A novel broad-band neutron spin filter based on dynamically polarized protons using photo-excited triplet states

Laboratory for Scientific Developments and Novel Materials (LDM), Paul Scherrer Institute, 5232 Villigen PSI, Switzerland

^a e-mail: yifan.quan@psi.ch
^b Now at: CSEM Neuchâtel, 2002 Neuchâtel, Switzerland

Published online: 12 December 2019

Abstract

The use of polarized protons as a broad-band neutron spin filter is an attractive alternative to the well-established neutron polarization techniques, namely polarized ³He gas and super mirrors, since the spin-dependent neutron proton scattering cross-section is large in a broad wavelength range. We have developed a novel neutron spin filter where we create the necessary large proton polarization in a solid with a recent method of dynamic nuclear polarization (DNP) that uses photo-excited triplet states. This requires only moderate experimental means and allows a compact design. In order to quantify the efficiency of the spin filter, we have measured the relevant spin-dependent and spin-independent terms of the neutron scattering cross-section of a naphthalene single crystal. The data allows to estimate the triplet spin filter performance over a broad wavelength range. With the recently achieved proton polarization of 80% the triplet filter compares well with a state of the art ³He filter.