Neutron diffraction and optics in noncentrosymmetric crystals: New feasibility of a search for neutron EDM

Abstract

Recently strong electric fields (up to 10 9 V/cm) have been discovered, which affect the neutrons moving in noncentrosymmetric crystals. Such fields allow for new polarization phenomena in the neutron diffraction and in the optics and provide, for instance, a new method of a search for the neutron electric dipole moment (EDM). A strong interplanar electric field of the crystal and a sufficiently long time for the neutron passage through the crystal for Bragg angle close to π/2 in the case of Laue diffraction make it possible to exceed the sensitivity achieved with the magnetic resonance method using ultra cold neutrons (UCN method). The pilot setup has been created and mounted at the neutron beam at the WWR-M reactor in Gatchina. It allows to study the optics and the dynamical diffraction of polarized neutrons in thick (1–10 cm) crystals, using the direct diffraction beam and Bragg angles close to 90°. The first experimental results are discussed on observing new effects in both the Laue diffraction and the optics of cold neutrons. These results confirm the opportunity to increase more than by an order of magnitude the sensitivity of the method to neutron EDM, using the diffraction angles close to 90° and give a real prospect to exceed the sensitivity of the UCN method.