Filters

2018 - 201912020 - 20221

More filters

2022 - 20232
Reset filters

Settings

Author: Pfau, Bastian × Subject: Electrons ×

Search Results

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    In situ single-shot diffractive fluence mapping for X-ray free-electron laser pulses
    ([London] : Nature Publishing Group UK, 2018) Schneider, Michael; Günther, Christian M.; Pfau, Bastian; Capotondi, Flavio; Manfredda, Michele; Zangrando, Marco; Mahne, Nicola; Raimondi, Lorenzo; Pedersoli, Emanuele; Naumenko, Denys; Eisebitt, Stefan
    Free-electron lasers (FELs) in the extreme ultraviolet (XUV) and X-ray regime opened up the possibility for experiments at high power densities, in particular allowing for fluence-dependent absorption and scattering experiments to reveal non-linear light-matter interactions at ever shorter wavelengths. Findings of such non-linear effects are met with tremendous interest, but prove difficult to understand and model due to the inherent shot-to-shot fluctuations in photon intensity and the often structured, non-Gaussian spatial intensity profile of a focused FEL beam. Presently, the focused beam is characterized and optimized separately from the actual experiment. Here, we present the simultaneous measurement of XUV diffraction signals from solid samples in tandem with the corresponding single-shot spatial fluence distribution on the actual sample. Our in situ characterization scheme enables direct monitoring of the sample illumination, providing a basis to optimize and quantitatively understand FEL experiments.
  • Thumbnail Image
    Item
    Real-time spatial characterization of micrometer-sized X-ray free-electron laser beams focused by bendable mirrors
    (Washington, DC : Soc., 2022) Mercurio, Giuseppe; Chalupský, Jaromír; Nistea, Ioana-Theodora; Schneider, Michael; Hájková, Věra; Gerasimova, Natalia; Carley, Robert; Cascella, Michele; Le Guyader, Loïc; Mercadier, Laurent; Schlappa, Justine; Setoodehnia, Kiana; Teichmann, Martin; Yaroslavtsev, Alexander; Burian, Tomáš; Vozda, Vojtĕch; Vyšín, Luděk; Wild, Jan; Hickin, David; Silenzi, Alessandro; Stupar, Marijan; Torben Delitz, Jan; Broers, Carsten; Reich, Alexander; Pfau, Bastian; Eisebitt, Stefan; La Civita, Daniele; Sinn, Harald; Vannoni, Maurizio; Alcock, Simon G.; Juha, Libor; Scherz, Andreas
    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.