Measuring the Count Rate in Underground Locations

The flux of cosmic rays underground is reduced due to the absorption process in the solid rock. Although the contribution from the soil radioactivity is still present, some change in the count rate of a Geiger counter may be observed even a few metres below the ground. The possibility of using such counters at even deeper underground locations could offer interesting activities in this respect. A few considerations about such possibility are discussed and results obtained a few metres below the ground, in a metro station, both with single counters and with Geiger telescopes are reported.