Multilayer X-ray Mirrors Research Articles

Data quality in laboratory convergent-beam X-ray total scattering

Measurement of laboratory atomic pair distribution function data has improved with contemporary X-ray sources, optics and detectors, with acquisition times of the order of minutes for ideal samples. This paper examines resolution effects in pair distribution function data obtained using a convergent-beam configuration and an Ag X-ray tube from standard silicon powder and from 10 nm BaTiO3 nanocubes. The elliptical multilayer X-ray mirror reflects a non-trivial X-ray spectrum and introduces resolution effects not commonly treated in ordinary parafocusing divergent-beam laboratory diffraction. These resolution effects are modeled using the fundamental parameters approach, and the influence this has on interpretation and modeling of the resulting reduced atomic pair distribution function data is demonstrated.

Evaluation of an x-ray multilayer mirror for radiography at sub-1-keV photon energies.

An x-ray multilayer mirror on a spherical substrate designed for near-normal incidence with a photon energy of ∼738eV (F Heα) was procured and tested. This device is intended to be used for in-flight radiography of the shell in inertial confinement fusion experiments with cryogenic targets on the OMEGA laser at the Laboratory for Laser Energetics. Experiments in self-emission on a small (∼10J) laser system showed that the reflectivity of the mirror is high enough to record an image at laser energies as low as 0.1J. A second set of tests in backlighting geometry on a larger (kJ)-scale, short-pulse laser yielded usable radiographs with laser energies as low as 40J with a spatial resolution of ∼10μm.

Emission of quasi-monochromatic ultrasoft X-ray of multilayer target in the Bragg direction under 5.7 MeV electron irradiation

Previously, it was experimentally shown that VUV radiation generated in a periodic structure of a multilayer X-ray mirror by relativistic electrons exhibits a quasi-monochromatic spectrum depending on the angle of inclination of the target and the direction of emission of radiation inside the radiation cone. Here, we present new experimental results regarding the properties of angular density of radiation. A comparison between the measured radiation intensity over a wide range of target inclination angles and theoretical calculations is provided.

Multistrip multilayer mirrors for sources based on inverse Compton scattering

A technique has been developed for calculating the periods of multi-strip multilayer mirrors for effective use with sources based on the inverse Compton effect. A model for constructing the multi-strip mirror is presented. The model has been developed in accordance with modern capabilities for creating multilayer X-ray mirrors. The reflection coefficients and fractions of the energy emitted by the source that are reflected are compared for total external reflection, for multilayer Goebel mirrors and for multi-strip mirrors. It is shown that the multi-strip design of multilayer mirrors proposed in the work is almost an order of magnitude superior to Goebel mirrors and to mirrors based on the total external reflection effect in terms of the efficiency of use of the source energy.

EUV Radiation in the Range of 10–20 nm from Liquid Spray Targets Containing O, Cl, Br and I Atoms under Pulsed Laser Excitation

The article describes the results of an investigation to determine the values of radiation intensities emitted by O-, Cl-, Br-, and I-containing liquid spray targets in absolute units in the wavelength range 10–20 nm when excited by pulsed laser radiation. The conversion coefficients of laser radiation into the EUV radiation are given for some wavelengths. The authors’ specially designed pulse extrusion liquid supply system was used to form the liquid spray targets. An Nd:YAG laser with λ = 1064 nm, τ = 8.4 ns, and Epulse = 0.8 J was used to excite the targets. Spectral measurements were made using a grazing incidence grating spectrometer–monochromator. The absolute intensities of a number of emission lines were also measured using a Bragg spectrometer based on a Mo/Be multilayer X-ray mirror, calibrated by both sensitivity and wavelength. The high values of absolute intensities of the liquid targets in the extreme ultraviolet wavelength range were demonstrated.

Spectrum of coherent VUV radiation generated by 5.7 MeV electrons in a multilayer X-ray mirror

The spectral and angular properties of diffracted transition radiation (DTR) and parametric radiation (PXR) in the ultrasoft X-ray region generated by the periodic structure upon interaction with a relativistic electron beam with energy of 5.7 MeV are numerically studied using a sample of the periodic structure [Mo/Si]50, known as a multilayer X-ray mirror. Based on calculations, an experimental approach is proposed to separate and identify the contributions of PXR and DTR. The ultrasoft X-ray radiation can be used to eliminate coherent effects occurring in the optical range when diagnosing the submicron electron beam size.

Investigation of structural and reflective characteristics of short-period Mo/B4C multilayer X-ray mirrors.

The results of a study of the structural and reflective characteristics of short-period multilayer X-ray mirrors based on Mo/B4C at wavelengths 1.54 Å, 9.89 Å and 17.59 Å are presented. The period of the samples varied in the range 8-35 Å. The average widths of the interfaces were ∼3.5 and 2.2 Å at one and the other boundaries, with a tendency for weak growth with any decrease in the period. The interlayer roughness was ∼1 Å. The research results indicate promising prospects for the use of multilayer Mo/B4C mirrors for synchrotron applications.

Study of the Effect of Si and Be Barrier Layers on Crystallization of Cr/Sc Multilayer X-ray Mirror

Study of the Effect of Si and Be Barrier Layers on Crystallization of Cr/Sc Multilayer X-ray Mirror

EFFECT OF ARGON WORKING GAS PRESSURE ON MECHANICAL STRESSES IN Mo/Si MULTILAYER X-RAY MIRRORS

By the method of X-ray tensometry (=0.154 nm), the dependences of residual stresses in Mo/Si multilayer Xray mirrors (MXMs) obtained by direct-current magnetron sputtering were studied as a function of the sputtering Ar pressure in the range of 1…4 mTorr. It is shown that an increase in pressure is accompanied by an increase in stresses from ~ 0.4 to ~ 0.8 GPa for a group of mirrors with periods near 7 nm and from ~ 0.9 to ~ 1.6 GPa for a group of mirrors with periods near 14 nm. The angles of texture misorientation for Mo crystallites were measured as a function of argon pressure. Mechanisms have been proposed to explain the reasons for the increase in stresses.

A Multilayer Nested Space Ray Telescope Assembly and Adjustment System Based on Online Monitoring Feedback

In order to adapt to the rapid development of deep space exploration, pulsar navigation and space astronomical observation technology, the development of high-efficiency and high-performance X-ray space telescopes has become one of the hotspots for research in the fields of autonomous spacecraft navigation and astronomical observation. Since the X-ray multilayer nested mirror shells are thin-walled and deformable cylindrical structures with high requirements for surface shape accuracy, a slight change in the position or surface shape will lead to a reduction in the focusing imaging quality, so it is necessary to develop a high-precision assembly and adjustment system based on closed-loop real-time monitoring. In this paper, a multi-layer nested space ray telescope assembly and adjustment system with online monitoring feedback is developed, and a method for precision assembly and adjustment of multi-layer nested mirror shells based on online real-time detection and feedback is proposed, which specifically includes key innovative assembly technologies such as three-dimensional face shape measurement, flexible vacuum adsorption, precision adjustment that have been broken through in the process, and the imaging quality of the focused spot of the mirror shells is evaluated and analyzed in the end. The results of the experiment indicate that the assembly and adjustment of the multilayer nested mirror shells can effectively complete the high-precision assembly, and the relevant results can provide a certain reference significance for the further enhancement of the assembly and adjustment performance of the multilayer nested mirror shells.

A modular table-top setup for ultrafast x-ray diffraction.

We present a table-top setup for femtosecond time-resolved x-ray diffraction based on a Cu Kα (8.05keV) laser driven plasma x-ray source. Due to its modular design, it provides high accessibility to its individual components (e.g., x-ray optics and sample environment). The Kα-yield of the source is optimized using a pre-pulse scheme. A magnifying multilayer x-ray mirror with Montel-Helios geometry is used to collect the emitted radiation, resulting in a quasi-collimated flux of more than 105 Cu Kα photons/pulse impinging on the sample under investigation at a repetition rate of 10Hz. A gas ionization chamber detector is placed right after the x-ray mirror and used for the normalization of the diffraction signals, enabling the measurement of relative signal changes of less than 1% even at the given low repetition rate. Time-resolved diffraction experiments on laser-excited epitaxial Bi films serve as an example to demonstrate the capabilities of the setup. The setup can also be used for Debye-Scherrer type measurements on poly-crystalline samples.

Monte Carlo study of X-ray grazing incidence microscopy using Geant4.

X-ray grazing incidence microscopy has extensive applications in the fields of laser inertial confinement fusion and synchrotron radiation. Monte Carlo methods can be used to determine the optical performance of X-ray grazing incidence microscopes and predict the experimental results, which is of great significance for studying physical experiments and diagnostics. In this paper, we proposed a Monte Carlo method based on Geant4 for studying X-ray grazing incidence microscopy. We introduced the G4MultilayerReflection class to describe the physical processes of X-ray multilayer mirrors. We designed a dual-energy Kirkpatrick-Baez microscope that can operate at 6.4 and 9.67 keV simultaneously. Monte Carlo simulations of the spatial resolution and throughput efficiency of the microscope were performed using Geant4, which was assembled and characterized. The spatial resolution results obtained by the Geant4 laboratory simulations, the theoretical model, and the experiments were in good agreement. Additionally, we conducted throughput efficiency calibration experiments for the 6.4 keV imaging channel. The difference between the experimental and Geant4-simulated throughput efficiency was evaluated and resulted in root mean square error values of 8.7% and 9.5% along the Y- and Z-axes, respectively.

Исследование свойств многослойных зеркал на основе пары материалов Mo/B-=SUB=-4-=/SUB=-C

The properties of Mo/B4C multilayer X-ray mirrors with periods of 3.74 – 3.84 nm are studied in this work. The dependences of the transmission band, reflection coefficient and the magnitude of internal stresses in mirrors on the ratio of material thicknesses in the period were investigated. The results of a study of the effect of thermal annealing on the structural parameters and reflective characteristics of mirrors are also presented in the paper.

Эмиссионные характеристики лазерно-плазменного источника экстремального ультрафиолетового излучения с тонкопленочными мишенями

The radiation spectra in the soft X-ray and extreme ultraviolet wavelength ranges of thin-film (0.15 microns thick) targets made of light materials (Si, C, Be) were studied when excited by a Nd:YAG laser pulse with a duration of 5.2 ns focused to an intensity of ~10^12 W/cm^2. Line spectra of BeIII, BeIV, CV, and SiV ions were recorded using a spectrometer based on a multilayer X-ray mirror. A comparison with the spectra of bulk solid-state targets of the same materials is carried out. In all cases, there was a decrease in the intensity of the lines of the soft X-ray spectrum of film targets compared to monolithic ones; the decrease was, depending on the material, from several tens of percent to several times, with more than an order of magnitude less mass of the vaporized substance.

One-dimensional image scaling with a reflecting X-ray mask

The work deals with the issue of miniaturization of template images using X-ray radiation. The compression method is based on the fact that X-ray radiation is directed at a specific template that reflects X-ray radiation at an grazing angle and a one-dimensional compressed image is recorded on a plane not parallel to the plane of the template. The advantage of this method of image compression is the relative simplicity of its implementation. The paper proposes the use of X-ray multilayer mirrors as reflective X-ray masks (RXM) for one-dimensional image compression. Control of the structural parameters of multilayer mirrors was carried out on a DRON- 3M X-ray diffractometer. The RXM template was formed by sputtering an absorbing WC layer with a thickness of ~0.2 μm through a certain stencil on the surface of a multilayer mirror. The test of the RXM with mirrors based on a pair of WC/Si materials in synchrotron radiation (l~3.5 nm) was carried out. A 14-fold compression of the reflective segments of the RXM with a size of ~50 μm was obtained. Theoretically, the principle possibility of obtaining compression of reflective segments to submicron sizes is shown.

Research and creation of broadband X-ray mirrors with a spectral transmission band coinciding with emission lines and the possibility of filtering

The article considers broadband multilayer X-ray mirrors based on Mo/Be and Mo/Si structures with a transmission band coinciding with the Si Lα (13.5 nm) and Sn (13.5 nm) emission lines. The described structures are of great interest for the currently developed liquid source of EUV radiation, since they make it possible to increase the efficiency of the source-X-ray optical system due to the "complete" capture of emission lines. Keywords: extreme ultraviolet radiation, emission spectrum, laser spark, multilayer X-ray mirror.

Prospective wavelengths for projection lithography uing synchrotron radiation

Promising wavelengths for next-generation lithography with a wavelength shorter than 13.5 nm based on a synchrotron X-ray source are discussed. Theoretical and experimental values of the reflection coefficients of multilayer X-ray mirrors providing the maximum reflectivity in the range of 11.4-3.1 nm are presented. The theoretical efficiency of multilayer optics is compared for different wavelengths. Keywords: X-ray lithography, multilayer X-ray optics, multilayer X-ray mirrors.

Система визуализации плазменного факела бетатронного источника рентгеновского излучения

The paper describes the design of a microscope for studying a betatron radiation source based on the PEARL femtosecond laser complex in the SXR and EUV wavelength range. The main optical element of the microscope is a spherical Schwarzschild objective a x5 magnification. The device allows to study the size and spatial structure of the interaction area of laser radiation with matter, at a selected wavelength in the EUV or SXR range with a resolution of δx = 2.75 microns. The operation wavelength (=13.5 nm) is set by multilayer X-ray mirrors. Thin-film absorption filters are used to suppress the background component of the signal.

Ru/Sr multilayer mirrors for the spectral range 9-12 nm

The results of studies of Ru/Sr multilayer mirrors optimized for the working wavelength range of 9-12 nm are presented in the paper. Within the framework of the presented article the strontium based multilayer structures with stable over time reflective characteristics were obtained for the first time. It is shown that Ru/Sr mirrors have the highest reflectance of all known reflective coatings, with the exception of beryllium-containing, in the spectral range of 9-12 nm. Keywords: multilayer X-ray mirrors, X-ray lithography, X-ray radiation.

Imaging system of a plasma torch of a Betatron X-ray source

The paper describes the design of a microscope for studying a betatron radiation source based on the PEARL femtosecond laser complex in the SXR and EUV wavelength range. The main optical element of the microscope is a spherical Schwarzschild objective a x5 magnification. The device allows to study the size and spatial structure of the interaction area of laser radiation with matter, at a selected wavelength in the EUV or SXR range with a resolution of delta x=2.75 μm. The operation wavelength (λ=13.5 nm) is set by multilayer X-ray mirrors. Thin-film absorption filters are used to suppress the background component of the signal. Keywords: SXR and EUV radiation, betatron radiation, imaging x-ray optics, SXR microscope.