On the Neutrons from the Deuteron-Deuteron Reaction

Abstract

The absolute number of neutrons produced in the deuteron-deuteron reaction (abbreviated $d\ensuremath{-}d$ reaction) has been determined for a target of heavy ice by measuring the scattering cross section of liquid ${\mathrm{N}}_{2}$ and liquid ${\mathrm{O}}_{2}$ for these neutrons, and by counting in an ionization chamber the recoils in ${\mathrm{N}}_{2}$ and in ${\mathrm{O}}_{2}$ gas due to the scattering of the neutrons. Applying the necessary corrections one finds 3.0\ifmmode\times\else\texttimes\fi{}${10}^{5}$ neutrons per second per microampere of deuterons at 100 kv with an estimated uncertainty of 20 percent. The absolute yield of the protons under the same conditions is 2.1\ifmmode\pm\else\textpm\fi{}0.2\ifmmode\times\else\texttimes\fi{}${10}^{5}$; the nuclear process leading to the emission of a proton and a ${\mathrm{H}}^{3}$ nucleus seems therefore somewhat less probable than the alternative process giving a neutron and a ${\mathrm{He}}^{3}$ nucleus. The effective cross section for the neutron-producing reaction is roughly 2\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}26}$ at 100 kv, increasing to 4\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}26}$ at 300 kv and according to the results of Amaldi, Hafstad and Tuve to 1.3\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}25}$ at 700 kv. This reaction is therefore not a "very probable process." The scattering cross section of oxygen for these 2.4 Mev neutrons has the surprisingly low value of 0.75\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}24}$ ${\mathrm{cm}}^{2}$, only 0.6 that of nitrogen. The cross section of hydrogen for these neutrons is 2.1\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}24}$ ${\mathrm{cm}}^{2}$ in agreement with the theoretical value.