Beam dynamics optimization for a higher-brightness photo injector with various photocathode laser pulse shape

Abstract At PITZ, a comprehensive study is conducted to analyse the factors influencing emittance growth in the European XFEL (EuXFEL) continuous wave (CW) setup. Emittance growth due to space charge effects can be mitigated using advanced photocathode laser pulse shapes. To optimize beam quality, multi-objective optimization studies using ASTRA are performed, focusing not only on minimizing emittance but also on maximizing beam brightness for various laser temporal profiles and durations. The optimization is initially carried out for the CW superconducting radio-frequency (SRF) injector section planned for EuXFEL. The optimized cases are then further tracked through start-to-end (S2E) simulations to evaluate their behaviour in the compression stages of EuXFEL. A comparative analysis of gaussian, flattop, ellipsoidal, and inverted parabolic laser profiles is presented, assessing their efficiency not only in terms of emittance but also in 4D and 6D brightness. Finally, the results of the optimized photoinjector setup and the beam properties after the final bunch compression are presented.