Intensity Variation of Vertical Cosmic-Ray Air Showers

A new experimental approach has been studied for measuring the sidereal time variation of the high-energy cosmic radiation. The apparatus consists of an "air-shower telescope" using only six small counter tubes and an "extensive" tray of GM tubes. The apparatus is sensitive to vertical showers and discriminates against showers with (projected) zenith angle greater than 10^∘{}; this directional efficiency is calculated to be about 90% and has been verified experimentally. In subsidiary experiments, the apparatus has been used to measure the zenith angle dependence of air showers. We can therefore set up an arrangement of counters to detect only vertical showers of high energy. Preliminary results show a counting rate of 1 per 3 hours per recording station for vertical extensive air showers of energy {≥}10¹⁵ ev. The barometric coefficient has been determined as (9±{}4)% per cm Hg; however, no statistically significant time variation has as yet been detected. The recording rate can be increased and better statistics obtained by increasing the number of recording setups.