Cross sections for the spallation production ofBe10in targets of N, Mg, and Si and their astrophysical applications

Abstract

Using an isotope-separator technique, cross sections have been measured for the spallation production of ${}_{}{}^{10}{}_{}{}^{}\mathrm{Be}$ in targets of N, Si, and Mg by protons of 600 MeV and in N by protons of 150 MeV. For 600-MeV protons $\sigma \left({}_{}{}^{10}{}_{}{}^{}\mathrm{Be}\right)=1.3\mathrm{}\pm 0.6,0.7\pm 0.3, \mathrm{and} 1.3\pm 0.4$ mb in N, Si, and Mg respectively. For 150-MeV protons $\sigma \left({}_{}{}^{10}{}_{}{}^{}\mathrm{Be}\right)=0.6\mathrm{}\pm 0.2$ mb in N. The results are discussed in terms of the cosmogenic production of ${}_{}{}^{10}{}_{}{}^{}\mathrm{Be}$ in meteorites, lunar surface, cosmic dust, the earth's atmosphere, and the interstellar gas. It is shown that the Si and Mg components of chondritic material will be important sources of ${}_{}{}^{10}{}_{}{}^{}\mathrm{Be}$, at least as far as the primary galactic flux is concerned. It is also pointed out that the quantitative evaluation of the ${}_{}{}^{10}{}_{}{}^{}\mathrm{Be}$ from lighter nuclei such as oxygen in meteorites and nitrogen in the earth's atmosphere depends strongly on the magnitude of the (unmeasured) secondary-neutron-induced reactions. ${}_{}{}^{10}{}_{}{}^{}\mathrm{Be}$ is shown to be a small fraction of the total Be formed in the spallation of cosmic rays over the whole range of important primary nuclei. Using standard radiochemical techniques cross sections have also been measured for ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$ and ${}_{}{}^{22}{}_{}{}^{}\mathrm{Na}$ production in targets of Si and Mg irradiated by 600-MeV protons. The results differ significantly from previously published values.