Intensity of the cosmic radiation at great depths underground

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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.