Intensity of the cosmic radiation at great depths underground

Abstract

The cosmic ray intensity was measured in a mine using a combined scintillation counter and Geiger counter telescope. It was shown that this apparatus could discriminate effectively against local γ-radiation. The intensities at 1660 m.w.e. and 3280 m.w.e. were 3 × 10−⁵ and 10−⁵ of that at the surface; no cosmic ray events were observed at 5060 m.w.e. The results suggest a steepening of the energy spectrum in the region of 10¹² ev. The most probable energy loss of μ-mesons which had a mean energy of about 3×10¹¹ ev was found to be not significantly higher than that of minimum ionizing particles.