Speaker
Description
We propose a novel photoelectron streaking technique for free-electron laser facilities, enabling simultaneous, in situ characterization of attosecond soft X-ray pulses and the relativistic electron beam that generates them*.
Our device combines solid-state valence photoemission driven by FEL soft-X-ray pulses with co-propagating, THz-like transient electric field of the electron beam acting as the intrinsic streaking field. Simulations show that the resulting photoelectron trace imprints the temporal structure of both the X-ray pulse and the unipolar beam field into the photoelectron momentum distribution, enabling sub-femtosecond reconstruction. Our design is compatible with FEL beamlines and enables single-shot, non-invasive diagnostics with sensitivity to sub-GV/m electron-beam fields. By using the electron beam itself as the streaking field, the approach removes external synchronization constraints and is intrinsically tolerant to timing jitter. In contrast to electro-optic sampling and laser-driven streaking, this approach provides direct, self-referenced access to beam–photon dynamics without external timing references.
Beyond its intrinsic temporal resolution, it opens a route to quantitative measurements of coupled electron–photon dynamics at relativistic sources, with implications for beam optimization, attosecond pulse engineering**, and the direct observation of correlated ultrafast phenomena in matter, like Auger decay and resonant emission delays in solids.
Funding Agency
This work was supported by the Basic Energy Sciences Accelerator and Detector Research program under Contract No. DE-AC02-76SF00515, and the Office of Basic Energy Science Accelerator
Footnotes
*D. Cesar, A. Acharya, J. P. Cryan, A. Kartsev, M. F. Kling, A. M. Lindenberg, C. D. Pemmaraju, A. D. Poletayev, V. S. Yakovlev, and A. Marinelli, "Ultrafast quantum dynamics driven by the strong space-charge field of a relativistic electron beam," Optica 10, 1-10 (2023)
**Franz, P., Li, S., Driver, T. et al. Terawatt-scale attosecond X-ray pulses from a cascaded superradiant free-electron laser. Nat. Photon. 18, 698–703 (2024).
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