Extension of self-seeding scheme with single crystal monochromator to lower energy < 5 keV as a way to generate multi-TW scale pulses at the European XFEL

TL;DR

This paper proposes extending the self-seeding scheme with a single crystal monochromator to generate multi-terawatt, fully-coherent X-ray pulses below 5 keV at the European XFEL, enabling advanced bio-imaging applications.

Contribution

It introduces a novel approach using diamond crystal monochromators and tapering of undulators to produce high-power pulses in the 3.5-5 keV range at the European XFEL.

Findings

Achieves up to 2 TW power in the 3.5-5 keV range

Uses diamond crystals with C(111) Bragg reflection for monochromatization

Demonstrates feasibility with 0.1 nC electron bunch at 17.5 GeV

Abstract

We propose a use of the self-seeding scheme with single crystal monochromator to produce high power, fully-coherent pulses for applications at a dedicated bio-imaging beamline at the European X-ray FEL in the photon energy range between 3.5 keV and 5 keV. We exploit the C(111) Bragg reflection (pi-polarization) in diamond crystals with a thickness of 0.1 mm, and we show that, by tapering the 40 cells of the SASE3 type undulator the FEL power can reach up to 2 TW in the entire photon energy range. The present design assumes the use of a nominal electron bunch with charge 0.1 nC at nominal electron beam energy 17.5 GeV. The main application of the scheme proposed in this work is for single shot imaging of individual protein molecules.