Beam splitting characteristics of crystal X-ray Laue diffraction

Abstract

The beam splitter is an optical element that divides a beam of light into two or more subbeams. It is an essential component in many optical experiments. X-ray has the characteristics of short wavelength and strong penetration ability, making it hard to use the optical elements in the visible-light region. Therefore, it is necessary to develop optical elements suitable for X-rays. The atomic layer spacing of the perfect crystal is of the same order of magnitude as the X-ray wavelength, so the crystal diffraction effect can be used to achieve the X-ray modulation. In this paper, the beam splitting characteristics of Laue crystal are analyzed based on X-ray diffraction dynamics and the influences of crystal absorption and incident light angular divergence on the rocking curves of transmission and diffraction are simulated. The modulation of the ratio of the crystal diffraction in-plane angle and crystal thickness to Laue diffraction beam-splitting is presented quantitatively. The results show that the kinematical theory of X-ray diffraction is not enough to analyze the beam splitting characteristics of the crystal. It is necessary to consider the interaction between the wave fields in the crystal and use the Pendellӧsung effect in the dynamical theory of X-ray diffraction to explain the change of the crystal beam-splitting ratio quantitatively. The influence of angular divergence and crystal absorption are considered in the simulation. The angular divergence broadens the bandwidth of the diffraction, thereby reducing diffraction intensity. The crystal absorption results in asymmetry and peak shift of the transmission curve and affects the intensity of diffraction and the intensity of transmission beam. The experimental results show that the non-dispersive (+n,-n) configuration can effectively eliminate the influence of angle divergence. The beam-splitting ratio can be adjusted in a small range (±2%) by changing the in-plane angle and adjusted in a wide range (±75%) by changing the crystal thickness, thereby realizing the quantitative modulation of the intensity of transmission and diffraction beam.

Intensity correlation properties of x-ray beams split with Laue diffraction

“…And the intensity ratio of diffraction beam to transmission beams can be modulated quantitatively based on Pendellösung effect even if the crystal thickness is far more than the extinction distance. [21] Therefore, the paper opts for the Laue case to alleviate the difficulties associated with crystal fabrication.…”

Recent progress on CO2 separation membranes

“…The CO 2 /N 2 selectivity of the combined membrane was lower than that of the pure Pebax1657 membrane, but its CO 2 permeability was five times higher. Xiao et al 82 prepared a polyimide film containing PPO segments by polymerization and studied its gas separation performance. It was found that with an increase in PPO content, the separation coefficient for CO 2 /N 2 increased from 18.77 to 30.12, which indicated that the introduction to PPO segments had a significant effect on the gas separation performance of the membrane material.…”

Development of stress-free Laue diffraction crystal for x-ray beam splitting

“…This allows for quantitative modulation of the intensity ratio between diffraction beam and transmission beam using the Pendellösung effect [8]. Therefore, the development of stress-free Laue diffraction crystals with thin thickness is crucial for high-quality X-ray beam splitting.…”