Effect of intense x ray free electron laser transient gratings on the magnetic domain structure of Tm YIG

In ferromagnets, domain patterns can be controlled globally using magnetic fields or spin polarized currents. In contrast, the local control of the magnetization on the nanometer length scale remains challenging. Here, we demonstrate how magnetic domain patterns in a Tm doped yttrium iron garnet Tm YIG thin film with perpendicular magnetic anisotropy can be permanently and locally imprinted by high intensity photon pulses of a hard x ray transient grating XTG . Micromagnetic simulations provide a qualitative understanding of the observed changes in the orientation of magnetic domains in Tm YIG and XTG induced changes. The presented results offer a route for the local manipulation of the magnetic state using hard XT

Characterization of the eLine ASICs in prototype detector systems for LCLS

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Single-shot X-ray Absorption Spectroscopy at X-ray Free Electron Lasers

X-ray Absorption Spectroscopy (XAS) is a widely used X-ray diagnostic method. While synchrotrons have large communities of XAS users, its use on X-Ray Free Electron Lasers (XFEL) facilities has been rather limited. At a first glance, the relatively narrow bandwidth and the highly fluctuating spectral structure of XFEL sources seem to prevent high-quality XAS measurements without accumulating over many shots. Here, we demonstrate for the first time the collection of single-shot XAS spectra on an XFEL, with error bars of only a few percent, over tens of eV. We show how this technique can be extended over wider spectral ranges towards Extended X-ray Absorption Fine Structure (EXAFS) measurements, by concatenating a few tens of single-shot measurements. Such results open indisputable perspectives for future femtosecond time resolved XAS studies, especially for transient processes that can be initiated at low repetition rate

Single-shot X-ray absorption spectroscopy at X-ray free electron lasers

International audienceX-ray Absorption Spectroscopy (XAS) is a widely used diagnostic method for studying electronic and structural properties of matter. At first glance, the relatively narrow bandwidth highly fluctuating spectral structure Free Electron Lasers (XFEL) sources seem to require accumulation over many shots achieve high data quality. To date best approach implementing XAS at XFEL facilities has been using monochromators scan photon energy across desired range. While this possible easily reproducible samples such as liquids, it incompatible with important systems. Here, we demonstrate collection single-shot spectra 10s eV an source, error bars only few percent. We additionally show how extend technique wider ranges towards Extended Fine Structure measurements, by concatenating tens measurements. Our results pave way future studies XFELs, in particular those femtosecond regime. This advance envisioned be especially transient processes that can initiated lower repetition rates, difficult reproduce excitation conditions, or rare samples, encountered high-energy density physics

Raster microdiffraction with synchrotron radiation of hydrated biopolymers with nanometre step-resolution: case study of starch granules

International audienceX-ray radiation damage propagation is explored for hydrated starch granules in order to reduce the step resolution in raster-microdiffraction experiments to the nanometre range. Radiation damage was induced by synchrotron radiation microbeams of 5, 1 and 0.3 mu m size with similar to 0.1 nm wavelength in B-type potato, Canna edulis and Phajus grandifolius starch granules. A total loss of crystallinity of granules immersed in water was found at a dose of similar to 1.3 photons nm-3. The temperature dependence of radiation damage suggests that primary radiation damage prevails up to about 120 K while secondary radiation damage becomes effective at higher temperatures. Primary radiation damage remains confined to the beam track at 100 K. Propagation of radiation damage beyond the beam track at room temperature is assumed to be due to reactive species generated principally by water radiolysis induced by photoelectrons. By careful dose selection during data collection, raster scans with 500 nm step-resolution could be performed for granules immersed in water

Ultrafast myoglobin structural dynamics observed with an X-ray free-electron laser

Light absorption can trigger biologically relevant protein conformational changes. The light-induced structural rearrangement at the level of a photoexcited chromophore is known to occur in the femtosecond timescale and is expected to propagate through the protein as a quake-like intramolecular motion. Here we report direct experimental evidence of such 'proteinquake' observed in myoglobin through femtosecond X-ray solution scattering measurements performed at the Linac Coherent Light Source X-ray free-electron laser. An ultrafast increase of myoglobin radius of gyration occurs within 1 picosecond and is followed by a delayed protein expansion. As the system approaches equilibrium it undergoes damped oscillations with a ∼3.6-picosecond time period. Our results unambiguously show how initially localized chemical changes can propagate at the level of the global protein conformation in the picosecond timescale. © 2015 Macmillan Publishers Limited. All rights reserved156611sciescopu

Molecular weight dependence of exciton diffusion in poly(3-hexylthiophene)

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