A new approach to the experiment intended to test the weak equivalence   principle for the neutron
  A new approach to the free fall experiment with UCN is proposed. The idea is that the experiment is performed with neutrons from different equidistant lines of a discrete energy spectrum with a precisely known distance between the lines. Such a spectrum may be formed by neutron diffraction from a moving phase grating. Time-of-flight values of neutrons from different lines of the spectrum must be measured. Neither the initial neutron energy, nor the geometry parameters of the installation are required to be known in this method. 
M.A. Zakharov, G.V. Kulin, A.I. Frank, D.V. Kustov, S.V. Goryunov
nucl-ex physics.ins-det