Yields of Neutrons from Photo-Neutron Sources

Abstract

The number of neutrons emitted per second per curie from ten photo-neutron sources was determined, and they are listed in Table I. Absolute values of yields and cross sections may be in error by 27 percent, but relative values are more reliable. The photo-disintegration cross section for deuterium, ${\sigma }_{\mathrm{D}}(\gamma ,n)$, is found to be 16×${10}^{-28\mathrm{}}$ ${\mathrm{cm}}^2$ at 2.76 Mev. ${\sigma }_{\mathrm{Be}}(\gamma ,n)$ is found to be 7×${10}^{-28\mathrm{}}$ ${\mathrm{cm}}^2$ at 2.76 Mev, and is greater than 9.7×${10}^{-28\mathrm{}}$ ${\mathrm{cm}}^2$ at 1.67 Mev. The more reliable ratios of $\frac{{\sigma }_{\mathrm{Be}}(\gamma ,n)}{{\sigma }_{\mathrm{D}}(\gamma ,n)}$ are found to be 0.43 at 2.76 Mev and 0.30 at 2.50 Mev.