Abstract
The photon beamline vacuum system of the European X-ray Free-Electron Laser Facility (European XFEL) is described. The ultra-large, in total more than 3 km-long, fan-like vacuum system, consisting of three photon beamlines is anessential part of the photon beam transport. It is located between the accelerator vacuum system and the scientific instruments. The main focus of the design was on the efficiency, reliability and robustness of the entire system to ensure the retention of beam properties and the operation of the X-ray optics and X-ray photon diagnostics components. Installation started in late 2014, the first of the three beamline vacuum systems was commissioned in spring 2017, and the last one was operational in mid-2018. The present state and experience from the first years of operation are outlined.
Highlights
The European XFEL is a hard X-ray free-electron laser (X-ray FEL) with MHz repetition rate that started operation in April 2017 (Altarelli et al, 2006; Decking et al, 2020)
The main focus of the design was on the efficiency, reliability and robustness of the entire system to ensure the retention of beam properties and the operation of the X-ray optics and X-ray photon diagnostics components
The X-ray beam is delivered to the scientific instruments, which are located in the experiment hall at the end of the underground tunnels (Tschentscher et al, 2017)
Summary
The European XFEL is a hard X-ray free-electron laser (X-ray FEL) with MHz repetition rate that started operation in April 2017 (Altarelli et al, 2006; Decking et al, 2020). The X-ray beam is delivered to the scientific instruments, which are located in the experiment hall at the end of the underground tunnels (Tschentscher et al, 2017). A horizontal separation of 1.4 m is required for the vacuum pipes close to the end of the tunnel to have enough space for the scientific instruments in the adjacent experiment hall. At the hard X-ray beamlines, this leads to long vacuum pipe sections to bridge the distance of about 550 m between distribution mirror and instruments, as the deflecting angles are very small. To reduce the photon beam intensity of the soft X-ray beamline SASE3 (Fig. 1) in a controllable way, a gas attenuator device has been developed and installed.
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