Cecil Frank Powell (5 December 1903 – 9 August 1969) was an Englishnuclear physicist who received theNobel Prize in Physics in 1950 for heading the team that developed the photographic method of studying nuclear processes and for the resulting discovery of thepion (pi-meson), asubatomic particle.[3]
Powell was born inTonbridge, Kent,England, the son Frank and Elizabeth Caroline (née Bisacre) Powell.[1] His father was agunsmith. He was educated at a local primary school before gaining ascholarship to theJudd School, Tonbridge.[4] Following this he attendedSidney Sussex College, Cambridge, graduating in 1925 in natural sciences.[4] After completing his bachelor's degree he worked at theCavendish Laboratory, Cambridge, underC.T.R. Wilson andLord Rutherford, conducting research into condensation phenomena, and gaining his PhD in physics in 1929.[5]
In 1932 Powell married Isobel Artner (1907–1995), and the couple had two daughters, Jane and Annie.[4][6]
In 1928 he took up a post as research assistant toArthur Mannering Tyndall in the H.H. Wills Physical Laboratory at theUniversity of Bristol, later being appointed lecturer, and in 1948 appointed Melville Wills Professor of Physics.[7] In 1936 he took part in aRoyal Society expedition toMontserrat in theWest Indies as part of a study of a damaging earthquake swarm.[8] He appears on a stamp issued inGrenada.[9]
During his time at Bristol University, Powell applied himself to the development of techniques for measuring the mobility of positive ions, to establishing the nature of the ions in common gases, and to the construction and use of aCockcroft generator to study the scattering ofatomic nuclei.[4] He also began to develop methods employing specialisedphotographic emulsions to facilitate the recording of the tracks of elementary particles, and in 1938 began applying this technique to the study of cosmic radiation,[4] exposing photographic plates at high-altitude, at the tops of mountains and using specially designed balloons,[10] collaborating in the study withGiuseppe "Beppo" Occhialini,Hugh Muirhead and young Brazilian physicistCésar Lattes. This work led in 1947 to the discovery of thepion (pi-meson),[11] which proved to be the hypothetical particle proposed in 1935 byHideki Yukawa in his theory of nuclear physics.[12]
In 1949 Powell was elected a Fellow of the Royal Society[1][13] and received the society'sHughes Medal the same year.[4] In 1950 he was awarded theNobel Prize for Physics "for his development of the photographic method of studying nuclear processes and his discoveries regarding mesons made with this method".César Lattes was working with him at the time of the discovery and had improved the sensitivity of the photographic emulsion.César Lattes was the first to write an article describing the discovery that would lead to the Nobel Prize.[14] Debendra Mohan Bose (nephew ofJagadish Chandra Bose) and Chowdhuri published three consecutive papers inNature, but could not continue further investigation on account of "non-availability of more sensitive emulsion plates during the war years. Seven years after this discovery of mesons by DM Bose and Bibha Chowdhuri, C.F. Powell made the same discovery of pions and muons and further decay of muons to electrons… using the same technique". He acknowledged in his book, "In 1941, Bose and Chaudhuri (sic) had pointed it out that it is possible, in principle, to distinguish between the tracks of protons and mesons in an emulsion… They concluded that many of the charged particles arrested in their plates were lighter than protons, their mean mass being … the physical basis of their method was correct and their work represents the first approach to the scattering method of determining momenta of charged particles by observation of their tracks in emulsion". In fact, the measured mass of the particle by Bose and Chowdhuri was very close to the accepted value measured by Powell who used improved "full-tone" plates.[15] From 1952 Powell was appointed director of several expeditions to Sardinia and the Po Valley, Italy, utilizing high-altitude balloon flights.[4]
In 1955, Powell, also a member of the World Federation of Scientific Workers,[16] added his signature to theRussell-Einstein Manifesto put forward by Bertrand Russell, Albert Einstein and scientistJoseph Rotblat, and was involved in preparations for the firstPugwash Conference on Science and World Affairs.[16] As Rotblat put it, "Cecil Powell has been the backbone of the Pugwash Movement. He gave it coherence, endurance and vitality." Powell chaired the meetings of the Pugwash Continuing Committee, often standing in for Bertrand Russell, and attended meetings until 1968.[17]
In 1961 Powell received theRoyal Medal, and served on the Scientific Policy Committee of the European Organization for Nuclear Research (CERN) that year,[4] and in 1967 he was awarded theLomonosov Gold Medal by the Academy of Sciences of the USSR (now Russian Academy of Sciences) "for outstanding achievements in the physics of elementary particles".[18]
Memorial bench dedicated to Powell outside the Capanna Vittoria restaurant, on the Alpe Giumello, inCasargo,Italy.
Powell died while on holiday with his wife in theValsassina region of Italy, lodging in a house in Sanico, in theProvince of Lecco.[22] On 9 August 1969, near the end of a walk in the foothills of theAlps, he suffered aheart attack.[22][23] Giuseppe Occhialini had a wooden bench built with Powell's name carved into a commemorative plaque, and then transported it toPremana, a village in the mountains aboveLake Como.[23] It was installed on the path where he died, outside the Rifugio Capanna Vittoria (now the Capanna Vittoria restaurant), on the Alpe Giumello, inCasargo.[22] Occhialini's reason was, "...if that bench had already been there, Powell would probably have stopped to rest there".[23]
In October 2011 a replacementcommemorative plaque was installed in Downside Road, Bristol.[6]
In 2013, theInternational Inner Wheel Club ofLecco, inLombardy, Northern Italy, erected a sign in memory of Powell, close to where he died, at the Capanna Vittoria restaurant, on the Alpe Giumello, in Casargo.[22]
^"Cecil Powell".Goethe-Universität Frankfurt. Johann Wolfgang Goethe-Universität Frankfurt am Main. Archived fromthe original on 27 March 2009. Retrieved14 September 2009.
^"Powell, Cecil".Encyclopædia Britannica. London: Encyclopædia Britannica Limited. 1962.
