A beamline for the x-ray free electron laser (XFEL) of SPring-8 Angstrom Compact free electron LAser (SACLA) provides hard x-ray pulses in the range 4.5-19.5 keV. Its optical system in an optics ...hutch delivers a pink beam below 15 keV with either of two double-mirror systems or a monochromatic beam with a double-crystal monochromator. These XFEL beams are used for various types of measurement at experimental stations, e.g. x-ray diffraction, coherent diffraction imaging, x-ray spectroscopy and pump-and-probe measurement. The experimental stations consist of experimental hutches and control stations, and a femtosecond optical laser which is synchronized with XFEL pulses. Photon diagnostics have been performed for measuring radiation parameters in a shot-by-shot manner.
A method of fabricating multilayer focusing mirrors that can focus X-rays down to 10 nm or less was established in this study. The wavefront aberration induced by multilayer Kirkpatrick-Baez mirror ...optics was measured using a single grating interferometer at a photon energy of 9.1 keV at SPring-8 Angstrom Compact Free Electron Laser (SACLA), and the mirror shape was then directly corrected by employing a differential deposition method. The accuracies of these processes were carefully investigated, considering the accuracy required for diffraction-limited focusing. The wavefront produced by the corrected multilayer focusing mirrors was characterized again in the same manner, revealing that the root mean square of the wavefront aberration was improved from 2.7 (3.3) rad to 0.52 (0.82) rad in the vertical (horizontal) direction. A wave-optical simulator indicated that these wavefront-corrected multilayer focusing mirrors are capable of achieving sub-10-nm X-ray focusing.
Turbulence is ubiquitous in the universe and in fluid dynamics. It influences a wide range of high energy density systems, from inertial confinement fusion to astrophysical-object evolution. ...Understanding this phenomenon is crucial, however, due to limitations in experimental and numerical methods in plasma systems, a complete description of the turbulent spectrum is still lacking. Here, we present the measurement of a turbulent spectrum down to micron scale in a laser-plasma experiment. We use an experimental platform, which couples a high power optical laser, an x-ray free-electron laser and a lithium fluoride crystal, to study the dynamics of a plasma flow with micrometric resolution (~1μm) over a large field of view (>1 mm
). After the evolution of a Rayleigh-Taylor unstable system, we obtain spectra, which are overall consistent with existing turbulent theory, but present unexpected features. This work paves the way towards a better understanding of numerous systems, as it allows the direct comparison of experimental results, theory and numerical simulations.
We present results from the SPring-8 Angstrom Compact free electron LAser facility, where we used a high intensity (∼10^{20} W/cm^{2}) x-ray pump x-ray probe scheme to observe changes in the ionic ...structure of silicon induced by x-ray heating of the electrons. By avoiding Laue spots in the scattering signal from a single crystalline sample, we observe a rapid rise in diffuse scattering and a transition to a disordered, liquidlike state with a structure significantly different from liquid silicon. The disordering occurs within 100 fs of irradiation, a timescale that agrees well with first principles simulations, and is faster than that predicted by purely inertial behavior, suggesting that both the phase change and disordered state reached are dominated by Coulomb forces. This method is capable of observing liquid scattering without masking signal from the ambient solid, allowing the liquid structure to be measured throughout and beyond the phase change.
X-ray second harmonic generation Shwartz, S; Fuchs, M; Hastings, J B ...
Physical review letters,
2014-Apr-25, Letnik:
112, Številka:
16
Journal Article
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We report clear experimental evidence for second harmonic generation at hard x-ray wavelengths. Using a 1.7 Å pumping beam generated by a free electron laser, we observe second harmonic generation in ...diamond. The generated second harmonic is of order 10 times the background radiation, scales quadratically with pump pulse energy, and is generated over a narrow phase-matching condition. Of importance for future experiments, our results indicate that it is possible to observe nonlinear x-ray processes in crystals at pump intensities exceeding 1016 W/cm2.
We report the first results of a search for real photon–photon scattering using X rays. A novel system is developed to split and collide X-ray pulses by applying interferometric techniques. A total ...of 6.5×105 pulses (each containing about 1011 photons) from an X-ray Free-Electron Laser are injected into the system. No scattered events are observed, and an upper limit of 1.7×10−24 m2 (95% C.L.) is obtained on the photon–photon elastic scattering cross section at 6.5 keV.
We have investigated multiphoton multiple ionization dynamics of xenon atoms using a new x-ray free-electron laser facility, SPring-8 Angstrom Compact free electron LAser (SACLA) in Japan, and ...identified that Xe(n+) with n up to 26 is produced at a photon energy of 5.5 keV. The observed high charge states (n≥24) are produced via five-photon absorption, evidencing the occurrence of multiphoton absorption involving deep inner shells. A newly developed theoretical model, which shows good agreement with the experiment, elucidates the complex pathways of sequential electronic decay cascades accessible in heavy atoms. The present study of heavy-atom ionization dynamics in high-intensity hard-x-ray pulses makes a step forward towards molecular structure determination with x-ray free-electron lasers.
We report a search for photon–photon elastic scattering in vacuum in the X-ray region at an energy in the center of mass system of ωcms=6.5keV for which the QED cross section is σQED=2.5×10−47m2. An ...X-ray beam provided by the SACLA X-ray Free Electron Laser is split and the two beamlets are made to collide at right angle, with a total integrated luminosity of (1.24±0.08)×1028m−2. No signal X rays from the elastic scattering that satisfy the correlation between energy and scattering angle were detected. We obtain a 95% C.L. upper limit for the scattering cross section of 1.9×10−27m2 at ωcms=6.5keV. The upper limit is the lowest upper limit obtained so far by keV experiments.
We report on new results of a search for a two-photon interaction with axionlike particles (ALPs). The experiment is carried out at a synchrotron radiation facility using a "light shining through a ...wall (LSW)" technique. For this purpose, we develop a novel pulsed-magnet system, composed of multiple racetrack magnets and a transportable power supply. It produces fields of about 10 T over 0.8 m with a high repetition rate of 0.2 Hz and yields a new method of probing a vacuum with high intensity fields. The data obtained with a total of 27 676 pulses provide a limit on the ALP-two-photon coupling constant that is more stringent by a factor of 5.2 compared to a previous x-ray LSW limit for the ALP mass ≲0.1 eV.
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