${\mathrm{C}}^{12}(x, xn){\mathrm{C}}^{11}$ and ${\mathrm{Al}}^{27}(x, x2pn){\mathrm{Na}}^{24}$ Cross Sections at High Energies

The ${\mathrm{C}}^{12}(x, xn){\mathrm{C}}^{11}$ and ${\mathrm{Al}}^{27}(x, x2pn){\mathrm{Na}}^{24}$ cross sections were measured for protons (105 to 350 Mev), deuterons (85 to 190 Mev), and alpha particles (380 Mev) by using a $4\pi$ $\beta$ counter to determine the absolute disintegration rate and measuring the incident flux with a Faraday cup. The absolute value of the ${\mathrm{C}}^{12}(p, pn){\mathrm{C}}^{11}$ excitation function was found to be 13% lower than the value previously published for these energies, and was found to be constant between 200 and 350 Mev. The new value of this reaction cross section removes some of the discrepancies between $p-p$ scattering cross sections measured elsewhere and those measured at Berkeley, and affects other experiments that use the reaction as a proton flux monitor. The other cross sections are in reasonable agreement with values determined by comparable methods.