The Monochromator_pol component is the polarising analogue of Monochromator_flat above – a flat, thin mosaic crystal with spin-dependent (up/down) reflectivity. Its underlying physics (the nuclear/magnetic structure factor formalism, \(F_N\)/\(F_M\), and how they relate to the up/down reflectivities) is described in the User Manual’s Polarisation chapter, section on Polarising Monochromator and Guides (A.2.2), which also documents Pol_mirror, Pol_bender, Pol_guide_mirror and Pol_guide_vmirror – see also section 7 of this manual for the rest of the polarisation-aware component set.