Editing Thermionic emission (section)

== History ==
Because the [[electron]] was not identified as a separate physical particle until the work of [[J. J. Thomson]] in 1897, the word "electron" was not used when discussing experiments that took place before this date.

The phenomenon was initially reported in 1853 by [[Edmond Becquerel]].<ref>{{cite journal |last1=Becquerel |first1=Edmond |title=Reserches sur la conductibilité électrique des gaz à des températures élevées |journal=Comptes Rendus |date=1853 |volume=37 |pages=20–24 |url=https://www.biodiversitylibrary.org/item/16564#page/30/mode/1up |trans-title=Researches on the electrical conductivity of gases at high temperatures |language=French}}
* Extract translated into English: {{cite journal |last1=Becquerel |first1=E. |title=Researches on the electrical conductivity of gases at high temperatures |journal=Philosophical Magazine |date=1853 |volume=6 |pages=456–457 |url=https://www.biodiversitylibrary.org/item/20076#page/470/mode/1up |series=4th series}}</ref><ref>{{ cite thesis |last=Paxton |first=William Francis |title=Thermionic Electron Emission Properties of Nitrogen-Incorporated Polycrystalline Diamond Films |type=PhD dissertation |publisher=Vanderbilt University |date=18 April 2013 |url=https://etd.library.vanderbilt.edu/etd-03262013-131559 |access-date=2022-12-16 |archive-url=https://web.archive.org/web/20161123053917/http://etd.library.vanderbilt.edu/available/etd-03262013-131559/unrestricted/Paxton_Thesis.pdf |archive-date=2016-11-23 |hdl=1803/11438}}</ref><ref>{{ cite web |url=https://www.britannica.com/technology/thermionic-power-converter |title=Thermionic power converter |website=Encyclopedia Britannica |access-date=2016-11-22 |url-status=live |archive-url=https://web.archive.org/web/20161123055013/https://www.britannica.com/technology/thermionic-power-converter |archive-date=2016-11-23}}</ref> It was observed again in 1873 by [[Frederick Guthrie (scientist)|Frederick Guthrie]] in Britain.<ref>{{ cite journal |first=Frederick |last=Guthrie |author-link=Frederick Guthrie (scientist) |date=October 1873 |url=https://books.google.com/books?id=U08wAAAAIAAJ&pg=PA257 |title=On a relation between heat and static electricity |journal=The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science |series=4th |volume=46 |issue= 306|pages=257–266 |url-status=live |archive-url=https://web.archive.org/web/20180113210540/https://books.google.com/books?id=U08wAAAAIAAJ&pg=PA257 |archive-date=2018-01-13 |doi=10.1080/14786447308640935|url-access=subscription }}</ref><ref>{{ cite journal |first=Frederick |last=Guthrie |author-link=Frederick Guthrie (scientist) |date=February 13, 1873 |url=https://books.google.com/books?id=GLk9AQAAMAAJ&pg=PA168 |title=On a new relation between heat and electricity |journal=Proceedings of the Royal Society of London |volume=21 |issue= 139–147|pages=168–169 |doi=10.1098/rspl.1872.0037 |url-status=live |archive-url=https://web.archive.org/web/20180113210540/https://books.google.com/books?id=GLk9AQAAMAAJ&pg=PA168 |archive-date=January 13, 2018 |doi-access=free}}</ref> While doing work on charged objects, Guthrie discovered that a red-hot iron sphere with a negative charge would lose its charge (by somehow discharging it into air). He also found that this did not happen if the sphere had a positive charge.<ref>{{ cite book | last1 = Richardson | first1 = O. W. | year = 2003 | title = Thermionic Emission from Hot Bodies | url = https://books.google.com/books?id=PrbOIoMnxnwC&pg=PA196 | pages = 196 | publisher = [[Wexford College Press]] | isbn = 978-1-929148-10-3 | url-status = live | archive-url = https://web.archive.org/web/20131231221553/http://books.google.com/books?id=PrbOIoMnxnwC&pg=PA196 | archive-date = 2013-12-31 }}</ref> Other early contributors included [[Johann Wilhelm Hittorf]] (1869–1883),<ref>{{ cite journal |first=W. |last=Hittorf |author-link=Johann Wilhelm Hittorf |year=1869 |url=http://babel.hathitrust.org/cgi/pt?id=uc1.b4433674;view=1up;seq=25 |title=Ueber die Electricitätsleitung der Gase |language=de |trans-title=On electrical conduction of gases |journal=Annalen der Physik und Chemie |series=2nd series |volume=136 |issue=1 |pages=1–31 |doi=10.1002/andp.18692120102 |bibcode=1869AnP...212....1H|url-access=subscription }}</ref><ref>{{ cite journal |first=W. |last=Hittorf |author-link=Johann Wilhelm Hittorf |year=1869 |url=http://babel.hathitrust.org/cgi/pt?id=uc1.b4433674;view=1up;seq=221 |title=Ueber die Electricitätsleitung der Gase |language=de |trans-title=On electrical conduction of gases |journal=Annalen der Physik und Chemie |series=2nd series |volume=136 |issue= 2|pages=197–234 |doi=10.1002/andp.18692120203 |bibcode=1869AnP...212..197H|url-access=subscription }}</ref><ref>{{ cite journal |first=W. |last=Hittorf |author-link=Johann Wilhelm Hittorf |year=1874 |url=http://gallica.bnf.fr/ark:/12148/bpt6k149954/f452.image.langEN |title=Ueber die Electricitätsleitung der Gase |language=de |trans-title=On electrical conduction of gases |journal=Annalen der Physik und Chemie |volume=Jubalband (anniversary volume) |pages=430–445 |url-status=live |archive-url=https://web.archive.org/web/20180113210541/http://gallica.bnf.fr/ark:/12148/bpt6k149954/f452.image.langEN |archive-date=2018-01-13}}</ref><ref>{{ cite journal |first=W. |last=Hittorf |author-link=Johann Wilhelm Hittorf |year=1879 |url=http://babel.hathitrust.org/cgi/pt?id=wu.89048352421;view=1up;seq=575 |title=Ueber die Electricitätsleitung der Gase |language=de |trans-title=On electrical conduction of gases |journal=Annalen der Physik und Chemie |series=3rd series |volume=7 |issue= 8|pages=553–631 |doi=10.1002/andp.18792430804 |bibcode=1879AnP...243..553H|url-access=subscription }}</ref><ref>{{ cite journal |first=W. |last=Hittorf |author-link=Johann Wilhelm Hittorf |year=1883 |url=http://babel.hathitrust.org/cgi/pt?id=wu.89048352561;view=1up;seq=727 |title=Ueber die Electricitätsleitung der Gase |language=de |trans-title=On electrical conduction of gases |journal=Annalen der Physik und Chemie |series=3rd series |volume=20 |issue= 12|pages=705–755 |doi=10.1002/andp.18832561214}}</ref><ref>{{ cite journal |first=W. |last=Hittorf |author-link=Johann Wilhelm Hittorf |year=1884 |url=http://babel.hathitrust.org/cgi/pt?id=wu.89048352587;view=1up;seq=106 |title=Ueber die Electricitätsleitung der Gase |language=de |trans-title=On electrical conduction of gases |journal=Annalen der Physik und Chemie |series=3rd series |volume=21 |issue= 1|pages=90–139 |doi=10.1002/andp.18842570105 |bibcode=1884AnP...257...90H|url-access=subscription }}</ref> [[Eugen Goldstein]] (1885),<ref>E. Goldstein (1885) [https://books.google.com/books?id=yhVbAAAAYAAJ&pg=PA79 "Ueber electrische Leitung in Vacuum"] {{webarchive|url=https://web.archive.org/web/20180113210540/https://books.google.com/books?id=yhVbAAAAYAAJ&pg=PA79 |date=2018-01-13}} (On electric conduction in vacuum) ''Annalen der Physik und Chemie'', 3rd series, ''24'': 79–92.</ref> and [[Julius Elster]] and [[Hans Friedrich Geitel]] (1882–1889).<ref>Elster and Geitel (1882) [http://babel.hathitrust.org/cgi/pt?id=wu.89048352488;view=1up;seq=211 "Ueber die Electricität der Flamme"] (On the electricity of flames), ''Annalen der Physik und Chemie'', 3rd series, ''16'': 193–222.</ref><ref>Elster and Geitel (1883) [http://babel.hathitrust.org/cgi/pt?id=wu.89048352546;view=1up;seq=612 "Ueber Electricitätserregung beim Contact von Gasen und glühenden Körpern"] (On the generation of electricity by the contact of gases and incandescent bodies), ''Annalen der Physik und Chemie'', 3rd series, ''19'': 588–624.</ref><ref>Elster and Geitel (1885) [http://babel.hathitrust.org/cgi/pt?id=uc1.b4433723;view=1up;seq=15 "Ueber die unipolare Leitung erhitzter Gase"] (On the unipolar conductivity of heated gases") ''Annalen der Physik und Chemie'', 3rd series, ''26'': 1–9.</ref><ref>Elster and Geitel (1887) [http://babel.hathitrust.org/cgi/pt?id=uc1.b4433728;view=1up;seq=123 "Ueber die Electrisirung der Gase durch glühende Körper"] (On the electrification of gases by incandescent bodies") ''Annalen der Physik und Chemie'', 3rd series, ''31'': 109–127.</ref><ref>Elster and Geitel (1889) [http://babel.hathitrust.org/cgi/pt?id=uc1.b4433733;view=1up;seq=333 "Ueber die Electricitätserregung beim Contact verdünnter Gase mit galvanisch glühenden Drähten"] (On the generation of electricity by contact of rarefied gas with electrically heated wires) ''Annalen der Physik und Chemie'', 3rd series, ''37'': 315–329.</ref>

=== Edison effect ===
Thermionic emission was observed again by [[Thomas Edison]] in 1880 while his team was trying to discover the reason for breakage of [[Incandescent light bulb#Carbon filament and vacuum|carbonized bamboo filaments]]<ref>{{Cite web |title=How Japanese Bamboo Helped Edison Make The Light Bulb |url=https://www.amusingplanet.com/2019/05/how-japanese-bamboo-helped-edison-make.html |access-date=2024-06-03 |website=www.amusingplanet.com |language=en}}</ref> and undesired blackening of the interior surface of the bulbs in his [[incandescent lamp]]s. This blackening was [[carbon]] deposited from the filament and was darkest near the positive end of the filament loop, which ''apparently'' cast a light shadow on the glass, as if negatively-charged carbon emanated from the negative end and was attracted towards and sometimes absorbed by the positive end of the filament loop. This projected carbon was deemed "electrical carrying" and initially ascribed to an effect in [[Crookes tube|Crookes tubes]] where negatively-charged [[cathode rays]] from [[ionized gas]] move from a negative to a positive electrode. To try to redirect the charged carbon particles to a separate electrode instead of the glass, Edison did a series of experiments (a first inconclusive one is in his notebook on 13 February 1880) such as the following successful one:<ref>{{Cite journal |last=Johnson |first=J. B. |date=1960-12-01 |title=Contribution of Thomas A. Edison to Thermionics |url=https://doi.org/10.1119/1.1935997 |journal=American Journal of Physics |volume=28 |issue=9 |pages=763–773 |doi=10.1119/1.1935997 |bibcode=1960AmJPh..28..763J |issn=0002-9505|url-access=subscription }}</ref>
{{Multi image
| image1            = Edison light bulb with plate.jpg
| caption1          = One '''Edison effect bulb''' consisted of an [[vacuum|evacuated]] bulb with an externally-wired [[electrode]] such as a metal plate in this example (variants used platinum foil or extra wire instead) isolated from the [[Incandescent light bulb#Filament|carbon filament]] (hairpin-shaped in this example).
| align             = center
| image2            = EdisonEffect-side-by-side.svg
| caption2          = Edison's [[electric circuit|circuit]] configured his bulb (large circle) such that its electrode was in series with an [[ammeter]] (A) to measure [[conventional current]] and a [[voltage source]] (separate from the power source heating the filament) to [[biasing|bias]] the electrode either positively (in which case electrons were [[Coulomb's law|attracted]] and flowed along the arrows from the filament through the partial vacuum to the electrode) or negatively (which resulted in no measurable current). We now know that in addition to carbon molecules, the filament was emitting electrons, which have negative charge and thus are attracted to a positively-charged electrode but not a negatively-charged electrode.
| total_width       = 700
| header            = Experiment demonstrating the Edison effect
}}

{{Multi image
| total_width       = dsf
| image1            = 
}}

This effect had many applications. Edison found that the current emitted by the hot filament increased rapidly with [[voltage]], and filed a patent for a [[Voltage regulator|voltage-regulating]] device using the effect on 15 November 1883,<ref>{{cite patent|inventor1-first=Thomas A. |inventor1-last=Edison |inventorlink1=Thomas Edison |title=Electrical indicator |country=US |number=307031 |fdate=1883-11-15 |pubdate= 1884-10-21}}</ref> notably the first US patent for an electronic device. He found that sufficient current would pass through the device to operate a [[telegraph]] sounder, which was exhibited at the [[International Electrical Exhibition of 1884]] in Philadelphia. Visiting British scientist [[William Preece]] received several bulbs from Edison to investigate. Preece's 1885 paper on them referred to the one-way current through the partial vacuum as the ''Edison effect,''<ref>{{cite journal |first=William Henry |last=Preece |author-link=William Preece |year=1885 |url=https://books.google.com/books?id=xmdDAAAAYAAJ&pg=PA219 |title=On a peculiar behaviour of glow lamps when raised to high incandescence |journal=Proceedings of the Royal Society of London |volume=38 |issue= 235–238|pages=219–230 |doi=10.1098/rspl.1884.0093 |url-status=live |archive-url=https://web.archive.org/web/20140626213555/http://books.google.com/books?id=xmdDAAAAYAAJ&pg=PA219 |archive-date=2014-06-26 |doi-access=free}} Preece coins the term the "Edison effect" on page 229.</ref><ref name="Josephson">{{cite book | last1 = Josephson | first1 = M. | year = 1959 | title = Edison | url = https://archive.org/details/edisonbiography00jose | url-access = registration | publisher = [[McGraw-Hill]] | isbn = 978-0-07-033046-7 }}</ref> although that term is occasionally used to refer to thermionic emission itself. British physicist [[John Ambrose Fleming]], working for the British [[Marconi Company|Wireless Telegraphy Company]], discovered that the Edison effect could be used to detect [[radio waves]]. Fleming went on to develop a two-element [[vacuum tube|thermionic vacuum tube diode]] called the [[Fleming valve]] (patented 16 November 1904).<ref>Provisional specification for a thermionic valve was lodged on November 16, 1904. In this document, Fleming coined the British term "valve" for what in North America is called a "vacuum tube": "The means I employ for this purpose consists in the insertion in the circuit of the alternating current of an appliance which permits only the passage of electric current in one direction and constitutes therefore an electrical valve."</ref><ref>{{cite patent|inventor1-first=John Ambrose |inventor1-last=Fleming |inventor1-link=John Ambrose Fleming |title=Improvements in instruments for detecting and measuring alternating electric currents |country=GB |number=190424850 |fdate=1905-08-15 |pubdate=1905-09-21}}</ref><ref>{{cite patent|inventor1-first=John Ambrose |inventor1-last=Fleming |inventor1-link=John Ambrose Fleming |title=Instrument for converting alternating electric currents into continuous currents |country=US |number=803684 |fdate=1905-04-19 |pubdate=1905-11-07}}</ref> Thermionic diodes can also be configured to convert a heat difference to electric power directly without moving parts as a device called a [[thermionic converter]], a type of [[heat engine]].