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.
@article{arxiv.2602.14734,
title = {An x-ray regenerative amplifier free-electron laser with a step-tapered-undulator},
author = {Henry P. Freund and P. J. M. van der Slot and P. G. O'Shea},
journal= {arXiv preprint arXiv:2602.14734},
year = {2026}
}