A High Repetition HHG Source of Ultrafast XUV Pulses for the SXP Instrument at the European XFEL

At the European X-ray Free Electron Laser (XFEL) facility a new instrument, the Soft X-ray Port (SXP), has recently started its operation [1]. It is primarily designed for time- and spin-resolved X-ray photo-electron spec-troscopy (TR-XPES), but investigations of complex chemical and bio-inorganic molecular systems with fluores-cence spectroscopy as well as research on highly charged ions are also envisioned [2]. SXP is located downstream of the SASE 3 soft X-ray (SXR) undulator system providing ultrafast photon pulses with variable polarization in the energy range between 260 eV and 3000 eV, at MHz repetition rates. Up to 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sup> photons per pulse are focused at the interaction region in a micrometer spot size resulting in an intensity of more than 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">18</sup> W/cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>. These out-standing specifications enable the complete electronic, chemical and atomic characterization of solids, surfaces and interfaces using TR-XPES. For this purpose, two powerful pump-probe lasers operating in a broad spectral range from the mid-infrared to the ultraviolet region are available. In this contribution, an HHG source is presented, which is designed to operate in conjunction with the SXP instrument as well as with the existing laser infrastructure, providing ultrafast XUV light in the range of 20 eV to 72 eV with MHz repetition rates.