31 research outputs found
Spectrometer for Hard X-Ray Free Electron Laser Based on Diffraction Focusing
X-ray free electron lasers (XFELs) generate sequences of ultra-short,
spatially coherent pulses of x-ray radiation. We propose the diffraction
focusing spectrometer (DFS), which is able to measure the whole energy spectrum
of the radiation of a single XFEL pulse with an energy resolution of . This is much better than for most modern x-ray
spectrometers. Such resolution allows one to resolve the fine spectral
structure of the XFEL pulse. The effect of diffraction focusing occurs in a
single crystal plate due to dynamical scattering, and is similar to focusing in
a Pendry lens made from the metamaterial with a negative refraction index. Such
a spectrometer is easier to operate than those based on bent crystals. We show
that the DFS can be used in a wide energy range from 5 keV to 20 keV.Comment: 9 pages, 8 figures, 2 table
Hydrodynamic Compaction and Sintering of Titanium Filters
This paper describes the development of an equipment for hydrodynamic compaction for production of porous permeable materials and compares the process with the more widely known hydrostatic process. Technical design data, mathematical expressions involved, effect of operating parameters on quality of the sintered product have been discussed
Diffraction based Hanbury Brown and Twiss interferometry performed at a hard x-ray free-electron laser
We demonstrate experimentally Hanbury Brown and Twiss (HBT) interferometry at
a hard X-ray Free Electron Laser (XFEL) on a sample diffraction patterns. This
is different from the traditional approach when HBT interferometry requires
direct beam measurements in absence of the sample. HBT analysis was carried out
on the Bragg peaks from the colloidal crystals measured at Linac Coherent Light
Source (LCLS). We observed high degree (80%) spatial coherence of the full beam
and the pulse duration of the monochromatized beam on the order of 11 fs that
is significantly shorter than expected from the electron bunch measurements.Comment: 32 pages, 10 figures, 2 table
Revealing three-dimensional structure of individual colloidal crystal grain by coherent x-ray diffractive imaging
We present results of a coherent x-ray diffractive imaging experiment
performed on a single colloidal crystal grain. The full three-dimensional (3D)
reciprocal space map measured by an azimuthal rotational scan contained several
orders of Bragg reflections together with the coherent interference signal
between them. Applying the iterative phase retrieval approach, the 3D structure
of the crystal grain was reconstructed and positions of individual colloidal
particles were resolved. As a result, an exact stacking sequence of hexagonal
close-packed layers including planar and linear defects were identified.Comment: 8 pages, 5 figure
Spontaneous supercrystal formation during a strain-engineered metal-insulator transition
Mott metal-insulator transitions possess electronic, magnetic, and structural
degrees of freedom promising next generation energy-efficient electronics. We
report a previously unknown, hierarchically ordered state during a Mott
transition and demonstrate correlated switching of functional electronic
properties. We elucidate in-situ formation of an intrinsic supercrystal in a
Ca2RuO4 thin film. Machine learning-assisted X-ray nanodiffraction together
with electron microscopy reveal multi-scale periodic domain formation at and
below the film transition temperature (TFilm ~ 200-250 K) and a separate
anisotropic spatial structure at and above TFilm. Local resistivity
measurements imply an intrinsic coupling of the supercrystal orientation to the
material's anisotropic conductivity. Our findings add an additional degree of
complexity to the physical understanding of Mott transitions, opening
opportunities for designing materials with tunable electronic properties
Synthesis of nanocrystalline ZnO by the thermal decomposition of [Zn(H2O)(O2C5H7)(2)] in isoamyl alcohol
It was studied how the conditions of heat treatment of a [Zn(H2O)(O2C5H7)(2)] solution in isoamyl alcohol at 120-140A degrees C for 2-60 min affect the precursor decomposition mechanism and the characteristics of the obtained nanocrystalline zinc oxide. In all the cases, the product was a crystalline substance with the wurtzite structure and a size of crystallites of 14-18 nm, which was independent of the synthesis conditions. The thermal behavior and microstructure of the separated and dried nanostructured ZnO powder were investigated. It was determined how the duration and temperature of the heat treatment of the precursor solution affects the microstructure of ZnO coatings dip-coated onto glass substrates using dispersions produced at 120 and 140A degrees C. The nanosized ZnO application procedure was shown to be promising for creating a gas-sensing layer of chemical gas sensors for detecting 1% H-2 ( was 58 +/- 2 at an operating temperature of 300A degrees C) and 4 ppm NO2 ( were 15 +/- 1 and 1.9 +/- 0.1 at operating temperatures of 200 and 300A degrees C, respectively)