One of current challenges in softmatter and materials science involves understanding complex systems with high hierarchical order on a manifold length scale. SANS is one of the well established techniques for that purpose, and recently, it further expanded its capabilities by USANS.
OPUS (OPtion USans) is a project dedicated to study an USANS option for the ESS (European Spallation Source) ToF-SANS instruments LoKI and SKADI. The basis of our approach is the Small Angle Multi Beam Analysis proposed by Roland Gähler[1,2]. The fundamental idea is to multiplex the scattering experiment in order to achieve a gain in intensity over an equivalent single pinhole geometry.
We performed McStas simulations in order to project and design a specific optics to adapt the original approach to the characteristics of LoKI and SKADI instruments at ESS: addition of two multi-hole or multi-slits grids, multi lenses and a high resolution detector. Furthermore we extended this ray tracing study to the USANS prototype, based on the same principle, designed for the upgrade of D11 at ILL.
We present results of the McStas-simulated virtual experiments using virtual samples -spheres and cylinders- for both instruments. The effects of set up misalignments, wavelength spread and detector resolution on the ultimate intensity and resolution are also studied. In addition a routine for data reduction and is also presented.
 R. Gähler et al. Proc. SPIE 4785; Advances in Neutron Scattering Instrumentation; Ed: Anderson I., Guerard B. (2002) 153.
 C. Grünzweig et al. App. Phys. Lett., 91(2007) 203504.