Roy Holt

The absolute differential polarization of neutrons elastically scattered from a spin-zero nucleus has been measured, for the first time, as a continuous function of energy using a double-scattering technique. The method has been applied to a study of the polarization of neutrons elastically scattered from carbon-12 at eight angles between 20° and 150° in the energy range 2 to 5 MeV. The neutron energies were determined u s in g the nanosecond neutron time-of-flight spectrometer associated with the Yale University Electron Linear Accelerator. The primary intense flux of unpolarized neutrons was generated by the photo-disintegration of natural uranium and lead. The time-of-flight resolution was 0.75 ns. m , corresponding to an energy resolution of 50 keV at 2 MeV. The neutron spin precession method was used to reduce systematic errors to negligible amounts. The measured differential polarizations were analyzed using a general, R-matrix reaction theory and, from this, the neutron total and differential cross sections were predicted. Good agreement with measurements of these cross sections was obtained at all energies and angles in the range 0 to 5 MeV. The predictions of the polarization of neutrons elastically scattered from carbon-12, using a deformed shell-model as a basis, were found to be in reasonable agreement with the present results.