The paper deals with an analytical study of the problem of pore detection and certification in bulk materials by means of X-ray radiography. The optimum thickness of a sample under X-ray absorption investigation of the pores is found, that can be used for an improvement of the signal-to-noise ratio by the proper X-ray photon energy. In the case of low absorption an X-ray coherent beam can be used for production of phase contrast in the radiographic experiments. We present a simple model to calculate the complex value of the wave field formed by the sample. The model includes two dimensionless parameters: the Fresnel number F= a2/(λz), where a is the pore radius, λ is the wavelength, z is the sample-to-detector distance and the phase number Φ = akδ, where k = 2π/λ and δ is the decrement of the real part of material's relative permittivity. The detailed analysis of the field structure is given with an estimation of the optimal position of the detector. The numerical simulation results are presented as well, which were obtained for the Gaussian type of the pore shape function. The stationary phase method of higher orders has been proven to simplify the Fresnel integral. The developed qualitative visualization of the pores with the help of phase contrast X-ray imaging complements other modern methods of monitoring porous-sensitive materials.
There is a quest for new knowledge and methods to study various materials and processes on surfaces and interfaces at the nanoscale. It concerns ablation, phase transitions, physical and chemical transformations, dissolution, selforganization etc. Obviously, to achieve an appropriate resolution it is necessary to use a corresponding wavelength . Higher resolution can be obtained with shorter wavelengths. On the other hand, in surface modification, ablation, study of buried interfaces etc. the penetration length of radiation into the materials, which depends on the wavelength and angle of incidence, plays important role... Considering these factors the experimental studies in nano-physics and nanotechnology are usually carried out using X-ray radiation with a photon energy of 0.1-10 keV. As far as surfaces and films are investigated, it is reasonable to use an X-ray microscope operating in the reflection mode. However, in this spectral range a substantial portion of the radiation is reflected only at small grazing angles (e.g. ≤ 10°). Thus, the idea of grazing incidence reflection-mode X-ray microscope has been developed. In this paper, we consider one of possible schemes of such an X-ray microscope. Our analysis and simulation is based on the extension of the Fresnel propagation theory to tilted object problems.
A new type of a high-brilliance X-ray source known as the Thomson X-ray laser-electron generator (TXG) opens new possibilities for materials characterization by X-ray diffraction methods such as high resolution X-ray diffractometry and topography and diffraction analysis at extreme conditions in shear diamond anvil cells. The advantages of the TXG compared to X-ray laboratory sources are a high flux, a quasi-monochromatic, nearly parallel beam and a tunable wavelength. The paper presents examples of applications as well as estimations of typical photon flux and exposure time saving advantages resulted from an implementation of TXG radiation in a home laboratory.
It was medical applications that stimulated F. Carrol in the early 1990s to start the research of on relativistic Thomson scattering X-ray sources, as a part of the infrastructure of the future society. The possibility to use such a source in interventional cardiology is discussed in this paper. The replacement of X-ray tube by relativistic Thomson scattering Xray source is predicted to lower the patient radiation dose by a factor of 3 while image quality remains the same. The required general characteristics of accelerator and laser units are found. They can be reached by existing technology. A semiempirical method for simulation of medical and technical parameters of interventional coronary angiography systems is suggested.
The theory of reflection image formation at coherent slant illumination is specified for the case of confined objects. The
approach is based on the parabolic wave equation with a boundary condition posed on an object surface that is tilted in
respect to the beam k-vector. The result is obtained in the form of a new propagation integral. 3D simulation of coherent
reflection imaging at grazing angles of illumination in a lens optical scheme is performed and discussed.
The determination of EUV optical constants in rare-earth metals is much hampered by the high reactivity and easy air contamination of these materials. The most difficult regions are a long wavelengths part of the EUV interval and the vicinity of absorption edges. In this study the optical constants of La and Tb are determined in a wide energy interval 14-400 eV. The study is performed by our recent method, which is suitable for reactive materials and for intervals around the absorption edges of elements. The samples are identically protected films with thickness ~ 10 nm or ~ 100 nm, which are deposited on silicon photodiodes. Mathematical treatment separates the contributions of a capping layer and a rare-earth metal and provides data which are free from the effects of air contamination. The precision and behavior of optical constants, as well as the parameters of the O2,3 and N4,5 edges in La and Tb are analyzed.
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