An efficient gravitational spectrometer for ultracold neutrons

We report on the design and construction of an efficient gravitational spectrometer for ultracold neutrons. The spectrometer is suited to experiments that can greatly profit from knowledge of the neutron energy spectrum without losing available statistics, such as many of the current precision experiments that use ultracold neutrons.The description of the apparatus is complemented by the results of the first test measurements which served as a proof of principle and showed its capability of discriminating between different UCN energy ranges. The measurements showed the expected behavior and are in qualitative agreement with Monte Carlo simulations.