Analysis of Coherence Properties of 3-rd Generation Synchrotron Sources and Free-Electron Lasers

TL;DR

This paper presents a theoretical analysis of the transverse coherence properties of third-generation synchrotron sources and XFELs using statistical optics, highlighting mode contributions and coherence behavior at different distances.

Contribution

It introduces a unified theoretical framework for analyzing coherence in synchrotron and XFEL sources, including mode decomposition for XFELs and Gaussian Schell-model for synchrotrons.

Findings

Coherence properties vary with distance from the source.

Few transverse modes dominate the XFEL radiation field.

The model accurately describes the PETRA III and European XFEL sources.

Abstract

A general theoretical approach based on the results of statistical optics is used for the analysis of the transverse coherence properties of 3-rd generation synchrotron sources and x-ray free-electron lasers (XFEL). Correlation properties of the wavefields are calculated at different distances from an equivalent Gaussian Schell-model source. This model is used to describe coherence properties of the five meter undulator source at the synchrotron storage ring PETRA III. In the case of XFEL sources the decomposition of the statistical fields into a sum of independently propagating transverse modes is used for the analysis of the coherence properties of these new sources. A detailed calculation is performed for the parameters of the SASE1 undulator at the European XFEL. It is demonstrated that only a few modes contribute significantly to the total radiation field of that source.