Dissertation / PhD Thesis

PUBDB-2026-02158

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Development of a wavefront and coherence analysis platform for online beam characterization at next generation synchrotron beamlines

Sharma, A.Extern*DESY*

2026

Abstract: The increasing demands on spatial resolution and beam stability in next-generation synchrotron sources such as PETRA~IV necessitate advanced techniques for wavefront characterization and coherence analysis. This thesis presents a comprehensive framework for quantitative wavefront reconstruction and coherence measurement, developed with in-house computational tools optimized for synchrotron beamlines. The work bridges fundamental wave theory with practical beam diagnostics, addressing the need for accurate, non-invasive characterization of partially coherent X-ray beams.The study begins with a theoretical foundation of wave interactions, diffraction, and scattering phenomena, establishing the link between electromagnetic field propagation and the resulting intensity distributions. This serves as the analytical groundwork for developing near-field experimental approaches. Leveraging Talbot imaging and speckle-based interferometry, the thesis investigates wavefront reconstruction methodologies capable of resolving sub-microradian phase deviations. In particular, the implementation of the Frankot--Chellappa projection and Fourier expansion methods enables precise integration of phase gradients into quantitative wavefront maps.A major contribution of this work lies in the formulation and validation of a scalable software framework for wavefront reconstruction, supporting simulation-driven analysis and experimental benchmarking. The framework is applied to study the impact of system parameters, including Talbot distance, detector noise, operating energy, and optical misalignments. Furthermore, coherence analysis is extended through a hybrid near-field heterodyne speckle method, offering 2D coherence mapping with enhanced sensitivity to small phase perturbations.The final sections integrate simulation and experimental data to extract source coherence parameters, quantify detector modulation transfer functions, and validate the derived phase and coherence metrics through cross-comparison with established ptychographic and coded-mask reconstruction methods. The outcomes provide a validated methodology for beam quality assessment and optics characterization that aligns with the precision requirements of PETRA~IV’s diffraction-limited regime.This work thus contributes a unified experimental--computational framework for X-ray wavefront and coherence analysis, enhancing the diagnostic capabilities of high-brilliance synchrotron facilities. The developed techniques are expected to play a critical role in optimizing beamline optics, improving source performance, and enabling advanced imaging and diffraction experiments in the forthcoming PETRA~IV era.

Note: Dissertation, University of Hamburg, 2026

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Contributing Institute(s):

1. FS-PETRA (FS-PETRA)

Research Program(s):

1. 632 - Materials – Quantum, Complex and Functional Materials (POF4-632) (POF4-632)
2. 6G3 - PETRA III (DESY) (POF4-6G3) (POF4-6G3)

Experiment(s):

1. PETRA Beamline P06 (PETRA III)

Appears in the scientific report 2026

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