V. V. Kvardakov

Determination of the electron beam size at the Kurchatov synchrotron radiation source using an X-ray refractive lens

The electron beam size in the storage ring of the Kurchatov synchrotron radiation source at 2.5 GeV is determined using an x-ray two-dimensional parabolic refractive lens. The vertical size of the electron beam of the storage ring is found to be 270 μm, which exceeds the corresponding design value 140 μm (at a betatron coupling of 1%). The difference is explained by the imperfect geodetic arrangement of ring elements and the incomplete adjustment of the ring.

Observation of the phase coexistence in -Fe2O3at the Morin transition by synchrotron radiation white beam section topography

Phase coexistence during the spin-reorientation Morin transition in haematite (α-Fe2O3) was investigated by observing phase boundary movements under the influence of temperature and of a magnetic field, using synchrotron radiation white beam section topography. The sample was a high quality (111) platelet shaped crystal, 1.1 mm thick. The phase boundaries are observed to move while remaining nearly parallel to (111). Nucleation of the weak ferromagnetic phase and pinning of interphase boundaries on defects located in the bulk of the crystal were observed. The observed behaviour patterns are discussed in terms of the elastic and magnetostatic energies involved.

Coupling between antiferro and ferromagnetic domains in hematite

Abstract We observe a coupling between the weak ferromagnetic (WF) component and the antiferromagnetic (AF) vector by investigating 180° domains in the WF phase of hematite, in keeping with the symmetry of the Dzialoshinski interaction, and a memory effect associated with the coupling between the signs of the major type domains in the WF and AF phases when going through the Morin transition.

Concentration of Hydrogen in Titanium Measured by Neutron Incoherent Scattering

Mass fractions of hydrogen in titanium matrices have been measured using neutron incoherent scattering (NIS) and compared with results from prompt gamma activation analysis (PGAA). Qualitatively, NIS is a more efficient technique than PGAA which involves neutron absorption, and the former may be suitable for on-line analysis. However, for NIS the scattering contribution comes from both the hydrogen and the matrix, whereas prompt gamma emission has minimal matrix effect. To isolate the signal due to hydrogen scattering, a set of polypropylene films is used to simulate the increasing amount of hydrogen, and the scattered intensity is monitored. From this response, an unknown amount of the hydrogen can be deduced empirically. We have further attempted a first principle calculation of the intensity of the scattered signal from the experimental systems, and have obtained good agreement between calculation and the measurements. The study can be used as a reference for future applications of the scattering method to other hydrogen-in-metal systems.

Nontrivial role of the resolution function in the formation of double-crystal X-ray rocking curves

A theoretical analysis of the shape of the resolution function of an X-ray diffractometer in the double-crystal nondispersive scheme for measuring rocking curves has been performed. It is shown that this function, along with the strong narrow central line (corresponding to the characteristic line to which the collimator crystal and slits in the experimental scheme are tuned) always contains an additional weak satellite, corresponding to the neighboring characteristic line. This feature manifests itself in experimental curves as an additional pseudopeak, whose intensity is comparable with the corresponding diffraction scattering intensity from a sample in the fundamental characteristic line, and whose shape and exact position are set by the resolution function in a specific experimental scheme. It is shown that the exact allowance for the angular and spectral distribution of incident radiation in the double-crystal scheme makes it possible to precisely determine the parameters of the structures studied.

The resolution function of a double-crystal X-ray diffractometer

The shape of the resolution function and the predicted and earlier detected pseudopeak in the diffraction reflection curve (DRC) were experimentally studied in detail as functions of the geometric parameters of a double-crystal dispersion-free measurement system. It has been established that the shapes of the resolution function and the pseudopeak in the DRC weakly depend on the width of the collimation slit so that this optical element, which was earlier considered necessary, is extraneous in this measurement scheme. The physical mechanism of the formation of a pseudopeak in the DRC is illustrated by the example of analyzing the Du Mond diagram.

Double-crystal diffraction imaging with a small effective divergence source: application to the magneto-acoustic vibrations in FeBO3

Ultrasonic standing waves, excited in FeBO3 (111) crystal plates through magneto-elastic coupling, were visualized using monochromatic Bragg diffraction imaging (topography) with synchrotron radiation. The images depend strongly on whether diffraction by the sample occurs in the same plane as in the double-crystal monochromator, or in the perpendicular plane. The observations are explained by taking into account (a) the strong spatial dispersion which prevails because of the small effective divergence (angular size of the source as seen from a point in the specimen), which is less than one microradian in this experiment, and (b) the sample vibration and curvature.

X-Ray “knife” as a submicrometer tool for studying focusing lens quality

A mobile x-ray “knife” developed by the authors is described. The device is intended for determining the profile of the spatial intensity distribution in the ionizing radiation beam. Its automated motion system combines two actuator types. Significant displacements are performed using a goniometric module with a piezoelectric actuator. The angular step of this module is 1 arc second, which corresponds to a linear displacement of 0.97 μm. As a “fine” drive, a rotating module with a piezoelectric column is used. Its linear step can be varied from 0.01 to 1 μm at a total number of steps of 1000. The x-ray knife was experimentally tested at the Kurchatov Center of Synchrotron Radiation for diagnostics of the parameters of a short-focus x-ray lens at a photon energy of 18 keV. In the vertical direction, the width of the profile for the intensity distribution in the beam formed by the lens was 2.4 μm.

Determination of the Electron Beam Size at the Kurchatov Synchrotron Radiation Source Using an Edge Screen

The electron beam size of the 2.5-GeV storage ring of the Kurchatov Synchrotron Radiation Source was measured using a fixed edge screen. The obtained vertical beam size of 190 μm and the corresponding calculated value of 198 μm (for 2% betatron coupling) almost coincide within the experimental error.

Microanalysis station at the Kurchatov synchrotron radiation source

The REFRA station developed, fabricated, and put into operation at the Kurchatov Synchrotron Radiation Center is described. The station is placed on beamline 5.6 of the big storage ring. The station consists of a vertical beam position monitor, an operating shutter, vertical and horizontal slits for the white beam, a monochromator, an alignment stage, an intensity monitor, an EXAFS spectrometer unit, a diffractometer unit, detectors, and a data control and acquisition system. The station operating energy range is 5–30 keV. The station is fully-automated and has been operating with the SR beam since spring 2005. The station units can be reproducibly mounted on the SR beam to provide various research configurations.