The Structure of Cosmic-Ray Air Showers

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Abstract
Bursts of ionization occurring in each of two thin-walled unshielded ionization chambers were measured at Chicago (elevation 190 meters), with the same apparatus used at Echo Lake (elevation 3100 meters). A comparison of the size-frequency distribution curve for bursts occurring in a single chamber at Chicago with the corresponding curve observed at Echo Lake shows that the altitude dependence for bursts containing more than 50 particles is similar to the altitude dependence of large air showers measured with Geiger-Müller counters. In contrast to this, the altitude dependence for the largest bursts is much greater. The ratio of the coincident burst rate to the single chamber burst rate is as low at Chicago as at Echo Lake. If one assumes the validity of the cascade theory of showers and of the theory of multiple scattering of electrons in air, one must conclude from these data that showers exhibiting these narrow regions of high particle density cannot originate close to the top of the atmosphere. The data presented in this paper, together with the data of Lapp and of Carmichael, show that the slope of the size-frequency distribution curve for bursts in a single chamber is dependent upon the chamber wall.