321 research outputs found
Some data on the content of organic carbon in rivers in the winter months. [Translation from: Gidrochim. Mat. 23, 36-38, 1955]
Observations are reported on the content of organic matter in the Moscow region in 1941. Some data is given on alkalinity, oxygen content and colourisation of the rivers
Optical properties of the organic substances from aqueous humus surface waters. [Translation from: Gidrochim. Mat. 23, 31-35, 1955]
Dissolved organic matter, especially turf and peat, is repsonsible for the colouration of water. The reported study tried to determine the nature of the colouring agent or organic matter by the establishment of a relationship between the intensity of colouration and the total organic matter content. 44 waters from different sources were examined
Controlled mechanical ventilation tactics in patients with polytrauma during interhospital transportation to the specialized center
Water Window Ptychographic Imaging with Characterized Coherent X-rays
We report on a ptychographical coherent diffractive imaging experiment in the
water window with focused soft X-rays at . An X-ray beam with
high degree of coherence was selected for ptychography at the P04 beamline of
the PETRA III synchrotron radiation source. We measured the beam coherence with
the newly developed non-redundant array method. A pinhole
in size selected the coherent part of the beam and was used for ptychographic
measurements of a lithographically manufactured test sample and fossil diatom.
The achieved resolution was for the test sample and only
limited by the size of the detector. The diatom was imaged at a resolution
better than .Comment: 22 pages. 7 figure
Intensity interferometry of single x-ray pulses from a synchrotron storage ring
We report on measurements of second-order intensity correlations at the high
brilliance storage ring PETRA III using a prototype of the newly developed
Adaptive Gain Integrating Pixel Detector (AGIPD). The detector recorded
individual synchrotron radiation pulses with an x-ray photon energy of 14.4 keV
and repetition rate of about 5 MHz. The second-order intensity correlation
function was measured simultaneously at different spatial separations that
allowed to determine the transverse coherence length at these x-ray energies.
The measured values are in a good agreement with theoretical simulations based
on the Gaussian Schell-model.Comment: 16 pages, 6 figures, 42 reference
Statistical properties of a free-electron laser revealed by the Hanbury Brown and Twiss interferometry
We present a comprehensive experimental analysis of statistical properties of
the self-amplified spontaneous emission (SASE) free-electron laser (FEL) FLASH
at DESY in Hamburg by means of Hanbury Brown and Twiss (HBT) interferometry.
The experiments were performed at the FEL wavelengths of 5.5 nm, 13.4 nm, and
20.8 nm. We determined the 2-nd order intensity correlation function for all
wavelengths and different operation conditions of FLASH. In all experiments a
high degree of spatial coherence (above 50%) was obtained. Our analysis
performed in spatial and spectral domains provided us with the independent
measurements of an average pulse duration of the FEL that were below 60 fs. To
explain complicated behaviour of the 2-nd order intensity correlation function
we developed advanced theoretical model that includes the presence of multiple
beams and external positional jitter of the FEL pulses. By this analysis we
determined that in most experiments several beams were present in radiating
field and in one of the experiments external positional jitter was about 25% of
the beam size. We envision that methods developed in our study will be used
widely for analysis and diagnostics of the FEL radiation.Comment: 29 pages, 14 figures, 3 table
Seeded x-ray free-electron laser generating radiation with laser statistical properties
The invention of optical lasers led to a revolution in the field of optics
and even to the creation of completely new fields of research such as quantum
optics. The reason was their unique statistical and coherence properties. The
newly emerging, short-wavelength free-electron lasers (FELs) are sources of
very bright coherent extreme-ultraviolet (XUV) and x-ray radiation with pulse
durations on the order of femtoseconds, and are presently considered to be
laser sources at these energies. Most existing FELs are highly spatially
coherent but in spite of their name, they behave statistically as chaotic
sources. Here, we demonstrate experimentally, by combining Hanbury Brown and
Twiss (HBT) interferometry with spectral measurements that the seeded XUV FERMI
FEL-2 source does indeed behave statistically as a laser. The first steps have
been taken towards exploiting the first-order coherence of FELs, and the
present work opens the way to quantum optics experiments that strongly rely on
high-order statistical properties of the radiation.Comment: 24 pages, 10 figures, 37 reference
Characterization of Spatial Coherence of Synchrotron Radiation with Non-Redundant Arrays of Apertures
We present a method to characterize the spatial coherence of soft X-ray
radiation from a single diffraction pattern. The technique is based on
scattering from non-redundant arrays (NRA) of slits and records the degree of
spatial coherence at several relative separations from one to 15 microns,
simultaneously. Using NRAs we measured the transverse coherence of the X-ray
beam at the XUV X-ray beamline P04 of the PETRA III synchrotron storage ring as
a function of different beam parameters. To verify the results obtained with
the NRAs additional Young's double pinhole experiments were conducted and show
good agreement.Comment: 15 pages, 6 figures, 2 tables, 42 reference
Quantum Imaging with Incoherently Scattered Light from a Free-Electron Laser
The advent of accelerator-driven free-electron lasers (FEL) has opened new
avenues for high-resolution structure determination via diffraction methods
that go far beyond conventional x-ray crystallography methods. These techniques
rely on coherent scattering processes that require the maintenance of
first-order coherence of the radiation field throughout the imaging procedure.
Here we show that higher-order degrees of coherence, displayed in the intensity
correlations of incoherently scattered x-rays from an FEL, can be used to image
two-dimensional objects with a spatial resolution close to or even below the
Abbe limit. This constitutes a new approach towards structure determination
based on incoherent processes, including Compton scattering, fluorescence
emission or wavefront distortions, generally considered detrimental for imaging
applications. Our method is an extension of the landmark intensity correlation
measurements of Hanbury Brown and Twiss to higher than second-order paving the
way towards determination of structure and dynamics of matter in regimes where
coherent imaging methods have intrinsic limitations
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