Cecil Powell
1903–1969, Tonbridge, Kent, England, near Milan, Italy
English physicist who developed the nuclear photographic-emulsion technique and used it to discover the pion; he received the 1950 Nobel Prize in Physics.
Cecil Frank Powell was born in Tonbridge, Kent, studied at Sidney Sussex College, Cambridge, and researched with Rutherford and Wilson at the Cavendish. In 1928 he moved to the University of Bristol, where he spent his whole career, becoming professor of physics in 1948.
At Bristol he shifted from ionization detectors to special photographic plates recording particle tracks, building an international school of scanners who read emulsions exposed at high altitude. His group discovered the pion in 1947 — the particle Yukawa had predicted — and he led the European emulsion collaborations that anticipated the spirit of CERN.
Nobel-winning work
Powell developed the photographic method of studying nuclear processes: special emulsions rich in silver bromide — developed with Ilford — recorded the track of each charged particle, yielding measurable energies and masses. He exposed the plates at high altitude on the Pic du Midi and in the Andes to capture cosmic rays.
In 1947, his Bristol group — including César Lattes, Giuseppe Occhialini, and Hugh Muirhead — found in the emulsions tracks of a particle some 300 times the electron's mass decaying into a muon: the π-meson (pion), the carrier of the nuclear force Yukawa had predicted in 1935. Powell received the 1950 Nobel Prize in Physics 'for his development of the photographic method of studying nuclear processes and his discoveries regarding mesons made with this method'.
Workplaces: University of Bristol
United Kingdom