Numerical study of Bragg CDI on thick polycrystalline specimens

Area of Science:

• Materials Science
• Crystallography
• X-ray Optics

Background:

• Bragg coherent diffraction imaging (BCDI) offers high-resolution structural and strain mapping in crystalline materials.
• Traditional BCDI is limited to small, isolated objects, not bulk polycrystalline samples, due to signal overlap.

Purpose of the Study:

• To develop a novel X-ray imaging method applicable to bulk polycrystalline samples.
• To adapt BCDI principles for imaging individual grains or domains within bulk materials.

Main Methods:

• Utilizing a coherent X-ray source and an objective lens for magnification of diffracted beams.
• Employing a far-field 2D detector to monitor the magnified diffraction patterns.
• Implementing a reconstruction principle adapted from BCDI, accounting for magnification and pupil function.

Main Results:

• Numerical simulations demonstrate the feasibility of the proposed imaging method.
• The setup achieves a larger numerical aperture by using an object-lens distance shorter than the focal length.
• The configuration shows robustness against minor lens imperfections and phase errors.

Conclusions:

• The developed method successfully extends high-resolution X-ray imaging to bulk polycrystalline materials.
• Simulations predict a spatial resolution below 20 nm with the proposed objective lens configuration.
• This technique offers a promising advancement for analyzing complex crystalline structures in bulk samples.