Secondary nuclear reactions induced in tin by fast protons

Abstract

Nuclear reactions in which spallation products are captured by the target nucleus have been studied by the radio-chemical method. The excitation functions of secondary reactions leading to product nuclei having charges 2 or 3 units greater than that of the target nuclei have been obtained from measurements of the yields of isotopes of tellurium (Z = 52) and iodine (Z = 53) formed in the 170–660 MeV proton bombardment of tin (Z = 50). The cross-sections of these reactions increase with increasing proton energy: for E_p = 170 MeV, σ(α, xn) and σ(Li, xn) are 18·5 ± 5 and 0·17 ± 0·1 μbarns, respectively; for E_p = 660 MeV, these cross-sections are 50 ± 6·5 and 1·6 ± 0·5 μbarns, respectively. The cross-sections for the capture of lithium nuclei by tin obtained in this work are in good agreement with the results for similar reactions with copper, tin, and lead over a comparable proton energy interval but they are 50 times less than the cross-sections found by Marquez and Perlman. The observed secondary reaction cross-sections for the capture of lithium nuclei can be accounted for only by supposing that the lithium nuclei are emitted with energies greater than they could acquire as a result of fission or evaporation of the target nucleus. Secondary reactions of the type (α, xn) can be accounted for by assuming that the m-particles are emitted as a result of the evaporation process.