PHYLLIS FREEER, E. J. LOFGREN, E. P. NEY, AND F. OPPENHEIMER University of Minnesota, Minneapolis, Minnesota AND H. L. BRADT AND B. PETERS University of Rochester, Rochester, New York (Received June 8, 1948) RECENT high altitude flights in free balloons have given evidence for the existence of nuclei of atomic number up to about 40 and kinetic energies of about 2 Bev per nucleon as a component of cosmic radiation above 90,000 feet. Tracks of such particles were observed both in a cloud chamber and in Ilford nuclear emulsions. The cloud chamber and associated equipment was enclosed in a sphere of aluminum 30 inches in diameter and 0.040-inch thick, which was kept at atmospheric pressure and within a temperature range between 58 and 98 degrees F throughout the flight. The balloon reached an altitude of 94,000 feet (14 g/cm2 below the top of the atmosphere), spent three hours above 90,000 feet, and four hours above 65,000 feet. Stacks of photographic plates in groups of twelve were placed above and below the chamber, the emulsion lying in the vertical plane. Tracks which entered the photographic plates below the chamber within 300 from the vertical had to pass through all
Physical Review – American Physical Society (APS)
Published: Jul 15, 1948
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