Total Cross Section forn−pScattering at 20 Mev

The total scattering cross section for neutrons incident on protons has been measured in a good-geometry transmission experiment. The scatterer was hydrogen gas contained in a pressure vessel one meter long, at a pressure of 4000 psi. The resulting cross section is ${\sigma }_t={0.494}_2\pm 0.0025$ barn at a laboratory neutron energy of 19.665±0.026 Mev.