Distribution of Radionuclides from the Interaction of 3- and 29-GeV Protons with Silver

Abstract

Formation cross sections have been measured of about 60 radionuclides isolated from Ag irradiated by 3- and 29-GeV protons. From these data, isobaric charge distributions and mass-yield curves were derived. At 3 GeV, the total isobaric cross sections are \ensuremath{\sim}40 mb near the target, and they decrease to a broad minimum of 4 mb at around $A=30\ensuremath{-}40$. For lighter products the cross sections increase again. At 29 GeV, light- and intermediate-mass products ($20<A<50$) have 20-100% higher cross sections than at 3 GeV; the heavier products ($A>65$) have 10-20% lower yields. Corresponding charge-distribution curves at the two energies are identical except for shifts in absolute magnitude. Comparison of the 3-GeV mass-yield curve with the results of a Monte Carlo calculation based on a cascade-evaporation model shows that such a mechanism can account for the observed cross sections down to about mass 50. The lower-mass products ($15<A<35$) must be formed mainly in a fragmentation or "fission-like" process. Comparisons are made with previous nuclear-emulsion and radiochemical results.