A. Erko

High-performance x-ray spectroscopic devices for plasma microsources investigations

X-ray spectroscopy with high spectral (up to Δλ/λ = 10−4) and spatial resolution (up to 1 μm) is discussed. Devices based on crystals, diffraction and Bragg-Fresnel elements and their applications in Z- and X-pinches and laser plasma experiments are described.

Multilayer gratings efficiency: numerical and physical experiments

Abstract Recently the possibility of focusing, imaging and spectroscopy with Fresnel zones etched on a flat multilayer substrate instead of a curved substrate has been shown. This is now known as Bragg-Fresnel Multilayer lenses (BFML). Lamellar gratings etched in a multilayer (LMG) are the basic type of Bragg-Fresnel optics. In this paper we describe important points in the fabrication, computer simulation, and testing of the LMs. They can be very interesting as a spectroscopic device with a relatively high dispersion and efficiency. We develop a rigorous theory of diffraction combined with the layer-by-layer differential integration numerical method. The agreement with experimentals results obtained for a lamellar grating with several period and various etched depths in a W/Si multilayer is very good. The main result is an increase of the effective extinction depth ( t ext ) in short-period gratings which gives a possibility to increase the absolute diffraction efficiency of the LGM practically from 30% to 60% in the first order with a totally suppressed zero order.

Elliptical multilayer Bragg-Fresnel lenses with submicron spatial resolution for X-rays

Abstract Elliptical Bragg-Fresnel multilayer lenses (BFML), designed and fabricated at the Institute of Microelectronic Technology (Russian Academy of Science) have been used for two-dimensional focusing of the white X-ray synchrotron beam at LURE (Orsay France). For two fixed beam energies (8 keV and 12.4 keV), the spot size produced was approximately 1 μm as determined from a high resolution photographic plate. A fluorescence X-ray scanning microprobe based on these BFML lenses was also tested. The transmitted signal registered during the scan of a test object shows less than 1 μm resolution with 8 keV output photon energy. 2D scanning images with submicron resolution of test objects in transmission mode at 8 keV and 12.4 keV beam energies are presented.

Comparison of modal and differential methods for multilayer gratings

Abstract Modal theory is applied in calculating the lamellar multilayer grating performances. Comparison of numerical results obtained with the differential and modal methods is performed. Both methods give the same values of diffraction order efficiency and are in good agreement with experimental data. Tungsten-carbon multilayer gratings having a 4 μm lamellar period and a 3 nm bilayer spacing for a 0.154 nm wavelength were used as the test object. The diffraction properties of multilayer gratings are discussed using reciprocal space and dispersive surfaces representation. A strong dependence of the multilayer grating properties on the lamellar period and the optical characteristics of multilayer grating materials are shown.

First test of the scanning X-ray microprobe with Bragg-Fresnel multilayer lens at ESRF beam line

Abstract The fluorescence X-ray scanning 2D microprobe based on a Bragg-Fresnel multilayer lens (BFML) has been tested at the ESRF, Grenoble (France) for the first time. A single elliptical BFML has been used for two-dimensional focusing of the X-ray synchrotron beam of an undulator source in the energy range of 12 keV. A spatial resolution of 2.4 μm and a photon intensity of about 10 10 photons per second have been measured using a Cr knife-edge test object.

Dynamical theory for Bragg Fresnel multilayer lenses for X-UV and X-ray range

Abstract We propose a general dynamical theory for Bragg Fresnel multilayer lenses (BFML) which allows writing fast and accurate numerical codes. Our theory is valid if one satisfies a given inequality relation between the lens parameters. We apply this theory to a particular kind of BFML which has been designed recently for zero order suppression around the first focused order. Numerical simulations results are compared to experimental data.

Fabrication, structure and reflectivity of WC and WB4C multilayers for hard X-ray

Abstract The W C and W B 4 C multilayer structures (MLS) with the period d = 29–35 A were fabricated by RF-magnetron sputtering under different conditions. Structure and properties of the MLS were studied, using transmission electron microscopy (TEM) and small-angle X-ray (1.54 A) scattering techniques. The results of the research show that amorphous tungsten layers (6–12 A) in both W C and W B 4 C multilayer systems always have an islanding structure, and that the type of the islands depends strongly on the magnetron power and on the thickness of the layers. It is shown that shape and dimensions of the island have important influence to the mirrors reflectivity. A narrowing of the rocking curve for the first Bragg peak was observed in some multilayers into which intermediate layers of the light material (spacer) were introduced. The TEM study revealed modified internal structure of these multilayers and a different capability of C and B4C to form a thin film with smooth outer surface. As a result of the work, the optical quality of the MLS in hard X-ray was improved.

Microplasma object imaging spectroscopy by using zone plate surface structure on mica crystal

A new method is proposed for obtaining spatially resolved multicharged ion spectra of microplasma sources with resolution better than 0.5 μm. The method is based on making a Bragg–Fresnel lens structure on a mica crystal surface. The lens was formed in a direction normal to the direction of dispersion and was used for the investigation of plasma created in nanosecond X pinch. The method may be used in studies of plasma heated by pico‐ and femtosecond laser radiation.

High-performance x-ray spectroscopy of plasma microsources

X-ray spectroscopy with high spectral (up to (Delta) (lambda) /(lambda) equals 10-4) and spatial resolution (up to microns) is discussed. Devices based on crystals, diffraction, and Bragg-Fresnel elements and their application in Z- and X-pinches and laser plasma experiments are observed.

Imaging X‐ray Spectroscopy in Z‐Pinch Experiments

X‐ray spectroscopy with high spectral (up to Δλ/λu2009=u200910−4) and spatial resolution (up to microns) is discussed. Devices based on crystals, difraction and Bragg‐Fresnel elements and there application in Z‐ and X‐pinches experiments are observed.