Editing Electron (section)

== Plasma applications ==

=== Particle beams ===
[[File:Nasa Shuttle Test Using Electron Beam full.jpg|right|thumb|alt=A violet beam from above produces a blue glow about a Space shuttle model|During a [[NASA]] [[wind tunnel]] test, a model of the [[Space Shuttle]] is targeted by a beam of electrons, simulating the effect of [[ion]]izing gases during [[Atmospheric entry|re-entry]].<ref>
{{cite web
 |title=Image # L-1975-02972
 |department=[[Langley Research Center]]
 |publisher= [[NASA]] |date=April 4, 1975
 |url=https://grin.hq.nasa.gov/ABSTRACTS/GPN-2000-003012.html
 |url-status=dead |access-date=2008-09-20 |df=dmy-all
 |archive-url=https://web.archive.org/web/20081207041522/https://grin.hq.nasa.gov/ABSTRACTS/GPN-2000-003012.html
 |archive-date=December 7, 2008
}}</ref>]]

[[Cathode ray|Electron beams]] are used in [[electron beam welding|welding]].<ref>
{{cite web
 | last = Elmer | first = J.
 | title = Standardizing the Art of Electron-Beam Welding
 | publisher=[[Lawrence Livermore National Laboratory]]
 | date=March 3, 2008
 | url = https://www.llnl.gov/str/MarApr08/elmer.html
 |url-status=dead | access-date = 2008-10-16 |df=dmy-all
 | archive-url=https://web.archive.org/web/20080920142328/https://www.llnl.gov/str/MarApr08/elmer.html
 |archive-date=2008-09-20
}}</ref> They allow energy densities up to {{val|e=7|u=W·cm<sup>−2</sup>}} across a narrow focus diameter of {{nowrap|0.1–1.3 mm}} and usually require no filler material. This welding technique must be performed in a vacuum to prevent the electrons from interacting with the gas before reaching their target, and it can be used to join conductive materials that would otherwise be considered unsuitable for welding.<ref>
{{cite book
 | last = Schultz
 | first = H.
 | title = Electron Beam Welding
 | pages = 2–3
 | publisher = [[Woodhead Publishing]]
 | year = 1993
 | isbn = 978-1-85573-050-2
 | url = https://books.google.com/books?id=I0xMo28DwcIC&pg=PA2
 | access-date = 2020-08-25
 | archive-date = 2022-02-04
 | archive-url = https://web.archive.org/web/20220204084011/https://books.google.com/books?id=I0xMo28DwcIC&pg=PA2
 | url-status = live
}}</ref><ref>
{{cite book
 | last = Benedict
 | first = G.F.
 | title = Nontraditional Manufacturing Processes
 | series = Manufacturing engineering and materials processing
 | volume = 19
 | page = 273
 | publisher = [[CRC Press]]
 | year = 1987
 | isbn = 978-0-8247-7352-6
 | url = https://books.google.com/books?id=xdmNVSio8jUC&pg=PA273
 | access-date = 2020-08-25
 | archive-date = 2022-02-04
 | archive-url = https://web.archive.org/web/20220204084012/https://books.google.com/books?id=xdmNVSio8jUC&pg=PA273
 | url-status = live
}}</ref>

[[Electron-beam lithography]] (EBL) is a method of etching semiconductors at resolutions smaller than a [[Micrometre|micrometer]].<ref>
{{cite conference
 | last = Ozdemir | first = F.S.
 | title = Electron beam lithography | pages = 383–391
 | conference = Proceedings of the 16th Conference on Design automation
 | date = June 25–27, 1979 | place = San Diego, CA
 | publisher = [[IEEE Press]]
 | url = https://portal.acm.org/citation.cfm?id=800292.811744
 | access-date = 2008-10-16 |df=dmy-all
}}</ref> This technique is limited by high costs, slow performance, the need to operate the beam in the vacuum and the tendency of the electrons to scatter in solids. The last problem limits the resolution to about 10&nbsp;nm. For this reason, EBL is primarily used for the production of small numbers of specialized [[integrated circuit]]s.<ref>
{{cite book
 | last = Madou
 | first = M.J.
 | title = Fundamentals of Microfabrication: the Science of Miniaturization
 | pages = 53–54
 | publisher = CRC Press
 | edition = 2nd
 | year = 2002
 | isbn = 978-0-8493-0826-0
 | url = https://books.google.com/books?id=9bk3gJeQKBYC&pg=PA53
 | access-date = 2020-08-25
 | archive-date = 2021-01-07
 | archive-url = https://web.archive.org/web/20210107160805/https://books.google.com/books?id=9bk3gJeQKBYC&pg=PA53
 | url-status = live
}}</ref>

[[Electron beam processing]] is used to irradiate materials in order to change their physical properties or [[Sterilization (microbiology)|sterilize]] medical and food products.<ref>
{{cite conference
 | last1 = Jongen | first1 = Y.
 | last2 = Herer | first2 = A.
 | title=[no title cited]
 | conference = Electron Beam Scanning in Industrial Applications
 | department = APS/AAPT Joint Meeting
 | date =2–5 May 1996
 | publisher = [[American Physical Society]]
 | bibcode =1996APS..MAY.H9902J
}}</ref> Electron beams fluidise or quasi-melt glasses without significant increase of temperature on intensive irradiation: e.g. intensive electron radiation causes a many orders of magnitude decrease of viscosity and stepwise decrease of its activation energy.<ref>
{{cite journal
 | last1 = Mobus | first1 = G. | display-authors = etal
 | year = 2010
 | title =  Nano-scale quasi-melting of alkali-borosilicate glasses under electron irradiatio
 | journal = Journal of Nuclear Materials
 | volume = 396 | issue = 2–3 | pages = 264–271
 | doi = 10.1016/j.jnucmat.2009.11.020
 | bibcode = 2010JNuM..396..264M
}}</ref>

[[Linear particle accelerator]]s generate electron beams for treatment of superficial tumors in [[radiation therapy]]. [[Electron therapy]] can treat such skin lesions as [[basal-cell carcinoma]]s because an electron beam only penetrates to a limited depth before being absorbed, typically up to 5&nbsp;cm for electron energies in the range 5–20&nbsp;MeV. An electron beam can be used to supplement the treatment of areas that have been irradiated by [[X-ray]]s.<ref>
{{cite journal
 | last1 = Beddar | first1 = A.S.
 | last2 = Domanovic | first2 = Mary Ann
 | last3 = Kubu | first3 = Mary Lou
 | last4 = Ellis | first4 = Rod J.
 | last5 = Sibata | first5 = Claudio H.
 | last6 = Kinsella | first6 = Timothy J.
 | title = Mobile linear accelerators for intraoperative radiation therapy
 | journal = [[AORN Journal]] | year = 2001
 | volume = 74 | issue = 5 | pages = 700–705
 | doi =10.1016/S0001-2092(06)61769-9
 | pmid = 11725448
}}</ref><ref>
{{cite web
 | last1 = Gazda
 | first1 = M.J.
 | last2 = Coia
 | first2 = L.R.
 | date = June 1, 2007
 | title = Principles of Radiation Therapy
 | url = https://www.thymic.org/uploads/reference_sub/02radtherapy.pdf
 | access-date = 2013-10-31
 | df = dmy-all
 | archive-date = 2013-11-02
 | archive-url = https://web.archive.org/web/20131102114151/http://www.thymic.org/uploads/reference_sub/02radtherapy.pdf
 | url-status = live
}}</ref>

[[Particle accelerator]]s use electric fields to propel electrons and their antiparticles to high energies.  These particles emit synchrotron radiation as they pass through magnetic fields. The dependency of the intensity of this radiation upon spin polarizes the electron beam – a process known as the [[Sokolov–Ternov effect]].{{efn|The polarization of an electron beam means that the spins of all electrons point into one direction. In other words, the projections of the spins of all electrons onto their momentum vector have the same sign.}} Polarized electron beams can be useful for various experiments. [[Synchrotron]] radiation can also [[Radiation damping|cool]] the electron beams to reduce the momentum spread of the particles.  Electron and positron beams are collided upon the particles' accelerating to the required energies; [[particle detector]]s observe the resulting energy emissions, which [[particle physics]] studies.<ref>
{{cite book
 | last1 = Chao
 | first1 = A.W.
 | last2 = Tigner
 | first2 = M.
 | title = Handbook of Accelerator Physics and Engineering
 | pages = 155, 188
 | url = https://books.google.com/books?id=Z3J4SjftF1YC&pg=PA155
 | publisher = [[World Scientific]]
 | year = 1999
 | isbn = 978-981-02-3500-0
 | access-date = 2020-08-25
 | archive-date = 2022-02-04
 | archive-url = https://web.archive.org/web/20220204071146/https://books.google.com/books?id=Z3J4SjftF1YC&pg=PA155
 | url-status = live
}}</ref>

=== Imaging ===
[[Low-energy electron diffraction]] (LEED) is a method of bombarding a crystalline material with a [[Collimated light|collimated beam]] of electrons and then observing the resulting diffraction patterns to determine the structure of the material. The required energy of the electrons is typically in the range 20–200&nbsp;eV.<ref>
{{cite book
 | last = Oura | first = K.
 | title = Surface Science: An Introduction
 | pages = 1–45
 | publisher = [[Springer Science+Business Media]] | year = 2003
 | isbn = 978-3-540-00545-2
 |display-authors=etal
}}</ref> The [[reflection high-energy electron diffraction]] (RHEED) technique uses the reflection of a beam of electrons fired at various low angles to characterize the surface of crystalline materials. The beam energy is typically in the range 8–20&nbsp;keV and the angle of incidence is 1–4°.<ref>
{{cite book
 | last1 = Ichimiya
 | first1 = A.
 | last2 = Cohen
 | first2 = P.I.
 | title = Reflection High-energy Electron Diffraction
 | page = 1
 | publisher = Cambridge University Press
 | year = 2004
 | isbn = 978-0-521-45373-8
 | url = https://books.google.com/books?id=AUVbPerNxTcC&pg=PA1
 | access-date = 2020-08-25
 | archive-date = 2022-02-04
 | archive-url = https://web.archive.org/web/20220204084445/https://books.google.com/books?id=AUVbPerNxTcC&pg=PA1
 | url-status = live
}}</ref><ref>
{{cite journal
 | last = Heppell | first = T.A.
 | year = 1967
 | title = A combined low energy and reflection high energy electron diffraction apparatus
 | journal = [[Measurement Science and Technology|Journal of Scientific Instruments]]
 | volume = 44 | issue = 9 | pages = 686–688
 | doi =10.1088/0950-7671/44/9/311
 | bibcode = 1967JScI...44..686H
}}</ref>

The [[electron microscope]] directs a focused beam of electrons at a specimen. Some electrons change their properties, such as movement direction, angle, and relative phase and energy as the beam interacts with the material. Microscopists can record these changes in the electron beam to produce atomically resolved images of the material.<ref>
{{cite web
 | last = McMullan
 | first = D.
 | title = Scanning Electron Microscopy: 1928–1965
 | publisher = University of Cambridge
 | year = 1993
 | url = https://www-g.eng.cam.ac.uk/125/achievements/mcmullan/mcm.htm
 | access-date = 2009-03-23
 | df = dmy-all
 | archive-date = 2009-03-16
 | archive-url = https://web.archive.org/web/20090316071650/http://www-g.eng.cam.ac.uk/125/achievements/mcmullan/mcm.htm
 | url-status = live
}}</ref> In blue light, conventional [[optical microscope]]s have a diffraction-limited resolution of about 200&nbsp;nm.<ref>
{{cite book
 | last = Slayter
 | first = H.S.
 | title = Light and electron microscopy
 | page = 1
 | publisher = Cambridge University Press
 | year = 1992
 | isbn = 978-0-521-33948-3
 | url = https://books.google.com/books?id=LlePVS9oq7MC&pg=PA1
 | access-date = 2020-08-25
 | archive-date = 2022-02-04
 | archive-url = https://web.archive.org/web/20220204084446/https://books.google.com/books?id=LlePVS9oq7MC&pg=PA1
 | url-status = live
}}</ref> By comparison, electron microscopes are limited by the [[Matter wave|de Broglie wavelength]] of the electron. This wavelength, for example, is equal to 0.0037&nbsp;nm for electrons accelerated across a 100,000-[[volt]] potential.<ref>
{{cite book
 | last = Cember
 | first = H.
 | title = Introduction to Health Physics
 | pages = 42–43
 | publisher = [[McGraw-Hill|McGraw-Hill Professional]]
 | year = 1996
 | isbn = 978-0-07-105461-4
 | url = https://books.google.com/books?id=obcmBZe9es4C&pg=PA42
 | access-date = 2020-08-25
 | archive-date = 2022-02-04
 | archive-url = https://web.archive.org/web/20220204084443/https://books.google.com/books?id=obcmBZe9es4C&pg=PA42
 | url-status = live
}}</ref> The [[Transmission Electron Aberration-Corrected Microscope]] is capable of sub-0.05&nbsp;nm resolution, which is more than enough to resolve individual atoms.<ref>
{{cite journal
 |last1           = Erni
 |first1          = R.
 |display-authors = etal
 |year            = 2009
 |title           = Atomic-Resolution Imaging with a Sub-50-pm Electron Probe
 |journal         = [[Physical Review Letters]]
 |volume          = 102
 |issue           = 9
 |page            = 096101
 |doi             = 10.1103/PhysRevLett.102.096101
 |bibcode         = 2009PhRvL.102i6101E
 |pmid            = 19392535
 |osti = 960283
 |url             = https://digital.library.unt.edu/ark:/67531/metadc927376/
 |access-date     = 2018-08-17
 |archive-date    = 2020-01-02
 |archive-url     = https://web.archive.org/web/20200102164706/https://digital.library.unt.edu/ark:/67531/metadc927376/
 |url-status      = live
}}</ref> This capability makes the electron microscope a useful laboratory instrument for high resolution imaging. However, electron microscopes are expensive instruments that are costly to maintain.

Two main types of electron microscopes exist: [[Transmission electron microscopy|transmission]] and [[scanning electron microscope|scanning]]. Transmission electron microscopes function like [[overhead projector]]s, with a beam of electrons passing through a slice of material then being projected by lenses on a [[Reversal film|photographic slide]] or a [[charge-coupled device]].  Scanning electron microscopes [[Raster scan|rasteri]] a finely focused electron beam, as in a TV set, across the studied sample to produce the image. Magnifications range from 100× to 1,000,000× or higher for both microscope types. The [[scanning tunneling microscope]] uses quantum tunneling of electrons from a sharp metal tip into the studied material and can produce atomically resolved images of its surface.<ref name="bozzola_1999">
{{cite book
 | last1 = Bozzola
 | first1 = J.J.
 | last2 = Russell
 | first2 = L.D.
 | title = Electron Microscopy: Principles and Techniques for Biologists
 | pages = 12, 197–199
 | publisher = [[Jones & Bartlett Learning|Jones & Bartlett Publishers]]
 | year = 1999
 | isbn = 978-0-7637-0192-5
 | url = https://books.google.com/books?id=RqSMzR-IXk0C&pg=PA12
 | access-date = 2020-08-25
 | archive-date = 2022-02-04
 | archive-url = https://web.archive.org/web/20220204084447/https://books.google.com/books?id=RqSMzR-IXk0C&pg=PA12
 | url-status = live
}}</ref><ref>
{{cite book
 | last1 = Flegler | first1 = S.L.
 | last2 = Heckman | first2 = J.W. Jr.
 | last3 = Klomparens | first3 = K.L.
 | title = Scanning and Transmission Electron Microscopy: An Introduction
 |publisher=Oxford University Press |edition=Reprint |year=1995
 | pages = 43–45
 | isbn = 978-0-19-510751-7
}}</ref><ref>
{{cite book
 | last1 = Bozzola
 | first1 = J.J.
 | last2 = Russell
 | first2 = L.D.
 | title = Electron Microscopy: Principles and Techniques for Biologists
 | page = 9
 | publisher = [[Jones & Bartlett Learning|Jones & Bartlett Publishers]]
 | edition = 2nd
 | year = 1999
 | isbn = 978-0-7637-0192-5
 | url = https://books.google.com/books?id=RqSMzR-IXk0C&pg=PA9
 | access-date = 2020-08-25
 | archive-date = 2022-02-04
 | archive-url = https://web.archive.org/web/20220204084444/https://books.google.com/books?id=RqSMzR-IXk0C&pg=PA9
 | url-status = live
}}</ref>

=== Other applications ===
In the [[free-electron laser]] (FEL), a [[relativistic electron beam]] passes through a pair of [[undulator]]s that contain arrays of [[dipole magnet]]s whose fields point in alternating directions. The electrons emit synchrotron radiation that [[Coherence (physics)|coherently]] interacts with the same electrons to strongly amplify the radiation field at the [[resonance]] frequency. FEL can emit a coherent high-[[Radiance|brilliance]] electromagnetic radiation with a wide range of frequencies, from [[microwave]]s to soft X-rays. These devices are used in manufacturing, communication, and in medical applications, such as soft tissue surgery.<ref>
{{cite book
 | last1 = Freund
 | first1 = H.P.
 | last2 = Antonsen
 | first2 = T.
 | title = Principles of Free-Electron Lasers
 | pages = 1–30
 | publisher = [[Springer Science+Business Media|Springer]]
 | year = 1996
 | isbn = 978-0-412-72540-1
 | url = https://books.google.com/books?id=73w9tqTgbiIC&pg=PA1
 | access-date = 2020-08-25
 | archive-date = 2022-02-04
 | archive-url = https://web.archive.org/web/20220204084620/https://books.google.com/books?id=73w9tqTgbiIC&pg=PA1
 | url-status = live
}}</ref>

Electrons are important in [[cathode-ray tube]]s, which have been extensively used as display devices in laboratory instruments, [[computer monitor]]s and [[television set]]s.<ref>
{{cite book
 | last = Kitzmiller | first = J.W.
 | title = Television Picture Tubes and Other Cathode-Ray Tubes: Industry and Trade Summary
 | pages = 3–5
 | publisher = Diane Publishing | year = 1995
 | isbn = 978-0-7881-2100-5
}}</ref> In a [[photomultiplier]] tube, every photon striking the [[photocathode]] initiates an avalanche of electrons that produces a detectable current pulse.<ref>
{{cite book
 | last = Sclater | first = N.
 | title = Electronic Technology Handbook
 | pages = 227–228
 | publisher = [[McGraw-Hill|McGraw-Hill Professional]] | year = 1999
 | isbn = 978-0-07-058048-0
}}</ref> [[Vacuum tube]]s use the flow of electrons to manipulate electrical signals, and they played a critical role in the development of electronics technology. However, they have been largely supplanted by [[solid-state electronics|solid-state devices]] such as the [[transistor]].<ref>
{{cite web
 | title = The History of the Integrated Circuit
 | url = https://nobelprize.org/educational_games/physics/integrated_circuit/history/
 | publisher = [[Nobel Foundation|The Nobel Foundation]]
 | year = 2008
 | access-date = 2008-10-18
 | df = dmy-all
 | archive-date = 2008-12-01
 | archive-url = https://web.archive.org/web/20081201144536/http://nobelprize.org/educational_games/physics/integrated_circuit/history/
 | url-status = live
}}</ref>