Construction of a high-energy Bonse–Hart ultrasmall-angle x-ray scattering instrument

Abstract

A Bonse–Hart ultrasmall-angle x-ray scattering (USAXS) instrument, employing a synchrotron x-ray source at an energy of 18.86 keV (wavelength λ=0.06573 nm), has been designed, constructed, and tested. Solid as well as suspensions of polystyrene and poly(chlorostyrene) latex spheres were used as reference standards in order to demonstrate the range of this instrument. The USAXS results measured at λ=0.06573 nm were also compared with those from a calibrated Bonse-Hart instrument operating at λ=0.154 nm, i.e., the standard Cu Kα radiation. The higher-energy synchrotron x rays permit us to study absorbing and/or opaque materials having long range inhomogeneities in the order of microns. Furthermore, for many polymer systems, the optimal sample thickness at λ≂0.066 nm is increased to ∼10 mm and thin-walled glass windows become acceptable. Thus, a cylindrical light-scattering cell with a wall thickness of 0.3 mm could be used for both USAXS and laser light scattering measurements. The main hurdle for performing simultaneous static and dynamic light scattering as well as USAXS experiments on polymer solutions and gels with the same sample has been resolved. This capability should open up new frontiers in structural and dynamical studies of systems involving a large range of length scales from angstroms to microns.