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The recent start of the European X-ray Free-Electron Laser (EuXFEL) provides a unique pulsed X-ray source of high spectral brilliance and high photon flux at a high repetition rate and opens the possibility for new scientific opportunities. However, the EuXFEL beam has a high peak power that is converted into a high cyclic thermal load on the optical elements, such as mirrors and monochromators, and is impossible to fully mitigate within the pulse train pattern. In the single crystal based X-ray monochromators, the increase of temperature leads to deformation of the crystal structure which affects the rocking curve and consequently the performance of these devices and the quality of the transmitted X-ray beam. To address the increase of temperature, we propose the use of a diamond channel-cut monochromator as an alternative to the current silicon monochromators. In this work we present the design and parameters of the diamond monochromator, heat load simulations and the surface and crystalline quality characterisation. The heat load simulations indicate a high performance of the monochromator under the pulse train of the EuXFEL and the characterisation demonstrates high crystal quality and its functionality as a double crystal monochromator.

In the X-ray FEL beam transport system, the optic components which have direct contact with the beam, e.g. mirror, absorber and beam shutter, etc., could exceed 10 kW peak heat load on a sub-mm spot. Therefore, the thermo-mechanical performance of these components under the extreme high heat load will limit the maximum allowed pulses for the safety operation of the facility. In this contribution, a selection of multi-scale and multi-physics numerical models using finite element tools is introduced to describe the interaction of X-ray laser beam with different materials, taking into consideration of the multi-coupling of heat transfer, solid mechanics, fluid dynamics and phase transitions. The verified and validated models can be referred to define damage threshold of the optic components, and to virtually reproduce the damage mechanism of the materials.

We present the fabrication and characterization of opto-mechanical micro-resonators developed to detect radiation-pressure coupling between light and a macroscopic body. The major achievements of this work are the development of complex high aspect ratio shapes by using the deep-RIE Bosch process and the integration of a high-reflectivity dielectric mirror. The micro-resonators were used as an end-mirror of a Fabry-Perot cavity, attaining an optical finesse of about 6 × 104, and at cryogenic temperature (about 10 K) we measured a mechanical quality factor up to 2 × 106 at about 90 kHz. These features make our devices particularly suitable for experiments on quantum-opto-mechanics.