British physicist, who was awarded the 1951 Nobel Prize for Physics for his discovery in 1947 of the pi-meson (pion).
The son of a gunsmith, Powell was educated at Cambridge University where he gained his PhD in 1927. In the same year he joined the physics department of Bristol University and spent the rest of his career there, becoming Wills Professor of Physics in 1948 and director of the Wills Physics Laboratory in 1964.
In the 1930s Powell began his study of the tracks of nuclear particles on photographic plates. The standard instrument of his day, Wilson's cloud chamber, was unwieldy and limited in its use. Powell therefore developed photographic emulsions some hundred times thicker than those normally used and eventually used them to study cosmic rays by sending them up in balloons to heights of 30 000 metres. The lengthy analysis of these plates was rewarded in 1947 by Powell's discovery of the tracks of the pi-meson, predicted by H. Yukawa in 1935. Powell also, in collaboration with Giuseppe Occhialini, published one of the earliest textbooks on these new methods, Nuclear Physics in Photography (1947). Powell was also involved in setting up CERN in 1953 and was present at the Pugwash meeting in Nova Scotia in 1957 that initiated the Pugwash movement, enabling scientists to influence world affairs.
Subjects: Contemporary History (Post 1945) — Science and Mathematics.