On the Neutrons from the Deuteron-Deuteron Reaction

Abstract

The absolute number of neutrons produced in the deuteron-deuteron reaction (abbreviated $d-d$ 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×${10}^5$ 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±0.2×${10}^5$; 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×${10}^{-26\mathrm{}}$ at 100 kv, increasing to 4×${10}^{-26\mathrm{}}$ at 300 kv and according to the results of Amaldi, Hafstad and Tuve to 1.3×${10}^{-25\mathrm{}}$ 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×${10}^{-24\mathrm{}}$ ${\mathrm{cm}}^2$, only 0.6 that of nitrogen. The cross section of hydrogen for these neutrons is 2.1×${10}^{-24\mathrm{}}$ ${\mathrm{cm}}^2$ in agreement with the theoretical value.