Ernest Lawrence

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Ernest Lawrence
Ernest Lawrence.jpg
Lawrence in 1939
Born Ernest Orlando Lawrence
(1901-08-08)August 8, 1901
Canton, South Dakota
Died August 27, 1958(1958-08-27) (aged 57)
Palo Alto, California
Residence Berkeley, California
Nationality American
Fields Physics
Institutions University of California
Yale University
Alma mater University of South Dakota, B.A.
University of Minnesota, M.A.
Yale University, Ph.D.
Doctoral advisor William F.G. Swann
Doctoral students Edwin McMillan
Chien-Shiung Wu
Milton S. Livingston
Kenneth Ross MacKenzie
Known for Invention of the cyclotron
Manhattan Project
Notable awards Hughes Medal (1937)
Elliott Cresson Medal (1937)
Hughes Medal (1937)
Comstock Prize in Physics (1938)
Nobel Prize in Physics (1939)
Duddell Medal and Prize (1940)
Medal for Merit (1946)
Officer de la Legion d'Honneur (1948)
Faraday Medal (1952)
Enrico Fermi Award (1957)
Sylvanus Thayer Award (1958)
Spouse Mary K. "Molly" (Blumer) Lawrence (1910–2003)
(m. 1932–1958, his death)
Children 2 sons, 4 daughters
Signature

Ernest Orlando Lawrence (August 8, 1901 – August 27, 1958) was a pioneering American nuclear scientist, winner of the Nobel Prize for Physics in 1939 for his invention of the cyclotron. 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.[1][2]

A graduate of the University of South Dakota and University of Minnesota,[1] Lawrence completed his Doctor of Philosophy degree in physics at Yale in 1925. In 1928, he was hired as an associate professor of physics at the University of California, becoming the youngest full professor there two years later. In its library one evening, Lawrence was intrigued by a diagram of an accelerator that produced high-energy particles. He contemplated how it could be made compact, and came up with an idea for a circular accelerating chamber between the poles of an electromagnet. The result was the first cyclotron. Lawrence went on to build a series of ever larger and more expensive cyclotrons. His Radiation Laboratory became an official department of the University of California in 1936, with Lawrence as its director.

During World War II, Lawrence developed electromagnetic isotope separation at the Radiation Laboratory. It used devices known as calutrons, a hybrid of the standard laboratory mass spectrometer and cyclotron. A huge electromagnetic separation plant was built at Oak Ridge, Tennessee, which came to be called Y-12. The process was inefficient, but it worked.

After the war, Lawrence campaigned extensively for government sponsorship of large scientific programs, and was a forceful advocate of "Big Science", with its requirements for big machines and big money. Lawrence strongly backed Edward Teller's campaign for a second nuclear weapons laboratory, which Lawrence located in Livermore, California.[3] After his death, the Regents of the University of California renamed the Lawrence Livermore National Laboratory and Lawrence Berkeley National Laboratory after him. Chemical element number 103 was named lawrencium in his honor after its discovery at Berkeley in 1961.

Early life[edit]

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.[4]

Lawrence attended the public schools of Canton and Pierre, then enrolled at St. Olaf College in Northfield, Minnesota, but transferred after a year to the University of South Dakota in Vermillion.[5] He completed his bachelor's degree in chemistry in 1922,[6] 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.[7]

Lawrence followed Swann to the University of Chicago, and then to Yale University in New Haven, Connecticut, where Lawrence completed his Doctor of Philosophy (Ph.D.) degree in physics in 1925 as a Sloane Fellow,[8] writing his doctoral thesis on the photoelectric effect in potassium vapor.[9][10] 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, he remained at Yale University with Swann as a researcher.[11]

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. 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.[12]

Lawrence received offers of assistant professorships from the University of Washington in Seattle 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,[13] 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 unimpressed by his South Dakota immigrant background.[14]

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 university's youngest professor.[8] Robert Gordon Sproul, who became university president the day after Lawrence became a professor,[15] 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.[16]

While at Yale, Lawrence met Mary Kimberly (Molly) Blumer (1910–2003), the eldest of four daughters of George Blumer, the dean of the Yale School of Medicine.[17][18] They first met in 1926 and became engaged in 1931,[19] and were married on May 14, 1932, at Trinity Church on the Green in New Haven, Connecticut.[20] They had six children: Eric, Margaret, Mary, Robert, Barbara, and Susan.[17][21] Molly's sister Elsie married Edwin McMillan in 1941.[19] Lawrence named his son Robert after theoretical physicist Robert Oppenheimer, his closest friend in Berkeley.[22][23][24]

The developments of the cyclotron[edit]

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,[25] and was intrigued by one of the diagrams.[26] This depicted a device that produced high-energy particles required for atomic disintegration by means of a succession of small "pushes." The device depicted was laid out in a straight line using increasingly longer electrodes.[27]

Diagram of cyclotron operation from Lawrence's 1934 patent.

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.[28] He initially worked with Niels Edlefsen. Their first cyclotron was made out of brass, wire, and sealing wax and was only four inches (10 cm) in diameter—it could literally be held in one hand, and probably cost $25 in all.[21][29]

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[24] 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. Both designs proved practical, and by May 1931, Sloan's linear accelerator was able to accelerate ions to 1 MeV.[30] 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 on its construction.[31]

Meeting at Berkeley in 1940 concerning the planned 184-inch (4.67 m) cyclotron (seen on the blackboard): Lawrence, Arthur Compton, Vannevar Bush, James B. Conant, Karl T. Compton, and Alfred Lee Loomis

In what would be become a recurring pattern, as soon as there was the first sign of success, Lawrence started planning a new, bigger machine. Lawrence and Livingston drew up a design for a 27-inch (69 cm) cyclotron in early 1932. The magnet for the $800 11-inch cyclotron weighed 2 tons, but Lawrence found a massive 80-ton magnet for the 27-inch that had originally been built during World War I to power a transatlantic radio link, but was now rusting in a junkyard in Palo Alto.[32][33] In the cyclotron, he 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 adequate detection apparatus.[34]

Although important discoveries continued to elude Lawrence's Radiation Laboratory, mainly due to its focus on the development of the cyclotron rather than its scientific use, through his increasingly larger machines, Lawrence was able to provide crucial equipment needed for experiments in high energy physics. Around this device, he built what became 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,[35] which he assigned to the Research Corporation.[36] In February 1936, Harvard University's president, James B. Conant, made attractive offers to Lawrence and Oppenheimer.[37] In response, the Radiation Laboratory became an official department of the University of California on July 1, 1936, with Lawrence formally appointed its director, and the University agreed to make $20,000 a year available for its activities.[38]

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.[39] William Laurence of The New York Times described Lawrence as "a new miracle worker of science".[40] At Cockroft's invitation, Lawrence was invited to the 1933 Solvay Conference, to give a presentation on the cyclotron.[41] Lawrence ran into withering skepticism from James Chadwick, who suggested that what Lawrence's team was observing was contamination of their apparatus.[42]

The 60-inch (1.52 m) cyclotron soon after completion in 1939. The key figures in its development and use are shown, standing, left to right: D. Cooksey, D. Corson, Lawrence, R. Thornton, J, Backus, W.S. Sainsbury. In the background are Luis Walter Alvarez and Edwin McMillan.

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, of nuclear fusion.[43] Lawrence pressed on with the creation of larger cyclotrons. The 27-inch cyclotron was superseded by a 37-inch cyclotron in June 1937.[44] 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.[45]

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".[46] He was the first at Berkeley as well as the first South Dakotan to become a Nobel Laureate, and the first 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. Lawrence received his medal from Carl E. Wallerstedt, Sweden's Consul General in San Francisco.[47] Robert W. Wood wrote to Lawrence and presciently noted "As you are laying the foundations for the cataclysmic explosion of uranium... I'm sure old Nobel would approve."[48]

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.[49]

World War II and the Manhattan Project[edit]

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 recruiting staff for underwater sound laboratories to develop techniques for detecting German submarines. Meanwhile, work continued at Berkeley with cyclotrons. In December 1940, Glenn T. Seaborg and Emilio Segré used the 60-inch (150 cm) cyclotron to bombard with deuterons uranium-238 producing a new element, Neptunium-238, which decayed by beta emission to form plutonium-238. The discovery of plutonium was kept secret until a year after the end of World War II after the discovery that one of its isotopes, plutonium-239, could undergo nuclear fission in a way that might be useful in an atomic bomb.[50][51][52]

A large oval-shaped structure.
Giant electromagnet Alpha I racetrack for uranium enrichment at Y-12 plant, Oak Ridge, Tennessee, circa 1944-45. The calutrons Lawrence developed are located around the ring.

In September 1941, Oliphant met with Lawrence and Oppenheimer at Berkeley, where they showed him the site for the new 184-inch (4.7 m) cyclotron. Oliphant in turn took the Americans to task for not following up the recommendations of the British MAUD Committee, which advocated a program to develop an atomic bomb.[53] Lawrence had already thought about the problem of separating the fissile isotope uranium-235 from uranium-238, a process known today as uranium enrichment. Separating uranium isotopes was difficult because the two isotopes have very nearly identical chemical properties, and could only be separated gradually using small mass differences. Separating these isotopes with a mass spectrometer was one of the technologies developed to produce weapon-grade uranium-235, so Lawrence began converting his old 37-inch cyclotron into a giant mass spectrometer.[54] It was on Lawrence's recommendation that the director of the Manhattan Project, Brigadier General Leslie R. Groves, Jr., appointed Oppenheimer as head of the Los Alamos Laboratory.[55]

Schematic diagram of uranium isotope separation in a calutron.

Electromagnetic isotope separation was developed by Lawrence at the Radiation Laboratory. It used devices known as calutrons, a hybrid of two laboratory instruments, the mass spectrometer and cyclotron. The name was derived from the words "California", "university" and "cyclotron".[56] On November 1943, Lawrence's team at Berkeley was bolstered by 29 British scientists, including Oliphant.[57][58] In the electromagnetic process, a magnetic field deflected charged particles according to mass.[59] The process was neither scientifically elegant nor industrially efficient.[60] 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.[56]

Responsibility for the design and construction of the electromagnetic separation plant at Oak Ridge, Tennessee, which came to be called Y-12, was assigned to Stone & Webster. 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 Groves authorized construction of four more racetracks, known as Alpha II.[61]

When the plant was started up for testing on schedule in October 1943, 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.[60]

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.[62]

Tennessee Eastman was hired to manage Y-12.[63] 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 laboratory in March 1944.[64] Only 1 part in 5,825 of the uranium feed emerged as final product. 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 1945 K-25 was producing uranium sufficiently enriched to feed directly into the Beta tracks.[64]

On July 16, 1945, Lawrence observed the Trinity nuclear test of the first atomic bomb with Chadwick and Charles A. Thomas. Few were more excited at its success than Lawrence.[65] 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 strongly that a demonstration would be wise. Nonetheless, when a uranium bomb was used without warning in the atomic bombing of Hiroshima, Lawrence felt great pride in his accomplishment.[66]

Lawrence hoped that the Manhattan Project would develop improved calutrons and construct Alpha III racetracks, but they were judged to be uneconomical.[67] The Alpha tracks were closed down in September 1945. Although performing better than ever,[68] they could not compete with K-25 and the new K-27, which commenced operation in January 1946. In December, the Y-12 plant was closed, thereby cutting the Tennessee Eastman payroll from 8,600 to 1,500 and saving $2 million a month.[69] Staff numbers at the Radiation laboratory fell from 1,086 in May 1945 to 424 by the end of the year.[70]

Post-war career and legacy[edit]

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. In 1946, Lawrence asked the Manhattan Project for over $2 million for research at the Radiation Laboratory. Groves approved the money, but cut a number of programs, including Seaborg's proposal for a "hot" radiation laboratory in densely populated Berkeley, and John Lawrence's for production of medical isotopes, because this need could now be better met from nuclear reactors. One obstacle was the University of California, which was eager to divest its wartime military obligations. Lawrence and Groves managed to persuade Sproul to accept a contract extension.[71]

Responsibility for the national laboratories passed to the newly created Atomic Energy Commission on 1 January 1947.[72] In 1947, Lawrence asked for $15 million for his projects, which included a new linear accelerator and a new gigaelectronvolt synchrotron which became known as the bevatron. Unfortunately, University of California's contract to run the Los Alamos laboratory was due to expire on July 1, 1948, and some board members wished to divest the university of the responsibility for running a site outside California. After some negotiation, the university agreed to extend the contract for the Los Alamos National Laboratory for four more years, and to appoint Norris Bradbury, who had replaced Oppenheimer as its director on October 1945, as a professor.[73]

To most of his colleagues, Lawrence appeared to have almost an aversion to mathematical thought. He had a most unusual intuitive approach to involved physical problems, and when explaining new ideas to him, one quickly learned not to befog the issue by writing down the differential equation that might appear to clarify the situation. Lawrence would say something to the effect that he didn't want to be bothered by the mathematical details, but "explain the physics of the problem to me." One could live close to him for years, and think of him as being almost mathematically illiterate, but then be brought up sharply to see how completely he retained his skill in the mathematics of classical electricity and magnetism.

Luis Alvarez [74]

The 184-inch cyclotron was completed with wartime dollars from the Manhattan Project. It incorporated new ideas by Ed McMillan, and was completed as a synchrotron.[75] It commenced operation on November 13, 1946.[76] For the first time since 1935, Lawrence actively participated in the experiments, working unsuccessfully with Eugene Gardner in an attempt to create recently discovered pi mesons with the synchrotron. César Lattes then used the apparatus they had created to find negative pi mesons in 1948.[77]

In the chilly Cold War climate at the University of California, Lawrence was forced to defend Radiation Laboratory staff members like Robert Serber who were investigated by the University's Personnel Security Board. Lawrence barred Robert Oppenheimer's brother Frank from the Radiation Laboratory, damaging his relationship with Robert.[78] An acrimonious loyalty oath campaign drove away faculty members.[79]

Lawrence was alarmed by the Soviet Union's first nuclear test in August 1949. The proper response, he concluded, was an all-out effort to build a bigger nuclear weapon: the hydrogen bomb.[80] To create the tritium and the then-difficult to produce plutonium it required, Lawrence proposed to use accelerators to produce neutrons instead of nuclear reactors.[81] He first proposed the construction of Mark-I, a prototype $7 million, 25 MeV linear accelerator, codenamed Materials Test Accelerator (MTA), mainly used to produce polonium for the nuclear weapon program.[81][82] He was soon talking about a new, even larger MTA known as the Mark II which could produce tritium or plutonium from depleted uranium-238. Serber and Segré attempted in vain to explain the technical problems that made it impractical, but Lawrence felt that they were being unpatriotic.[83][84]

Lawrence strongly backed Edward Teller's campaign for a second nuclear weapons laboratory, which Lawrence proposed to locate with the MTA Mark I at Livermore, California. Lawrence and Teller had to argue their case not only with the Atomic Energy Commission, which did not want it, and the Los Alamos National Laboratory, which was implacably opposed, but with proponents who felt that Chicago was the obvious site for the new laboratory.[3] The new laboratory at Livermore was finally approved on July 17, 1952. The Mark II MTA was cancelled at the same time. By this time, the Atomic Energy Commission had spent $45 million on the Mark I, which had commenced operation. By this time the Brookhaven National Laboratory's Cosmotron was already in operation, and had generated a 1 GeV beam.[85]

For his service to his country, Lawrence received the Enrico Fermi Award from the Atomic Energy Commission in 1957,[86] and was the first recipient of the prestigious Sylvanus Thayer Award by the United States Military Academy in 1958.[87] 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 ulcerative colitis, Lawrence decided to go, but he became ill while in Geneva, and was rushed to the hospital at Stanford University.[88] Surgeons removed much of his large intestine, but found other problems, including severe atherosclerosis of the superior mesenteric artery. Large quantities of blood were transfused during and after surgery. The doctors did not believe that he regained consciousness, but Molly claimed that he had spoken to her.[89] He died in Palo Alto Hospital on August 27, 1958.[90] Molly did not want a public funeral, but agreed to a memorial service at the First Congregationalist Church in Berkeley. President Clark Kerr delivered the eulogy.[89]

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 National Laboratory and Lawrence Berkeley National Laboratory.[91] The Ernest Orlando Lawrence Award was established in his memory in 1959.[92] Chemical element number 103, discovered at the Lawrence Berkeley National Laboratory in 1961, was named lawrencium in his honor.[93] In 1968 the Lawrence Hall of Science public science education center was established in his honor.[94]

In the 1980s, Lawrence's widow petitioned the University of California Board of Regents on several occasions to remove her husband's name from the Livermore laboratory, due to its focus on nuclear weapons.[95][96][97][98] She outlived her husband by more than 44 years and died in Walnut Creek at the age of 92 on January 6, 2003.[17][18]

Notes[edit]

  1. ^ a b "Inventor of cyclotron dies after surgery". Eugene Register-Guard. Associated Press. August 28, 1958. p. 5b. 
  2. ^ Berdahl, Robert M. (December 10, 2001). "The Lawrence Legacy". Vermillion, South Dakota: University of California, Berkeley. Office of the Chancellor. Retrieved May 9, 2014. 
  3. ^ a b Herken 2002, pp. 244–247.
  4. ^ Childs 1968, pp. 23–30.
  5. ^ Childs 1968, pp. 47–49.
  6. ^ Childs 1968, p. 61.
  7. ^ Childs 1968, pp. 63–68.
  8. ^ a b Alvarez 1970, pp. 253–254.
  9. ^ Alvarez 1970, p. 288.
  10. ^ Lawrence, Ernest Orlando (August 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. 
  11. ^ Childs 1968, p. 93.
  12. ^ Alvarez 1970, p. 256.
  13. ^ Childs 1968, pp. 107–108.
  14. ^ Childs 1968, pp. 120–121.
  15. ^ Childs 1968, p. 256.
  16. ^ Brechin 1999, p. 312.
  17. ^ a b c Yarris, Lynn (January 8, 2003). "Lab mourns death of Molly Lawrence, widow of Ernest O. Lawrence". Lawrence Berkeley National Laboratory. Retrieved May 9, 2014. 
  18. ^ a b "Obituaries: Mary Lawrence". The Berkleyan. University of California. January 15, 2003. Retrieved May 9, 2014. 
  19. ^ a b Alvarez 1970, p. 259.
  20. ^ Childs 1968, p. 182.
  21. ^ a b Allen, John F. (August 29, 1958). "Cyclotron father's death mourned". Milwaukee Sentinel. p. 13, part 1. 
  22. ^ Childs 1968, p. 309.
  23. ^ Herken 2002, pp. 11–15.
  24. ^ a b Kiessling, E.C. (December 17, 1968). "Even geniuses have human frailties". Milwaukee Journal. p. 24, part 1. 
  25. ^ Widerøe, R. (December 17, 1928). "Ueber Ein Neues Prinzip Zur Herstellung Hoher Spannungen". Archiv fuer Elektronik und Uebertragungstechnik (in German) 21 (4): 387. 
  26. ^ "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. 
  27. ^ Heilbron & Seidel 1989, pp. 75–82.
  28. ^ Heilbron & Seidel 1989, pp. 83–88.
  29. ^ "Remembering E. O. Lawrence". Science & Technology Review. Lawrence Livermore Laboratory. October 2001. Retrieved August 25, 2013. 
  30. ^ Heilbron & Seidel 1989, pp. 89–95.
  31. ^ Heilbron & Seidel 1989, pp. 95–100.
  32. ^ Herken 2002, pp. 5–7.
  33. ^ "The Rad Lab – Ernest Lawrence and the Cyclotron". American Institute of Physics. Retrieved September 22, 2013. 
  34. ^ Heilbron & Seidel 1989, pp. 137–141.
  35. ^ US patent 1948384, Ernest O. Lawrence, "Method and apparatus for the acceleration of ions", issued 1934-02-20 
  36. ^ Heilbron & Seidel 1989, pp. 192–193.
  37. ^ Childs 1968, pp. 235–237.
  38. ^ Childs 1968, pp. 240, 248.
  39. ^ Heilbron & Seidel 1989, pp. 153–157.
  40. ^ Heilbron & Seidel 1989, p. 156.
  41. ^ Childs 1968, pp. 197–208.
  42. ^ Herken 2002, p. 10.
  43. ^ Heilbron & Seidel 1989, pp. 169–171.
  44. ^ Heilbron & Seidel 1989, p. 277.
  45. ^ Childs 1968, p. 288.
  46. ^ "The Nobel Prize in Physics 1939". The Nobel Foundation. Retrieved August 25, 2013. 
  47. ^ Childs 1968, pp. 294–296.
  48. ^ Herken 2002, p. 27.
  49. ^ Childs 1968, p. 299.
  50. ^ Alvarez 1970, p. 274.
  51. ^ Childs 1968, pp. 306–308.
  52. ^ Glenn T. Seaborg. "The plutonium story". Lawrence Berkeley Laboratory, University of California. LBL-13492, DE82 004551. 
  53. ^ Herken 2002, pp. 38–41.
  54. ^ Hewlett & Anderson 1962, pp. 43–44.
  55. ^ Childs 1968, pp. 337–339.
  56. ^ a b Jones 1985, pp. 117–119.
  57. ^ Childs 1968, p. 347.
  58. ^ Jones 1985, p. 124.
  59. ^ Childs 1968, p. 312.
  60. ^ a b Fine & Remington 1972, p. 684.
  61. ^ Jones 1985, pp. 126–132.
  62. ^ "The Calutron Girls". SmithDRay. Retrieved 22 June 2011. 
  63. ^ Jones 1985, p. 140.
  64. ^ a b Jones 1985, pp. 143–148.
  65. ^ Childs 1968, pp. 358–359.
  66. ^ Childs 1968, pp. 360–365.
  67. ^ Herken 2002, p. 128.
  68. ^ Hewlett & Anderson 1962, p. 624.
  69. ^ Hewlett & Anderson 1962, pp. 630, 646.
  70. ^ Childs 1968, p. 370.
  71. ^ Herken 2002, p. 168.
  72. ^ Herken 2002, p. 170.
  73. ^ Herken 2002, pp. 176, 182–183.
  74. ^ Alvarez 1970, p. 253.
  75. ^ Childs 1968, pp. 370–371.
  76. ^ Childs 1968, p. 387.
  77. ^ Alvarez 1970, pp. 277–279.
  78. ^ Herken 2002, pp. 190–192.
  79. ^ Herken 2002, pp. 220–222.
  80. ^ Herken 2002, pp. 200–202.
  81. ^ a b Heilbron; Seidel, Robert W.; Wheaton, Bruce R. (1981). "Lawrence and His Laboratory – A historian's view of the Lawrence year". Lawrence Berkeley National Laboratory. Retrieved 5 October 2013.  |chapter= ignored (help)
  82. ^ Herken 2002, p. 220.
  83. ^ Herken 2002, pp. 234–235.
  84. ^ Heilbron; Seidel, Robert W.; Wheaton, Bruce R. (1981). "Lawrence and His Laboratory – A historian's view of the Lawrence year". Lawrence Berkeley National Laboratory. Retrieved 5 October 2013.  |chapter= ignored (help)
  85. ^ Herken 2002, p. 256.
  86. ^ Childs 1968, pp. 508–510.
  87. ^ Childs 1968, pp. 517–518.
  88. ^ Herken 2002, pp. 325–325.
  89. ^ a b Childs 1968, pp. 532–534.
  90. ^ Alvarez 1970, p. 283.
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References[edit]

External links[edit]

Preceded by
none
Sylvanus Thayer Award
1958
Succeeded by
John Foster Dulles