Storage of ultracold neutrons in high resistivity, non-magnetic materials with high Fermi potential

We report the use of deuterated polystyrene (dPS) and deuterated polyethylene (dPE) for the storage of ultracold neutrons (UCN) in an experiment to search for a finite neutron electric dipole moment (nEDM). The Fermi potential of thin film coatings on silicon was measured by cold neutron reflectometry as V(dPS)=(161±10) neV and V(dPE)=(214±10) neV. The UCN loss factor at room temperature of a dPS-coated polystyrene insulator is η=(3±1)×10−4.