EVAPORATION NEUTRONS FROM COSMIC RAY NUCLEAR INTERACTIONS IN VARIOUS ELEMENTS

Abstract

Production of evaporation neutrons from nuclear interactions by cosmic rays is investigated in C, Al, Fe, Cu, Pb, and Bi. Boron trifluoride counters in a paraffin moderator in which the element under study is placed serve to detect the evaporation neutrons. A cosmic ray telescope allows the consideration of ionizing neutron-producing particles separately and it is found that of the total neutrons 14.6% are produced by ionizing particles. The mean neutron multiplicities are worked out and they show an increase with the two-thirds power of the atomic weight of the element in which the interactions take place. Also, the rate of interactions is calculated and this gives the relative interaction cross-sections which are found to increase slightly more with atomic weight than expected if the cross-section is geometric. An estimate of the intensity of the N-component is made and discussed in connection with measurements published by other authors.