Editing Betatron (section)

{{Short description|Cyclic particle accelerator}}
[[File:First betatron 1940.jpg|thumb|One of the first betatrons built by [[Donald Kerst]] ''(visible right)'' at University of Illinois, 1940. Its 4-ton magnet could accelerate electrons to 24&nbsp;MeV.]]
[[File:Betatron 6MeV (1942).jpg|thumb|right|A German 6&nbsp;MeV betatron (1942)]]
[[File:Melbourne University 35MeV Betatron.jpg|thumb|A 35&nbsp;MeV betatron used for photonuclear physics at the University of Melbourne.]]
A '''betatron''' is a type of cyclic [[particle accelerator]] for [[electron]]s.  It consists of a [[torus]]-shaped [[vacuum chamber]] with an electron source.  Circling the torus is an [[magnetic core|iron transformer core]] with a wire winding around it.  The device functions similarly to a [[transformer]], with the electrons in the torus-shaped vacuum chamber as its secondary coil.  An [[alternating current]] in the [[primary winding|primary coils]] accelerates electrons in the vacuum around a circular path.  The betatron was the first machine capable of producing electron beams at energies higher than could be achieved with a simple [[electron gun]], and the first circular accelerator in which particles orbited at a constant radius.<ref>{{Cite web|url=https://www.britannica.com/technology/betatron|title=Betatron {{!}} particle accelerator|website=Encyclopedia Britannica|language=en|access-date=2019-01-24}}</ref>

The concept of the betatron had been proposed as early as 1922 by [[Joseph Slepian]].<ref name="kersthistory">{{cite journal |last1=Kerst |first1=Donald W. |title=Historical Development of the Betatron |journal=Nature |date=January 1946 |volume=157 |issue=3978 |pages=90–95 |doi=10.1038/157090a0|pmid=21015096 |bibcode=1946Natur.157...90K |s2cid=42153256 }}</ref> Through the 1920s and 30s a number of theoretical problems related to the device were considered by scientists including [[Rolf Wideroe]],<ref>{{Cite journal | last1 = Wideröe | first1 = R. | author-link1 = Rolf Widerøe| title = Über ein neues Prinzip zur Herstellung hoher Spannungen | doi = 10.1007/BF01656341 | journal = Archiv für Elektrotechnik | volume = 21 | issue = 4 | pages = 387–406 | date = 17 Dec 1928 | language = de| s2cid = 109942448 }}</ref><ref name="NTNF">{{cite book | title = From nuclear transmutation to nuclear fission, 1932-1939 | last1 = Dahl | first1 = F. | publisher = [[CRC Press]] | year = 2002 | isbn = 978-0-7503-0865-6 | url = https://books.google.com/books?id=Vg6UHu3gZ3gC&q=rolf+wideroe }}
</ref> [[Ernest Walton]], and [[Max Steenbeck]].<ref name="steenbeck">{{cite journal |last1=Steenbeck |first1=Max |title=Beschleunigung von Electronen durch elektrische Wirbelfelder. |journal=Die Naturwissenschaften |date=1943 |volume=31 |issue=S |pages=234–235|doi=10.1007/BF01482241 |bibcode=1943NW.....31..234S |s2cid=6832156 }}</ref>  The first working betatron was constructed by [[Donald Kerst]] at the [[University of Illinois Urbana-Champaign]] in 1940.<ref>{{Cite journal | last1 = Kerst | first1 = D. W. | s2cid = 120616002 | author-link1 = Donald William Kerst| title = Acceleration of Electrons by Magnetic Induction | doi = 10.1103/PhysRev.58.841 | bibcode = 1940PhRv...58..841K| journal = [[Physical Review]] | volume = 58 | issue = 9 | pages = 841 | year = 1940 }}</ref><ref name="kerst1941">{{Cite journal | last1 = Kerst | first1 = D. W. | author-link = Donald William Kerst | title = The Acceleration of Electrons by Magnetic Induction | journal = [[Physical Review]] | volume = 60 | issue = 1 | pages = 47–53 | year = 1941 | doi = 10.1103/PhysRev.60.47 | bibcode = 1941PhRv...60...47K | url = http://web.ihep.su/dbserv/compas/src/kerst41/eng.pdf}}</ref><ref>{{Cite journal | last1 = Kerst | first1 = D. W. | author-link1 = Donald William Kerst | last2 = Serber | first2 = R. | author-link2 = Robert Serber | title = Electronic Orbits in the Induction Accelerator | journal = [[Physical Review]] | volume = 60 | issue = 1 | pages = 53–58 | date=Jul 1941 | doi = 10.1103/PhysRev.60.53 | bibcode = 1941PhRv...60...53K}}</ref>