Magnetic Cloud-Chamber Analysis of Cosmic Rays at 3.4 Kilometers

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Abstract
About 18,000 magnetic cloud-chamber photographs (magnetic field of 8000 Gauss) have been taken at an altitude of 3.4 kilometers at Climax, Colorado. These were counter-controlled with single counters above and below the chamber forming a twofold telescope. The photographs were taken under three conditions: with no absorber over the chamber, and with 5 and 20 cm of lead above the chamber. The momenta of singly occurring particles have been measured and plotted to give momentum distributions. With sufficient absorber over the chamber, selection of exposures showing a single track has the effect of eliminating electrons. The momentum spectrum of the residual particles (mesons and some protons) shows a distribution closely similar to that found for mesons at sea level. Contrary to previously published reports, no appreciable increase in the relative number of low energy mesons is found. Particles selected in this way show a positive to negative ratio of 1.5±0.05 as compared to reported values of about 1.3 at sea level. This confirms previous reports of an increase in this ratio with altitude. However, it is shown that the increase in positive excess is due in part to a greater number of protons at higher altitudes, and it is suggested that the entire increase may be thus accounted for, the positive excess of mesons remaining constant with altitude. Some estimate has been made of the abundance of protons at 3.4 kilometers.

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