Soft X-ray diffraction patterns measured by a LiF detector with sub-micrometre resolution and an ultimate dynamic...

Area of Science:

• Materials Science
• Optics and Photonics
• Condensed Matter Physics

Background:

• High-intensity coherent X-ray sources like synchrotrons and X-ray free-electron lasers (XFELs) enable advanced imaging techniques such as X-ray diffraction, small-angle X-ray scattering, and phase-contrast imaging.
• The full potential of these techniques is contingent upon detectors with adequate dynamic range and spatial resolution to capture subtle diffraction patterns and scattering signals.

Purpose of the Study:

• To demonstrate the efficacy of lithium fluoride (LiF) as a photoluminescence (PL) imaging detector for X-ray diffraction measurements.
• To evaluate the dynamic range and spatial resolution achievable with LiF detectors in high-intensity X-ray environments.
• To characterize the photoluminescence response of LiF to X-ray irradiation and establish calibration for quantitative analysis.

Main Methods:

• Utilized LiF crystals as photoluminescence detectors at the PETRA III synchrotron facility.
• Recorded X-ray diffraction patterns from a 5 µm circular aperture irradiated with 500 eV X-rays.
• Measured the accumulated dose distribution across the diffraction pattern, from the central maximum to the 16th fringe.
• Analyzed the PL signal using a laser-scanning confocal microscope (Carl Zeiss LSM700) with 488 nm excitation.
• Determined calibration dependencies of the PL signal on excitation intensity and microscope gain.

Main Results:

• Achieved a dynamic range of approximately 10^7 in X-ray diffraction measurements using LiF detectors.
• Demonstrated sub-micrometer spatial resolution, with the last diffraction fringe period measured at 0.8 µm width.
• Quantified the dose variation from 1.7 × 10^5 J cm^-3 in the central maximum to 2 × 10^-2 J cm^-3 in the 16th fringe.
• Established calibration curves for the PL response of LiF to 500 eV X-ray photons and the readout system.

Conclusions:

• LiF crystals are effective photoluminescence detectors for high-resolution, wide dynamic range X-ray imaging.
• The developed LiF-based detection system significantly enhances the capabilities of X-ray diffraction and scattering techniques at synchrotron and XFEL facilities.
• This approach offers a promising pathway for quantitative analysis of X-ray-induced phenomena with improved sensitivity and resolution.