Compact polarising Soller guides for cold neutrons

Abstract

A compact guide system composed of magnetised thin-suit mirrors deposited on to stretched plastic foils, and suitable for polarising cold neutron beams (wavelengths lambda >0.5 nm) is described. The optical requirements in designing thin-film polarising guides are discussed, and polarising efficiency and transmittance measurements made near the characteristic cut-off wavelength lambda ₊* approximately=0.65 nm are presented. The mechanical design parameters of this guide are compared with those of existing alternative devices: their main advantage is their ability to polarise large beam areas (about 50 mm*40 mm) in relatively small distances (length approximately 180 mm).