| 1. |
- Glazyrin, K., et al.
(author)
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Sub-micrometer focusing setup for high-pressure crystallography at the Extreme Conditions beamline at PETRA III
- 2022
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In: Journal of Synchrotron Radiation. - Chichester, United Kingdom : Wiley-Blackwell. - 0909-0495 .- 1600-5775. ; 29, s. 654-663
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Journal article (peer-reviewed)abstract
- Scientific tasks aimed at decoding and characterizing complex systems and processes at high pressures set new challenges for modern X-ray diffraction instrumentation in terms of X-ray flux, focal spot size and sample positioning. Presented here are new developments at the Extreme Conditions beamline (P02.2, PETRA III, DESY, Germany) that enable considerable improvements in data collection at very high pressures and small scattering volumes. In particular, the focusing of the X-ray beam to the sub-micrometer level is described, and control of the aberrations of the focusing compound refractive lenses is made possible with the implementation of a correcting phase plate. This device provides a significant enhancement of the signal-to-noise ratio by conditioning the beam shape profile at the focal spot. A new sample alignment system with a small sphere of confusion enables single-crystal data collection from grains of micrometer to sub-micrometer dimensions subjected to pressures as high as 200 GPa. The combination of the technical development of the optical path and the sample alignment system contributes to research and gives benefits on various levels, including rapid and accurate diffraction mapping of samples with sub-micrometer resolution at multimegabar pressures.
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| 2. |
- Hoppe, R., et al.
(author)
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Full characterization of a focused wavefield with sub 100 nm resolution
- 2013
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In: Advances In X-Ray Free-Electron Lasers II. - : SPIE - International Society for Optical Engineering. - 9780819495808 ; , s. 87780G-
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Conference paper (peer-reviewed)abstract
- A hard x-ray free-electron laser (XFEL) provides an x-ray source with an extraordinary high peak-brilliance, a time structure with extremely short pulses and with a large degree of coherence, opening the door to new scientific fields. Many XFEL experiments require the x-ray beam to be focused to nanometer dimensions or, at least, benefit from such a focused beam. A detailed knowledge about the illuminating beam helps to interpret the measurements or is even inevitable to make full use of the focused beam. In this paper we report on focusing an XFEL beam to a transverse size of 125nm and how we applied ptychographic imaging to measure the complex wavefield in the focal plane in terms of phase and amplitude. Propagating the wavefield back and forth we are able to reconstruct the full caustic of the beam, revealing aberrations of the nano-focusing optic. By this method we not only obtain the averaged illumination but also the wavefield of individual XFEL pulses.
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| 3. |
- Seiboth, F., et al.
(author)
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Focusing XFEL SASE pulses by rotationally parabolic refractive x-ray lenses
- 2014
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In: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 499:1, s. 012004-
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Journal article (peer-reviewed)abstract
- Using rotationally parabolic refractive x-ray lenses made of beryllium, we focus hard x-ray free-electron laser pulses of the Linac Coherent Light Source (LCLS) down to a spot size in the 100 nm range. We demonstrated efficient nanofocusing and characterized the nanofocused wave field by ptychographic imaging [A. Schropp, et al., Sci. Rep. 3, 1633 (2013)] in the case of monochromatic LCLS pulses produced by a crystal monochromator that decreases the LCLS bandwidth down to ΔE/E 1.4 · 10-4. The full spectrum of LCLS pulses generated by self-amplified spontaneous emission (SASE), however, fluctuates and has a typical bandwidth of a few per mille (ΔE/E 2 · 10-3). Due to the dispersion in the lens material, a polychromatic nanobeam generated by refractive x-ray lenses is affected by chromatic aberration. After reviewing the chromaticity of refractive x-ray lenses, we discuss the influence of increased bandwidth on the quality of a nanofocused SASE pulse.
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| 4. |
- Uhlén, Fredrik, et al.
(author)
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Damage investigation on tungsten and diamond diffractive optics at a hard x-ray free-electron laser
- 2013
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In: Optics Express. - : Optical Society America. - 1094-4087. ; 21:7, s. 8051-8061
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Journal article (peer-reviewed)abstract
- Focusing hard x-ray free-electron laser radiation with extremely high fluence sets stringent demands on the x-ray optics. Any material placed in an intense x-ray beam is at risk of being damaged. Therefore, it is crucial to find the damage thresholds for focusing optics. In this paper we report experimental results of exposing tungsten and diamond diffractive optics to a prefocused 8.2 keV free-electron laser beam in order to find damage threshold fluence levels. Tungsten nanostructures were damaged at fluence levels above 500 mJ/cm(2). The damage was of mechanical character, caused by thermal stress variations. Diamond nanostructures were affected at a fluence of 59 000 mJ/cm(2). For fluence levels above this, a significant graphitization process was initiated. Scanning Electron Microscopy (SEM) and mu-Raman analysis were used to analyze exposed nanostructures.
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