A Study of the Elastic Scattering of 2 to 3 MeV Neutrons by 40Ca and 32S Using an Associated Particle Time of Flight Spectrometer
An associated particle time of flight spectrometer based on the D(d,n)3He reaction has been developed using thin deuterated polythene targets. The competing D(d,p)3T was used to monitor the neutron output. The spectrometer has been used to study the elastic scattering of a 2 - 3 MeV neutrons in 40Ca and 32S; in each case the differential elastic scattering cross sections have been measured. In the angular range 20° - 100° in the laboratory frame of reference the results have been compared with an optical model analysis. Values of ¿2 per point of 3.46 and 2.84 for 40C and 32S respectively were obtained.
The elastic scattering of 14 MeV neutrons in large samples of iron.
Abstract The differential cross-sections for the elastic scattering of 14 MeV neutrons from iron have been measured for various sample thicknesses using an associated particle time of flight spectrometer. The variation of the cross-sections with sample thickness has been measured and the results for the smallest sample compared to the predictions of the optical model.
A non-local potential model for the scattering of neutrons by nuclei
Abstract An energy independent non-local optical potential for the elastic scattering of neutrons from nuclei is proposed and the wave-equation solved numerically in its full integro-differential form. The non-local kernel is assumed seperable into a potential form factor times a Gaussian non-locality. The potential form factor, of argument 1/2r+r'), is that of a real Saxon form plus an imaginary term having the shape of the derivative of a Saxon form. A real local spin-orbit potential of the usual Thomas form is included. The parameters of the potential obtained solely from the fitting of the differential cross sections for lead at 7 MeV and 14.5 MeV are used unchanged to calculate the elastic differential cross sections, total and reaction cross sections and polarizations on some elements ranging from Al to Pb at various energies from 0.4 MeV to 24 MeV. The S-wave strength functions and the effective scattering radius R′ are also calculated with the same parameters. The parameters in the usual notations are: real potential V = 71 MeV, r = 1.22 fm, a = 0.65 fm; surface imaginary potential W = 15 MeV, a = 0.47 fm; non-locality β = 0.85 fm; spin-orbit potential, using the nucleon mass in the Thomas form, Uso = 1300 MeV. The energy independence of the potential parameters allows the compound elastic scattering to be included approximately at energies below 4 MeV. The calculations are compared to the data over the whole energy range, and the quality of the agreement with the data is found to be comparable to that obtained previously with energy-dependent local optical potentials. A “local WKB” approximation to the integro-differential equation is derived and found to give an approximate relation between the non-local potential and the equivalent local optical potential.