Development of new, non-depolarizating and high reflective coatings based on B-C-N compounds for application in fundamental neutron physics

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Research in fundamental physics of the free neutron is one of the key tools for testing the standard model at low energies. Most prominent candidates in this field are the search for an electric dipole moment and the measurement of the neutron lifetime. Significant improvements of the experimental determination using ultracold neutrons (UCN) require reduction of both systematic and statistical errors. New, superthermal sources for ultracold neutrons will enhance the present UCN densities (≈ 40/cm3 at ILL) by about a factor of 10 to 100. At the same time, progress in new neutron guides and neutron storage materials is urgently needed in order to benefit from the higher UCN densities. The crucial parameters to optimize (minimize) here are the neutrons’ critical velocity directly connected to a search for materials with high neutron optical potential (Fermi-potential) and the neutron loss rate. The main goal of this project will be the development of new coating materials, based on B-C-N compounds using highly enriched boron 11, which in contrast to 10B shows a low neutron absorption cross section. Compounds of this type may be a breakthrough in UCN transport and storage. Their use in fundamental neutron physics will increase significantly the performances of upcoming experiments like the neutron electric dipole moment (EDM) experiments, e.g., the n2EDM experiment currently under construction at the Paul Scherrer Institute (PSI).