Time-of-flight Fourier UCN spectrometer
  We describe a new time-of-flight Fourier spectrometer for investigation of UCN diffraction by a moving grating. The device operates in the regime of a discrete set of modulation frequencies. The results of the first experiments show that the spectrometer may be used for obtaining UCN energy spectra in the energy range of 60$\div$200 neV with a resolution of about 5 neV. The accuracy of determination of the line position was estimated to be several units of $10^{-10}$ eV 
G.V. Kulin, A.I. Frank, S.V. Goryunov, D.V. Kustov, P. Geltenbort, M.   Jentschel, B.Lauss, Ph. Schmidt-Wellenburg
physics.ins-det nucl-ex