A commonly used material for UCN guiding is stainless steel ISO 1.4401 and 1.4404, due to its non magnetic, high stress resistance, availability and quite high neutron optical potential.
Reducing losses and to minimize non-specular reflection they are highly polished to very low roughness far below the guided neutrons wavelength reaching a average transimission of 90% per meter as measured by us at the PF2 EDM and TES beam line, as shown in figure (a). The measurement results and spectra are depicted in my master thesis. Using our switches we also measured the transmission of neutrons at velocities below 3m/s for coated glass guides, as shown in figure (b).
