Speaker
Description
Plasma accelerators now deliver GeV-class electron beams with sufficient brightness and stability to drive free-electron lasers. Yet they offer a distinctive capability that remains largely unexplored: the phase space of a trapped beam can be shaped in situ, at the moment of injection, on femtosecond timescales. In this talk, we report the generation of multi-GeV electron combs in a plasma wakefield accelerator driven by a 10-GeV electron beam propagating through a helium-confined lithium heat-pipe oven. The comb is a beam consisting of more than ten microbunches spanning 2 to 6 GeV, simultaneously separated in energy and time. Each microbunch exhibits a percent-level energy spread, carries several pC of charge, and has sub-femtosecond length; the energy separation between adjacent microbunches reaches up to 10%. Two mechanisms combine to produce this structure: betatron-driven pinching of the trailing spike of the double-spiked drive beam triggers sequential ionization injection of helium electrons once per half betatron period, while the gentle lithium density gradient maps each bunchlet to a different wake phase. Electrons ionized over ~17 cm are thereby compacted into a beam only a few micrometers long, yielding a mapping factor over 26,000. This work establishes femtosecond, in-situ phase-space shaping in plasma accelerators, paving the way for structured electron beams with tailored energy-time correlations.
Acknowledgements. This work was supported by the U.S. Department of Energy under Contract No. DE-AC02-76SF00515 (FACET-II) and Grant No. DE-SC0010064 (UCLA). Simulations used resources of NERSC under Contract No. DE-AC02-05CH11231 (Award HEP-ERCAP-MP113). S.C., C.A.L., and O.G.F. acknowledge support from ANR (ANR-23-CE30-0011), ERC (101116161), and NFR (313770), respectively.
| Working group | WG3 |
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