High accuracy simulations of extreme polarization purity of an X-ray beam for Brewster crystal diffraction

Abstract Recent advancements in powerful pump optical lasers and X-ray free-electron lasers have reignited interest in vacuum birefringence, a phenomenon predicted by quantum electrodynamics (QED). Detecting this subtle effect requires X-ray photons with exceptionally high linear polarization. To meet this need, several polarimeters employing channel-cut crystal monochromators, designed to deflect only σ-polarization while suppressing π-polarization, have been proposed. In this paper, we utilize the upgraded SHADOW code to perform high-accuracy simulations of the linear polarization of X-ray beams by Brewster deflection. Our results highlight a promising beamline configuration capable of achieving linear polarization purity on the order of 10 −13 . We propose using this setup for single-shot experiments to verify vacuum birefringence, offering a novel avenue for probing linear polarization purity in future experimental investigations.