Advanced X-ray polarimeter design for nuclear resonant scattering

This work presents the improvements in the design and testing of polarimeters based on channel-cut crystals for nuclear resonant scattering experiments at the 14.4 keV resonance of ⁵⁷Fe. By using four asymmetric reflections at asymmetry angles of α₁ = -28°, α₂ = 28°, α₃ = -28° and α₄ = 28°, the degree of polarization purity could be improved to 2.2 × 10^-9. For users, an advanced polarimeter without beam offset is now available at beamline P01 of the storage ring PETRA III.