Cecil Frank Powell (1903-1969), British nuclear physicist and Nobel Prize winner. A leading proponent of international scientific cooperation, Powell developed photographic methods that greatly enhanced the study of nuclear processes. He won the 1950 Nobel Prize in physics for his photographic methods and for discovering pi-mesons, or pions, a type of cosmic ray (cosmic rays are fast-moving subatomic particles that enter the earth's atmosphere from outer space).

Born in Tonbridge, Kent, England, Powell graduated from Sidney Sussex College of the University of Cambridge in 1925 with a B.S. degree in natural science, and earned his Ph.D. degree in physics in 1927 at the Cavendish Laboratory at Cambridge. In 1928 Powell became research assistant at the University of Bristol, and served as a professor of physics there from 1948 to 1963. In 1963 he was appointed vice chancellor of the University of Bristol, as well as director of the university's H. H. Wills Physics Laboratory, a post from which he retired only months before his death.

Powell became interested in subatomic-particle-detection devices when he studied at the Cavendish Laboratory under Scottish physicist Charles Thomson Rees Wilson, the Nobel Prize-winning inventor of the cloud chamber (a device that tracks ionized particles by producing a trail of water droplets from air saturated with water, and the tool used at the time for detecting subatomic particles). The drawback of the cloud chamber is that it requires a resting period—a luxury seldom afforded a scientist attempting to record the fast-moving tracks of electrically charged particles—each time it is used. As an alternative, Powell began experimenting with photographic emulsions that could be used continuously, but found that none of those available were of adequate quality to record evidence of the particles. He finally persuaded a photographic film company to create a new emulsion that would work. To obtain data on cosmic rays, Powell sent the new emulsion aloft in hydrogen balloons to high altitudes to capture traces of the rays, a project that eventually evolved into a collaborative effort among scientists and nonscientists throughout Europe. These expeditions resulted in Powell's discovery of a new particle, the pi-meson, or pion, which proved to be a cohesive force within the atomic nucleus. These accomplishments earned him the Nobel Prize and marked the beginning of elementary-particle physics.

Increasingly concerned about social problems attached to scientific and technological advances, Powell served from 1961 to 1963 as the chairperson of the Scientific Policy Committee of the European Organization for Nuclear Research (CERN). He was also the founder of the Pugwash Conferences for Science and World Affairs.