Polarization analysis in neutron small-angle scattering with a novel triplet dynamic nuclear polarization spin filter

摘要

A novel neutron spin filter whose principle is based on the strong spin dependence of the neutron scattering on protons has been developed. The dimensions of this filter are small, and it works very efficiently and is stable even in inhomogeneous fields. The protons in the naphthalene spin filter crystal are polarized by a recently developed method of dynamic nuclear polarization using photoexcited triplet states. This technique allows the design of a very compact apparatus that can be placed at a close distance to the sample under investigation. The application of this filter as a polarization analyzer is demonstrated in a magnetic small-angle neutron scattering experiment with the measurement of the spin-dependent scattering signals of a CuFeNi alloy. This sample has a pronounced textured structure factor of ferromagnetic precipitates in a paramagnetic matrix. The performance of the spin filter as an analyzer is illustrated by the excellent agreement of the experimental data with simulations based on a model of homogeneously magnetized spherical particles which are ordered in a simple cubic paracrystalline lattice.