OPUS: an easy way to push the limits of SANS instruments towards USANS

Abstract

Chemistry and physics have made major advances in recent years, yielding much more complex systems with high hierarchical order across multiple length scales. Accordingly, characterization tools are required that can elucidate the structure of such new materials over all length scales. Simultaneous small-angle neutron scattering (SANS) and ultra-small-angle neutron scattering (USANS) measurements are a unique tool to study such complexity and can be applied to very different fields of science. The OPUS (Option USANS) project is the study of a USANS option for SANS instruments, designed to be very versatile and easy to implement. The main idea is to provide the opportunity to study at the same time, and under the same experimental conditions, complex systems such as polymers, bio-systems, complex fibres and self-assembling systems. More specifically, this work presents the design of an option that could be applied to the suite of SANS instruments at the European Spallation Source (ESS) which will allow exploration of a Q range with a minimum Q down to one order of magnitude lower than the value attainable with the standard SANS instrument at the ESS. The proposed setup, based on the SAMBA (small-angle multi-beam analysis) approach, is very easy and fast to implement on a conventional SANS instrument and constitutes a multi-beam approach involving two multi-slits and a set of lenses near the sample position. This contribution describes all the focusing elements necessary to attain the proposed configuration and a detailed study using McStas simulations to optimize all the parameters involved for two SANS instruments: the future LoKI at the ESS and the present D11 at the Institut Laue–Langevin, the latter used as a benchmark for the model. Simulations performed without taking into account gravity effects show that the multi-beam approach allows extending the Q ranges to 9 × 10−5–7 × 10−4 Å−1 and 5 × 10−5–3 × 10−4 Å−1 for LoKI and D11, respectively.