Yu. V. Ponomarev

Two-dimensional image magnification in an asymmetric-reflection X-ray microscope

The experimental results on the two-dimensional 20× magnification of an x-ray image obtained in an asymmetric-reflection x-ray microscope with the use of a laboratory source of x rays are discussed. The field of view is determined by the linear sizes of the detector and is equal to 0.5 × 0.5 mm in our experiment for an exposure time of 600 s.

X-ray Microscopy with Asymmetrical Reflection from a Single Crystal

The theoretical and experimental possibilities of obtaining enlarged images in the hard X-ray range with the use of asymmetrical crystals (monochromators) are considered.

Resonance enhancement of diffuse scattering of x-rays in a waveguide heterostructure

The diffuse scattering of x rays in a four-layer waveguide-type heterostructure is investigated. The dynamic enhancement of diffuse scattering is detected experimentally in regions corresponding to the excitation of waveguide modes for both the incident and scattered waves.

X-ray diffuse scattering in multilayer nanostructures

The theory is presented for the resonant diffuse scattering in multilayer nanostructures. The dynamic diffraction effects are taken into account. The computational simulation was constructed from this theory and results are presented and discussed. The angular spectra of the diffuse scattering intensity have been measured experimentally. These results confirm the decisive influence of the dynamic diffraction effects on the process of the resonant diffuse scattering.

ReflEXAFS Spectroscopy of Thin Fe/Sc Multilayers

For two three-layer systems. Sc/Fe/Sc and Fe/Sc/Fe, the fine structure in specular reflected x rays above the Fe K-edge has been investigated experimentally. Computer simulation of ReflEXAFS formation on multilayered structures has been done. Estimates of each layers thickness and density as well as of local atomic order in Fe layers have been obtained. The possibility of ultrathin-layer investigations (down to a few angstroms) has been analyzed.

Soft x-ray production and harmonic generation in femtosecond laser-driven plasma

The picosecond soh X-ray source based on femtosecond laser-driven plasma and spherical multilayred mirrors is developed. Results on VUV laser plasma spectrum. investigation and second harmonic generation are reported.

Dynamics of optically induced dichroism (theory and experiment)

The dynamics of photoinduced dichroism has been experimentally and theoretically (on the basis of the Dumont model) investigated in several ridge-shaped azopolymers. This dynamics was used to reconstruct the dynamics of change in the concentration of trans-isomers and anisotropy of their angular distribution, thickness-averaged for optically thick samples. It is shown that, at the beginning of illumination, the experimental dependences of dichroism are described well within the Dumont model, even disregarding the orientational memory, on the assumption that only some part of trans-isomers are involved in trans-cis isomerization.

X-ray Microscopy of Track Membranes and Biological Objects in the Soft- and Hard-Wavelength Ranges

The methods used to obtain X-ray images of track membranes and various biological objects in the soft (20 nm) and hard (0.2–0.02 nm) wavelength ranges have been considered. In the range of soft X-rays, the images were obtained in a Schwarzshild microscope. In the spectral range of hard X-ray radiation, various methods were used including the use of Fresnel zone plates, asymmetric reflecting crystals, X-ray microradiography and microtomography.

Focusing of picosecond x-ray pulses on the target at power densities up to 1 GW cm-2

The x ray emission from femtosecond laser-driven plasma has been investigated using spherical multilayered mirrors. Different laser pulse widths have been used. The conditions required to produce high intensity x ray emission (up to 1011 W cm-2) from H-like excited ions are discussed.

Ionization waves (strata) in a bounded low-temperature plasma

Resonant properties of a positive column with excitation of induced strata are considered. The mechanism of steady-state amplitude buildup is established, and the conditions for the soft and hard modes of intrinsic strata excitation are obtained. The conditions under which strata are suppressed when the system is acted upon asynchronously by modulation of the discharge currents are investigated. The analysis is carried out for a bounded positive column using the generally accepted model [1, 3].