Development of the Neutron Reflectometer OffSpec at the Delft University of Technology

Abstract

The fact that a neutron possesses a spin can be used to develop devices to manipulate the polarization of the neutron beam in such a way that much higher resolution (in energy and/or wave vector) can be obtained, without sacrificing intensity. An example of this application is the neutron-spin echo technique. It has been used for several decades for inelastic neutron scattering, where a resolution can be obtained down to the neV range (or times up to several tens of ns) [1]. Since the end of last century, a new application has matured, i.e., the use of spin-echo techniques to label small scattering angles, down to several microradians; see [2,3]. In the preceding paper [4], the application of the spin-echo technique in small-angle scattering is described for the Delft setup, where a monochromatic beam is used (SESANS). Here we will describe a technical solution for a polychromatic beam that will be used in the neutron reflectometer OffSpec for the second target-station at ISIS, which is planned to be operational at the end of 2008. The complicated magnet system to perform the angle labeling is tested in Delft. We describe this system and compare it with the monochromatic version. The different modes for OffSpec are discussed and a few first experimental results are presented.