Grazing-incidence scattering techniques are powerful tools for studies in surface science. In particular, grazing-incidence neutron scattering (GISANS) provides unique insights in soft-matter systems and magnetic structures, in particular, if they are buried beneath a surface. However, the brilliance of neutron sources is limited hindering the method from becoming widely used.  Particularly, for GISANS there is the possibility for studies of lateral domains in thin film materials with light elements. Examples include lipid films on substrates with controlled curvature, block co-polymer films and studies of lateral structures with magnetic properties. By the use of neutron mirrors, beam shaping and focusing has become can be used to design devices to improve the flux available for GISANS-studies. In this regard we have designed a compact nested mirror focusing device that preserves the lateral resolution along an interface but relaxes the resolution out-of-plane, thus gaining in flux but sacrificing depth resolution.

Fig. 1. Graphical abstract for the designed nested mirror optics. The output of the device has been simulated for the SANS instrument SKADI. These results have then been used for DWBA-simulations of scattering from a nanoparticle film shown in the image.

By combining ray tracing simulations in the software Mcstas with the distorted wave born approximation we show that a portable and easy to install optics increases the flux available for GISANS studies, at least, by one order of magnitude and enables straight forward experiments from free liquid surfaces.

Since the publication of our design and simulation results the device has been constructed together with the company SwissNeutronics. The device has been characterized and an experiment with scattering from a sample (iron filled hexagonal mesoporous aluminium oxide) has been performed at the SANS beamline at the Delft Reactor Institute, Netherlands. Experiments are now being planned other samples, such as magnetic structures and biological films. Use of the optics as a beam expander/compressor is also planned.  With the opening of the ESS the optics will be available at the SKADI-instrument.

This work is part of an Röntgen-Ångström cluster project. Research groups from Uppsala University, Ludwig-Maximillians-Universität, European Spallation Source, Jülich Centre for Neutron Science and Biofisika Institute (UPV/EHU, CSIC) and Fundación Biofisika Bizkaia have been working together.

Contact

Filip Mehler

Phd student
Div. of Material Physics

Dept. of Physics and Astronomy

Uppsala University

Filip.mehler@physics.uu.se