Inhibition of current-spike formation based on longitudinal phase space manipulation for high-repetition-rate X-ray FEL

The formation of a double-horn current profile is challenging issue in the achievement electron bunch with high peak current, especially for high-repetition-rate X-ray free-electron lasers (XFELs) where more nonlinear and intricate beam dynamics propagation involved. Here, we propose to correct longitudinal phase space distortion photoinjector section dual-mode buncher. In combination evolutionary many-objective optimization, this method shown be effective manipulating at injector exit. Furthermore, spike avoided after multi-stage charge density modulation 1.6 kA achieved 100-pC charge. Start-to-end simulations based on Shanghai XFEL extreme light facility demonstrate that proposed scheme can increase FEL pulse energy by than 3 times cascading operation echo-enabled harmonic generation high-gain generation. Moreover, also used shaping beams operating repetition rate meet specific demands different researches.