Multilayer neutron monochromator-polarizer based on iron

Abstract

In this paper, a multilayer neutron monochromator-polarizer, consisting of 490 alternating layers of iron and niobium, is proposed. Each layer of iron or niobium has a thickness of 25 Å. The use of thin layers in the structure period improves the quality of the monochromator-polarizer and yields a neutron beam reflected from this structure with high wavelength resolution and a small fraction of minor nonmonochromatic contributions to the intensity of the reflected beam. The fact that the layer thicknesses are the same in the period suppresses even-order Bragg peaks. The parameters of the first-order Bragg peak for eight model neutron monochromators-polarizers based on iron and cobalt are given. It follows from the calculated curve of the coefficient of neutron reflection from the Fe/Nb structure that the first-order Bragg peak has a half width of 1.1%, a relative reflection coefficient of 0.997, and a maximum polarizing efficiency of unity. We also present the first experimental curves of the coefficient of neutron reflection from this structure, depending on the momentum transfer for both spin components of the beam.