100 research outputs found
Non-homogeneous semilinear elliptic equations involving critical Sobolev exponent (Variational Problems and Related Topics)
Upper bound of the best constant of the Trudinger-Moser inequality and its application to the Gagliardo-Nirenberg inequality (Variational Problems and Related Topics)
Upper bound of the best constant of the Trudinger-Moser inequality and its application to the Gagliardo-Nirenberg inequality (Harmonic Analysis and Nonlinear Partial Differential Equations)
A self-referenced in-situ arrival time monitor for X-ray free-electron lasers
We present a novel, highly versatile, and self-referenced arrival time
monitor for measuring the femtosecond time delay between a hard X-ray pulse
from a free-electron laser and an optical laser pulse, measured directly on the
same sample used for pump-probe experiments. Two chirped and picosecond long
optical supercontinuum pulses traverse the sample with a mutually fixed time
delay of 970 fs, while a femtosecond X-ray pulse arrives at an instant in
between both pulses. Behind the sample the supercontinuum pulses are temporally
overlapped to yield near-perfect destructive interference in the absence of the
X-ray pulse. Stimulation of the sample with an X-ray pulse delivers non-zero
contributions at certain optical wavelengths, which serve as a measure of the
relative arrival time of the X-ray pulse with an accuracy of better than 25 fs.
We find an excellent agreement of our monitor with the existing timing
diagnostics at the SACLA XFEL with a Pearson correlation value of 0.98. We
demonstrate a high sensitivity to measure X-ray pulses with pulse energies as
low as 30 J. Using a free-flowing liquid jet as interaction sample ensures
the full replacement of the sample volume for each X-ray/optical event, thus
enabling its utility even at MHz repetition rate XFEL sources
Capturing molecular structural dynamics by 100 ps time-resolved X-ray absorption spectroscopy
An experimental set-up for time-resolved X-ray absorption spectroscopy with 100 ps time resolution at beamline NW14A at the Photon Factory Advanced Ring is presented
Reversible phase transition in laser-shocked 3Y-TZP ceramics observed via nanosecond time-resolved X-ray diffraction
The high-pressure phase stability of the metastable tetragonal zirconia is
still under debate. The transition dynamics of shocked Y2O3 (3 mol%) stabilized
tetragonal zirconia ceramics under laser-shock compression has been directly
studied using nanosecond time-resolved X-ray diffraction. The martensitic phase
transformation to the monoclinic phase, which is the stable phase for pure
zirconia at ambient pressure and room temperature, has been observed during
compression at 5 GPa within 20 ns without any intermediates. This monoclinic
phase reverts back to the tetragonal phase during pressure release. The results
imply that the stabilization effect due to addition of Y2O3 is negated by the
shear stress under compression.Comment: 11 pages, 4 figures, draf
Online dynamic flat-field correction for MHz Microscopy data at European XFEL
The X-ray microscopy technique at the European X-ray free-electron laser
(EuXFEL), operating at a MHz repetition rate, provides superior contrast and
spatial-temporal resolution compared to typical microscopy techniques at other
X-ray sources. In both online visualization and offline data analysis for
microscopy experiments, baseline normalization is essential for further
processing steps such as phase retrieval and modal decomposition. In addition,
access to normalized projections during data acquisition can play an important
role in decision-making and improve the quality of the data. However, the
stochastic nature of XFEL sources hinders the use of existing flat-flied
normalization methods during MHz X-ray microscopy experiments. Here, we present
an online dynamic flat-field correction method based on principal component
analysis of dynamically evolving flat-field images. The method is used for the
normalization of individual X-ray projections and has been implemented as an
online analysis tool at the Single Particles, Clusters, and Biomolecules and
Serial Femtosecond Crystallography (SPB/SFX) instrument of EuXFEL.Comment: 14 pages, 7 figure
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