Real-time spatial characterization of micrometer-sized X-ray free-electron laser beams focused by bendable mirrors

A real-time and accurate characterization of the X-ray beam size is essential to enable a large variety of different experiments at free-electron laser facilities. Typically, ablative imprints are employed to determine shape and size of μm-focused X-ray beams. The high accuracy of this state-of-the-art method comes at the expense of the time required to perform an ex-situ image analysis. In contrast, diffraction at a curved grating with suitably varying period and orientation forms a magnified image of the X-ray beam, which can be recorded by a 2D pixelated detector providing beam size and pointing jitter in real time. In this manuscript, we compare results obtained with both techniques, address their advantages and limitations, and demonstrate their excellent agreement. We present an extensive characterization of the FEL beam focused to ≈1 μm by two Kirkpatrick-Baez (KB) mirrors, along with optical metrology slope profiles demonstrating their exceptionally high quality. This work provides a systematic and comprehensive study of the accuracy provided by curved gratings in real-time imaging of X-ray beams at a free-electron laser facility. It is applied here to soft X-rays and can be extended to the hard X-ray range. Furthermore, curved gratings, in combination with a suitable detector, can provide spatial properties of μm-focused X-ray beams at MHz repetition rate

The Heisenberg-RIXS instrument at the European XFEL

Resonant Inelastic X-ray Scattering (RIXS) is an ideal X-ray spectroscopy method to push the combination of energy and time resolutions to the Fourier transform ultimate limit, because it is unaffected by the core-hole lifetime energy broadening. And in pump-probe experiments the interaction time is made very short by the same core-hole lifetime. RIXS is very photon hungry so it takes great advantage from high repetition rate pulsed X-ray sources like the European XFEL. The hRIXS instrument is designed for RIXS experiments in the soft X-ray range with energy resolution approaching the Fourier and the Heisenberg limits. It is based on a spherical grating with variable line spacing (VLS) and a position-sensitive 2D detector. Initially, two gratings are installed to adequately cover the whole photon energy range. With optimized spot size on the sample and small pixel detector the energy resolution can be better than 40 meV at any photon energy below 1000 eV. At the SCS instrument of the European XFEL the spectrometer can be easily positioned thanks to air-pads on a high-quality floor, allowing the scattering angle to be continuously adjusted over the 65-145 deg range. It can be coupled to two different sample interaction chamber, one for liquid jets and one for solids, each equipped at the state-of-the-art and compatible for optical laser pumping in collinear geometry. The measured performances, in terms of energy resolution and count rate on the detector, closely match design expectations. hRIXS is open to public users since the summer of 2022.Comment: 43 pages, 12 figures, Supplemental Materia

Photon shot-noise limited transient absorption soft X-ray spectroscopy at the European XFEL

Femtosecond transient soft X-ray Absorption Spectroscopy (XAS) is a very promising technique that can be employed at X-ray Free Electron Lasers (FELs) to investigate out-of-equilibrium dynamics for material and energy research. Here we present a dedicated setup for soft X-rays available at the Spectroscopy & Coherent Scattering (SCS) instrument at the European X-ray Free Electron Laser (EuXFEL). It consists of a beam-splitting off-axis zone plate (BOZ) used in transmission to create three copies of the incoming beam, which are used to measure the transmitted intensity through the excited and unexcited sample, as well as to monitor the incoming intensity. Since these three intensity signals are detected shot-by-shot and simultaneously, this setup allows normalized shot-by-shot analysis of the transmission. For photon detection, the DSSC imaging detector, which is capable of recording up to 800 images at 4.5 MHz frame rate during the FEL burst, is employed and allows approaching the photon shot-noise limit. We review the setup and its capabilities, as well as the online and offline analysis tools provided to users.Comment: 11 figure

First beam at the Extreme Condition Beamline, P02.2, PETRA III, DESY

At the end of November 2010 the Extreme Conditions Beamline (ECB) P02.2 at PETRA III received first beam. In the following weeks we guided the beam over the monochromator into the experimental hutch and onto the laser heating experimental setup. Within this paper we present initial results on monochromator calibration, beam profile and flux measurements of the unfocused beam in comparison to the predicted values. The incident beam was focused with Compound Refractive Lenses (CRL). Powder diffraction images of the CeO2 diffraction standard (NIST) were collected in air and the diamond anvil cell (DAC) on an amorphous silicon area detector bonded with a CsI scintillator from Perkin Elmer. Good diffraction patterns in the DAC were reached in 1 sec collection time. We will discuss the implication of these first results for the possibility of collecting diffraction patterns in sub seconds to conducted time resolved diffraction experiment.Finally, we give an outlook on the further commissioning of the Laser Heating (LH) experiment and the still to be build General Purpose (GP) experimental setup during the next six month. In the fall of 2011 the Extreme Conditions Beamline in start full user operation

Capabilities of the Extreme Conditions Beamline at PETRA III, DESY

At the end of 2010 the Extreme Conditions Beamline (ECB) at PETRA III received first beam and entered the commissioning phase. Since 2012 we are offering beamtime to general users to conduct a variety of different experiments such as powder and single diffraction in the laser/resistive heated and cryogenically cooled Diamond Anvil Cell (DAC). Particularly attractive has been our ability to conducted diffraction experiments at high energies of 60 and 77 keV for pair distribution function (PDF) studies as well as possibility to preform time resolved powder diffraction experiments at 26 and 43 keV with a maximum time resolution of 15 Hz. Within we present some of the current capabilities of the beamline as well as future plans to promote single crystal diffraction at high pressures and temperatures using both monochromatic and pink beam. Finally, we emphasis the present and future time resolved capabilities to conduct powder and single crystal diffraction experiments under dynamic compression and heating conditions in the DAC

Beamline P02.1 at PETRA III for High-Resolution and High-Energy Powder Diffraction

Powder X-ray diffraction techniques largely benefit from the superior beam quality provided by high-brilliance synchrotron light sources in terms of photon flux and angular resolution. The High Resolution Powder Diffraction Beamline P02.1 at the storage ring PETRA III (DESY, Hamburg, Germany) combines these strengths with the power of high-energy X-rays for materials research. The beamline is operated at a fixed photon energy of 60 keV (0.207 Å wavelength). A high-resolution monochromator generates the highly collimated X-ray beam of narrow energy bandwidth. Classic crystal structure determination in reciprocal space at standard and non-ambient conditions are an essential part of the scientific scope as well as total scattering analysis using the real space information of the pair distribution function. Both methods are complemented by in situ capabilities with time-resolution in the sub-second regime owing to the high beam intensity and the advanced detector technology for high-energy X-rays. P02.1's efficiency in solving chemical and crystallographic problems is illustrated by presenting key experiments that were carried out within these fields during the early stage of beamline operation