Spallation of Aluminum by 28-GeV Protons

In the bombardment of Al foils with 28-GeV protons the following cross sections (in mb) for production of the indicated nuclides were obtained: ${\mathrm{Be}}^7$, 7.9±0.5; ${\mathrm{F}}^{18}$, 6.0±0.3; ${\mathrm{C}}^{11}$, 4.7±0.2; ${\mathrm{Na}}^{22}$, 9.8±0.6; ${\mathrm{N}}^{13}$, 1.18±0.07; ${\mathrm{Na}}^{24}$, 8.3±0.5; ${\mathrm{O}}^{15}$, 3.5±1.0; ${\mathrm{Mg}}^{27}$, 0.067±0.006. An upper limit for the ${\mathrm{Ne}}^{24}$ cross section of 0.6 mb was obtained. The ${\mathrm{Mg}}^{27}$ cross section has been corrected for secondary reactions and represents only production by primary protons, presumably by the ($p, p{\pi }^{+}$) reaction. The measurements were made relative to the production of ${\mathrm{C}}^{11}$ activity in polyethylene and polystyrene foils. The production of ${\mathrm{Be}}^7$ in the plastic foils was also observed and corresponds to a cross section of 7.7±0.4 mb per carbon nucleus. By comparison of these cross sections with those at lower bombarding energies, no significant trend of the excitation functions is observable.