This demonstration lit a peristyle of the Grand Palais (a large exhibition hall).[14] Claude’s asso- ciate, Jacques Fonseque, realized the possibilities for a business based on signage and advertising. By 1913 a large sign for the vermouth Cinzano illuminated the night sky in Paris, and by 1919 the entrance to the Paris Opera An enormous number of colors can be created by combinations [2] was adorned with neon tube lighting. Over the next sev- of different gases and fluorescent coatings in the tube. eral years, patents were granted to Claude for two inno- vations still used today: a “bombardment” technique to Neon tube signs[16][17][18][19] are produced by the craft of remove impurities from the working gas of a sealed sign, bending glass tubing into shapes. A worker skilled in this and a design for the internal electrodes of the sign that craft is known as a glass bender, neon bender or tube ben- [9] prevented their degradation by sputtering. der. The neon tube is made out of 4-5' straight sticks of In 1923, Georges Claude and his French company Claude hollow glass sold by sign suppliers to neon shops world- Neon introduced neon gas signs to the United States by wide where they are manually assembled into individual selling two to a Packard car dealership in Los Ange- custom designed and fabricated lamps. There are many les. Earle C. Anthony purchased the two signs reading dozens of colors available, determined by the type of glass “Packard” for $1,250 apiece.[1] Neon lighting quickly be- tubing and the composition of the gas filling. came a popular fixture in outdoor advertising. Visible Tubing in external diameters ranging from about 8–15 even in daylight, people would stop and stare at the first mm with a 1 mm wall thickness is most commonly used, [15] neon signs for hours, dubbed “liquid fire.” although 6 mm tubing is now commercially available in The next major technological innovation in neon lighting colored glass tubes. The tube is heated in sections us- and signs was the development of fluorescent tube coat- ing several types of burners that are selected according ings. Jacques Risler received a French patent in 1926 for to the amount of glass to be heated for each bend. These these.[3] Neon signs that use an argon/mercury gas mix- burners include ribbon, cannon, or crossfires, as well as a ture emit a good deal of ultraviolet light. When this light variety of gas torches. Ribbon burners are strips of fire is absorbed by a fluorescent coating, preferably inside the that make the gradual bends while crossfires, when used, tube, the coating (called a “phosphor”) glows with its own make the sharp bends. color. While only a few colors were initially available to The interior of the tubes may be coated with a thin phos- sign designers, after the Second World War (1939–1945) phorescent powder coating, affixed to the interior wall of phosphor materials were researched intensively for use in the tube by a binding material. The tube is filled with a color televisions. About two dozen colors were available purified gas mixture, and the gas ionized by a high volt- to neon sign designers in the 1960s, and today there are age applied between the ends of the sealed tube through [5] nearly 100 available colors. 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. Different phosphor- coated tubing sections may be butt welded together using 10 CHAPTER 3. MISCELLANY glass working torches to form a single tube of varying col- voltage ion implantation into the interior glass walls of ors, for effects such as a sign where each letter displays a the tubes which depletes the gas, and eventually causes different color letter within a single word, such as shown the tube resistance to rise to a level that it can no longer in the sign in the photo above right. light at the rated voltage, but this may take well over 50 “Neon” is used to denote the general type of lamp, but years if the tube is properly processed during bombard- neon gas is only one of the types of tube gases principally ment and gas back-filling. used in commercial application. Pure neon gas is used The actual cause of 80% of neon sign failures is the to produce only about a third of the colors. The great- burnout of the high voltage electrical wires connecting the est number of colors is produced by filling with another tubes inside of metal conduits. A very common type of inert gas, argon, and a drop of mercury (Hg) which is neon sign is made from a formed metal box having a col- added to the tube immediately after purification. When ored translucent face, called “channel lettering”. Newer the tube is ionized by electrification, the mercury evap- channel letter signs are being replaced by high brightness orates into mercury vapor, which fills the tube and pro- LEDs. duces strong ultraviolet light. The ultraviolet light thus This long lifetime has created a practical market for neon produced excites the various phosphor coatings designed use for interior architectural cove lighting in a wide vari- to produce different colors. Even though this class of ety of uses including homes, where the tube can be bent neon tubes use no neon at all, they are still denoted to any shape, fitted in a small space, and can do so without as “neon.” Mercury-bearing lamps are a type of cold- requiring tube replacement for a decade or more. cathode fluorescent lamps. Each type of neon tubing produces two completely dif- ferent possible colors, one with neon gas and the other Tube bending with argon/mercury. Some “neon” tubes are made with- out phosphor coatings for some of the colors. Clear tub- ing filled with neon gas produces the ubiquitous yellow- A section of the glass is heated until it is malleable; then ish orange color with the interior plasma column clearly it is bent into shape and aligned to a neon sign pattern visible, and is the cheapest and simplest tube to make. paper containing the graphics or lettering that the final Traditional neon glasses in America over 20 years old product will ultimately conform to. This is where the real are lead glass that are easy to soften in gas fires, but re- art of neon comes in, that takes some artisans from a year cent environmental and health concerns of the workers up to several years of practice to master. A tube ben- has prompted manufacturers to seek more environmen- der corks off the hollow tube before heating and holds a tally safe special soft glass formulas. One of the vexing latex rubber blow hose at the other end, through which problems avoided this way is lead glass’ tendency to burn he gently presses a small amount of air to keep the tube into a black spot emitting lead fumes in a bending flame diameter constant as it is bending. The trick of bending too rich in the fuel/oxygen mixture. Another traditional is to bend one small section or bend at a time, heating line of glasses was colored soda lime glasses coming in one part of the tubing so that it is soft, without heating a myriad of glass color choices, which produce the high- some other part of the tube as well, which would make est quality, most hypnotically vibrant and saturated hues. the bend uncontrollable. A bend, once the glass is heated, Still more color choices are afforded in either coating, or must be brought to the pattern and fitted rapidly before not coating, these colored glasses with the various avail- the glass hardens again because it is difficult to reheat able exotic phosphors. once completely cooled without risking breakage. It is frequently necessary to skip one or more bends and come back to it later, by measuring carefully along the length of Long lifetime the tube. One tube letter may contain 7-10 small bends, and mistakes are not easily corrected without going back It is the wide range of colors and the ability to make a and starting all over again. If more tubing is required, tube that can last for years if not decades without replace- another piece is welded onto it, or the parts can be all ment, that makes this an art. Since these tubes require so welded onto each other at the final step. The finished much custom labor, they would have very little economic tube must be absolutely vacuum tight to operate, and it viability if they did not have such a long lifetime when must be vacuum clean inside. Once the tube is filled with well processed. The intensity of neon light produced in- mercury, if any mistake is made after that, the entire tube creases slowly as the tube diameter grows smaller, that is, has to, or should be, started over anew, because breathing the intensity varies inversely with the square root of the heated mercury impregnated glass and phosphor causes interior diameter of the tubing, and the resistance of the long term heavy metal poisoning in neon workers. Sticks tube increases as the tubing diameter decreases accord- of tubing are joined until the tube reaches an impractical ingly, because tube ionization is greatest at the center of size, and several tubes are joined in series with the high the tube, and the ions migrate to and are recaptured and voltage neon transformer. Extreme ends of the electrical neutralized at the tube walls. The greatest cause of neon circuit must be isolated from each other to prevent tube tube failure is the gradual absorption of neon gas by high puncture and buzzing from corona effect. 3.1. NEON SIGN 11

Bombardment which would quickly burn the metal cathodes and mer- cury droplets (if pumped with argon/mercury) and ox- idize the interior gases and cause immediate tube fail- A cold cathode electrode is melted (or welded) to each ure. The more thorough the purification of the tube is, end of the tube as it is finished. The electrodes are also the longer lasting and stable the tube will be in actual op- traditionally lead glass and contain a small metal shell eration. Once these gases and impurities are liberated with two wires protruding through the glass to which the under pre-filling bombardment into the tube interior they sign wiring will later be attached. All welds and seals are quickly evacuated by the pump. must be perfectly leak-proof to high vacuum before pro- ceeding further. While still attached to the manifold, the tube is allowed to cool while pumping down to the lowest pressure the The tube is attached to a manifold which is itself attached system can achieve. It is then filled to a low pressure to a high-quality vacuum pump. The tube is then evacu- of a few torrs (millimeters of mercury) with one of the ated of air until it reaches near-vacuum. During evac- noble gases, or a mixture of them, and sometimes a small uation, a high current is forced through the tube via the amount of mercury. This gas fill pressure represents wires protruding from each electrode (in a process known roughly 1/100th of the pressure of the atmosphere. The as “bombarding”). This current and voltage is far above required pressure depends on the gas used and the di- the level that occurs in final operation of the tube. The ameter of the tube, with optimal values ranging from 6 current depends on the specific electrodes used and the Torr (0.8 kPa) (for a long 20 mm tube filled with ar- diameter of the tube, but is typically in the 45 mA to 80 gon/mercury) to 27 Torr (3.6 kPa) (for a short 8 mm mA range, at an applied voltage usually between 5,000- diameter tube filled with pure neon). Neon or argon 36,000 V DC. The bombarding transformer acts as an are the most common gases used; krypton, xenon, and adjustable constant current source, and the voltage pro- helium are used by artists for special purposes but are duced depends on the length and pressure of the tube. not used alone in normal signs. A premixed combina- Typically the operator will maintain the pressure as high tion of argon and helium is often used in lieu of pure as the bombarder will allow to ensure maximum power argon when a tube is to be installed in a cold climate, dissipation and heating. since the helium increases voltage drop (and thus power This very high power dissipation in the tube heats the dissipation), warming the tube to operating temperature glass walls to a temperature of several hundred degrees faster. Neon glows bright red or reddish orange when lit. Celsius, and any dirt and impurities within are drawn off When argon or argon/helium is used, a tiny droplet of in the gasified form by the vacuum pump. The greatest mercury is added. Argon by itself is very dim pale laven- impurities that are driven off this way are the gases that der when lit, but the droplet of mercury fills the tube with coat the inside wall of the tubing by adsorption, mainly mercury vapor when sealed, which then emits ultraviolet oxygen, carbon dioxide, and especially water vapor. The light upon electrification. This ultraviolet emission allows current also heats the electrode metal to over 600oC, pro- finished argon/mercury tubes to glow with a variety of ducing a bright orange incandescent color. The cathodes bright colors when the tube has been coated on the inte- are prefabricated hollow metal shells with a small open- rior with ultraviolet-sensitive phosphors after being bent ing (sometimes a ceramic donut aperture) which contains into shape. in the interior surface of the shell a light dusting of a cold cathode low work function powder (usually a powder ce- ramic molar eutectic point mixture including BaCO2), combined with other alkaline earth oxides, which reduces Heat processed neon tubes to BaO2 when heated to about 500 degrees F, and reduces the work function of the electrode for cathodic emission. Barium Oxide has a work function of roughly 2 whereas An alternative way of processing finished neon tubes has tungsten at room temperature has a work function expo- also been used. Because the only purpose of bombard- nentially 100 times more, or 4.0. This represents the cath- ment by electrical means is to purify the interior of tubes, ode drop or electron energy required to remove electrons it is also possible to produce a tube by heating the tube from the surface of the cathode. This avoids the neces- externally either with a torch or with an oven, while heat- sity of using a hot wire thermoelectric cathode such as ing the electrode with a radio frequency induction heat- is used in conventional fluorescent lamps. And for that ing (RFIH) coil. While this is less productive, it creates a reason, neon tubes are extremely long lived when prop- cleaner custom tube with significantly less cathode dam- erly processed, in contrast to fluorescent tubing, because age, longer life and brilliance, and can produce tubes of there is no wire filament as there is in a fluorsecent tube to very small sizes and diameters, down to 6mm OD. The burn out like a common light bulb. The principal purpose tube is heated thoroughly under high vacuum without ex- of doing this is to purify the interior of the tube before ternal electrical application, until the outgassed gases can the tube is sealed off so that when it is operated, these be seen to have been totally depleted and the pressure gases and impurities are not driven off and released by drops to a high vacuum again. Then the tube is filled, the plasma and the heat generated into the sealed tube, sealed and the mercury dropped and shaken. 12 CHAPTER 3. MISCELLANY

Electrical wiring

The finished glass pieces are illuminated by either a neon sign transformer or a switched-mode power supply run- ning at voltages ranging between 3-15 kV and currents between 20 and 120 mA. These power supplies operate as constant-current sources (a high voltage supply with a very high internal impedance), since the tube has a neg- ative 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. The standard traditional neon transformer, a magnetic shunt transformer, is a special non-linear type designed to Club Prima Donna animated neon sign in Reno, Nevada, 1955. keep the voltage across the tube raised to whatever level is necessary to produce the fixed current needed. The volt- arate tubes, but the electrical splice is the plasma inside age drop of a tube is proportional to length and so the the crossover glass itself. The entire tube lights up, but maximum voltage and length of tubing fed from a given the segments that the viewer is not supposed to see are transformer is limited. covered with highly opaque special black or gray glass Compact high frequency inverter-converter transformers paint. This heat-resistant coating is either painted on or developed in the early 1990s are used, especially when dipped. Without blockout paint, the unintended visual low Radio Frequency Interference (RFI) is needed, such connections would make the display appear confusing. as in locations near high-fidelity sound equipment. At the In most mass-produced low-priced signs today, clear glass typical frequency of these solid state transformers, the tubing is coated with translucent paint to produce col- plasma electron-ion recombination time is too long to ex- ored light. In this way, several different colors can be tinguish and reignite the plasma at each cycle, unlike the produced inexpensively from a single glowing tube. Over case at power line frequency. The plasma does not broad- time, elevated temperatures, thermal cycling, or exposure cast high frequency switching noise and remains ionized to weather may cause the colored coating to flake off the continually, becoming radio noise free. glass or change its hue. A more expensive alternative is The most common current rating is 30 mA for general to use high-quality colored glass tubing, which retains a use, with 60 mA used for high-brightness applications more stable appearance as it ages. like channel letters or architectural lighting. 120 mA sources are occasionally seen in illuminating applications, but are uncommon since special electrodes are required 3.1.3 Applications to withstand the current, and an accidental shock from a 120 mA transformer is much more likely to be fatal than Light-emitting tubes form colored lines with which a text from the lower current supplies. can be written or a picture drawn, including various deco- The efficiency of neon lighting ranges between that of or- rations, especially in advertising and commercial signage. dinary incandescent lights and that of fluorescent lamps, By programming sequences of switching parts on and off, depending on color. On a per-watt basis, incandescents there are many possibilities for dynamic light patterns that produce 10 to 20 lumens, while fluorescents produce form animated images. 50 to 100 lumens. Neon light efficiency ranges from In some applications, neon tubes are increasingly being 10 lumens per watt for red, up to 60 lumens for green replaced with LEDs, given the steady advance in LED lu- and blue when these colors result from internal phosphor minosity and decreasing cost of high-intensity LEDs.[21] coatings.[20] However, proponents of neon technology maintain that they still have significant advantages over LEDs.[22] Blocking out and coating Neon illumination is valuable to invoke 1940s or 1950s nostalgia in marketing and in historic restoration of ar- A trick of the eye is used to produce visually distinct neon chitectural landmarks from the neon era. Architecture in display segments by blocking out parts of the tube with the streamline moderne era often deployed neon to ac- an opaque coating. One complete assembly may be com- cent structural pigmented glass built into the façade of a posed of contiguous tube elements joined by glass weld- 1930s or 1940s structure; many of these buildings now ing to one another so that the same current passes through, qualify for inclusion on historic registers such as the US for example, several letters joined end to end from cath- National Register of Historic Places if their historic in- ode to cathode. To the untrained eye, this looks like sep- tegrity is faithfully maintained.[23] 3.1. NEON SIGN 13

3.1.4 Images of neon signs [6] Myers, Robert L. (2002). Display interfaces: fundamen- tals and standards. John Wiley and Sons. pp. 69–71. • Helium ISBN 978-0-471-49946-6. Plasma displays are closely re- lated to the simple neon lamp. • Neon [7] Weber, Larry F. (April 2006). “History of the plasma • Argon display panel”. IEEE Transactions on Plasma Sci- ence 34 (2): 268–278. Bibcode:2006ITPS...34..268W. • Krypton doi:10.1109/TPS.2006.872440. Paid access.

• Xenon [8] “Lamp Inventors 1880-1940: Moore Lamp”. The Smith- sonian Institution. • A deteriorated, 1950s era sign typical of Googie ar- chitecture; “Ships” was a chain of coffee shops in [9] Claude, Georges (November 1913). “The Development Los Angeles.[1] of Neon Tubes”. The Engineering Magazine: 271–274.

• Original Whitey’s Restaurant “EAT” sign in Arling- [10] Weeks, Mary Elvira (2003). Discovery of the Elements: ton, VA Third Edition (reprint). Kessinger Publishing. p. 287. ISBN 978-0-7661-3872-8.

1. ^ Hess, Alan (2004). Googie redux: ultramodern [11] Fleming, J. A. (October 1904). “The Propagation of Elec- roadside architecture. Chronicle Books. p. 115. tric Waves along Spiral Wires, and on an Appliance for ISBN 978-0-8118-4272-3. Measuring the Length of Waves Used in Wireless Teleg- raphy”. Philosophical Magazine and Journal of Science: Sixth Series 8 (46): 417. Fleming used a tube of neon, 3.1.5 See also without electrodes, to explore the amplitudes of radiofre- quency waves by examining the intensity of the tube’s light • Neon lighting emission. He had obtained his neon directly from its dis- coverer, Ramsey. • Gas discharge lamp [12] Howard, John K. (February 2009). “OSA’s First Four • Crackle tube Presidents”. Optics & Photonics News. Retrieved 2009- 02-21. • Plasma globe [13] The dates of the show are listed at “Chronik 1901 - • Pundit Light 1910/en”. Mercedes Benz.

• Neon message board [14] Testelin, Xavier. “Reportage - Il était une fois le néon No. 402”. Retrieved 2010-12-06. Claude’s 1910 demonstra- • Westinghouse Sign tion of neon lighting lit the peristyle of the Grand Palais in Paris; this webpage includes a contemporary photograph • Timeline of lighting technology that gives an impression of it. It is part of an extensive selection of images of neon lighting; see “Reportage - Il était une fois le néon”. 3.1.6 References [15] These anecdotes and the phrase “liquid fire” are often used [1] van Dulken, Stephen (2002). Inventing the 20th century: in references discussing the first neon tube lights in Los 100 inventions that shaped the world : from the airplane Angeles, but the primary source is not provided. One ex- to the zipper. New York University Press. p. 42. ISBN ample of a typical, tertiary reference is Bellis, Mary. “The 978-0-8147-8812-7. History of Neon Signs: Georges Claude and Liquid Fire”. about.com. [2] Stern, Rudi (1988). The New Let There Be Neon. H. N. Abrams. pp. 16–33. ISBN 978-0-8109-1299-1. [16] Strattman, Wayne (1997). Neon Techniques: Handbook of Neon Sign and Cold-Cathode Lighting, 4th edition. ST [3] Bright, Jr., Arthur A. (1949). The Electric-Lamp Industry. Media Group International. ISBN 978-0-944094-27-3. MacMillan. Pages 221-223 describe Moore tubes. Pages 369-374 describe neon tube lighting. Page 385 discusses [17] Signs of the Times http://www.stmediagroup.com/index. Risler’s contributions to fluorescent coatings in the 1920s. php3?d=pubs |url= missing title (help). Retrieved 2010- Pages 388-391 discuss the development of the commercial 03-08. fluorescent at General Electric in the 1930s. [18] “SignWeb website”. ST Media Group International. Re- [4] Popper, Frank (2009). “Neon”. Grove Art Online. Oxford trieved 2011-03-08. University Press. [19] Strattman, Wayne (1997). “The Luminous Tube: An il- [5] Thielen, Marcus (August 2005). “Happy Birthday luminating description of how neon signs operate”. Signs Neon!". Signs of the Times. of the Times. Retrieved 2010-12-10. 14 CHAPTER 3. MISCELLANY

[20] Caba, Randall L. “Neon and Fluorescents: A Circus of Similarities”. SignIndustry.com. Retrieved 4 March 2011.

[21] “Lighting & LED”. SignWeb. Media Group International. Retrieved 2012-03-06.

[22] “Knowledge Center”. Brighter Thinking. The Neon Group. Retrieved 2012-03-06.

[23] Michael J. Auer (October 1991). “The Preservation of Historic Signs”. US National Park Service.

3.1.7 Further reading A General Electric NE-34 glow lamp, manufactured circa 1930.

• “2010 Top Ten Endangered Sites”. Heritage Van- couver Society. Retrieved 2010-12-05.

• Bass, Shermakaye (2007-06-06). “Neon Museum 3.2.1 History saving Las Vegas’ iconic signs”. Los Angeles Times. Retrieved 2009-09-12.

• Crowley, David (September 2007). “Life in the Neon was discovered in 1898 by William Ramsay and Darkness”. Creative Review. Retrieved 2010-12-26. Morris W. Travers. The characteristic, brilliant red color Article about neon signage’s flowering and decline in that is emitted by gaseous neon when excited electrically Warsaw and Poland. was noted immediately; Travers later wrote, “the blaze of crimson light from the tube told its own story and was a • Keen, Judy (October 6, 2008). “Save neon signs, sight to dwell upon and never forget.”[1] fans urge”. USA Today. Neon’s scarcity precluded its prompt application for elec- trical lighting along the lines of Moore tubes, which used electric discharges in nitrogen. Moore tubes were com- 3.1.8 External links mercialized by their inventor, Daniel McFarlan Moore, in the early 1900s. After 1902, Georges Claude's company, • Johansson, Feddy. “Svenska Neonskyltar”. Collec- Air Liquide, was producing industrial quantities of neon tion of photographs of Swedish neon signs; text in as a byproduct of his air liquefaction business, and in De- Swedish. cember 1910 Claude demonstrated modern neon lighting based on a sealed tube of neon. In 1915 a U.S. patent was • “Neon Muzeum”. NeonMuzeum.com. Website of issued to Claude covering the design of the electrodes for an organization devoted to preserving Polish neon neon tube lights;[2] this patent became the basis for the signs; in English. monopoly held in the U.S. by his company, Claude Neon Lights, through the early 1930s.[3] Around 1917, Daniel Moore developed the neon lamp 3.2 Neon lamp while working at the General Electric Company. The lamp has a very different design from the much larger See also: Neon lighting neon tubes used for neon lighting. The difference in de- A neon lamp (also neon glow lamp) is a miniature gas sign was sufficient that a U.S. patent was issued for the discharge lamp. The lamp typically consists of a small lamp in 1919.[4] A Smithsonian Institution website notes, glass capsule that contains a mixture of neon and other “These small, low power devices use a physical principle gases at a low pressure and two electrodes (an anode and called coronal discharge. Moore mounted two electrodes a cathode). When sufficient voltage is applied and suffi- close together in a bulb and added neon or argon gas. The cient current is supplied between the electrodes, the lamp electrodes would glow brightly in red or blue, depending produces an orange glow discharge. The glowing portion on the gas, and the lamps lasted for years. Since the elec- in the lamp is a thin region near the cathode; the larger trodes could take almost any shape imaginable, a popu- and much longer neon signs are also glow discharges, but lar application has been fanciful decorative lamps. Glow they use the positive column which is not present in the lamps found practical use as indicators in instrument pan- ordinary neon lamp. Neon glow lamps are widely used as els and in many home appliances until the widespread indicator lamps in the displays of electronic instruments commercialisation of Light-Emitting Diodes (LEDs) in and appliances. the 1970s.”[5] 3.2. NEON LAMP 15

DC and AC supplied NE-2 type neon lamps D

3.2.2 Description

A small electric current, (For a 5 mm bulb diameter NE-2 lamp, the quiescent current is about 400 uA) which may Graph showing the relationship between current and voltage across a neon lamp.[6] be AC or DC, is allowed through the tube, causing it to glow orange-red. The gas is typically a Penning mixture, 99.5% neon and 0.5% argon, which has lower striking internal surface of the lamp with metal and causes it to voltage than pure neon, at a pressure of 1-20 torr. The darken. lamp glow discharge lights at its striking voltage. The voltage required to sustain the discharge is significantly The potential needed to strike the discharge is higher than (~30%) lower than the striking voltage. This is due to what is needed to sustain the discharge. When there is not the organization of positive ions near the cathode. When enough current, the glow forms around only part of the driven from a DC source, only the negatively charged electrode surface. Convective currents make the glowing electrode (cathode) will glow. When driven from an AC areas flow upwards, not unlike the discharge in a Jacob’s source, both electrodes will glow (each during alternate ladder.A photoionization effect can also be observed half cycles). These attributes make neon bulbs (with se- here, as the electrode area covered by the glow discharge ries resistors) a convenient low-cost voltage testers; they can be increased by shining light at the lamp. determine whether a given voltage source is AC or DC, In comparison with incandescent light bulbs, neon lamps and if DC, the polarity of the points being tested. Neon have much higher luminous efficacy. Incandescence is lamps operate using a low current glow discharge. Higher heat-driven light emission, so a large portion of the elec- power devices, such as mercury-vapor lamps or metal tric energy put into an incandescent bulb is converted into halide lamps use a higher current arc discharge. Low heat. Non-incandescent light sources such as neon light pressure sodium-vapor lamps use a neon Penning mixture bulbs, fluorescent light bulbs, and light emitting diodes for warm up and can be operated as giant neon lamps if are therefore much more energy efficient than normal in- operated in a low power mode. candescent light bulbs. Green neon bulbs[7] can produce Once the neon lamp has reached breakdown, it can sup- up to 65 lumens per watt of power input, while white neon port a large current flow. Because of this characteris- bulbs have an efficacy of around 50 lumens per watt. In tic, electrical circuitry external to the neon lamp must contrast, a standard incandescent light bulb only produces [8] limit the current through the circuit or else the current around 13.5 lumens per watt. will rapidly increase until the lamp is destroyed. For indicator-sized lamps, a resistor typically limits the cur- rent. Larger neon sign sized lamps often use a specially 3.2.3 Applications constructed high voltage transformer with high leakage inductance or other electrical ballast to limit the available Small neon lamps are most widely used as indicators in current. electronic equipment and appliances, due to their low When the current through the lamp is lower than the cur- power consumption, long life, and ability to operate off rent for the highest-current discharge path, the glow dis- mains power. Larger lamps are used in neon signage. charge may become unstable and not cover the entire sur- Most small neon (indicator-sized) lamps, such as the face of the electrodes.[6] This may be a sign of aging of the common NE-2, break down at between 90 and 110 volts. indicator bulb, and is exploited in the decorative “flicker The breakdown feature of neon lamps allows them to flame” neon lamps. However, while too low a current be used as very simple voltage regulators or overvoltage causes flickering, too high a current increases the wear of protection devices. In the 1960s General Electric (GE), the electrodes by stimulating sputtering, which coats the Signalite, and other firms made special extra-stable neon 16 CHAPTER 3. MISCELLANY

normal glow discharge mode; some literature references their use as detectors of radiation up into the optical regime when operated in abnormal glow mode. Coupling of microwaves into the plasma may be in free space, in waveguide, by means of a parabolic concentrator (e.g., Winston cone), or via capacitive means via a loop or dipole antenna mounted directly to the lamp. In 1930s radio sets, neon lamps were used as tuning indi- cators, called “tuneons” and would give a brighter glow as the station was tuned in correctly. Because of their com- paratively fast response time, in the early development of television neon lamps were used as the light source in many mechanical-scan TV displays. Although most of these applications use ordinary off-the- shelf dual-electrode lamps, in one case it was found that special 3 (or more) electrode lamps, with the extra elec- trode acting as the coupling antenna, provided even better results (lower noise and higher sensitivity). This discov- The digits of a Nixie tube. ery received an application patent (Kopeika et al.) Neon lamps with several shaped electrodes were used as lamps for electronic uses. alphanumerical displays known as Nixie tubes. These have since been replaced by other display devices such Like other gas discharge lamps,[9] the neon bulb as light emitting diodes, vacuum fluorescent displays, and has negative resistance; its voltage falls with increas- liquid crystal displays. Novelty glow lamps with shaped ing current after the bulb reaches its breakdown electrodes (such as flowers and leaves), often coated with voltage.[10][11][12] Therefore the bulb has hysteresis; its phosphors, have been made for artistic purposes. In some turn-off (extinction) voltage is lower than its turn-on of these, the glow that surrounds an electrode is part of (breakdown) voltage.[13] This allows it to be used as the design. an active switching element. Neon bulbs were used to make relaxation oscillator circuits,[13][14][11] for low frequency applications such as flashing warning lights, stroboscopes[15] tone generators in electronic organs,[11] and as time bases and deflection oscillators in early cathode ray oscilloscopes.[16] Neon bulbs can also be bistable, and were even used to build digital logic cir- cuits such as logic gates, flip-flop, binary memories, and digital counters.[17] [18] 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. A variant of the NE-2 type lamp, the NE-77, had three parallel wires (in a plane) in- stead of the usual two. It was also intended primarily to be a circuit component. Unlit and lit neon lamps (NE-2 type) and their light spectrum. Neon lamps have been historically used as microwave and millimeter-wave detectors ('plasma diodes’ or GDDs- Glow Discharge Detectors) up to about 100 GHz or so and in such service were said to exhibit comparable sen- Colour sitivity (of the order of a few 10s to perhaps 100 mi- crovolts) to the familiar 1N23-type catwhisker-contacted Neon indicator lamps are normally orange, and are fre- silicon diodes once ubiquitous in microwave equipment. quently used with a coloured filter over them to improve More recently it has been found that these lamps work contrast and change their colour to red or a redder orange, well as detectors even at submillimeter ('terahertz') fre- or less often green. quencies and they have been successfully used as pixels in They can also be filled with argon, krypton, or xenon several experimental imaging arrays at these wavelengths. rather than neon, or mixed with it. While the electrical In these applications the lamps are operated either in operating characteristics remain similar, the lamps light 'starvation' mode (to reduce lamp-current noise) or in with a bluish glow (including some ultraviolet) rather than 3.2. NEON LAMP 17

[2] US 1125476, Georges Claude, “Systems of Illuminating by Luminescent Tubes”, issued 1915-01-19

[3] “Claude Neon Lights Wins Injunction Suit: Also Gets Rights to Recover Profits and Damages Resulting From Patent Infringement”. The New York Times. November 28, 1928. Paid access.

[4] US patent 1316967, Daniel McFarlan Moore, “Gaseous Conduction Lamp”, issued 1919-09-23, assigned to Gen- eral Electric Company

[5] “Lamp Inventors 1880-1940: Moore Lamp”. The Smith- sonian Institution.

[6] C.R. Dougherty, T.D. Foulke, J.D. Harden, T.L. Hewitt, Phosphor-coloured neon lamps F.N. Peters, R.D. Smith, and J.W. Tuttle, General Elec- tric Glow Lamp Manual, 2nd ed. (General Electric Com- pany, 1966), Chapter 1: Physics and characteristics of neon’s characteristic reddish-orange glow. Ultraviolet ra- glow lamps: Theory of gaseous conduction in the glow diation then can be used to excite a phosphor coating in- lamp, pages 1-3; see Fig. 1.1, Characteristic curve of the side of the bulb and provide a wide range of various col- neon lamp. In the current vs. voltage curve in this arti- ors, including white.[19] A mixture of neon and krypton cle, the portion of the curve between points A and B cor- can be used for green glow, but nevertheless “green neon” respond to the points E and F in Fig. 1.1. From p. 2: lamps are more commonly phosphor-based. “After breakdown occurs the lamp passes through a tran- sition region EF which is an unstable region of operation. The shaded portion indicates the region in which oscilla- Latching tion can occur. This region is often referred to as the neg- ative resistance region, since voltage decreases as current Since at least the 1940s, argon, neon, and phosphored increase[s], contrary to normal behavior in a resistive ele- glow thyratron latching indicators (which would light up ment. … As the current through the lamp is allowed to in- crease further, the lamp enters the normal glow discharge upon an impulse on their starter electrode and extinguish region represented by section FG [where the point G cor- only after their anode voltage was cut) were available for responds to the point C in the current vs. voltage graph example as self-displaying shift registers in large-format, of this article] in Fig. 1.1 where voltage changes a mini- [20] crawling-text dot-matrix displays, or, combined in a mum amount with a change in current. … In the normal 4x4, four-color phosphored-thyratron matrix, as a stack- glow region the glow is confined to a portion of the cath- able 625-color RGBA pixel for large video graphics ode surface and the amount of cathode surface covered by arrays.[21] Multiple-cathode and/or anode glow thyratrons the glow is somewhat proportional to the tube current.” called Dekatrons could count forwards and backwards while their count state was visible as a glow on one [7] “Other emitted colors such as green, yellow and blue are available through secondary emission by coating the inside of the numbered cathodes.[22] These were used as self- surface of the envelope with phosphor.” — International displaying divide-by-n counter/timer/prescalers in count- Light Technology ing instruments, or as adder/subtracters in calculators. [8] Thielen, Marcus (2006-02-10). “LED or Neon”. Re- trieved 2008-12-30. 3.2.4 See also [9] Raju, Gorur Govinda (2006). Gaseous Electronics: The- • Timeline of lighting technology ory and Practice. Taylor and Francis. p. 453. ISBN 0849337631. • List of light sources [10] Daugherty, C. L.; Tuttle, J.W. et al (1965). G.E. Glow • Pearson-Anson effect Lamp Manual, 2nd Ed.. Cleveland, Ohio: General Elec- tric. p. 2. • Magic eye tube [11] Bauman, Edward (1966). Applications of Neon Lamps • Neon sign and Discharge Tubes. USA: Carleton Press. p. 18. • Light art [12] Dance, J. B. (1968). Cold Cathode Tubes. London: Iliffe. p. 7.

3.2.5 References [13] Gottlieb, Irving M. (1997). Practical Oscillator Hand- book. Elsevier. pp. 69–70. ISBN 0080539386. [1] Weeks, Mary Elvira (2003). Discovery of the Elements: Third Edition (reprint). Kessinger Publishing. p. 287. [14] GE Glow Lamp Manual 1965, p.14-18 18 CHAPTER 3. MISCELLANY

[15] Burton, Walter E. (February 1948). “Magic with neon glow lamps”. Popular Science (New York: Popular Sci- ence Publishing Co.) 152 (2): 194–196. ISSN 0161- 7370. Retrieved April 14, 2014.

[16] Wahl, Horst D. (2005). “Tutorial Oscilloscope”. Phys4822L Advanced Lab-Experiment 11: Studies of electrons with a CRT. Prof. Horst D. Wahl, Physics Dept.,Florida State Univ. Retrieved April 14, 2014.

[17] GE Glow Lamp Manual 1965, p.35-36, 41-66

[18] See:

• William G. Miller, Using and Understanding Miniature Neon Lamps (Indianapolis, Indiana: Howard W. Sams, 1969). • A.A. Vuylsteke, “Neon lamp flip-flop and binary counter,” Electronics, vol. 26, page 248 (April 1953). • M.S. Raphael and A.S. Robinson, “Digital storage using neon tubes,” Electronics, vol. 29, pages 162- 165 (July 1956). • Charles E. Hendrix, “A study of the neon bulb as a nonlinear circuit element,” Proceedings of the Insti- tute of Radio Engineers: Transactions on component parts, vol. 3, no. 2, pages 44-54 (September 1956). (Use of neon lamps in “and” and “or” gates.) • J.C. Manley and E.F. Buckley, “Neon diode ring counter,” Electronics, vol. 23, pages 84-87 (January 1950). • R.L. Ives, “Neon oscillator rings,” Electronics, vol. 31, pages 108-115 (10 October 1958). • C.E. Hendrix and R.B. Purcell, “Neon lamp logic gates play tic-tac-toe,” Electronics, vol. 31, pages 68-69 (20 June 1958).

[19] Yen, William M.; Yamamoto, Hajime (2007). Phosphor handbook. CRC Press. p. 442. ISBN 978-0-8493-3564- 8.

[20] “Philips, 1968: ZC1050 data sheet” (PDF). Retrieved 10 May 2013.

[21] “Melz, 1944: IНДIКАTОР ИТМ2-M data sheet” (PDF). Retrieved 9 May 2013.

[22] “ETL: GCA10G/GSA10G data sheet” (PDF). Retrieved 10 May 2013. Chapter 4

Text and image sources, contributors, and licenses

4.1 Text

• Neon Source: http://en.wikipedia.org/wiki/Neon?oldid=642164288 Contributors: Kpjas, CYD, Vicki Rosenzweig, Mav, Koyaanis Qatsi, Andre Engels, LA2, William Avery, SimonP, DrBob, Heron, Jaknouse, Fonzy, Ubiquity, RTC, Tim Starling, Erik Zachte, Lexor, Ixfd64, Sannse, Eric119, Minesweeper, Dgrant, Looxix, Ahoerstemeier, Mgimpel, Suisui, Александър, Poor Yorick, Andres, Cratbro, Evercat, Mxn, BRG, Raven in Orbit, Epo, Schneelocke, Hashar, Emperorbma, EL Willy, Stone, David Latapie, Tpbradbury, Grendelkhan, Finlay McWalter, Robbot, Moondyne, Kowey, Romanm, Naddy, Jondel, Wikibot, Ungvichian, Raeky, Anthony, Dina, Carnildo, Dave6, Giftlite, Christopher Parham, Marnanel, Robin Patterson, Misterkillboy, Lupin, Herbee, Everyking, Solipsist, Darrien, SWAdair, Yath, Quadell, Antandrus, Vina, Rdsmith4, Sebbe, Icairns, Sfoskett, Karl-Henner, CanSpice, Edsanville, Jcw69, Wyllium, Deglr6328, Adashiel, Trevor MacInnis, Venu62, Indosauros, Discospinster, Pak21, Vsmith, Paul August, Bender235, ESkog, 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19 20 CHAPTER 4. TEXT AND IMAGE SOURCES, CONTRIBUTORS, AND LICENSES

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4.2 Images

• File:1003-1005_Broadway_Ann_Arbor.JPG Source: http://upload.wikimedia.org/wikipedia/commons/b/b9/1003-1005_Broadway_ Ann_Arbor.JPG License: Public domain Contributors: Library of Congress Historic American Buildings Survey Archive: http://lcweb2. loc.gov/pnp/habshaer/mi/mi0100/mi0136/photos/089658pu.tif Original artist: Historic American Buildings Survey • File:Asterisks_one.svg Source: http://upload.wikimedia.org/wikipedia/commons/4/49/Asterisks_one.svg License: CC BY-SA 3.0 Con- tributors: Own work Original artist: DePiep • File:Asterisks_one_(right).svg Source: http://upload.wikimedia.org/wikipedia/commons/1/1c/Asterisks_one_%28right%29.svg Li- cense: CC BY-SA 3.0 Contributors: Own work Original artist: DePiep 4.2. IMAGES 21

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4.3 Content license

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