Neutron Spin Filtering With Dynamically Polarized Protons Using Photo-Excited Triplet States

The use of polarized protons as neutron spin filter is an attractive alternative to the well established neutron polarization techniques. The spin-dependent neutron scattering cross section of protons is usefully large up to the sub-Mev region. Employing optically excited triplet states for the dynamic nuclear polarization (DNP) of the protons, low temperatures and strong magnetic fields are not required and the apparatus can be simplified.The triplet DNP method can be used to build a reliably working neutron spin filter that is operated in 0.3T and about 100K. The high proton polarization of 0.5 obtained is presently still limited by the cooling of the sample. The corresponding analyzing power of A similar to 0.5, obtained with the 5 mm thick sample, can be further increased using a longer sample. Interesting possibilities for a triplet spin filter are opened by the use of neutron optics elements that allow to adapt the beam to the filter cross section.