Realization of an advanced super-mirror solid-state neutron polarizer for the instrument PF1B at the Institut Laue-Langevin

In this last of a series of three papers on the development of an advanced solid-state neutron polarizer, we present the final construction of the polarizer and the results of its commissioning. The polarizer uses spin-selective reflection of neutrons by interfaces coated with polarizing super-mirrors. The polarizer is built entirely in-house for the PF1B cold neutron beam facility at the Institut Max von Laue - Paul Langevin (ILL). It has been installed in the PF1B casemate and tested at real conditions. The average transmission for the "good" spin component is measured to be >30 %. The polarization averaged over the capture spectrum reaches a record value of Pn ~ 0.997 for the full angular divergence in the neutron beam, delivered by the H113 neutron guide, and the full wavelength band lambda of 0.3-2.0 nm. This unprecedented performance is due to a series of innovations in the design and fabrication in the following domains: choice of the substrate material, super-mirror and anti-reflecting multilayer coatings, magnetizing field, assembling process. The polarizer is used for user experiments at PF1B since the last reactor cycle in 2020.