Spallation reactions in27Aland56Feinduced by 800 MeV protons

Abstract

Spallation of ${}^{27}\mathrm{Al}$ and ${}^{56}\mathrm{Fe}$ by 800 MeV protons was investigated at the WNR facility of the Los Alamos National Laboratory. Production cross sections for a considerable number of residual nuclei were determined for both targets by use of three different methods. Because of the specific time structure of the WNR beams it was possible to observe both the prompt \ensuremath{\gamma} radiation resulting from the final stage of the spallation reaction and the \ensuremath{\gamma} radiation due to the decay of short-lived residual nuclei by delayed \ensuremath{\gamma}-ray spectroscopy. The activity of long-lived residual nuclei was measured several weeks after the irradiation with a calibrated high-purity Ge \ensuremath{\gamma}-ray detector. In the prompt \ensuremath{\gamma}-ray spectrum it was possible to observe the transitions from the first excited ${2}^{+}$ state to the ground state for all even-even nuclei strongly populated in the spallation reactions and, from these data, to deduce the production cross sections of these mostly stable nuclei in addition to the short- and long-lived residual nuclei mentioned before. In this way production cross sections for 36 nuclides from the proton interactions with ${}^{56}\mathrm{Fe}$ and for 12 nuclides in the case of ${}^{27}\mathrm{Al}$ could be measured; in addition, meaningful upper limits were obtained for a number of further nuclides in both cases. The results are in reasonable agreement with previous measurements obtained by different methods; for a number of nuclides, production cross sections were determined for the first time. The present data as well as the results of all previous measurements are compared with the predictions of the semiempirical systematics and with quantum molecular dynamics calculations.