Light-induced structures for (ultra)cold neutron optics

The aim of the project is the search for and development of photo-neutronrefractive materials for neutron-optical components as well as their utilisation as mirrors and beamsplitter for an interferometer to investigate the `phase problem` in neutron scattering. As photo-neutronrefractive materials are termed, which change their neutron optical potential by illumination with light. This characteristic opens up the possibility to spatially modulate the neutron-refractive index in the sub- micrometer range by illumination with a light pattern and makes these substances of particular interest for cold and ultracold neutron-optical applications. In the frame of the project we will optimize application-relevant parameters of the few known photo- neutronrefractive materials, investigate novel materials with respect to their suitability for neutron-optical applications and test promising potential substances for the fabrication of neutron-optical components. On the basis of light-induced gratings in polymethylmethacrylate the set-up of an interferometer will be accomplished which enables detailed investigations on the phase and on the coherence properties of the neutrons scattered by a sample. These interferometric experiments will first be performed on model systems and then extended to structures of scientific relevance.

Optical elements such as mirrors, lenses or beam splitters by which light and in particular its propagation direction can be manipulated, are well known not only in physics but also in everyday life. However, it is a big challenge to design and produce such components for (very) cold neutrons, i.e., matter waves. In the framework of this project we successfully produced structures which serve as mirrors or beam splitters for neutrons within the wavelength range of 1-4 nanometres. This was managed by employing theoretical findings and applying a holographic technique in nanoparticle-polymer composites. Cold neutrons have their peculiar importance as a non-destructive method for investigating biological substances (e.g. DNA). Further the basis for a set-up of improved interferometers for (very) cold neutrons could be laid by using those structures (gratings). Using composites with (superpara)magnetic nanoparticles pioneers a polarizing beam-splitter for neutrons of credit card size and low cost, which could replace the extremely expensive and bulky spin-polarized He-3 analyzers at polarized neutron small angle scattering beamlines.