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.
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).
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
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