Ultra-high-gain water-window X-ray laser driven by plasma photocathode wakefield acceleration

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Berman, Lily H. A. and Campbell, David and Hartmann, Edgar and Heinemann, Thomas and Wilson, Thomas and Hidding, Bernhard and Habib, Ahmad Fahim (2025) Ultra-high-gain water-window X-ray laser driven by plasma photocathode wakefield acceleration. Other. arXiv, Ithaca, NY. (https://doi.org/10.48550/arXiv.2507.06403)

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Abstract

X-ray free-electron lasers are large and complex machines, limited by electron beam brightness. Here we show through start-to-end simulations how to realise compact, robust and tunable X-ray lasers in the water window, based on ultra-bright electron beams from plasma wakefield accelerators. First, an ultra-low-emittance electron beam is released by a plasma photocathode in a metre-scale plasma wakefield accelerator. By tuning the beam charge, space-charge forces create a balance between beam fields and wakefields that reduces beam energy spread and improves energy stability - both critical for beam extraction, transport, and focusing into a metre-scale undulator. Here, the resulting ultra-bright beams produce wavelength-tunable, coherent, femtosecond scale photon pulses at ultra-high gain. This regime enables reliable generation of millijoule-gigawatt-class X-ray laser pulses across the water window, offering tunability via the witness beam charge and robustness against variations in plasma wakefield strength. Our findings help democratise access to coherent, high-power, soft X-ray radiation.

ORCID iDs

Berman, Lily H. A., Campbell, David, Hartmann, Edgar, Heinemann, Thomas, Wilson, Thomas ORCID logoORCID: https://orcid.org/0000-0002-6140-7045, Hidding, Bernhard ORCID logoORCID: https://orcid.org/0000-0002-5827-0041 and Habib, Ahmad Fahim ORCID logoORCID: https://orcid.org/0000-0003-2108-8702;
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