Background Sub-femtosecond electron beams offer enormous promise for furthering ultrafast research, including ultrafast electron diffraction and free-electron lasers. However, traditional compression techniques are essentially constrained by slice energy spread and cannot stably produce sub-femtosecond electron beams.
Purpose This work proposes a unique compression strategy based on a Transverse Gradient Undulator (TGU). The slice energy spread is actively reduced by taking advantage of the link between transverse position and energy modulation in the TGU, hence breaking the compression limit.
Methods Theoretical proof has been provided of the suppression effect of TGU on slice energy spread, with confirmation of the relevant parameters influencing this effect. A complete compression beamline has been designed, and numerical simulations conducted.
Results Numerical simulations show that the proposed approach may compress the electron beam from 50 fs to less than 1 fs, with a compression factor over 52.09. Although phase jitter in the electron gun’s electric field affects the final compression pulse length, adjusting the modulation laser parameters of the TGU can effectively improve the compression results.
Conclusions This study confirms that the TGU with flexible tunability and suppression of slice energy dispersion can be explored to be applied in ultrafast science research.
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