The stochastic nature of the self-amplified spontaneous emission (SASE) process in hard x-ray free electron laser (FEL) photon pulse generation often requires online spectral monitoring on a pulse-to-pulse basis. Experimenters and machine operators use the spectral information to better understand their data and guide the experiment, or to optimize the machine parameters through feedbacks to achieve a desired stability. Even experiments that use monochromators benefit from online spectral measurements as it allows the FEL operators to use machine feedbacks on the generated spectra so that the light would not jitter too far out of the monochromator’s acceptance bandwidth.
Online spectrometers have existed for several years in several facilities like LCLS, SACLA, and SwissFEL, and have mostly been used to characterize hard x-rays at photon energies typically above 4 keV. This abstract presents ongoing work on the development of the online tender x-ray spectrometer (TXS)], meant to cover the energy range between 2000 and 4000 eV and fill a gap for online spectral measurements at SwissFEL.
At the European X-ray Free Electron Laser facility one‐ or two‐ Si(111) channel (cut) crystal X‐ray monochromator (Kmonochromator) are planned for photon beam based alignment: gap tuning of the undulator segments and phase tuning of the phase shifters during commissioning and maintenance of the undulators. A prototype device has been built using a single channel-cut crystal and was characterized at PETRAIII synchrotron (at P01, which is the only beamline with two undulator segments) by applying different undulator adjustment methods, intended for the European XFEL, that use imaging and intensity detection. This paper presents the setup and the first results from the experimental qualification of the K-monochromator prototype.
This paper presents the outcome of ray tracing simulations for different optical schemes to be setup at the
European X-ray Free Electron Laser facility (XFEL.EU), Germany: one- or two- channel (cut) crystal X-ray
monochromators (K-Mono; using spontaneous radiation) are planned and designed mainly for photon beam
based alignment, which is gap tuning of the undulator segments and phase tuning of the phase shifters during
commissioning and maintenance of the undulators. The coherent SASE (Self Amplified Spontaneous Emission)
radiation will be monitored pulse-resolved by single-shot spectrometers of which two types are investigated: i) a
three element spectrometer, design proposed by Yabashi et al., which consists of a curved focusing mirror,
followed by a flat analyzer crystal and a 2D-detector.ii) a two element spectrometer based on a reflection zone
plate that reflects and focuses in one step, and a 2D-detector (currently under development).
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