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.

Some variants of the composition of multilayer absorption film filters with a high transmittance in the spectral region of the "water window" (2.3-4.4 nm) have been considered. Having created an ultimate pressure difference between the sides of free-standing films at which they are damaged, we compared the strength of 100 nm thick Ti-based multilayer filters with Al, Be, C interlayers and 100 nm thick V-based multilayer filters with Al interlayers. Sc and Cr was also considered as interlayers. Among the tested periodic multilayer structures, the best strength characteristics were demonstrated by Ti/Be (with a fraction of Ti in a period of about 0.6) and V/Al (with a fraction of V in a period of about 0.4) multilayer filters. Despite the fact that Ti/Be and V/Al filters are inferior in strength to Ti and V monolayer filters of the same thickness, these multilayer filters may be of interest, since they have either a higher transmittance in the "water window" (Ti/Be) or more high level of blocking of visible radiation (V/Al). Keywords: spectral region of the "water window" multilayer free-standing filters, ultimate pressure difference, film filter strength, transmittance in the soft x-ray, visible light blocking level.

Multilayer interference structures acting as dispersion elements for a mirror spectrometer for a wavelength range of 7–30 nm have been calculated and synthesized. Three elements are implemented: for the range λ = 7–12 nm – multilayer structure Mo/B4C (number of periods N = 60, period thickness d = 6.5 nm); for the range λ = 11–18 nm – Mo/Be (N = 50; d = 9.83 nm) and for the range λ = 17–30 nm – Be/Si/Al (N = 40; d = 18.2 nm). For the entire spectral range, an efficiency of more than 10

Within the Universat program, a set of solar vacuum ultraviolet (VUV) telescopes has been developed for deployment on 6U nanosatellites. Telescopes are designed to get images of the solar corona. The spectral ranges of observations is considered, the characteristics of the nanosatellite from the point of view of the observations feasibility are opmized, the optical scheme of the telescope and VUV multilayer mirrors coatings and thin-film filters are modelled. Keywords: Nanosatellite, VUV, telescope, solar corona.

Using a multilayer mirror spectrometer of the extreme ultraviolet (EUV) range, the laser plasma emission spectra of bulk aluminum in the wavelength range of 8.0-18.0 nm were studied. Testing of thin film laser targets made of aluminum and comparative measurements of the intensity of EUV radiation of a film with a thickness of 100 nm and a bulk material target were carried out. Keywords: SXR and EUV radiation, thin film, laser plasma.

Knowledge of the emissivity and thermal conductivity of thin metal films used in conjunction with multilayer mirrors for the spectral selection of radiation in the extreme-ultraviolet- and “soft”-X-ray wavelength ranges is necessary in order to correctly calculate the heating of film elements at high heat loads. Heating is associated with absorption in the film of a significant fraction of the incident intensity, and the concept of a high heat load is somewhat arbitrary, since even at an absorbed intensity level on the order of 1 W/cm 2 a freestanding film can be heated in vacuum by several hundred degrees. In the first approximation, to estimate the thermal-conductivity coefficient, one could use tabular values for bulk samples of the corresponding metals or use the well-known Wiedemann-Franz law which links the thermal conductivity and the electrical resistivity of the sample; the latter is easier to measure. However, an analysis of the published data indicates significant errors that are possible when using any of these approaches. Therefore, in this work, we measure the thermal conductivity directly by processing the temperature distribution obtained by infrared (IR) pyrometry over a film sample mounted on a heated frame or heated by a flowing electric current. The thermophysical characteristics (thermal conductivity and emissivity) are determined for samples of film absorption filters based on Mo, Al, and Be of submicron thickness (from 100 nm), as well as for films of copper: a metal whose bulk samples have high thermal and electrical conductivity. As expected, significant differences are found between the thermal and electrical properties of the film materials and the properties of the same metals in monolithic samples.

Variants of the structures of free-standing films with a high transmittance coefficient at a wavelength of 13.5 nm, which were developed for use in the projection of extreme ultraviolet (EUV) lithography as protective and filtering elements, are considered. Our attention is focused on the most problematic—in terms of manufacturing and the requirements on their characteristics—ultrathin free-standing films (pellicles), which are installed in front of the mask (photomask) in modern EUV scanners and serve to protect the surface of the mask from contamination. The main approaches used to manufacture ultrathin free-standing large-aperture films are compared. A brief review of the research on the development of high transmittance pellicles at a wavelength of 11.2 nm, which may become an operating wavelength for future EUV lithography, is given.

We demonstrate the possibility of manufacturing Be-basedultrathin films with high transmission at wavelengths of 11.4 and 13.5 nm. For free-standing films of Be and Be-based multilayer structures (Si/Be,ZrSi2/Be, Be/BexNy, Zr/Be, Ru/Be, Mo/Be), we determine the thresholds of theabsorbed power at which over a short period (tens of minutes) of vacuumannealing, initially sagging free-standing films became visibly stretchedover the hole. Of the film structures tested here, the Be/BexNy structure(with beryllium nitride interlayers) showed the highest threshold for theabsorbed power (1 W/cm2). However, due to the low strength of thisstructure, ZrSi2/Be, Mo/Be, and Be films seem to be more promising for themanufacture of a full-size pellicle. Long-term vacuum annealing of Mo/Beand Be ultrathin films showed that they could withstand 24 hours of vacuumheating at an absorbed power density of 0.2 W/cm2 (film temperature 250oC)without noticeable changes in EUV transmission or sagging of films. Withcomparable transmission (~83% at 13.5 nm and ~88% at 11.4 nm), a multilayerMo/Be structure with a thickness of 30 nm appears to be preferable, as itshows less brittleness than a monolayer Be film with a thickness of 50 nm. Keywords: Be-based pellicle, multilayer thin film, EUV lithography,thermal stability\

We describe results of studying emission spectra of Cl-, Br-, and I-containing liquid jet targets in the 3‒6.5 nm wavelength range under their excitation by a pulsed laser. A number of emission lines of Cl, Br, and I ions are recorded, including in the “water-window” spectral range of 2.3‒4.4 nm. A specially developed system based on an industrial pulse valve is used for a liquid-jet target to be formed. The targets are excited by an Nd:YAG laser (λ = 1064 nm, τ = 5.2 ns, E pulse = 0.8 J). Using a Bragg spectrometer based on a multilayer X-ray Cr/Sc mirror and Ti/Be absorption filters, absolute intensities of some of the most intense lines are measured. High emissivity of liquid targets is demonstrated; thus, for a bromine-containing target in the 6.12 ± 0.05 nm band, the resulting radiation intensity in the half-space is 1.3 × 10 13 photons per pulse.

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.

Observation of a sample of Si/Al/Sc mirror with a MoSi2 protective cap layer, which was stored in air for 40 months, showed that the peak reflectivity at a wavelength of 58.4 nm during this period decreased from 32 % to 20.5 %, and over the last 20 months of observation-from 21.5 % to 20.5 %, which indicates a significant decrease in the rate of decline and almost stabilization of the peak reflectivity at the level of 20 %. The spectral reflection peak width of this mirror at half maximum has not changed over the past 20 months and amounted to 6.3 nm. The given data of secondary ion mass spectrometry and grazing incidence X-ray reflectometry show that the decrease in reflectance of Si/Al/Sc multilayer mirrors with a MoSi2 protective cap layer is mainly due to an increase in the amount of impurities (oxygen and carbon) in the structure and on the surface of the mirrors and, to a lesser extent, due to the broadening of the interlayer boundaries. Comparison of the rate of decrease in reflectance at 58.4 nm of Sc/Al mirrors with interlayers of silicon and nitride scandium and a MoSi2 cap layer indicates that neither the material and thickness of the interlayer nor the thickness of the protective MoSi2 cap layer within 3-6 nm have a significant effect on this rate.

Multilayer interference structures acting as dispersion elements for a mirror spectrometer for a wavelength range of 7-30 nm have been calculated and synthesized. Three elements are implemented: for the range λ=7-12 nm – multilayer structure Mo/B4C (periods N=60; period thickness d=6.50 nm); for the range λ=11-18 nm – Mo/Be (N=50; d=9.83 nm) and for the range λ=17-30 nm – Be/Si/Al (N=40; d=18.2 nm). For the entire spectral range, an efficiency of more than 10% was obtained at a wavelength resolution of 0.15-1.0 nm.

Variants of the structures of freely hanging films with a high transmittance coefficient at a wave-length of 13.5 nm, which were developed for use in the projection of extreme ultraviolet (EUV) lithography as protective and filtering elements, are considered. Our attention is focused on the most problematic—in terms of manufacturing and the requirements on their characteristics—ultrathin freely hanging films (pelli-cles), which are installed in front of the mask (photomask) in modern EUV scanners and serve to protect the sur-face of the mask from contamination. The main approaches used to manufacture ultrathin freely hanging large-aperture films are compared. A brief review of the research on the development of high transmittance pellicles at a wavelength of 11.2 nm, which may become an operating wavelength for future EUV lithography, is given.

This paper describes in detail a compact (2U format) telescope operating in the extreme ultraviolet range for studying the solar corona at a wavelength of 17.14 nm. The telescope objective has been built according to the Ritchey-Chrétien scheme with the following parameters: effective focal length of 381.3 mm, field of view of 2×2∘, and angular resolution of 11 in. Reflective multilayer Al/Be coatings were used, having 55% reflectance and a 0.4 nm spectral bandwidth. The wavefront rms error is 30 nm. An interferometric technique for controlling the shapes of the substrates and for adjusting the optical system and detector of the telescope assembly is described in detail.

The paper presents experimental data on the absolute values of the radiation intensity in the wavelength range of 6.6-32 nm for a stainless steel target excited by a Nd: YAG laser with parameters λ=1064 nm, Epulse=0.45 J, tau=4 ns, ν=10 Hz. The results are of interest for various applications using laboratory laser-plasma sources of soft X-ray and extreme ultraviolet radiation. Keywords: extreme ultraviolet radiation, emission spectrum, laser spark, multilayer X-ray mirror.

Some variants of the composition of multilayer absorption film filters with a high transmittance in the spectral region of the “water window” (2.3–4.4 nm) have been considered. Having created an ultimate pressure difference between the sides of free-standing films at which they are damaged, we compared the strength of 100 nm thick Ti-based multilayer filters with Al, Be, C interlayers and 100 nm thick V-based multilayer filters with Al interlayers. Sc and Cr was also considered as interlayers. Among the tested periodic multilayer structures, the best strength characteristics were demonstrated by Ti/Be (with a fraction of Ti in a period of about 0.6) and V/Al (with a fraction of V in a period of about 0.4) multilayer filters. Despite the fact that Ti/Be and V/Al filters are inferior in strength to Ti and V monolayer filters of the same thickness, these multilayer filters may be of interest, since they have either a higher transmittance in the “water window” (Ti/Be) or more high level of blocking of visible radiation (V/Al).

The article is devoted to the development of an EUV microscope using a wavelength of 13.84 nm. Due to the use of a mirror lens with a large numerical aperture, NA = 0.27, and a short depth of focus, it has been possible to carry out z-tomography of bio-samples for the first time with this type of microscope. A 3D image was reconstructed, and a pixel resolution of 140 nm was obtained. A new simple algorithm for the 3D reconstruction of absorption images from z-tomography data has been proposed that takes into account lens aberrations and a point spread function. The algorithm reduces the inverse absorption task to the corresponding well-studied task of fluorescence microscopy, with an error of 10% for cells up to 10 µm thick.

We demonstrate the possibility of manufacturing Be-based ultrathin films with high transmission at wavelengths of 11.4 and 13.5 nm. For free-standing films of Be and Be-based multilayer structures (Si/Be, ZrSi2/Be, Be/BexNy, Zr/Be, Ru/Be, Mo/Be), we determine the thresholds of the absorbed power at which over a short period (tens of minutes) of vacuum annealing, initially sagging free-standing films became visibly stretched over the hole. Of the film structures tested here, the Be/BexNy structure (with beryllium nitride interlayers) showed the highest threshold for the absorbed power (1 W/cm2). However, due to the low strength of this structure, ZrSi2/Be, Mo/Be, and Be films seem to be more promising for the manufacture of a full-size pellicle. Long-term vacuum annealing of Mo/Be and Be ultrathin films showed that they could withstand 24 hours of vacuum heating at an absorbed power density of 0.2 W/cm2 (film temperature ~250°C) without noticeable changes in EUV transmission or sagging of films. With comparable transmission (~83% at 13.5 nm and ~88% at 11.4 nm), a multilayer Mo/Be structure with a thickness of 30 nm appears to be preferable, as it shows less brittleness than a monolayer Be film with a thickness of 50 nm.

Using a multilayer mirror spectrometer of the extreme ultraviolet (EUV) range, the laser plasma emission spectra of bulk aluminum in the wavelength range of 8.0-18.0 nm were studied. Testing of thin film laser targets made of aluminum and comparative measurements of the intensity of EUV radiation of a film with a thickness of 100 nm and a bulk material target were carried out.

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.