Imaging Measurement of Neutron Attenuation by Small-Angle Neutron Scattering Using Soller Collimator

A new experimental technique to measure spatial distribution of small-angle neutron scattering (SANS) is proposed. Since SANS reflects the nanostructures of samples, high-efficiency mapping of the nanostructures becomes possible. Neutrons scattered at small angle in the transmitted neutron beam are eliminated using a set of Soller collimators at a pulsed neutron source. The eliminated SANS contribution can be observed as neutron attenuation. The first experiment of this technique, SANS imaging, was carried out using monodisperse SiO2 fine particles with three different average diameters: 22, 200, and 1000 nm. The energy-resolved neutron transmission images reveal that the smallest sample shows the largest neutron attenuation at short wavelengths, whereas the neutron attenuation of the sample with the diameter of 200 nm becomes the largest at a wavelength longer than 0.51 nm. Since the difference between the samples is only the nanostructure, this observed wavelength dependence of the neutron attenuation is attributed to the SANS contribution. The difference observed in the neutron attenuation spectra reflects differences in the diameters of the SiO2 fine particles. For quantitative explanation, the effects of sample thickness and geometrical uncertainty in the experiments are necessary to be considered.