Pavel Alekseevich Cherenkov

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Pavel Alekseevich Cherenkov

The principal contribution of the Russian physicist Pavel Alekseevich Cherenkov (1904-1990) was the explanation of a certain pale bluish radiation as a consequence of high-speed electrons passing through refractive mediums.

More is known about the Cherenkov effect than about Pavel Cherenkov himself. He was born on July 28, 1904, into a poor peasant family living in the village of Novaya Chigla, Voronezh Province. At the age of 20 he entered the State University of Voronezh, graduating 4 years later. In 1930 he was accepted as a postgraduate student at the P. N. Lebedev Institute of Physics of the Soviet Academy of Sciences. Cherenkov earned his doctorate in 1940.

As early as 1910, Marie Curie had noticed that radium salts dissolved in distilled water produced a bluish glow, but she did not pursue this observation further. During the late 1920s a French scientist, L. I. Mallet, examined the spectrum of the bluish-white radiation and discovered it was continuous instead of lines or bands usually associated with fluorescence; he failed to uncover the origin of the glow. Between 1934 and 1938 Cherenkov conducted a series of intensive investigations of the fluorescence of water bombarded by gamma rays. Before each experiment he would sit for 60 to 90 minutes in total darkness in order to increase his visual sensitivity to the feeble glow. He decided in 1934 that the bluish radiation was not a fluorescent phenomenon.

Sergei Vavilov's 1934 paper, which appeared at the same time as the Cherenkov study, suggested that the gamma-ray-induced glow was due to the slowing down of the electrons in the water (an example of the bremsstrahlung process). Vavilov then helped design a number of experiments for Cherenkov to carry out in the hope of determining the source of the luminescence. Under Vavilov's guidance Cherenkov arrived at the conclusion that the radiation was the result of light emitted by electrons liberated by the gamma rays as the electrons moved in a refractive medium at a speed faster than the propagation of light itself in that medium; the light was emitted not in random fashion but at a specific angle to the direction of the moving electron. The shock waves produced by bullets, missiles, or jet planes moving faster than the speed of sound are an acoustical analogy of the Cherenkov radiation.

The theory and the effect have been extended, refined, and modified; it has found increasing application in the physics of cosmic rays and high-energy particles. By employing photomultipliers, the Cherenkov effect has been successfully used in detectors for obtaining vital data on high-speed particles; a Cherenkov detector orbited the earth in Sputnik III. Cherenkov and Vavilov, together with Igor Evgenievich Tamm and Ilya Mikhailovich Frank, received the Stalin Prize in 1946 for their explanation, theory, and practical application of the Cherenkov radiation. In the former Soviet Union the "blue glow" is often referred to as the Vavilov-Cherenkov effect; Vavilov is usually given greater credit for its development than Cherenkov. In 1958 Cherenkov, Frank, and Tamm shared the Nobel Prize in physics. In 1964 Cherenkov was elected a corresponding member of the Soviet Academy of Sciences. He continued working in high energy physics and established a fine reputation for the training of research physicists. Cherenkov died in 1990.

Further Reading

Only brief and scattered accounts of Cherenkov exist. There is a biographical chapter on him in Nobel Foundation, Nobel Lectures: Physics, vol. 3 (1964). The most comprehensive work in English on the Cherenkov effect is J. V. Jelley, Cherenkov Radiation and Its Applications (1958). The Cherenkov radiation is discussed in J. G. Linhart, Plasma Physics (1960; 2d ed. 1961), and the Cherenkov detectors are presented in David M. Ritson, ed., Techniques of High Energy Physics (1961). □