Design of a horizontal neutron reflectometer for the European Spallation Source

A design study of a horizontal neutron reflectometer adapted to the general baseline of the long pulse European Spallation Source (ESS) is presented. The instrument layout comprises advanced solutions for the neutron guide, high-resolution pulse shaping and beam bending onto a sample surface being thoroughly adjusted to the properties of the ESS. The length of this instrument is roughly 55 m, enabling delta lambda/lambda resolutions from 0.5% to 10%. The incident beam is focused in horizontal plane to boost measurements of sample sizes of 1 X 1 cm(2) and smaller with potential beam deflection in both downward and upward directions. The primary range of neutron wavelengths utilized by the instrument is 2-7.1 angstrom. If the wavelength range needs to be extended, then this is possible by utilizing only every second (third, fourth) pulse by suppressing all other pulses by the chopper system and thus increase the longest usable wavelength to 12.2 (17.3, 22.4) angstrom. Angles of incidence can be set between 0 degrees and 9 degrees with a total accessible q-range from 4 X 10(-3) angstrom(-1) up to 1 angstrom(-1), while the delta theta/theta resolution can be freely set. The instrument operates in both theta/theta (free liquid surfaces) and theta/2 theta (solid-liquid, air-solid interfaces) geometries. The experimental setup will in particular enable direct studies on ultrathin films (d approximate to 10 angstrom) and buried monolayers to multilayered structures of up to 3000 angstrom total thickness. The horizontal reflectometer will further foster investigations of hierarchical systems from nanometer to micrometer length scale (the latter by off-specular scattering), as well as their kinetics and dynamical properties, in particular under load (shear, pressure, external fields). Polarization and polarization analysis as well as the GISANS option are designed as potential modules to be implemented in the generic instrument layout. The instrument is highly flexible and offers a variety of different measurement modes. With respect to its mechanical components the instrument is exclusively based on current technology. Risks of failure for the chosen setup are minimum. (C) 2014 Elsevier B.V. All rights reserved.