Cascade Showers and Nuclear Disintegrations at 10,000 Feet

Abstract

A large cloud chamber containing eight lead plates was operated without counter control at 10,000 feet. In 8500 photographs, 1090 cascade showers and 58 nuclear disintegrations were observed. The differential energy spectrum for the shower-producing rays, which was obtained from the relative frequency of occurrence for showers of a given size, is proportional to $E^{-1.7\mathrm{}}$ for $E=2\mathrm{}\times {10}^8$ ev and to $E^{-3.0\mathrm{}}$ for $E={10}^9$ ev. The shower-producing rays with $E>\mathrm{}2\mathrm{}\times {10}^8$ ev constituted 6.5 percent of the radiation observed in the cloud chamber; one-third of the shower-producing rays were photons. Approximately one-third of the observed nuclear disintegrations contained particles that penetrated at least 0.7 cm of lead and four contained particles that penetrated at least 2.8 cm of lead. Most of the disintegration particles were protons or mesotrons. The initiating particles were neutrons and protons, with the former predominant for the lower energy disintegrations. There appears to be no sharp line of distinction between low energy and high energy disintegrations. No correlation was observed between the disintegrations and the cascade showers.