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==World War II and the Manhattan Project==
==World War II and the Manhattan Project==
After the outbreak of [[World War II]] in Europe, Lawrence became drawn into military projects. He helped recruit staff for the {{MIT Radiation Laboratory]], where American physicists developed the [[cavity magnetron]] invented by Oliphant's team in Britain. The name of the new laboratory was deliberately copied from Lawrence's laboratory in Berkeley for security reasons. He also became involved in recreating staff for underwater sound laboratories to develop techniques for detecting German submarines.Meanwhile, work continued at Berkeley with cyclotron. [[Glenn Seaborge]] and [[Emilio Segré]] bombarded uranium to produce a new element, [[plutonium]], which they reported was [[fissile]].{{sfn|Alvarez|1970|p=274}}{{sfn|Childs|1968|pp=306-308}}
[[Image:Oak Ridge Y-12 Alpha Track.jpg|left|thumb|250px|Giant [[calutron]] plants developed at Lawrence's laboratory were used at [[Oak Ridge National Laboratory|Site X]] during World War II to [[Enriched_uranium#Enrichment_methods|purify uranium]] for use in the first [[atomic bomb]].]]


In September 1941, Oliphant met with Lawrence at Oppenheimer at Berkeley, where they showed him the site for the new 184-inch cyclotron. Oliphant in turn took the Americans to task for not following up the recommendations of the British [[Maud Report]], which advocated a program to develop an [[atomic bomb]].{{sfn|Herken|2002|pp=38-41}} Lawrence had already thought about the problem of [[uranium enrichment]], for only the [[uranium-235]] isotope is fissile. One way of doing this was with a [[mass spectrometer]], so Lawrence began converting his old 37-inch cyclotron into a giant mass spectrometer.{{sfn|Hewlett|Anderson|1962}pp=43-44}}
During [[World War II]], Lawrence eagerly helped to ramp up the American investigation of the possibility of a weapon utilizing [[nuclear fission]]. His Radiation Laboratory at U.C. Berkeley (known as the Rad Lab), became one of the major centers for wartime nuclear research, and it was Lawrence who first introduced [[J. Robert Oppenheimer]] into what would soon become the [[Manhattan Project]]. An early champion of the [[Enriched_uranium#Electromagnetic_isotope_separation|electromagnetic separation method]] to enrich [[uranium]] and increase its percentage of [[fissile]] U-235, Lawrence manufactured his magnetic [[calutron]]s — specialized forms of [[mass spectrometer]]s — for the massive isotope separation plants in [[Oak Ridge, Tennessee]]. It should be noted that Ernest Lawrence saw magnetic separation, or enrichment, as the best short term solution at hand, and it was Lawrence that demanded that the Government also simultaneously and generously sponsor research into chemical enrichment techniques that would eventually become more efficient. After successful completion and testing of the first atomic bomb at the Trinity test site in New Mexico, the question of how to use the now functional weapon on Japan became an issue for the scientists. While Oppenheimer favored no demonstration of the power of the new weapon to Japanese leaders, Lawrence felt that a demonstration would be wise. No demonstration was approved by the military. President Truman felt that to get the Japanese Military to surrender, and avoid the planned massive invasion of Japan with up to one million casualties predicted, the two remaining atomic bombs built through the Manhattan Project would be dropped on Japan to end the war in the Pacific.


Electromagnetic isotope separation was developed by Lawrence at the University of California Radiation Laboratory. This method employed devices known as [[calutron]]s, a hybrid of the standard laboratory [[mass spectrometer]] and cyclotron. The name was derived from the words "California", "university" and "cyclotron".{{sfn|Jones|1985|pp=117–119}} In the electromagnetic process, a magnetic field deflected charged particles according to mass.{{sfn|Smyth|1945|pp=164–165}} The process was neither scientifically elegant nor industrially efficient.{{sfn|Fine|Remington|1972|p=684}} Compared with a [[gaseous diffusion]] plant or a [[nuclear reactor]], an electromagnetic separation plant would consume more scarce materials, require more manpower to operate, and cost more to build. Nonetheless, the process was approved because it was based on proven technology and therefore represented less risk. Moreover, it could be built in stages, and would rapidly reach industrial capacity.{{sfn|Jones|1985|pp=117–119}}
Lawrence's secretary, [[Helen L. Seaborg|Helen Griggs]] married the future [[Nobel Prize in Chemistry]] winner, [[Glenn T. Seaborg]], in 1942, as the three of them made their way to work on the Manhattan Project in [[Chicago, Illinois]].

[[File:Oak Ridge Y-12 Alpha Track.jpg|left|thumb|300px|Giant Alpha I racetrack at Y-12|alt=A large oval-shaped structure.]]
Responsibility for the design and construction of the electromagnetic separation plant, which came to be called [[Y-12 National Security Complex|Y-12]], was assigned to Stone & Webster by the S-1 Committee in June 1942. The design called for five first stage processing units, known as Alpha racetracks, and two units for final processing, known as Beta racetracks. In September 1943 the director of the [[Manhattan Project]], [[Brigadier General (united States)|Brigadier General]] [[Leslie R. Groves, Jr.]], authorized construction of four more racetracks, known as Alpha II. Their construction began in February 1943.{{sfn|Jones|1985|pp=126–132}}

When the plant was started up for testing on schedule in October, the 14-ton vacuum tanks crept out of alignment because of the power of the magnets, and had to be fastened more securely. A more serious problem arose when the magnetic coils started shorting out. In December Groves ordered a magnet to be broken open, and handfuls of rust were found inside. Groves then ordered the racetracks to be torn down and the magnets sent back to the factory to be cleaned. A pickling plant was established on-site to clean the pipes and fittings.{{sfn|Fine|Remington|1972|p=684}} The second Alpha I was not operational until the end of January 1944, the first Beta and first and third Alpha I's came online in March, and the fourth Alpha I was operational in April. The four Alpha II racetracks were completed between July and October 1944.{{sfn|Jones|1985|pp=138–139}}

[[File:Y12 Calutron Operators.jpg|thumb|300px|Operators at their calutron control panels at Y-12. Gladys Owens, the woman seated in the foreground, did not know what she had been involved with until seeing this photo in a public tour of the facility fifty years later.<ref>{{cite web |url=http://smithdray1.net/angeltowns/or/go.htm |publisher=SmithDRay |title=The Calutron Girls |accessdate=22 June 2011}}</ref>|alt=A long corridor with many consoles with dials and switches, attended by women seated on high stools.]]
[[Tennessee Eastman]] was hired to manage Y-12 on the usual cost plus fixed fee basis, with a fee of $22,500 per month plus $7,500 per racetrack for the first seven racetracks and $4,000 per additional racetrack.{{sfn|Jones|1985|p=140}} The calutrons were initially operated by scientists from Berkeley to remove bugs and achieve a reasonable operating rate. They were then turned over to trained Tennessee Eastman operators who had only a high school education.{{sfn|Nichols|1987|p=131}}

Y-12 initially enriched the uranium-235 content to between 13% and 15%, and shipped the first few hundred grams of this to Los Alamos in March 1944. Only 1 part in 5,825 of the uranium feed emerged as final product. Much of the rest was splattered over equipment in the process. Strenuous recovery efforts helped raise production to 10% of the uranium-235 feed by January 1945. In February the Alpha racetracks began receiving slightly enriched (1.4%) feed from the new [[S-50 thermal diffusion plant]]. The next month it received enhanced (5%) feed from the [[K-25 gaseous diffusion plant]]. By April K-25 was producing uranium sufficiently enriched to feed directly into the Beta tracks.{{sfb|Jones|1985|pp=143–148}}

After successful completion and testing of the first atomic bomb at the Trinity test site in New Mexico, the question of how to use the now functional weapon on Japan became an issue for the scientists. While Oppenheimer favored no demonstration of the power of the new weapon to Japanese leaders, Lawrence felt that a demonstration would be wise. No demonstration was approved by the military. President Truman felt that to get the Japanese Military to surrender, and avoid the planned massive invasion of Japan with up to one million casualties predicted, the two remaining atomic bombs built through the Manhattan Project would be dropped on Japan to end the war in the Pacific.


==Post-war career and legacy==
==Post-war career and legacy==

Revision as of 02:14, 25 August 2013

Ernest O. Lawrence
Ernest O. Lawrence
Born(1901-08-08)August 8, 1901
Canton, South Dakota
DiedAugust 27, 1958(1958-08-27) (aged 57)
Palo Alto, California
NationalityAmerican
Alma materUniversity of South Dakota
University of Minnesota
Yale University
Known forInvention of the cyclotron
Manhattan Project
AwardsHughes Medal (1937)
Elliott Cresson Medal (1937)
Comstock Prize in Physics (1938)
Nobel Prize in Physics (1939)
Faraday Medal (1952)
Enrico Fermi Award (1957)
Scientific career
FieldsPhysics
InstitutionsUniversity of California, Berkeley
Yale University
Doctoral advisorWilliam F.G. Swann
Doctoral studentsEdwin McMillan
Chien-Shiung Wu
Milton S. Livingston
Kenneth Ross MacKenzie
Signature

Ernest Orlando Lawrence (August 8, 1901 – August 27, 1958) was an American scientist who won the Nobel Prize for Physics in 1939 for his invention of the cyclotron atom-smasher. He is also known for his work on uranium-isotope separation for the Manhattan Project, and for founding the Lawrence Berkeley Laboratory and the Lawrence Livermore Laboratory.

Lawrence had a long career at the University of California, Berkeley, where he was a Professor of Physics. Chemical element number 103 is named "lawrencium" in his honor. He was also the first recipient of the Sylvanus Thayer Award.[1]

Early life

Ernest Orlando Lawrence was born in Canton, South Dakota on August 8, 1901. His parents, Carl Gustavus and Gunda (née Jacobson) Lawrence, were both the offspring of Norwegian immigrants who had met while teaching at the high school in Canton, where his father was also the superintendent of schools. He had a younger brother, John H. Lawrence. Growing up, his best friend was Merle Tuve, who would also go on to become a highly accomplished nuclear physicist.[2]

Lawrence attended St. Olaf College in Minnesota, but he transferred to the University of South Dakota after his first year.[3] Lawrence completed his bachelor's degree in 1922,[4] and his Master of Arts (M.A.) degree in physics from the University of Minnesota in 1923 under the supervision of William Francis Gray Swann. For his master's thesis, Lawrence built an experimental apparatus that rotated an ellipsoid through a magnetic field.[5]

Lawrence followed Swann to the University of Chicago, and then to Yale University, where Lawrence completed his Doctor of Philosophy (Ph.D.) degree in physics in 1925 as a Sloane Fellow,[6] writing his doctoral thesis on the photoelectric effect in potassium vapour.[7][8] He was elected a member of Sigma Xi, and, on Swann's recommendation, received a National Research Council fellowship. Instead of using it to travel to Europe, remained at Yale University with Swann as a researcher.[9]

With Jesse Beams from the University of Virginia, Lawrence continued to research the photoelectric effect. They showed the photoelectrons appeared within 2 x 10-9 seconds of the photons striking the photoelectric surface—close to the limit of measurement at the time. They showed that by reducing the emission time by switch the light source on and off rapidly, the spectrum of energy emitted became broader, in conformance with Werner Heisenberg's uncertainty principle.[10]

Lawrence received offers of assistant professorships from the University of Washington and the University of California at a salary of $3,500 per annum. Yale promptly matched the offer of the assistant professorship, but at a salary of $3,000. Lawrence chose to stay at the more prestigious Yale,[11] but found that the appointment without having first been an instructor was resented by some of his fellow faculty, and did not necessarily lift his social status among people who were unimpressed by his South Dakota immigrant background.[12]

In 1928, Lawrence was hired as an Associate Professor of Physics at the University of California, and two years later he became a full Professor, becoming the youngest Professor at the University of California.[6] Robert Gordon Sproul, who became President of the University of California the day after Lawrence became a professor,[13] was a member of the Bohemian Club, and he sponsored Lawrence's membership in 1932. Through this club, Lawrence met William Henry Crocker, Edwin Pauley, and John Francis Neylan. They were influential men who helped him obtain money for his energetic nuclear particle investigations. There was great hope for medical uses to come from the development of particle physics, and this led to much of the early funding for advances Lawrence was able to obtain.[14]

While at Yale, Lawrence met Mary (Molly) Blumer, the eldest of four daughters of George Blumer, the Dean of the Yale School of Medicine. They became engaged in 1931,[15] and were married on May 14, 1932, at Trinity Church on the Green in New Haven, Connecticut.[16] They had six children: Eric, Margaret, Mary, Robert, Barbara and Susan. Molly's sister Elsie married Edwin McMillan in 1941.[15] Lawrence's closest friend in Berkeley was theoretical physicist Robert Oppenheimer.[17] Lawrence named his son Robert after Oppenheimer.[18]

The Developments of the Cyclotron

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, Lawrence glanced over a journal article by Rolf Widerøe,[19] and was intrigued by one of the diagrams.[20] The idea was to produce very high-energy particles required for atomic disintegration by means of a succession of very small "pushes." The device as depicted however, was laid out in a straight line using increasingly longer electrodes.[21]

Diagram of cyclotron operation from Lawrence's 1934 patent.

Lawrence saw that such 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.[22] He initially worked with Niels Edlefsen. Their first cyclotron was made out of brass, wire, and sealing wax and was only four inches in diameter—it could literally be held in one hand. It probably cost $25 in all.[23]

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 M. Stanley Livingston and David H. Sloan, who he set to work on developing Widerøe's accelerator and Edlefsen's cyclotron respectively. Both had their own financial support. Hiring good people and paying them little or nothing would prove to be a sound business model. Both designs proved practical, and by May 1931, Sloan's linear accelerator was able to accelerate ions to 1 MV.[24] Livingston had a greater technical challenge, but when he applied 1,800 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.[25]

In what would be become a recurring pattern, as soon as there was the first signs of success, Lawrence started planning a new, bigger machine. Lawrence and Livingston drew up a design for a 27-inch cyclotron in early 1932. The magnet for the $80011-inch cyclotron weighed 2 tons. Lawrence found an 80-ton magnet for the 27-inch.[26] In the cyclotron, Lawrence had a powerful scientific instrument, but this did not translate into scientific discovery. In April 1932, John Cockcroft and Ernest Walton at the Cavendish laboratory in England announced that they had bombarded lithium with protons and succeeded in transmuting it into helium. The energy required turned out to be quite low—well within the capability of the 11-inch cyclotron. On learning about it, Lawrence wired the Berkeley and asked for Cockcroft and Walton's results to be verified. It took the team until September to do so, mainly due to lack of detection apparatus.[27]

Through his increasingly larger machines, Lawrence was able to provide the crucial equipment needed for experiments in high energy physics. Around this device, Lawrence built up his Radiation Laboratory, which would become the world's foremost laboratory for the new field of nuclear physics research in the 1930s. He received a patent for the cyclotron in 1934,[28] which he assigned to the Research Corporation.[29] In February 1936, Harvard University's president, James B. Conant, made made attractive offers to Lawrence and Oppenheimer.[30] As a result, the Radiation Laboratory became an official department of the University of California on July 1, 1936, with Lawrence formally appointed its Director. The University agreed to make $20,000 a year available for its activities.[31]

Meeting at Berkeley concerning the planned 184-inch cyclotron (seen on the blackboard): Lawrence, Arthur Compton, Vannevar Bush, James B. Conant, Karl T. Compton, and Alfred Lee Loomis

Using the new 27-inch cyclotron, the team at Berkeley discovered that every element that they bombarded with recently-discovered deuterium emitted energy, and at the same range. They therefore postulated the existence of a new and hitherto unknown particle, and a possible source of limitless energy.[32] William Laurence of The New York Times described Lawrence as "a new miracle worker of science".[33] At Cockroft's invitation, Lawrence was invited to the 1933 Solvay Conference, to give a presentation on the cyclotron.[34] Lawrence ran into withering skepticism from James Chadwick, who suggested that what Lawrence's team was observing was contamination of their apparatus.[35]

After he returned to Berkeley, Lawrence mobilized his team to go painstakingly over the results in order to gather enough evidence to convince Chadwick. Meanwhile, at the Cavendish laboratory, Ernest Rutherford and Mark Oliphant found that deuterium fuses to form helium-3, which causes the effect that the cyclontroneers had observed. Not only was Chadwick correct in that they had been observing contamination, but they had overlooked another important discovery.[36] Leawrence pressed on with the creation of larger cyclotrons. The 27-inch cyclotron was superseded by a 37-inch cyclotron in June 1937.[37] In May 1939, the 60-inch cyclotron was started it. It was used to bombard iron and produced its first radioactive isotopes in June, and the first cancer patient received neutron therapy from it on November 20.[38]

Lawrence was awarded the Nobel Prize in Physics in November 1939 "for the invention and development of the cyclotron and for results obtained with it, especially with regard to artificial radioactive elements".[39] Not only was he the first at Berkeley to become a Nobel Laureate, he was also the first ever to be so honored while at a state-supported university. The award ceremony was held on February 29, 1940, in Berkeley, California due to World War II, in the auditorium of Wheeler Hall on the campus of the university with Lawrence receiving his medal from Carl E. Wallerstedt, Sweden's Consul General in San Francisco.[40] Robert W. Wood wrote to Lawrence and presciently noted "As you are laying the foundations for the the cataclysmic explosion of uranium... I'm sure old Nobel would approve."[41]

In March 1940, [Arthur Compton]], Vannevar Bush, James B. Conant, Karl T. Compton, and Alfred Lee Loomis travelled to Berkeley to discuss Lawrence's proposal for a 184-inch cyclotron with a 4,500-ton magnet that was estimated to cost $2.65 million. The Rockefeller Foundation put up $1.15 million to get the project started.[42]

World War II and the Manhattan Project

After the outbreak of World War II in Europe, Lawrence became drawn into military projects. He helped recruit staff for the {{MIT Radiation Laboratory]], where American physicists developed the cavity magnetron invented by Oliphant's team in Britain. The name of the new laboratory was deliberately copied from Lawrence's laboratory in Berkeley for security reasons. He also became involved in recreating staff for underwater sound laboratories to develop techniques for detecting German submarines.Meanwhile, work continued at Berkeley with cyclotron. Glenn Seaborge and Emilio Segré bombarded uranium to produce a new element, plutonium, which they reported was fissile.[43][44]

In September 1941, Oliphant met with Lawrence at Oppenheimer at Berkeley, where they showed him the site for the new 184-inch cyclotron. Oliphant in turn took the Americans to task for not following up the recommendations of the British Maud Report, which advocated a program to develop an atomic bomb.[45] Lawrence had already thought about the problem of uranium enrichment, for only the uranium-235 isotope is fissile. One way of doing this was with a mass spectrometer, so Lawrence began converting his old 37-inch cyclotron into a giant mass spectrometer.[46]

Electromagnetic isotope separation was developed by Lawrence at the University of California Radiation Laboratory. This method employed devices known as calutrons, a hybrid of the standard laboratory mass spectrometer and cyclotron. The name was derived from the words "California", "university" and "cyclotron".[47] In the electromagnetic process, a magnetic field deflected charged particles according to mass.[48] The process was neither scientifically elegant nor industrially efficient.[49] Compared with a gaseous diffusion plant or a nuclear reactor, an electromagnetic separation plant would consume more scarce materials, require more manpower to operate, and cost more to build. Nonetheless, the process was approved because it was based on proven technology and therefore represented less risk. Moreover, it could be built in stages, and would rapidly reach industrial capacity.[47]

A large oval-shaped structure.
Giant Alpha I racetrack at Y-12

Responsibility for the design and construction of the electromagnetic separation plant, which came to be called Y-12, was assigned to Stone & Webster by the S-1 Committee in June 1942. The design called for five first stage processing units, known as Alpha racetracks, and two units for final processing, known as Beta racetracks. In September 1943 the director of the Manhattan Project, Brigadier General Leslie R. Groves, Jr., authorized construction of four more racetracks, known as Alpha II. Their construction began in February 1943.[50]

When the plant was started up for testing on schedule in October, the 14-ton vacuum tanks crept out of alignment because of the power of the magnets, and had to be fastened more securely. A more serious problem arose when the magnetic coils started shorting out. In December Groves ordered a magnet to be broken open, and handfuls of rust were found inside. Groves then ordered the racetracks to be torn down and the magnets sent back to the factory to be cleaned. A pickling plant was established on-site to clean the pipes and fittings.[49] The second Alpha I was not operational until the end of January 1944, the first Beta and first and third Alpha I's came online in March, and the fourth Alpha I was operational in April. The four Alpha II racetracks were completed between July and October 1944.[51]

A long corridor with many consoles with dials and switches, attended by women seated on high stools.
Operators at their calutron control panels at Y-12. Gladys Owens, the woman seated in the foreground, did not know what she had been involved with until seeing this photo in a public tour of the facility fifty years later.[52]

Tennessee Eastman was hired to manage Y-12 on the usual cost plus fixed fee basis, with a fee of $22,500 per month plus $7,500 per racetrack for the first seven racetracks and $4,000 per additional racetrack.[53] The calutrons were initially operated by scientists from Berkeley to remove bugs and achieve a reasonable operating rate. They were then turned over to trained Tennessee Eastman operators who had only a high school education.[54]

Y-12 initially enriched the uranium-235 content to between 13% and 15%, and shipped the first few hundred grams of this to Los Alamos in March 1944. Only 1 part in 5,825 of the uranium feed emerged as final product. Much of the rest was splattered over equipment in the process. Strenuous recovery efforts helped raise production to 10% of the uranium-235 feed by January 1945. In February the Alpha racetracks began receiving slightly enriched (1.4%) feed from the new S-50 thermal diffusion plant. The next month it received enhanced (5%) feed from the K-25 gaseous diffusion plant. By April K-25 was producing uranium sufficiently enriched to feed directly into the Beta tracks.[55]

After successful completion and testing of the first atomic bomb at the Trinity test site in New Mexico, the question of how to use the now functional weapon on Japan became an issue for the scientists. While Oppenheimer favored no demonstration of the power of the new weapon to Japanese leaders, Lawrence felt that a demonstration would be wise. No demonstration was approved by the military. President Truman felt that to get the Japanese Military to surrender, and avoid the planned massive invasion of Japan with up to one million casualties predicted, the two remaining atomic bombs built through the Manhattan Project would be dropped on Japan to end the war in the Pacific.

Post-war career and legacy

After the war, Lawrence campaigned extensively for government sponsorship of large scientific programs. Lawrence was a forceful advocate of "Big Science" with its requirements for big machines and big money.

For his service to his country, Lawrence received the Enrico Fermi Award from the U.S. Atomic Energy Commission in 1957, and was the first recipient of the prestigious Sylvanus Thayer Award by the United States Military Academy in 1958. In 1937, he was elected a Fellow of the American Academy of Arts and Sciences.[56]

In July 1958, President Eisenhower requested that Lawrence travel to Geneva, Switzerland, to help negotiate a proposed treaty with the Soviet Union to ban nuclear weapons testing. Despite suffering from a serious flare-up of his chronic colitis, Lawrence decided to go, but he became ill while in Geneva, and was rushed to the hospital at Stanford University. Lawrence died one month later in Palo Alto, California, at the age of 57.

Just 23 days after his death, the Regents of the University of California voted to rename two of the university's nuclear research sites after Lawrence: the Lawrence Livermore and Lawrence Berkeley Laboratories. The Ernest Orlando Lawrence Award was established in his memory in 1959. Chemical element number 103, discovered at LBNL in 1961, is named "lawrencium" in his honor. In 1968 the Lawrence Hall of Science public science education center was established in honor of Ernest O. Lawrence, who had been throughout his career a passionate advocate of encouraging public interest in science, particularly among schoolchildren. The museum features a permanent exhibit devoted to Lawrence's life.

Notes

  1. ^ Information Office United States Military Academy West Point, New York (March 4, 1958). "Dr Ernest Orlando Lawrence". Retrieved 2008-03-07. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help)
  2. ^ Childs 1968, pp. 23–30.
  3. ^ Childs 1968, pp. 47–49.
  4. ^ Childs 1968, p. 61.
  5. ^ Childs 1968, pp. 63–68.
  6. ^ a b Alvarez 1970, pp. 253–254.
  7. ^ Alvarez 1970, p. 288.
  8. ^ Lawrence, Ernest Orlando (1925). "The photoelectric effect in potassium vapour as a function of the frequency of the light". Philosophical Magazine. 50 (296): 345–359. doi:10.1080/14786442508634745. {{cite journal}}: Unknown parameter |month= ignored (help)
  9. ^ Childs 1968, p. 93.
  10. ^ Alvarez 1970, p. 256.
  11. ^ Childs 1968, pp. 107–108.
  12. ^ Childs 1968, pp. 120–121.
  13. ^ Childs 1968, p. 256.
  14. ^ Brechin 1999, p. 312.
  15. ^ a b Alvarez 1970, p. 259.
  16. ^ Childs 1968, p. 182.
  17. ^ Herken 2002, pp. 11–15.
  18. ^ Childs 1968, p. 309.
  19. ^ Widerøe, R. (December 17, 1928). "Ueber Ein Neues Prinzip Zur Herstellung Hoher Spannungen". Archiv fuer Elektronik und Uebertragungstechnik (in German). 21 (4): 387.
  20. ^ "Breaking Through: A Century of Physics at Berkeley. 2. The Cyclotron". Bancroft Library, UC Berkeley. 2012-02-25. Archived from the original on February 25, 2012.
  21. ^ Heilbron & Seidel 1989, pp. 75–82.
  22. ^ Heilbron & Seidel 1989, pp. 83–88.
  23. ^ "Remembering E. O. Lawrence". Lawrence Livermore Laboratory. Retrieved August 25, 2013.
  24. ^ Heilbron & Seidel 1989, pp. 89–95.
  25. ^ Heilbron & Seidel 1989, pp. 95–100.
  26. ^ Herken 2002, pp. 5–7.
  27. ^ Heilbron & Seidel 1989, pp. 137–141.
  28. ^ US patent 1948384, Ernest O. Lawrence, "Method and apparatus for the acceleration of ions", issued 1934-02-20 
  29. ^ Heilbron & Seidel 1989, pp. 192–193.
  30. ^ Childs 1968, pp. 235–237.
  31. ^ Childs 1968, pp. 240, 248.
  32. ^ Heilbron & Seidel 1989, pp. 153–157.
  33. ^ Heilbron & Seidel 1989, p. 156.
  34. ^ Childs 1968, pp. 197–208.
  35. ^ Herken 2002, p. 10.
  36. ^ Heilbron & Seidel 1989, pp. 169–171.
  37. ^ Heilbron & Seidel 1989, p. 277.
  38. ^ Childs 1968, p. 288.
  39. ^ "The Nobel Prize in Physics 1939". The Nobel Foundation. Retrieved August 25, 2013.
  40. ^ Childs 1968, pp. 294–296.
  41. ^ Herken 2002, p. 27.
  42. ^ Childs 1968, p. 299.
  43. ^ Alvarez 1970, p. 274.
  44. ^ Childs 1968, pp. 306–308.
  45. ^ Herken 2002, pp. 38–41.
  46. ^ Hewlett & Anderson.
  47. ^ a b Jones 1985, pp. 117–119.
  48. ^ Smyth 1945, pp. 164–165.
  49. ^ a b Fine & Remington 1972, p. 684.
  50. ^ Jones 1985, pp. 126–132.
  51. ^ Jones 1985, pp. 138–139.
  52. ^ "The Calutron Girls". SmithDRay. Retrieved 22 June 2011.
  53. ^ Jones 1985, p. 140.
  54. ^ Nichols 1987, p. 131.
  55. ^ Jones (1985), pp. 143–148.
  56. ^ "Book of Members, 1780-2010: Chapter L" (PDF). American Academy of Arts and Sciences. Retrieved 13 April 2011.

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