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Summary: The Vacuum Systems for the European XFEL Vacuum is a pre‐requisite for the successful operation of the European XFEL. Apart of the need to specify pressure levels a large variety of other requirements have to be fulfilled. Specifically, the cleanliness level is noteworthy, as it has to be established in a large system. The respective parts of the particle accelerator and the X‐ray optics are of kilometer length in total. Many of the vacuum components have been developed for the European XFEL to enable the transport of a high quality electron beam. Redundancy and segmentation have been instrumental for the very fast commissioning of the system. The first experiments with X‐ray laser light have been performed successfully. [ABSTRACT FROM AUTHOR]

Electron photoinjectors provide high-brightness electron beams to numerous research applications in physics, chemistry, material, and life sciences. Semiconductor photocathodes are widely used here, as they enable the production of low-emittance beams with variable charge at high repetition rates. One of the key figures of merit of photocathodes is the minimum achievable bunch length. In semiconductor cathodes, this is dominated by scattering effects and varying penetration depths of the extracting photons, which leads to a characteristic electron emission function. We present a method to determine this cathode time response with resolution on the tens of femtoseconds level, breaking the resolution barrier encountered in previous studies. The method is demonstrated with cesium-telluride (Cs2Te) and gold cathodes, revealing response times of (184 ± 41) fs up to (253 ± 58) fs for the semiconductor and an upper limit of (93 ± 17) fs for the metal. Monte Carlo simulations of Cs2Te emission benchmarked to these results give detailed information about the cathode material. [ABSTRACT FROM AUTHOR]