Speaker
Description
Next-generation x-ray free-electron lasers operating at MHz repetition rates require fast, flexible source-level actuators for adaptive and autonomous operation.* The photoinjector drive laser, mapping directly onto the electron beam's initial longitudinal phase space, represents a powerful and largely unexplored upstream handle. Here we present the first demonstration of programmable ultraviolet pulse shaping at an operating FEL photoinjector beyond the temporal flattop, implemented at LCLS-II using dispersion-controlled nonlinear synthesis** combined with spatial-light-modulator spectral shaping. Multi-peaked UV modulations are tracked through acceleration, compression, and undulator transport, with laser-imprinted current structure clearly resolved in the compressed beam. Variance-based x-ray temporal reconstruction from transverse deflecting cavity measurements reveals structured emission profiles broadly consistent with the programmed waveform***. These results establish programmable photoinjector shaping as a viable upstream actuator, with implications for on-demand pulse structuring, multiplexed operation, and adaptive control at high-repetition-rate light sources.
Funding Agency
Work supported by DOE BES under DE-AC02-76SF00515, DE-SC0022559, DE-FOA-0002859, DE-FG02-86ER13491; NSF 2231334, 2431903, 2436343; AFOSR FA9550-23-1-0409.
Footnotes
- Zhou et al., PRAB 24, 073401 (2021)
** Lemons et al., Ultrafast Sci. 5, 0112 (2025)
*** Hirschman et al., arXiv:2603.15996 (2026)
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