Editing Electron (section)

=== 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>