High-transformer-ratio plasma-based afterburner for extending X-ray free-electron laser photon energies to ≳50 keV
Abstract
Bright coherent X-rays in the ≳50 keV range are highly desirable for applications in materials science, high-energy-density physics, and nuclear physics, but are difficult to obtain from present X-ray free-electron laser (XFEL) facilities. Plasma-based afterburners offer a compact route to increasing the electron-beam energy, yet high transformer ratio (TR) operation is vulnerable to hosing instability, which can severely degrade the witness beam quality. We propose using a transversely elliptical driver beam to excite an elliptical nonlinear plasma wake with an axially varying focusing gradient, thereby suppressing the witness beam hosing through betatron decoherence. Three-dimensional particle-in-cell simulations show that, for a 3 kA driver and a 2.35 kA witness beam with an rms length of 4 μm and a beam separation of 94 μm (TR ≈ 3), this scheme can accelerate an 8 GeV witness beam to ∼30 GeV while nearly half of the electrons meet the XFEL requirements. Start-to-end simulations show that the resulting beam can drive ≳50 keV XFEL radiation with peak powers of ∼10 GW and durations of ∼10 fs, even when quantum diffusion is included, offering a compact route to extend existing XFEL facilities to higher photon energies.
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BibTeX
@misc{han2026hightransformerratio,
title = {{High-transformer-ratio plasma-based afterburner for extending X-ray free-electron laser photon energies to $\gtrsim$50 keV}},
author = {Songtang Han and Letian Liu and Zhiyan Yang and Zhuo Pan and Xueqing Yan and Xinlu Xu},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2611.05957},
eprint = {2611.05957},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2611.05957},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - High-transformer-ratio plasma-based afterburner for extending X-ray free-electron laser photon energies to ≳50 keV
AU - Songtang Han
AU - Letian Liu
AU - Zhiyan Yang
AU - Zhuo Pan
AU - Xueqing Yan
AU - Xinlu Xu
PY - 2026
DA - 2026/11/04
PB - arXiv
DO - 10.48550/arxiv.2611.05957
UR - https://arxiv.org/abs/2611.05957
AB - Bright coherent X-rays in the ≳50 keV range are highly desirable for applications in materials science, high-energy-density physics, and nuclear physics, but are difficult to obtain from present X-ray free-electron laser (XFEL) facilities. Plasma-based afterburners offer a compact route to increasing the electron-beam energy, yet high transformer ratio (TR) operation is vulnerable to hosing instability, which can severely degrade the witness beam quality. We propose using a transversely elliptical driver beam to excite an elliptical nonlinear plasma wake with an axially varying focusing gradient, thereby suppressing the witness beam hosing through betatron decoherence. Three-dimensional particle-in-cell simulations show that, for a 3 kA driver and a 2.35 kA witness beam with an rms length of 4 μm and a beam separation of 94 μm (TR ≈ 3), this scheme can accelerate an 8 GeV witness beam to ∼30 GeV while nearly half of the electrons meet the XFEL requirements. Start-to-end simulations show that the resulting beam can drive ≳50 keV XFEL radiation with peak powers of ∼10 GW and durations of ∼10 fs, even when quantum diffusion is included, offering a compact route to extend existing XFEL facilities to higher photon energies.
ER -