27 May 1897|
|Died||18 September 1967
|Institutions||Atomic Energy Research Establishment|
|Alma mater||Victoria University of Manchester
Manchester College of Technology
St. John's College, Cambridge
|Academic advisors||Ernest Rutherford|
|Notable students||Ishfaq Ahmad|
|Known for||Splitting the atom|
|Notable awards||Nobel Prize in Physics (1951)|
Sir John Douglas Cockcroft OM KCB CBE FRS (27 May 1897 – 18 September 1967) was a British physicist. He shared the Nobel Prize in Physics for splitting the atomic nucleus with Ernest Walton, and was instrumental in the development of nuclear power. He was the first Master of Churchill College and is buried at the Parish of the Ascension Burial Ground in Cambridge, together with his wife Elizabeth and son John, known as Timothy, who had died at the age of two in 1929.
Early years 
Cockcroft was born in Todmorden, England, the eldest son of a mill owner. He was educated at Todmorden Secondary School (1909–1914) (where his physics teacher, Luke Sutcliffe, would later tutor another future Nobel Prize-winner, Geoffrey Wilkinson) and studied mathematics at the Victoria University of Manchester (1914–1915). He was a signaller in the Royal Artillery from 1915 to 1918. After the war ended, he studied electrotechnical engineering at Manchester College of Technology from 1919 until 1920. Cockcroft received a mathematics degree from St. John's College, Cambridge in 1924 and began research work under Ernest Rutherford. In 1929 he was elected a Fellow of St. John's College.
Nuclear research 
In 1928, he began to work on the acceleration of protons with Ernest Walton. In 1932, they bombarded lithium with high energy neutrons, electrons and protons and succeeded in transmuting it into helium and other chemical elements. This was one of the earliest experiments to change the atomic nucleus of one element to a different nucleus by artificial means. This feat was popularly – if somewhat inaccurately – known as splitting the atom.
At the outbreak of the Second World War, he took up the post of Assistant Director of Scientific Research in the Ministry of Supply, working on radar. In 1944, he took charge of the Canadian Atomic Energy project and became Director of the Montreal Laboratory and Chalk River Laboratories, replacing Hans von Halban, who was considered a security risk. In 1946, he returned to Britain to set up the Atomic Energy Research Establishment (AERE) at Harwell, charged with developing Britain's atomic power programme. He became the first director of AERE. Even when leaving the post, he continued to be involved with Harwell. He was made a Commander of the Order of the British Empire in 1944, knighted in 1948, and created Knight Commander of the Order of the Bath in 1953.
As director of the AERE, he famously insisted that the coolant discharge chimney stacks of the Windscale plutonium production reactors be fitted, at great expense, with high performance filters. Since this was decided after the stacks had been designed, they produced iconic lumps in the shape of the structures. The reactors were designed to remain clean and uncorroded during use, thus it was not considered that there would be any particulate present for the filters to catch. These filters were therefore known as "Cockcroft's Folly" until the core of one of the two reactors caught fire in 1957, and the filters prevented the disaster from becoming a catastrophe.
In post-war years, AERE under his direction took part in frontier fusion research, including the ZETA program.
Personal life 
Cockcroft married Eunice Elizabeth Crabtree (born 26 October 1898, died 4 October 1989) in 1925 and had six children: John Haslam, known as Timothy, born 29th January 1927, died 11 October 1929; Joan Dorothea, known as Thea, born 5th October 1932; Jocelyn, born 1st September 1934; Elisabeth Fielden, born 23rd February 1936; Catherine Helena, born 17th October 1939; and Christopher Hugh John, born 14th January 1942. He died at Churchill College, Cambridge, 18 September 1967; he is buried at the Parish of the Ascension Burial Ground in Cambridge, in the same grave as his wife and son John, known as Timothy.  John R. Cockcroft is his great nephew, notable in the field of cardiology and arterial stiffness.
In 1951, Cockcroft, along with Walton, was awarded the Nobel Prize in Physics for his work in the use of accelerated particles to study the atomic nucleus. In 1959, he became the first Master of Churchill College, Cambridge. He was president of the Institute of Physics, the Physics Society, and the British Association for the Advancement of Science. Cockcroft served as chancellor of the Australian National University from 1961 to 1965. He received the American Atoms for Peace Award in 1961. He delivered the Rutherford Memorial Lecture in 1944.
Today, five buildings in the United Kingdom are named after him: the Cockcroft building at the New Museums Site of the University of Cambridge, comprising a lecture theatre and several hardware laboratories; the Cockcroft Institute at Daresbury Laboratory in Cheshire; the Cockroft Hall lecture theatre at the Harwell Science and Innovation Centre; the Cockcroft building of the University of Brighton; and the Cockcroft building of the University of Salford. The oldest building at the Research School of Physical Sciences and Engineering, Australian National University, the Cockcroft building, is named after him.
In the 1950s, the AERE commissioned a number of homes to be built in the nearby town of Didcot for the many Harwell workers who lived there. The "focal" road of this development in the south of the town (the one with the shops, school and public house) is named Cockcroft Road.
- Allibone, T. E. (1967). "Sir John Cockcroft, O.M., F.R.S". British Journal of Radiology 40 (479): 872–873. doi:10.1259/0007-1285-40-479-872. PMID 4862179.
- Oliphant, M. L. E.; Penney, L. (1968). "John Douglas Cockcroft. 1897-1967". Biographical Memoirs of Fellows of the Royal Society 14: 139. doi:10.1098/rsbm.1968.0007.
- A Guide to Churchill College, Cambridge: text by Dr. Mark Goldie, pages 62 and 63 (2009)
Further reading 
- Cathcart, Brian, The Fly in the Cathedral, Penguin, 2005. ISBN 0-14-027906-7
- The Papers of Sir John Cockcroft are held at the Churchill Archives Centre in Cambridge, and are accessible to the public. They include Cockcroft's lab books, correspondence, photographs (with dozens depicting the construction of Chalk River, CKFT 26/4), theses and political papers.
- John Cockcroft at Find a Grave
- Biography from Churchill Archives Centre
- Biography from the Nobel Museum
- Another Nobel biography
- Speech to the Empire Club of Canada
- Annotated bibliography for John Cockcroft from the Alsos Digital Library for Nuclear Issues
- Archival material relating to John Cockcroft listed at the UK National Archives
None: new position
Churchill College, Cambridge