Forward scattering of 4·75 }5 neutrons in hydrogenous liquids

Abstract

Small-angle scattering measurements from protonated polystyrene (PSH) and mixtures of deuterated and protonated toluene (C7D8 and C7H8) are presented. The data are compared with the simple 'quasiisotropic' Vineyard model, corrected for third-and higher-order multiple scattering by Monte Carlo methods. This model agrees surprisingly well with all protonated samples over the total thickness range considered. The empirical Jacrot g factor in the expression I(Q) = K(1 -T)g(2)/4n works well over a more limited thickness range. The effective differential cross section can be calculated using Melkonian total cross sections, and this gives an absolute scattered intensity which is 9% lower than a calibration performed at Oak Ridge National Laboratory. Scattering from oversize samples must be back shielded. The model requires an anisotropic kernel to predict D/H toluene mixtures.

General formula for determination of cross-section from measured SANS intensities

“…To the authors opinion supported by the results of Beyster (1968), the main contribution to the anisotropy of the scattering from water embedded in a flat cell positioned perpendicular to the beam may come from multiple scattering for cold neutrons. This interpretation of the anisotropy was also suggested by Boyer & King (1988), who found very good agreement of simulations and measurements on protonated toluene while considering only multiple scattering effect. Actually, the anisotropy of the scattering from water can be explained even when taking into account only the geometry of the cell and a relatively small free path of neutron in water.…”