An x-ray regenerative amplifier free-electron laser with a step-tapered-undulator

TL;DR

This paper investigates the performance of an x-ray regenerative amplifier free-electron laser (XRAFEL) with step-tapered undulators, demonstrating its potential for producing stable, high-quality hard x-ray photons compared to SASE-based sources.

Contribution

It introduces the use of step-tapered undulators in XRAFELs and analyzes their performance with different out-coupling methods, advancing the design of stable x-ray light sources.

Findings

Step-tapered undulators improve laser stability and output quality.

Transmissive and hole out-coupling methods affect laser performance.

XRAFELs offer more stable x-ray emission than SASE configurations.

Abstract

Regenerative amplifier x-ray free-electron lasers constitute alternative configurations for fourth generation light sources which are typically operated in self-amplified spontaneous emission (SASE) mode. However, SASE exhibits relatively large fluctuations in the power and spectral properties from shot to shot, whereas XRAFELs provide a much more stable source of hard x-ray photons. Here, we study the performance of an x-ray cavity under consideration at the Stanford Linear Accelerator Facility using both uniform and step-tapered undulators with either transmissive or hole out-coupling.