Small-angle light scattering: instrumental design and application to particle sizing.

A small-angle integrated light-scattering (SAILS) instrument was designed with the innovative use of a diffusing plate and a charge-coupled device (CCD) camera. In contrast to previous small-angle light-scattering instruments, SAILS has few optical surfaces, allowing the direct recovery of scattering data. Although this approach bypasses the need for aberration corrections that are due to lenses, geometric corrections still apply and are described in detail. The image on the diffusing plate, when photographed by the CCD camera, yields a digitized two-dimensional array, covering the observed scattering angles from 10 to 20 deg. The size distribution of the scattering particles can be obtained by a discrete inversion of the experimentally obtained intensity versus angle-scattering curve. The mean radii obtained from this inversion of SAILS data are compared with nominal sizes given by the manufacturer, and standard errors are computed. The results indicate that SAILS is an ideal instrument for the study of particulates and, because of its fast readout time, is suitable for studying aggregation phenomena. However, because of the limited Q range of SAILS it is currently not suited for the direct determination of particle diameters smaller than approximately 300 nm.