The intensity and angular distribution of cosmic rays far underground

An apparatus incorporating scintillators, Geiger counters and neon flash-tubes has been operated at three locations underground in the Kolar Gold Fields, India, to measure the vertical intensity and angular distributions of penetrating cosmic-ray muons. The intensities at the three depths (816, 1812 and 4100 metres water equivalent of rock) are, respectively; (2.39 ± 0.15) × 10^-6, (2.00 ± 0.12) × 10^-7 and (4.63 ± 0.57) × 10^-9 cm^-2 sec^-1 sterad^-1.

The angular distributions are well represented by expressions of the form I(θ) = I(0)cosⁿθ, where θ is the zenith angle, and the values of n at the successive depths are 1.93 ± 0.22, 3.03 ± 0.16 and 5.12 ± 0.82.