John Cockcroft

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For the politician, see John Cockcroft (politician). For the cardiologist, see John R. Cockcroft.

Sir
John Cockcroft
St. John's College, Cambridge (BA, PhD)
Known forSplitting the atom
Awards
Scientific career
FieldsPhysics
InstitutionsAtomic Energy Research Establishment
Thesis On phenomena occurring in the condensation of molecular streams on surfaces  (1928)
Academic advisorsErnest Rutherford
1st Master of Churchill College, Cambridge
In office
1959–1967
Succeeded bySir William Hawthorne

Sir John Douglas Cockcroft

CBE FRS (27 May 1897 – 18 September 1967) was a British physicist who shared with Ernest Walton the Nobel Prize in Physics in 1951 for splitting the atomic nucleus, and was instrumental in the development of nuclear power
.

After service on the

St. John's College, Cambridge, where he sat the tripos exam in June 1924, becoming a wrangler. Ernest Rutherford accepted Cockcroft as a research student at the Cavendish Laboratory, and Cockcroft completed his doctorate under Rutherford's supervision in 1928. With Ernest Walton and Mark Oliphant he built what became known as a Cockcroft–Walton generator. Cockcroft and Walton used this to perform the first artificial disintegration of an atomic nucleus
, a feat popularly known as splitting the atom.

During the

atomic bomb could be technically feasible, and of the MAUD Committee which succeeded it. In 1940, as part of the Tizard Mission, he shared British technology with his counterparts in the United States. Later in the war, the fruits of the Tizard Mission came back to Britain in the form of the SCR-584 radar set and the proximity fuze, which were used to help defeat the V-1 flying bomb. In May 1944, he became director of the Montreal Laboratory, and oversaw the development of the ZEEP and NRX reactors, and the creation of the Chalk River Laboratories
.

After the war Cockcroft became the director of the

Windscale. Under his direction it took part in frontier fusion research, including the ZETA program. His insistence that the chimney stacks of the Windscale reactors be fitted with filters was mocked as Cockcroft's Folly until the core of one of the reactors ignited and released radionuclides during the Windscale fire
of 1957.

From 1959 to 1967, he was the first Master of Churchill College, Cambridge. He was also chancellor of the Australian National University in Canberra from 1961 to 1965.

Early years

John Douglas Cockcroft, also known as "Johnny W.", was born in

Church of England school in Walsden from 1901 to 1908, at Todmorden Elementary School from 1908 to 1909, and at Todmorden Secondary School from 1909 to 1914,[2][4] where he played football and cricket. Among the girls at the school was his future wife, Eunice Elizabeth Crabtree. In 1914, he won a County Major Scholarship, West Riding of Yorkshire, to the Victoria University of Manchester, where he studied mathematics.[4][5]

The

Kinmel Camp in Wales. He enlisted in the British Army on 24 November 1915. On 29 March 1916, he joined the 59th Training Brigade, Royal Field Artillery, where he was trained as a signaller. He was then posted to B Battery, 92nd Field Artillery Brigade, one of the units of the 20th (Light) Division, on the Western Front.[6]

Cockcroft participated in the

Officer Candidate School in Weedon Bec in Northamptonshire, where he was trained as a field artillery officer.[7] He was commissioned as a lieutenant in the Royal Field Artillery on 17 October 1918.[8]

After the war ended, Cockcroft was released from the Army in January 1919. He elected not to return to the Victoria University of Manchester, but to study

MSc thesis on the "Harmonic Analysis for Alternating Currents" in June 1922.[9]

Walker then suggested Cockcroft sit for a scholarship to

St. John's College, Cambridge, Walker's alma mater. Cockcroft was successful, winning a £30 scholarship and a £20 bursary awarded to undergraduates of limited means. Metropolitan Vickers gave him £50 subject to his returning after completing his degree. Walker and an aunt made up the balance of the £316 fee. As a graduate of another university, he was allowed to skip the first year of the tripos. He sat the tripos exam in June 1924, achieved a B* as a wrangler, and was awarded his BA degree.[10]

Cockcroft married Elizabeth Crabtree on 26 August 1925,[4] in a ceremony at the Bridge Street United Methodist Church in Todmorden.[11] They had six children. The first, a boy known as Timothy, died in infancy. They subsequently had four daughters, Joan Dorothea (Thea), Jocelyn, Elisabeth Fielden and Catherine Helena; and another son, Christopher Hugh John.[4]

Nuclear research

House in Walsden in West Yorkshire where John Cockcroft lived from the age of two until he was 28 years old

Peter Kapitza, who was working on the physics of magnetic fields in extremely low temperatures. Cockcroft helped with the design and construction of helium liquefiers.[2]

In 1919, Rutherford had succeeded in disintegrating

Cockcroft–Walton accelerator. Mark Oliphant designed a proton source for them. A crucial moment came when Cockcroft read a paper by George Gamow on quantum tunnelling. Cockcroft realised that as a result of this phenomenon, the desired effect could be achieved with much lower voltages than first thought. In fact, he calculated that protons with energy of just 300,000 electronvolts would be able to penetrate a boron nucleus. Cockcroft and Walton worked on their accelerator for the next two years. Rutherford obtained a £1,000 grant from the University of Cambridge for them to buy a transformer and other equipment they needed.[2][4][15][16]

Cockcroft was elected a Fellow of St. John's College on 5 November 1928.[17] He and Walton began operating their accelerator in March 1932, bombarding lithium and beryllium with high-energy protons. They expected to see gamma rays, which French scientists had reported, but none were found. In February 1932, James Chadwick demonstrated that what had been observed were actually neutrons. Cockcroft and Walton then switched to looking for alpha particles instead. On 14 April 1932, Walton bombarded a lithium target and noticed what he thought might be alpha particles. Cockcroft and then Rutherford were summoned, and confirmed that this was indeed the case. That evening, Cockcroft and Walton met at Rutherford's home and produced a letter for Nature in which they announced their results, the first artificial disintegration of an atomic nucleus, which can be described thus:[18]

7
3Li
 +
p
 → 24
2He
 + 17.2 MeV

This feat was popularly known as splitting the atom.

carbon-11 and nitrogen-13.[21][22][23][24][25][26]

Cockcroft-Walton voltage multiplier circuit

In 1929, Cockcroft was appointed a Supervisor in Mechanical Sciences at St John's College. He was appointed a Supervisor in Physics in 1931, and in 1933 became the junior bursar, making him responsible for the upkeep of the buildings, many of which were suffering from neglect. The college gatehouse had to be partly taken down in order to repair damage done by deathwatch beetles, and Cockcroft supervised rewiring of the electrics. In 1935, Rutherford appointed him the director of research at the Mond Laboratory after Kapitza, who had returned to the Soviet Union.[27][28] He supervised the installation of new cryogenic equipment, and supervised low temperature research. He was elected a Fellow of the Royal Society in 1936,[2][4] and in 1939 was elected the Jacksonian Professor of Natural Philosophy, effective 1 October 1939.[4]

Cockcroft and Walton were well aware of the limits of their accelerator. A much better design had been developed in the United States by

Second World War in Europe in 1939, and it too would be obsolescent when it was completed after the war.[30]

Second World War

GL Mk. III radar

At the outbreak of the Second World War, Cockcroft took up the post of Assistant Director of Scientific Research in the

atomic bomb could be technically feasible. This committee was succeeded by the MAUD Committee, of which Cockcroft was also a member, in June 1940. This committee directed the ground-breaking early research in Britain.[33]

In August 1940, Cockcroft travelled to the United States as part of the Tizard Mission. Because Britain had developed many new technologies but lacked the industrial capacity to fully exploit them, it was decided to share them with the United States, although that nation was not yet at war.[34] The information provided by the Tizard Mission contained some of the greatest scientific advances made during the war. The shared technology included radar technologies, in particular the greatly improved cavity magnetron designed by Oliphant's group at Birmingham, which the American historian James Phinney Baxter III described as "the most valuable cargo ever brought to our shores",[35] the design for the proximity fuze, details of Frank Whittle's jet engine and the Frisch–Peierls memorandum describing the feasibility of an atomic bomb. Though these may be considered the most significant, many other items were also transported, including designs for rockets, superchargers, gunsights and submarine detection devices. He returned to Britain in December 1940.[34]

Soon after his return, Cockcroft was appointed Chief Superintendent of the Air Defence Research Development Establishment (ADRDE) at

Christchurch, Hampshire.[4] His focus was on the use of radar for shooting down enemy aircraft. The GL Mk. III radar was developed as a target tracking and predicting radar, but by 1942 the SCR-584 radar developed for the same purpose in the United States became available, and Cockcroft recommended that it be acquired under Lend-Lease. On his own initiative, he acquired SCR-584 sets for testing, and trials conducted on the Isle of Sheppey in October 1943 conclusively demonstrated that SCR-584 was superior. This made Cockcroft very unpopular at the Ministry of Supply, but he had intelligence that the Germans were planning to deploy the V-1 flying bomb. On 1 January 1944, Lieutenant-General Sir Ronald Weeks sent Washington an urgent request for 134 SCR-584 sets.[36]

A proximity fuze

The

Commander of the Order of the British Empire in June 1944.[38]

In August 1943, the

Combined Policy Committee to control the Manhattan Project.[39] A final agreement was spelt out on 20 May 1944. Under it, the Americans would assist with the construction of a heavy water-moderated nuclear reactor in Canada, and would provide technical assistance with matters such as corrosion and the effects of radiation on materials. They would not provide details about plutonium chemistry or metallurgy, although irradiated uranium slugs were made available for the British to work it out for themselves.[40] A sticking point was the director of the Montreal Laboratory, Hans von Halban, who was a poor administrator, did not work well with the Canadians,[41] and was regarded as a security risk by the Americans.[42] In April 1944 a Combined Policy Committee meeting at Washington agreed that Montreal Laboratory scientists who were not British subjects would leave, and Cockcroft would become the new director of the Montreal Laboratory in May 1944.[43]

ZEEP reactor in February 1954 with NRX and NRU (under construction, in background)

On 24 August 1944, the decision was taken to build a small reactor in order to test the Montreal Laboratory's calculations relating to such matters as lattice dimensions, sheathing materials, and control rods, before proceeding with the full-scale NRX reactor. This was named ZEEP, for Zero Energy Experimental Pile.[44] Building reactors in downtown Montreal was out of the question; the Canadians selected, and Groves approved, a site at Chalk River, Ontario, on the south bank of the Ottawa River some 110 miles (180 km) north west of Ottawa.[45] The Chalk River Laboratories opened in 1944, and the Montreal Laboratory was closed in July 1946.[44] ZEEP went critical on 5 September 1945,[46] becoming the first operating nuclear reactor outside the United States.[47] The larger NRX followed on 21 July 1947.[46] With five times the neutron flux of any other reactor, it was the most powerful research reactor in the world.[48] Originally designed in July 1944 with an output of 8 MW, the power was raised to 10 MW through design changes such as replacing uranium rods clad in stainless steel and cooled by heavy water with aluminium-clad rods cooled by light water.[49]

Cockcroft was shocked when he was informed on 10 September 1945 that the British physicist Alan Nunn May, who worked at the Chalk River Laboratories, was a Soviet spy. In August 1947, Cockcroft was one of the scientists who signed a petition urging that Nunn May's ten-year prison sentence be reduced, an act he later regretted.[50]

Post war

In April 1945, Cockcroft and Oliphant scouted a site for a similar establishment in Britain, settling on

Los Alamos Laboratory became head of the Theoretical Physics; Robert Spence, Cockcroft's deputy at Montreal Laboratory, became head of Chemistry; H.W.B. Skinner, of General Physics; Otto Frisch, of Nuclear Physics; and John Dunworth, of Reactor Physics.[52] Fuchs was later arrested as a Soviet spy on 3 February 1950.[53]

The low-powered, graphite-moderated

1958 US–UK Mutual Defence Agreement.[58]

Under Cockcroft's direction, AERE took part in frontier fusion research in the post-war years, including the

Oxford University under Peter Thonemann. In 1951, Cockcroft arranged for the Oxford group to be transferred to Harwell. Cockcroft approved the construction of ZETA (Zero Energy Thermonuclear Assembly) by the Thonemann's Harwell group, and the smaller Sceptre by Allibone's AEI group. James L. Tuck's group at the Los Alamos Laboratory was also researching fusion, and Cockcroft struck an agreement with the Americans that they would release their results together, which was done in 1958. Despite Cockcroft's perennial optimism that a breakthrough was imminent, fusion power remained an elusive goal.[59]

Cockcroft's Folly

The two chimney stacks of the Windscale reactors, with the visible swellings to house Cockcroft's filters

As director of the AERE, Cockcroft famously insisted that the chimney stacks of the Windscale plutonium production reactors be fitted, at great expense, with high-performance filters. That was in response to a report that uranium oxide had been found in the vicinity of the X-10 Graphite Reactor in Oak Ridge, Tennessee. Because it was decided to fit them after the stacks had been designed, the filters became pronounced lumps at the top of the chimneys.

The reactors had been designed to remain clean and uncorroded during use, so it was thought there would be no particulate for the filters to catch. As well, the uranium oxide at Oak Ridge turned out to be from the chemical plant and not the reactor. The filters therefore became known as "Cockcroft's Folly". However, when the core of one of the two reactors ignited the Windscale fire of 1957, the filters prevented a far worse release of radioactive material. Terence Price, future scientific advisor at the Ministry of Defence in the 1960s, noted that "the word folly did not seem appropriate after the accident".[60][61]

Later life

Cockcroft receiving the Atoms for Peace Award in January 1961

On 24 January 1959, Churchill College, Cambridge, was formally recognised by the University. Two days later, the Trustees announced that Cockcroft would be its first Master. Although it would also teach the humanities and social sciences, 70 per cent of the student body would study science and technology related subjects. He nominated the first fellows, and he oversaw the initial construction. Controversy arose over the chapel. A 1961 plan to build it at the entrance to the college, as was traditional at Cambridge, led to the immediate resignation of Francis Crick, a staunch atheist, as a fellow. The first undergraduates arrived in 1961, and the college, still incomplete, was formally opened by Prince Philip, Duke of Edinburgh, on 5 June 1964.[62]

Churchill College, Cambridge, in 2005

Cockcroft was president of the

Rutherford Memorial Lecture in 1944. He was the British delegate on the Council of CERN as well as Chairman of the Nuclear Physics Sub-Committee of the Department of Scientific and Industrial Research.[4]

In addition to winning, along with Walton, the Hughes Medal and 1951 Nobel Prize in Physics, Cockcroft received numerous awards and accolades over the years. He became a

Knight Commander of the Military Order of Christ by Portugal in 1955, and the Grand Cross of the Order of Alfonso X by Spain in 1958.[4]

Cockcroft (left) at a sod turning for the Saskatchewan Accelerator Laboratory in Saskatoon, Canada in May 1962

Cockcroft died from a

Parish of the Ascension Burial Ground in Cambridge, in the same grave as his son Timothy. A memorial service was held at Westminster Abbey on 17 October 1967.[68]

Several buildings in the United Kingdom are named after him: the Cockcroft building at the

Research School of Physical Sciences and Engineering, Australian National University, the Cockcroft building, is named after him.[73]

Cockcroft's papers are held at the Churchill Archives Centre in Cambridge, and are accessible to the public. They include his lab books, correspondence, photographs (with dozens depicting the construction of Chalk River, CKFT 26/4), theses and political papers.[74]

Notes

  1. PMID 4862179
    .
  2. ^
    doi:10.1093/ref:odnb/2473. (Subscription or UK public library membership
    required.)
  3. ^ Hartcup & Allibone 1984, p. 2.
  4. ^
    S2CID 57116624
    .
  5. ^ Hartcup & Allibone 1984, pp. 4–5.
  6. ^ Hartcup & Allibone 1984, pp. 5–7.
  7. ^ Hartcup & Allibone 1984, pp. 10–15.
  8. ^ "No. 30993". The London Gazette (Supplement). 5 November 1918. p. 13089.
  9. ^ Hartcup & Allibone 1984, pp. 15–19.
  10. ^ Hartcup & Allibone 1984, pp. 20–25.
  11. ^ Hartcup & Allibone 1984, p. 34.
  12. ^ Cockcroft, John Douglas. "On phenomena occurring in the condensation of molecular streams on surfaces". University of Cambridge. Retrieved 4 September 2016.
  13. ISSN 1364-5021
    .
  14. ^ Hartcup & Allibone 1984, p. 33.
  15. ^ Hartcup & Allibone 1984, pp. 37–42.
  16. S2CID 120684789
    .
  17. ^ Hartcup & Allibone 1984, p. 43.
  18. ^ a b Hartcup & Allibone 1984, pp. 50–53.
  19. ^ "Award winners : Hughes Medal". Royal Society. Retrieved 4 September 2016.
  20. ^ "The Nobel Prize in Physics 1951". Nobel Foundation. Retrieved 4 September 2016.
  21. ISSN 1364-5021
    .
  22. ISSN 1364-5021
    .
  23. ISSN 1364-5021
    .
  24. ISSN 1364-5021
    .
  25. ISSN 1364-5021
    .
  26. ISSN 1364-5021
    .
  27. ^ "University of Cambridge". University of Cambridge Digital Library. Retrieved 12 October 2022.
  28. ^ "The Nobel Prize". nobelprize.org. Retrieved 12 October 2022.
  29. ^ Hartcup & Allibone 1984, pp. 368–371.
  30. ^ Clarke, Dr N. M. "The Nuffield Cyclotron at Birmingham". University of Birmingham. Archived from the original on 8 April 2014. Retrieved 2 May 2013.
  31. ^ Hartcup & Allibone 1984, pp. 89–90.
  32. ^ Hartcup & Allibone 1984, p. 94.
  33. ^ Hartcup & Allibone 1984, pp. 120–124.
  34. ^ a b Hartcup & Allibone 1984, pp. 96–103.
  35. ^ "Radar". Newsweek. 12 January 1997. Retrieved 4 September 2016.
  36. ^ a b Hartcup & Allibone 1984, pp. 108–111.
  37. ^ Hartcup & Allibone 1984, p. 96.
  38. ^ "No. 36544". The London Gazette (Supplement). 2 June 1944. p. 2586.
  39. ^ Hewlett & Anderson 1962, pp. 277–280.
  40. ^ Hewlett & Anderson 1962, pp. 281–284.
  41. ^ Avery 1998, pp. 184–185.
  42. ^ Gowing 1964, pp. 206–207, 209–214.
  43. ^ Goldschmidt, Bertrand. "How it All Began in Canada – The Role of the French Scientists". Canadian Nuclear Society. Retrieved 6 May 2016.
  44. ^
    Laurence, George C. "Early Years of Nuclear Energy Research in Canada"
    (PDF). Retrieved 19 May 2016.
  45. ^ Jones 1985, pp. 246–247.
  46. ^ a b Close 2015, pp. 102–104.
  47. ^ Manhattan District 1947, p. 9.23.
  48. Università di Pisa
    . Retrieved 15 April 2016.
  49. ^ Manhattan District 1947, pp. 9.9–9.10.
  50. ^ Hartcup & Allibone 1984, pp. 133–134.
  51. ^ Hartcup & Allibone 1984, pp. 136–137.
  52. ^ Hartcup & Allibone 1984, pp. 139–146.
  53. ^ Hartcup & Allibone 1984, p. 158.
  54. ^ Hartcup & Allibone 1984, pp. 146–147.
  55. ^ Gowing & Arnold 1974a, pp. 379–382.
  56. ^ Gowing & Arnold 1974, pp. 105–108.
  57. ^ Hartcup & Allibone 1984, pp. 222–223.
  58. JSTOR 2611300
    .
  59. ^ Hartcup & Allibone 1984, pp. 201–204.
  60. ^ Leatherdale, Duncan (14 November 2014). "Windscale Piles: Cockcroft's Follies avoided nuclear disaster". BBC. Retrieved 3 September 2016.
  61. ^ Hartcup & Allibone 1984, p. 211.
  62. ^ Hartcup & Allibone 1984, pp. 250–258.
  63. ^ "No. 38161". The London Gazette (Supplement). 30 December 1947. p. 2.
  64. ^ Hartcup & Allibone 1984, p. 193.
  65. ^ "No. 39863". The London Gazette (Supplement). 26 May 1953. p. 2943.
  66. ^ "No. 40960". The London Gazette (Supplement). 28 December 1956. p. 4.
  67. ^ "No. 39462". The London Gazette. 8 February 1952. p. 789.
  68. ^ Hartcup & Allibone 1984, p. 284.
  69. ^ "Cockcroft Building". University of Cambridge. Retrieved 5 September 2016.
  70. ^ "Cockcroft Institute". Cockcroft Institute. Retrieved 5 September 2016.
  71. ^ "Presentation Notes: Cockcroft Building, University of Brighton". University of Brighton. Retrieved 5 September 2016.
  72. ^ "New £3m Megalab unveiled". University of Salford. Retrieved 5 September 2016.
  73. ^ "Cockcroft Building". Archived from the original on 15 September 2016. Retrieved 5 September 2016.
  74. ^ "The Papers of Sir John Cockcroft". Churchill Archives Centre, ArchiveSearch. Retrieved 30 September 2021.

References

Further reading

External links

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Academic offices
Preceded by Jacksonian Professor of Natural Philosophy
1939–1946 		Succeeded by
New institution Master of Churchill College, Cambridge
1959–1967 		Succeeded by
Preceded by Chancellor of the Australian National University
1961–1965 		Succeeded by
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