 Concerning the neutron spins it has a strong analogy to the so-called Hahn echo, well known in the
field of NMR.In both cases the loss of polarization (magnetization) due to dephasing of the spins in time is restored by an effective time reversal operation,
that leads to a restitution of polarization (rephasing).In NMR the dephasing happens due to variation in the local fields at positions of the
nuclei, in NSE the dephasing is due to different neutron velocities in the incoming neutron beam.