Replika mirrors—Nearly loss-free guides for ultracold neutrons—Measurement technique and first preliminary results

The reflectivity of ultracold neutron (UCN) guides produced with a dedicated technique called Replika has been studied. The guides are made of nickel, where the surface quality was copied from a glass layer. This results in a surface roughness smaller than 10 إ. The reflectivity was measured to be 99.9 (1)%. Those guides can be used at present or future UCN sources to transport UCN over long distances to the respective experiments without significant losses.