C. F. Powell

Cecil Frank Powell (5 December 1903 – 9 August 1969) was a British experimental physicist who received the Nobel Prize in Physics in 1950 for heading the team that developed the photographic method of studying nuclear processes, and for the resulting discovery of the pion (pi-meson).<ref name="physicstodayobit">Template:Cite journal</ref>

Education

Cecil Frank Powell was born on 5 December 1903 in Tonbridge, England, the son of Frank Powell, a gunsmith, and Elizabeth Caroline Bisacre.<ref name="frs" />

Powell was educated at a local primary school before gaining a scholarship to The Judd School in Tonbridge.<ref name=NobelBiog>Template:Cite book</ref> He then entered Sidney Sussex College, Cambridge, graduating in 1925 with First Class Honours in the Natural Science Tripos.<ref name=NobelBiog/> After completing his bachelor's degree, he worked under Ernest Rutherford and C. T. R. Wilson in the Cavendish Laboratory, conducting research on condensation phenomena. He received his Ph.D. in Physics in 1927.<ref>Cambridge University Library</ref>

In 1932, Powell married Isobel Artner (1907–1995). They had two daughters, Jane and Annie.<ref name=NobelBiog/><ref name="CHIS" />

Career and research

In 1927, Powell became a research assistant to Arthur Mannering Tyndall in the H. H. Wills Physical Laboratory at the University of Bristol, later being appointed lecturer, and in 1948 appointed Melville Wills Professor of Physics.<ref>Template:Cite web</ref> In 1936, he took part in a Royal Society expedition to Montserrat in the West Indies as part of a study of a damaging earthquake swarm.<ref>Template:Cite journal</ref> He appears on a stamp issued in Grenada.<ref>Template:Cite web</ref>

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 a Cockcroft–Walton generator to study the scattering of atomic nuclei.<ref name=NobelBiog/> He also began to develop methods employing specialised photographic emulsions to facilitate the recording of the tracks of elementary particles, and in 1938 began applying this technique to the study of cosmic radiation,<ref name=NobelBiog/> exposing photographic plates at high-altitude, at the tops of mountains and using specially designed balloons,<ref>Template:Cite encyclopedia</ref> collaborating in the study with Giuseppe Occhialini, Hugh Muirhead, and César Lattes. This work led in 1947 to the discovery of the pion (pi-meson),<ref>Template:Cite web</ref> which proved to be the hypothetical particle proposed in 1935 by Hideki Yukawa in his theory of nuclear physics.<ref>Template:Cite journal</ref>

In 1949, Powell was elected a Fellow of the Royal Society<ref name="frs"/><ref>Template:Cite web</ref> and received the society's Hughes Medal.<ref name=NobelBiog/> In 1950, he was awarded the Nobel Prize in Physics "for his development of the photographic method of studying nuclear processes and his discoveries regarding mesons made with this method". Lattes was working with him at the time of the discovery and had improved the sensitivity of the photographic emulsion. Lattes was the first to write an article describing the discovery that would lead to the Nobel Prize.<ref>Template:Cite web</ref> Debendra Mohan Bose and Bibha Chowdhuri published three consecutive papers in Nature, 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 Bose and Chowdhuri, 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.<ref>Template:Cite web</ref> From 1952, Powell was appointed director of several expeditions to Sardinia and the Po Valley, Italy, utilizing high-altitude balloon flights.<ref name=NobelBiog/>

In 1955, Powell, also a member of the World Federation of Scientific Workers,<ref name=Pugwash1>Template:Cite web</ref> added his signature to the Russell–Einstein Manifesto put forward by Bertrand Russell, Albert Einstein, and Joseph Rotblat, and was involved in preparations for the first Pugwash Conference on Science and World Affairs.<ref name=Pugwash1/> 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.<ref>Template:Cite web</ref>

In 1961, Powell received the Royal Medal and served on the Scientific Policy Committee of the European Organization for Nuclear Research (CERN).<ref name=NobelBiog/> In 1967, he was awarded the Lomonosov Gold Medal by the Academy of Sciences of the USSR (now Russian Academy of Sciences) "for outstanding achievements in the physics of elementary particles".<ref>Template:Cite web</ref>

Global policy

He was one of the signatories of the agreement to convene a convention for drafting a world constitution.<ref>Template:Cite web</ref><ref>Template:Cite web</ref> As a result, for the first time in human history, a World Constituent Assembly convened to draft and adopt the Constitution for the Federation of Earth.<ref>Template:Cite web</ref>

Death

Memorial bench dedicated to Powell outside the Capanna Vittoria restaurant, on the Alpe Giumello, in Casargo, Italy.

Powell died while on holiday with his wife in the Valsassina region of Italy, lodging in a house in Sanico, in the Province of Lecco.<ref name="Valsassina News 26 May 2013">Template:Cite web</ref> On 9 August 1969, near the end of a walk in the foothills of the Alps, he suffered a heart attack.<ref name="Valsassina News 26 May 2013" /><ref name="Vegni 2006">Template:Cite book</ref> Giuseppe Occhialini had a wooden bench built with Powell's name carved into a commemorative plaque, and then transported it to Premana, a village in the mountains above Lake Como.<ref name="Vegni 2006" /> It was installed on the path where he died, outside the Rifugio Capanna Vittoria (now the Capanna Vittoria restaurant), on the Alpe Giumello, in Casargo.<ref name="Valsassina News 26 May 2013" /> Occhialini's reason was, "...if that bench had already been there, Powell would probably have stopped to rest there".<ref name="Vegni 2006" />

Legacy

• The Cecil F. Powell Memorial Medal was named in his honour by the European Physical Society.
• In October 2011 a replacement commemorative plaque was installed in Downside Road, Bristol.<ref name="CHIS">Template:Cite web</ref>
• In 2013, the International Inner Wheel Club of Lecco, in Lombardy, 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.<ref name="Valsassina News 26 May 2013" />

See also

• Marietta Blau

External links

• Template:Commons category inline
• Template:Nobelprize including the Nobel Lecture, 11 December 1950 The Cosmic Radiation
• Portrait photograph of Powell at the American Institute of Physics