Cosmic-ray work with emulsions in the 1940s and 1950s

摘要

The use of photographic plates to record ionizing radiations dates back to Henri Becquerel, who in 1896 discovered radioactivity from the blackening of plates by uranium salts.~1 In 1910-11, M. Kinoshita showed that it was possible to record individual tracks due to a particles at both verticle and tangential angles to the emulsion plane.~2 During the 1920s and 1930s, experiments by M. Blau and H. Wambacher in Germany, G. Zhdanov in the USSR, H. J. Taylor in England, and R. Wilkins and H. Rumbaugh and A. Locher in the United States recorded particles both from cosmic rays and from accelerators, on occasion achieving sensitivity to protons by use of organic sensitizing dyes (e.g., pinakryptol yellow).~(3-7) The general nonreproducibility of the results, however, placed the technique under something of a cloud. Indeed, in 1935, Taylor, at Cambridge, using Ilford R1 and R2 emulsions, concluded that it was "impossible to deduce with any accuracy the energy of individual particles from range in emulsion." Similar remarks were voiced by M. Stanley Livingston and Hans Bethe in 1937.~8