Elastic Scattering of 14-MeV Neutrons by Deuterons

Abstract

The differential cross section for the elastic scattering of neutrons by deuterons was measured at a neutron energy of 14.3\ifmmode\pm\else\textpm\fi{}0.2 MeV. The data cover the center-of-mass scattering angles from 13.5\ifmmode^\circ\else\textdegree\fi{} to 158.6\ifmmode^\circ\else\textdegree\fi{}, and the cross section at each angle was measured with a statistical accuracy from 2 to 3%. The scattering sample was a deuterated benzene scintillator coupled to a photomultiplier tube. The time of flight of the scattered neutron was measured by utilizing the recoil-deuteron pulse in the scattering-sample counter to start the timer, and a pulse produced by the scattered neutron in a plastic scintillation counter to stop it. Background events were limited by placing pulse-height restrictions on the pulses from the scattering-sample counter. The data were normalized to the experimentally determined $n\ensuremath{-}p$ scattering cross section at 14.1 MeV. The relative efficiency of the scattered-neutron detector at each energy was determined by performing the experiment with a nondeuterated benzene scintillator in place of the deuterated target. The angles chosen for the $n\ensuremath{-}p$ scattering were those for which the neutron energies were the same as those for the scattering angles chosen for the $n\ensuremath{-}d$ experiment. The known values of the $n\ensuremath{-}p$ scattering cross section were then used to evaluate the $n\ensuremath{-}d$ cross section. The angular distribution shows a deeper minimum near 120\ifmmode^\circ\else\textdegree\fi{} and higher values in the forward directions than is indicated by previous experimental results. An eighth-order polynomial is required to fit the angular distribution, and the value of the total cross section is in good agreement with earlier values.