Properties of the Low Energy Nucleonic Component at Large Atmospheric Depths

This is a report on the absorption properties of the cosmic radiation low energy nucleonic component measured by detectors of disintegration product neutrons as the nucleonic cascade develops deep within the atmosphere. The air absorption mean free path L of the star- or neutron-producing radiation was measured as a function of atmospheric depth x (in g-cm^-2 atmosphere) at the geomagnetic latitudes λ=0^∘, 41^∘, 52^∘. L(x, λ) was obtained for carbon or free atmosphere and for a lead plus carbon pile geometry. As reported earlier, for small x the absorption mfp, L, is dependent upon λ (L is a function of the average energy of the primary nucleons which initiate the nucleonic chain or cascade). However, it is shown by the present measurements that, for $x>600$ g-cm^-2, L→~140 g-cm^-2 independent of latitude λ.The latitude dependence of neutron component intensity was measured at $x=680$ g-cm^-2 (11 200 ft) between λ=0^∘ and 58^∘N. The latitude factor of intensity increase is 2.55. In view of the independence of $L(x)$ on λ at large atmospheric depths this latitude effect is nearly constant down to sea level ($x=1030$). It is shown that at large atmospheric depths neutron production is observed from primary protons with energies as low as {~}1 Bev. The specific yield of neutrons at 11 200 ft has been computed taking into account protons, alpha-particles, and heavier primary nuclei.These measurements resolve discrepancies reported in the literature between high altitude measurements and measurements between sea level and mountain altitudes for the low energy nucleonic component.