104 research outputs found
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
Revealing the origins of vortex cavitation in a Venturi tube by high speed X-ray imaging
Hydrodynamic cavitation is useful in many processing applications, for example, in chemical reactors, water treatment and biochemical engineering. An important type of hydrodynamic cavitation that occurs in a Venturi tube is vortex cavitation known to cause luminescence whose intensity is closely related to the size and number of cavitation events. However, the mechanistic origins of bubbles constituting vortex cavitation remains unclear, although it has been concluded that the pressure fields generated by the cavitation collapse strongly depends on the bubble geometry. The common view is that vortex cavitation consists of numerous small spherical bubbles. In the present paper, aspects of vortex cavitation arising in a Venturi tube were visualized using high-speed X-ray imaging at SPring-8 and European XFEL. It was discovered that vortex cavitation in a Venturi tube consisted of angulated rather than spherical bubbles. The tangential velocity of the surface of vortex cavitation was assessed considering the Rankine vortex model
- …