Journal of X-Ray Science and Technology - Volume 6, issue 2
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Journal of X-Ray Science and Technology is an international journal designed for the diverse community (biomedical, industrial and academic) of users and developers of novel x-ray imaging techniques. The purpose of the journal is to provide clear and full coverage of new developments and applications in the field.
Areas such as x-ray microlithography, x-ray astronomy and medical x-ray imaging as well as new technologies arising from fields traditionally considered unrelated to x rays (semiconductor processing, accelerator technology, ionizing and non-ionizing medical diagnostic and therapeutic modalities, etc.) present opportunities for research that can meet new challenges as they arise.
Abstract: The strong demand for bright, compact, and inexpensive sources for x-ray microscopy has stimulated the development of flash x-ray sources. In this paper, the requirements for such a source are analyzed under boundary conditions given by the concept of an imaging x-ray microscope using mirror condenser and Fresnel zone plates for high-resolution imaging. It is found that the Lyman-α (1s–2p) line of hydrogen-like nitrogen (N VII) at λ = 2.48 nm emitted from a nonequilibrium plasma of about 200 eV temperature and 1020 cm−3 electron density is best suited. These conditions are achieved in medium-current pinch-plasma devices. Using…detailed numerical simulation of the physical processes of such a device, optimization criteria for the integrated spectral brightness (ISB) are found. Measurements of the ISB confirm these optimization criteria. The results show that the spectral emission characteristics of an optimized pinch plasma souce are compatible with the demands of the mentioned x-ray microscopy concept. These emission characteristics are compared with laser-produced plasma sources. Using the optimized source with an ISB exceeding 0.6 μJ/(μm2 sr) in a 10–20 ns pulse, wet biological samples are imaged with about 0.1 μm lateral resolution.
Abstract: Structural, phase, and chemical stabilities of x-ray multilayer mirrors Mo–(B + C) with periods in the range 8–11.5 nm were studied at temperatures of 250–1100°C by small-angle and large-angle x-ray diffraction and electron microscopy methods. Two amorphizations at ~450 and ~750°C and two crystallizations at ~650 and ~850°C of Mo-based layers were observed, which were due to the formation of the molybdenum carbides MoC (hex), γ-MoC, and Mo2 C instead of the metal Mo, and to the formation of the molybdenum borides MoB2 and Mo2 B5 instead of molybdenum carbides, respectively. Both amorphizations of Mo-based layers were accompanied…by smoothing of interfaces and by an increase of the multilayer x-ray reflectivity at λ = 0.154 nm. Both crystallizations of Mo-based layers promoted the development of interface roughness and a decrease of multilayer x-ray reflectivity. The destruction of Mo–(B + C) multilayers at ~ 1100°C was caused by the recrystallization of Mo2 B5 layers.
Abstract: The problem of multilayer mirrors which are capable of reflecting x-ray radiation at two given wavelengths is discussed. Three kinds of two-period multilayers are considered and a comparison of their properties in the soft x-ray region is presented. The scheme of a soft x-ray scanning microscope based on a Schwarzschild objective with a two-period multilayer coating is proposed for chemical microanalysis of biological samples.
Abstract: The fabrication of the calibration source is a critical part for the non-destructive and quantitative investigation of blue and white porcelains using EDXRF. In order to minimize the effects on the results due to the matrix difference between the samples and the calibration source, broken porcelain pieces of the Ming and Qing dynasties with matrix conditions similar to those of the measured samples are used directly as calibration sources. The 13 trace elements, viz. Ti, Mn, Fe, Co, Ni, Cu, Zn, Ga, Pb, Rb, Sr, Y, and Zr, have been quantitatively measured for 20 imperial blue and white porcelains of…the Qing dynasty and for 11 contemporary Jingdezhen porcelains. The data are then analyzed by the principal component analysis method. The clustering of the data and the identification of the porcelains are then investigated.
Abstract: High-temperature laser target implosions can be achieved by using relatively thin-shell targets, and they can be diagnosed by doping the fuel with krypton and measuring K-shell and L-shell lines. Electron temperatures of up to 5 keV at modest compressed densities (~ 1–5 g/cm3 ) are predicted for such experiments, with ion temperatures peaking above 10 keV at the center. It is found that the profiles of low-opacity (optically thin) lines in the expected density range are dominated by the Doppler broadening and can provide a measurement of the ion temperature if spectrometers of spectral resolution Δλ/λ ≥ 1000 are used.…For high-opacity lines, obtained with a higher krypton fill pressure, the measurement of the escape factor can yield the ρR of the compressed fuel. At higher densities, Stark broadening of low-opacity lines becomes important and can provide a density measurement, whereas lines of higher opacity can be used to estimate the extent of mixing.
Abstract: The goal of this study is to develop high resolution imaging detectors with applications in digital radiography and computed tomography. A physical treatment aimed at a better understanding of the line-spread function response of kinestatic charge detector (KCD) gas media, using dopants with permanent electric dipoles, is presented. Experimental results were obtained by operating a KCD krypton-filled detector at pressures up to 60 atm and constant electric field-to-gas density ratio doped with small amounts of polar or nonpolar polyatomic molecules with low or high ionization potential. The results clearly indicate that the addition of dopants having both low ionization potential…and high dipole moment significantly enhance the imaging signal quality. An analysis of the experimental results aimed at providing a plausible interpretation of the reported observations is offered.
Abstract: Actual assessment of the modulation transfer function (MTF) of a physical system requires objective experimental data to be obtained. This paper presents four practical methods for measuring the MTF of a linear x-ray detector. These methods are based on using the ball, wire, edge, and bar/space pattern as stimuli. The measurement procedure and experimental conditions are described in detail. The MTF results obtained with these different techniques are analyzed and compared.