Neutron flux enhancement using spin-dependent interaction potentials

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Abstract
A new method for enhancing the flux of a slow neutron beam is proposed. It is shown that a composite potential consisting of a periodic nuclear modulation and a magnetic spiral of a single chirality can be constructed so that a coherently reflected beam is polarized in one spin eigenstate and, at saturation, has one-half the intensity of an unpolarized incident beam. Although this spin-dependent reflectivity is in itself certainly not unique, what is special is that the contributions to the reflected beam come equally from each of the two incident polarization states via spin-flip and non-spin-flip processes. Consequently, equal fractions of ‘‘spin-up’’ and ‘‘spin-down’’ neutrons are transmitted. Thus, reflected and transmitted beams can be combined incoherently to give an effective conversion of 0.75 of an incident unpolarized beam into a single polarization state. Successive application of such a superposition in conjunction with a straightforward, spatial narrowing of the beam by reflection back into an unpolarized state results in a net flux enhancement.