Editing Ernest Lawrence (section)

=== Invention ===
The invention that brought Lawrence to international fame started out as a sketch on a scrap of a paper napkin. While sitting in the library one evening in 1929, Lawrence glanced over a journal article by [[Rolf Widerøe]],<ref>{{cite journal|last = Widerøe|first = R.|author-link=Rolf Widerøe |date =  December 17, 1928 |title=Ueber Ein Neues Prinzip Zur Herstellung Hoher Spannungen|journal = Archiv für Elektronik und Übertragungstechnik|language=de|volume = 21|issue = 4|pages = 387–406|doi = 10.1007/BF01656341|s2cid = 109942448}}</ref> and was intrigued by one of the diagrams.<ref>{{cite web|title=Breaking Through: A Century of Physics at Berkeley. 2. The Cyclotron. |publisher=Bancroft Library, UC Berkeley |date=February 25, 2012 |url=http://bancroft.berkeley.edu/Exhibits/physics/bigscience02.html |archive-url=https://web.archive.org/web/20120527183442/http://bancroft.berkeley.edu/Exhibits/physics/bigscience02.html |archive-date=May 27, 2012 |url-status=dead }}</ref> This depicted a device that produced [[Particle physics|high-energy particles]] by means of a succession of small "pushes". The device depicted was laid out in a straight line using increasingly longer electrodes.{{sfn|Heilbron|Seidel|1989|pp=75–82}} At the time, physicists were beginning to explore the [[atomic nucleus]]. In 1919, the New Zealand physicist [[Ernest Rutherford]] had fired alpha particles into [[nitrogen]] and had succeeded in knocking [[proton]]s out of some of the nuclei. But nuclei have a positive charge that repels other positively charged nuclei, and they are bound together tightly by a force that physicists were only just beginning to understand. To break them up, to disintegrate them, would require much higher energies, of the order of millions of volts.{{sfn|Heilbron|Seidel|1989|pp=46–49}}

[[File:Cyclotron patent.png|left|thumb|Diagram of cyclotron operation from Lawrence's 1934 patent|alt=Strange-looking schematic diagaram]]
Lawrence saw that such a [[particle accelerator]] would soon become too long and unwieldy for his university laboratory. In pondering a way to make the accelerator more compact, Lawrence decided to set a circular accelerating chamber between the poles of an electromagnet. The magnetic field would hold the charged protons in a spiral path as they were accelerated between just two semicircular electrodes connected to an alternating potential. After a hundred turns or so, the protons would impact the target as a beam of high-energy particles. Lawrence excitedly told his colleagues that he had discovered a method for obtaining particles of very high energy without the use of any high voltage.{{sfn|Heilbron|Seidel|1989|pp=83–88}} He initially worked with Niels Edlefsen. Their first [[cyclotron]] was made out of brass, wire, and sealing wax and was only {{convert|4|in|cm|spell=in}} in diameter—it could be held in one hand, and probably cost a total of $25 ({{Inflation|US|25|1934|r=-2|fmt=eq}}).<ref name=cfdmd /><ref name=stroc01>{{cite magazine|url=https://www.llnl.gov/str/October01/Lawrence.html |title=Remembering E. O. Lawrence |magazine=Science & Technology Review |publisher=[[Lawrence Livermore Laboratory]] |date=October 2001 |access-date=August 25, 2013 |archive-url=https://web.archive.org/web/20130615150500/https://www.llnl.gov/str/October01/Lawrence.html |archive-date=June 15, 2013 |url-status=dead}}</ref>

What Lawrence needed to develop the idea was capable graduate students to do the work. Edlefsen left to take up an assistant professorship in September 1930, and Lawrence replaced him with David H. Sloan and [[M. Stanley Livingston]],<ref name=eghhufr/> whom he set to work on developing Widerøe's accelerator and Edlefsen's cyclotron, respectively. Both had their own financial support. Both designs proved practical, and by May 1931, Sloan's [[linear accelerator]] was able to accelerate ions to 1 MeV.{{sfn|Heilbron|Seidel|1989|pp=89–95}} Livingston had a greater technical challenge, but when he applied 1,800&nbsp;V to his 11-inch cyclotron on January 2, 1931, he got 80,000-[[electron volt]] protons spinning around. A week later, he had 1.22 MeV with 3,000 V, more than enough for his PhD thesis on its construction.{{sfn|Heilbron|Seidel|1989|pp=95–100}}