 The Larmor precession of the neutron spin in a preparation zone with a magnetic field before the sample encodes
the individual velocities of neutrons in the beam into precession angles.Close to the sample the time reversal is effected by a so-called
flipper.A symmetric decoding zone follows such that at its end the precession angle accumulated in the preparation zone is exactly compensated
(provided the sample did not change the neutron velocity, i.e.