Depolarization of a neutron beam in laue diffraction by a noncentrosymmetric crystal

The depolarization of a neutron beam executing Laue diffraction in a thick (similar to3.5 cm) noncentrosymmetric alpha -quartz crystal is observed. Th is effect was predicted by us earlier and suggested for measuring the elect ric dipole moment (EDM) of a neutron. The effect is due to an interaction o f the magnetic moment of a moving neutron with a strong crystal electric fi eld, as a result of which the neutron spin rotates in opposite directions f or waves of two types excited in the crystal. The effect is studied for neu tron diffraction by a system of crystallographic (110) planes at Bragg angl es close to pi /2, up to 87 degrees. It is shown that, for a crystal of thi ckness L = 3.5 cm, a direct beam initially polarized along the reciprocal l attice vector becomes depolarized upon diffraction, irrespective of the val ue of Bragg angle, whereas the beam polarized perpendicular to the diffract ion plane retains its polarization. The E tau value determining the sensiti vity of the method to EDM is experimentally estimated. (C) 2000 MAIK "Nauka / Interperiodica".