Editing Mark Oliphant (section)

== Cavendish Laboratory ==
In 1925, Oliphant heard a speech given by the New Zealand physicist Sir [[Ernest Rutherford]], and he decided he wanted to work for him&nbsp;– an ambition that he fulfilled by earning a position at the [[Cavendish Laboratory]] at the [[University of Cambridge]] in 1927.{{sfn|Cockburn|Ellyard|1981|p=29}} He applied for an [[1851 Exhibition Scholarship]] on the strength of the research he had done on mercury with Burdon. It came with a living allowance of £250 per annum ({{Inflation|AU|500|1927|fmt=eq|r=-3|cursign=AUD$}}). When word came through that he had been awarded a fellowship, he [[electrical telegraph|wired]] Rutherford and [[Trinity College, Cambridge|Trinity College]], Cambridge. Both accepted him.{{sfn|Cockburn|Ellyard|1981|p=30}}

[[File:The Cavendish Laboratory - geograph.org.uk - 631839.jpg|thumb|The Cavendish Laboratory was the home of some of the great discoveries in physics. It was founded in 1874 by the [[Duke of Devonshire]] (Cavendish was his family name), and its first professor was [[James Clerk Maxwell]].<ref>{{cite web |url=http://www.phy.cam.ac.uk/history |title=The History of the Cavendish |publisher=[[University of Cambridge]] |access-date=15 August 2014 |archive-url=https://web.archive.org/web/20080708091429/http://www.phy.cam.ac.uk/history/ |archive-date=8 July 2008 |url-status=live  }}</ref>]]
Rutherford's Cavendish Laboratory was carrying out some of the most advanced research into [[nuclear physics]] in the world at the time. Oliphant was invited to afternoon tea by Rutherford and Lady Rutherford. He soon met other researchers at the Cavendish Laboratory, including [[Patrick Blackett]], [[Edward Bullard]], [[James Chadwick]], [[John Cockcroft]], [[Charles Drummond Ellis|Charles Ellis]], [[Peter Kapitza]], [[Egon Bretscher]], [[Philip Moon]] and [[Ernest Walton]]. There were two fellow Australians: [[Harrie Massey]] and [[John Keith Roberts]]. Oliphant would become especially close friends with Cockcroft. The laboratory had considerable talent but little money to spare, and tended to use a "string and sealing wax" approach to experimental equipment.{{sfn|Cockburn|Ellyard|1981|p=37}} Oliphant had to buy his own equipment, at one point spending £24 ({{Inflation|AU|24|1927|fmt=eq|r=-2|cursign=AUD$}}) of his allowance on a [[vacuum pump]].{{sfn|Cockburn|Ellyard|1981|p=41}}

Oliphant submitted his [[PhD]] thesis on ''The Neutralization of Positive Ions at Metal Surfaces, and the Emission of Secondary Electrons'' in December 1929.<ref name="AAS" /> For his ''[[oral exam|viva]]'', he was examined by Rutherford and Ellis. Receiving his degree was the attainment of a major life goal, but it also meant the end of his 1851 Exhibition Scholarship. Oliphant secured an 1851 Senior Studentship, of which there were five awarded each year. It came with a living allowance of £450 per annum ({{Inflation|AU|900|1929|fmt=eq|r=-3|cursign=A$}}) for two years, with the possibility of a one-year extension in exceptional circumstances, which Oliphant was also awarded.{{sfn|Cockburn|Ellyard|1981|pp=42–43}}

A son, Geoffrey Bruce Oliphant, was born 6 October 1930,{{sfn|Cockburn|Ellyard|1981|p=43}} but he died of [[meningitis]] on 5 September 1933. He was interred in an unmarked grave in the [[Ascension Parish Burial Ground, Cambridge|Ascension Parish Burial Ground]] in Cambridge, alongside Timothy Cockcroft, the infant son of Sir John and Lady Elizabeth Cockcroft, who had died the year before. Unable to have more children, the Oliphants adopted a four-month-old boy, Michael John, in 1936,{{sfn|Cockburn|Ellyard|1981|p=59}} and a daughter, Vivian, in 1938.{{sfn|Cockburn|Ellyard|1981|p=71}}

[[File:Sir Ernest Rutherfords laboratory, early 20th century. (9660575343).jpg|thumb|right|Sir Ernest Rutherford's laboratory, 1926]]
In 1932 and 1933, the scientists at the Cavendish Laboratory made a series of ground-breaking discoveries. Cockcroft and Walton bombarded [[lithium]] with high energy [[proton]]s and succeeded in [[nuclear transmutation|transmuting]] it into energetic [[atomic nucleus|nuclei]] of [[helium]]. This was one of the earliest experiments to change the [[atomic nucleus]] of one element to another by artificial means. Chadwick then devised an experiment that discovered a new, uncharged particle with roughly the same mass as the proton: the [[neutron]]. In 1933, Blackett discovered tracks in his [[cloud chamber]] that confirmed the existence of the [[positron]] and revealed the opposing spiral traces of positron–electron [[pair production]].{{sfn|Cockburn|Ellyard|1981|pp=45–46}}

Oliphant followed up the work by constructing a [[particle accelerator]] that could fire protons with up to 600,000 [[electronvolts]] of energy. He soon confirmed the results of Cockcroft and Walton on the [[artificial disintegration]] of the nucleus and positive [[ion]]s. He produced a series of six papers over the following two years.{{sfn|Cockburn|Ellyard|1981|pp=48–50}} In 1933, the Cavendish Laboratory received a gift from the American [[physical chemist]] [[Gilbert N. Lewis]] of a few drops of [[heavy water]]. The accelerator was used to fire [[heavy hydrogen]] nuclei (''[[deuteron]]s'', which Rutherford called ''diplons'') at various targets. Working with Rutherford and others, Oliphant thereby discovered the nuclei of [[helium-3]] (''helions'') and [[tritium]] (''tritons'').{{sfn|Cockburn|Ellyard|1981|pp=52–55}}<ref>{{cite journal |first1=M. L. E. |last1=Oliphant |first2=Lord |last2=Rutherford |author-link2=Lord Rutherford |date=3 July 1933 |doi=10.1098/rspa.1933.0117 |volume=141 |issue=843 |pages=259–281 |journal=Proceedings of the Royal Society A  |title=Experiments on the Transmutation of Elements by Protons |bibcode=1933RSPSA.141..259O |doi-access=free }}</ref><ref>{{cite journal |first1=M. L. E. |last1=Oliphant |first2=B. B. |last2=Kinsey |first3=Lord |last3=Rutherford |author-link3=Lord Rutherford |journal=Proceedings of the Royal Society A |title= The Transmutation of Lithium by Protons and by Ions of the Heavy Isotope of Hydrogen  |date=1 September 1933 |volume=141 |issue=845 |pages=722–733 |doi=10.1098/rspa.1933.0150 |bibcode=1933RSPSA.141..722O |doi-access=free }}</ref><ref>{{cite journal |first1=M. L. E. |last1=Oliphant |first2=P. |last2=Harteck |author-link2=Paul Harteck |first3=Lord |last3=Rutherford |author-link3=Lord Rutherford |journal=Proceedings of the Royal Society A |title= Transmutation Effects Observed with Heavy Hydrogen  |date=1 May 1934 |volume=144 |issue=853 |pages=692–703 |doi=10.1098/rspa.1934.0077 |bibcode=1934RSPSA.144..692O |doi-access=free }}</ref>

Oliphant used [[electromagnetic separation]] to separate the isotopes of lithium.<ref name="Electromagnetic separation" /> He was the first to experimentally demonstrate [[nuclear fusion]]. He found that when deuterons reacted with nuclei of helium-3, tritium or with other deuterons, the particles that were released had far more energy than they started with. [[Binding energy]] had been liberated from inside the nucleus.{{sfn|Cockburn|Ellyard|1981|pp=55–57}}<ref>{{cite journal |title=The Accurate Determination of the Energy Released in Certain Nuclear Transformations |first1=M. L. E. |last1=Oliphant |first2=A. R. |last2=Kempton |first3=Lord |last3=Rutherford |author-link3=Lord Rutherford |journal=Proceedings of the Royal Society A |volume=149 |pages=406–416 |issue=867 |doi=10.1098/rspa.1935.0071 |date=1 April 1935|bibcode = 1935RSPSA.149..406O |doi-access=free }}</ref> Following  [[Arthur Eddington]]'s 1920 prediction that energy released by [[nuclear fusion|fusing]] small nuclei together could provide the energy source that powers the stars,<ref>{{cite journal|author-link=Arthur Eddington|bibcode=1920Obs....43..341E|year=1920|title=The internal constitution of the stars|last=Eddington|first=Arthur S.|journal=The Observatory|volume=43|issue=1341|pages=341–358|doi=10.1126/science.52.1341.233|pmid=17747682|url=https://zenodo.org/record/1429642}}</ref> Oliphant speculated that nuclear fusion reactions might be what powered the sun.{{sfn|Cockburn|Ellyard|1981|pp=52–55}} With its higher [[cross section (physics)#Nuclear physics|cross section]], the deuterium–tritium nuclear fusion reaction became the basis of a [[hydrogen bomb]].<ref name=curiosity /> Oliphant had not foreseen this development:{{blockquote|... we had no idea whatever that this would one day be applied to make hydrogen bombs. Our curiosity was just curiosity about the structure of the nucleus of the atom, and the discovery of these reactions was purely, as the Americans would put it, coincidental.<ref name=curiosity /> }}

In 1934, Cockcroft arranged for Oliphant to become a fellow of [[St John's College, Cambridge]], which paid about £600 a year. When Chadwick left the Cavendish Laboratory for the [[University of Liverpool]] in 1935, Oliphant and Ellis both replaced him as Rutherford's assistant director for research. The job came with a salary of £600 ({{Inflation|AU|1200|1935|fmt=eq|cursign=AUD$|r=-3}}).{{sfn|Cockburn|Ellyard|1981|p=58}} With the money from St John's, this gave him a comfortable income.<ref name="AAS" /> Oliphant soon fitted out a new accelerator laboratory with a 1.23 [[Electronvolt|MeV]] generator at a cost of £6,000 ({{Inflation|AU|12000|1935|fmt=eq|cursign=AUD$|r=-4}}) while he designed an even larger 2&nbsp;MeV generator.{{sfn|Cockburn|Ellyard|1981|p=53}} He was the first to conceive of the proton [[synchrotron]], a new type of cyclic particle accelerator.<ref>{{cite journal | last1 = Rotblat | first1 = Józef| author-link = Józef Rotblat| title = Mark Oliphant (1901–2000) | journal = Nature | volume = 407 | issue = 6803| pages = 468 | year = 2000 | doi = 10.1038/35035202 | pmid =  11028988| s2cid = 36978443}}</ref> In 1937, he was elected to the [[Royal Society]]. When he died he was its longest-serving fellow.<ref name="AAS" />