Observations on Cosmic-Ray Penetrating Showers at High Altitude, Sea Level and Below Ground

Penetrating showers have been investigated, using Geiger counters, at a depth of 30 m. below ground, at sea level and at an altitude of 3,457 m. The influence of the geometry of the absorbers was studied. The transition curves for local showers, corrected for this geometric effect, give the following collision lengths of the generating particles: Pb, 180±40; Al, 85±15; Paraffin similar 80 gm/cm2. These values correspond to a collision cross section close to the geometric cross section of the nuclei. From the results obtained for extensive penetrating showers, it is concluded that most of the penetrating particles in these showers appear to be generated in the atmosphere. In 40 days, no penetrating showers were recorded below ground. Using photographic plates, the density distribution of shower tracks associated with nuclear disintegrations was found to be similar at sea level and 3,457 m.