Intense radiation effects observed at European XFEL (Conference Presentation)

Abstract

The X-ray Free Electron Laser (XFEL) is uniquely characterised by its high-brilliance (≥ 10E12 photons/pulse), high spatial coherence and ultrashort (fs) pulses, in the wavelength range spanning over 30 keV from soft to hard x-ray regimes [1,2]. Much of the mainstream interests focus on the powerfulness of the beam it delivers, meanwhile increasing cases of (x-ray) optical and electronical components damages are rapidly emerging – many of them designed and considered to be “radiation tolerant”. This signals that there is still, afterall, insufficient understandings to short- to long-term radiation effects on materials at various degrees. The talk will target on the observations and examples from the European XFEL – one of the most intense XFEL facility in the world. The case study includes some (unintended) instant damages by X-rays, phase modification effects only observed in transmitted pulse profile but not under visible microscope, and controversy results where the long-term radiation fatigues can only explain. I will also note on how such effects could alter the x-ray pulse wavefront (WF) distortion and its effect ranging from radiation deposition mechanism, to (in)ability to reach diffraction limited foci, and limitations to spectral correlations between spectrometers. The general effect goes well beyond ‘bad quality’ beam and may determine the capability and the scientific goal of the experiment altogether. [1] Tschentscher, T. et al, Applied Sciences (Basel) 7, 592 (2017). [2] Decking, W. et al, Nature Photonics 14, 391 (2020).