Cosmic-Ray Neutron Production in Elements as a Function of Latitude and Altitude

The relative rates of local neutron production in Al, Cu, Sn, and Pb were obtained at geomagnetic latitudes λ=40^∘ and 54^∘ at atmospheric depth 312 g-cm^-2 (30 000 ft pressure altitude). The latitude and altitude dependence of local neutron production in carbon and lead were measured in the latitude interval 0^∘{}-54^∘{} with pile geometries containing BF₃ proportional counters. From these observations several results were obtained: 1. The relative neutron multiplicities in elements were measured and found to be in good agreement with reported low altitude observations.2. A neutron transition maximum in lead at {~}20 g-cm^-2 Pb was obtained at 33 000 ft pressure altitude.3. The absorption mean free path for the neutron producing radiation in lead was 350 g-cm^-2.4. An anomalous air absorption mean free path for the nucleonic component has been found for measurements derived from local neutron production in lead at λ40^∘.5. Aside from the absorption anomaly in elements of high atomic weight A, local neutron production in elements of high A as a function of λ is in fair agreement with the free air neutron latitude effect.6. Local production in carbon as a function of λ and altitude is in agreement with corresponding free air neutron measurements.