Comparison of specularly reflecting mirrors for GRANIT

The specularity of ultracold neutron reflection was compared for different “promising” surfaces, including sapphire, silica, silica with carbon (diamond-like), and copper coatings with very small roughness. The probability of total losses of ultracold neutrons (UCN) from a specular trajectory was dominated by diffusive (non-specular) elastic scattering of UCN. In all the cases considered the quality of reflection was sufficiently high for storage of UCN at specular trajectories for the first stage of GRANIT experiment.